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Title The system NaFe^<3+>Si_2O_6-CaFe^<2+>Si_2O_6 at low oxygene fugacity

Author(s) Ohta, Kohei; Onuma, Kosuke; Yagi, Kenzo

Citation Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy, 17(3), 487-504

Issue Date 1977-02

Doc URL http://hdl.handle.net/2115/36070

Type bulletin (article)

File Information 17(3)_487-504.pdf

Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP

Jour. Fac. ScL, Hokkaido Univ., Ser. IV,

vol. 17, no. 3, Feb., 1977, pp. 487-504.

487

THE SYSTEM NaFe3'Si2 06 -CaFe2'Si2 06

AT LOW OXYGEN FUGACITY

by

Kohei Ohta*, Kosuke Onuma aRd Kenzo Yagi

(with i table and 8 text-figures)

(Contribution from the Depaitment of Geology and Mineralogy,

Facuity of Science, Hokkaido University, No. 1482)

Abstract

,,,,T,h.e,gF.F,e.e",S;'g.O,z-/j,Ck?8r,`.8f,Sh,e,2Y,Ste.i",lll,a.F.e;ES,k2P.z:,C,?.,F,g,2'.S,ikO,-%,w,as.glgleg.'i,'ile61,a,t

atm. It was found that a high temperature foTm of hedenbergite has not 6-wollastonitestructure, but bustamite structure in the temperature range of iiOOOC-11750C. Three

Fe2'-bearing silicate phases were also confirmed by X-ray diffraction patterns and optical

properties: Fe-bustamitess, 6-Fe-wollastonitess, and or-Fe-wollastonitess (ss: solid solution).

These t}iree phases are solid solutions between CaSi03 and FeSi03 at low oxygen fugacity;

NaFe3'Si206 enters into the liquid when the crystalline phases coexist with liquid. The

following phase assemblages were encountered with increasing temperature: Fe-bustamitess

+ iron oxide + liquid, B-Fe-woliastonitess + Fe-bustamitess + iron oxide ÷ liquid,6-Fe-wollastonitess + iron oxide + liquid, 6-Fe-wollastonitess + a-Fe-wollastonitess + iron

oxide + liquid, and or-Fe-wollastonitess + iron oxide + liquid. The assembfages are essentially

the same throughout the range of oxygen fugacity investigated, except that magnetiteconverts to wthstite at low oxygen fugacity. Application of the system to the natural

pyroxene is also given.

Introduction

From experimental study of the system acmite-diopside and the natural

pyroxene from alkalic rocks, Yagi (1966) suggested that there are continuous

solid solutions in the system acmite-diopside-hedenbergite. Later Ohashi (1967)

confirrned the presence of a ccomplete seriesof solid solutions in the system

acmite-hedeRbergite at subsolidus teinperature, and Nolan (i969) showed that

continuous solid solutions exist in the subsolidus region of the system

diopside-hedenbergite-acmite. However, investigatioRs of the high temperature

region in the system acmite-hedenbergite has not yet been accomplished.

Bowen et al. (1933), investigating the system CaO-FeO-Si02 , demonstrated

that 6-wollastonite forms a solid solutioR with ferrosilite, which enters into

6-wollastonite up to 70 mole percent at high temperature with the substitution

* Present Address: Nippon Cement Co., Tokyo

488 K. Ohta, K. Onuma and K. Yagi

of Fe2' for Ca. Recently, many studies on the system CaO-FeO-Si02 were

carried out and the problems related to the structure of high temperature forms

of hedenbergite are presented (Peacor and Prewitt, 1963; Prewitt and Peacor,

1964; Rutstein, 197l ; Rutstein and White, l971 ; Matsueda, 1973).

From his experimental study Rutstein (l971) claimed that Fe2' cannot

substitute for Ca more than about 10 atomic percent in the 6-wollastonite

structure, and that specimens containing more than IO percent Fe2' have

bustamite structtire. Matsueda (1973), from his study of natural specimens as

well as experimental work on the system 6-wollastonite-ferrosilite, concluded

that the structure of iron wollastonite is different from that of6-wollastonite.

In the present study the phase diagram of the system acmite-hedenbergite is

determiAed at the teinperattire i'ange of lIOOOC - 12500C and at the oxygen

fugacity (fo, ) of 1O-9 - IC}-i i atm and the structural problem of CaFe2'Si2 06

is also discussed.

Experimental Methods

The ordinary quenching method was employed for the iiivestigation of the

phase diagram.

Homogeneous glasses were prepared by melting pure chemicals in aPtg o Rhi o crucible previously saturated with iron. Pure quartz, Fe2 03 , CaC03

and pure Na2 Si2 Os were used as sources. These homogeneous glasses were used

as starting materials for quenching experiments. Starting materials were held in

Pt6oRh4o envelopes in order to minimize the loss of iroii and suspended in a

vertical quenching furnace. A Pt-Pts 7 Rlii 3 thermocouple used to measure the

temperature was calibrated at the standard melting points of Au (I062.60C)

and diopside (1391.SOC).

The atmosphere in the furnace was controlled by running mjxtures of C02

and H2 gas at definite ratios. Calibration fof oxygen fugacity was made by

examining the stability field of hematite, magnetite, and wUstite.

