THE AMERICA\ MINERALOGIST, \ 'OL 54, JULY AUGUST, 1S6S

ELECTRON MICROPROBE ANALYSES OF GARNET INGLALTCOPHANE SCHISTS AND ASSOCIATED ECLOGITES

Pntscrrre P. Dunrnv, Department of G-eology and Geophysics, BostonCollege, Chestnut Hil l, Massachusetts 0Z167.

ABSTRACT

Analyses o{ zoned garnet in 15 different rock types from the F'ranciscan assemblage otCalifornia are reported. Specimen localities include the Tiburon Peninsula. Occidenta),Ward Creek near Cazadero, and Santa Catalina Island, Garnet in glaucophane schists fromShubin, U.S.S.R. and Loh oelo, Java is compositionally similar to Franciscan samples

Oscillatory zoning of garnet porphyroblasts is observed in rocks containing fine-grainedmonomineral ic garnet bands.

Comparison of microprobe analyses of the presert study rvith conventional analyses ofgarnets from the same outcrops indicates that the latter are most representative of inclu-

sion-free outer zones of individual crystalsPreliminary data for coexisting garnet, pyroxene and amphiboles shorvs similar frac-

tionation of Mg and Fe in Franciscan eclogites and regiorally metamorphosed glaucophane

eclogites in the southern Urals

Ixrnorucrrox

Coleman et al. (1965) and Chesnokov (1959) reported wet chemicalanalyses for garnet in eclogites associated with glaucophane schists inCalifornia and the southern Urals. Their analyses have recentl"- been usedby several workers calculating distribution coemcients for Mg and Fe incoexisting pyroxene and garnet in eciogites (Banno and ItIatsui, 1965;Perchuk, 1967; Saxena, 1968). Evans (1965) showed that garnets ineclogites of glaucophane schist terranes are compositionallr. 'zoned as aregarnets of other metamorphic environments such as the greenschist(Brown, 1967), epidote amphibolite (Banno, 1965) and amphibolite facies(Holl ister, 1966). The present paper reports the ertent of inhomogeneityin Mg, Fe, Ca and Mn observed in garnets from several of the same Io-calit ies studied by Coleman and Chesnokov: Tiburon, Occidental andCazadero in California, and Shubin, Lr.S.S.R. In addition, analvses arepresented for garnets of associated glaucophane schists, hornblendeschists and other rocks of these localit ies as well as Santa Catalina Isiand,California and southern Tava.

Gnorocrc Snrrnqc

Most samples of the present study are from the Franciscan assemblageof California (Bailey et al., 1964) and in particular from the TiburonPeninsula, Marin Countv, the type locality of lawsonite (Ransome,1894). Garnet bearing rocks at Tiburon crop out as isolated blocks restingin soil developed on graywackes and shales or on incipientlv recrl 'stal-

tr39

1140 PRTSCILLA P. DUDLDY

l ized metasediments containing jadeite and/or lawsonite. Many blocksare coated with rinds of chlorite-actinolite schist and are interpreted bythe author as tectonic inclusions which have been eroded out of associatedserpentinite masses. All the Franciscan garnets of this study are fromblocks which are out of place with the exception of sample 665-C-59which is from a glaucophane schist sequence continuously exposed for330 meters in Ward Creek (Coleman and Lee, 1963).

Glaucophane schists mapped as Franciscan and containing lawsoniteand aragonite crop out on Santa Catalina Island west of the San Andreasfault near Los Angeles. Bailey (1941) mapped higher grade assemblagescontaining occasional k.r 'anite as an older "Olas Series" thrust over theFranciscan. The Catalina samples of this study are assigned to theFranciscan bv- Essene (1967) but the presence of kyanite, tan hornblendeand relatively pyrope-rich garnet distinguish them from Franciscanrocks of northern California.

