9
九州大学学術情報リポジトリ Kyushu University Institutional Repository Chemical compositions of the coexisting amphiboles, clinopyroxenes and pyroxenoids in manganese ore deposits from Japan and India Ishida, Kiyotaka Department of Evolution of Earth Environments, Graduate School of Social and Cultural Studies, Kyushu University https://doi.org/10.15017/8578 出版情報:比較社会文化. 2, pp.125-132, 1996-02-20. 九州大学大学院比較社会文化研究科 バージョン: 権利関係:

Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

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Page 1: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

九州大学学術情報リポジトリKyushu University Institutional Repository

Chemical compositions of the coexistingamphiboles, clinopyroxenes and pyroxenoids inmanganese ore deposits from Japan and India

Ishida, KiyotakaDepartment of Evolution of Earth Environments, Graduate School of Social and Cultural Studies,Kyushu University

https://doi.org/10.15017/8578

出版情報:比較社会文化. 2, pp.125-132, 1996-02-20. 九州大学大学院比較社会文化研究科バージョン:権利関係:

Page 2: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Wlt~*±~Jt1t~ ~ 2 ~ (1996) 125"'-'132J{Bulletin of the Graduate School of Social and

Cultural Studies, Kyushu Universityvo1.2 (1996), pp.125"'-'132

compositions of the coexisting amphiboles,and pyroxenoids in manganese

ore deposits from Japan and India

Kiyotaka ISHIDA*

Keywords : Element distribution, Manganoan amphibole , Manganoan aegirine-augite, Pyroxenoid

Abstract: The chemical compositions of the coexisting manganoan amphiboles (mainly the Na-Ca- and alkali-amphibole series) manganoan clinopyroxenes (the aegirine-diopside-johannseniteseries) and pyroxenoids were analyzed by means of an EPMA method. As the number ofdiopside molecule in manganoan clinopyroxenes coexisting with pyroxenoids increases, the num­ber of johannsenite molecule in them also tends to increase. Although the oxidation conditions

the ore formation do not have much effect on the Mn content of clinopyroxenes, theystrongly affect the ferrous iron content pyroxenoids. The calcium content in the M2 site ofclinopyroxene is larger than that in the site of amphibole. The M1 site of clinopyroxene canaccommodate much more Mn ions than the M1, M2 and M3 sites of the coexisting amphibole.On the other hand, Mg ions can occupy much more easily in the M1, M2 and M3 sites ofamphibole than the M1 site of clinopyroxene. This study shows that among the coexistingamphiboles, manganoan clinopyroxenes and pyroxenoids, almost all the rhodonites andpyroxmangites can accommodate the smallest amounts of Mg, Ca and Fe 2

+ in their structures.

Many mineralogical and petrological studies formanganese-bearing sodic-calcic and alkali amphibolesand aegirine-augite clinopyroxenes from contact orregionally metamorphosed manganese ore deposits inIndia, Japan, and the U. S .A . have been made(Roy, 1970; Nambu et al., 1980a; Klein, 1966).The formation of these minerals is generally fa­voured in parts of the manganese formation (manga­nese silicate rocks and oxide ores) that have beeninvaded by pegmatite dikes and veins (Roy andPurkait, 1968). The formation of almost all theseminerals is also favoured by strong oxidation.

Mineralogical properties of manganiferousamphiboles, namely chemical compositions, opticaland physical properties and parageneses, have beenreported by Bilgrami (1956), Roy (1970, 1974), Royand Purkait (1968), Nambu et al. (1980a), Mottanaand Griffin (1986), Ghose et al. (1986), Dasguptaet al. (1988), Hawthorne (1992) and Ishida (1984,1989, 1995). Those of manganiferous clinopyroxeneshave been also reported by Frondel and Ito (1966),Roy (1971), Nambu et al. (1980b) and Minagawa

(1992).However, little research has been carried out on

the relationships between chemical compositions andatomic partitions, both inter- and intra-crystalline,among these coexisting manganese silicate minerals.This is mainly because in most Mn-bearing silicateminerals ionic substitutions do not widely occur, andtherefore any crystal-chemical parameters orthermodynamic information can be obtained fromthem.

The purpose of this study is to describe thechemical compositions of the coexisting manganoanamphiboles, manganoan clinopyroxenes andpyroxenoids and the cation site occupancies withineach mineral, and also to investigate the distributionof elements among them.

Materials and experimental

Sample localities and mineral assemblages ofamphiboles, clinopyroxenes and pyroxenoids used inthis study are listed in Table 1. Almost all Na-Caand alkali amphiboles from Japanese manganese oredeposits coexist with pyroxenoids, while amphiboles

*Department of Evolution of Earth Environments, Graduate School of Social and Cultural Studies, Kyushu University,Ropponmatsu, Fukuoka 810, Japan.

