Canadia* Mineralogist Vol. 28, pp. 409-418(1990)

FIRSTREPORT OF PLATINUM-GROUPMINERALS AT BLUELAKE, LABRADORTROUGI-I, OUEBEC1

GEORGESBEAUDOIN2 AND ROGER LAURENT Ddpartementde Gdologie,Universitd Laval, Sainte-Foy,Qudbec GIK 7P4

DANIEL OHNENSTETTER Centrede recherchessur la synthdseet la chimiedes mindraux, Ia, rue de Ia F€rollerie,F 45071Orldans Cedex 2, France

ABSTRACT proviendraientde la remobilisationdes sulfures magmati- quesprimaires par desfluides hydrothermaux qui lesont We describehere the frst known occurrenceof platinum- pr6cipit6spr6fdrentiellement dans les zones de cisaillement group (PGM) from the Labrador Trough, eue- allx contactsentre les sulfures massifs et I'encaissant.Cet bec: sudburyitePdSb, temagamitePd3HgTe3 associated €pisoded'alt6ration et de d6formationpourrait 6tre li6 d with bismuthian kotulskite Pd(Te, Bi), kotulskite PdTe, I'orog6nbsehudsonienne (1.8 ca). and micheneritePdBiTe intergrownwith altaite pbTe and an unnamedmineral Pd(Sb,Te,Bi)close in chemicalcom- Mots-clds:mindraux du groupedu platine,p6ridotite, sul- positionto UNl976-4 from Sudbury.The PGMhave been furesmassifs, hydrothermal, mdtamorphisme, defor- found in the Centerand Pogo Lake zonesof the Blue Lake mation,Fosse du Labrador,Qu€bec. Cu-Ni-PGEmassive sulfidedeposit. The massivesulfides arehosted by a peridotitic and gabbroicsill. The PGM arc closelyassociated with Cu-rich shearedmargins of massive INTRODUCTIoN sulfide lensesand their adjacent chloritized host-rock. Occurrencesand texturesof the PGMsuggest that the PGE In this paper, we present the first account of and Cu wereremobilized from the primary magmaticsul- platinum-groupminerals (PCM from the Labrador fides by hydrothermal solutions and preferentially precipi Trough, Quebec. Our report is preliminary, as it tated in shearzones at the marginsof massivesulfide lenses. coversonly certainzones of the Blue Lake deposit, This episodeof alteration and deformation is most likely the main occurrenceof platinum-group elements related to the Hudsonian Orogeny (1.8 ca), (PGE) known in the Labrador Trough (Fie. 1). The Keywords: platinum-group minerals, massive sulfide, PGM were found by petrographicexamination of peridotite, hydrothermal, metamorphism,deformation, polishedthin sectionsof the various faciesof mas- Labrador Trough, Quebec. sive sulfide from the Center and Pogo Lake zones. The Labrador Trough consistsof Aphebian clas- tic and chemical sedimentary rocks and basalts SoN4naarns intruded by sills of ultramafic and gabbroic rocks. The intrusive rocks have been dated at 1.9 Ga by Nous d6crivonsici le premier exempled'une suite de Pb-Pb and Sm-Nd geochronology(Rohon et al., in min6raux groupe platine du du (MGP\ dans la Fosse du prep.). This assemblageunconforrnably overlies an I,abrador: sudburyitePdSb, t6magamite Pd3HgTe3asso- Archean gneissicbasement. The belt was folded, ci6ed une kotulskite bismuthifdrePd(Te, Bi), korulskite PdTe, et micheneritePdBiTe associ6ed de I'altaite pbTe faulted and regionally metamorphosedduring the et un min6ralsans nom, Pd(Sb,Te,Bi)comparable en com- Hudsonian Orogeny (ca. 1.8 Ga) (Dimroth 1978). position chimiqueau mindral UNl976< de Sudburv.Ces The BIueLake depositis estimatedto contain about min6rauxont eG decouvertsdans les zones Center eipogo 2.9 Mt of ore at an averagegrade of 0.84 VoCu, 0.55 Lake du gisementde sulfures massifsd Cu-Ni-EGp du lac 9oNi, 0.69g/t Pd and 0.14s/t ft (Clark et ol. 1989). Bleu, Fossedu Labrador, Qu6bec.Les sulfuresmassifs sont encaiss6sdans un filon-couchede rochesp6ridotitique et GEOLOGICAL SSTTTNc gabbroique.Les MGP sont 6troitementassoci6s i la bor- dure cisaillde riche en Cu des lentilles de sulfures massifs The Blue Lake depositconsists ofthree zonesof et aux 6ponteschloritis€es de la roche encaissante.D'aorbs outcropping la distribution et les textures desMGP.les EGp et le Cu Cu-Ni-PGE massivesulfides, named PogoLake, Center,and Blue Lake, hostedin a com- rPublished with the authorization of the Ministbre de positesill. Severalburied zoneshave been discovered I'Energie et des Ressourcesdu Qu6bec. by drilling. The sill was emplacedat the contact 2Present address: Centre 96oscientifiqued'Ottawa- betweenpelites of the ThompsonLake Formation, Carleton, Laboratoire Derry, D6partementde Gdologie, which form the floor of the sill, and basaltsof the Universit6 d'Ottawa, Ottawa, Ontario KIN 6N5. Willbob Formation, which occur at its roof. In the 409