Two specimens from Shubin near Mednogorsk in the southern Uralswere kindly provided b1- Drs. B. V. Chesnokov and D. P. Grigoriev.Lawsonite has been found in the area, and eclogites similar to those of thenorthern California Coast Ranges crop out apparently in place in a re-gionall l ' metamorphosed sequence of glaucophane-quartz schists (Ches-nokov, 1959,196t ,1963). The eclogi tes form boudinaged lenses up toseveral hundred meters Iong and tens of meters thick (Lennikh, 1963).

Sample 198-9 in the Berkelel, 'collection is from the Loh oelo River nearBanjoemas in south central Java. Associated rock types at this localit1'inclr-rde glaucophane schist, aegirine-augite bearing qrartzite, and garnet-blue-green hornblende schist (Niethammer, 1909).

PBrnocnapny

Most garnet, except that in metacherts and garnetites, forms euhedralto subhedral porphyroblasts 0.5 to 2.0 mm in diameter. Metacherts havethin pink bands of fresh, euhedral garnet which is 0.01 to 0.05 mm in di-ameter and lacks inclusions. Some hornblende schists and occasionalglaucophane schists and eclogites at Tiburon contain monomineralic gar-netite bands up to 3 cm in width composed of anhedral grains 10 to 20 p.ntin diameter. Coarse-grained garnetites at Santa Catalina form boulders6 m across (Essene, 1967) and contain interstitial qtartz and tan horn-blende; sample 665-Cat-S contains garnet 5 mm in diameter. Garnetitesassociated with glaucophane schists have been reported from the NorthBerkeley Hil ls (Brothers, 1954), New Caledonia (Lacroix,I9+2, p. 42),the southern Lrrals (Chesnokov, 1963) and the Pennine Alps (Bearth,1959, p. 27 t ) .

Retrogressive replacement of garnet by other minerals has occurred in

GARN]JT IN GLAUCOPHAN]J SCIIISTS

frO. 1. Electron beam scanning photograph of pyroxene vein in Tiburon hornblende

schist 665-T-12. Na Ka radiation. Pyroxene invades blue green hornblende along cleav-

ages and cuts euhedral garnet (dark). Scale 400X400pm.

some of the coarse-grained Franciscan schists. At Tiburon, retrograde

alteration of garnet is mainly accompanied by the growth of chlorite and

white mica and less commonlv by pumpellyite, lawsonite, aragonite (c/.

Brown et al.,1962), glaucophane and sodic pyroxene. Veins of sodic pr, '-

roxene cut garnet and blue-green hornblende in some hornblende schists(F ig. 1). Replacement o{ garnet by epidote was not observed. Other rochs

show no retrograde effects; fresh garnet coexists with glaucophane (677-

318), sodic pyroxene (292-4) and rarely lawsonite (665-C-59). Rims of

accessory kyanite are altered to paragonite in 665-Cat-3 (Essene, 1967).

All garnets except those of the metache rt 67 7 556 contain inclusions of

other minerals, usually concentrated in the cores. Sphene and epidote are

the most abundant inciusions and present a problem of calcium contam-

ination in analysis. In some schists with no quartz in the groundmass,

garnets contain qrartz inclusions (677 7O7).Sample 677-D from the southern Urals is composed of omphacite,

garnet and actinolite with subordinate glaucophane and quartz- The

actinolite optically resembles blue-green hornblende but is low in AlzOa(3.6/s: Klein, 1969, No. 3-3). Omphacite is concentrated in a green band.