X-ray diffraction pattems of the crystalline phases were obtained with

Ct}Ka radiation at 35 KV and 20 mA at room temperature. Reflections of

(210) and (I02) of 6-wollastonite, and (204) and (204) of bustamite were

obtained at a scaiming speed of 114 degree per minute, with silicon as an

external standard.

Experimental Results and DiscussioRs

e-ystalline phases

In the present experiment three different silicate phases were recognized.

THE SYSTEM NaFe3"Si2 06 -CaFe2'Si2 06 489

e A3.1OO

3.050

3.000

Lo

tog Po2=-11

Jp

ee

d2o4

CaFeSi206tj

FeBusss.WUs.L

I

fl1-i-l

/1-i---･

llll,fi-FeWos6d

i,EeHusssi'' WUs.L i I

fi-FeWOss.WUs.L

1100

l

1150 o1200 C

o A3.300

3.250

3.200

LogPo2=-11

li

dio4

Ca Fe S i206

ee

-d

FeBvsss.WUs.L

'

1!1t-I"

1-l.-../

lbln-FeWessli.FeBusss"

Hl1.WUs.L ,

ltpln-FeWoss.WOs.L

llOO 1150Teraperature

ol200 C

Fig. 1 Changes of d-spacings of B-Fe-wollastonitess and Fe-bustamitess crystailized fromthe composition of CaFe2"Si2 06 at 1OMi i atm fo2 . The open circles represent d2 i o

and dio2 of B-woilastonite and the soiid circles d2o4 and dio4 of bustamite. The

following abbrevations wil1 be used throughout all figures and tables. Fe-Bus =

Fe-bustamite, B-Fe-Wo = 6-Fe-wollastonite, or-Fe-Wo = or-Fe-wollastonite, WUs =

wUstite, Mt = magnetite.

From the X-ray dif{lraction patterns and optical data, it is suggested that these

three crystalline phases correspond to bustaminess, 6-woliastoRitess, and

a-wollastonitess. As all of these phases incorporate Fe2', henceforth these

phases will be described as Fe-bustamitess, 6-Fe-wollastonitess, and or--Fe-

wollastonitess, respectively. The 6-wollastonitess and the or-wollastonitess

represent wollastoRitess and pseudowollastonitess, respectively, as defined by

Bowen et aL (1933).

X-ray 'diffraction patterns of bustamite and 6-wollastonite are similar, but

490

o A3,1OO

3.050

3000

to

K. Ohta, K. Onuma and K. Yagi

Log Po2= --1 O

d 2o4

l-t----l-

"caFesi2o6" Irl---p /ee

i/ FeBusss.Fe-oxide .L l?FJe[Beuljssi .C}IF. se) LOss

"Wus.L l ll

11 00 11 50 e1200 C

t

e A3,300

3.250

3.200

Log Po2=-1 O

d io4

"CaFeSi206" l/ / l/l

FeSusss.Fe･･oxTtie.L

l t/----ldi

Trl---

ttil.,'eFi,Wu/tsil.:;-.F:Tl,oss

i/I1100 1150

Tery}perature

o1200 C

Fig. 2 Change of d-spacings of 6-Fe-wollastonitess and Fe-bustamitess crystallized fromthe composition of CaFe2"Si2 06 at 1OMi O atm fo2 . The open circles represent d2 i o

and die2 of 6-wollastonite and the solid circles d2o4 and d7o4 of bustamite.

Abbrevations are same as in Fig. 1.

the peaks of bustamite are located at 1-1.50 higher angle side in 2e compared

to 5-wollastonite. The diffi'action peaks, liowever, shift to the bustamite side

due to Fe2' substitution for Ca in the B-wollastonite structure and it may

become difficult to determine whether the structure of･the phases present

belongs to 6-woilastonite or to bustamite when 6-wollastonitess contains

considerable amounts of Fe2'.

The crystalline material of composition CaFe2"Si2 06 was prepared at fo,

of lcrii and IOmiO atm to examine whether these two phases are mutually

distinguishable or not. Figs. I and 2 show the changes of d-spacings of(204) as

a function of temperature. Only one peak corresponding to that of bustamite

THE SYSTEM NaFe3'Si2 06 -CaFe2'Si2 06 49l

Log Po2=-11 "CaFeSi2o6"

t7oo fXIxxllx

,,,,

el-XS-S-iXXGs'h`l"xx:l)iitti,,

1.600 FeBuigs-Was+L

b･Fel.vo,g

: Fe B.u S

l wws,Ll

l!

I-I-nvslxl-I-I

.nQF.e,w.e,ss i

l

Ixl-a-FeVtoss.n-FeWoss,WUs.L

;1 OO 11 50 1200 o1250 C

1.700

1.650

1.600

I Log Po2=-11 "Acio-Hdgolllllllllllllll'lllllXlvV-l

:

tt

IIxl

FeBusss.W"s+L

k･fewo,S

aFeelssst

lWU'5,Ll

ll

I I-xl?.":",W.2ss

I a-FeWessI :B.L,f,eW.,Oss

::

Fig. 3

o 1100 1150 1200 1250C Temperature

Change of refractive indices of 6-Fe-wollastonitess and Fe-bustamitess crystallized

from the compositions of CaFe2'Si206 and AcioHdge at IOMii atm fo2.Abbrevations are same as in Fig. 1.

was observed and the d-spacing increases with increasing temperature between

1lOOOC and 1l750C. The peak of (2e4) splits at 1i80 and l1850C, giving two

different d-spacings. One is similar to the d-spacing of 6-wollastonite and the

other to that of bustamite. However, at higher temperatures again only one

peak was observed, which gave a d-spacing similar to that of 6-wollastonite

(Figs. I and 2).

