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HPndashUHP Metamorphic Belt in the East Kunlun
Orogen Final Closure of the Proto-Tethys Ocean
and Formation of the Pan-North-China
Continent
Shuguang Song 1 Hengzhe Bi1 Shengsheng Qi2 Liming Yang1
Mark B Allen3 Yaoling Niu3 Li Su4 and Wufu Li2
1MOE Key Laboratory of Orogenic Belt and Crustal Evolution School of Earth and Space Sciences Peking
University Beijing 100871 China 2Qinghai Bureau of Geological Survey Xining 810012 China 3Department of
Earth Sciences Durham University Durham DH1 3LE UK 4Institute of Earth Science and State Key Laboratory of
Geological Processes and Mineral Resources Chinese University of Geosciences Beijing 100083 China
Corresponding author E-mail sgsongpkueducn
Received April 8 2018 Accepted September 12 2018
ABSTRACT
The East Kunlun Orogen the northwestern part of the Central China Orogenic Belt is a long-livedaccretionary orogenic belt that records the evolution and eventual destruction of branches of the
Tethys Ocean from the Cambrian to the Triassic Here we report an Early Paleozoic eclogite belt that
extends for 500 km within the East Kunlun Orogen This belt consists of eclogite blocks metasedi-
mentary rocks and minor serpentinite blocks accompanied by ophiolites (530ndash460 Ma) and concur-
rent arc volcanic sequences and granitic plutons Geochemical data show that the eclogites have
normal mid-ocean ridge basalt- to ocean island basalt-like compositions UndashPb dating of metamorph-
ic zircons from eclogites and their surrounding rocks gave peak and retrograde metamorphic ages of430ndash410 Ma Coesite pseudomorphs in garnet quartz exsolution rods in omphacite and PndashT calcula-
tions suggest that some eclogites experienced ultrahigh-pressure (UHP) metamorphic conditions at
29ndash30 kbar and 610ndash675C these could represent oceanic crust subducted to and exhumed from
coesite-forming depths (100ndash120 km) The UHP metamorphic eclogite belt in the East Kunlun Orogen
may represent the final closure of the Proto-Tethys Ocean (opening at 580 Ma subduction initiating
at 520 Ma) at 430ndash410 Ma in the East Kunlun with the formation of the Pan-North-China Continentin the Early Paleozoic and expansion of the Paleo-Tethys Ocean in the south
Key words eclogite belt ultrahigh-pressure metamorphism Proto-Tethys Ocean East KunlunOrogen
INTRODUCTION
Eclogites carry information that is critical in understand-ing orogenic processes (eg Ernst 1988 Carswell 1990
Ernst amp Liou 1995) Together with ophiolites arc mag-
matism and the sedimentary fill of accretionary prisms
eclogites characterize orogenic belts associated
with paleo-ocean subduction (eg Agard et al 2009
Song et al 2013) and provide valuable information on
the processes and conditions of subduction andexhumation
The Proto-Tethys Ocean is an inconsistently used
concept for a supposed predecessor of the Paleo-Tethys Ocean which separated some blocks (eg the
QaidamndashQilian South China) from the northern mar-
gins of Gondwana in the Neoproterozoic (eg Li et al
2008 von Raumer amp Stampfli 2008 Xu et al 2015)
The evolution of Proto-Tethys is however ambiguous
concerning the timing of its opening and closing aswell as geological processes in the course of its shrink-
ing and transition to the Paleo-Tethys Ocean
VC The Author(s) 2018 Published by Oxford University Press All rights reserved For permissions please e-mail journalspermissionsoupcom 2043
J O U R N A L O F
P E T R O L O G Y
Journal of Petrology 2018 Vol 59 No 11 2043ndash2060
doi 101093petrologyegy089
Advance Access Publication Date 20 September 2018
Original Article
Dow
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icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
The QinlingndashQilianndashKunlun orogenic belt (or the
Central China Orogenic Belt) lies in the central part of
China and is considered to have resulted from the con-
sumption of the Proto-Tethys (eg Yin amp Harrison 2000
Dong amp Santosh 2016 Song et al 2017) The EastKunlun the west part of the QinlingndashQilianndashKunlun
Mountains (Fig 1) is a long-lived orogenic belt with a
history from Cambrian to Triassic times which records
the orogenic evolution of the Proto- and Paleo-Tethys
oceans and holds the key to understanding the evolu-
tion of the ancient Tethys Ocean and formation of the
Chinese continent Eclogite blocks were reported byMeng et al (2013) and subsequently by Qi et al (2016)
at Wenquan in the east and by Qi et al (2014) at
Xiarihamu in the west of the East Kunlun Orogen (EKO)
(Fig 1) With the addition of a newly discovered
eclogite-bearing locality at Kehete in the mid-east a
500 km long eclogite-bearing high-pressure meta-morphic belt can be recognized within the EKO In this
study we present petrological geochemical and geo-
chronological studies of this eclogite belt We have
determined for the first time that some of the EKO eclo-
gites have experienced UHP metamorphism in
SilurianndashDevonian times This eclogite belt togetherwith accompanying ophiolites and arc volcanic rocks
represents the final closure of the Proto-Tethys Ocean
and continued convergence between fragments of
Eastern Gondwanaland and the North ChinandashTarim
continent
Mineral abbreviations are after Whitney amp Evans
(2010)
GEOLOGICAL SETTING AND PETROGRAPHY
The East Kunlun Orogen lies south of the Qaidam Block
(Fig 1) The basement of the Qaidam Block is largely
covered by thick sedimentary successions of a
Mesozoic to Cenozoic intracontinental basin The
Precambrian crystalline basement is mainly exposed at
the north and south margins of the block To the north
of the Qaidam Block is the North Qaidam ultrahigh-pressure metamorphic (UHPM) belt which consists of
various types of eclogite garnet peridotite coesite-
bearing metapelite and granitic gneiss The North
Qaidam UHPM belt is a continental collision zone
recording that the Qaidam Block had subducted north-
wards to depths of 200 km at 440ndash425 Ma (eg Song
et al 2014 and references therein) Further north theQilian Orogen consists of the South Qilian oceanic
accretionary belt the Central Qilian Block and the North
Qilian oceanic accretionary belt The South Qilian
oceanic accretionary belt (SQAB) is composed of
Cambrian ophiolites (535ndash500 Ma) and an Ordovician
intra-oceanic arc complex (470ndash440 Ma) (eg Songet al 2017 Zhang et al 2017) without high-pressure
rocks The North Qilian oceanic accretionary belt
(NQAB) consists of 550ndash450 Ma ophiolites 520ndash440 Ma
continental arc volcanic and plutonic rocks and 500ndash
440 Ma high-pressure metamorphic rocks Carpholite in
metapelites and lawsonite in eclogites and blueschistssuggest relatively cold oceanic subduction and high-
pressurelow-temperature (HPLT) metamorphism
(Song et al 2007 Zhang et al 2007) Therefore three
subparallel HPndashUHP belts are exposed in a 400 km wide
region in the northern Tibetan Plateau (Fig 1) These
HPndashUHP belts together with associated ophiolites and
arc rocks record the evolution of the northern Proto-Tethys Ocean from ocean-floor subduction and con-
sumption to subsequent continental collision (Song
et al 2006 2014)
The East Kunlun Orogen records a long and complex
history from Cambrian to Triassic times (Dong et al
Fig 1 Simplified geological map of the northern Tibetan Plateau showing HPndashUHP metamorphic terranes in three orogenic beltsCAOB Central Asian Orogenic Belt CCOB Central China Orogenic Belt HOB Himalayan Orogenic Belt NCC North China CratonNQ-SP North QiangtangndashSongpan Block SCC South China Craton QLB QiangtangndashLhasa Block TB Tarim Block NQAB NorthQilian Accretionary Belt SQAB South Qilian Accretionary Belt NQUB North Qaidam UHPM Belt EKO East Kunlun Orogen CQBCentral Qilian Block
2044 Journal of Petrology 2018 Vol 59 No 11
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2018 Li et al 2018) It mainly consists of (1) an Early
Paleozoic accretionary complex at the southwestern
margin of the Qaidam Block (2) the Arsquonyemaqen accre-
tionary complex in the south (3) Precambrian base-
ment (the South Kunlun Block) and (4) Triassic volcanicand plutonic rocks distributed throughout the East
Kunlun Orogen Ophiolites in the Early Paleozoic accre-
tionary complex formed over a long period from 537 to
460 Ma (Yang et al 1996 Bian et al 2004 Meng et al
2015 Qi et al 2016 Li et al 2018) the same as ophio-
lites in the QilianndashQaidam region to the north (Song
et al 2013) The types of ophiolite are not well docu-mented partly because most ophiolites are strongly
deformed and fragmented Basalts with pillow structure
show characteristics of normal- to enriched-mid-ocean
ridge basalt (N- to E-MORB) affinity (Yang et al 1996
Qi et al 2016) most probably representative of MORB-
type ophiolites (eg Topuz et al 2018) Arc volcanicrocks include Alaskan-type ultramaficndashmafic intrusions
with CundashNi ore-deposits andesitesndashrhyolites and
granites with SilurianndashDevonian ages (450ndash400 Ma) (eg
Zhu et al 2006 Wang et al 2014) Three eclogite-
bearing regions from east to west Wenquan Kehete
and Xiarihamu are distributed discontinuously along
the Early Paleozoic accretionary belt (Fig 1) TheArsquonyemaqen accretionary complex in the south is main-
ly a melange belt with 460ndash308 Ma ophiolitic fragments
(Bian et al 2004 Yang et al 2004) The Precambrian
basement in the EKO mainly consists of 1200ndash950 Ma
Mesoproterozoic granitic gneisses Detrital zircons from
metapelite (KL33) yielded an age peak at 2482 Ma with
secondary age groups of 2686ndash2505 and 2180ndash1054 Madetrital zircons from late Neoproterozoic sedimentary
rocks (Golmud region) yield a major age group of 1465ndash
802 Ma and three minor age groups of 1892ndash1758
2502ndash2431 and 3308 Ma (authorrsquos unpublished data)
All eclogites in the three terranes occur as lens-
shaped blocks of varying size (5ndash100 m in length) withinmetasedimentary hosts including metapelite and mar-
ble (Fig 2andashd) A serpentinite block has also been
Fig 2 Field photographs and photomicrographs of the eclogite belt in the EKO (a) Eclogite block within garnetndashmica schist (meta-pelite) from Kehete terrane (b) Eclogite block with weak alteration (Kehete terrane) (c) Eclogite blocks with marble (Xiarihamu ter-rane) (d) Eclogite blocks within metapelite (Xiarihamu terrane) (e) Photomicrograph of eclogite with the mineral assemblagegarnet (Grt) omphacite (Omp) phengite (Phn) rutile (Rt) and quartz (16KL13) (f) Coesite-pseudomorphs (Coe-P) in omphacite (g)Coesite-pseudomorph (Coe-P) in garnet [Note Omp rims decompressed into symplectitic low-Na clinopyroxene (Cpx) and oligo-clase (Oli) and further replaced by amphibole (Amp)] (h) Densely packed quartz exsolution rods in Omp (i) Amphibolite-faciesretrogression of eclogite in the Xiarihamu terrane with omphacite replaced by amphibole and rutile (Rt) by titanite (Ttn)
Journal of Petrology 2018 Vol 59 No 11 2045
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discovered in the Kehete terrane The metapelite sam-
ples have a schistose structure with red grains of gar-
net and foliated mica in outcrop The rocks are
composed of garnet (5ndash15) muscovite (20ndash30) bio-
tite (5ndash10) quartz (35ndash45) plagioclase (10) andminor tourmaline zircon and rutile Most rutile grains
in the matrix are replaced by titanite andor ilmenite No
granitic gneiss has been found in the eclogite-bearing
high-pressure terranes The rock assemblage plus
some serpentinite massifs suggests an oceanic-type
subduction melange
Most eclogite samples in the east section of the HPndashUHP belt are fresh They show granoblastic textures with
a mineral assemblage of garnet omphacite rutile quartz
and minor phengite without obvious foliation Garnet
occurs as euhedral crystals with rare zircon and rutile
inclusions (Fig 2e and f) Coesite pseudomorphs are
observed as inclusions in garnet (Fig 2g) Most ompha-cite crystals contain densely packed oriented quartz rods
(Fig 2h) Omphacite crystals are commonly replaced by
Cpx thorn Oli symplectites and further by amphibole and ru-
tile is replaced by titanite suggesting that these eclogite
samples are overprinted by later decompression and
amphibolite-facies retrogression (Fig 2i)
ANALYTICAL METHODS
Mineral compositionsPolished thin sections were produced from representa-tive pieces of the studied samples and were examined
in detail using a petrographic microscope Mineral com-
positions were analysed using an electron probe micro-
analyzer (EPMA) (JEOL JXA-8100) at Peking University
operated at 15 kV acceleration voltage with 20 nA beam
current and 1ndash5 lm beam spot Routine analyses wereobtained by counting for 20 s at peak and 5 s on back-
ground Synthetic silica (Si) and spessartine (Mn) nat-
ural sanidine (K) pyrope (Mg) andradite (Fe and Ca)
albite (Na and Al) and rutile (Ti) were used as standards
Ferric iron in minerals was determined based on the
scheme of Droop (1987)
Whole-rock major and trace elementsOn the basis of careful petrographic observations we
selected 18 samples for whole-rock major and trace
element analyses The whole-rock major element
oxides were analyzed using a Leeman Prodigy induct-
ively coupled plasma optical emission spectroscopy
system (ICP-OES) at the China University of
Geosciences Beijing (CUGB) The analytical precisions(1r) for most major elements based on master stand-
ards GSR-1 GSR-3 GSR-5 (national geological stand-
ard reference materials of China) and USGS AGV-2 are
better than 1 except for TiO2 (15) and P2O5
(20) Loss on ignition (LOI) was determined by plac-
ing 1 g of sample powder in a furnace at 1000C for sev-eral hours before being cooled in a desiccator and
reweighed (Song et al 2010)
The trace element compositions of Haolaoluchang
volcanic samples were determined by inductively
coupled plasma mass spectrometry (ICP-MS) using an
Agilent-7500a quadrupole system in the Institute of
Earth Science CUGB About 40 mg power for each sam-ple was dissolved in a distilled acid mixture (11 HNO3ndash
HF) in a Teflon digesting vessel and heated on a hot-
plate at 185C for 48 h using high-pressure bombs for
digestionndashdissolution The sample was then evaporated
to incipient dryness refluxed with 1 ml 6N HNO3 and
heated again to incipient dryness The sample was
again dissolved in 2 ml of 3N HNO3 in a high-pressurebomb at 165C for a further 24 h to ensure complete dis-
solution Such digested samples were finally diluted
with Milli-Q water to a dilution factor of 2000 in 2
HNO3 solution for analysis Master standards (GSR-1
GSR-3 GSR-5 and USGS AGV-2) were used to monitor
the analytical accuracy and precision Analytical accur-acy as indicated by a relative difference between meas-
ured and recommended values is better than 5 for
most elements and 10ndash15 for Cu Zn Gd and Ta
Zircon preparation and UndashThndashPb analysisThe samples were crushed and sieved to 300 lm forthe first separation and then to 100 lm for the second
separation Zircons were separated by combining mag-
netic and heavy liquid methods before finally hand-
picking under a binocular microscope Zircon grains to-
gether with zircon standard 91500 were mounted in
epoxy mounts which were then polished to section thecrystals in half for analysis All zircons were docu-
mented with transmitted and reflected light micro-
graphs as well as cathodoluminescence (CL) images to
reveal their internal structures and the mount was
vacuum-coated with high-purity gold prior to secondary
ion mass spectrometry (SIMS) analysis The CL images
were obtained on an FEI Philips XL30 SFEG SEM with2 min scanning time at conditions of 15 kV and 20 nA at
Peking University
Measurements of U Th and Pb were conducted
using the Cameca IMS-1280 SIMS system at the
Institute of Geology and Geophysics Chinese Academy
of Sciences in Beijing UndashThndashPb ratios and absoluteabundances were determined relative to the standard
zircon 91500 (Wiedenbeck et al 1995) analyses of