This rock resembles Tiburon sample 677-I4t7 from a single block exhib-

it ing bands of hornblende eclogite, epidote hornblende schist, qlrartz-

epidote eclogite and glaucophane-white mica-quartz schist (677-1351).

tl41

l t42 PRISCILLA P. DUDLEY

Teer,o 1. RnpnnseNtarrve Ganll:r ANer,ysos'

Urals 677 l, lTiburon' ' f ec log i t "

D E 6 i i 702

Core Rim

Cazadero

"Type I I I"

metabasalt

665-C,59

Occidental

zoisite

eclogite

M 1 6 9

Core Rim

Tiburon Santa

glauco- Catal ina

schist garnet i te

677-707 665-Cat-8

3 8 6 3 8 72 1 6 2 1 71 , 1 8 2 2 21 1 6 1 0 41 4 6 7 |0 7 1 1

1 0 1 9 1 0 1 5

s 7 9 3 8 . 3 3 8 . 92 1 8 2 1 3 2 1 92 + 4 2 9 0 2 6 0t 2 6 3 5 5 . 20 5 3 6 2 22 2 4 6 6 i l

9 9 1 1 0 0 3 1 0 0 5

3 8 51 9 52 3 i1 2 73 71 1

9 9 2

Numbers of ions on the basis of 12 (0)

s i 3 . 0 1 s . o 2A l I 1 . 9 6 r . 9 6F e i 1 . 8 1 1 . 8 3Ca 0 . 80 0 . 87M n I 0 . 1 3 o . l 2M g 0 2 9 0 . 1 9

i 0 2 3 . 0 4 3 0 2 3 0 21 , 9 0 1 9 1 1 9 9 1 . 9 8r i 2 1 9 3 0 9 6 1 4 30 9 1 0 7 8 0 9 7 0 8 6o 3 4 0 0 4 0 9 6 0 4 60 14 0 .29 0 08 0 1 ,7

2 9 9 3 0 2 3 0 12 0 3 1 q 8 2 0 01 6 1 1 S 1 1 6 81 0 7 0 3 0 0 . 4 30 0 4 0 . 2 4 0 . 1 40 2 6 0 5 4 0 7 3

3 0 s1 8 51 , 5 91 0 90 2 50 1 3

a Samples described in Key to Figure 2

In neither rock is there textural evidence of replacement of amphiboles byomphacite (as there is in Tiburon hornblende schist 617-1403). Glauco-phane partially replaces a few omphacite grains in 677-1417, and Len-nikh (1963) reports replacement of omphacite bv glaucophane in rocks ofthe Shubin area.

In Urals sample 677-8, pale glaucophane and sphene form a fine-grained matrix in which are embedded garnet porphyroblasts 6 mm indiameter containing qxartz, epidote, ruti le and sphene inclusions. Lenses

M 169: Zoisite eclogite, Occidental Collected by R Rose Microprobe analysis of pyroxene: jadeite 43, acmite 1,augire 56 mol percent (Essene and Fyf e, 1967, Tabte 1, No 1 7).

Lee 113-RGC-58: Wet analysis oI garnet in clinozoisite eclogite from same locality as M 169 (,Lee et al ,1963)677-318: Garnet-epidote-glaucophane schist, Tiburon.Pabst 1955: Anal, sis of garnet in glaucophane schist from same locality as 677-318 (Pabst, 1931, 1955, Samplc

"B. " )677-736: Garnet glaucophane-actinolite-epidote schist, Tiburon67 7 522: GarneI-epidote-omphacite schist, Tiburon677-707 : Garnet-white mica-glaucophane schist, Tiburon.677-C: Garnet-hornblendeschistwithgarnetitebands,Tiburon.CollectedbyS.Rice.Ilornblendeandglauco-

phane analysed by Klein (1969, No 4 2).67 t--T-12: Epidote garnet-hornblende schist, Tiburon. Collected by E Essene. \reined by pyroxene; partial

microprobe analysis; jadeite 20, acmite 27, augite 43 mole percent (Essene, 1967),677-7403i Garnet-horablende schist, Tiburon Veined by pyroxene: jadeite 311 7, acrite 301 7 mole percent.Samples collected on Santa Catalina Island by E. Essene and W. S Fy'fe:66.5-Cat-3: Garnet-zoisite-tremolite albite (an 7) rock with accessory kyanite and paragof,ite (Essene, 1967).665-Cat-8: Garnetite with interstitial quartz665-Cat-3,1: Garnet-zoisite-hornblende schist.665-Ca137: Garnetite with inrerstitial tan hornblende. Occurs as bands in hornblende schist