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Frc. l. Geologicalmap of the Blue Lake depositarea, Labrador Trough, Quebec,with outcropsof Blue Lake, Center and Pogo Lake mineralizedzones indicated.

Blue Lake areathere are three sills, but only the mid- violarite in the Centerzone, but only in part in the dle one is mineralized (Fig. l; Rohon et al. 1988, Pogo Lake zone. Magnetite occursas subhedralto Beaudoin& Laurent 1989,Rohon 1989).The sills roundish anhedralgrains, up to 1.5mm, irregularly are composedof a lower unit of wehrlitic dunite, disseminatedin massivesulfides. wehrlite, and olivine websteritein transitional con- tact v/ith an upper unit of gabbronorite with a Mrcnopnoss ANALYTIcALTncnNtQuss granophyric zone and a chilled margin (Fig. 2). Mas- sivesulfides form lensesof variablethickness (up to Analyseswere made with CAMECA CAMEBAX 6.7 m) located at the baseof (Blue Lake and Pogo automated wavelength-dispersion electron- Lake zones)or within (Blue Lake and Centerzones) microprobes at McGill University and the Centre the middle sill (Fig. 2). Margins of massivesulfide National de la Recherche Scientifique (CNRS, lenses are commonly sheared, rvith a foliated Orl6ans,France). Calibration for the analysesper- -richband in contact with the chloritized formed at McGill was done using synthetic PGM host-rock. The chloritizedzone extends up to 50 cm standards provided by J.H.G. Laflamme (CAN- from the massive sulfides (Clark el al. 1989). MET), with the exceptionof Ni, for which a syn- Sulfide mineralsin the massivesulfide lensesare thetic nickeliferous pyrrhotite was used. Analyses coarseto fine grained and locally foliated parallel doneat the CNRSwere calibrated using pure metals, to lenscontacts. They are composedmainly of pyr- with the exceptionof Fe and S, Sb, and Hg, for rhotite (over 8090),with up to l09o chalcopyrite,up which pyrite, stibnite, and cinnabar were used, to 390pentlandite and up to 690magnetite. Pyrrho- respectively.Precision for analysesperformed at tite is fine to coarsegrained (up to I cm), locally elon- McGill University is better that20/o for major ele- gate parallel to the plane of foliation, and showslen- ments and l2Vo for Ni. Comparableprecision was ticular and lamellar twins and kink bands. obtained at the CNRS, although some discrepancy Chalcopyrite is irregularly distributed in roundish existsfor Ni, due probably to the Ni content (0.2 aggregates,in elongatelenses in the foliation plane, wt.9o) of the pyrrhotiteused as a standardat McGill or occurs as irregular grains interstitial to pyrrho- comparedto a pure metal at CNRS. tite. Pentlanditeforms euhedralto anhedralgrarns (up to I mm) commonly locatedat the boundary of OccuRRENcEsoF PLATINUM-GRouPMINSRALS pyrrhotite or chalcopyritegrains. It also occursas ubiquitous "flames" and irregular inclusions in pyr- Despite detailed examination of numerous rhotite. Pentlandite is almost completelyreplaced by polished thin sections,we found only two occur-

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A A'