which were interspersed with those of unknown grains
using operating and data processing procedures similar
to those described by Li et al (2009) A long-term uncer-
tainty of 15 (1RSD) for 206Pb238U measurements of
the standard zircons was propagated to the unknowns(Li et al 2010) despite the fact that the measured206Pb238U error in a specific session is generally around
1 (1RSD) or less Measured compositions were cor-
rected for common Pb using non-radiogenic 204Pb
Corrections are sufficiently small to be insensitive to the
choice of common Pb composition and an average ofthe present-day crustal composition (Stacey amp Kramers
1975) was used for the common Pb assuming that the
2046 Journal of Petrology 2018 Vol 59 No 11
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Tab
le1
Re
pre
sen
tati
ve
an
aly
ses
of
ga
rne
tin
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(HK
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
26
-11
6K
L2
6-2
16
KL
27
-11
6K
L2
7-2
16
KL
27
-31
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
7A
-31
4k2
-11
4k2
-21
4k2
-31
4k4
-11
4k4
-21
4k4
-31
4k5
-11
4k5
-21
4k5
-3L
oca
tio
n
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
23
76
63
87
33
79
33
83
23
86
33
88
13
84
53
81
83
83
93
84
53
89
43
67
73
79
33
89
33
84
83
84
23
91
63
88
23
92
9T
iO2
01
201
100
701
001
100
100
800
300
700
500
501
401
001
300
701
600
001
100
7A
l 2O
32
10
62
12
82
08
72
17
12
17
12
13
62
14
72
15
02
13
12
14
22
22
02
11
92
22
32
18
32
15
12
17
32
22
32
23
12
24
6C
r 2O
300
100
700
000
100
000
300
400
100
000
400
200
000
600
000
000
200
400
100
1F
eO
265
52
22
42
58
92
62
12
18
92
20
92
22
82
31
72
31
42
28
82
54
82
58
62
59
62
59
62
87
02
80
62
57
12
36
92
46
3M
nO
05
304
005
003
604
804
005
005
104
704
202
705
407
604
505
603
500
908
500
5N
iO00
500
000
001
000
000
300
000
500
000
000
000
400
000
400
200
400
300
000
0M
gO
50
070
271
471
970
669
568
367
368
067
033
420
420
843
323
431
337
235
338
0C
aO
82
895
765
562
798
799
991
289
193
896
51
10
91
20
51
21
995
61
00
699
11
00
41
20
91
13
3N
a2O
00
600
600
400
500
500
500
000
800
300
100
000
100
000
600
000
000
500
000
0K
2O
00
100
000
000
100
000
000
000
300
000
100
000
000
000
100
000
300
000
000
0T
ota
l9
93
39
94
89
91
003
29
98
997
39
87
79
92
995
99
96
21
014
986
21
013
11
012
91
017
41
018
51
010
61
014
11
016
4C
alc
ula
tio
nu
sin
g1
2o
xy
ge
nS
i29
62
29
87
29
64
29
52
29
66
29
85
29
91
29
61
29
66
29
69
30
08
29
44
29
53
30
03
29
99
29
76
30
30
29
88
30
15
Ti
00
07
00
06
00
04
00
06
00
06
00
01
00
05
00
02
00
04
00
03
00
03
00
08
00
06
00
08
00
04
00
09
00
00
00
06
00
04
Al
19
52
19
34
19
22
19
71
19
64
19
36
19
68
19
65
19
40
19
49
20
21
19
99
20
39
19
85
19
76
19
84
20
27
20
23
20
31
Cr
00
01
00
04
00
00
00
01
00
00
00
02
00
02
00
01
00
00
00
02
00
01
00
00
00
04
00
00
00
00
00
01
00
02
00
01
00
01
Fe
3thorn
01
20
00
83
01
49
01
20
00
99
00
98
00
39
01
25
01
24
01
07
00
00
00
98
00
39
00
04
00
17
00
47
00
00
00
00
00
00
Fe
2thorn
16
26
13
52
15
42
15
68
13
06
13
23
14
10
13
78
13
71
13
70
16
46
16
33
16
50
16
71
18
53
17
70
16
64
15
25
15
80
Mn
00
35
00
26
00
33
00
24
00
31
00
26
00
33
00
34
00
31
00
28
00
18
00
37
00
50
00
29
00
37
00
23
00
06
00
55
00
03
Ni
00
03
00
00
00
00
00
06
00
00
00
02
00
00
00
03
00
00
00
00
00
00
00
03
00
00
00
02
00
01
00
02
00
02
00
00
00
00
Mg
05
86
08
07
08
32
08
26
08
08
07
97
07
92
07
78
07
83
07
71
03
85
02
43
02
41
04
98
02
72
03
61
04
29
04
05
04
35
Ca
06
98
07
91
05
48
05
18
08
12
08
23
07
60
07
40
07
76
07
98
09
18
10
33
10
17
07
90
08
40
08
22
08
32
09
97
09
31
Na
00
09
00
09
00
06
00
07
00
07
00
07
00
00
00
12
00
04
00
01
00
00
00
02
00
00
00
09
00
00
00
00
00
08
00
00
00
00
K00
01
00
00
00
00
00
01
00
00
00
00
00
00
00
03
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
03
00
00
00
00
00
00
Su
m8
88
88
88
88
88
88
88
88
88
Py
rop
e1
91
32
63
92
67
92
70
32
64
42
59
82
61
02
54
72
53
92
50
91
29
780
080
51
66
490
11
19
51
46
41
35
81
47
4A
lm5
69
64
69
05
44
85
52
64
59
84
63
24
77
64
91
94
84
54
80
55
54
95
68
65
63
65
59
76
19
56
01
05
67
65
11
35
35
8S
pe
ss11
508
610
707
710
208
510
911
010
008
906
012
016
709
812
307
602
018
601
1U
va
ro00
302
200
000
300
000
901
200
300
001
300
600
001
800
000
000
601
200
300
3G
ross
ula
r2
27
32
56
31
76
61
69
12
65
62
67
52
49
22
42
02
51
62
58
43
08
83
39
43
37
32
64
12
78
22
71
32
82
83
34
03
15
5
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
cea
fte
rD
roo
p(1
98
7)
Journal of Petrology 2018 Vol 59 No 11 2047
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icoupcompetrologyarticle-abstract591120435104339 by U
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Tab
le2
Re
pre
sen
tati
ve
an
aly
ses
of
om
ph
aci
tein
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(KH
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
13
-31
6K
L2
7-1
16
KL
27
-21
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
6-1
16
KL
26
-21
4k2
-11
4k4
-11
4k4
-21
4k4
-31
4k4
-5k4
-51
k4-61
k4-75
XR
1-1
XR
2-1
Lo
cati
on
H
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
25
60
55
54
05
53
35
53
15
53
75
53
15
53
95
54
45
52
45
48
55
17
35
24
25
48
85
53
15
45
65
26
25
27
95
46
95
39
9T
iO2
00
901
701
001
000
501
402
101
101
601
300
600
700
700
901
200
601
001
401
6A
l 2O
393
298
996
91
00
194
998
390
891
190
557
147
245
654
952
153
731
347
278
081
0C
r 2O
300
400
000
000
000
300
000
000
000
600
700
100
400
000
000
500
000
700
300
6F
eO
64
765
363
068
845
744
262
160
260
469
91
41
11
03
082
376
085
41
04
394
153
350
9M
nO
00
300
900
200
600
000
300
300
200
201
001
000
200
800
000
100
900
100
600
2N
iO00
000
500
000
600
500
000
000
000
000
000
700
000
600
600
000
000
000
600
0M
gO
73
373
571
675
292
292
091
188
388
51
15
61
05
81
03
21
03
61
06
71
06
61
14
71
07
299
81
01
0C
aO
136
01
36
91
36
71
25
01
48
51
45
11
36
61
37
51
37
81
87
31
75
11
93
01
75
11
79
01
72
92
13
31
82
81
58
01
59
4N
a2O
67
465
869
668
359
962
963
662
064
221
715
425
836
436
738
213
733
753
056
9K
2O
00
400
200
100
100
000
100
000
200
000
300
100
000
000
300
000
100
000
000
1T
ota
l9
97
29
97
69
92
49
92
89
96
19
97
41
000
59
94
99
96
21
003
51
004
59
96
10
02
21
005
31
004
21
005
994
79
91
99
91
7C
alc
ula
tio
nu
sin
g6
ox
yg
en
Si
20
16
19
93
19
95
19
95
19
82
19
72
19
78
19
93
19
81
20
09
19
37
19
49
20
02
20
08
19
84
19
53
19
47
19
77
19
43
Ti
00
02
00
05
00
03
00
03
00
01
00
04
00
06
00
03
00
04
00
04
00
02
00
02
00
02
00
02
00
03
00
02
00
03
00
04
00
04
Al
03
95
04
19
04
12
04
26
04
00
04
13
03
82
03
86
03
82
02
46
02
08
02
00
02
36
02
23
02
30
01
37
02
05
03
32
03
44
Cr
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
02
00
02
00
00
00
01
00
00
00
00
00
01
00
00
00
02
00
01
00
02
Fe
3thorn
00
37
800
44
500
79
700
56
900
47
800
70
600
90
900
54
400
91
700
00
000
26
000
82
600
14
000
15
100
62
800
52
801
34
400
77
01
53
Fe
2thorn
01
57
01
52
01
10
01
51
00
89
00
61
00
95
01
27
00
89
02
14
04
16
02
38
02
37
02
16
01
97
02
71
01
56
00
85
00
00
Mn
00
01
00
03
00
01
00
02
00
00
00
01
00
01
00
01
00
01
00
03
00
03
00
01
00
02
00
00
00
00
00
03
00
00
00
02
00
01
Ni
00
00
00
01
00
00
00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
02
00
00
00
02
00
02
00
00
00
00
00
00
00
02
00
00
Mg
03
93
03
94
03
85
04
04
04
92
04
89
04
85
04
73
04
73
06
31
05
91
05
72
05
63
05
78
05
78
06
35
05
89
05
38
05
42
Ca
05
24
05
28
05
28
04
83
05
69
05
54
05
23
05
30
05
29
07
35
07
02
07
69
06
84
06
96
06
74
08
48
07
22
06
12
06
15
Na
04
70
04
59
04
87
04
78
04
16
04
35
04
40
04
32
04
46
01
54
01
12
01
86
02
57
02
58
02
69
00
99
02
41
03
71
03
97
K00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
01
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
00
00
00
Su
m4
44
44
44
44
44
44
44
44
44
Jd
414
14
17
44
09
54
23
43
83
73
88
83
65
83
82
43
67
72
59
11
47
21
51
02
39
72
33
82
17
691
61
54
83
13
22
90
7A
e37
844
579
756
947
870
690
954
491
700
026
082
614
015
162
852
81
34
476
51
53
2W
EF
548
15
38
15
10
85
19
75
68
55
40
65
43
35
63
25
40
67
40
98
26
97
66
47
46
37
51
17
19
68
55
67
10
86
10
35
56
1
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
ce(D
roo
p1
98
7)
2048 Journal of Petrology 2018 Vol 59 No 11
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common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
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Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
2050 Journal of Petrology 2018 Vol 59 No 11
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
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Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
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The QinlingndashQilianndashKunlun orogenic belt (or the
Central China Orogenic Belt) lies in the central part of
China and is considered to have resulted from the con-
sumption of the Proto-Tethys (eg Yin amp Harrison 2000
Dong amp Santosh 2016 Song et al 2017) The EastKunlun the west part of the QinlingndashQilianndashKunlun
Mountains (Fig 1) is a long-lived orogenic belt with a
history from Cambrian to Triassic times which records
the orogenic evolution of the Proto- and Paleo-Tethys
oceans and holds the key to understanding the evolu-
tion of the ancient Tethys Ocean and formation of the
Chinese continent Eclogite blocks were reported byMeng et al (2013) and subsequently by Qi et al (2016)
at Wenquan in the east and by Qi et al (2014) at
Xiarihamu in the west of the East Kunlun Orogen (EKO)
(Fig 1) With the addition of a newly discovered
eclogite-bearing locality at Kehete in the mid-east a
500 km long eclogite-bearing high-pressure meta-morphic belt can be recognized within the EKO In this
study we present petrological geochemical and geo-
chronological studies of this eclogite belt We have
determined for the first time that some of the EKO eclo-
gites have experienced UHP metamorphism in
SilurianndashDevonian times This eclogite belt togetherwith accompanying ophiolites and arc volcanic rocks
represents the final closure of the Proto-Tethys Ocean
and continued convergence between fragments of
Eastern Gondwanaland and the North ChinandashTarim
continent
Mineral abbreviations are after Whitney amp Evans
(2010)
GEOLOGICAL SETTING AND PETROGRAPHY
The East Kunlun Orogen lies south of the Qaidam Block
(Fig 1) The basement of the Qaidam Block is largely
covered by thick sedimentary successions of a
Mesozoic to Cenozoic intracontinental basin The
Precambrian crystalline basement is mainly exposed at
the north and south margins of the block To the north
of the Qaidam Block is the North Qaidam ultrahigh-pressure metamorphic (UHPM) belt which consists of
various types of eclogite garnet peridotite coesite-
bearing metapelite and granitic gneiss The North
Qaidam UHPM belt is a continental collision zone
recording that the Qaidam Block had subducted north-
wards to depths of 200 km at 440ndash425 Ma (eg Song
et al 2014 and references therein) Further north theQilian Orogen consists of the South Qilian oceanic
accretionary belt the Central Qilian Block and the North
Qilian oceanic accretionary belt The South Qilian
oceanic accretionary belt (SQAB) is composed of
Cambrian ophiolites (535ndash500 Ma) and an Ordovician
intra-oceanic arc complex (470ndash440 Ma) (eg Songet al 2017 Zhang et al 2017) without high-pressure
rocks The North Qilian oceanic accretionary belt
(NQAB) consists of 550ndash450 Ma ophiolites 520ndash440 Ma
continental arc volcanic and plutonic rocks and 500ndash
440 Ma high-pressure metamorphic rocks Carpholite in
metapelites and lawsonite in eclogites and blueschistssuggest relatively cold oceanic subduction and high-
pressurelow-temperature (HPLT) metamorphism
(Song et al 2007 Zhang et al 2007) Therefore three
subparallel HPndashUHP belts are exposed in a 400 km wide
region in the northern Tibetan Plateau (Fig 1) These
HPndashUHP belts together with associated ophiolites and
arc rocks record the evolution of the northern Proto-Tethys Ocean from ocean-floor subduction and con-
sumption to subsequent continental collision (Song
et al 2006 2014)
The East Kunlun Orogen records a long and complex
history from Cambrian to Triassic times (Dong et al
Fig 1 Simplified geological map of the northern Tibetan Plateau showing HPndashUHP metamorphic terranes in three orogenic beltsCAOB Central Asian Orogenic Belt CCOB Central China Orogenic Belt HOB Himalayan Orogenic Belt NCC North China CratonNQ-SP North QiangtangndashSongpan Block SCC South China Craton QLB QiangtangndashLhasa Block TB Tarim Block NQAB NorthQilian Accretionary Belt SQAB South Qilian Accretionary Belt NQUB North Qaidam UHPM Belt EKO East Kunlun Orogen CQBCentral Qilian Block
2044 Journal of Petrology 2018 Vol 59 No 11
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2018 Li et al 2018) It mainly consists of (1) an Early
Paleozoic accretionary complex at the southwestern
margin of the Qaidam Block (2) the Arsquonyemaqen accre-
tionary complex in the south (3) Precambrian base-
ment (the South Kunlun Block) and (4) Triassic volcanicand plutonic rocks distributed throughout the East
Kunlun Orogen Ophiolites in the Early Paleozoic accre-
tionary complex formed over a long period from 537 to
460 Ma (Yang et al 1996 Bian et al 2004 Meng et al
2015 Qi et al 2016 Li et al 2018) the same as ophio-
lites in the QilianndashQaidam region to the north (Song
et al 2013) The types of ophiolite are not well docu-mented partly because most ophiolites are strongly
deformed and fragmented Basalts with pillow structure
show characteristics of normal- to enriched-mid-ocean
ridge basalt (N- to E-MORB) affinity (Yang et al 1996
Qi et al 2016) most probably representative of MORB-
type ophiolites (eg Topuz et al 2018) Arc volcanicrocks include Alaskan-type ultramaficndashmafic intrusions
with CundashNi ore-deposits andesitesndashrhyolites and
granites with SilurianndashDevonian ages (450ndash400 Ma) (eg
Zhu et al 2006 Wang et al 2014) Three eclogite-
bearing regions from east to west Wenquan Kehete
and Xiarihamu are distributed discontinuously along
the Early Paleozoic accretionary belt (Fig 1) TheArsquonyemaqen accretionary complex in the south is main-
ly a melange belt with 460ndash308 Ma ophiolitic fragments
(Bian et al 2004 Yang et al 2004) The Precambrian
basement in the EKO mainly consists of 1200ndash950 Ma
Mesoproterozoic granitic gneisses Detrital zircons from
metapelite (KL33) yielded an age peak at 2482 Ma with
secondary age groups of 2686ndash2505 and 2180ndash1054 Madetrital zircons from late Neoproterozoic sedimentary
rocks (Golmud region) yield a major age group of 1465ndash
802 Ma and three minor age groups of 1892ndash1758
2502ndash2431 and 3308 Ma (authorrsquos unpublished data)
All eclogites in the three terranes occur as lens-
shaped blocks of varying size (5ndash100 m in length) withinmetasedimentary hosts including metapelite and mar-
ble (Fig 2andashd) A serpentinite block has also been
Fig 2 Field photographs and photomicrographs of the eclogite belt in the EKO (a) Eclogite block within garnetndashmica schist (meta-pelite) from Kehete terrane (b) Eclogite block with weak alteration (Kehete terrane) (c) Eclogite blocks with marble (Xiarihamu ter-rane) (d) Eclogite blocks within metapelite (Xiarihamu terrane) (e) Photomicrograph of eclogite with the mineral assemblagegarnet (Grt) omphacite (Omp) phengite (Phn) rutile (Rt) and quartz (16KL13) (f) Coesite-pseudomorphs (Coe-P) in omphacite (g)Coesite-pseudomorph (Coe-P) in garnet [Note Omp rims decompressed into symplectitic low-Na clinopyroxene (Cpx) and oligo-clase (Oli) and further replaced by amphibole (Amp)] (h) Densely packed quartz exsolution rods in Omp (i) Amphibolite-faciesretrogression of eclogite in the Xiarihamu terrane with omphacite replaced by amphibole and rutile (Rt) by titanite (Ttn)
Journal of Petrology 2018 Vol 59 No 11 2045
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discovered in the Kehete terrane The metapelite sam-
ples have a schistose structure with red grains of gar-