>>

GARN]iT IN GLAUCOPHANE SCIIISTS

ALM +PY

I 143

e s P

Iitc. 2. Garnet analyses.lCompositions plotted in the lower portion of triangles repre-

senting spessartine, almandinef pyrope, and grossularf andradite mole percent For probc

analyses, a1l tse calculated as almandine. c: core, r: rim

Approximate jadeite and acmite content oI coexisting pyroxenes estimated by method of

Essene and Fy{e (1967) using 221 spacing and B refractive index.

KEY To ANALYSES

Lelt to right, upper row:677-556: Metachert, Tiburon.2g|,4tnclogitewith contofled garnetite bands Collected at Tiburon by R. Hohvay (1906) Pyroxene: jadeite

331 7, acmite 20t 7 mole percent.

677-1417t Epidote-garnet-hornblendeomphacite schist, Tiburon. Pyroxene: jadeite 31-34f7, acmite 17t7

mole percent.617-1351: Garnet-glaucophane-quartz schist interbanded with 677 1417, Tiburon

677-D: Garnet-actinolite-omphacite schist, Shubin, U.S.S.R. Donated by B. V. Chesnokov. Pyroxene: jadeite

35:t 7, acmite 171 7 mol percent Actinolite and glaucophane analysed by Klein (1969' No 3-3)'

677-E: Garnet glaucophane schist, Shubin, U S.S.R Donated by B V Chesnokov'

chesnokov 1959: Wet analysis of Sarnet in glaucophane eclogite containing "anomalous glaucophane" and

actinolite, Shubin, U S.S R. (Chesnokov, 1959)

677-702 : Eclogite, Tiburon.Lee 100-RGC-58: Wet analysis of garnet in eclogite lrom same locality as 67 7 -io2 (.Lee et al.' 1963)

19g-9: Omphacite-actinolite glaucophane schist, Loh oelo River, Java. Partial microprobe analysis of pyroxene:

jadeite 34, acmite 14, augite -52 mole percent (l issene, 1967)

From le{t to right, lower row:665-C-59: Omphacite garnet-glaucophane schist with aragonite and lawsonite, "Type III", Ward Creek (Cole-

man and Lee, 1963). Collected by E. Essene. Microprobe analysis of pyroxene: iadeite 42' acmite 4'

augite 56 mole percent (Essene and Fvfe, 1967, Table 1, No. 5)

Lee 50-CZ-5g: Wet analysis oI garnet in Type III metabasalt (glaucophane quartz-alagonite-clinozoisite-

pumpellyite), Ward Creek r Lee el a/., 1063).

67 7-1 3 13: Zoisite eclogite, Tiburon. Pyroxene: jadeite 35 t 7, acmite 14t 7 mole percent'

1 To obtain a copy of analyses corresponding to points plotted in Figure 2 together

with tabulated mineralogy of analyzed samples, order NAPS Document 100478 from

ASIS National Auxiliarl' Publications Service, c,/o ccM Information sciences, Inc.,

22West 34th Street, New York, New York 10001;remitting in advance $1.00 for micro-

fiche or $3 00 for photocopies, payable to ASIS NAPS.

' . \ i l 3 -RGC-58

-+ccr0ENTAL

1711 PRISCILLA P. DUDLDY

of green sodic pvroxene are present in the matrix. pleochroic haloes sur-rounding tinf inclusions, possibly' zircon, are abundant in the amphibolesof both Russian samples. Such haloes were not observecl in the Franciscanrocks.