THOMPSONLAKE FORMATION PELJTES

B,

30m

10

o 0 10 20 30m SCALE LEGEND

MASSIVESULFIDES SHEARZONE PETROGRAPHICFACIES CHANGE

Ftc. 2. A. Typical cross-sectionof the middle sill in the Centerzone. Massivesul- fides occur as elongate,discontinuous lenses within the sill. B. Typical cross-section of the middle sill in the Pogo Lake zone. Note that the massivesulfides occur at the baseof the sill in contactwith metapelites.The massivesulfides are repeated by a thrust fault.

rencesof PGM in the massivesulfides. One is a tri- pyrrhorite occurrenceat Retty Lake (Rohon e/ al., angular compositegrain (25 pm) located besidea in prep.). fracture, interstitial to pyrrhotite grains; it consists Within a laminatedchalcopyrite-rich band, at the of temagamitePdrHgTe, with bismuthian kotul- margin of a massivesulfide lens, a rounded grain skitePd(Ie,Bi) at oneof the apicesof the grain (Fies. of sudburyitePdSb was found accompaniedby pyr- 3A, 4A). The secondoccurrence is a half-moon- rhotite and partly surroundedby a porous Ag tellu- shapedinclusion Q5 pm)in pyrrhotite(Figs. 3B, 4B). ride (Fig. 3C). The grain is at the contact between The inclusion comprisesa complex intergrowth of pyrrhotite and laminatedlenses of chalcopyrite.The tellurides: michenerite, altaite, and an unnamed Ag telluride (?)was identified by SEM, but Pd(Sb,Te, Bi) minerallabeled PGM-I in this paper. microprobeanalyses proved to be unreliable,prob- Kotulskite with a lower Bi content and associated ably becauseof the porous state of this . with a grain of galenawas describedfrom a massive The contactbetween massive sulfide lenses and the

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Frc. 3. A. Triangular grain of temagamite(T) along a fracture in massivesulfides. Bismuthian kotulskite (K) forms one of the apicesof the triangle. B. Complexintergrowth of altaite - michenerite- PGM-I in massivepyrrhotite. C. Sudburyite(S) and pyrrhotite (P) partly surroundedby a round grain of porous Ag-telluride (A) at the contact between a lenticular aggregateof chalcopyrite and a pyrrhotite grain, D, Seam of euhedral magnetite molded by a band of prismaticamphibole at the contactbetween massive sulfides and chloritizedperidotitic wallrock. E. Sud' buryite (S) interstitial to amphibole (A) in the band molding euhedralmagnetite in Fig. 3D. F. Anhedral grains of sudburyite (S) interstitial to prismatic inclusions of amphibole (A), in contact with disseminatedchalcopyrite (C) in a chloritized peridotitic wallrock.

host rock is shearedand was recoveredin only one across,were found within this interval; they occur drill core in the Center zone. It consistsof a seam interstitially to and molding the amphibole, pyrrho- of euhedralgrains (0.5 mm) of magnetitemolded by tite and chalcopyrite(Fig. 3E). The peridotite at the an undulating band of prismatic amphibole (Fig. contact with the massivesulfides is chloritized and 3D). Numerousgrains of sudburyite,up to 0.1 rnm contains up to 3090 chalcopyrite. Sudburyite occurs

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FIc' 4. A. Back-scatteredelectron image of temagamite(black) overgrownby bismuthiankotulskite (white). Numbers refer to someof the analysesin Tables2 and3. B. Back-scatteredelectron image of the complexinclusion, consist- ing of altaite (white) replacedby michenerite(light grey), both cross-cutby PGM-I (dark grey). Numbersrefer to . some of the analysesreported in Tables 4 to 6.

TABLE 1. CHEMICAI COMPOSITION OF SI'DBT'RYITE

erain rt II III !a2 1b 1c 1d 16 2a 2b 2c 2e Mean 1 27271137L2

Pd 39.30 42.94 43.26 4J..03 4L.67 40.67 4L.63 39.38 40.83 41.89 40.34 40.56 4t.L7 Pt 0.31 0.24 0.98 0.16 0.27 O.4L O.43 n.d. 0.63 O.51 Ir O.55 0.11 0.35 n.d. O.L2 o.23 0.47 0.51 0.65 0.42 Ni 6.39 5.39 s.33 2.69 2.61 2,74 2,39 2.65 2.62 2.L4 2.99 2.4A 3.00 !e o.35 0.08 0.5s L.62 L.20 0.61 0.72 0.57 0.14 0.5s ::_ 0.11 0.17 0.17 0.67 0.89 O.2O 0.18 n.d. 0.09 O.2O Hg L.23 !.77 !.94 n.d. 0.10 0.11 n.d. n.d. 0.31 n.d. 0.31 !.28 0.50 SD 46.24 50.37 50.28 s4.06 52.83 53.24 52.97 54.16 52.74 53.s7 53.s1 52.27 s2.74 Bi J.I/ L.!I I.UJ 0.75 1.56 0.91 0.76 0.3s 1.01 0.89 1.01 I.r7 1.06 Te O.04 O.L4 n.d. n.d. n.d. o.92 0.04 1.18 1.31 0.51 0.33 O.42 O.14 O.2L n.d. O.55 O.L3 O.25 n.d. O.24