125

Page 3: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Kiyotaka IsNmA

from IRdxan enes do itot, except sample GS aRdthese of yeglow t2rodites and maRgaRoait tremoktes,

respectively 0xgdes of indgan eres are mestgybraunate, with a trace ameunt of hematate m somesamples, whereas thGse ef Japa*ese ores arebraunite, magnetite, hegnatite, Jacobsite andpyrephanKe In general, the IndgaR ores are poorm Fe aftd their oxidation state gs mgch higher thanthe Japanese ones The chegnicai analyses were made gsgRg a scan-

nwtg electroit micrgscope 3EOL SEM35-CFff

equipped with a LINK SYSTEM 8gO-2-5eO energy-dispersive spectrometer aitd the ZAF-41FLS quaittytatwe aflalysis software systeiy} Operatwtg coRdi-tloRs were malntatwed at an acceieratmg vG}tage of15 kV and a beara cgrrent of l 5 RA on iron metai

Resugt$ and di$cu$$ion

/gmphlboges

Chemical cemposgtionsfor those agnphiboles have

aAd structgrag propefties

already beeit meptgopted

Table 1 Localities and mineral assernblages of materials used in thEs s{udy

Sample No Locality (EPMA) (Mmae)

Mmeral assemblages

Amph!boles clmopyroxenes Pyroxenoids Other mmerals

TNITN2NDI

ND2

ND3ND4ND5

HWHJI

HJ2

KDGS

29

189

27,174

17,273

l9

20

340

22

21

85

Tanohata

IX

Noda Tamagawa

11

brown MrfKozulite

dark brown

Mrb, Wm,

Mrf

Act

Mrf

brown Agt

brown Aebrewfi Agt

Nrn

RdR, NmRdn, Nm

Rdn

RdnRdnRdnRdn

Pxm

Ccp

Br

Phl, Kfs,

Qtz, Rds,

Tp,

Mag,

Hem, fo

11

11

11

brown Agt,-brown Agt

greenish Ccp, Py

dark-brown

dark-brown Mrf

HanawaHijikuzu

pale-bluish Tur

brown Mrf

tl

TG8ATG60TG64TG67TG68}v{K

brown Agt

reddish Ae

green Agt

Kfs, Chl, Bm,

Kfs

Yo, Kfs,

83

18

823

81

26,478

844

28

84

Ap(Sr), Brt, Pr

Kodaira

Gos(z)aisho

Taguchi

11

11

xl

11

MuRakata

green Mrb, Dan

yellow Mrb

greenish Wm

brown Agt

pale greemsh-yeilow Ric

pale yellowish-green Mrf

dark greenish Mrf

dark-brown Mrf

Rdn Grt(Cld),

Ab, Kfs,

Mag, Pr

Qtz, Mag,

HemAb, Yo,

Hemyellow Ae

brown Agt, greenish-Agt

browR Ae

RdnRdR, Bs

PxmPxmRdnRdn

Kfs(Ba),

Yo, Kfs, Ab, Qtz,

Kfs, Phl, Rds

Qtz

Ap(Sr), Mag, Bt

Yo, Kfs

Ab, Kfs, Ap(As), Br, Hem, Pr, fo

TRITR2TR3TR4TR5TR6TR8JNI

JN2

JN3

JN4

JN5

25

24

482a

482b

T!rodi

II

pale brownish Tr

pale-purplish Mrb

11

11

pale-purp1ish Mrb

pale purp1ish Mrb

492

487

649

481

486

498

499

500

JN6

JN7

JN8

JN9

509

510

480

5el

485

483

11

Il

/1Junawani

tl

11

II

11

11

11

/I

t/

yellow Tir

yellow Tir

yellow Wmred Mrf

pale purplish Mrb

violet Mrb

RdnRdn

Br

Br

Br

McAb, Ap,Kfs(Ba),

Qtz, Ap(Sr)

Br, Ap(Sr)

Mc, Br,Cal(Sr)

Cal(Mn),

Ktn, Br, Brt

brown Agt Rds(Ba), Pen

blue Agt Wlt, Ap(Sr)

yellow Tir

yellow Tir

RdnRdnRdR, BsRdfi

Grt(Cld),

Cal(Sr),

Qtz

Grt(Cld), Br, Kem

pale-brown Tr

JNIO

WHI

11

brown Di

brown Di Grt(Cld),

violet-Mrb

blue Mrf

blue Di

blue Agt

blue Di

Wadhona brown Agt

Br,

Ab,Phl,

Grt,

Kfs(Ba), Cal

Cal(Sr), Brt

Br, Qtz

Cal(Sr), Brt

Cal(Sr), Kfs

Amphiboles Mrf==manganoan magnesioarfvedsonite, Mrb=manganoan magnesioxxebeckrte, Wm-wwmanganoan fern-winchite, Act= manganoafi

actmohte, Tirxtirodite, Dan=dannemoxxte, Ric=manganoan nchterrte, Tr==manganoan tremolite

