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MINERALOGY AND PETROLOGY OF THE GRANADA MATERIAL
GEOCHEMISTRY
Bulk Chemistry
The Granada specimen is an ultramafic material containing (Table 20). This
value is considerably below that of normal basalts or ultramafic komatites. Furthermore,
the material is highly calcic (Table 20). The third most abundant oxide is FeO*, analyzed
as FeO and Fe2O3, (Table 20). Other prominent oxides include MgO and MnO (Table
20). Water occurs in both the H2O- and H2O+ states, respectively (Table 20). Upon
heating the sample the material gained 1.42% of its initial mass, which corresponds to a
–1.42% LOI.
Table 20: Bulk chemistry of the Granada material, with all values being in percents. Analysis was conducted by Actlabs, Inc. on February 13, 2004.
Oxide Wt. % Compound Composition SiO2 26.15Al2O3 3.71 FeO* 18.32 MnO 5.38 MgO 5.63 CaO 39.36 Na2O 0.16 K2O 0.35 TiO2 0.35 P2O5 1.34 H2O- 1.52 H2O+ 3.13
Trace Element Chemistry
The Granada material shows a general enrichment in its REE pattern, relative to
chondrite abundances (fig. 10). This enrichment is more prominent in LREE's than the
HREE's (fig. 10). HREE's are not as abundant as LREE's (values <10 x CN), and the
material displays small negative europium and holmium anomalies (fig. 10).
fig. 10: Graph represents the chondrite normalized REE pattern of the Granada material. All values are normalized after average C1 chondrite values from Anders and Grevesse (1989).
A depletion of chacophile and lithophile elements was found within the Granada
material (Table 21). However, low trace amounts of tin and antimony are present.
Despite the low distribution of chalcophile elements, a significant amount of copper (113
ppm) was found within the material (Table 21). The greatest elemental concentrations
are that of refractory elements such as vanadium (Table 21). Other elements such as
carbon, chlorine, and sulfur have high enough concentrations reported as weight percents
(Table 21).
Table 21: Trace element analysis of the Granada material. All values are in ppm unless otherwise noted. Values below the detection limit are indicated as b.d. Analysis was conducted by Actlabs, Inc. on February 13, 2004.
Element Concentration
Cl (%) 0.17 C (%) 0.61 S (%) 0.18 Ba 995 V 648 Cr 863 As 8.8 Sc 2 Be 1 Ni 49 V 648 Co 2 Cu 113 Zn b.d. Ga 7 Ge 1 Rb 14 Sr 180
Y 11 Zr 56 Nb 16 Mo b.d. Ag b.d. In b.d. Sn 11 Sb 1.1 Cs 1.0 Ba 995 La 10.3 Ce 18.6 Pr 2.07 Nd 8.0 Sm 1.6 Eu 0.38 Gd 1.6 Tb 0.3 Dy 1.6 Ho 0.3
Er 1.0 Tm 0.14 Yb 0.9 Lu 0.14 Hf 1.9 Ta 1.0 W 51 Tl b.d. Pb b.d. Bi b.d. Th 3.5 U 1.9 Pd b.d. Pt b.d. Au b.d.
Oxygen Isotopes and Radiometric Dating
The values for 17O and 18O are consistently high in both treated and pristine
samples (Table 22). Samples that are treated yield slightly higher concentrations of both
17O and 18O than the pristine samples (Table 22). The oxygen isotope analyses of the
Granada material display little deviation in 17O from the terrestrial fractionation line. The
overall average of the analyses is 14.10‰ for 18O and 7.20‰ for 17O, with D17O at -0.06
(Table 22).
Table 22: Oxygen isotope analyses of the Granada material. Sample "a" represents pristine samples and "b" represents samples treated in oxalic acid. Analysis was conducted by Dr. Nathalie Grassineau of the Royal Holloway University of London.
Sample d18O d17Oa-1 13.94 7.13 a-1 (duplicate) 13.90 7.11 a-2 14.21 7.24 Untreated Average: 14.07 7.18
b-3 14.06 7.17 b-4 14.19 7.28
Treated Average: 14.13 7.23 Overall Average: 14.10 7.20
The Granada material has 0.260% 40K and 0.717 nl/g of radiogenic 40Ar.