Total 99.50 101.64 101.84 100.23 99.93 99.86 100.63 99.s8 100.43 100.46 100.67 1oO.s8

t ' Ronan nunelals stand for analyses obtained lrLth the Mccil-l- microprobe. Atabic numeral-s stand for anal-yses obtaLned wilh the CNRS microprobe. n: number of anal-yses per grain; n.d.: not detected. At McGill, lhe analyses were performed at an acceleration voj.iage of 25 kV and a beam Lntensity of 30 nA for periods of 30 seconds. The following detection-l-j-mit.6 (wt.B) sere computed accordJ-ng to ziebold (1967) from repeated measurements of t.he standards over th€ period of analyses: pd, 0.04; Ni, 0.03i Eg, O.08i Sb, 0.04; Te, O.O3i Bi, 0.06. Analytical t€chniques used a! CNRS are r€ported ln Ohnenstelt€r et al-. (1986). Fe, Cu, S, and possibly As are probabl-y due to fluorescence from natrLx sulEfdE;. Precision and accuracy of trace concentratione of P! and Ir are unknown, and the values repolted shoul-d be taken as 6stLmat66 only. Concentratl-ons ar6 explegsed in wt.*.

as anhedralgrains (up to 0.04 mm) that mold pris- bole. Sudburyiteis whitish creamin air, with weak matic amphibolegrains and chlorite mats, enclosed but distinct anisotropismin brownish grey to dark within disseminatedchalcopyrite (Fie. 3F). greenishto bluish greytints; no reflectionpleochro- ism was observed.The sudburyite(Table 1) is com- MINERALoGYAND CHEMICALCoMPosITIoN parablechemically to other occurrenceselsewhere. Major-element concentrationsof Pd and Sb are Sudburyite within the range of values reported by Cabri & Laflamme (1974, l98l). The averageNi content is SudburyitePdSb occursas anhedralgrains (25-l@ lower than the averagesudburyite from Sudbury, but pm) that may contain inclusions of prismatic amphi- within the range of variation reported by Cabri &

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TABTE 2. CTIEMICAI,COI4POSITION OF TEMAGAMITE

Analysis r II IV 13 5Z ?6 Mean

Pd wt.t 33.93 33.77 34.O2 JJ.YJ 55. Zd JJ. UJ 55.>Z JJ.rv )Zc tJ 32.94 32.42 33.32 33.38 Ni r.77 r..95 1.89 7.77 0.94 0.96 0.76 0.42 0.90 0.86 0.89 0.42 L.20 Hg 2I.sL 21.51 2I.!4 21.s1 20.13 20.95 L9.40 18.50 20.sL 2L.LA 20.56 2r.29 24.64 Te 41.80 41.80 4L.73 41.80 42.49 42.5s 4L.49 4!.45 42.4L 43.36 43.47 42.64 42.32 sb 0.39 0.30 0.2a 0.39 0.23 0.15 0.4s 0.40 0.34 0.13 0.32 0.22 0.30 Bi 0.68 0.63 0.61 0.68 0.98 0.66 3.59 4.43 0.71 0.58 0.34 0.25 1,.21, D+ 0.06 0.39 0.37 o.r2 0.35 0.38 0.11 0.07 0.30 0.24 IT n.d. o.23 0.07 o.25 0.29 0.32 0.13 0.15 n.d. o.2I drt 0.39 n.d. n.d. -i-Anno n.d. 0.34 0.2L Fe n.d. 1.08 1.20 0.40 0.86 L.47 1.01 1.19 1.08 t.O4

TotaL 100.08 99.97 99.67 100.13 100.54 99.93 100.37 100.69 100.18 100.40 100.43 100.39

S€e Table 1 for anal.rtical conditions and conments.