Clmopyroxenes Aemumanganoan aegirme, Agt=manganoan aegmne augite, Di=diopside

Pyroxenoids Rdn=rhodonite, Pxm :pyroxmangite, Bs=bustamite, Nrn =Batronambuljte

Other mmerals Kfs(Ba)=Ba bearmg potassium feldspar, Abffpt5ite, Mc =microlme, Phl=:manganoan phlogopite, Bt=manganoan biotite,

Chl= manganoan chloxxte, Grt(Cld)-"garnet contammg caldeflte molecule(Mn3Fe3'2SlaOi2), Tpmete phroite, Yo= yoshimuraite, Qtz= quartz,

Rds==rhodochrosite, Cal(Sr) ==Sr beanng calcite, Ktn==kutnahonte, Wit==withente, Ap(Sr) = Sr-bearmg apatite, Brtmbaryte,

Br--braumte, Mag =magnetite, Hem=hematite, Jb=jacobsite, Prwpyrophanite, Ccp=chalcopynte, Py==py"te, Penmpenwithite

126

Page 4: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Chemical compositiens of the coexisting amphiboles,

(Ishida, 1995). k have also beeR reported thatjudging frem the M6ssba"er spectra mostamphiboies from Japanese mangaRese ore depositscefitaiit both Fe2" and Fe3', whereas oniy the peaks

due to Fe3' have been observed iit a}g the sampgesfrem India.

A-site vacaRt atwphibGles, which coexist withclinepyroxeRes containing varying arltounts ef less

aegirine molec"ge, befoRg tG the Ca amphibGae ofthe manganoan tremoiite-actinoliSe series or te the

aikali amphiboge of the manganoait giaucophane-riebeckite series. On the othef ha"d, clinopyfoxeRes

which Åíeexist with Fe-Mg-Mn amphibeges centain avery sgitali agx}eunt ef aegiriite molecule, and their

chemicag cempositions begong to the diopside-hedeitbergite-johannsenite series.

Clinopyroxenes Clinepyroxeites ceexisting with pyroxeneids arein general (Rark brGwpt te pale yeliowish brewn with

rather weak pleochroism in thiit sectioRs, whilesome grains or rriargiRai parts of samples TG60 afid

ND2 afe yegiowish green with strong pleechreism.Other cliitopyrexenes net coexisting with pyroxenoids

are page biuish te reddish purp}e with stroRgpieochroism, except GS, that is pale yeilowishbrowfl with streng pieochreism. The optic signs ofsome of these cgiRopyroxeites were agso examined:ciinopyroxenes iq sampaes of TNI, ffW aRd JN3were 2V.==aarge, these in ND2 were 2Vz=iarge.

Table 2. Chemical cornpositions and structural formulae

clinopyroxenes and pyroxenoids in maRgnese ore depGsits from Japan aRd India.

Both signs were ebserved in T(}60 graims.

The structural formulae were cagcuiated ept thebasis Gf 6(O) as the totai iron in ferric state frorri

the M6ssbauer data (Tabie 2). For fiiost samples,

the ggmbers of Na plas Ca are in the range efO.950-vl.OeO. Thus, the M2 site of theseciinepyroxenes is occupied by Na and Ca ieRs and a

smaii amount of MR. While the Ml site is eccu-pied mainly by Mn, Mg, Fe3' and trace amegnts ofTi aitd Al.

Aimost aai these ciinopyroxes are cemposed efaegirinc (Ae, NaFe3'Si,e6), diopside (Di, CaMgSi206) aitd jehaitnseitite (Jh, CaMnSi206) moiecules.The chemicag cotwpositiefis of these cgiRepyroxeResafe plotted oft tke Ae-Di-jh triaitgles iit Hg. 1. gn

the almest ciiitepyroxeites coexisting withpyroxenoids, the Rumber ef johaxnsenite mogeculeincreases with ificreasing amouitts ef diopside mole-

cule, reachigg up to 36 mei %. While inciiffopyrexeites Rot coexgsting with pyroxefioids, the

chemicag variation in the aegiriRe-diopside join ispredorr}iRant. Ca-rich cginopyroxenes in sampies JN6 and JN7, both coexistiAg with pyroxeitoids, showa chemical variation in the diopside-jehanptsenitejoin.

Pyroxenoids

There are maingy three kiftds ef pyrexenoidswhich coexist with amphibeges and/or cliRopyroxenes:

rhedenite, pyroxmaRgite and bustamite. These

of manganoan clinopyroxenes.

