THE AMERICAN MINERALOGIST, VOL. 56, NOVEMBER_DECEMBER, 1971

ADDITIONAL DATA ON FERROCARPHOLITE FROMSULAWESI (CELEBES), INDONESIA

W. P. oB Roovnn, Geologi.cal Institule, Universily oJ Amsterdam,l{ieuwe Prinsengracht 130, Amsterdam, The Netheilands

AND

C. Krnnr, l{etherland,s Organization for the Ad,aancement of PureResearch (Z.W.O.), Working Community Jor Analytical Chemical

Research of M'inerals and Rocks (W.A.C.O.M.), cf o FreeUniaersity, Institute oJ Earth Sciences, De Boelleaan 1085,

A msterdom- I 1. T he N etherlands

ABSTRACT

Four electron microprobe analyses are given of ferrocarpholite, (Fe, Mg)Ah(OH)rSizOo'

a mineral chemically similar to chloritoid+quartz+water and probably a high-pressure/

Iow-temperature equivalent of this assemblage in part of the glaucophane-schist facies and

the lawsonite-albite facies. There is complete miscibility between divalent iron and mag-

nesium in the range between the atomic ratios 0.82s:0.16s and 0.55:0.43, with concomitant

variation of the refractive indices and the ontic axial anqle.

INrnooucrtoN

Ferrocarpholite, FeAI2(OH)4Si2O6, was first described by the senior

author (W.P.de Roever, 1951). I t is the ferrous i ron analogue ofcarpholite proper, which contains manganese as the main divalent ele-ment. According to a crystal structure analysis by Caroline H. MacGil-lavry et al. (1956), ferrocarpholite is an inosilicate with (Siot,-chains

very similar to those found in the pyroxenes.In 1951 virtually manganese-free material with optic characteristics

very near to those of carpholite was recognized in three samples collectedin eastern central Sulawesi by the late Dr. W. H. Hetzel, member of the1929 Celebes Expedition of the Netherlands Indies Geological Survey,and by its leader Prof. H. A. Brouwer. In the only sample that containedenough material for wet-chemical analysis according to conventionalmethods, the ferrocarpholite appeared to be represented by a magnesianvariety with the atomic ratio Fe2+: Mg: Mn:0.79s:0.20:0.005; this sam-ple (no. 15-161*) was taken from a cobble of vein-quartz west of thevil lage of Tomata (Fig. 1). Electron microprobe analyses of the ferro-carpholite in the two other samples as well as of material erroneouslydescribed as carpholite in an earlier paper by W. P. de Roever (1947,

p. 103-105), have now been performed by Kieft.

Monn oF OccURRENCE

All three samples were taken from exposures of solid rock. In sample

F ERROCA RP HOLI T E FROM I N DON ES I A

Frc. 1. Ferrocarpholite localities in Sulawesi, indicated by sample numbers.

17-47*, a blastopsammitic sericite-qxartzite collected east of Tamond-jengi, north of the trail to Majumba, the mineral is also found in qvartz-veins. In a metaconglomerate collected southwest of Peleru on the trailto Majumba (no. 17-42), it occurs as a rock-forming mineral in themesostasis between the original pebbles, whereas in a blastopsammiticschistose ferrocarpholite-quartzite from the S. (Solo: river) Musori(no. 16-30*) it is the main constituent of gray-green schistose layersalternating with iayers colored red by hematite. AII samples have beendescribed rather elaborately in a previous paper by W. P. de Roever(1947, p. 103-1 11, 152-154).

Besides qtartz, colorless mica, and hematite, the accompanying min-erals are chlorite, leucoxene, ruti le, tourmaline, zircon, and (?)biotite.The metamorphism shown by the rocks and causing the parallel arrange-ment of the ferrocarpholite crystals in sample 16-30* is thought to be ofYounger Mesozoic or Tertiary age, as it also affected radiolarian chertsand spilitic rocks considered to be of Mesozoic age. The main phase ofthis metamorphism was in the glaucophane-schist facies (Eskola's origi-nal nomenclature is preferred since common natural iron-bearing

r977

r d E \

\I

\I

\I\II

r b l i;r; l ii 3 i : !