Laflamme(1981). Values for Bi, Hg and Te arevarr- anisotropismis observed,but Cabri (1981a)reported able. The Bi concentrationis higher than the Sud- weak anisotropism in air. Temagamite has a bury average(1.06 versus0.77 ut.s/o); Hg and Te homogeneouschemical composition (Table 2)' with concentrations were not repofred by Cabri & major elementsPd and Hg at the lower limit, and Laflamme(1981). Bi and Sb at the upper limit of the rangeof compo- sitions reported by Cabri & Laflamme (1981)' Temagamite whereasBi and Sb are more abundant. Ni was not reportedby Cabri & Laflamme (1981),but our ana- TemagamitePdrHgTe3, of medium grey color in lysesindicate that Ni can be a minor constituentof air, occursnext to pyrrhotite and bismuthiankotul- temagamite. skite. Neither reflection pleochroism nor Kotulskite

At Blue Lake, kotulskite Pd(Te, Bi) is bright TABLE 3. CIiEI'IICAL COI.IPOSITION OF' KOTULSKITE creamy white in air next to temagamite and pyrrho- Retty Lake BIue Lake tite. Variable reflection pleochroism and

51 18 20 anisotropismwere reported for kotulskite by Cabri (l98la), but neitherwas recognized in this specimen. Pd' 40.65 41.01 39.46 40.37 37.31 36.32 32.17 35.27 The kotulskite has a chemical composition at the Pr 0.33 0.49 0.46 0.43 - 1.07 0.49 0 .78 Ir 0.18 0.58 n.d. 0.38 - n.d. n.d. bismuth-rich end of the range of compositions NL n.d. 0.09 0,07 0.08 0.L7 n.d. n.d. Eg n.d. n.d. n.d. 1.59 n.d. n.d. reported by Cabri & Laflamme (1981)and relative Te 44.36 44.46 43.52 44.1I 26.07 24.67 2r.42 24.05 (Table Bi 10.19 9.56 9.46 9.14 31.0s 31.64 27.87 30.19 to the compositionof Retty Lake kotulskite sb 2.55 2.62 2.42 2.53 2 .58 2. 08 1.76 2.r4 Ni areat low levels,similar to otheroccur- re 2.33 2.00 3.45 2.59 - 3.49 9.64 6.57 3). Pt and s 0,22 0.16 1.?9 0.12 - 1.63 6.55 4.09 renceselsewhere. Sb, however, is more abundant 100.81100.98 100.64 100.84 98. ?9 100.90 99.9 1 than in most localitieswhere it has beenmeasured, with the exception of the New Rambler deposit, coments. 'Sea fable 1 for anallticaI conditions and conc€nttattons expressed ln fl.8. Wyoming (Cabri & Laflamme l98l). Michenerite ond PGM-I

TABLE 4. CHEMICAI, COMPOSITION OF ALTAITE The complextelluride inclusion in pynhotite (Figs. 38, 48) consistsof palebluish erey altaite (Table4), pinkish micheneriteand creamyto yellow PGM-I; pleochroic Pd wt.3 0.06 0.08 0.09 0.1,2 all three are neither nor anisotropic in air. 0.66 0 .38 0.15 0.40 Back-scatteredelectron imagery suggeststhat altaite Bl n. d. 0 .39 nd Ta 14 11 36.37 36.21 36.L2 is replacedby michenerite,and both are cros$-cut sb 0,25 0 .36 0.37 n 10 by PGM-|. The crystallization of altaite (924'C, Pb 60.57 60.51 6L.47 60.62 s 0.84 1.0r 0.94 0.39 0 .80 Cabri & Laflamme 1976) and its replacementby Total 98.02 98.41 9A.42 98.89 michenerite(490-500"C, Cabri & Laflamme 1976) indicate that the systemevolves from Te to TeBi and see Table L for analytlcal condltlons. Iater to Sb (PGM-|) with decreasingtemperature.