Optical methods are also useful to identify the si}icate phases encountered.

Two silicate phases A and B were observed in the ruR charges of the

492 I<. Ohta, K. Onuma and K. Yagi

I Log po2=-io . .i-7 00 1/ -ixi , Ca Fe Si2o6

t650

1.600

iXxx

FeBusss.Fe-ox[de.L

1100

×KI'xlvl-- a IXIvi-- ---l-HKI XI- ---I-I-I----Ns--Ih--Ns-I-

.?.'Fae.:"//s:ln-Fewassl .::FF.""bUe;.s

`WUs.L .yv"s-L i d r ,Wss.L LIl cli Ld1 ,･･L11 50 1200 nso a c

i7oo I

1,650

L600

Log Po2=-ulO

lXiIxlxXXxXII

FeBusss.Fe-oxide.L

"Acio-Hdgo"

r×}-I--

×-I-. al-I l-Ixl II I-Ixl i.fiEeFSV:s5sSi n-Fewoss l .:JFFeewWeess:

.W"s.t d.WUs.L, i ,WUs.L tl/ di/ didFig. 4

e llOO 1150 1200 1250C Ternperature

Change of refractive indices of 6-Fe-wollastonitess and Fe-bustamitess crystaliized

from the compositions of CaFe2'Si206 and AcioHdgo at' iO-iO atm fo2.Abbrevations are same as in Fig. 1.

composition of CaFe2'Si206 at ll800C and 11850C and also that ofAcioHdgo at 1l7SOC. These two phases sliow different refractive indices as

follows: A-phase or = 1.628 ± O.O03, 7= 1.642 ± O.O03; B-phase a = 1.647 ±

O.O03, 7 = 1.662 ± O.O03. The A-phase was not encountered below theseteinperatures and the B-phase disappears above these temperatures. Coinparing

with the X-ray data it is evident that the A-phase corresponds to the6-wollastonite structure and the B-phase to the bustamite structure.The changes

of refractive indices as a function of temperature are given in ITigs. 3, 4, and S.

If the 6-wollastonitess changes in cornpositioA while maintaing its structure, the

d-spacing and the refractive indices should change continuously. However, as

seen in Figs. I, 2, 3, 4, and 5, the changes of these values are discontinuous,

indicating that there should be some change in the structural state. The

obseivations mentioned above lead to the following conclusion: the phase with

THE SYSTEM NaFe3'Si2 06 -CaFe2'Si2 06 493

l

1.7oo e

1.650

1.600

Log Po2=-9

"CaFeSi206" INXI r IXIXXL-m ------ a I---- mm""I IXIx -'T-I I-NIx Add 4 n-FeWess , d fi-FeWoss i a-FeLYess FeBusss.Mt.L +Feeusss , i +Fe-oxide i +n-FeWoss .Mt+L , i ,L i .W"sd 4il bbi il tL.

1100 11 50 1200'-""rmt'-""'-

o 1250 C

i7oo I

1.650

1600

LogPo2=--9

lilllll5

a

d-

Acio " Ncigo

IL}}

i-

FeBtisss+Ml.L

{XI･------INIi? gBW2gt:sl B-Fewo,s

.Ut+LUMt.L l

IIII

I a-FeWess::"F.Jg-e.W,,O-ds.s

:,Ll

Fig. 5

o llOO 1150 1200 1250C Tefnperature

Change of refractive indlces of a-Fe-wollastonitess and Fe-bustamitess crystallized

from the compositions of CaFe2'Si206 and AcioHdgo at 10-9 atm fo2.Abbrevations are same as in Fig. 1.

low refractive indices and larger d-spacing has 6-wollastonite structure, whereas

the phase with high refractive indices and smaller d-spacing is presumed to have

bustamite structure.

Rutstein (1971) fotmd that bustamite with composition between(Cao.gFeo.i)Si03 and (Cao.sFeo.2)Si03 shows a split in the peaks of X-ray

diffraction patterns, indicating the presence of two phases. He also distingushed

these two phases by infrared spectral analyses and concluded that these two

phases correspond to the structures of 6-wollastonite and bustamite, althougli

their optical properties were not giveR. Matsueda (1973) found the natural

mineral to have different structure from 6-wollastonite and called the structure

of this mineral "iron wollastonite structure" which corresponds to the

bustamite investigated by Rutstein. Since in the present study the presence of

494 K. ohta, K. onuma and K. Yagi

B-wollastonite structure including Fe2' is recognized in addition to or-

wollastonite and bustamite structures, it is not proper to use the term "iroR

wollastonite" for the mineral which has a bustamite structure.

IR the present investigation, therefore, the three phases mentioned above

are called a-Fe-wollastonitess, 6-Fe-wollastonitess and Fe-bustamitess, because

X-ray diffraction patterns are shifted from the pure compounds, indicating that

Fe2" is incorporated iR the structures. Since there is some confusion concerning

the structural states of these phases according to different workers, the

Aomenclature is compared in Table l.