AN.q.r,yrrcal TncnNrqun

All analyses were made with an Applied Research Laboratories EMX electron probeusing an accelerating potential of 15 kilovolts ancl sample currents of 0.05 to 0.06 micro-amperes. Beam diameter r,vas approximately one micron. rntegration time was 20 secondsfor al1 elements Three elements were measured simultaneously during each traverse of acrystal: ca, Mn and Mg followed by -F-e, Si and AI. For the major elements, line intensitywas greater than 1000 counts per second. Accuracy is estimated at about 2 percent of theamount present for major elements and 5 to l0 percent for minor elements

Several standards were used in a1l runs, but for consistency, t$,o garnets lr,ere u-red for

Analyses were calculated by a computer program written by Dr. w. chinn. 'fhe pro-

gram includes a linear correction for instrument drift (runs in which drift exceecled 3 per-cent were discarded), a background correction, and the unmodified Philibert correction forabsorption.

Analytical totals in excess of 100 percent were obtainecl for the Mn rich cores of somestrongly zored garnets. Enhancement of observed intensity of Mn Ka radiation by fluores-cence of Mn by Fe KB characteristic radiation is estimated to contribute an excess of nomore thaq 3 to 4 percent of the amount of Mn present. Since this is insulficient to accountfor the high totals, the difficulty may be in Mn calibration or in imprecise repetition o{analytical spots during the second traverse.

ZoN.q.rroN

All the garnets studied are zoned to some extent. Analyses reported arefor individual spots in cr1'stals and are not averages. They do not neces-sarily represent maximum variation present in any sample since sectionswere not precisely- cut to pass through the exact centers of porphyro-blasts. Most of the cr1-stals of the present stud.v show the same pattern ofzonation as that previously reported for metamorphic garnets (e.g. Hol-l ister, 1966). Mn and ca are preferentiaily enriched in the core, whiie Mgand Fe are enr iched near the r im (Fig.3) . Samples 67i C,31g,736 and1403 show reverse zoning in Mn near the rims; such zoning is especiallycharacteristic of garnet porphvroblasts in rccks containing fine-grainedgarnetite bands or veins. Porphyroblasts in the hornblende schist 677-chave Mn rich rims and are immersed in fine-grained garnet richer in Mnthan the rims (Table 2). oscil latorv zoning in garnet of ecrogite 292 4isshown by two Mn-rich bands near the rim in eight porphyrobrasts of thesection that were examined (Fig. a a, b) . Garnet in the:rssociated fine-

GARNET IN GLAUCOPHAND SCHISTS

2 4

22

4 V

t-q9--,. CoO

t 2

t o

I

6

4

2

Oi,PHACITE BAND QUARTZ BAND HORNBLENDE

EPIDOTE HORNBLENDE BAND

Frc. 3. Microprobe traverses of garnets in several bands of Tiburon sample 677-1417.

Variation is not necessarily the maximum present in each crystal since section does notpass precisely through all crystal cores.

P E R C E N T O X I D E S M I C R O N S

o .+oo

\f

\t/

FcO

1146 PRISCILLA P. D(TDLI]V

Tenr,tt 2. CouposrrroN on GenNerrro Bells eNo Assrcraren Ponpnvnonr,asrsrx Honxlr,rxnE Scrrrsr 677 C awo EcLoe:lr 292-4,

Trnunor+ Pesrr,sur-a

677-CPorphyroblasts

67 t- -C

Garnetite

Core Rim

Almandine

GrossularSpessartinePyrope

5 8 . 92 8 92 . 39 . 9

5 3 . 92 6 86 7

13.2

.51 .52 4 . 9I J . I

1 0 4

292-4 292-4

Oscillatory Zoning

AlmandineGrossularSpessartinePyrope

5 2 9 6 0 . 5 5 8 . 7 4 9 . 72 4 . 5 2 1 . 4 1 8 3 2 5 01 5 . 4 7 . 4 9 . 0 3 . 97 . 2 1 0 . 7 1 4 0 1 3 3

Garnetite

3 1 . 6 3 3 . 42 7 9 2 8 73 7 4 3 2 83 1 5 . 1

grained garnetite band shows onlv Mn-rich cores with no zoning bands atthe rims (Fig. 4c).