HIYI TN2 }{[l2 MK HW NDI 'ITNI KD TR8 ND2 T([}60 JN6 JN7 GS JN9 JN3 WM JN20 JN8

sie2

N203Ti02

MgOFe203*

MnOCaONa20

K,O

52.31 52.37 50.45 52.l9

G.el O.27 O.28 O.37O.04 O.96 O.18 O.25O.78 2.42 1.43 2.73

31.59 26.37 29.48 25.23

2.73 2.14 2.42 4.401.47 2.eO 3.16 4.88

10.90 12.09 ll.23 le.25

o.ol o.o3 e.o2 o.ol

52.40 5a.50 52.03 51.23 53.26

O.38 Z.08 O.23 O.77 e.29O.59 O.17 O.98 O.OO O.284.19 4.04 3.91 3.18 5.50

21.82 19.54 20.39 23.38 l9.96

4.74 6.46 5.95 6.08 5.447.20 7.75 7.80 8.32 7.759.40 9.26 9.30 8.49 7.33o.o2 o.ol o.ol o.el o.ol

52.58 52.22 52.17

O.24 O.2e e.37O.31 O.22 e.026.74 6.l4 IO.83

l4.92 15.86 5.61

8.05 7.25 8.7211.28 12.93 18.91

6.48 5.74 2.04O.Ol O.03 O.03

54.13

O.80

O.04

13.40

4.64

5.72

20.24

2.07

O.Ol

51.85

O.47

O.15

3.41

25.31

4.21

3.29

9.97

O.02

53.21

G.30

O.22

4.36

25.33

O.72

5.96

9.61

O.Ol

53.48

e.7o

O.48

5.89

19.67

2.47

7.83

8.61

O.02

53.50

e.o7

O.08

7.63

14.75

4.33

13.42

6.07

O.Ol

55.46

O.85

O.03

l6.21

2.52

O.69

23.65

1.38

O.Ol

54.84

O.34

O.04

16.67

l.21

l.05

24.30

l.12

o.oo

Total 99.84 98.65 98.64 10G.31 100.74 99.81 IOO.60 IOI.46 99.82 100.6! 100.59 98.70 101.05 98.68 99.72 99.15 99.86 100.80 99.57

Si

NTi

MgFe3'

MnCa

Na

K

2.012 2.008 l.973 l.995

O.OOI O.O12 O.O13 O.O17

o.ool o.o2s o.oos o.eo7

O.045 O.l38 O.083 O.156

O.9i5 e.761 O.868 O.726

e.osg o.e66 o.oso o.142

o.o61 o.os2 o.133 o.2eo

O.813 O.898 O.852 O.760

o.eel o.ool o.ooo o.ool

1.988

O.O17

o.el7

O.237

O.619

O.152

O.296

O.691

O.OOI

l.979 1.986 1.954 2.020

O.049 O.020 O.034 O.Ol3

o.oos o.o2s o.oeo o.oos

O.231 O.223 O.181 O.311

O.565 O.586 O.671 O.570

O.210 O.192 O.i96 O.l75

O.314 O.319 O.340 O.314

e.690 O.688 O.627 O.539

O.OOI O.OOI O.OOI O.OOI

1.994 1.985 1.992

O.O12 O.O09 O.O17

O.O09 O.O06 O.OOI

O.381 O.353 O.616

O.426 O.453 O.161

O.259 O.234 O.283

O.459 O.527 e.774

O.455 O.422 e.150

O.OOI O.OOI O.OOI

1.987

O.035

O.OOI

O.733

O.128

O.178

O.795

O.I47

o.ooo

2.005

O.022

O.O05

O.I96

O.737

O.I38

O.136

O.747

O.OOI

2.012

O.O14

O.O06

O.245

O.721

O.023

O.241

O.705

O.OOI

2.e21

O.032

O.O14

O.332

o.s6e

O.079

O.317

O.631

O.OOI

2.016

O.O03

O.O02

O.428

O.419

O.138

O.542

O.444

O.OOI

1.995

O.036

O.OOI

O.870

o.e6s

o.e21

e.912

O.097

O.OOI

2.000

O.O15

O.OOI

O.905

e.o34

O.033

O.948

O.081

o.ooo

Total 3.938 3.994 4.0e9 4.004 4.018 4.e44 4.e33 4.004 3.951 3.996 3.990 3.995 4.004 3.987 3.968 3.987 3.993 4.001 4.017

Cal(NaÅÄCa) O.070 O.084 O.135 O.208 O.300 O.313 O.317 O.352 O.368 O.502 e.555 O.838 O.904 O.154 O.255 O.334 O.450 O.904 O.921

* : Total iron as Fez03.

HJ2'vJN7 : clinopyroxenes coexisting with pyroxenoids.

GSNJN8:clinopyroxenes not coexisting with pyroxenoids.

127

Page 5: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

@ee

3e

jh

GSec Q

@

tf!q

$,YH1xkY tw8rrtr Ejuagu

op<ftSeuej[paN3=V ll u

Kiyetaka

eAe

3e

m

Sh

JN9

rgsss

50

ts

mu

JNIO D; jhiiiiliil, 3e

ee tw tw

JN7 % ee

s c

TG60 3g o {:g;'.tE.E;M,t/esi$$li'lil/:G'iX;tSD/7 .,gi:g S..,.i rG6e

Sh

30

Dg

as-co

Fig.1 Chemical cornpositions of manganoan clinopyroxenes

plotted on the aegirine (Ae, NaFe3'Si206)-diopside

(Di, CaMgSi206)-johannsenite (Jh, CaMnSi206) dia-

g ra m.

a: Manganoan clinopyroxenes not coexisting with pyroxenoids. b and c: Manganoan clinopyroxenes coexiting wlth pyroxenoids.