Moreover, the %40Ar contributed to air, which was removed from the calculation, is
80.4%. This corresponds to an age of 70.9 +/- 4.3 Ma; placing an upper boundary limit
of the late Cretaceous and a lower age limit of the early Tertiary.
MINERALOGY AND PETROLOGY
The Granada specimen consists of ultrarefractory materials. The ultrarefractory
mineral phases are aphanitic and typically less than 1.0 mm. Vesicles comprise
approximately 25% of the both the interior and exterior surfaces. They are typically
rounded to elongated and discontinuous throughout the groundmass.
With the assumption of equilibrium conditions, a CIPW norm calculation was
utilized to identify the potential existence of mineral phases (Table 23a). The unusual
chemistry of the material prohibited a normative calculation of high temperature-pressure
minerals. As a result, the calculation yielded varying assemblages from what is actually
present. Some assemblages were in good agreement with the phases that were identified
in the specimen (Table 23b). EMP identified 14 mineral phases, with 11 being optically
identifiable (Table 14). Olivine was expected to be present in such a silica-deprived
material; however, the only mineral that was found with high birefringence was
secondary calcite. The most abundant phase that exists is larnite, which is a rare calcium
silicate, formed naturally by contact metamorphism of limestones or artificially by
smelting processes to produce slag.
Table 23: (a) CIPW norm calculation of the Granada material and (b) estimated mineral assemblages. CIPW norm calculation is based on chemical analyses conducted by Acltlabs, Inc. on February 13, 2004 and observed mineral phases are based on a thin section prepared by Tulsa Sections, Inc. on March 10, 2004.
(a)Mineral Wt. % Larnite 57.63 Plagioclase 11.27 Olivine-Forsterite 10.46 Magnetite 10.33 Hematite 4.90 Apatite 3.34 Kalsilite 0.66 Halite 0.51 Ilmenite 0.48 Pyrite 0.26 Chromite 0.15 Zircon 0.01 Total 100%
(b)Mineral Wt. % Larnite 45 Magnetite 16 Sadanagaite 15 Magnesiowustite 6 Ilmenite 4 Merwinite 5 Galaxite 4 Native iron 4 Quartz 1 Secondary Calcite 1 Andesine <1 Orthoclase <1 Albite <1 Total 101%
Calcium Silicate & Amphibole Phases
Two calcium silicate phases, larnite and merwinite, are found within the Granada
specimen. The most abundant phase is larnite, occurring as microlaths less than 1mm,
composing approximately 45% of the groundmass (fig. 11a). Larnite was difficult to
identify because of its strong resemblance to plagioclase in crystal form, however it was
recognized by its birefringence. Unlike plagioclase, the larnite microlaths display a
second order green and red in polarized light (fig. 11b). The microlaths typically lack a
prominent orientation and display quenched cooling patterns, with a non-trachytic texture
relative to the groundmass. However, some localized microlaths are trachytic around
microphenocrysts of amphibole grains in a distinct radial orientation (figs. 11c, d).
Polysynthetic twinning is localized around a few individual grains, typically occurring
around crystal rims. The 2V angle of microlaths was difficult to detect, but larger than
anticipated. The large 2V angle is typical for high calcium mineral phases, and reflects
its calcic-enriched composition. Analysis by EMP showed that larnite is nearly pure in
composition, with only slight variations of manganese, magnesium, and iron (Table 24).
Merwinite occurs as microlaths that are less than 1mm in size. The microlaths are
anhedral and makeup an estimated 5% of the composition. They are similar to larnite in
that they have the same crystal morphology and are translucent in plain light. However,
unlike larnite, the microlaths are more anhedral and display first order red to low second
order blue colors in polarized light (figs. 11e, f). Analysis by EMP indicates that
merwinite is nearly pure in composition with only slight iron enrichment (Table 24).