r978 W. P. DE ROEVER AND C. KIEFT

glaucophane requires considerable pressure for its formation, as law-

sonite does, see de Roever, 1967 ;1970). It could not be definitely deter-

mined whether the ferrocarpholite was produced during metamorphismin this facies, or during slightly younger or older metamorphism in the

green-schist facies, or in a facies characterizedby the plentiful production

of pumpellyite and actinolite apparently corresponding to Hashimoto's(1966) pumpellyite-actinolite-schist facies, or, more roughly, to the

prehnite-pumpellyite-metagraywacke facies. According to its rather

wide distribution (Fig. 1) and rather coarse grain-size' however, the

ferrocarpholite is most probably a product of metamorphism in theglaucophane-schist facies. Lawsonite, and jadeite accompanied by quartz(de Roever, 1955) have been found in a sample (no. 16-4") collected at a

distance of a few kilometers from the ferrocarpholite locality east of

Tamondjengi. For the subfacies of the glaucophane-schist facies occur-

ring in the area under consideration, which subfacies is characterized by

the absence of epidote and garnet, the name lawsonite-glaucophanesubfacies may be used (or lawsonite-glaucophanite subfacies as sug-

gested by W. P. de Roever in 1947).The only other part of the world where ferrocarpholite has been

found subsequently is Calabria, southern Italy (de Roever, de Roever,

Beunk, and Lahaye, 1967). There the bulk of the mineral l ikewise occurs

in quartz-bearing veins in an area also containing rocks with glauco-

phane, lawsonite, pumpellyite, aragonite, and jadeite (up to 80 percent

Jd) associated with qtrartz, in the wider surroundings of ScalBa and

between .scalda and Mormanno (see also de Roever and Beunk, to be

published). De Roever and Beunk came to the conclusion that the

ferrocarpholite of Calabria has been produced in part by metamorphismin the glaucophane-schist facies and in part by a metamorphism that

may best be described in terms of Winkler's (1965) lawsonite-albitefacies. A chemical analysis of a 98 percent-pure concentrate revealed

a much larger proportion of magnesium, the atomic ratios Fe2+:Mg:Mnbeing 0.55:0.43:0.02.

In hand-specimen ferrocarpholite resembles actinolite. Optically,however, it is rather easily recognized because of its parallel extinction

and especially because of the tourmaline-like orientation of its pleochro-

ism from yellow-green or green-yellow to very light blue-green or ex-

tremely light bluish green, with maximum absorption for vibrations nor-

mal to the elongation. It does not seem likely therefore, that the mineralhas often been overlooked.

Mrcnopnosp ANar-vsrs

Chemical analysis was performed with the aid of a Geoscan microprobe, with an ac-

celerating potential of 20 rv. Standards used were wollastonite for Si, corundum, synthetic

FERROCARP HOLITE FROM I N DON ESI A

TiO, Fe-metal, rhodonite for Mn, and olivine for Mg. For correcting mass-absorption andatomic number efiects a modified version of the computer progriun of Springer (1967) wasapplied. In this modified program the mass-absorption coefficients of Heinrich (1966) areused. The Fe3+/Fe2+ ratio was determined by reducing the sum of the cation ratios, calcu-lated on the basis of 8 O, to 5 and by compensating the resulting valence deficiency byassuming the presence of an appropriate amount of Fe3+. It is evident that inaccuracy ofthe analysis, especially in the Si-content, will result in errors in the Fe3+/Fez+ ratio.

The results of four new electron-microprobe analyses are given incolumns 1-4 of Table 1, together with the two previous analyses offerrocarpholite, made according to conventional methods (cols. 5 and 6).

All ferrocarpholites hitherto analyzed contain an insignificant propor-

Tsble 1. Micloprobe Amlyses of Fe$ocarphollt€ Fron Sul.aYeslCodpared tlith lhe Other Analyses 0f TtrLs i"llneral

1979

I'Ieight p€r cent

L 2 3

Atonlc ratLos

2 ) 4

sio2 )6.?Ar2ol 30.9'iio^ n.d.aoEl

Fe as

Feo L3"7

i'[no 0.2.)i lEO 4.?.- 2

TotaL .3

37.35 36.5 fi.6530.8 30.65 28.65(0.1 n.d. n.d.

15.5 17.0 19.8

0 .1 o" ) 0 .?

3 .9 2 .7 5

2 .0

87"65 87.2 87.3

s i L .995 2 .02 2 .OO 2 .03 2 .03 z .OL

f 1.e85 1,e65 1.e8 7.87

lil lllr"1 o.o2 o.oo5 0.015 o.o? o.o8j 0.06

F"4 0.605 0.6% 0.?6; 0.85 o.ati 0,5?

ILr 0.01 0.005 0.015 0.01 0.005 o.O?

rts o.)85 0.315 o.2z o.L? 0.205 0.45

Tots lo I 8 I I

v/)c/-

2v4

Bi!efrhgence

7 2

1.638 1.540

7.6T 7.6)6

7.5L7 1,.627

600 - 610 sjo - 5?o0.02L0.021 o.o19

7.643

1.639 - 1.640 (ca1c.)