net and foliated mica in outcrop The rocks are
composed of garnet (5ndash15) muscovite (20ndash30) bio-
tite (5ndash10) quartz (35ndash45) plagioclase (10) andminor tourmaline zircon and rutile Most rutile grains
in the matrix are replaced by titanite andor ilmenite No
granitic gneiss has been found in the eclogite-bearing
high-pressure terranes The rock assemblage plus
some serpentinite massifs suggests an oceanic-type
subduction melange
Most eclogite samples in the east section of the HPndashUHP belt are fresh They show granoblastic textures with
a mineral assemblage of garnet omphacite rutile quartz
and minor phengite without obvious foliation Garnet
occurs as euhedral crystals with rare zircon and rutile
inclusions (Fig 2e and f) Coesite pseudomorphs are
observed as inclusions in garnet (Fig 2g) Most ompha-cite crystals contain densely packed oriented quartz rods
(Fig 2h) Omphacite crystals are commonly replaced by
Cpx thorn Oli symplectites and further by amphibole and ru-
tile is replaced by titanite suggesting that these eclogite
samples are overprinted by later decompression and
amphibolite-facies retrogression (Fig 2i)
ANALYTICAL METHODS
Mineral compositionsPolished thin sections were produced from representa-tive pieces of the studied samples and were examined
in detail using a petrographic microscope Mineral com-
positions were analysed using an electron probe micro-
analyzer (EPMA) (JEOL JXA-8100) at Peking University
operated at 15 kV acceleration voltage with 20 nA beam
current and 1ndash5 lm beam spot Routine analyses wereobtained by counting for 20 s at peak and 5 s on back-
ground Synthetic silica (Si) and spessartine (Mn) nat-
ural sanidine (K) pyrope (Mg) andradite (Fe and Ca)
albite (Na and Al) and rutile (Ti) were used as standards
Ferric iron in minerals was determined based on the
scheme of Droop (1987)
Whole-rock major and trace elementsOn the basis of careful petrographic observations we
selected 18 samples for whole-rock major and trace
element analyses The whole-rock major element
oxides were analyzed using a Leeman Prodigy induct-
ively coupled plasma optical emission spectroscopy
system (ICP-OES) at the China University of
Geosciences Beijing (CUGB) The analytical precisions(1r) for most major elements based on master stand-
ards GSR-1 GSR-3 GSR-5 (national geological stand-
ard reference materials of China) and USGS AGV-2 are
better than 1 except for TiO2 (15) and P2O5
(20) Loss on ignition (LOI) was determined by plac-
ing 1 g of sample powder in a furnace at 1000C for sev-eral hours before being cooled in a desiccator and
reweighed (Song et al 2010)
The trace element compositions of Haolaoluchang
volcanic samples were determined by inductively
coupled plasma mass spectrometry (ICP-MS) using an
Agilent-7500a quadrupole system in the Institute of
Earth Science CUGB About 40 mg power for each sam-ple was dissolved in a distilled acid mixture (11 HNO3ndash
HF) in a Teflon digesting vessel and heated on a hot-
plate at 185C for 48 h using high-pressure bombs for
digestionndashdissolution The sample was then evaporated
to incipient dryness refluxed with 1 ml 6N HNO3 and
heated again to incipient dryness The sample was
again dissolved in 2 ml of 3N HNO3 in a high-pressurebomb at 165C for a further 24 h to ensure complete dis-
solution Such digested samples were finally diluted
with Milli-Q water to a dilution factor of 2000 in 2
HNO3 solution for analysis Master standards (GSR-1
GSR-3 GSR-5 and USGS AGV-2) were used to monitor
the analytical accuracy and precision Analytical accur-acy as indicated by a relative difference between meas-
ured and recommended values is better than 5 for
most elements and 10ndash15 for Cu Zn Gd and Ta
Zircon preparation and UndashThndashPb analysisThe samples were crushed and sieved to 300 lm forthe first separation and then to 100 lm for the second
separation Zircons were separated by combining mag-
netic and heavy liquid methods before finally hand-
picking under a binocular microscope Zircon grains to-
gether with zircon standard 91500 were mounted in
epoxy mounts which were then polished to section thecrystals in half for analysis All zircons were docu-
mented with transmitted and reflected light micro-
graphs as well as cathodoluminescence (CL) images to
reveal their internal structures and the mount was
vacuum-coated with high-purity gold prior to secondary
ion mass spectrometry (SIMS) analysis The CL images
were obtained on an FEI Philips XL30 SFEG SEM with2 min scanning time at conditions of 15 kV and 20 nA at
Peking University
Measurements of U Th and Pb were conducted
using the Cameca IMS-1280 SIMS system at the
Institute of Geology and Geophysics Chinese Academy
of Sciences in Beijing UndashThndashPb ratios and absoluteabundances were determined relative to the standard
zircon 91500 (Wiedenbeck et al 1995) analyses of
which were interspersed with those of unknown grains
using operating and data processing procedures similar
to those described by Li et al (2009) A long-term uncer-
tainty of 15 (1RSD) for 206Pb238U measurements of
the standard zircons was propagated to the unknowns(Li et al 2010) despite the fact that the measured206Pb238U error in a specific session is generally around
1 (1RSD) or less Measured compositions were cor-
rected for common Pb using non-radiogenic 204Pb
Corrections are sufficiently small to be insensitive to the
choice of common Pb composition and an average ofthe present-day crustal composition (Stacey amp Kramers
1975) was used for the common Pb assuming that the
2046 Journal of Petrology 2018 Vol 59 No 11
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Tab
le1
Re
pre
sen
tati
ve
an
aly
ses
of
ga
rne
tin
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(HK
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
26
-11
6K
L2
6-2
16
KL
27
-11
6K
L2
7-2
16
KL
27
-31
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
7A
-31
4k2
-11
4k2
-21
4k2
-31
4k4
-11
4k4
-21
4k4
-31
4k5
-11
4k5
-21
4k5
-3L
oca
tio
n
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
23
76
63
87
33
79
33
83
23
86
33
88
13
84
53
81
83
83
93
84
53
89
43
67
73
79
33
89
33
84
83
84
23
91
63
88
23
92
9T
iO2
01
201
100
701
001
100
100
800
300
700
500
501
401
001
300
701
600
001
100
7A
l 2O
32
10
62
12
82
08
72
17
12
17
12
13
62
14
72
15
02
13
12
14
22
22
02
11
92
22
32
18
32
15
12
17
32
22
32
23
12
24
6C
r 2O
300
100
700
000
100
000
300
400
100
000
400
200
000
600
000
000
200
400
100
1F
eO
265
52
22
42
58
92
62
12
18
92
20
92
22
82
31
72
31
42
28
82
54
82
58
62
59
62
59
62
87
02
80
62
57
12
36
92
46
3M
nO
05
304
005
003
604
804
005
005
104
704
202
705
407
604
505
603
500
908
500
5N
iO00
500
000
001
000
000
300
000
500
000
000
000
400
000
400
200
400
300
000
0M
gO
50
070
271
471
970
669
568
367
368
067
033
420
420
843
323
431
337
235
338
0C
aO
82
895
765
562
798
799
991
289
193
896
51
10
91
20
51
21
995
61
00
699
11
00
41
20
91
13
3N
a2O
00
600
600
400
500
500
500
000
800
300
100
000
100
000
600
000
000
500
000
0K
2O
00
100
000
000
100
000
000
000
300
000
100
000
000
000
100
000
300
000
000
0T
ota
l9
93
39
94
89
91
003
29
98
997
39
87
79
92
995
99
96
21
014
986
21
013
11
012
91
017
41
018
51
010
61
014
11
016
4C
alc
ula
tio
nu
sin
g1
2o
xy
ge
nS
i29
62
29
87
29
64
29
52
29
66
29
85
29
91
29
61
29
66
29
69
30
08
29
44
29
53
30
03
29
99
29
76
30
30
29
88
30
15
Ti
00
07
00
06
00
04
00
06
00
06
00
01
00
05
00
02
00
04
00
03
00
03
00
08
00
06
00
08
00
04
00
09
00
00
00
06
00
04
Al
19
52
19
34
19
22
19
71
19
64
19
36
19
68
19
65
19
40
19
49
20
21
19
99
20
39
19
85
19
76
19
84
20
27
20
23
20
31
Cr
00
01
00
04
00
00
00
01
00
00
00
02
00
02
00
01
00
00
00
02
00
01
00
00
00
04
00
00
00
00
00
01
00
02
00
01
00
01
Fe
3thorn
01
20
00
83
01
49
01
20
00
99
00
98
00
39
01
25
01
24
01
07
00
00
00
98
00
39
00
04
00
17
00
47
00
00
00
00
00
00
Fe
2thorn
16
26
13
52
15
42
15
68
13
06
13
23
14
10
13
78
13
71
13
70
16
46
16
33
16
50
16
71
18
53
17
70
16
64
15
25
15
80
Mn
00
35
00
26
00
33
00
24
00
31
00
26
00
33
00
34
00
31
00
28
00
18
00
37
00
50
00
29
00
37
00
23
00
06
00
55
00
03
Ni
00
03
00
00
00
00
00
06
00
00
00
02
00
00
00
03
00
00
00
00
00
00
00
03
00
00
00
02
00
01
00
02
00
02
00
00
00
00
Mg
05
86
08
07
08
32
08
26
08
08
07
97
07
92
07
78
07
83
07
71
03
85
02
43
02
41
04
98
02
72
03
61
04
29
04
05
04
35
Ca
06
98
07
91
05
48
05
18
08
12
08
23
07
60
07
40
07
76
07
98
09
18
10
33
10
17
07
90
08
40
08
22
08
32
09
97
09
31
Na
00
09
00
09
00
06
00
07
00
07
00
07
00
00
00
12
00
04
00
01
00
00
00
02
00
00
00
09
00
00
00
00
00
08
00
00
00
00
K00
01
00
00
00
00
00
01
00
00
00
00
00
00
00
03
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
03
00
00
00
00
00
00
Su
m8
88
88
88
88
88
88
88
88
88
Py
rop
e1
91
32
63
92
67
92
70
32
64
42
59
82
61
02
54
72
53
92
50
91
29
780
080
51
66
490
11
19
51
46
41
35
81
47
4A
lm5
69
64
69
05
44
85
52
64
59
84
63
24
77
64
91
94
84
54
80
55
54
95
68
65
63
65
59
76
19
56
01
05
67
65
11
35
35
8S
pe
ss11
508
610
707
710
208
510
911
010
008
906
012
016
709
812
307
602
018
601
1U
va
ro00
302
200
000
300
000
901
200
300
001
300
600
001
800
000
000
601
200
300
3G
ross
ula
r2
27
32
56
31
76
61
69
12
65
62
67
52
49
22
42
02
51
62
58
43
08
83
39
43
37
32
64
12
78
22
71
32
82
83
34
03
15
5
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
cea
fte
rD
roo
p(1
98
7)
Journal of Petrology 2018 Vol 59 No 11 2047
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le2
Re
pre
sen
tati
ve
an
aly
ses
of
om
ph
aci
tein
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(KH
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
13
-31
6K
L2
7-1
16
KL
27
-21
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
6-1
16
KL
26
-21
4k2
-11
4k4
-11
4k4
-21
4k4
-31
4k4
-5k4
-51
k4-61
k4-75
XR
1-1
XR
2-1
Lo
cati
on
H
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
25
60
55
54
05
53
35
53
15
53
75
53
15
53
95
54
45
52
45
48
55
17
35
24
25
48
85
53
15
45
65
26
25
27
95
46
95
39
9T
iO2
00
901
701
001
000
501
402
101
101
601
300
600
700
700
901
200
601
001
401
6A
l 2O
393
298
996
91
00
194
998
390
891
190
557
147
245
654
952
153
731
347
278
081
0C
r 2O
300
400
000
000
000
300
000
000
000
600
700
100
400
000
000
500
000
700
300
6F
eO
64
765
363
068
845
744
262
160
260
469
91
41
11
03
082
376
085
41
04
394
153
350
9M
nO
00
300
900
200
600
000
300
300
200
201
001
000
200
800
000
100
900
100
600
2N
iO00
000
500
000
600
500
000
000
000
000
000
700
000
600
600
000
000
000
600
0M
gO
73
373
571
675
292
292
091
188
388
51
15
61
05
81
03
21
03
61
06
71
06
61
14
71
07
299
81
01
0C
aO
136
01
36
91
36
71
25
01
48
51
45
11
36
61
37
51
37
81
87
31
75
11
93
01
75
11
79
01
72
92
13
31
82
81
58
01
59
4N
a2O
67
465
869
668
359
962
963
662
064
221
715
425
836
436
738
213
733
753
056
9K
2O
00
400
200
100
100
000
100
000
200
000
300
100
000
000
300
000
100
000
000
1T
ota
l9
97
29
97
69
92
49
92
89
96
19
97
41
000
59
94
99
96
21
003
51
004
59
96
10
02
21
005
31
004
21
005
994
79
91
99
91
7C
alc
ula
tio
nu
sin
g6
ox
yg
en
Si
20
16
19
93
19
95
19
95
19
82
19
72
19
78
19
93
19
81
20
09
19
37
19
49
20
02
20
08
19
84
19
53
19
47
19
77
19
43
Ti
00
02
00
05
00
03
00
03
00
01
00
04
00
06
00
03
00
04
00
04
00
02
00
02
00
02
00
02
00
03
00
02
00
03
00
04
00
04
Al
03
95
04
19
04
12
04
26
04
00
04
13
03
82
03
86
03
82
02
46
02
08
02
00
02
36
02
23
02
30
01
37
02
05
03
32
03
44
Cr
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
02
00
02
00
00
00
01
00
00
00
00
00
01
00
00
00
02
00
01
00
02
Fe
3thorn
00
37
800
44
500
79
700
56
900
47
800
70
600
90
900
54
400
91
700
00
000
26
000
82
600
14
000
15
100
62
800
52
801
34
400
77
01
53
Fe
2thorn
01
57
01
52
01
10
01
51
00
89
00
61
00
95
01
27
00
89
02
14
04
16
02
38
02
37
02
16
01
97
02
71
01
56
00
85
00
00
Mn
00
01
00
03
00
01
00
02
00
00
00
01
00
01
00
01
00
01
00
03
00
03
00
01
00
02
00
00
00
00
00
03
00
00
00
02
00
01
Ni
00
00
00
01
00
00
00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
02
00
00
00
02
00
02
00
00
00
00
00
00
00
02
00
00
Mg
03
93
03
94
03
85
04
04
04
92
04
89
04
85
04
73
04
73
06
31
05
91
05
72
05
63
05
78
05
78
06
35
05
89
05
38
05
42
Ca
05
24
05
28
05
28
04
83
05
69
05
54
05
23
05
30
05
29
07
35
07
02
07
69
06
84
06
96
06
74
08
48
07
22
06
12
06
15
Na
04
70
04
59
04
87
04
78
04
16
04
35
04
40
04
32
04
46
01
54
01
12
01
86
02
57
02
58
02
69
00
99
02
41
03
71
03
97
K00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
01
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
00
00
00
Su
m4
44
44
44
44
44
44
44
44
44
Jd
414
14
17
44
09
54
23
43
83
73
88
83
65
83
82
43
67
72
59
11
47
21
51
02
39
72
33
82
17
691
61
54
83
13
22
90
7A
e37
844
579
756
947
870
690
954
491
700
026
082
614
015
162
852
81
34
476
51
53
2W
EF
548
15
38
15
10
85
19
75
68
55
40
65
43
35
63
25
40
67
40
98
26
97
66
47
46
37
51
17
19
68
55
67
10
86
10
35
56
1
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
ce(D
roo
p1
98
7)
2048 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
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icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
2050 Journal of Petrology 2018 Vol 59 No 11
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
2052 Journal of Petrology 2018 Vol 59 No 11
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
2018 Li et al 2018) It mainly consists of (1) an Early
Paleozoic accretionary complex at the southwestern
margin of the Qaidam Block (2) the Arsquonyemaqen accre-
tionary complex in the south (3) Precambrian base-
ment (the South Kunlun Block) and (4) Triassic volcanicand plutonic rocks distributed throughout the East
Kunlun Orogen Ophiolites in the Early Paleozoic accre-
tionary complex formed over a long period from 537 to
460 Ma (Yang et al 1996 Bian et al 2004 Meng et al
2015 Qi et al 2016 Li et al 2018) the same as ophio-
lites in the QilianndashQaidam region to the north (Song
et al 2013) The types of ophiolite are not well docu-mented partly because most ophiolites are strongly
deformed and fragmented Basalts with pillow structure
show characteristics of normal- to enriched-mid-ocean
ridge basalt (N- to E-MORB) affinity (Yang et al 1996
Qi et al 2016) most probably representative of MORB-
type ophiolites (eg Topuz et al 2018) Arc volcanicrocks include Alaskan-type ultramaficndashmafic intrusions
with CundashNi ore-deposits andesitesndashrhyolites and
granites with SilurianndashDevonian ages (450ndash400 Ma) (eg
Zhu et al 2006 Wang et al 2014) Three eclogite-
bearing regions from east to west Wenquan Kehete
and Xiarihamu are distributed discontinuously along
the Early Paleozoic accretionary belt (Fig 1) TheArsquonyemaqen accretionary complex in the south is main-
ly a melange belt with 460ndash308 Ma ophiolitic fragments
(Bian et al 2004 Yang et al 2004) The Precambrian
basement in the EKO mainly consists of 1200ndash950 Ma
Mesoproterozoic granitic gneisses Detrital zircons from
metapelite (KL33) yielded an age peak at 2482 Ma with
secondary age groups of 2686ndash2505 and 2180ndash1054 Madetrital zircons from late Neoproterozoic sedimentary
rocks (Golmud region) yield a major age group of 1465ndash
802 Ma and three minor age groups of 1892ndash1758
2502ndash2431 and 3308 Ma (authorrsquos unpublished data)
All eclogites in the three terranes occur as lens-
shaped blocks of varying size (5ndash100 m in length) withinmetasedimentary hosts including metapelite and mar-
ble (Fig 2andashd) A serpentinite block has also been
Fig 2 Field photographs and photomicrographs of the eclogite belt in the EKO (a) Eclogite block within garnetndashmica schist (meta-pelite) from Kehete terrane (b) Eclogite block with weak alteration (Kehete terrane) (c) Eclogite blocks with marble (Xiarihamu ter-rane) (d) Eclogite blocks within metapelite (Xiarihamu terrane) (e) Photomicrograph of eclogite with the mineral assemblagegarnet (Grt) omphacite (Omp) phengite (Phn) rutile (Rt) and quartz (16KL13) (f) Coesite-pseudomorphs (Coe-P) in omphacite (g)Coesite-pseudomorph (Coe-P) in garnet [Note Omp rims decompressed into symplectitic low-Na clinopyroxene (Cpx) and oligo-clase (Oli) and further replaced by amphibole (Amp)] (h) Densely packed quartz exsolution rods in Omp (i) Amphibolite-faciesretrogression of eclogite in the Xiarihamu terrane with omphacite replaced by amphibole and rutile (Rt) by titanite (Ttn)