DrscussroN oF ANALYSES

Comparison of the microprobe results with wet analyses of garnetsf rom the same Franciscan outcrops (677 318: Pabst , 1931, 1955, Sample"8 " ;677 -702 , M 169 ,655 -C-59 : Lee e t a l . , 1965 , Nos . 100 -RGC-58 ,113-RGC-58, 50-CZ-59) shows that the latter resemble values obtainedfor the outer zones of individual crystals (Figure 2). Garnet analyses re-ported by Chesnokov (1961, Table 3) for Shubin amphibole eclogites andgarnet-glaucophane schists are lower in X4n and higher in Mg than coresof garnet crystals 677-D and 677-E, although direct comparison is notwarranted since samples may not correspond to the same outcrops. Sinceinclusions are often concentrated in garnets of this paragenesis, garnetcores are l ikely to be discarded during separation in preference to purerrim material relatively free of inclusions.

Saxena (1968, Table 1), using the analyses of Lee et al. (.1963),Ioundthat distribution coefflcients of Mg and Fe in coexisting garnet and py-

GARN]'T IN GLAUCOPIIANIl. SCHISTS

( c )

Frc. 4. Electron beam scanning photographs of garnet in Tiburon eclogite 292-L. Mn

Karadiat ion.Br ightareasrepresentgreatestconcentrat ionofmanganese Scaie400X400pm. (a) and (b) porphyroblasts showing oscillatory zoning at rim; (c) garnetite band in

same thin section.

roxene in Franciscan eclogites fall in the range KD.rre):0.033-0.053.1 Ifthe inner portions of the garnets were considered, even lower Kp,1p"yvalues would be obtained, further distinguishing eclogites associatedwith glaucophane schists from those of gneissic terranes. As an extremeexample (for the garnet cores are unlikely to be in exchange equil ibriumwith the pyroxene of the matrix), Kn(r"t values were calculated for sam-ples M 169 and 665-C-59 using the probe analyses of pyroxenes in the

r ' ? * 1 - ' s " '. . I F "I K l t p " r : r - " ; . . * r v h e r e 1 1 " :

, - ^ r . ^ 1 . .

F-"t*

Fe2+ i Mg

1148 PRISCILLA P. DUDL]'Y

same thin sections made by Dr. E. Essene (Essene and Fyfe, 1967, Table1). Garnet cores give Ko(r'"):0.031 and 0.027 and rims give 0.063 and0.039 for M 169 and 665-C-59 respectively. Zoisite eclogite M 169 thushas a high Kp compared to other Franciscan eclogites, as does Occidentalc l inozois i te ec logi te 113-RGC-58 (Coleman et a l . , 1965 Ko(n") :0.053) .Sample 665-C-59, a "Type III" rock from Cazadero in which lawsonitecoexists with garnet, has a low Kp. This trend is in agreement with thelower temperature of formation of Type III rocks deduced from oxygenisotope fractionation by Taylor and Coleman (1968; e.g. 270"-280"C.for 50-CZ-59) .

Glaucophane bearing eclogites of the solrthern Urals are of interestsince thev apparently crop out in place in a regionally metamorphosed se-quence of glaucophane-quartz schists, rather than as enigmatic looseblocks which are characteristic of Franciscan terrances. Several l ines ofevidence show the similarity of rocks of both localit ies. Pvrope content ingarnet and jadeite content in pyroxene of the eclogites is similar. Accord-ing to the analyses of coexisting garnet (pyrope 8.8 mol percent) and py-roxene (jadeite 26, acmite 18 mole percent) determined by Chesnokov(1959), a Shubin ec logi te has a Kp1p") :0.024. Fur ther , Kle in 's (1969)analvses of coexisting glaucophane and actinoiite in Urals sample 677-Dshows fractionation of Mg and Fe identical to that in a Cazadero TypeIV schist (Lee et al., 1966) and similar to that in Tiburon rocks.r Ernst(1968, p. 31) noted that Franciscan actinolite-glaucophane pairs showmore pronounced fractionation of Mg and Fe than pairs from Japaneseglaucophane schists, in agreement with the lower temperature of forma-tion of Franciscan rocks deduced from mineral assemblages. Sample677 -D f alls in the range of Franciscan pairs plotted by Ernst (1968, p. 32,Fig. 15a). Since eclogitic rocks similar to Franciscan tvpes evidently havea regional metamorphic origin in the southern Urals, no support is pro-vided for the contact metamorphic origin of Franciscan eclogites pro-posed by Essene et al. (1965).