7.624

) L - Y

0.019

L.647

f.&t+

1.628

49o

0.019 - 0.020

1. FerrocarpholLt€, E of T@ndjengl'r N of tlie trail to i'fajuba, eastem central SuJ.awesl.Indonesier fi,eld nwber l7 - 47x, ruseu tMb€r c 164, awrage of 9 neesre@nts @ 3 grairs.

Ferrocarphollt€, SW of Pelen on the trail to Hajuba, oast€m centaal sulewesi, Indonesls.fl€ld nurdcer 1/ - 42, nusem nub€r B )261. average of 5 rearuenents q 3 graixs.

FerrocerFhollt€, s. r,lusorL, on tlte tlall fr@ i,IoMt Jro to Artja. N of the S. 15.ro@i'east€rn central Sulasesl, Indonosia, fLeld nmber L6 - 3O,., nuseu nwtpr C 141r averageof I @aru@nts on @ln @os of 3 grairs. Optic constants deterrln€d ty F. F. Beuk.

Exttr@ vaLueE obtainod on mr!fl reh of no. 3 (imccuate aBhrsj.s dug to b8d [easulngconditlons witlrin tle v€in).

Ferrocalphollt€, cobble W of To@ta, €ast€m centrel Sularesi. Indonesla, fleLd nuber15 - 76Lx. ruseu nwber C 98, wet-chenical eElJEls accotdbg to convontioml @t}rods bythe rlaborat4rlw voor Delfstoffenonderzoek va d€ DLenst ru de lEjnbowt, Bandug(w. r . de Koever, ry)r j .

Felrocarphollt€ concentrat€, about 981 pu!e, large block ln trtbut rT of T. Saracem near5e Nlco1a Airolla, N of ScalBa. plovjrce of Cosenza, southem Italy (R 164), ret-chenlcslaBlysis accordhg to conventioml nettrods \r P. H. J. iahaye ( W. P. de Roever gg3l.,1%?).

1980 W. P. DE

\ l----N

\ zVo<

I 650

1 €43

t.640

r 635

n1.60

1 625

1 620

l6t5

o70 @3 0'60 065 090 095 16

Fe2 '

F"'z;. Ms. M;-

Frc. 2. Variation of refractive indices and optic axial angle with atomic ratio

Fe2+' (Fe2++Mg+Mn), ferrocarpholite from Sulawesi, Indonesia.

tion of Mn, the main variable being the ratio of divalent iron to mag-nesium. In carpholite proper, on the other hand, manganese is stronglydominant over either iron or magnesium. The results of the analysesindicate that ferrocarpholite shows complete miscibility of divalent ironand magnesium in the range between the atomic ratios 0.825:0.16a and0 .55 :0 .43 .

RBr.q.rrow or OprrcAL Pnoppnrrrs ro CEEMTcAL CoMposrrroN

The refractive indices as weli as the optic axial angle show a ratherregular variation with the chemical composition as illustrated by Figure2. An increase in the Fe2+:Mg ratio results in a gradual increase of theprincipal indices of refraction, and in a concomitant decrease of the optic

ROEVER AND C. KIDFT

+- eo"

#

so'\

\

FERROCARPHOLITE FROM INDONESIA 198I

axial angle. In magnesium-rich ferrocarpholites from Calabria currently

being investigated by F. F. Beunk, however, the optic axial angle seems

to be rather consistently 5o-10o lower than indicated in the diagram for

the ferrocarpholite from Sulawesi (oral communication).

RBrarroN To CHLoRrrorD

In view of the chemical similarity between ferrocarpholite and

chloritoid already recorded by W. P. de Roever et al,. (1967) and il lus-

trated by the equation

Fe2+Alz(OH)4Si2O6 : Fer+AlzO(oH)rsio+ + sio, * Hzolerrocarpholite chloritoid qtarlz water

the ranges of substitution in ferrocarpholite may be compared with

those in chloritoid described by Halferdahl (1961) (Table 2). The sim-

Tner,E 2. ReNcns or Suesrrrurrow rx FrnnocenpgolrrE AND Cnr-omroro

Ranges in percent

SubstitutionFerrocarpholite Chloritoid

Mg for Fez+

Mn for FeFFe8+ for Al

l6s-430 - 23 - 4

0-42u170-14

ilarity between these ranges indicates that this reaction may indeed

occur in nature. In this respect it is interesting to note that Fischer

(lg2g) concluded that carpholite from the Harz Mountains was formed

at the expense of ottrelite (see also Miigge, 1918).