Journal of Petrology 2018 Vol 59 No 11 2045
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icoupcompetrologyarticle-abstract591120435104339 by U
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discovered in the Kehete terrane The metapelite sam-
ples have a schistose structure with red grains of gar-
net and foliated mica in outcrop The rocks are
composed of garnet (5ndash15) muscovite (20ndash30) bio-
tite (5ndash10) quartz (35ndash45) plagioclase (10) andminor tourmaline zircon and rutile Most rutile grains
in the matrix are replaced by titanite andor ilmenite No
granitic gneiss has been found in the eclogite-bearing
high-pressure terranes The rock assemblage plus
some serpentinite massifs suggests an oceanic-type
subduction melange
Most eclogite samples in the east section of the HPndashUHP belt are fresh They show granoblastic textures with
a mineral assemblage of garnet omphacite rutile quartz
and minor phengite without obvious foliation Garnet
occurs as euhedral crystals with rare zircon and rutile
inclusions (Fig 2e and f) Coesite pseudomorphs are
observed as inclusions in garnet (Fig 2g) Most ompha-cite crystals contain densely packed oriented quartz rods
(Fig 2h) Omphacite crystals are commonly replaced by
Cpx thorn Oli symplectites and further by amphibole and ru-
tile is replaced by titanite suggesting that these eclogite
samples are overprinted by later decompression and
amphibolite-facies retrogression (Fig 2i)
ANALYTICAL METHODS
Mineral compositionsPolished thin sections were produced from representa-tive pieces of the studied samples and were examined
in detail using a petrographic microscope Mineral com-
positions were analysed using an electron probe micro-
analyzer (EPMA) (JEOL JXA-8100) at Peking University
operated at 15 kV acceleration voltage with 20 nA beam
current and 1ndash5 lm beam spot Routine analyses wereobtained by counting for 20 s at peak and 5 s on back-
ground Synthetic silica (Si) and spessartine (Mn) nat-
ural sanidine (K) pyrope (Mg) andradite (Fe and Ca)
albite (Na and Al) and rutile (Ti) were used as standards
Ferric iron in minerals was determined based on the
scheme of Droop (1987)
Whole-rock major and trace elementsOn the basis of careful petrographic observations we
selected 18 samples for whole-rock major and trace
element analyses The whole-rock major element
oxides were analyzed using a Leeman Prodigy induct-
ively coupled plasma optical emission spectroscopy
system (ICP-OES) at the China University of
Geosciences Beijing (CUGB) The analytical precisions(1r) for most major elements based on master stand-
ards GSR-1 GSR-3 GSR-5 (national geological stand-
ard reference materials of China) and USGS AGV-2 are
better than 1 except for TiO2 (15) and P2O5
(20) Loss on ignition (LOI) was determined by plac-
ing 1 g of sample powder in a furnace at 1000C for sev-eral hours before being cooled in a desiccator and
reweighed (Song et al 2010)
The trace element compositions of Haolaoluchang
volcanic samples were determined by inductively
coupled plasma mass spectrometry (ICP-MS) using an
Agilent-7500a quadrupole system in the Institute of
Earth Science CUGB About 40 mg power for each sam-ple was dissolved in a distilled acid mixture (11 HNO3ndash
HF) in a Teflon digesting vessel and heated on a hot-
plate at 185C for 48 h using high-pressure bombs for
digestionndashdissolution The sample was then evaporated
to incipient dryness refluxed with 1 ml 6N HNO3 and
heated again to incipient dryness The sample was
again dissolved in 2 ml of 3N HNO3 in a high-pressurebomb at 165C for a further 24 h to ensure complete dis-
solution Such digested samples were finally diluted
with Milli-Q water to a dilution factor of 2000 in 2
HNO3 solution for analysis Master standards (GSR-1
GSR-3 GSR-5 and USGS AGV-2) were used to monitor
the analytical accuracy and precision Analytical accur-acy as indicated by a relative difference between meas-
ured and recommended values is better than 5 for
most elements and 10ndash15 for Cu Zn Gd and Ta
Zircon preparation and UndashThndashPb analysisThe samples were crushed and sieved to 300 lm forthe first separation and then to 100 lm for the second
separation Zircons were separated by combining mag-
netic and heavy liquid methods before finally hand-
picking under a binocular microscope Zircon grains to-
gether with zircon standard 91500 were mounted in
epoxy mounts which were then polished to section thecrystals in half for analysis All zircons were docu-
mented with transmitted and reflected light micro-
graphs as well as cathodoluminescence (CL) images to
reveal their internal structures and the mount was
vacuum-coated with high-purity gold prior to secondary
ion mass spectrometry (SIMS) analysis The CL images
were obtained on an FEI Philips XL30 SFEG SEM with2 min scanning time at conditions of 15 kV and 20 nA at
Peking University
Measurements of U Th and Pb were conducted
using the Cameca IMS-1280 SIMS system at the
Institute of Geology and Geophysics Chinese Academy
of Sciences in Beijing UndashThndashPb ratios and absoluteabundances were determined relative to the standard
zircon 91500 (Wiedenbeck et al 1995) analyses of
which were interspersed with those of unknown grains
using operating and data processing procedures similar
to those described by Li et al (2009) A long-term uncer-
tainty of 15 (1RSD) for 206Pb238U measurements of
the standard zircons was propagated to the unknowns(Li et al 2010) despite the fact that the measured206Pb238U error in a specific session is generally around
1 (1RSD) or less Measured compositions were cor-
rected for common Pb using non-radiogenic 204Pb
Corrections are sufficiently small to be insensitive to the
choice of common Pb composition and an average ofthe present-day crustal composition (Stacey amp Kramers
1975) was used for the common Pb assuming that the
2046 Journal of Petrology 2018 Vol 59 No 11
Dow
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icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le1
Re
pre
sen
tati
ve
an
aly
ses
of
ga
rne
tin
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(HK
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
26
-11
6K
L2
6-2
16
KL
27
-11
6K
L2
7-2
16
KL
27
-31
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
7A
-31
4k2
-11
4k2
-21
4k2
-31
4k4
-11
4k4
-21
4k4
-31
4k5
-11
4k5
-21
4k5
-3L
oca
tio
n
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
23
76
63
87
33
79
33
83
23
86
33
88
13
84
53
81
83
83
93
84
53
89
43
67
73
79
33
89
33
84
83
84
23
91
63
88
23
92
9T
iO2
01
201
100
701
001
100
100
800
300
700
500
501
401
001
300
701
600
001
100
7A
l 2O
32
10
62
12
82
08
72
17
12
17
12
13
62
14
72
15
02
13
12
14
22
22
02
11
92
22
32
18
32
15
12
17
32
22
32
23
12
24
6C
r 2O
300
100
700
000
100
000
300
400
100
000
400
200
000
600
000
000
200
400
100
1F
eO
265
52
22
42
58
92
62
12
18
92
20
92
22
82
31
72
31
42
28
82
54
82
58
62
59
62
59
62
87
02
80
62
57
12
36
92
46
3M
nO
05
304
005
003
604
804
005
005
104
704
202
705
407
604
505
603
500
908
500
5N
iO00
500
000
001
000
000
300
000
500
000
000
000
400
000
400
200
400
300
000
0M
gO
50
070
271
471
970
669
568
367
368
067
033
420
420
843
323
431
337
235
338
0C
aO
82
895
765
562
798
799
991
289
193
896
51
10
91
20
51
21
995
61
00
699
11
00
41
20
91
13
3N
a2O
00
600
600
400
500
500
500
000
800
300
100
000
100
000
600
000
000
500
000
0K
2O
00
100
000
000
100
000
000
000
300
000
100
000
000
000
100
000
300
000
000
0T
ota
l9
93
39
94
89
91
003
29
98
997
39
87
79
92
995
99
96
21
014
986
21
013
11
012
91
017
41
018
51
010
61
014
11
016
4C
alc
ula
tio
nu
sin
g1
2o
xy
ge
nS
i29
62
29
87
29
64
29
52
29
66
29
85
29
91
29
61
29
66
29
69
30
08
29
44
29
53
30
03
29
99
29
76
30
30
29
88
30
15
Ti
00
07
00
06
00
04
00
06
00
06
00
01
00
05
00
02
00
04
00
03
00
03
00
08
00
06
00
08
00
04
00
09
00
00
00
06
00
04
Al
19
52
19
34
19
22
19
71
19
64
19
36
19
68
19
65
19
40
19
49
20
21
19
99
20
39
19
85
19
76
19
84
20
27
20
23
20
31
Cr
00
01
00
04
00
00
00
01
00
00
00
02
00
02
00
01
00
00
00
02
00
01
00
00
00
04
00
00
00
00
00
01
00
02
00
01
00
01
Fe
3thorn
01
20
00
83
01
49
01
20
00
99
00
98
00
39
01
25
01
24
01
07
00
00
00
98
00
39
00
04
00
17
00
47
00
00
00
00
00
00
Fe
2thorn
16
26
13
52
15
42
15
68
13
06
13
23
14
10
13
78
13
71
13
70
16
46
16
33
16
50
16
71
18
53
17
70
16
64
15
25
15
80
Mn
00
35
00
26
00
33
00
24
00
31
00
26
00
33
00
34
00
31
00
28
00
18
00
37
00
50
00
29
00
37
00
23
00
06
00
55
00
03
Ni
00
03
00
00
00
00
00
06
00
00
00
02
00
00
00
03
00
00
00
00
00
00
00
03
00
00
00
02
00
01
00
02
00
02
00
00
00
00
Mg
05
86
08
07
08
32
08
26
08
08
07
97
07
92
07
78
07
83
07
71
03
85
02
43
02
41
04
98
02
72
03
61
04
29
04
05
04
35
Ca
06
98
07
91
05
48
05
18
08
12
08
23
07
60
07
40
07
76
07
98
09
18
10
33
10
17
07
90
08
40
08
22
08
32
09
97
09
31
Na
00
09
00
09
00
06
00
07
00
07
00
07
00
00
00
12
00
04
00
01
00
00
00
02
00
00
00
09
00
00
00
00
00
08
00
00
00
00
K00
01
00
00
00
00
00
01
00
00
00
00
00
00
00
03
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
03
00
00
00
00
00
00
Su
m8
88
88
88
88
88
88
88
88
88
Py
rop
e1
91
32
63
92
67
92
70
32
64
42
59
82
61
02
54
72
53
92
50
91
29
780
080
51
66
490
11
19
51
46
41
35
81
47
4A
lm5
69
64
69
05
44
85
52
64
59
84
63
24
77
64
91
94
84
54
80
55
54
95
68
65
63
65
59
76
19
56
01
05
67
65
11
35
35
8S
pe
ss11
508
610
707
710
208
510
911
010
008
906
012
016
709
812
307
602
018
601
1U
va
ro00
302
200
000
300
000
901
200
300
001
300
600
001
800
000
000
601
200
300
3G
ross
ula
r2
27
32
56
31
76
61
69
12
65
62
67
52
49
22
42
02
51
62
58
43
08
83
39
43
37
32
64
12
78
22
71
32
82
83
34
03
15
5
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
cea
fte
rD
roo
p(1
98
7)
Journal of Petrology 2018 Vol 59 No 11 2047
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le2
Re
pre
sen
tati
ve
an
aly
ses
of
om
ph
aci
tein
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(KH
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
13
-31
6K
L2
7-1
16
KL
27
-21
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
6-1
16
KL
26
-21
4k2
-11
4k4
-11
4k4
-21
4k4
-31
4k4
-5k4
-51
k4-61
k4-75
XR
1-1
XR
2-1
Lo
cati
on
H
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
25
60
55
54
05
53
35
53
15
53
75
53
15
53
95
54
45
52
45
48
55
17
35
24
25
48
85
53
15
45
65
26
25
27
95
46
95
39
9T
iO2
00
901
701
001
000
501
402
101
101
601
300
600
700
700
901
200
601
001
401
6A
l 2O
393
298
996
91
00
194
998
390
891
190
557
147
245
654
952
153
731
347
278
081
0C
r 2O
300
400
000
000
000
300
000
000
000
600
700
100
400
000
000
500
000
700
300
6F
eO
64
765
363
068
845
744
262
160
260
469
91
41
11
03
082
376
085
41
04
394
153
350
9M
nO
00
300
900
200
600
000
300
300
200
201
001
000
200
800
000
100
900
100
600
2N
iO00
000
500
000
600
500
000
000
000
000
000
700
000
600
600
000
000
000
600
0M
gO
73
373
571
675
292
292
091
188
388
51
15
61
05
81
03
21
03
61
06
71
06
61
14
71
07
299
81
01
0C
aO
136
01
36
91
36
71
25
01
48
51
45
11
36
61
37
51
37
81
87
31
75
11
93
01
75
11
79
01
72
92
13
31
82
81
58
01
59
4N
a2O
67
465
869
668
359
962
963
662
064
221
715
425
836
436
738
213
733
753
056
9K
2O
00
400
200
100
100
000
100
000
200
000
300
100
000
000
300
000
100
000
000
1T
ota
l9
97
29
97
69
92
49
92
89
96
19
97
41
000
59
94
99
96
21
003
51
004
59
96
10
02
21
005
31
004
21
005
994
79
91
99
91
7C
alc
ula
tio
nu
sin
g6
ox
yg
en
Si
20
16
19
93
19
95
19
95
19
82
19
72
19
78
19
93
19
81
20
09
19
37
19
49
20
02
20
08
19
84
19
53
19
47
19
77
19
43
Ti
00
02
00
05
00
03
00
03
00
01
00
04
00
06
00
03
00
04
00
04
00
02
00
02
00
02
00
02
00
03
00
02
00
03
00
04
00
04
Al
03
95
04
19
04
12
04
26
04
00
04
13
03
82
03
86
03
82
02
46
02
08
02
00
02
36
02
23
02
30
01
37
02
05
03
32
03
44
Cr
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
02
00
02
00
00
00
01
00
00
00
00
00
01
00
00
00
02
00
01
00
02
Fe
3thorn
00
37
800
44
500
79
700
56
900
47
800
70
600
90
900
54
400
91
700
00
000
26
000
82
600
14
000
15
100
62
800
52
801
34
400
77
01
53
Fe
2thorn
01
57
01
52
01
10
01
51
00
89
00
61
00
95
01
27
00
89
02
14
04
16
02
38
02
37
02
16
01
97
02
71
01
56
00
85
00
00
Mn
00
01
00
03
00
01
00
02
00
00
00
01
00
01
00
01
00
01
00
03
00
03
00
01
00
02
00
00
00
00
00
03
00
00
00
02
00
01
Ni
00
00
00
01
00
00
00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
02
00
00
00
02
00
02
00
00
00
00
00
00
00
02
00
00
Mg
03
93
03
94
03
85
04
04
04
92
04
89
04
85
04
73
04
73
06
31
05
91
05
72
05
63
05
78
05
78
06
35
05
89
05
38
05
42
Ca
05
24
05
28
05
28
04
83
05
69
05
54
05
23
05
30
05
29
07
35
07
02
07
69
06
84
06
96
06
74
08
48
07
22
06
12
06
15
Na
04
70
04
59
04
87
04
78
04
16
04
35
04
40
04
32
04
46
01
54
01
12
01
86
02
57
02
58
02
69
00
99
02
41
03
71
03
97
K00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
01
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
00
00
00
Su
m4
44
44
44
44
44
44
44
44
44
Jd
414
14
17
44
09
54
23
43
83
73
88
83
65
83
82
43
67
72
59
11
47
21
51
02
39
72
33
82
17
691
61
54
83
13
22
90
7A
e37
844
579
756
947
870
690
954
491
700
026
082
614
015
162
852
81
34
476
51
53
2W
EF
548
15
38
15
10
85
19
75
68
55
40
65
43
35
63
25
40
67
40
98
26
97
66
47
46
37
51
17
19
68
55
67
10
86
10
35
56
1
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
ce(D
roo
p1
98
7)
2048 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
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icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
2050 Journal of Petrology 2018 Vol 59 No 11
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
2052 Journal of Petrology 2018 Vol 59 No 11
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
discovered in the Kehete terrane The metapelite sam-
ples have a schistose structure with red grains of gar-
net and foliated mica in outcrop The rocks are
composed of garnet (5ndash15) muscovite (20ndash30) bio-
tite (5ndash10) quartz (35ndash45) plagioclase (10) andminor tourmaline zircon and rutile Most rutile grains
in the matrix are replaced by titanite andor ilmenite No
granitic gneiss has been found in the eclogite-bearing
high-pressure terranes The rock assemblage plus
some serpentinite massifs suggests an oceanic-type
subduction melange
Most eclogite samples in the east section of the HPndashUHP belt are fresh They show granoblastic textures with
a mineral assemblage of garnet omphacite rutile quartz
and minor phengite without obvious foliation Garnet
occurs as euhedral crystals with rare zircon and rutile
inclusions (Fig 2e and f) Coesite pseudomorphs are
observed as inclusions in garnet (Fig 2g) Most ompha-cite crystals contain densely packed oriented quartz rods
(Fig 2h) Omphacite crystals are commonly replaced by
Cpx thorn Oli symplectites and further by amphibole and ru-
tile is replaced by titanite suggesting that these eclogite
samples are overprinted by later decompression and
amphibolite-facies retrogression (Fig 2i)
ANALYTICAL METHODS
Mineral compositionsPolished thin sections were produced from representa-tive pieces of the studied samples and were examined
in detail using a petrographic microscope Mineral com-
positions were analysed using an electron probe micro-
analyzer (EPMA) (JEOL JXA-8100) at Peking University
operated at 15 kV acceleration voltage with 20 nA beam
current and 1ndash5 lm beam spot Routine analyses wereobtained by counting for 20 s at peak and 5 s on back-
ground Synthetic silica (Si) and spessartine (Mn) nat-
ural sanidine (K) pyrope (Mg) andradite (Fe and Ca)
albite (Na and Al) and rutile (Ti) were used as standards
Ferric iron in minerals was determined based on the
scheme of Droop (1987)
Whole-rock major and trace elementsOn the basis of careful petrographic observations we