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The unnamedPGM-I has a chemicalcomposition TABLE 5. CHE!{ICAL COMPOSITION O[' Pq't-]. AND uN1976-4 similar to an unnamedmineral (LlNl976-4) described 22 Mean unlgZO-q' and analyzed by Cabri et al. (1973), Cabri & 18 21. (198lb) (Table Laflamme (1976),and Cabri 5). As pd' 36.10 3s.11 32.69 34.22 35.27 34.68 42.3 40.3 37.4 is the casewith UNl976-4 from the Vermillion and Pt 0.46 0.19 0.25 0.71 0.64 0.45 fr 0,20 1.d.0.22 0.43 n.d. 0.28 Creighton deposits, Sudbury area, PGM-I is Fe 3.32 4.87 6.36 4.01 3.01 4.31 Nl 3.27 3.01 2.68 2.50 2.53 2.80 associatedwith michenerite (Cabri & Laflamme Pb 1.78 1.14 0.60 0.90 2.75 1.30 sn 2.00 1.93 1.83 1.86 2.04 r.92 1976). The chemical composition of michenerite Hg 0.17 0.19 0.11 0.10 n.d. 0.14 (Table to ihat of other occlurences, Bi 11.89 12.09 13.96 14.39 15.43 13.55 17.8 32.3 6) is similar Te 15.40 15.521,7.23 L6,96 16.77 16'38 18.8 11.1 10.4 exceptfor Bi, which is at the lower limit of the range sb 24.51 23.7L20,!2 21".99 27.O0 22.27 22.0 16.2 As 0.75 L.79 0.79 0.99 n.d. r.08 of compositionsreported. s 0.52 1.40 2.30 0.98 0.32 1.10 Total 100.3?100.93 99.12 100.14 99.15 100.9 99.9 99.8

' Solrn SolutroN CaUrt (rggtl). see Table 1 for analytical condltlooa and co@a[tB. Pb va1u9s ate probab].y due to fluote€cencs IN THE SYSTEMPd-Te-Bi-Sb SYSTEM from nsarby a1talte. concentratlons aro gxp!9aaed in w!.8 . The extentof solid solution and the end members in the systemPd-Te-Bi-Sb are still poorly known. The averagechemical composition of the Blue Lake TABLE 6. CIIEMICAL COMPOSITION OF MICHENERITE PGMs is shown in Figure 5 in relation to the field of variation of known minerals in the systemPd- !4 It Mean Te-Bi-Sb. A complete solid-solution between Pd' 23.6L 2L.73 20.65 24.05 22,5r sobolevskiteand kotulskite is indicatedby the wide Pr 1.65 1. 03 0.80 0.85 1.08 variation in Bi content of kotulskite, Ni n.d. 0.35 0.51 0. 11 0.32 coupled with cu n.d. 0,21 0.30 0.3: o.28 the occurrenceof a seriesof unnamedminerals along Pb 0. 14 6. 08 9.46 n.d. Sn n.d. 0.26 O,27 n.d. O.24 the kotulskite-sobolevskite join. A kotulskite- Bt 41. 13 35.03 37.23 39.95 36.84 sobolevskitejoin is favored relative to a polarite- Te 31.83 3I.26 3r.77 32.55 31.85 sb 1.50 3.37 3.91 1.86 2,66 kotulskitejoin with an immiscibility gap closeto the s 0.47 0.38 0.59 n.d. 0.48 polarite pole, as suggestedearlier by Cabri & Total 100.33 99.70 99.46 99.12 Laflamme (L976). Polarite is orthorhombic and reported to contain between20 to 40wt,oloPb (Cabri see TabLe I for anal"ytlcal condltLone and comenLe. 1981a,Cabri & Laflammel98l). Elratlc hLgh Pb values plobibly cauaed by fLuores- Both sobolevskite conce floB nearby altalte. concenirallons are and kotulskite are hexagonal (Cabri l98la), and expregsed ln wt.t. preliminary data indicatehexagonal s''nmetry with similar cell-parametersto those of sobolevskitefor UN1973-18(Cabri 1981b). by whole-rock assaysthat reveal a characteristic The chemicalcompositions of a seriesof unnamed enrichmentin Pd at the baseor top of the lensesof PGMs, includingPGM-\, fall in the spaceabove the massivesulfides (Fie. O @eaudoin& Laurent 1989). sudburyite-sobolevskite-kotulskiteplane in the sys- The textural relationship of sudburyite to the tem Pd-Te-Bi-Sb @ig. 5). Theseunnamed PGMs metamorphic and hydrothermal minerals in the mar- displayconsiderable scatter in a projection onto the gins of massivesulfides and in adjacentchloritized sudburyite-sobolevskite-kotulskiteplane. Present rock (Figs. 3D, E, F) indicatesthat sudburyitepost- data precludeidentification of fields of solid solu- datesthe dynamothermal event that overprinted the tion or immiscibility and the end members. massivesulfides. Temporal relations are documented by the developmentof a tectonic foliation in the mas- sivesulfides, shearing at the contactsof the massive DIScUSSIoN sulfide lenses,and precipitation of amphibole and chlorite replacingthe host rock. Concentrationof Although the mineral suite reported here is Pd at the margins of massivesulfide lensesand within preliminary and probably not exhaustive,it points the chloritized wall-rocksmost likely resultedfrom to a Pd-dominatedmineralogy of the PGM at Blue the remobilization, by hydrothermal solutions, of Pd Lake. An important feature of the distribution of originally contained in the primary massivesulfides. PGM is their scarcityin carefully investigatedmas- This eventalso inducedremobilization of Cu and the sivesulfides and, on the other hand, their relatively concentrationof massivechalcopyrite at the margins high abundancein the contact zonesof the massive of the massivesulfide lenses.These margins, which sulfides and their adjacent chloritized rock. The were strongly shearedowing to competencycontrasts abundanceof PGM atthe border of the massivesul- betweenmassive sulfides and enclosingperidotite, fides and in adjacent chloritized rock is corroborated served as channelways for hydrothermal fluids