TabEel The structural states of or-Fe-wollastonite, B-Fe-wollastonite, and

Fe-bustamite by different workers.

Phasepresentinthisstudy Structuralstates

Rutstein(1971) Matsueda(1973)

cr-Fe-wollastonite - -B-Fe-wollastonite B-woNastonite 6-wollastonite

Fe-bustarnite bustamite ironwollastonite

Under the microscope the Fe-bustamitess forms nearly equant plates at

lower temperatures and slender plates or prisms at higher temperatures, both

being about O.04 - O.Ol mm in length. The 6-Fe-wollastonitess forms slender

piates or prisms, about O.04 - O.Ol mm in length. Both of them are pale green

and non-pleochroic. The or-Fe-wollastonitess forms equant plates or squares,

about O.02 - O.04 mm in size. Pleochorism is distiiict as follows: X' = colorless,

Z' =: pale green. The or-wollastonitess is distinguished from the other phases by

its high birefringence. In addition to the silicate phases very small amounts of

oxide minerals, magnetite and wUstite, are preseAt throughout all runs.

Phase diagrams

Results of quenching experiments for the oxygen fugacities IO-i i, IO-'O

10-9 atm are listed iR appendices 1, 2, and 3 with refractive indices of the

silicate minerals, and the phase diagrams for each of the isobaiic sections are

shown in Figs. 6, 7, and 8. The transition boundary of wUstite and magRetite is

calculated from the data of Darken and Gurry (1945) to locate # at 11430C at

10-'O atm and l2700C at 10-9 atm.

At 10-' ' atm fo, , the following assemblages were encountered with falling

temperature: or-Fe-wollastonitess + w"stite + Iiquid, or-Fe-wollastonitess +

6-Fe-wollastonitess + wUstite -t- liquid, B-I?e-wollastonite + wUstite + liquid,

6-Fe-wollastonitess + Fe-bustamitess + wUstite + liquid, and Fe-bustamitess +

THE SYSTEM NaFe3'Si2 06 -CaFe2"Si2 06 495

x

Log Po2= --11

x

o

L

x

o

o

xe

xe

xao

a-FeWess.WUs.L

s

o

a-f"Wess-fi-feVtoss.W"s,L

e

oo

oo on-FtWoss.W"s.t

o o

o"o

eae o

g

o

e

o

o

o

e

o

a

o

F"Eusss.W"s.L

v

n-kWess.FeBusss.W"s.L

n o

'ce 1250

e

? 1200

o

e :t:･ N x E fl

n t150

o

o llO･:i

NaFeSi206 30 40 so

Fig.6 Phase diagram of the system Abbrevations are given in Fig. 1.

6o 7o 80 90 CaFeSi206 mot el.

NaFe3'Si206-CaFe2'Si206 at 10-ii atm fo2.

wtlstite + liquid. In the sections with fo, of 10m'O and 10-9, the same

assemblages were confirmed, except that wthstite converts to magnetite at lower

temperatures.

In each section it is observed that the upper stability of each phase

assernblage increases with increasing CaFe2'Si2 06 and also that the stability

field of each assemblage increases with decreasing fo, . On the other hand, the

liquid field extends towards CaFe2'Si2 06 with increasing fo, ･

Since the present system is a join of a five-component system, Na2 O-CaO-

Fe-O-Si02 , the iso-fugacity T-X section is not binary, but pseudo-binaiTy. When

the composition is projected from the oxygen apex onto the Fe-Si02 line,

magnetite and wUstite are compositionally coincident, so that the system is

treated as a four-component system in the analysis of phase assemblages (see

Lindsley et al., 1968). Therefore, a five-phase assemblage is univariant and a

four-phase assemblage is divariant. In the 10mi' atm section two divariant

assemblages are present, B-Fe-wollastonitess + Fe-bustamitess + wtlstite + liquid

aiid or-Fe-wollastonitess + 6-Fe-wollastonitess + wUstite + liquid. In the 10miO

atm and IO-9 atm sections, the magnetite-wUstite inversion curve appears and

496 K. Ohta, K. Onuma and K. Yagi

Log Po2=-1O

L

x

xoo

x

xOoo

oo a-FeWOssWUs.L

G e

a-FeWoss.n-FeWess.Wdis,L

o

fi-FeWess.FeBusss.Wes.L

o

n-FeWoss.WUs.L

o

o

a

o

]

a

FeBusss.WUs,L

n

e co 1.250

e

o 1200

An.

a 1150

2aatLgEs

x

FeSusss.Mt.L

di eR el e s:t FiWeSS /B Fewoss FeBvsssMt L

e fi " m e za

M

e 1100

Fig. 7

NaFeSi206 40 50

Phase diagram of the systemAbbrevations are given in Fig. 1.