selected 18 samples for whole-rock major and trace
element analyses The whole-rock major element
oxides were analyzed using a Leeman Prodigy induct-
ively coupled plasma optical emission spectroscopy
system (ICP-OES) at the China University of
Geosciences Beijing (CUGB) The analytical precisions(1r) for most major elements based on master stand-
ards GSR-1 GSR-3 GSR-5 (national geological stand-
ard reference materials of China) and USGS AGV-2 are
better than 1 except for TiO2 (15) and P2O5
(20) Loss on ignition (LOI) was determined by plac-
ing 1 g of sample powder in a furnace at 1000C for sev-eral hours before being cooled in a desiccator and
reweighed (Song et al 2010)
The trace element compositions of Haolaoluchang
volcanic samples were determined by inductively
coupled plasma mass spectrometry (ICP-MS) using an
Agilent-7500a quadrupole system in the Institute of
Earth Science CUGB About 40 mg power for each sam-ple was dissolved in a distilled acid mixture (11 HNO3ndash
HF) in a Teflon digesting vessel and heated on a hot-
plate at 185C for 48 h using high-pressure bombs for
digestionndashdissolution The sample was then evaporated
to incipient dryness refluxed with 1 ml 6N HNO3 and
heated again to incipient dryness The sample was
again dissolved in 2 ml of 3N HNO3 in a high-pressurebomb at 165C for a further 24 h to ensure complete dis-
solution Such digested samples were finally diluted
with Milli-Q water to a dilution factor of 2000 in 2
HNO3 solution for analysis Master standards (GSR-1
GSR-3 GSR-5 and USGS AGV-2) were used to monitor
the analytical accuracy and precision Analytical accur-acy as indicated by a relative difference between meas-
ured and recommended values is better than 5 for
most elements and 10ndash15 for Cu Zn Gd and Ta
Zircon preparation and UndashThndashPb analysisThe samples were crushed and sieved to 300 lm forthe first separation and then to 100 lm for the second
separation Zircons were separated by combining mag-
netic and heavy liquid methods before finally hand-
picking under a binocular microscope Zircon grains to-
gether with zircon standard 91500 were mounted in
epoxy mounts which were then polished to section thecrystals in half for analysis All zircons were docu-
mented with transmitted and reflected light micro-
graphs as well as cathodoluminescence (CL) images to
reveal their internal structures and the mount was
vacuum-coated with high-purity gold prior to secondary
ion mass spectrometry (SIMS) analysis The CL images
were obtained on an FEI Philips XL30 SFEG SEM with2 min scanning time at conditions of 15 kV and 20 nA at
Peking University
Measurements of U Th and Pb were conducted
using the Cameca IMS-1280 SIMS system at the
Institute of Geology and Geophysics Chinese Academy
of Sciences in Beijing UndashThndashPb ratios and absoluteabundances were determined relative to the standard
zircon 91500 (Wiedenbeck et al 1995) analyses of
which were interspersed with those of unknown grains
using operating and data processing procedures similar
to those described by Li et al (2009) A long-term uncer-
tainty of 15 (1RSD) for 206Pb238U measurements of
the standard zircons was propagated to the unknowns(Li et al 2010) despite the fact that the measured206Pb238U error in a specific session is generally around
1 (1RSD) or less Measured compositions were cor-
rected for common Pb using non-radiogenic 204Pb
Corrections are sufficiently small to be insensitive to the
choice of common Pb composition and an average ofthe present-day crustal composition (Stacey amp Kramers
1975) was used for the common Pb assuming that the
2046 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le1
Re
pre
sen
tati
ve
an
aly
ses
of
ga
rne
tin
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(HK
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
26
-11
6K
L2
6-2
16
KL
27
-11
6K
L2
7-2
16
KL
27
-31
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
7A
-31
4k2
-11
4k2
-21
4k2
-31
4k4
-11
4k4
-21
4k4
-31
4k5
-11
4k5
-21
4k5
-3L
oca
tio
n
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
23
76
63
87
33
79
33
83
23
86
33
88
13
84
53
81
83
83
93
84
53
89
43
67
73
79
33
89
33
84
83
84
23
91
63
88
23
92
9T
iO2
01
201
100
701
001
100
100
800
300
700
500
501
401
001
300
701
600
001
100
7A
l 2O
32
10
62
12
82
08
72
17
12
17
12
13
62
14
72
15
02
13
12
14
22
22
02
11
92
22
32
18
32
15
12
17
32
22
32
23
12
24
6C
r 2O
300
100
700
000
100
000
300
400
100
000
400
200
000
600
000
000
200
400
100
1F
eO
265
52
22
42
58
92
62
12
18
92
20
92
22
82
31
72
31
42
28
82
54
82
58
62
59
62
59
62
87
02
80
62
57
12
36
92
46
3M
nO
05
304
005
003
604
804
005
005
104
704
202
705
407
604
505
603
500
908
500
5N
iO00
500
000
001
000
000
300
000
500
000
000
000
400
000
400
200
400
300
000
0M
gO
50
070
271
471
970
669
568
367
368
067
033
420
420
843
323
431
337
235
338
0C
aO
82
895
765
562
798
799
991
289
193
896
51
10
91
20
51
21
995
61
00
699
11
00
41
20
91
13
3N
a2O
00
600
600
400
500
500
500
000
800
300
100
000
100
000
600
000
000
500
000
0K
2O
00
100
000
000
100
000
000
000
300
000
100
000
000
000
100
000
300
000
000
0T
ota
l9
93
39
94
89
91
003
29
98
997
39
87
79
92
995
99
96
21
014
986
21
013
11
012
91
017
41
018
51
010
61
014
11
016
4C
alc
ula
tio
nu
sin
g1
2o
xy
ge
nS
i29
62
29
87
29
64
29
52
29
66
29
85
29
91
29
61
29
66
29
69
30
08
29
44
29
53
30
03
29
99
29
76
30
30
29
88
30
15
Ti
00
07
00
06
00
04
00
06
00
06
00
01
00
05
00
02
00
04
00
03
00
03
00
08
00
06
00
08
00
04
00
09
00
00
00
06
00
04
Al
19
52
19
34
19
22
19
71
19
64
19
36
19
68
19
65
19
40
19
49
20
21
19
99
20
39
19
85
19
76
19
84
20
27
20
23
20
31
Cr
00
01
00
04
00
00
00
01
00
00
00
02
00
02
00
01
00
00
00
02
00
01
00
00
00
04
00
00
00
00
00
01
00
02
00
01
00
01
Fe
3thorn
01
20
00
83
01
49
01
20
00
99
00
98
00
39
01
25
01
24
01
07
00
00
00
98
00
39
00
04
00
17
00
47
00
00
00
00
00
00
Fe
2thorn
16
26
13
52
15
42
15
68
13
06
13
23
14
10
13
78
13
71
13
70
16
46
16
33
16
50
16
71
18
53
17
70
16
64
15
25
15
80
Mn
00
35
00
26
00
33
00
24
00
31
00
26
00
33
00
34
00
31
00
28
00
18
00
37
00
50
00
29
00
37
00
23
00
06
00
55
00
03
Ni
00
03
00
00
00
00
00
06
00
00
00
02
00
00
00
03
00
00
00
00
00
00
00
03
00
00
00
02
00
01
00
02
00
02
00
00
00
00
Mg
05
86
08
07
08
32
08
26
08
08
07
97
07
92
07
78
07
83
07
71
03
85
02
43
02
41
04
98
02
72
03
61
04
29
04
05
04
35
Ca
06
98
07
91
05
48
05
18
08
12
08
23
07
60
07
40
07
76
07
98
09
18
10
33
10
17
07
90
08
40
08
22
08
32
09
97
09
31
Na
00
09
00
09
00
06
00
07
00
07
00
07
00
00
00
12
00
04
00
01
00
00
00
02
00
00
00
09
00
00
00
00
00
08
00
00
00
00
K00
01
00
00
00
00
00
01
00
00
00
00
00
00
00
03
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
03
00
00
00
00
00
00
Su
m8
88
88
88
88
88
88
88
88
88
Py
rop
e1
91
32
63
92
67
92
70
32
64
42
59
82
61
02
54
72
53
92
50
91
29
780
080
51
66
490
11
19
51
46
41
35
81
47
4A
lm5
69
64
69
05
44
85
52
64
59
84
63
24
77
64
91
94
84
54
80
55
54
95
68
65
63
65
59
76
19
56
01
05
67
65
11
35
35
8S
pe
ss11
508
610
707
710
208
510
911
010
008
906
012
016
709
812
307
602
018
601
1U
va
ro00
302
200
000
300
000
901
200
300
001
300
600
001
800
000
000
601
200
300
3G
ross
ula
r2
27
32
56
31
76
61
69
12
65
62
67
52
49
22
42
02
51
62
58
43
08
83
39
43
37
32
64
12
78
22
71
32
82
83
34
03
15
5
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
cea
fte
rD
roo
p(1
98
7)
Journal of Petrology 2018 Vol 59 No 11 2047
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le2
Re
pre
sen
tati
ve
an
aly
ses
of
om
ph
aci
tein
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(KH
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
13
-31
6K
L2
7-1
16
KL
27
-21
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
6-1
16
KL
26
-21
4k2
-11
4k4
-11
4k4
-21
4k4
-31
4k4
-5k4
-51
k4-61
k4-75
XR
1-1
XR
2-1
Lo
cati
on
H
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
25
60
55
54
05
53
35
53
15
53
75
53
15
53
95
54
45
52
45
48
55
17
35
24
25
48
85
53
15
45
65
26
25
27
95
46
95
39
9T
iO2
00
901
701
001
000
501
402
101
101
601
300
600
700
700
901
200
601
001
401
6A
l 2O
393
298
996
91
00
194
998
390
891
190
557
147
245
654
952
153
731
347
278
081
0C
r 2O
300
400
000
000
000
300
000
000
000
600
700
100
400
000
000
500
000
700
300
6F
eO
64
765
363
068
845
744
262
160
260
469
91
41
11
03
082
376
085
41
04
394
153
350
9M
nO
00
300
900
200
600
000
300
300
200
201
001
000
200
800
000
100
900
100
600
2N
iO00
000
500
000
600
500
000
000
000
000
000
700
000
600
600
000
000
000
600
0M
gO
73
373
571
675
292
292
091
188
388
51
15
61
05
81
03
21
03
61
06
71
06
61
14
71
07
299
81
01
0C
aO
136
01
36
91
36
71
25
01
48
51
45
11
36
61
37
51
37
81
87
31
75
11
93
01
75
11
79
01
72
92
13
31
82
81
58
01
59
4N
a2O
67
465
869
668
359
962
963
662
064
221
715
425
836
436
738
213
733
753
056
9K
2O
00
400
200
100
100
000
100
000
200
000
300
100
000
000
300
000
100
000
000
1T
ota
l9
97
29
97
69
92
49
92
89
96
19
97
41
000
59
94
99
96
21
003
51
004
59
96
10
02
21
005
31
004
21
005
994
79
91
99
91
7C
alc
ula
tio
nu
sin
g6
ox
yg
en
Si
20
16
19
93
19
95
19
95
19
82
19
72
19
78
19
93
19
81
20
09
19
37
19
49
20
02
20
08
19
84
19
53
19
47
19
77
19
43
Ti
00
02
00
05
00
03
00
03
00
01
00
04
00
06
00
03
00
04
00
04
00
02
00
02
00
02
00
02
00
03
00
02
00
03
00
04
00
04
Al
03
95
04
19
04
12
04
26
04
00
04
13
03
82
03
86
03
82
02
46
02
08
02
00
02
36
02
23
02
30
01
37
02
05
03
32
03
44
Cr
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
02
00
02
00
00
00
01
00
00
00
00
00
01
00
00
00
02
00
01
00
02
Fe
3thorn
00
37
800
44
500
79
700
56
900
47
800
70
600
90
900
54
400
91
700
00
000
26
000
82
600
14
000
15
100
62
800
52
801
34
400
77
01
53
Fe
2thorn
01
57
01
52
01
10
01
51
00
89
00
61
00
95
01
27
00
89
02
14
04
16
02
38
02
37
02
16
01
97
02
71
01
56
00
85
00
00
Mn
00
01
00
03
00
01
00
02
00
00
00
01
00
01
00
01
00
01
00
03
00
03
00
01
00
02
00
00
00
00
00
03
00
00
00
02
00
01
Ni
00
00
00
01
00
00
00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
02
00
00
00
02
00
02
00
00
00
00
00
00
00
02
00
00
Mg
03
93
03
94
03
85
04
04
04
92
04
89
04
85
04
73
04
73
06
31
05
91
05
72
05
63
05
78
05
78
06
35
05
89
05
38
05
42
Ca
05
24
05
28
05
28
04
83
05
69
05
54
05
23
05
30
05
29
07
35
07
02
07
69
06
84
06
96
06
74
08
48
07
22
06
12
06
15
Na
04
70
04
59
04
87
04
78
04
16
04
35
04
40
04
32
04
46
01
54
01
12
01
86
02
57
02
58
02
69
00
99
02
41
03
71
03
97
K00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
01
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
00
00
00
Su
m4
44
44
44
44
44
44
44
44
44
Jd
414
14
17
44
09
54
23
43
83
73
88
83
65
83
82
43
67
72
59
11
47
21
51
02
39
72
33
82
17
691
61
54
83
13
22
90
7A
e37
844
579
756
947
870
690
954
491
700
026
082
614
015
162
852
81
34
476
51
53
2W
EF
548
15
38
15
10
85
19
75
68
55
40
65
43
35
63
25
40
67
40
98
26
97
66
47
46
37
51
17
19
68
55
67
10
86
10
35
56
1
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
ce(D
roo
p1
98
7)
2048 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
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icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
2052 Journal of Petrology 2018 Vol 59 No 11
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
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Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le1
Re
pre
sen
tati
ve
an
aly
ses
of
ga
rne
tin
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(HK
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
26
-11
6K
L2
6-2
16
KL
27
-11
6K
L2
7-2
16
KL
27
-31
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
7A
-31
4k2
-11
4k2
-21
4k2
-31
4k4
-11
4k4
-21
4k4
-31
4k5
-11
4k5
-21
4k5
-3L
oca
tio
n
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
23
76
63
87
33
79
33
83
23
86
33
88
13
84
53
81
83
83
93
84
53
89
43
67
73
79
33
89
33
84
83
84
23
91
63
88
23
92
9T
iO2
01
201
100
701
001
100
100
800
300
700
500
501
401
001
300
701
600
001
100
7A
l 2O
32
10
62
12
82
08
72
17
12
17
12
13
62
14
72
15
02
13
12
14
22
22
02
11
92
22
32
18
32
15
12
17
32
22
32
23
12
24
6C
r 2O
300
100
700
000
100
000
300
400
100
000
400
200
000
600
000
000
200
400
100
1F
eO
265
52
22
42
58
92
62
12
18
92
20
92
22
82
31
72
31
42
28
82
54
82
58
62
59
62
59
62
87
02
80
62
57
12
36
92
46
3M
nO
05
304
005
003
604
804
005
005
104
704
202
705
407
604
505
603
500
908
500
5N
iO00
500
000
001
000
000
300
000
500
000
000
000
400
000
400
200
400
300
000
0M
gO
50
070
271
471
970
669
568
367
368
067
033
420
420
843
323
431
337
235
338
0C
aO
82
895
765
562
798
799
991
289
193
896
51
10
91
20
51
21
995
61
00
699
11
00
41
20
91
13
3N
a2O
00
600
600
400
500
500
500
000
800
300
100
000
100
000
600
000
000
500
000
0K
2O
00
100
000
000
100
000
000
000
300
000
100
000
000
000
100
000
300
000
000
0T
ota
l9
93
39
94
89
91
003
29
98
997
39
87
79
92
995
99
96
21
014
986
21
013
11
012
91
017
41
018
51
010
61
014
11
016
4C
alc
ula
tio
nu
sin
g1
2o
xy
ge
nS
i29
62
29
87
29
64
29
52
29
66
29
85
29
91
29
61
29
66
29
69
30
08
29
44
29
53
30
03
29
99
29
76
30
30
29
88
30
15
Ti
00
07
00
06
00
04
00
06
00
06
00
01
00
05
00
02
00
04
00
03
00
03
00
08
00
06
00
08
00
04
00
09
00
00
00
06
00
04
Al
19
52
19
34
19
22
19
71
19
64
19
36
19
68
19
65
19
40
19
49
20
21
19
99
20
39
19
85
19
76
19
84
20
27
20
23
20
31
Cr
00
01
00
04
00
00
00
01
00
00
00
02
00
02
00
01
00
00
00
02
00
01
00
00
00
04
00
00
00
00
00
01
00
02
00
01
00
01
Fe
3thorn
01
20
00
83
01
49
01
20
00
99
00
98
00
39
01
25
01
24
01
07
00
00
00
98
00
39
00
04
00
17
00
47
00
00
00
00
00
00
Fe
2thorn
16
26
13
52
15
42
15
68
13
06
13
23
14
10
13
78
13
71
13
70
16
46
16
33
16
50
16
71
18
53
17
70
16
64
15
25
15
80
Mn
00
35
00
26
00
33
00
24
00
31
00
26
00
33
00
34
00
31
00
28
00
18
00
37
00
50
00
29
00
37
00
23
00
06
00
55
00
03
Ni
00
03
00
00
00
00
00
06
00
00
00
02
00
00
00
03
00
00
00
00
00
00
00
03
00
00
00
02
00
01
00
02
00
02
00
00
00
00
Mg
05
86
08
07
08
32
08
26
08
08
07
97
07
92
07
78
07
83
07
71
03
85
02
43
02
41
04
98
02
72
03
61
04
29
04
05
04
35
Ca
06
98
07
91
05
48
05
18
08
12
08
23
07
60
07
40
07
76
07
98
09
18
10
33
10
17
07
90
08
40
08
22
08
32
09
97
09
31
Na
00
09
00
09
00
06
00
07
00
07
00
07
00
00
00
12
00
04
00
01
00
00
00
02
00
00
00
09
00
00
00
00
00
08
00
00
00
00
K00
01
00
00
00
00
00
01
00
00
00
00
00
00
00
03
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
03
00
00
00
00
00
00
Su
m8
88
88
88
88
88
88
88
88
88
Py
rop
e1
91
32
63
92
67
92
70
32
64
42
59
82
61
02
54
72
53
92
50
91
29
780
080
51
66
490
11
19
51
46
41
35
81
47
4A
lm5
69
64
69
05
44
85
52
64
59
84
63
24
77
64
91
94
84
54
80
55
54
95
68
65
63
65
59
76
19
56
01
05
67
65
11
35
35
8S
pe
ss11
508
610
707
710
208
510
911
010
008
906
012
016
709
812
307
602
018
601
1U
va
ro00
302
200
000
300
000
901
200
300
001
300
600
001
800
000
000
601
200
300
3G
ross
ula
r2
27
32
56
31
76
61
69
12
65
62
67
52
49
22
42
02
51
62
58
43
08
83
39
43
37
32
64
12
78
22
71
32
82
83
34
03
15
5
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
cea
fte
rD
roo
p(1
98
7)
Journal of Petrology 2018 Vol 59 No 11 2047
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le2
Re
pre
sen
tati
ve
an
aly
ses
of
om
ph
aci
tein
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(KH
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
13
-31
6K
L2
7-1
16
KL
27
-21
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
6-1
16
KL
26
-21
4k2
-11
4k4
-11
4k4
-21
4k4
-31
4k4
-5k4
-51
k4-61
k4-75
XR
1-1
XR
2-1
Lo
cati
on
H
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
25
60
55
54
05
53
35
53
15
53
75
53
15
53
95
54
45
52
45
48
55
17
35
24
25
48
85
53
15
45
65
26
25
27
95
46
95
39
9T
iO2
00
901
701
001
000
501
402
101
101
601
300
600
700
700
901
200
601
001
401
6A
l 2O
393
298
996
91
00
194
998
390
891
190
557
147
245
654
952
153
731
347
278
081
0C
r 2O
300
400
000
000
000
300
000
000
000
600
700
100
400
000
000
500
000
700
300
6F
eO
64
765
363
068
845
744
262
160
260
469
91
41
11
03
082
376
085
41
04
394
153
350
9M
nO
00
300
900
200
600
000
300
300
200
201
001
000
200
800
000
100
900
100
600
2N
iO00
000
500
000
600
500
000
000
000
000
000
700
000
600
600
000
000
000