Whereas ferrocarpholite is found in rocks showing a comparatively

low grade of metamorphism, chloritoid both in Sulawesi (W' P' de Roe-',r"r, 1956; and in Calabria seems to be restricted to slightly higher-grade

rocks, which would suggest that ferrocarpholite is a low-grade equivalent

of chloritoid (E.w.F. de Roever and Beunk, to be published). In view

of the wide range of temperatures found for the formation of rocks of

the glaucophane-schist facies by Taylor and coleman (1968) with the

aid of the 018/016 method-which implies that part of the glaucophane-

schist facies is a high-pressure equivalent of the greenschist facies-it

seems safer, however, to restrict our conclusion to the statement that

ferrocarpholite is probably a high-pressure/low-temperature equivalent

of chloritoid * quartz* water.

1982 W. P. DE ROEVER AND C. KIEFT

AcxnowlrnGuBNts

The authors are indebted to Prof. Brouwer for placing the material investigated at theirdisposal and to Messrs. F. F. Beunk and E w. F. de Roever for valuable assistance andsuggestions.

RnrBnnNcrs

Dn Ronvrn, E. w. F., exo F. F. BnuNr (1971) Ferrocarpholite associated with lawsonite-albite facies rocks near sangineto, calabria (southern rtary). Minerol, Mag. (in press).

Dn Ronwn, w. P. (1947) rgneous and metamorphic rocks in eastern central celebes. Gea-logi,col Erplorations in the Island. oJ cetrebes und.er the Leadership of H. A. Brouuer.North-Holland Publishing Co., Amsterdam, 65-17 3.

- (1951) Ferrocarpholite, the hitherto unknown ferrous iron analogue of carpholiteproper. Amer. Mineral S6,736'7+5.

- (1955) Genesisof jadei tebylow-grademetamorphism.Anter.J.Sci .2S3,2g3 2gg.- (1956) Some additional data on the crystalline schists of the Rumbia and Mendoke

Mountains, South East celebes. verh. Koninkt. Ndert. Geol,. Mi.jnbouwk. Genootsch.16,385-393.

- (1967) overdruk van tektonische oorsprong of diepe metamorfose? [overpressureof tectonic origin or deep-seated metamorphism?l versl. Gew. verg. AJd. Not urk.,Koninkl. N ed.erl Akod.. W etensclt. 76, 69-7 4.

- (1970) Nekotorie problemy obrazovanija glaukofana i lavsonita [some problemsconcerning the origin of glaucophane and larnsonite. Summary in English]. problems

oJ Petrology and Genetic Mineralogy, Pap:rs dedi.cateil to Acad.. v s. sobol,n on the oc-casion oJ his 60th bi,rthdoy,2, 2+ 40.,Nauka,, Moscow.

E. W. F. nr Ror'rcn, F. F. BruNx, ano p. H. J. Lenave (1967) preliminary noteon ferrocarpholite from a glaucophane- and lawsonite-bearing part of calabria,Southern ltaly. Proc. Koninhl- Ned.erl. Akad. Wetmsch., Seri.es 8,70, 53+-537.

Frscnrn, G. (1929) Die Gesteine der metamorphen zone von wippra mit besondererBeriicksichtigung der Griinschieter. Abhand.i. Preuss. Geotr. Land.esonst , N. F.lZl.

H,ulonoerrl, L. B. (1961) chloritoid: its composition, X-ray and optical properties, sta-bility, and occurrence, J. P etrolo gy, 2, 49-135.

Hesnruoro, Mrrsuo (1966) on the prehnite-pumpellyite metagreywacke facies (Japaresewith English summary). J. Geol. Soc. Jo!.72,253-265.

HrrNucn, K. F. J. (1966) X-ray absorption uncertainty. In Electron Microprobe. J. wileyand Sons, New York, P.296-377.

MacGrr,rnvrv, C. H., W. L. Konsr, E J. Wnrcnar. Moonn, aNo H. J. veN oen ples(1956) The crystal structure of ferrocarpholite. Aeta Crysta.llogr.g, TZ3-776.

MiiGGE, o (1918) ottrelith- und Karpholithschiefer aus dem Harz Neues rahrb. Mineralr Abh. ,75,98.

SrnrNcrn, G. (1967) Die Berechnung von Korrekturen fiir die quantitative Elektronen-strahl-Mikroan aly se. F o rt s chr. M iner aI. 45, 103- lZ4

Tavlon, H. P., Jn., .q.Nn R. G. Cor.aueN (1968) 018/016 ratios of coexisting minerals inglaucophane-bearing metamorphic rocks. GeoI. Soc. Am.er. Bul,I.79, 1127-1756.

wrnr<r.nn, H. G. F. (1965) Die Gmese d.er metamorphen Gesteine springer-verlag, Berlin.

Manuscripl receheil, Morch 23, 1971 ; accepted. Jor fzr.blicati.on, A pril 26, lgf t .