Circles: Manganoan clinopyroxenes from the Japa- nese manganese ore deposits. Squares and dia- monds: Manganoan clinopyroxenes from the Indi- an manganese ore deposits.

Table 3. Chemical compositions and structural formulae of

ISHIDA

mineragogical identificatiell was made by means of an eptical micrescepe and XRD. IR some sampies, Ratronambuiite is aXso present: in the satwple TNI the pyroxenoid is only natronumbugite, and ilt the sarrxples NDI afld TN2 matronambuiite is present engy in a trace amoupt. The chemicai compositions aRd structural formulae calculated oit the basis ef 6 (()) are listed iR TabXe 3.

The chemicag compositiens of rhedonites, pyroxymangites and bustamites are pletted oit the Mn-(Mg+Fe2')-Ca (Fig. 2) afid also on She (Ca+ Mit)-Mg-Fe2' diagrams (Fig. 3). There is a Ca content be"ndary between pyrexmangite and rhodonite at about 5'v7 atomic 9o Ca, and anethef boundary between rhodonite and bustamite, at 22 •"v30 atemic 9o Ca (Fig. 2). Fig. 3 shows that the

Mg centent for pyfoxmangites reaches up te 20 atomic 9(o, and for rhodongte aRd bustaixite up te le atomic 9o. It also shows that the Fe2' ceRtent for pyroxmangite reaches up to 37 atomic %, while that for rhodoRite up te 27 atomgc 91o. Thus, ameng the pyroxenoids examined, pyrexmaRgite cag accommodate very iarge ameuitts of Mg and much more Fe2' in the structure, whereas rhedefiite and

bustamite centain rather smager ameuRts (cf. Momoi, l964).

DistribgtiGR of elewteRts

Ca-Na-Mn dtstribation The crystal-•chemicai properties of the M2 site ef

cignopyrexene are siraigar go those ef the M4 site of

amphibeie, while those of the Ml site ef cginopyroxeite are simigar te these ef the Ml, M2 and M3 sites ef amphibele (Hawtheme, 1983; Ghose ef al., l986). Since it beceme ciear that the

M2 site of the cginepyroxeites contains Ca and Na igns and also the M4 site ef amphiboges contains

pyroxenoids (rhodonite, pyroxemangite and bustamite).

T664 HJ2 TG68 TG67 ND3 ND4 TR8 TR6 ND5 TG8ASample Pxm Pxm Rdn Rdn Rdn Rdn Rdn Rdn Rdn Rdn

MK JN5 IN4 }i[W NDI TN2 KD [[N6 TG60 JN6 T([}60Rdn Rdn Rdn Rdn RdR Rdn Rdn Rdn Rdn Bs Bs

Si02

MgOFeO"

MnOCaO

48.64 47.23 47.37 46.09 46.88 47.11 46.22 47.34 48.09

5.63 3.28 2.16 2.12 l.24 l.40 2.29 2.61 2.121.81 12.81 3.38 3.35 O.72 O.90 O.37 O.27 4.86

43.38 36.17 43.74 44.84 46.81 46.67 45.43 45.61 41.99

1.22 O.93 3.04 3.ll 3.42 3.82 4.27 4.44 4.63

45.68

1.83

5.35

40.70

4.58

47.43 47.34 47.59 47.8e 47.43 45.95 48.05 47.e8 48.eO 47.63 48.66

1.24 2.53 2.17 2.06 1.51 e.70 1.30 1.86 O.89 1.34 O.92O.24 O.20 O.21 O.96 O.28 O.26 2.80 O.18 3.23 O.26 1.l9

46.83 45.42 45.83 43.96 44.61 44.76 43.09 43.27 40.63 36.19 35.87

4.80 4.88 5.01 5.15 5.75 5.91 5.71 7.46 8.74 i3.69 14.68Total IOO.681eO.42 99.69 99.51 99.07 99.90 98.58100.27101.69 98.14 leO.54 IOO.37 100.81 99.93 99.58 97.58 10e.95 99.85 101.49 99.11 IOI.32

si

MgFe2+

MnCa

2.010 2.eOe 2.015 l.975 2.016 2.0e9 l.990 1.998 2.005 1.985

O.347 O.207 e.137 O.137 O.079 e.e89 O.l47 O.164 O.132 O.Z18

O.063 O.454 e.120 O.121 O.e26 O.032 O.O13 O.OIO O.169 O.195

1.518 1.297 1.575 1.642 1.705 1.686 1.657 1.630 1.482 1.498

O.054 O.042 O.139 O.144 O.158 O.175 O.l97 O.201 O.207 O.213

2.008 1.996 2.00e 2.017 2.014 2.007 2.016 l.993 2.003 2.0e2 2.003

O.078 O.159 O.136 O.130 O.096 O.046 O.081 O.l17 O.055 O.e84 O.056

o.oog o.oo7 o.eo7 o.o34 o.olo o.olo o.ogs o.oo6 o.113 o.oog o.o41

1.679 1.622 1.631 1.571 l.604 1.655 1.531 l.551 l.436 1.288 1.250

O.218 O.220 O.226 O.233 e.262 O.276 e.257 O.338 O.391 O.616 O.647

Total 3.992 4.000 3.986 4.019 3.984 3.991 4.004 4.003 3.995 4.009 3.992 4.004 4.000 3.985 3.986 3.994 3.983 4.005 3.998 3.999 3.997