600
0M
gO
73
373
571
675
292
292
091
188
388
51
15
61
05
81
03
21
03
61
06
71
06
61
14
71
07
299
81
01
0C
aO
136
01
36
91
36
71
25
01
48
51
45
11
36
61
37
51
37
81
87
31
75
11
93
01
75
11
79
01
72
92
13
31
82
81
58
01
59
4N
a2O
67
465
869
668
359
962
963
662
064
221
715
425
836
436
738
213
733
753
056
9K
2O
00
400
200
100
100
000
100
000
200
000
300
100
000
000
300
000
100
000
000
1T
ota
l9
97
29
97
69
92
49
92
89
96
19
97
41
000
59
94
99
96
21
003
51
004
59
96
10
02
21
005
31
004
21
005
994
79
91
99
91
7C
alc
ula
tio
nu
sin
g6
ox
yg
en
Si
20
16
19
93
19
95
19
95
19
82
19
72
19
78
19
93
19
81
20
09
19
37
19
49
20
02
20
08
19
84
19
53
19
47
19
77
19
43
Ti
00
02
00
05
00
03
00
03
00
01
00
04
00
06
00
03
00
04
00
04
00
02
00
02
00
02
00
02
00
03
00
02
00
03
00
04
00
04
Al
03
95
04
19
04
12
04
26
04
00
04
13
03
82
03
86
03
82
02
46
02
08
02
00
02
36
02
23
02
30
01
37
02
05
03
32
03
44
Cr
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
02
00
02
00
00
00
01
00
00
00
00
00
01
00
00
00
02
00
01
00
02
Fe
3thorn
00
37
800
44
500
79
700
56
900
47
800
70
600
90
900
54
400
91
700
00
000
26
000
82
600
14
000
15
100
62
800
52
801
34
400
77
01
53
Fe
2thorn
01
57
01
52
01
10
01
51
00
89
00
61
00
95
01
27
00
89
02
14
04
16
02
38
02
37
02
16
01
97
02
71
01
56
00
85
00
00
Mn
00
01
00
03
00
01
00
02
00
00
00
01
00
01
00
01
00
01
00
03
00
03
00
01
00
02
00
00
00
00
00
03
00
00
00
02
00
01
Ni
00
00
00
01
00
00
00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
02
00
00
00
02
00
02
00
00
00
00
00
00
00
02
00
00
Mg
03
93
03
94
03
85
04
04
04
92
04
89
04
85
04
73
04
73
06
31
05
91
05
72
05
63
05
78
05
78
06
35
05
89
05
38
05
42
Ca
05
24
05
28
05
28
04
83
05
69
05
54
05
23
05
30
05
29
07
35
07
02
07
69
06
84
06
96
06
74
08
48
07
22
06
12
06
15
Na
04
70
04
59
04
87
04
78
04
16
04
35
04
40
04
32
04
46
01
54
01
12
01
86
02
57
02
58
02
69
00
99
02
41
03
71
03
97
K00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
01
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
00
00
00
Su
m4
44
44
44
44
44
44
44
44
44
Jd
414
14
17
44
09
54
23
43
83
73
88
83
65
83
82
43
67
72
59
11
47
21
51
02
39
72
33
82
17
691
61
54
83
13
22
90
7A
e37
844
579
756
947
870
690
954
491
700
026
082
614
015
162
852
81
34
476
51
53
2W
EF
548
15
38
15
10
85
19
75
68
55
40
65
43
35
63
25
40
67
40
98
26
97
66
47
46
37
51
17
19
68
55
67
10
86
10
35
56
1
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
ce(D
roo
p1
98
7)
2048 Journal of Petrology 2018 Vol 59 No 11
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common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
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Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
2052 Journal of Petrology 2018 Vol 59 No 11
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
2054 Journal of Petrology 2018 Vol 59 No 11
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
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Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le2
Re
pre
sen
tati
ve
an
aly
ses
of
om
ph
aci
tein
ecl
og
ite
sfr
om
Ke
he
teT
era
ne
(KH
T)
an
dX
iari
ha
mu
Te
rra
ne
E
ast
Ku
nlu
nO
rog
en
Sa
mp
le
16
KL
13
-11
6K
L1
3-2
16
KL
13
-31
6K
L2
7-1
16
KL
27
-21
6K
L2
7A
-11
6K
L2
7A
-21
6K
L2
6-1
16
KL
26
-21
4k2
-11
4k4
-11
4k4
-21
4k4
-31
4k4
-5k4
-51
k4-61
k4-75
XR
1-1
XR
2-1
Lo
cati
on
H
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
HK
TH
KT
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
XR
HM
SiO
25
60
55
54
05
53
35
53
15
53
75
53
15
53
95
54
45
52
45
48
55
17
35
24
25
48
85
53
15
45
65
26
25
27
95
46
95
39
9T
iO2
00
901
701
001
000
501
402
101
101
601
300
600
700
700
901
200
601
001
401
6A
l 2O
393
298
996
91
00
194
998
390
891
190
557
147
245
654
952
153
731
347
278
081
0C
r 2O
300
400
000
000
000
300
000
000
000
600
700
100
400
000
000
500
000
700
300
6F
eO
64
765
363
068
845
744
262
160
260
469
91
41
11
03
082
376
085
41
04
394
153
350
9M
nO
00
300
900
200
600
000
300
300
200
201
001
000
200
800
000
100
900
100
600
2N
iO00
000
500
000
600
500
000
000
000
000
000
700
000
600
600
000
000
000
600
0M
gO
73
373
571
675
292
292
091
188
388
51
15
61
05
81
03
21
03
61
06
71
06
61
14
71
07
299
81
01
0C
aO
136
01
36
91
36
71
25
01
48
51
45
11
36
61
37
51
37
81
87
31
75
11
93
01
75
11
79
01
72
92
13
31
82
81
58
01
59
4N
a2O
67
465
869
668
359
962
963
662
064
221
715
425
836
436
738
213
733
753
056
9K
2O
00
400
200
100
100
000
100
000
200
000
300
100
000
000
300
000
100
000
000
1T
ota
l9
97
29
97
69
92
49
92
89
96
19
97
41
000
59
94
99
96
21
003
51
004
59
96
10
02
21
005
31
004
21
005
994
79
91
99
91
7C
alc
ula
tio
nu
sin
g6
ox
yg
en
Si
20
16
19
93
19
95
19
95
19
82
19
72
19
78
19
93
19
81
20
09
19
37
19
49
20
02
20
08
19
84
19
53
19
47
19
77
19
43
Ti
00
02
00
05
00
03
00
03
00
01
00
04
00
06
00
03
00
04
00
04
00
02
00
02
00
02
00
02
00
03
00
02
00
03
00
04
00
04
Al
03
95
04
19
04
12
04
26
04
00
04
13
03
82
03
86
03
82
02
46
02
08
02
00
02
36
02
23
02
30
01
37
02
05
03
32
03
44
Cr
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
02
00
02
00
00
00
01
00
00
00
00
00
01
00
00
00
02
00
01
00
02
Fe
3thorn
00
37
800
44
500
79
700
56
900
47
800
70
600
90
900
54
400
91
700
00
000
26
000
82
600
14
000
15
100
62
800
52
801
34
400
77
01
53
Fe
2thorn
01
57
01
52
01
10
01
51
00
89
00
61
00
95
01
27
00
89
02
14
04
16
02
38
02
37
02
16
01
97
02
71
01
56
00
85
00
00
Mn
00
01
00
03
00
01
00
02
00
00
00
01
00
01
00
01
00
01
00
03
00
03
00
01
00
02
00
00
00
00
00
03
00
00
00
02
00
01
Ni
00
00
00
01
00
00
00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
02
00
00
00
02
00
02
00
00
00
00
00
00
00
02
00
00
Mg
03
93
03
94
03
85
04
04
04
92
04
89
04
85
04
73
04
73
06
31
05
91
05
72
05
63
05
78
05
78
06
35
05
89
05
38
05
42
Ca
05
24
05
28
05
28
04
83
05
69
05
54
05
23
05
30
05
29
07
35
07
02
07
69
06
84
06
96
06
74
08
48
07
22
06
12
06
15
Na
04
70
04
59
04
87
04
78
04
16
04
35
04
40
04
32
04
46
01
54
01
12
01
86
02
57
02
58
02
69
00
99
02
41
03
71
03
97
K00
02
00
01
00
00
00
00
00
00
00
00
00
00
00
01
00
00
00
01
00
00
00
00
00
00
00
01
00
00
00
00
00
00
00
00
00
00
Su
m4
44
44
44
44
44
44
44
44
44
Jd
414
14
17
44
09
54
23
43
83
73
88
83
65
83
82
43
67
72
59
11
47
21
51
02
39
72
33
82
17
691
61
54
83
13
22
90
7A
e37
844
579
756
947
870
690
954
491
700
026
082
614
015
162
852
81
34
476
51
53
2W
EF
548
15
38
15
10
85
19
75
68
55
40
65
43
35
63
25
40
67
40
98
26
97
66
47
46
37
51
17
19
68
55
67
10
86
10
35
56
1
Fe
3thorn
ing
arn
et
an
dcl
ino
py
rox
en
ew
as
calc
ula
ted
by
cha
rge
ba
lan
ce(D
roo
p1
98
7)
2048 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
2052 Journal of Petrology 2018 Vol 59 No 11
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
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Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
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common Pb is largely surface contamination introduced
during sample preparation Uncertainties on individual
analyses in data tables are reported at a 1r level mean
ages for pooled UPb (and PbPb) analyses are quoted
with a 95 confidence interval Data reduction was
carried out using the IsoplotEx v 249 program
(Ludwig 2003)
Measurements of UndashPb in zircons by laser ablation
(LA)-ICP-MS were carried out on an Agilent-7500a quad-
rupole ICP-MS system coupled with a New Wave SSUP193 laser sampler at the China University of
Geosciences Beijing Laser spot size of 36 lm laser en-
ergy density of 85 J cmndash2 and a repetition rate of 10 Hz
were applied for analysis National Institute of
Standards and Technology 610 glass and zircon stand-
ard 91500 (Wiedenbeck et al 1995) were used as exter-
nal standards Si as an internal standard and zirconstandard Qinghu zircon as the secondary standard The
software GLITTER (ver 44 Macquarie University) was
used to process the isotopic ratios and element concen-
trations of zircons The common lead correction was
made following Andersen (2002) Age calculations and
plots of concordia diagrams were made using IsoplotEx v 30 program (Ludwig 2003) Analytical details
have been described by Song et al (2010)
MINERAL AND WHOLE-ROCK CHEMISTRY
Chemical compositions of representative metamorphic
minerals are listed in Tables 1ndash3 Garnets in eclogites
from the three eclogite terranes show varying composi-tions (Fig 3a) Eclogitic garnets in the Kehete terrrane
are homogeneous in composition whereas garnets in
eclogites from the Xiarihamu terrane display weak
Table 3 Representative analyses of phengite in eclogites fromKehete Terane East Kunlun Orogen
Sample 16KL13-1 16KL27-1 16KL27-1 16KL27-1 16KL27A-1
SiO2 5596 5342 5248 5324 5465TiO2 094 069 067 073 068Al2O3 2488 2699 2778 2804 2611Cr2O3 000 007 002 006 000FeO 163 200 197 174 178MnO 002 003 001 000 001NiO 002 000 001 002 002MgO 476 395 314 352 416CaO 000 002 002 003 001Na2O 012 036 031 061 038K2O 860 924 895 802 872Total 9693 9676 9637 9601 9652Calculation using 12 oxygenSi 3591 3466 3447 3452 3533Ti 0045 0034 0033 0036 0033Al 1882 2064 2150 2142 1989Cr 0000 0004 0001 0003 0000Fe 0087 0109 0108 0094 0096Mn 0001 0002 0001 0000 0001Ni 0001 0000 0001 0001 0001Mg 0455 0382 0307 0340 0401Ca 0000 0001 0001 0002 0001Na 0015 0045 0039 0077 0048K 0704 0765 0750 0663 0719Sum 6782 6871 6839 6810 6822
Fig 3 Diagrams showing compositional variation of garnet (a) clinopyroxene (b) and amphibole (c) from the East Kunlun eclogite belt
Journal of Petrology 2018 Vol 59 No 11 2049
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
2050 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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Tab
le4
Re
pre
sen
tati
ve
an
aly
ses
of
am
ph
ibo
lein
ecl
og
ite
sfr
om
Ke
he
te(K
HT
)a
nd
Xia
rih
am
u(X
RH
M)
terr
an
es
Ea
stK
un
lun
Oro
ge
n
Sa
mp
le
16
KL
02
16
KL
09
16
KL
10
-11
6K
L1
0-2
16
KL
-8-1
16
KL
04
-11
6K
L0
4-2
16
KL
05
-11
6K
L0
5-2
16
KL
11
-11
6K
L1
1-2
14
k2-1
14
k2-2
14
k2-3
14
k2-4
14
k5-1
14
k5-2
k5-2
4L
oca
tio
n
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TK
HT
KH
TX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
MX
RH
M
SiO
24
98
15
08
95
26
05
30
64
95
25
01
34
89
75
16
55
17
25
01
94
73
65
07
55
21
44
29
74
81
94
98
65
34
54
27
9T
iO2
01
301
301
400
201
401
602
801
402
601
401
502
504
401
602
802
400
602
9A
l 2O
373
161
814
814
773
365
578
962
162
364
883
367
855
91
27
589
081
235
01
50
2C
r 2O
301
500
500
000
000
000
100
600
300
800
400
200
000
500
200
200
100
000
8F
eO
108
21
07
01
69
51
75
31
16
61
14
21
27
282
981
81
23
01
48
51
14
91
06
61
75
71
33
21
06
81
18
51
33
9M
nO
00
500
004
503
301
401
000
700
400
900
900
600
700
900
000
601
000
500
7N
iO00
000
000
300
000
000
300
900
800
000
200
000
600
600
500
001
201
200
2M
gO
152
41
53
21
23
61
23
01
50
51
50
31
31
21
72
71
71
11
57
71
25
81
50
11
56
81
01
41
45
71
54
21
62
41
08
0C
aO
114
51
21
71
23
71
22
11
14
91
21
51
17
51
25
31
26
21
01
11
17
01
22
91
24
81
12
01
05
81
20
61
16
61
22
1N
a2O
09
607
601
001
109
608
209
808
307
907
711
210
307
523
115
309
304
717
1K
2O
01
302
200
300
701
801
601
900
901
300
701
301
500
900
602
101
900
703
4T
ota
l9
60
59
64
29
65
19
71
09
64
79
65
79
61
29
71
59
72
19
59
79
63
09
78
89
80
29
72
39
76
69
77
39
74
79
67
1S
i72
51
73
77
78
35
78
60
72
15
72
94
72
03
73
52
73
55
73
25
70
45
72
86
74
28
64
65
69
96
71
45
76
63
63
50
Ti
00
14
00
14
00
16
00
02
00
15
00
18
00
31
00
15
00
28
00
15
00
17
00
27
00
47
00
18
00
31
00
26
00
06
00
32
AlIV
07
49
06
23
01
65
01
40
07
85
07
06
07
97
06
48
06
45
06
75
09
55
07
14
05
72
15
35
10
04
08
55
03
37
16
50
AlV
I05
05
04
33
00
95
01
17
04
73
04
17
05
71
03
94
03
99
04
39
05
05
04
33
03
66
07
26
05
19
05
17
02
54
09
77
Fe
3thorn
01
94
00
71
00
32
00
57
02
27
01
19
00
82
00
91
00
55
04
63
01
96
00
78
00
43
02
75
03
80
01
68
02
01
00
94
Fe
2thorn
13
17
12
97
21
11
21
72
14
20
13
89
15
64
09
87
09
73
15
01
18
47
13
79
12
70
22
10
16
17
12
80
14
21
16
62
Mg
33
07
33
11
27
45
27
16
32
69
32
60
28
77
36
65
36
27
34
31
27
90
32
12
33
30
22
74
31
54
32
94
34
71
23
89
Mn
00
06
00
00
00
57
00
41
00
17
00
12
00
09
00
05
00
11
00
11
00
08
00
09
00
11
00
00
00
07
00
12
00
06
00
09
Ca
17
63
18
81
19
70
19
31
17
67
18
79
18
42
18
99
19
16
15
33
18
41
18
81
18
99
17
73
16
05
18
31
17
67
19
29
Na
02
67
02
13
00
29
00
31
02
67
02
30
02
78
02
28
02
17
02
11
03
19
02
85
02
07
06
62
04
20
02
56
01
29
04
89
K00
24
00
40
00
06
00
13
00
33
00
29
00
35
00
16
00
23
00
13
00
24
00
27
00
16
00
11
00
38
00
34
00
13
00
64
Su
m1
53
97
152
61
150
61
150
81
154
89
153
54
152
89
152
99
152
50
156
17
155
47
153
31
151
89
159
50
157
70
154
19
152
68
156
45
2050 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
Journal of Petrology 2018 Vol 59 No 11 2051
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
2052 Journal of Petrology 2018 Vol 59 No 11
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
2054 Journal of Petrology 2018 Vol 59 No 11
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
Journal of Petrology 2018 Vol 59 No 11 2055
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
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Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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Table 5 Whole-rock compositions of eclogites from East Kunlun Orogen
Sample 16KL-13 KL-14 KL-15 KL-16 KL-20 KL-23 KL-24 KL-26 KL-27 KL-37 KL-38 KL-40 KL-43 KL-44Location Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete Hekete
Major elements (wt )
SiO2 4722 4687 4672 5059 4721 4680 4709 4685 4859 4928 5090 4909 4827 4601
TiO2 347 243 147 201 286 271 281 397 183 179 170 208 235 254
Al2O3 1340 1449 1678 1503 1266 1391 1358 1287 1452 1420 1381 1438 1389 1413
TFe2O3 1660 1536 1284 1316 1613 1830 1839 1488 1430 1382 1351 1516 1574 1727
MnO 023 021 018 017 022 027 027 016 019 019 018 021 021 027
MgO 561 654 806 664 604 587 574 758 713 727 681 682 704 708
CaO 897 987 1173 917 1099 966 973 993 994 1007 958 938 911 951
Na2O 226 220 163 147 206 199 188 276 221 217 200 197 127 191
K2O 053 080 016 026 070 039 027 011 053 041 038 020 063 053
P2O5 044 028 006 050 030 027 031 032 014 012 014 021 020 025
LOl 062 054 029 024 069 005 006 048 046 039 033 022 103 058
Total 9934 9960 9994 9925 9987 10011 10002 9991 9985 9971 9936 9973 9974 10008
Trace elements (ppm)
Li 9572 11886 12266 10178 3894 7328 6108 2246 2134 11988 12776 2892 16782 265Sc 352 3618 3706 2312 3586 4032 4038 2888 348 3562 3274 356 3348 3448
V 4202 3668 2428 1993 4378 3894 3832 5282 2774 3064 2826 284 2844 315
Cr 7132 689 194 9732 14688 307 3398 5482 141 1561 1398 12842 11698 9824
Co 493 5016 4392 4536 4848 4844 5564 3826 5522 5112 4826 4526 5738 4488
Ni 414 4508 532 5226 6796 2436 3746 387 8176 8058 8646 579 903 6034
Cu 4476 4946 2268 2888 935 6482 6744 15508 9614 7452 7684 4794 7308 6132
Zn 10278 969 6614 1069 10738 10776 10948 731 8696 909 858 8048 9664 9938
Ga 225 2118 16002 2804 2204 2100 2044 2926 1905 1899 17586 17872 18384 1898
Rb 2202 284 6744 8066 15188 1708 11748 4922 2324 14978 12254 6686 3172 2692
Sr 16548 19216 11096 12438 386 2052 2124 3262 1622 13484 12542 1382 1371 13072
Y 4206 359 2474 223 3564 392 3976 2444 2738 2618 2518 3094 3544 352Zr 19975 14103 9359 10695 10074 16444 18717 18054 10537 9221 9523 11108 14079 14873
Nb 3468 2603 971 1838 1879 2198 2223 3449 1264 1127 1064 1352 1701 1570
Cs 1375 1088 0158 0786 0835 0754 0499 0227 1255 1550 1379 0750 2662 0399
Ba 6272 8378 1751 416 2078 4048 3796 13422 5768 674 6226 3002 455 5514
La 2638 19054 3776 14356 17228 9786 1494 18414 891 7704 8266 11246 1209 13884
Ce 5586 4082 8954 3078 4028 2136 3308 3884 2008 17132 17986 2548 2656 3116
Pr 7496 5542 13392 4258 5888 3138 4662 5316 2914 247 253 3608 3754 443
Nd 3268 2428 6874 19092 2706 15296 215 2352 1363 1178 11886 16594 17056 2024
Sm 7578 5966 261 4584 7006 4946 5992 5704 3848 363 3556 4388 4716 5346
Eu 2432 1881 1122 1562 2460 1850 2056 2272 1458 1416 1388 1556 1666 1874
Gd 8028 6520 3732 4798 7470 6596 7110 5628 4636 4502 4448 5110 5734 6274
Tb 1297 1079 0685 0749 1196 1172 1210 0852 0796 0771 0760 0881 1017 1053