With the exception of the calcium silicate phases the groundmass is composed chiefly of
opaque mineral assemblages.
fig. 11: Photomicrographs indicating the abundance of calcium silicate mineral phases as well as opaques, within the Granada material. The mineral phases are abbreviated as: mw- merwinite, l-larnite, sa-sadanagaite, il-ilmenite, sp-spinel, w-wustite and op-opaques. Blue areas are epoxy in-filled vesicles. Photomicrograph (a) in plane light displays a groundmass dominated by larnite microlaths, (b) is the corresponding photo in cross polarized light, (c) trachytic texture of larnite microlaths in plane light around sadanagaite, (d) photo in cross polarized light, (e) photomicrograph in plane light displays merwinite microlaths surrounded by spinel patches and oxides, (f) is the corresponding photo in cross polarized light.
a b
c d
e f
1 mm 1 mm
1 mm 1 mm
200 m 200 m
Tabl
e 24
: Ta
ble
disp
lays
the
chem
ical
com
posi
tion
of th
e ph
ases
in th
e G
rana
da m
ater
ial,
dete
rmin
ed b
y el
ectro
n M
icro
prob
e an
alys
is.
Ana
lysi
s was
con
duct
ed b
y D
r. El
lery
Fra
hm o
f the
Uni
vers
ity o
f Min
neso
ta.
Phas
e
SiO
2
K
2O
N
a 2O
Cr 2O
3
MnO
Al 2O
3
C
aO
M
gO
Ti
O2
Fe
O
Tot
al
Larn
ite
31.9
3 0.
59
0.08
0.
00
2.9
8 0
.13
58.8
9 2
.10
0.0
6 1
.42
98.
19
31
.84
0.57
0.
09
0.01
3
.28
0.9
0 57
.51
2.3
9 0
.17
1.7
8 9
8.54
32.2
4 0.
50
0.08
0.
00
2.4
5 0
.29
57.6
2 3
.73
0.0
5 1
.17
98.
14
Mer
win
ite
34.8
1 0.
10
0.10
0.
02
2.1
3 0
.18
51.4
4 9
.74
0.1
2 1
.59
100.
23
34
.58
0.13
0.
14
0.00
1
.79
0.1
4 51
.44
10.3
5 0
.06
1.4
0 10
0.03
34.4
7 0.
14
0.15
0.
00
1.9
5 0
.16
51.1
9 10
.11
0.0
0 1
.37
99.
53
Mag
nesi
owus
tite
0.0
3 0.
03
0.00
1.
17
31.9
3 0
.08
0.4
5 21
.18
0.0
2 44
.95
99.
85
0
.04
0.03
0.
00
2.09
31
.59
0.6
2 0
.59
20.6
8 0
.11
43.9
5 9
9.70
0.0
1 0.
00
0.00
1.
30
30.0
6 0
.05
0.6
8 25
.89
0.0
0 43
.56
101.
55
Mag
netit
e 0
.03
0.01
0.
00
0.05
0
.16
0.0
7 0
.06
0.0
0 0
.01
91.0
4 9
1.43
0.0
1 0.
05
0.03
0.
02
0.1
3 0
.06
0.0
5 0
.01
0.0
1 90
.76
91.
12
0
.00
0.04
0.
00
0.04
0
.09
0.0
9 0
.05
0.0
1 0
.01
90.1
3 9
0.46
Ilm
enite
0
.00
0.02
0.
03
0.00
4
.28
0.0
5 0
.00
0.4
7 45
.16
50.3
6 10
0.37
0.0
1 0.
05
0.08
0.
00
4.5
8 0
.04
0.0
0 0
.45
45.5
1 49
.26
99.
97
0
.00
0.01
0.
06
0.00
5
.00
0.0
0 0
.05
0.4
8 45
.19
49.3
0 10
0.08
G
alax
ite
0.2
7 0.
03
0.00
1.
34
10.9
6 57
.08
0.3
4 13
.73
1.7
1 13
.64
99.
08
0
.24
0.02
0.
00
2.03
11
.42
56.5
7 0
.58
12.0
7 1
.59
14.7
3 9
9.25
0.3
1 0.
01
0.00
2.
60
11.1
0 57
.01
0.5
1 12
.74
1.2
4 14
.07
99.