6o 7o 80 90 CaFeSi206 mo l elo

NaFe3'Si206-CaFe2'Si206 at IOrmiO atm fo2.

crosses the divariant assemblage fields mentioned above, resulting in the

presence of univariant assemblages: 6-Fe--wollastonitess + Fe-bustamitess +

wUstite + magnetite + liquid (10MiO) and or-Fe-wollastonitess + 6-Fe-

wollastonitess + wC}stite + magnetite + liquid. Therefore, the univariant curve

indicating these two assemblages lias a pesitive slope in the T-fo, prQjection

aiid must lie on the magnetite-wUstite inversion plaiie which is independent of

the composition in the T-X-fo, space. These two univariant curves meet

together at an invariant point where or-Fe-wollastonitess, 6-Fe-wollastonitess,

Fe-bustamitess magnetite, and wt'istite coexist with liquid.

When Fe3' is not present at low fo2 , say 10" i, sodium can not enter iiito

the crystalline phases in the form of NaFe3'Si2 e6 , but all of this molecule is

contained in the liquid. However, when magnetite is present, indicating the

existence of Fe3', it is possible that sorne of the Fe3', in the form of

NaFe3'Si2 06 , can be incorporated in the silicate phases and the remainder is

contained in the liquid. The amount of Fe3' in the silicate phases may increase

THE SYSTEM NaFe3'Si2 06-CaFe2'Si2 06 497

Log Po2=-9 x

x

･w:I.reLW

o a-feWess.n-FeWoss.W"s+L

I"c

l250

e

L

x

xe

x di m

XM ts N

e e el200a-FeYVoss.B-FeWoss.Mt.L

/Te

fi-FeWoss.Mt.L

e

m

m

as

FeBusss.Mt,L

m

S-FeWess.FeBusss.Mt.L

e ee

e

za 1150

ee

m "od

o..iEI

NxgN

NaFeSi206 40 50 6o

Fig.8 Phase diagram of the system Abbrevations are given in fig. 1.

7o so 90 CaFeSi206 mo l Olo

NaFe3'Si206-CaFe2'Si206 at IO-9 atm fo2.

with decreasing amount of liquid and finally a complete series of solid solutions

between NaFe3'Si2 06 and CaFe2'Si2 06 is formed at subsolidus ternperatures

as demonstrated by Ohashi (i976).

Application to natural pyroxene

The present experimental evidence supports the former conclusion ofYagi

(1966) that at low fo, the pyroxene trend proceeds from diopsidic towards

hedenbergitic and at high fo, from diopsidic through soda augite to aegirtne.

Recently Ewart et al. (1976) called attention to the fact that acmite-enrich-

ment occurs oRly after extreme Fe-enrichment and not only fo, but activity of

alumina in liquid plays an important role in detennining the courses mentioned

above. The presence of the acmite molecule in pyroxene also depends upon the

concentration of calcium in the liquid. From their experimental studies Onuma

and Yagi (1975) and Yoshikawa and Onuma (197S) suggested that at high fo,

498 K. Ohta K. Onuma and K Yagi

when enough calcium and aluminum are present Fe3" enters into pyroxene in

the form of CaFe3'AISi06 and sodium forms nepheline, also that pyroxene

proceeds towards acmite only when Na > Fe3' + Al, as pointed out by

Huckenholz (1973) in his study of natural pyroxene.

The above statement leads to the following conclusion: When fo2 is higher

than the magnetite-wtstite transition curve, pyroxene becomes acmitic in the

case of Na > Fe3' + Al, or fassaitic in the case of Na < Fe3' + Al; when fo, is

lower than the magnetite-wUstite curve, it becomes hedenbergitic in either case.

Acknowleclgements The authors' thanks are due to Mr. Haruo Ohashi ofthe National Institute

for Research in IRorganic Materials for his help in the experimental technique,

aRd Dr. N.C. Stevens of University of Queensland for his cr#ical reading of the

paper in manuscript. Part of the cost for the present study was defrayed by

Grant for Scientific Research from the Ministry of Education of Japan, and a

grant from the Mitsubishi Foundation.

References

Bowen, N.L., J.F. Schairer, and E. Posnj.ak, l933. The system CaO-FeO-SiO?. Am. J, Sei.,

26: l93-284.Darken, L.S. and R.W. Gurry, l945. The system iron-oxygen. I. The whstite field and related

equibria. J. Am. Chem. Soc., 67: l398-l412.Ewart, A., A. Mateen and J.A. Ross, l976. Review of mineralogy and chemistry of Tertiary

central volcanic complexes in southeast Queensland and northeast New South Wales.

Vblcanism in Australasia, Ed. by R.W. Johnson, 21-39.Huckenholz,1 .G. I973. The origin of fassaitic augite in the alkali basalt in suite of the

Hocheifel area, Western Germany. Contr. Min. Pet., 40: 3l5-326.

Lindsley, D.H., D.H. Speidel and R.H. Nafziger, 1968. P-T-fo relation for the system

Fe-O-Si02.Am. L Sci., 266: 342-360.Matsueda, H.,i973. Iron-wollastonite from the Sampo mine showing properties distinct from

those of wollastonite. Mineral. J., 7: l80-201.

Nolan, J., 1969. Physical properties of synthetic and natural pyroxenes in the system

diopside-hedenbergite-acmite. Mineral. Mag., 37: 2l6r229.

Ohashi, H., 1967. The systern acmite-hedenbergite. M. Sc. Thesis Hokkaido Univ. (in

Japanese).Onuma, K. and K. Yagi, 1975. Thejoin CaMgSi2 06-CaAl2 Si06-CaFe3"AISi06 in air and its

bearing on fassaitic pyroxene. J, Eac. Sci., HOkkaido Uhiv., Ser. 4, l6: 343-356.