*: Total iren as FeO.

Rdn= rhodonite, Pxm :pyroxmangite, Bs= bustamite.

128

Page 6: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Chemicai composltlons of the coexisting amphiboles, clinopyroxenes and pyroxenoids in mangneseore deposits from JapaR and India.

oMloo oMnioo

50

10

40

a

2e ..")

,,

gl.lr, }Ge4

N03 geNDIrGfie /-2icL•:

ast

'rc scf-' '•,4/

JN5

SO 10rho onite

90

pyroxmanglte3e

fli ,•k

tttl

1. tlt

TR6g'tt" ,,., VN4 ,' ,,i ,,//11

/e l].xfv tti!a /i/

ittlA ts"lj

,x' a i'

/. // ND5

o

70

GO

{Mg+OFe} IO O le 2o Atornic "te

30 4e50

soCa

ee?oo X?oe

30 ,.X. Jt it tttth Jt ...As

tt A 1, HJ2

20

Te

rhedonite i,t`'L..MK

rG

f,ke//G•il///,i'gek4S,..,r",

"Ise'rG6A

'4e :tts!pyroxmangite :.4,/

o

eo 40

g .gi.

30

20

10 o

rhodonite soKD,21'ee..k,•ec"'ls'--ts

'-' "i.e-i.:I"

g .". 1:

'•A.- JNe 7e rGeo {tF.le•

bustamlte60

e lo 2e 3o 4o se e lo {Mg+Fe} AtomicO/a Ca {Mg.Fe)Fig.2 Chemical compositions of pyroxenoids piotted on the a and b: Pyroxenolds containing less than 15 atomic O/o c: Pyroxeneids containing more than 15 atomic O/o Ca. sk: Pyroxmangites. A: Rhodenites. V: Bustarnites.

{Ca+Mn} ,, b!Aassi.i[lilis,ss,t<c,i;if:ses.lliil,i..ege..il03 ,,

4e

so

X,,, es.,TGigNe,

rhocionltexsA X il

XeAA x,o XL XN X. AX' s, A X LsA lx st 7e !N L ND5S. 1 Ss l xgt

2e 3e 4o Atornic e/e

(Mg+Pe2")-Mn-Ca Ca.

20

seSG

Ca

diagram.

ttttt.

c'

Gtby'fG6`

pyroxmangite

60

asO

o

Mgo e o 10 20 Atomic "le

30 40so

sOFe2+

50o Mg

Fig.3

40

.!1.

30

20

{Ca+ua} {Ca+Mn} olOO oTOO TN2,.XKsl,61"' , ..,fi

Te.rhodonit -}eei,""1:I.66790

'.kttkNlfrGeA

(Ca,+,een}

JNE $ k.,,,i

ustamite

BO

Jt)- At--t

,ia4'X OL Ath-tZLN" sNx x- x ssHJ?Lxse. tXxx X...t-..-"'i.h), eo

pyroxman Ite4e

a

30

/

so se O iO AtoSIRce/. 3e 40 5FOe2+ MgO iOChemical compositions of pyroxenoids plotted on thea and b: Pyroxenoids containing less than 15 atomic O/oc: Pyroxenoids containing more than 15 atomic O/o Ca.Syrnboles are the sarne as those in Fig.2.

ts•z'- 'rG6o<' be"'."'/k', o

Kti'rsr'

rhocionlte

o

7e

60

2o se Atemic ele

Mg-(Ca+Mn)-Fe2" Ca.

4e s80 Fe2'

diagram.

129

Page 7: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Kiyotaka

Ca, Na and Mn atoms as described above, the re}a-

tion of Cal(Na+Ca) iR the M2 site ofclinepyroxeges versus Ca/(Na+Ca+MR) in the M4site ef amphiboles are piotted in Fig. 4. For ag-most alg samples, the number of Ca ions in the M2site of ciinepyrexene is larger thait that in the M4

site of amphibole. This is mainly because that theM4 site of amphibole can accemmodate mgch largeramounts of Mit than the M2 site of cginopyroxene.

aErd

6e

•.--

m"E.s

?i8&

g"}g

e

to

e,g

e.s

O.7

O.6

O,5

O.4

O.3

C.2

O.1

ao

g,' •}/"

/ //

j.i:1!w:-;,N.9. i<NDkk,3

Ti)31--(.>-/Ls(tillGj4s"ig2MK-Hw TRs

/ // /

///Z>LJN7

/

JN1Me,>-

OD O.1 O.2 03 O.4 O.5 O.6 O.7 O.8 Cal(Na"Ca} in M2 site of cpx

Fig.4 Relation between Ca/<Na+Ca) in the of clinopyroxenes and Cal<Na+Ca+Mn) M4 site of amphiboles.