59
Si
K
Na
Cr
Mn
Al
Ca
Mg
Ti
Fe
T
otal
N
ativ
e iro
n 0
.98
0.03
0.
01
0.01
0
.00
0.0
0 0
.01
0.0
4 0
.01
98.1
9 9
9.26
0.0
0 0.
03
0.00
0.
00
0.0
0 0
.03
0.0
2 0
.00
0.0
0 99
.04
99.
13
0
.00
0.04
0.
04
0.01
0
.01
0.0
2 0
.00
0.0
1 0
.00
99.1
4 9
9.26
Tabl
e 24
con
t. Ph
ase
Si
O2
K2O
N
a 2O
Cr 2O
3
MnO
Al 2O
3
CaO
MgO
TiO
2
FeO
T
otal
Sa
dana
gaite
39
.95
1.4
7 2
.26
0.0
0 0.
09
13.2
7 12
.34
14.2
2 3
.90
11.2
3 98
.73
39
.79
1.5
3 2
.32
0.0
0 0.
08
13.2
6 12
.20
14.1
2 3
.84
11.1
6 98
.30
40
.20
1.4
6 2
.39
0.0
0 0.
16
13.1
8 12
.01
13.6
7 3
.53
11.7
3 98
.32
Qua
rtz
99.5
7 0
.03
0.0
2 0
.00
0.00
0
.04
0.0
0 0
.02
0.0
0 0
.06
99.7
4
99.2
3 0
.01
0.0
6 0
.00
0.00
0
.08
0.0
2 0
.01
0.0
0 0
.00
99.4
0
99.1
2 0
.02
0.0
0 0
.00
0.02
0
.02
0.0
2 0
.02
0.0
1 0
.14
99.3
7 A
ndes
ine
58.3
7 0
.33
6.9
9 0
.01
0.01
25
.72
7.7
0 0
.00
0.0
0 0
.41
99.5
4
57.9
6 0
.29
7.0
8 0
.00
0.04
26
.11
7.5
8 0
.01
0.0
0 0
.52
99.5
9
58.4
7 0
.26
6.8
8 0
.00
0.00
26
.29
7.9
2 0
.00
0.0
0 0
.50
100.
33
Orth
ocla
se
63.8
7 15
.55
0.9
5 0
.00
0.00
18
.69
0.0
8 0
.00
0.0
0 0
.09
99.2
4
64.3
4 15
.76
0.8
7 0
.00
0.01
18
.42
0.0
8 0
.00
0.0
0 0
.15
99.6
2
63.5
7 16
.52
0.2
6 0
.00
0.01
18
.79
0.0
2 0
.00
0.0
3 0
.10
99.3
0 A
lbite
68
.17
0.0
7 11
.67
0.0
0 0.
01
19.2
8 0
.09
0.0
0 0
.00
0.1
1 99
.40
67
.81
0.0
8 11
.36
0.0
0 0.
00
19.4
1 0
.32
0.0
0 0
.00
0.1
9 99
.17
68
.40
0.0
9 11
.73
0.0
0 0.
01
19.0
5 0
.14
0.0
0 0
.02
0.1
3 99
.56
SiO
2
K
2O
Al 2O
3
CaO
MgO
TiO
2
Fe
O
C
O2
T
otal
C
alci
te
0.0
0 0.
03
0.0
1 55
.13
0.54
0
.00
0.1
0 44
.96
100.
77
0
.02
0.06
0
.00
57.4
3 0.
52
0.0
1 0
.14
41.9
2 10
0.10
0.0
0 0.
08
0.1
6 54
.99
0.64
0
.00
0.0
8 44
.69
100.
64
Cal
cite
/qua
rtz
23.4
5 0.
11
0.2
0 35
.42
0.70
0
.16
2.5
6 38
.28
100.
88
12
.96
0.12
0
.43
42.1
1 0.
88
0.0
8 2
.26
41.4
1 10
0.23
6.8
1 0.
06
0.5
4 46
.81
0.88
0
.13
1.9
7 43
.40
100.