ACKNOIVLEDGMENTS

Professor B. W. Evans, Ir. J. Turner and W S. Fyle supervised this research at theUniversity of California, Berkeley. Professor Evans instructed the author in the use of themicroprobe and offered helpful comments on a draft of the manuscript. Garnet samples

I According to Klein's data (1969, Tables 3 and 4):

MgglaucoDnane

Mg f Fe "

Nfs:- Ca amohibole

lle -l- Fe

: 0.84 in Urals 677-D and Cazadero 50-CZ-60 and 0.80 in Tiburon 677-C.

GARNET IN GLAUCOPIIANL SATISTS t149

were generously donated b)' Drs. E. Essene, B. V. Chesnokov and D. P Grigoriev. The

National Science Iioundation provided financial assistance through Graduate Fellowships

and Grant GA 500.

RnlnnoNcns

Berr,er, E. H. (1941) Mi,nerology,Petrology,and.GeologyoJ SantoCatolina Island,Calilornio-

Ph D. Thesis, Stanford University.--, W. R. IntvIx eNl D L. Joxrs (1964) Franciscan and related rocks and their

significance in the geology of x'estern Calilornia CaliJ. Ditt Mi'nes GeoI BuIl. 183'

BlNNo, S. (1965) Notes on rock-forming minerals (34): Zonal structure of pyralspite garnet

in Sanbagarva schists in the Bessi area, Sikoku. GeoI. Soc Jap 71r 185 188.- AND Y Marsur (1965) Eclogite types and partition of Mg, Fe and NIn betrveen

clinopyroxene and garnet. P r oc. J ap A c ad. 41, 7 16-7 2l

Bnenrn, P. (1959) Lrber Eklogite, Glaucophanschiefer und metamorphe Pillorvlaven.

S chu eiz. M iner al,. P etr o g M itt. 39, 267 -286.

Bnorntns, l{ N. (1954) Glaucophane schists from the north Berkeley Hills, California.

Amu. J. Sci .252, 61+626.BnorvN, E. H. (1967) The greenschist facies in part of eastern Otago, Nerv Zealand' Con'

trib. Mineral. P etro g. 14, 259-292.BRowN, W. H., W. S. Fvm, AND I-. J TunNsn (1962) Aragonite in Cali{ornia glaucophane

schists, and the kinetics of the aragonite-calcite transformation J ' Petrology 3, 566-

582.

CnesNorov, B V. (1959) Rutile bearing eclogites from the Shubin village deposit in the

Southern Urals 1zt'esl. Vysshihh. Uchebn. Zarednii, Geol Raztted'ko 4, 124-136. [TranslInt . . GeoI. Rer.2,936 9451.

-- (1961) Change in the composition of garnet rvith metamorphism of eclogites of the

Southern Urals. 1zzr. Ahad. Nou'k SSSi? Ser. Geol.7,40-48 [Transl. Izt. Acad. Sci

U SSR, Geol . Ser .7,30-371.- (1963) Eclogites of the southern Urals and their practical significance. In Mogua-

tism, Metamorpl'tism, and Genesi.s of Metols in tlrc Urals, Rep. 1st Urols Petrog. Cong.,3,

257-263 lin Russianl.

Cor.ruaN, R. G. eNn D. E Lnr (1963) Glaucophane bearing metamorphic rock types of

the Cazadero area, California. "/. Petrology41260-301.--, D. E. Lnn, L. B. Bre,rrv emn W. W. Bn,lNNocr (1965) Eclogites and eclogites:

their differences and similarities. Geol. Soc. Anter. BulI 76,483-508.