O.9 l.O

M2 site in the

Isffi[DA

The relatioit between Ca centent ef pyroxenoids and that in the M4 site ef amphiboaes are plotted in

Ng. 5. It has a tendency that the Ca content in the M4 site of amphiboles increases with an increas-

iitg Ca coRtent of pyrexeneids, altheugh the fermer is iarger than the iatter. The main reasen is that the M4 site of amphiboie can be filled with Ca, however, in general rhodenite and pyroxmaRgite cait coRtain up to efie-fifth and one-sevellth ef Ca in their structures, respectively (Ohashi and Finger, 1975).

The reiatien betweeit the Ca conteRt in the M2 ske of cliAopyroxenes afid that of pyroxenoids is showit in Fig. 6. The Ca ceRtent in the M2 site of clinopyroxeffes is rauch larger thait in pyrexenoids.

The maximum Ca centent of rhodGnite is 22.e atemic ero iR sample TG60, and thus the Ca coktent ix the M2 site of clinopyrexes rises rapidly near 20

atomic % Ca in pyroxenoids.

O.9O

O.35

O.3O

s2as O.25

ts

--Åë

"•as

" O.20E.E

Gi O.15

8k

i O.iO

8

"TG64rG8A

rR6

me TG67 ND5

MK `lll TG6s

ND3"Q

/

//

l

JN5

g!g.,

ND1

/ //Ll)LrN2

//N>

/ / /./J

O.80

O,7O

x .a o,6o

`:i;

t.co O.50

k E .S O.40 8. S O.30

g•

a2o

O.l O

o.o8.

Fig.6

and

(gi•PY,3Zx.fxe,?gite

O,05

o.oo

+HJ2

/

/ND4

/IgI7,PK,r&X,mgite

O.OO O.05 O.10 O.15 O.20 Ca/(Mg"ca"Fe2'"Mn) of

Fig.5 Relation between Ca content and Cal(Na+Ca+Mn) ln the amphiboles.

13e

-+!bl6

O.25 030pxd

of pyroxenoids M4 site of

+G60

T"e+..i,liii-i<Di

•/• / M+K N'/X'/

././' +TN2 •//

OO O.05 O,10 O.15 O,20 O.25 OSO Ca/{Mg+Ca+Fe2'+Mn} of pxd

Relation between Ca content of pyroxenoids Ca/(Na+Ca) in the M2 site of clinopyroxenes. The solid curve shows the average Ca contents in the M2 site of clinopyroxenes, drawn by free hand.

Mg-Mn distribution

Akhough a smail amount of Mn may enter theM2 site of clinepyroxeptes, only Mn, Mg and Fe3"geiterally eccilpy the Ml site as for studied samples.

The reiationship befween the Mnl(Mg+Mn) in theMl site of ciinopyroxenes aRd that in the Ml, M2and M3 sites of amphiboles is plotted in Fig. 7.Except fer sample TN2, the Rumber of Mn iens inthe Ml site of clinopyroxenes is much larger thaRthat in the Ml, M2 aRd M3 sites of amphiboles.Thus, the Ml site of clinopyrexeRes can accox3kmo-

date much mere Mn ions than the Ml, M2 aRd M3

Page 8: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Chemical cempositions of the coexisting amphiboles,

sites of the coexisting amphiboges. In other word,Mg ions cafi occupy much more easily the Ml, M2and M3 sites of amphibeles than the Ml site ofclinopyroxeRes.

The magnesium content in pyroxenoids, in theMl site ef clinopyroxenes and in the Ml, M2 andM3 'sites of amphiboles are aiso plotted iR Fig. 8.

Mgt(Mg+Mfi) ratios both in the Ml site ofciinopyroxeRes and in the Ml, M2 and M3 sites ofamphiboies are abeut teit times higher than that ifi

rhodonite.

1.0

s2 o.g

as

spt- TN2o O.8

.w- o.7ut

s

l,,,,tfo, j,N,7,/,'t4','i"iliMD2KNZI,

/•/• / /

clinopyroxeRes and pyroxenoids

/ //

o.o o.1 e.2 o.3 a4 o.s o.6 o.7 e.s Mn/{Mn+Mg) in Ml site ef cpx

Fig.7 Relation between Mnl(Mn+Mg) in site of clinopyroxenes and in the Ml, M3 sites of amphiboles.

`aErd

O,9 1.0

the MlM2 and

iit mangnese ore deposits from Japait and India.