59
Sadanagaite, an amphibole group mineral, comprises approximately 15% of the
groundmass, as subhedral to euhedral microphenocrysts that are less than 1.0 mm.
Sadanagaite was difficult to identify, because of its resemblance to orthopyroxene in
crystal shape and structure. Sadanagaite lacks pleochroism and displays prominent
cleavage faces, which resemble pyroxene group minerals; particularly augite (figs. 12a,
b). However, EMP analysis confirmed the existence of an amphibole group mineral
(Table 24). The crystals occur as clusters, displaying a hypidiomorphic texture (figs. 12a,
b).
Moreover, the overall texture of the sadanagaite is poikilitic, meaning the amphibole
crystals exceed the size of the larnite crystals. Compositionally, sadanagaite is an
intermediate amphibole, corresponding to a hypothetical composition of 48%
anthophyllite, 21% grunerite, and a 30% calcium amphibole end member composition
(Table 24).
fig. 12: Photomicrographs of sadanagaite crystal clusters displaying a hypidiomorphic texture; (a) is in plane light and (b) is in cross polarized light.
a b
1 mm 1 mm
Opaques
Opaque phases compose 34% of the groundmass, and are mostly oxides.
Excluding native iron, the oxide phases include: magnesiowustite, ilmenite, galaxite, and
magnetite. All opaque phases occur as subhedral to euhedral crudely hexaoctahedral
crystals, except for magnesiowustite, which occurs as rounded orange grains.
Magnesiowustite make up approximately 6% of the groundmass, occurring as
spherules (fig. 13a). The spherules occur in clusters that are only a few dozen microns in
diameter, with some displaying unusual grape-like clusters (figs. 13b, c) and flower petal
like textures (figs. 13d, e). The spherules are orange to opaque in plane light, which
reflects a high manganese concentration. Compositionally, magnesiowustite grains have
an unusual high concentration of manganese (Table 24). Such an allocation of
manganese can only be accounted for if the 2+ coordination site allows for an excess of
manganese cations. Frondel (1940) found that the manganese substitution is related to
oriented inclusions of manganosite, implying a very low oxygen fugacity. Some
spherules have darker rims, which may reflect an iron-enrichment. Magnesiowustite
occurs chiefly with ilmenite and is modally concentrated as clusters on larnite
microphenocrysts (fig. 13b, c).
fig. 13: Photomicrograph of magnesiowustite occurrences within the Granada material. The mineral phases are abbreviated as: l-larnite, wu-magnesiowustite, op-opaques, and sp-spinel. Photomicrograph (a) in plane light displays a magnesiowustite cluster on a larnite microlath, (b) in plane light shows the distribution of magnesiowustite grape like clusters within larnite microlaths, (c) is the same photo in cross polarized light, (d) flower petal magnesiowustite structure on a larnite lath in plane light, (e) is the same photo in cross polarized light.
a
200 m
b
c
d
e200 m
200 m
200 m
200 m
Ilmenite grains occur as anhedral to subhedral elongated microphenocrysts that
are less than 1.0 mm; composing approximately 4% of the groundmass. They typically
occur with magnesiowustite spherules as localized clusters; however, some individual
microphenocrysts were found in association with amphibole phenocrysts (figs. 11c, d).
Ilmenite microphenocrysts were easily distinguished from the other opaque phases by
their occurrence and crystal structure. Compositionally, ilmenite has a significant
pyrophanite component (MnTiO3), corresponding to a composition of 9% pyrophanite,
2% geikielite, and 90% ilmenite (Table 24).
The majority of the groundmass is composed of opaques, particularly magnetite
and spinel. Spinel comprises approximately 4% of the material, with a crystalline habit
of irregular disseminated patches that are 1.0-2.0 mm (figs. 14a. b). The patches are
massive and granular, appearing opaque to green in plane light. Some patches display an
anomalous green reflectance in polarized light in reference to its fracture. The green may
imply its hercynite component. Moreover, the patches display conchoidal fracture and an
interstitial texture to sadanagaite microphenocrysts. The crystals that were analyzed by
EMP show an intermediate composition between galaxite and hercynite (Table 24).