Peacor, D.R. and C.T. Prewitt, 1963. Comparison of the crystal structures of bustamite and

wollastonite. Am. Mineral., 48: 588-596.Prewitt, C.T. and D.R. Peacor, 1964. Crystal chernistry of the pyroxenes and pyroxenoids.

Am. Mineral,, 49: 1527-1542.Rutstein, M.S., 1971. Re-examination of the wollastonite-hedenbergite (CaSi03-CaFeSi2 06)

499 THE SYSTEM NaFe3'Si2 06 -CaFe2'Si206

equilibira. Am. Mineral., 56: 204e-2052.Rustein, M.S. and W.B. White, l971. Vibrational spectra of high-calcium pyroxenes and

pyroxenoids. Am. Mineral. 56: 877-887.Yagi, K., l966. The system acmite-diopside and its bearing on the stability relations of

natural pyroxenes of the acmite-hedenbergite-diepside series Am. Mineral., 51:'

976-IOeO.Yoshikawa, K. and K. Onuma, 1975. The join NaFeSi206-CaAl2Si06 at 1 atmospheric and high pressure: Part I. Phase relations at 1 atm pressure in air. J. lapan. Assoc. Min.

Pet, Econ. Geol., 70: 335-346.

(Received on Oct. 21, 1976)

soe

Appendix 1

K. Ohta, K. Onuma and K. Yagi

Results of quenching experiments for the system

CaFel2Si206 at 10-'i atm fb, and refractivepyroxenoids.

NaFof3Si206 -indices of the

Compositioll (mol %)

Ac HdTemp. (oC) Phases

Reftractive indices

(±O.O03)