Dy 8140 6882 4638 4562 7302 7548 7732 4982 5144 4932 4866 5776 6604 6608
Ho 1661 1396 0983 0899 1419 1548 1572 0962 1058 1013 0995 1194 1351 1333
Er 4596 3876 2808 2444 3824 4274 4360 2590 2958 2804 2754 3332 3804 3690
Tm 0640 0546 0402 0339 0515 0598 0608 0353 0413 0393 0385 0465 0534 0512
Yb 4072 3444 2602 2126 3152 3762 3852 2250 2616 2472 2436 2940 3344 3208
Lu 0599 0499 0389 0307 0453 0555 0569 0335 0385 0366 0363 0437 0497 0473
Hf 4822 3698 2402 2673 2730 4085 4668 4307 2650 2339 2447 2749 3440 3587
Ta 2096 1637 0604 1143 1161 1308 1334 2121 0840 0646 0617 0779 1000 0939
Pb 2380 11698 10046 12590 11400 10740 10700 4966 10204 5130 3214 6572 7828 9052
Th 2396 1733 0312 1512 2372 1647 1784 1746 0927 1016 1124 1545 1642 1634
U 0727 0637 0487 0505 1225 1084 1275 0624 0351 0324 0320 0389 0677 0454
(continued)
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
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Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
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Table 5 Continued
Sample 16KL-52 KL-53 KL-54 KL-56 KL-64 KL-80 KL-81 KL-83 KL-84 KL-91 KL-92
Location Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu Xiarihamu
Major elements (wt )
SiO2 4575 5053 5019 4899 5050 5088 5163 5181 5100 4611 4518
TiO2 627 118 124 142 102 082 104 162 104 294 304
Al2O3 1232 1271 1346 1359 1312 1285 1263 1245 1262 1339 1269
TFe2O3 1585 1274 1214 1440 1191 1078 1159 1419 1216 1749 1820
MnO 022 018 017 020 017 020 017 023 023 021 021
MgO 656 723 790 692 818 831 798 616 763 649 692
CaO 978 1088 1167 1112 1104 1050 1023 998 1175 1076 1111
Na2O 270 246 157 212 193 237 211 226 171 203 215
K2O 008 052 028 022 034 050 026 018 019 011 011
P2O5 022 009 009 011 009 006 007 013 008 025 026
LOl 004 057 052 035 083 180 125 009 060 009 011
Total 9979 9909 9922 9945 9913 9908 9895 9902 9901 9986 9999
Trace elements (ppm)
Li 1944 2224 15276 206 13855 2476 2462 16776 5504 1212 11144
Sc 4538 3908 3728 423 38006 3618 364 3834 3568 3886 4226
V 6744 3368 3166 3706 309467 2634 3088 3656 302 4558 4944Cr 482 16014 2154 1739 2403 3346 3488 9482 3376 2038 5848
Co 4644 4498 4606 5722 46691 4222 4332 4528 4534 5154 5438
Ni 352 698 9464 8472 97653 11064 12616 7074 12484 448 6642
Cu 6566 7786 7582 19426 88127 3152 6986 16992 9146 428 4938
Zn 8456 763 708 7872 74589 701 7436 8168 6692 8994 9226
Ga 18862 15562 15586 16292 15152 1365 14518 15392 12792 16952 1781
Rb 3098 12226 8616 8544 14571 219 7682 3848 5186 2002 10938
Sr 6548 2294 15282 17012 1649 2614 2102 134 1417 382 3448Y 4226 2096 19976 248 18359 15078 17646 3042 17688 14978 15802
Zr 16917 6414 6223 7421 4749 3555 4908 9263 4860 8445 8893
Nb 3260 367 556 644 294 235 367 968 300 894 964
Cs 0615 2216 15434 07876 0602 12818 09232 0278 0691 0345 0245
Ba 10826 2124 453 4216 66105 9992 5896 77140 27220 17066 11088
La 11314 3796 4912 604 4003 3596 3064 7746 3018 7808 7788
Ce 2534 9408 11384 13836 8865 7296 7426 17332 7570 17588 17916
Pr 3742 1485 17252 2056 1321 1077 1187 2520 1211 2558 2618
Nd 17958 7498 8308 9960 6504 5216 6018 11776 6140 11804 12158
Sm 508 2408 2482 2936 2060 1612 19178 3448 1958 2812 2946
Eu 1565 0919 0899 1079 0753 0619 0731 1181 0718 1138 1144
Gd 6004 3122 3006 3672 2615 2104 2452 4332 2456 2982 3134
Tb 1078 0559 0535 0653 0482 0386 0444 0777 0448 0462 0493
Dy 7510 3742 3560 4414 3233 2602 3068 5242 3016 2852 3040
Ho 1639 0796 0747 0945 0680 0563 0667 1127 0650 0574 0613
Er 4752 2286 2126 2706 1938 1658 1939 3284 1879 1557 1646
Tm 0689 0324 0300 0390 0276 0239 0276 0468 0268 0205 0218
Yb 4474 2084 1919 2506 1780 1584 1802 3010 1728 1246 1334
Lu 0670 0311 0282 0372 0270 0238 0267 0446 0260 0178 0192
Hf 4135 1524 1484 1770 1144 0844 1161 2186 1137 2611 2718
Ta 1736 0217 0376 0670 0179 0138 0549 0532 0176 0535 0528
Pb 1176 4966 1944 2964 4503 1712 1565 0838 0704 0579 0446
Th 0931 0457 0637 0693 0407 0282 0340 0972 0337 0114 0128
U 0199 0283 0291 0363 0204 0095 0124 0314 0113 0112 0033
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
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chemical zoning the XMn [frac14 Mn(Fe thorn Mg thorn Ca thorn Mn)]
values decrease slightly from core to rim and XMg [frac14Mg(Fe thorn Mg thorn Ca thorn Mn)] exhibits reversed zoning
Omphacite in eclogites from the Kehete and Wenquan
terranes have higher jadeite contents than that from the
Xiarihamu terrane (Table 2 Fig 3b) Phengite is a minor
phase found only in the eclogites from the Kehete ter-
rane Si contents in phengite vary from 344 to 359 Siatoms per formula unit (apfu) based on 11 oxygens
(Table 3)
Amphibole is a retrograde phase in eclogites from all
the three terranes Hbl thorn Pl occurs as a symplectite or
symplectitic coronas after garnet and omphacite
(Fig 2g and i) Results of EPMA (Fig 3c Table 4) indi-
cate that they show wide compositional variations butthere is no significant difference between coronas and
coarse amphibole grains in the matrix
Twenty-six eclogite samples (14 from the Kehete ter-
rane in the east and 12 from the Xiarihamu terrane in
the west) were selected for whole-rock compositional
analysis at the China University of Geosciences Beijing(Table 5) All eclogite samples are predominantly bas-
altic with SiO2 (4601ndash510 wt ) TiO2 (084ndash627 wt )
MgO (561ndash831 wt ) CaO (897ndash1173 wt ) and Na2O
(127ndash270 wt ) In a (NbY) vs (ZrTiO2) diagram
(Winchester amp Floyd 1976) five samples plot in the al-
kaline field whereas others plot in the subalkaline field
(Fig 4a) Discrimination diagrams as well as trace
element patterns show that the eclogites from the
Kehete terrane have the geochemical characteristics ofenriched mid-ocean ridge basalts (E-MORB) to ocean-
island basalts (OIB) or within-plate basalts (WPB)
whereas eclogites from the Xiarihamu terrane are simi-
lar to E-MORB and N-MORB (Figs 4bndashd and 5) The geo-
chemical characteristics of these eclogites suggest that
their protoliths were oceanic crust (including seamount)basalts
METAMORPHIC PndashT PATHS
Three stages of metamorphism of eclogites in the EastKunlun can be identified peak stage I with a mineral as-
semblage of garnet thorn Omp thorn CoeQtz thorn Rutile 6
Phengite stage II decompression of omphacite at dry
conditions to Cpx2thornoligoclase stage III amphibolite
overprinting with addition of H2O in the mid-crust
Coesite pseudomorphs and quartz exsolution rods in
Omp suggest UHP conditions during the peak stage ofmetamorphism GrtndashOpmndashPhn geothermobarometry
(Krogh Ravna amp Terry 2004) also indicates UHP condi-
tions of Pfrac14 291ndash303 GPa and Tfrac14610ndash675C (Fig 6)
The PndashT conditions of omphacite decompression into
Cpx2thornoligoclase cannot be precisely determined but
should lie below the stability curve of Jadeite thorn Quartzfrac14 Albite The amphibolite-facies retrogression is
marked by varying degrees of amphibolitization in all
Fig 4 Discrimination diagrams for eclogites from the EKO (a) NbY vs ZrTi after Winchester amp Floyd (1976) for rock classification(b) TaYb vs ThYb (modified after Pearce 1982) The compositions of modern normal mid-ocean ridge basalts (N-MORB) enrichedmid-ocean ridge basalts (E-MORB) and ocean-island basalts (OIB) are from Sun amp McDonough (1989) (c) HfndashThndashTa discriminationdiagram of Wood (1980) (d) NbndashZrndashY discrimination diagram of Meschede (1986)
Journal of Petrology 2018 Vol 59 No 11 2053
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
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eclogite blocks with the retrograde assemblage Hbl thornEp thorn Pl at 600C and 06 GPa Therefore eclogites
from the EKO record a clockwise PndashT path from subduc-
tion to exhumation (Fig 7)
HPndashUHP METAMORPHIC AGES
Three eclogites and two garnetndashmica schist samples
(three from the Kehete terrane and two from the
Xiarihamu terrane) were selected for zircon UndashPb dating
(Supplementary Data Appendix Tables S1 and S2 sup-
plementary data are available for downloading at http
wwwpetrologyoxfordjournalsorg)
Zircons separated from the eclogite blocks (samples16KL13 and 16KL27 from Kehete and 16KL87 from
Xiarihamu) are round to ovoid crystals and have a
diameter of 50ndash150 lm They all show a typical meta-
morphic origin with oval shapes and fir-tree and radial
sector zoning in CL images (Fig 8) Garnet thorn omphacite
thorn rutile inclusions were identified by Raman
Fig 5 Primitive mantle-normalized multi-element patterns foreclogites from the Kehete terrane (a) and the Xiarihamu ter-rane (b) Normalization values are from Sun amp McDonough(1989)
Fig 7 PndashTndasht path of eclogites in the EKO ZE zeolite facies PPprehnitendashpumpellyite facies EA epidote amphibolite faciesAM amphibolite facies GR granulite facies HGR high-pres-sure granulite facies BS blueschist facies Amp EC amphiboleeclogite facies Ep-EC epidote eclogite facies Lw-EC lawsoniteeclogite facies (after Liou et al 1998)
Fig 6 PndashT diagrams for three eclogite samples from the Hekete terrane with the assemblage Grt thorn Omp thorn Phn Calculation wasperformed using lsquoP-T calc eclogitersquo of Krogh Ravna amp Terry (2004)
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
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spectroscopy (Fig 8a and b) The U content in zircon
varies from 220 to 1487 ppm (mostly 300ndash600 ppm)with ThU ratios of 002ndash043 Thirty-two analyses of
16KL13 yield a concordia age of 4275 6 21 Ma (MSWD
frac14 036) 30 analyses of 16KL27 yield a concordia age of
4255 6 22 Ma (MSWD frac14 0069) and 30 analyses of
16KL87 4277 6 22 Ma (MSWD frac14 053) (Fig 9) These
ages suggest that the eclogites in the East Kunlunformed in a narrow age range of 428ndash425 Ma the same
as eclogites (428 6 2 Ma) from the Wenquan Terrane in
the easternmost EKO (Meng et al 2013)
Zircons in the two metapelitic samples (garnetndashmica
schists) (16KL39 from the east section and 16KL85 fromthe west section) show clear internal zoning with inher-
ited detrital cores and metamorphic rims (Fig 8)
Garnet and rutile inclusions were detected in the meta-
morphic rims by Raman spectroscopy (Fig 8b and c) In
sample 16KL39 from the east section of the East Kunlun
eclogite belt a total of 77 zircon grains were analyzedand 61 core analyses yielded 206Pb238U ages varying
from 453 6 5 to 971 6 10 Ma with peaks at 465 512
603 712 834 and 923 Ma Sixteen zircon rims in sample
Fig 8 Photomicrographs and cathodoluminescence (CL) images of zircons from the eclogites and metapelites in the EKO (a)Garnet and rutile inclusions in zircon from eclogite (16KL27) (b) Garnet inclusion in the rim domain of zircon from metapelite(16KL39) (c) Rutile inclusions in zircon from metapelite (16KL39) (d) CL images of zircons from eclogites omphacite (Omp) inclu-sion should be noted (e) CL images of zircons from metapelites The corendashrim structure and dark luminance of the rim domainsshould be noted
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
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nloaded from httpsacadem
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16KL39 have significantly low ThU ratios (001ndash006)
Twelve analyses form a concordia age of 4273 6 14 Ma(MSWD frac14 010) (Fig 10andashc) which is consistent with
the metamorphic ages of the eclogites Another four
analyses gave a younger mean age of 4105 6 2 Ma
(MSWD frac14 005) which may represent the amphibolite-
facies retrograde age of the HP belt Forty-five analyses
of zircon cores from sample 16KL85 yielded similar
ages ranging from 469 to 1162 Ma Six analyses of zir-
con rims gave a concordia age of 4275 6 2 Ma (MSWD
frac14 009) (Fig 10dndashf) the same as the ages of the
eclogites
DISCUSSION
The conditions of UHP metamorphism in theEast Kunlun OrogenThe 500 km long eclogite belt indicates the existence of
HPndashUHP metamorphism in a subduction zone associ-
ated with the East Kunlun Orogen Its rock assemblage
together with ophiolite and arc-volcanic rocks along this
belt suggests a tectonic melange and accretionary
complex that combines oceanic subduction and contin-
ental collision Peak metamorphic conditions are withinthe coesite stability field evidenced by quartz exsolu-
tion rods in Omp coesite pseudomorphs in garnet and
omphacite and PndashT calculations using the GrtndashOmpndash
Phn geothermobarometer of Krogh Ravna amp Terry
(2004) The metamorphic PndashTndasht path of the eclogite
shows a clockwise decompression path suggestingthat the eclogite blocks were exhumed from depths of
100ndash120 km
Evolution of the Proto-Tethys Ocean and forma-tion of the Pan-North-China ContinentThe remnants of the Early Paleozoic QinlingndashQilianndash
Kunlun Ocean preserved in the present-day Chinese
continent represent part of the Proto-Tethys Ocean
(Mattern amp Schneider 2000 von Raumer amp Stampfli2008 Stampfli et al 2013) All blocks in this region
including the South Kunlun Block QaidamndashQuangji
Block Central Qilian Block South China Block and
North Qilian Block which have been referred to as peri-
Gondwana have similar Precambrian basements
(records of 12ndash09 Ga orogenic assembly and 085ndash
07 Ga rifting of Rodinia) They are believed to have dis-persed from East Gondwanaland during breakup of the
Rodinia supercontinent (Yin amp Harrison 2000 Gehrels
et al 2003 Cawood et al 2007 2013 von Raumer amp
Stampfli 2008 Song et al 2012 2014 Han et al 2016
Xu et al 2016) in the late Neoproterozoic as recorded
by the 600ndash580 Ma rift-related volcano-sedimentarysequence and the oldest ophiolite (550 Ma) in the Qilian
orogen (Song et al 2013 Xu et al 2015)
The remnants of the Proto-Tethys Ocean preserved
in the northern Tibetan Plateau can be divided into the
Qilian Ocean in the north and the East Kunlun Ocean in
the south separated by the Qaidam Block Subparallel
oceanic-type accretionary belts and continental-typecollisional zones together with the three HP and UHP
metamorphic belts (Fig 1) suggest that the Proto-
Tethys Ocean must have experienced an evolution from
initial subduction at 520 Ma to final closure at
410 Ma The Qilian Ocean between the NCCndashTarim
and Qaidam blocks started to subduct at 520 Maand closed at 440 Ma followed by the northward con-
tinental subductionndashcollision of the Qaidam block at
Fig 9 Concordia diagrams for eclogites in the EKO
2056 Journal of Petrology 2018 Vol 59 No 11
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440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
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orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
440ndash420 Ma (Song et al 2013 2014) Ophiolites in the
EKO record formation ages of 540ndash460 Ma (eg Yanget al 1996 Meng et al 2015 Qi et al 2016 Li et al
2017) suggesting that the Kunlun Ocean between the
Qaidam and South Kunlun blocks had a similar history
to the Qilian Ocean in the north Arc volcanic rocks
suggest that the East Kunlun Ocean may have started
subduction at 450 Ma Ages of the Kunlun UPndashUHPbelt reveal that the Proto-Tethys Ocean finally closed at
428ndash410 Ma resulting in the formation of a united con-
tinent in North China by the end of Early Paleozoic
named lsquothe Pan-North-China Continentrsquo
Transition from Proto-Tethys to Paleo-Tethys inthe Northern Tibetan PlateauThe Proto-Tethys Ocean is generally considered to have
initiated at 550 Ma between the continents of Laurasia
and Gondwana (von Raumer amp Stampfli 2008 Song
et al 2013) However the transition from Proto-Tethys
to Paleo-Tethys is always ambiguous because there is
no clear subdivision of these two periods of oceanicspreading As shown in Fig 11 after closure of the
Proto-Tethys Ocean at 420ndash410 Ma in the East Kunlun
Fig 10 Concordia and histograms showing the age distribution of detrital zircons from two metapelite samples in the EKOSample 16KL39 is from the Kehete terrane and 16KL85 is from the Xiarihamu terrane