Spinel corresponds to an end member composition of 25% galaxite, 20% hercynite, and
55% spinel. The spinel has an anomalous chromium concentration, which is probable
considering chromium and aluminum can be readily substituted into the 3+-coordination
site.
fig. 14: Photomicrograph (a) in plane light displays spinel patches on sadanagaite amphibole crystals, in a groundmass of opaques (magnetite). Photomicrograph (b) is in cross polarized light. Abbreviations are sa-sadanagaite, wu-magnesiowustite, op-opaques, l-larnite, and sp-spinel.
The most abundant opaque phase is magnetite, composing 16% of the
groundmass. The grains occur as 1-2 mm anhedral to subhedral crystals, and are
poikilitic in reference to the other opaque phases. Its occurrence and size make it readily
identifiable from the other opaque phases. However, considering its widespread
occurrence within the groundmass I refer to it as opaque (figs. 14a, b). Compositionally,
it is nearly pure with no major contaminants. Furthermore, EMP did not readily identify
the percentage of Fe2+ to Fe3+ in magnetite. Thus, a large percent of uncertainty exists
in assigning oxidation numbers to iron states to derive an empirical formula (Table 24).
The largest phase is iron metal, with grains being variable in size from 1.0-4.0
mm, composing approximately 4% of the specimen. Grains occur as poorly shaped
anhedral phenocrysts, with remnants of poorly-shaped crystal faces (fig. 15).
Compositionally they are relatively pure, with no kamacite component (Fe, Ni) (Table
24). However, one grain identified by the EMP showed an anomalous silicon impurity
a b200 m 200 m
(Table 24). Some iron phenocrysts show alteration halos of oxidation, characterized by
brown rims around the phenocrysts (fig. 15).
fig. 15: Photomicrograph in plane light displaying crudely hexooctahedral crystals of iron metal, sadanagaite crystal cluster, and individual quartz crystals. Arrow indicates oxidation around iron crystal. Phases are abbreviated as: Fe-iron, qtz-quartz, sa-sadanagaite, and oxi-oxidation. Blue area is epoxy in-filled vesicle.
Accessory & Secondary Phases
EMP identified various accessory minerals within the Granada specimen
including: quartz, plagioclase, orthoclase, albite, and calcite. However, with the
exception of quartz, no other phases were petrographically verified. All phases are minor
and comprise less than 1% of the groundmass.
Quartz occurs as localized subhedral crudely hexagonal clustered
microphenocrysts, with remnants of (001) and (010) faces (fig. 15). The
microphenocrysts display zoning, that is probably related to the pressure-temperature
constraints responsible for forming the mineral. The equant 6-fold symmetry of quartz
indicates that it is either a high-pressure polymorph of coesite or stishovite (Luo et al.,
2004). Compositionally, the quartz grains are nearly pure SiO2 with only minor
contaminants (Table 24).
1 mm
Three phases of feldspar were identified by EMP analysis including: plagioclase,
albite, and orthoclase. Plagioclase is an intermediate member, corresponding to andesine
in composition (Table 24). Compositionally, albite and orthoclase are pure with no
contamination (Table 24).
Calcite was identified on the outer edge of the section suggesting secondary
alteration, caused by weathering. Consequently, calcite was the only mineral identified
in the groundmass with a high birefringence. Calcite occurs as localized massive
decimated patches that vary in size as a function of occurrence (fig. 16). The patch
examined at the edge of the slide is approximately 2.0 mm in diameter. Calcite also
occurs around localized exterior vesicles and as fissures on the surface of the material.
Moreover, some patches of calcite analyzed by EMP, suggest an intergrowth with quartz
(Table 24). The EMP data obtained for intergrowth of quartz and calcite show a large
variation in the amount of silicon present (Table 24). It is unclear if the same event
responsible for forming the quartz microphenocrysts resulted in the formation of the
intergrowth.
fig. 16: Photomicrograph in plane light displays calcite surrounding vesicles and a calcite/quartz intergrowth. Abbreviations are qtz-quartz, ca-calcite, op-opaques, and l-larnite. Blue areas are epoxy in-filled vesicles.
1 mm