EnNsr, W. G. (1968) Amphiboles. Springer-Verlag, New York.

EssoNn, E. J. (1967) PeLrogenesis oJ Franciscan Metanorfhic Rocfts Ph D. thesis, Univ.

Calif., Berkeley.eNo W. S. Fvrr (1967) Omphacite in Californian metamorphic rocks Contrib

M,ineral. Pelrog.15, | 23.Evass, B W. (196.5) Microprobe studl' of zoning in eclogite garnets. Geol. Soc Anrcr.

Spec Pap 87,54.Hor.r.rsren, L. S. (1966) Garnet zoning: An interpretation based on the Rayleigh frac

tionation nodel. Science L54,1647 1651.

Hor-wav, I{. S. (1906) Eclogites in California. I. Geol.12,344-358

Kr,rrN, C. (1969) Two-amphibole assemblages in the system actinolite-hornblende glauco-

phane. A mer. M,iner al. 54, 212-237 .KnonnrNc, O, VoN, aNo W. Q KrNNrov (1958) The mineral paragenesis and metamorphic

status of garnet-hornblende-pyroxene-scapolite gneiss from Ghana (Gold Coast).

Mineral. M ag. 31, 846 859.

1150 PRISCILLA P. DUDLEY

Lacnotx, A. (1942) Les glaucophanites de la Nouvelle-Calddonie et les roches qui les ac-compagnentJ leur composition et leur genbse. Mem. Acad. Sci. Insl. France.65.

Len, D. E., R. G. Cor.enaN, H. Blsrnox, exo V. C. Surrn (1966) A two-amphiboleglaucophane schist in the Franciscan Formation, Cazadero area, Sonoma County,California U . S. GeoL Suru. Prof . P ap. 55O-C, 148 157.

-t .{ND R. C. Em (1963) Garnet tlpes from the Cazadero area, California.J. P el r ol o g 1' 4, 4t)0-492.

LlNNrrcr, V. I. (1963) Petrography of the Maksiutovsky complex, particularly the meta-morphism and absolute age of the rocks,In Magm,atism,, Melamorphisnt, ond. Genesis oJMetals in the Urals, Rep. lst Urals Petrog. Cong., 31 245-255 [in Russian]

Nmnr,rmron, G (1909) Die Eruptivgesteine von Loh oelo auf Java Tscheynnks Mineral,P etro g. M itt. 28, 205-27 3.

Parsr, A (1931) The garnets oi the glaucophane schists of California. Anrcr. Minerol.16,JZ I J. t . t .

-(1938) Garnets from vesicles in rhyolite near Ely, Nevada Amer. Mineral. 23, 1O1-103.

-(1955) Manganese content of garnets from the Irranciscan schists.,4zzar. Minuol40,919-923.

Poncuur, L L. (1967) Pyroxene-garnet equilibrium and the depth facies of eclogites. 1zz.Akad. Nauk SSSR, Ser. Geol.11,41-86. fTransl. Inl. Geol. Ret: 10,280-318]

Re.nsolm, F. L. (1894) On lawsonite, a new rock forming mineral from the Tiburon Peninsula, X{arin County, California. Unfu. CaliJ. Dep. Geol. Sci. Bull. l, 301-312

Saxrx.l, S. K. (1968) Distribution of iron and magnesium between coexisting garnet andclinopyroxene in rocks of varying metamorphic grade. Amer. Mi.neral 53,2A18 2A2+

Tevrot, H. P., Jn ,q,Nn R. G Cor.olreN (1968) On/Os ratios oI coexisting minerals inglaucophane-bearing metamorphic rocks. GeoI S oc A mer. Bull. 79, 17 27 17 56.

Manuscript receired, Nor,entber 12, 1968; accepted for fublication, Afril 29, 1969.