Fig 11 Schematic illustration of the evolution from the Proto-Tethys to the Neo-Tethys oceans and the formation of the Pan-North-China Continent (PNCC) 1 UHP metamorphic ages ofSouth Altun (Liu et al 2012) 2 HP metamorphic ages of eclog-ite and blueschist of North Qilian (Song et al 2006 Zhanget al 2007) 3 UHP metamorphic ages of North Qinling (Liu
et al 2016) 4 UHP metamorphic ages of North Qaidam (Songet al 2014) 5 HPndashUHP metamorphic ages of East Kunlun(Meng et al 2013 Qi et al 2014 this study) 6 UHP meta-morphic ages of DabiendashSulu (Li et al 1993 Liu et al 2006) 7HP metamorphic ages of eclogite and blueschist of NorthQiangtang (Zhai et al 2011) 8 HP metamorphic ages of blues-chists in Lanchangjiang (Wang et al in press) SA SouthAltun QL Qilian Block NQ North Qinling SK South KunlunNQ-SP North QiangtangndashSongpan SQ-LS South QiangtangndashLhasa
Journal of Petrology 2018 Vol 59 No 11 2057
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
orogen a wide Paleo-Tethys Ocean which was named
the lsquoRheic Oceanrsquo by von Raumer amp Stampfli (2008)
developed in the Late Paleozoic in the south and east be-
tween Gondwana and the Pan-North-China Continent (or
Hunic terranes von Raumer et al 2003) Ophiolites inthe Arsquonyemaqen accretionary belt of the East Kunlan
(eg Yang et al 1996 Bian et al 2004) and in Central
Qiangtang (Zhai et al 2016) suggest that the oceanic
crust of the Paleo-Tethys Ocean could be as old as
500 Ma The Paleo-Tethys Ocean had closed by 220 Ma
marked by collision between the South China and North
China blocks in the north (eg Li et al 1993 Liu et al2006) and between the South QiangtangndashSibomasu
blocks and South ChinandashNorth Qiangtang blocks in the
south (Zhai et al 2011 Wang et al 2018) (Fig 11)
CONCLUSIONS
(1) The eclogite belt consists of eclogite blocks metape-
lites marble and minor serpentinite blocks and extends
laterally for 500 km within the Kunlun orogenic belt
All eclogites show geochemical characteristics with E-
MORB and OIB affinities
(2) Coesite pseudomorphs quartz exsolution in
omphacite and PndashT calculations reveal that the EastKunlun eclogites experienced UHP metamorphism at
conditions of 29ndash30 kbar and 610ndash675C Zircon UndashPb
analyses show they formed at 430ndash410 Ma
(3) The East Kunlun eclogite belt was produced in re-
sponse to final closure of the Proto-Tethys Ocean at the
end of the Early Paleozoic
ACKNOWLEDGEMENTS
We thank Xianhua Li and his group for help with the
secondary ion mass spectrometry UndashPb dating of zir-
cons and Xiaoli Li for help with electron microprobe
analysis We also thank Hannes Brueckner Gueltekin
Topuz and an anonymous reviewer as well as EditorAlasdair Skelton for their constructive comments
which significantly improved the quality of the paper
FUNDING
This research was financially supported by the Major
State Basic Research Development Program(2015CB856105) and the National Natural Science
Foundation of China (grants 41572040 and 41372060)
SUPPLEMENTARY DATA
Supplementary data for this paper are available at
Journal of Petrology online
REFERENCES
Agard P Yamato P Jolivet L amp Burov E (2009) Exhumationof oceanic blueschists and eclogites in subduction zonestiming and mechanisms Earth-Science Reviews 92 53ndash79
Andersen T (2002) Correction of common lead in U-Pb analy-ses that do not report 204Pb Chemical Geology 192 59ndash79
Bian Q-T Li D-H Pospelov I Yin L-M Li H-S Zhao D-S Chang C-F Luo X-Q Gao S-L Astrakhantsev O ampChamov N (2004) Age geochemistry and tectonic settingof Buqingshan ophiolites North QinghaindashTibet PlateauChina Journal of Asian Earth Sciences 23 577ndash596
Carswell D A (1990) Eclogite Facies Rocks Glasgow BlackieNew York Chapman amp Hall 396 pp
Cawood P A Johnson M R W amp Nemchin A A (2007)Early Paleozoic orogenesis along the Indian margin ofGondwana tectonic response to Gondwana assemblyEarth and Planetary Science Letters 255 70ndash84
Cawood P A Wang Y Xu Y amp Zhao G (2013) LocatingSouth China in Rodinia and Gondwana a fragment ofgreater India lithosphere Geology 41 903ndash906
Dong Y amp Santosh M (2016) Tectonic architecture and mul-tiple orogeny of the Qinling Orogenic Belt Central ChinaGondwana Research 29 1ndash40
Dong Y He D Sun S Liu X Zhou X Zhang F Yang ZCheng B Zhao G amp Li J (2018) Subduction and accre-tionary tectonics of the East Kunlun orogen western seg-ment of the Central China Orogenic System Earth-ScienceReviews doi101016jearscirev201712006
Droop G T R (1987) A general equation for estimating Fe3thorn
concentrations in ferromagnesian silicates and oxides frommicroprobe analyses using stoichiometric criteriaMineralogical Magazine 51 431ndash435
Ernst W G (1988) Tectonic history of subduction zonesinferred from retrograde blueschist PndashT paths Geology 161081ndash1084
Ernst W G amp Liou J G (1995) Contrasting plate-tectonicstyles of the QinlingndashDabiendashSulu and Franciscan meta-morphic belts Geology 23 353ndash356
Gehrels G E Yin A amp Wang X F (2003) Detrital-zircon geo-chronology of the northeastern Tibetan plateau GeologicalSociety of America Bulletin 115 881ndash896
Han Y Zhao G Cawood P A Sun M Eizenhofer P R HouW Zhang X amp Liu Q (2016) Tarim and North China cratonslinked to northern Gondwana through switching accretionarytectonics and collisional orogenesis Geology 44 95ndash98
Krogh Ravna E J amp Terry M P (2004) Geothermobarometryof UHP and HP eclogites and schistsmdashan evaluation of equi-libria among garnetndashclinopyroxenendashkyanitendashphengitendashcoe-sitequartz Journal of Metamorphic Geology 22 579ndash592
Li Q L Li X H Liu Y Tang G Q Yang J H amp Zhu W G(2010) Precise UndashPb and PbndashPb dating of Phanerozoic bad-deleyite by SIMS with oxygen flooding technique Journalof Analytical Atomic Spectrometry 25 1107ndash1113
Li R Pei X Li Z Pei L Chen G Wei B Chen Y Liu C ampWang M (2018) Cambrian (510 Ma) ophiolites of the EastKunlun orogen China a case study from the Acite ophiolitictectonic melange International Geology Review 602063ndash2083
Li S Xiao Y Liou D Chen Y Ge N Zhang Z Sun S-SCong B Zhang R Hart S R amp Wang S (1993) Collisionof the North China and Yangtse Blocks and formation ofcoesite-bearing eclogites timing and processes ChemicalGeology 109 89ndash111
Li S Zhao S Liu X Cao H Yu S Li X Somerville I YuS amp Suo Y (2018) Closure of the Proto-Tethys Ocean andEarly Paleozoic amalgamation of microcontinental blocks inEast Asia Earth-Science Reviews doi 101016jearscirev201701011
Li X H Liu Y Li Q L Guo C H amp Chamberlain K R (2009)Precise determination of Phanerozoic zircon PbPb age bymulti-collector SIMS without external standardization
2058 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Geochemistry Geophysics Geosystems 10 doi1010292009GC002400
Li Z X Bogdanova S V Collins A S Davidson A DeWaele B Ernst R E Fitzsimons I C W Fuck R AGladkochub D P Jacobs J Karlstrom K E Lu SNatapov L M Pease V Pisarevsky S A Thrane K ampVernikovsky V (2008) Assembly configuration andbreak-up history of Rodinia a synthesis PrecambrianResearch 160 179ndash210
Liou J G Zhang R Y Ernst W G Rumble D amp MaruyamaS (1998) High-pressure minerals from deeply subductedmetamorphic rocks In Hemley R J (ed)Ultrahigh-Pressure Mineralogy Physics and Chemistry ofthe Earthrsquos Deep Interior Mineralogical Society of AmericaReviews in Mineralogy 37 33ndash96
Liu D Jian P Kroner A amp Xu S (2006) Dating of progrademetamorphic events deciphered from episodic zircongrowth in rocks of the DabiendashSulu UHP complex ChinaEarth and Planetary Science Letters 250 650ndash666
Liu L Wang C Cao Y T Chen D L Kang L Yang W Q ampZhu X H (2012) Geochronology of multi-stage meta-morphic events Constraints on episodic zircon growth fromthe UHP eclogite in the South Altyn NW China Lithos 13610ndash26
Liu L Liao X Wang Y Wang C Santosh M Yang MZhang C amp Chen D (2016) Early Paleozoic tectonic evolu-tion of the North Qinling Orogenic Belt in Central ChinaInsights on continental deep subduction and multiphase ex-humation Earth-Science Reviews 159 58ndash81
Ludwig K R (2003) Userrsquos Manual for Isoplot 300 AGeochronological Toolkit for Microsoft Excel BerkeleyGeochronology Center Special Publication 4
Mattern F amp Schneider W (2000) Suturing of the Proto- andPaleo-Tethys oceans in the western Kunlun (XinjiangChina) Journal of Asian Earth Sciences 18 637ndash650
Meng F Zhang J amp Cui M (2013) Discovery of EarlyPaleozoic eclogite from the East Kunlun Western China andits tectonic significance Gondwana Research 23 825ndash836
Meng F Cui M Wu X amp Ren Y (2015) Heishan maficndashultra-mafic rocks in the Qimantag area of Eastern Kunlun NWChina remnants of an early Paleozoic incipient island arcGondwana Research 27 745ndash759
Meschede M (1986) A method of discriminating between differ-ent types of mid-ocean ridge basalts and continental tholeiiteswith the NbndashZrndashY diagram Chemical Geology 56 207ndash218
Pearce J A (1982) Trace element characteristics of lavas fromdestructive plate boundaries In Thorpe R S (ed)Andesites New York John Wiley pp 525ndash548
Qi S S Song S G Shi L C Cai H J amp Hu J C (2014)Discovery and its geological significance of Early Paleozoicedogite in XiarihamundashSuhaitu area western part of the EastKunlun Acta Petrologica Sinica 30 3345ndash3356
Qi X Yang J amp Fan X (2016) Age geochemical characteris-tics and tectonic significance of Changshishan ophiolite incentral East Kunlun tectonic melange belt along the east sec-tion of East Kunlun Mountains Geology in China 43797ndash816 (in Chinese with English abstract)
Song S Niu Y Su L Zhang C amp Zhang L (2014)Continental orogenesis from ocean subduction continentcollisionsubduction to orogen collapse and orogen recy-cling the example of the North Qaidam UHPM belt NWChina Earth-Science Reviews 129 59ndash84
Song S G Zhang L F Niu Y L Su L Song B A amp Liu DY (2006) Evolution from oceanic subduction to continentalcollision a case study from the Northern Tibetan Plateaubased on geochemical and geochronological data Journalof Petrology 47 435ndash455
Song S G Zhang L F Niu Y Wei C J Liou J G amp Shu GM (2007) Eclogite and carpholite-bearing metasedimentaryrocks in the North Qilian suture zone NW China implica-tions for early Palaeozoic cold oceanic subduction and watertransport into mantle Journal of Metamorphic Geology 25547ndash563
Song S G Niu Y L Wei C J Ji J Q amp Su L (2010)Metamorphism anatexis zircon ages and tectonic evolutionof the Gongshan block in the northern IndochinacontinentmdashAn eastern extension of the Lhasa Block Lithos120 327ndash346
Song S G Su L Li X H Niu Y L amp Zhang L F (2012)Grenville-age orogenesis in the QaidamndashQilian block thelink between South China and Tarim Precambrian Research220ndash221 9ndash22
Song S G Niu Y L Su L amp Xia X H (2013) Tectonics of theNorth Qilian orogen NW China Gondwana Research 231378ndash1401
Song S G Yang L M Zhang Y Q Niu Y L Wang C SuL amp Gao Y L (2017) Qi-Qin Accretionary Belt in CentralChina Orogen accretion by trench jam of oceanic plateauand formation of intra-oceanic arc in the Early PaleozoicQin-Qi-Kun Ocean Science Bulletin 62 1035ndash1038
Stacey J S amp Kramers J D (1975) Approximation of terres-trial lead isotope evolution by a two-stage model Earth andPlanetary Science Letters 26 207ndash221
Stampfli G M Hochard C Verard C Wilhem C amp vonRaumer J (2013) The formation of Pangea Tectonophysics593 1ndash19
Sun S S amp McDonough W F (1989) Chemical and isotopicsystematics of oceanic basalts implications for mantle com-position and processes In Saunders A Damp Norry M J(eds) Magmatism in the Ocean Basins Geological SocietyLondon Special Publications 42 313ndash345
Topuz G Okay A I Schwarz W H Sunal G Altherr R ampKylander-Clark A R C (2018) A middle Permian ophiolitefragment in Late Triassic greenschist- to blueschist-faciesrocks in NW Turkey An earlier pulse ofsuprasubduction-zone ophiolite formation in the Tethyanbelt Lithos 300ndash301 121ndash135
von Raumer J F amp Stampfli G M (2008) The birth of theRheic Oceanmdashearly Palaeozoic subsidence patterns andsubsequent tectonic plate scenarios Tectonophysics 4619ndash20
von Raumer J F Stampfli G M amp Bussy F (2003)Gondwana-derived microcontinentsmdashthe constituents ofthe Variscan and Alpine collisional orogens Tectonophysics365 7ndash22
Wang F Liu F Schertl H-P Liu P Jia L Cai J amp Liu L(2018) Paleo-Tethyan tectonic evolution of Lancangjiangmetamorphic complex evidence from SHRIMP UndashPb zircondating and 40Ar39Ar isotope geochronology of blueschistsin XiaoheijiangndashXiayun area Southeastern Tibetan PlateauGondwana Research in press
Wang G Sun F amp Li B (2014) Zircon UndashPb geochronologyand geochemistry of the maficndashultramafic intrusion inXiarihamu CundashNi deposit from East Kunlun with implica-tions for geodynamic setting Earth Science Frontier 21381ndash401 (in Chinese with English abstract)
Whitney D L amp Evans B W (2010) Abbreviations for namesof rock-forming minerals American Mineralogist 95185ndash187
Wiedenbeck M Alle P Corfu F Griffin W L Meier MOberli F Vonquadt A Roddick J C amp Spiegel W (1995)Three natural zircon standards for UndashThndashPb LundashHftrace-element and REE analyses Geostandards andGeoanalytical Research 19 1ndash23
Journal of Petrology 2018 Vol 59 No 11 2059
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019
Winchester J A amp Floyd P A (1976) Geochemical magmatype discrimination application to altered and metamor-phosed basic igneous rocks Earth and Planetary ScienceLetters 28 459ndash469
Wood D A (1980) The application of a ThndashHfndashTa diagram toproblems of tectonomagmatic classification and to estab-lishing the nature of crustal contamination of basaltic lavasof the British Tertiary Volcanic Province Earth and PlanetaryScience Letters 50 11ndash30
Xu X Song S G Su L Li Z X Niu Y L amp Allen M B(2015) The 600ndash580 Ma continental rift basalts in NorthQilian Shan northwest China links between theQilianndashQaidam block and SE Australia and the recon-struction of East Gondwana Precambrian Research 25747ndash64
Xu X Song S G Allen M B Ernst R E Niu Y L amp Su L(2016) An 850ndash820 Ma LIP dismembered duringbreakup of the Rodinia supercontinent and destroyed byEarly Paleozoic continental subduction in the northernTibetan Plateau NW China Precambrian Research 28252ndash73
Yang J S Robinson T Jiang C F amp Xu Z Q (1996)Ophiolites of the Kunlun Mountains China and their tectonicimplications Tectonophysics 258 215ndash231
Yang J-S Wang X-B Shi R D Xu Z Q amp Wu C L (2004)The Durrsquongoi ophiolite in East Kunlun north QinghaindashTibet
Platea fragment of paleo-Tethyan oceanic crust Geology inChina 31 225ndash239
Yin A amp Harrison T M (2000) Geologic evolution of theHimalayanndashTibetan orogen Annual Review of Earth andPlanetary Sciences 28 211ndash280
Zhang J X Meng F C amp Wan Y S (2007) A cold EarlyPalaeozoic subduction zone in the North Qilian MountainsNW China petrological and UndashPb geochronological con-straints Journal of Metamorphic Geology 25 285ndash304
Zhang Y Q Song S G Yang L M Su L Niu Y L Allen MB amp Xu X (2017) Basalts and picrites from a plume-typeophiolite in the South Qilian Accretionary Belt QilianOrogen Accretion of a Cambrian Oceanic Plateau Lithos278 97ndash110
Zhai Q G Zhang R Y Jahn B M Li C Song S G amp WangJ (2011) Triassic eclogites from central Qiangtang north-ern Tibet China petrology geochronology and meta-morphic PndashT path Lithos 125 173ndash189
Zhai Q-G Jahn B-M Wang J Hu P-y Chung S-L LeeH-y Tang S-h amp Tang Y (2016) Oldest Paleo-Tethyanophiolitic melange in the Tibetan Plateau GeologicalSociety of America Bulletin 128 355ndash373
Zhu Y Lin Q Jia C amp Wang G (2006) SHRIMP zircon UndashPbage and significance of Early Paleozoic volcanic rocks inEast Kunlun Orogen Qinghai Province China Science inChina Series D 49 88ndash96
2060 Journal of Petrology 2018 Vol 59 No 11
Dow
nloaded from httpsacadem
icoupcompetrologyarticle-abstract591120435104339 by U
niversity of Durham
user on 01 January 2019