Fe distribution

SiRce almost ail iron is coRsidered to be in theferrous state fer pyrexenoids, their Fe2' content de-

creases extremely when the oxygen fugacity is highin their crystallizatien environmeRt. On the other

hand, amphiboles can accemmodate both ferrousaRd ferric irons, and generally they can contain upto 2.0 Fe3' p.f.u., rr}ainly occupyiitg the M2 site.

As the studied amphiboies, except ND5, do notcentain iron iR their M4 site but in their Ml, M2and M3 sites, the relatioit between the Fe2' conteRt

Gf pyrexenGids and the Fe2'+Fe3" contents in the Ml,

M2 and M3 sites of amphiboles are shewit in Fig. 9.The pyroxenoids which coexist with only Fe3'-cogtain-

iRg amphiboies contaiii belew 5.e mol 9o Fe2", where-

as pyroxeneids which coexist with both Fe2' and Fe3'

-contaiRing amphiboles centain a much largefameunt of Fe2' ions. Among these pyroxeiteids,pyroxmangite cait accommodate much larger amouRtsof Fe2" than rhodonite.

.,m 1.ooo$ O.90

.-ca

9 oso2S O.70---d.

.s . O.60Ev':5 O.50

s'as O.40

s.S O.30

?2& O.20\cs) O.102 o.o a

Fig.8

ND5"t

MK B rGes,ii,1fyiifl T9fii.i.7/

/' l /• l I

rN2

JN+s/ HJ2

trrt5ZLJYrRe

/ rR8 / /ITG67

HJ2

rhodoniterts'r"fie- pyroxmangite

/• i/'

•/• -:-:/-ge-s-2r =G64

/

aas:amph { o es:cpx

/• +/•

aEes

ts

8.tmsNE.

g•-ec

'EIi

ic'IL,

Llr

Sib

L't,• :

sc--

<&g :MÅë

Lt'

&Åë

le

O.9

O.8

O.7

O.6

O.5

O.4

O.3

e.2

TR8

O.1

JN5JN4

o.o

TG67 TTGG68As /

+MK.HW `'" /,t9

,DIN3D4

TR6 "TG)jlfr/

,TN)i3/

Hj2

s//

//

(:i590rgxO#liatfigite

OO O.02 O,04 O,06 O.08 OAO O.12 O.14 O.16 O.18 Q20 Mg/(Mg.Ca+Fe"+Mn) of pxd

Relation among Mg content of pyroxenoids,Mgl(Mg+Mn) in the FVII site of clinopyroxene$,and in the Ml, M2 and M3 sites of amphiboles.

O.O O.1 O.2 O,3 O.4 FeV{Mg+ca+Fci2t+Mn) of pxd

Fig.9 Relation between Fe2" content of and Fe2"+Fe3" contents in the Ml, sites of amphiboles.

Concluding remarks

Although the maximum Mn coRtentM2+M3 sites fer almost all amphiboles

O.5 O.6

pyroxenoids

M2 and M3

iR

is

the Ml+about 2.0

131

Page 9: Chemical compositions of the coexisting amphiboles ... compositiens of the coexisting amphiboles, (Ishida, 1995). k have also beeR reported that judging frem the M6ssba"er spectra

Kiyotaka

p.f.g., it is wefth Retgng that the ameunt Gf Mpt inthe Ml site of cginepyroxeite is rcgch garger thait

that isc the MX, M2 a*d M3 sites of amphibeies.The iogic distfibutiens ef Ca, Fe2' aitd Mg fer both

gitanganean amphiboles aRd cgincpyrexeites afe mgchritere cencentfaSed fhait thGse of pyrexenoids.

These resggts Gf gonic distributions amoitg thecoexissiitg fyiaitgaitoait gr mangaitese sigicate ggxiiterals

show that the cation sites in pyrexeitoids are rather

imadequate te accommedate Gf varioas catiens cegit-

pared with the sites of ampkiboges asudcginopyroxenes, becagse the gatter mifterags have dis-

tiRctively differeRt cation sites: the A, M4 aitd the

Ml, k(l2 aftd M3 sites fer amphgboXes, and the Mlafid M2 site for cftiitGpyroxelles.

AcknowiedgewteRts - The a"ther wish to thankPrefessor emeritus Matsuo Nambu of Tehoku {-Jfti-versaty fcr the deRatioit ef sampies frome the}Iijikuzu twixe, te Prefessor Isamu Shinaso efKyushu EJRiversity for his hclpfgl advice oft EPMAanalyses. ffearty tl}anks are dge alsG to }?rofesser

Yashikazu Aoki of Kysshg Uifiversity fer vaivabkesuggestigns aftd critical reviewgng the inanascript.

[g]pis stssdy was supporsed by GraRt-iR-Aid for Sci-eittific Research (C) (Ne.04640743), the Miasistry of

Edecatiame, Science axd Cgkure, gapan.

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(Received ectober 23, 1995; Accepted Nevember 20, 1995)

132