or7o

le

20

100

90

se

1100

1125

1150

1175

1180

1185

1195

l2eo

1225

1250

1100

1125

ll50

1165

1175

1185

ll95

12oe

1225

125e

lleo

1125

1150

1165

ll75

1195

noe

1225

1250

Fe-bus÷wtis+gl

Fe-bus+wtis+gl

Fe-bus+wifs+gl

Fe-bus+wtis+gl

6-Fe-wo+Fe-bus+wiis+gl

6-Fe-we+Fe-bus+wifs+gl

6-Fe-wo+whs÷gl

6-Fe-wo+wiis+gl

a-Fe-wo+B-Fe-wo+wUs+gl

a-Fe-wo+B-Fe-wo+wUs+gl

Fe-bus+wiis+gl

Fe-bus+whs+gl

Fe-bus+w"s+gl

Fe-bus+wtis+gl

B-Fe-wo+Fe-bus+wUs+gl

6-Fe-wo+wiis+gl

B-Fe-wo+wifs+gl

6-Fe-wo+wiis+gl

or-Fe-wo+B-Fe-wo+wUs+gl

a-Fe-wo+wiis+gl

Fe-bus+wtis+gl

Fe-bus+wtis+gl

Fe-bus+wtis+gl

6-Fe-wo+Fe-bus+wUs+gl

6-Fe-wo+wtis+gl

B-Fe-wo+wus+gl

or -Fe-wo+fi -Fe-wo+wtis+gl

a-Fe-wo+B-Fe-wo+wUs+gl

or-Fe-wo+wiis+gl

1.685

1.680

l.673

1.654

L6511.628

1.650

l.628

1.626

1.627

l.625

l.609

1.624

1.609

1.675

1.666

1.655

1.650

1.649

1.628

1.626

1.626

1.626

1.624

1.609

1.609

1.658

1.655

1.649

1.647

1.628

1.626

1.625

1.622

1.610

l.623

1.609

1.609

1.705

1.700

l.688

1.669

1.664

1.642

1.663

1.641

l.640

l.641

1.638

L6521.638

L653

1.691

1.683

1.669

1.664

1,662

1.642

1.640

1.64e

1.640

1.638

1.653

1.654

1.674

1.669

1.663

L6621.642

1.640

1.639

1.636

1.653

1.636

1.653

1.653

Fe-bus

Fe-bus

Fe-bus

Fe-bus

Fe-bus

6-Fe-wo

Fe-bus

6-Fe-wo

B-Fe-wo

6-Fe-wo

6-Fe-wo

or-Fe-wo

6-Fe-wo

or -Fe-wo

Fe-bus

Fe-bus

Fe-bus

Fe-bus

Fe-bus

B -Fe-wo

6-Fe-wo

6 -Fe-wo

6 -Fe-wo

B-Fe-wo

cr -Fe-wo

or-Fe-wo

Fe-bus

Fe-bus

Fe-bus

Fe-bus

6-Fe-wo

6-Fe-wo

5-Fe-wo

B-Fe-wo

a-Fe-wo

6 -Fe-wo

or-Fe-wo

cr -Fe-wo

T正｛ESYST君M　NaFe3＋Si206・CaFe2＋Si206

　　　　　　　Appe薮db【1（continued）

Colnpbsitioll

　　（mol％）

Ac　　　Hd

Temp．（OC）

PhasesRe負ractive　indices　　　（±0．003）

　　α　　　　7

30

35

40

45

50

60

70

70

65

60

55

50

40

30

1100

1125

1150

1175

U95

1225

1250

1125

1185

1200

1225

1250

1100

1125

1150

1175

1185

1200

1225

1100

1175

1200

1100

1125

1150

1175

1100

1125

1100

Fe－bus＋wOs＋gl

Fe－bus＋w丘s＋gl

β一Fe－wo＋w昼s＋gl

β一Fe－wo＋wUs＋9董

α一Fe－wo＋β一Fe－wo＋w麺s＋gl

α一Fe－wo÷wUs＋gl

α一Fe－WO＋wUS＋gl

β一Fe－wo＋Fe－bus＋wUs＋gl

β一Fe－wo＋wUs＋gl

α一Fe－wo＋β・Fe－wo＋w酋s＋gl

α一Fe－WO＋W麺S＋gl

91

Fe－bus÷輔s÷gl

β＋Fe－wo＋w鷲s＋91

β一Fe－wo＋wUs＋gi

β一Fe－WO＋W昼S＋gl

β一Fe－wo＋wUs＋9韮

α一Fe－wo÷β一Fe－wo＋wOs＋9蓋

gi

β一Fe－wo＋Fe－bus＋w通s＋9董

β一Fe－wo＋w種s＋9正

gl

β一Fe－WO＋W已S＋gl

β一Fe－wo＋w態s＋gi

β一Fe－WO＋W睦S＋gl

9隻

β一Fe－wo＋w礒s＋gl

9藍

麟

互．655

1．652

1．626

1．622

1．622

1．609

1．609

1．609

L648

1．628

1．625

L623

1．609

L610

L652

1．626

L624

1．624

1．624

1．621

1．610

1．649

1．627

1。624

1．627

1．625

1．623

1．623

正．668

1．665

1．639

L634

互．636

1．654

L653

互．652

正．662

1．642

1．639

1．636

1．653

1．653

1．666

1．640

L638

1．637

1．638

1．635

1．653

1．663

1．641

1．636

1．640

1．638

1．634

1．636

Fe－bus

Fe－bus

β一Fe－w・

β一Fe－wo

β一Fe－wo

α一Fe－wo

α一Fe－WO

α一Fe－wo

Fe－bUS

β一Fe－WO

β一Fe－wo

β一Fe－wo

α一Fe－WO

α一Fe－wo

Fe－bus

β一Fe－wo

β一Fe－w・

β一Fe－wo

β一Fe－wo

β一Fe－WO

α一Fe－wo

Fe－bus

β一Fe－wo

β一Fe－w・

β一Fe－w・

β一Fe－WO

β一Fe－wo

β一Fe－wo

Abbrevations　ale　g｛ven　in　Fig。1．

501

502

Appendix 2

K. Ohta, K. Onuma and K. Yagi

Results of quenching experiments for the system

CaFof2Si206 at 10-iO atm fo, and refhractiye

pyroxenoids.

NaFe'3Si206 -indices of the

Composition (mol %)

Ac HdTemp. (oC) Phases

Refhractive indices

(±o.eo3)

