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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:
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
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
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
@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
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
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
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$,and in the Ml, M2 and M3 sites of amphiboles.
O.O O.1 O.2 O,3 O.4 FeV{Mg+ca+Fci2t+Mn) of pxd
Fig.9 Relation between Fe2" content of and Fe2"+Fe3" contents in the Ml, sites of amphiboles.
Concluding remarks
Although the maximum Mn coRtentM2+M3 sites fer almost all amphiboles
O.5 O.6
pyroxenoids
M2 and M3
iR
is
the Ml+about 2.0
131
Kiyotaka
p.f.g., it is wefth Retgng that the ameunt Gf Mpt inthe Ml site of cginepyroxeite is rcgch garger thait
that isc the MX, M2 a*d M3 sites of amphibeies.The iogic distfibutiens ef Ca, Fe2' aitd Mg fer both
gitanganean amphiboles aRd cgincpyrexeites afe mgchritere cencentfaSed fhait thGse of pyrexenoids.
These resggts Gf gonic distributions amoitg thecoexissiitg fyiaitgaitoait gr mangaitese sigicate ggxiiterals
show that the cation sites in pyrexeitoids are rather
imadequate te accommedate Gf varioas catiens cegit-
pared with the sites of ampkiboges asudcginopyroxenes, becagse the gatter mifterags have dis-
tiRctively differeRt cation sites: the A, M4 aitd the
Ml, k(l2 aftd M3 sites fer amphgboXes, and the Mlafid M2 site for cftiitGpyroxelles.
AcknowiedgewteRts - The a"ther wish to thankPrefessor emeritus Matsuo Nambu of Tehoku {-Jfti-versaty fcr the deRatioit ef sampies frome the}Iijikuzu twixe, te Prefessor Isamu Shinaso efKyushu EJRiversity for his hclpfgl advice oft EPMAanalyses. ffearty tl}anks are dge alsG to }?rofesser
Yashikazu Aoki of Kysshg Uifiversity fer vaivabkesuggestigns aftd critical reviewgng the inanascript.
[g]pis stssdy was supporsed by GraRt-iR-Aid for Sci-eittific Research (C) (Ne.04640743), the Miasistry of
Edecatiame, Science axd Cgkure, gapan.
Reference$
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(Received ectober 23, 1995; Accepted Nevember 20, 1995)
132
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