or7o

IO

20

30

100

90

80

70

1100

1125

1150

l165

1175

1185

1190

1200

1225

l250

1100

1l25

115e

1165

1175

l185

1200

1225

l250

neo1l25

1150

noe

1225

125e

11eo

l125

l150

1190

Fe-bus+mt+gl

Fe-bus+mt+gl

Fe-bus+w"s+gl

Fe-bus+wUs+gl

Fe-bus-w"s+gi

B-Fe-wo+Fe-bus+w"s+gl

B-Fe-wo+wus+gl

B-Fe-wo+wus+gl

or-Fe-wo+B-Fe-wo+wUs+gl

a-Fe-wo+B-Fe-wo÷wiis+gl

Fe-bus+mt+gl

Fe-bus+mt+gl

Fe-bus+wUs+gl

6-Fe-wo+Fe-bus+wiis+gl

5-Fe-wo+Fe-bus+wUs+gl

6-Fe-wo+wus+gl

6-Fe-wo+wiis+gl

or-Fe-wo-+z(3-Fe-wo+wiis+gl

or-Fe-wo+wtis+gl

Fe-bus+mt+gl

Fe-bus+mt+gl

6-Fe-wo+Fe-bus+wiis+gl

or-Fe-wo+B

-Fe-wo+wifs+gi

or-Fe-wo+B-Fe-wo+wlis+gl

or-Fe-wo+wiis+gl

Fe-bus+mt+gl

Fe-bus+mt+gl

6-Fe-wo÷wus+gl

P-Fe-wo+wUs+gi

1.683

1.674

1.667

1.653

1.650

1.648

l.629

1.628

1.628

l.627

1.6e9

1.623

1.609

1.670

l.663

L6551.649

1.628

1.649

1.628

1.626

1.626

1.625

1.609

l.609

1.655

1.651

1.648

1.629

1.621

1.609

1.623

L6091.609

1.654

1.650

1.626

l.622

1.7eo

1.691

L681

1.667

1.664

1.663

1,642

1.641

l.641

1.640

1.653

L636

1.652

L6831.678

1.669

l.663

1.641

1.662

l.641

l.640

1.639

L6381.653

1.652

1.669

l.665

1.662

1.642

l.638

1.654

1.636

1.653

1.653

1.658

l.664

1.640

1.636

Fe-bus

Fe-bus

Fe-bus

Fe-bus

Fe-bus

Fe-bus

B-Fe-wo

B-Fe-wo

6 -Fe-wo

B-Fe-wo

a-Fe-wo

6-Fe-wo

cr -Fe-wo

Fe-bus

Fe-bus

Fe-bus

Fe-bus

B-Fe-wo

Fe-bus

6-Fe-wo

6-Fe-wo

6-Fe-wo

6-Fe-wo

or -Fe-wo

a-Fe-wo

Fe-bus

Fe-bus

Fe-bus

6-Fe-wo

6-Fe-wo

a-Fe-wo

B-Fe-wo

or -Fe-wo

a-Fe-wo

Fe-bus

Fe-bus

6-Fe-wo

6-Fe-wo

THE SYSTEM NaFe3"Si2 06 -CaFe2"Si2 06

Appendix 2 (continued)

S03

Composition (mol %)

Ac HdTemp. (oC) Phases

Refractive indices

(±e,oo3)

a7

35

40

45

50

6e

65

60

55

50

40

1200

1225

1125

1175

119e

1200

1100

i125

1150

1175

11eo

1150

1100

1125

1150

1100

or-Fe-wo+6-Fe-wo+wiis+gl egl

gi

6-Fe-wo+Fe-bus+mt+gl

6-Fe-wo+wUs+gi

6-Fe-wo+wiis+gl

gi

Fe-bus+mt+gl

6-Fe-wo+mt+gl

6-Fe-wo÷wus+gl

gl

B-Fe-wo+Fe-bus+mt+gl

6-Fe-wo+wgs+gl

B-Fe-wo+mt+gl

5-Fe-wo+mt+gl

gl

gl

1.620

1.609

1.648

1.628

1.624

1.622

1.650

1.626

-1.623

1.648

1,627

1.622

1.623

1.622

1.634

1.653

1.662

1.642

1.637

1.636

1,664

L6401.636

1.662

1.642

1.635

1.635

1.635

6-Fe-wo

a-Fe-wo

Fe-bus

6-Fe-wo

6 -Fe-wo

B-Fe-wo

Fe-bus

6-Fe-wo

6-Fe-wo

Fe-bus

B-Fe-wo

6-Fe-wo

B -Fe-wo

6-Fe-we

Abbrevations afe given in Fig. 1.

504

Appendix 3

K. Ohta, K. Onuma and K. Yagi

Results of quenchlng experiments for the system

CaFe'2Si206 at 10r9 atm fo, and refra¢tivepyroxenoids.

NaFe'3Si206 -indices of tlie

Composition (mol %)

Ac HdTemp. (oC) Phases

Refractive indices

(±o.eo3)

a7o

10

20

3e

35

40

45

100

90

80

70

65

60

55

1100

l125

1150

1175

l185

1200

1225

ilOO

1125

1150

ll75

1200

1225

1250

llOO

1125

l150

1175

l200

l225

1100

1125

i150

1175

1100

1l25

l150

1100

1l25

1100

Fe-bus+mt+gl

Fe-bus+mt-gl

Fe-bus+mt-gl

Fe-bus+mt-gl

6-Fe-wo+mt+gl

6-Fe-wo+mt+gl

or-Fe-wo+6-Fe-wo+wUs+gl

Fe-bus+mt+gl

Fe-bus+mt+gl

Fe+bus+mit+gl

6-Fe-wo+Fe-bus+mt+gl

6-Fe-wo+mt+gl

a-Fe-wo+wtis+gl

gl

Fe-bus+mt+gl

Fe-bus+mt+gl

6-Fe-wo+Fe-bus+mt+gl

6-Fe-wo+mt÷gl

a-Fe-wo+6-Fe-wo+mt+gl

gl

Fe-bus+mt+gl

6-Fe-wo+Fe-bus+mt+gl

B-Fe-wo+mt+gl

gl

B-Fe-wo+Fe-bus+mt+gl

B-Fe-wo+mt+gl

gl

6-Fe-wo+mt+gl

gl

gl

1.671

1.666

l.650

l.626

1.624

1.623

1.608

1.666

1.659

1.651

1.647

1.627

1.625

1.609

l.655

1.653

1.647

1.627

l.627

1.625

1.6e9

l.650

1.648

1.627

`1.628

1.647

l.628

l.625

1.623

1.687

1.680

L6651.640

L6381.636

1.653

1.680

1.672

1.666

1.662

1.641

1.638

1.653

l.668

1.666

l.661

1.640

1.640

l.638

1.651

1.664

1.662

1.641

1.641

1.664

1.642

1.638

1.636

Fe-bus

Fe-bus

Fe-bus

B-Fe-wo

B -Fe-wo

B-Fe-wo

or-Fe-wo

Fe-bus

Fe-bus

Fe-bus

Fe-bus

6-Fe-wo

6-Fe-wo

or-Fe-wo

Fe-bus

Fe-bus

Fe-bus

B-Fe-wo

B-Fe-wo

B -Fe-wo

or -Fe-wo

Fe-bus

Fe-bus

B -Fe-wo

B-Fe-wo

Fe-bus

B-Fe-wo

B -Fe-wo

6-Fe-wo

Abbrevations are given in Fig. 1.