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LAKE

SUDBURYITE IOPALLADINITE

1974-6

uN1961-8 1974-7

': / uN19z6-s SOBOLEVSKITE BlueLake l r"u, r"* uN1e76-5^::,^-.^ "''.3:":: _^_i"jY::i"9 uN1973!18uN1979-1 OTULSKITE TEL ADINITE

SUDBURYITE

uN1974-7 \ KEITHCONNITE 1976-9^ \ LLADINITE uN196 1-8 uN'f19--o;Ft-1 197 4-6

uN1973-'18 ia.'-4=4 TESTIBIOPALLADINITE SOBOLEVSKITE :;-:7i:1 BOROVSKITE fiiln'n-iI i-v.t-.-'-,1-;-) uN1976-5__ FROODITE \t m**;#r ---{ MERENSKYITE

Te Frc. 5. Chemicalcomposition of PGMs in the systemPd-Te-Bi-Sb, Average composition of PGM from this study representedby largedots. Minerals with little compositionalvariation are representedby squares,whereas the field of variation of the othersis outlined with a broken line (Cabri & Laflamme l98l). Averagecomposition of unnamed mineralsis representedby triangles(Cabri 198lb); only thoseabove the sudburyrte- sobolevskite- kotulskite plane are identified and discussedin the text. Unnamedminerals plotting at the Bi or Te polesare not shown for the sake of clarity.

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precipitating disseminated sudburyite and chal- Labrador Trough. Our presenthypothesis, which copyrite. The occurrenceof sudburyite at sulfide- needsto be testedfurther, impliesthat PGEconcen- silicategrain boundariesin dynamically metamor- tration and PGM precipitation are secondaryand phosedrocks at the DonaldsonWest deposit, Cape tectonicallycontrolled, resultingfrom the remobili- Smith fold belt, also has been interpretedto indi- zation of primary massive sulfides of magmatic cate direct precipitation from hydrothermal fluids origin. (Dillon-Leitch et al. 1986).The associationof sud- buryite and kotulskite with hessiteor galenasuggests AcKNowLEDGEMENTS a rather low temperaturefor the hydrothermal fluids. We proposethat the hydrothermal fluids respon- This paper is published with permissionof the sible for the secondary Cu-Pd enrichment were Ministbrede l'Energie et desRessources du Qu6bec, generatedduring a major dynamothermal event which funded this work through a contract with becausethe mineralizationis clearlyassociated with Universit6 Laval, within the framework of the deformation. Furthermore, no other distinct Canada-Qu6becMineral DevelopmentAgreement. hydrothermaloverprint has beendocumented. The Constructivecriticism throughout this study and crit- Hudsonian Orogeny (1.8 Ga) is the major ical readingby T, Clark are acknowledged.J.H.G. dynamothermalepisode known in this area of the Laflamme (CANMET) provided the PGM stan-

a, o o MASSIVE SULFIDES

100 0 500 1000 7oSULFIDES Pd (ppb) Ftc. 6. Profile of Pd and sulfide abundancesin the middle sill. Center zone. The most prominent Pd enrichmentoccurs at the top of the massivesulfide lens in this drill hole, whereasin othersi1 occurseither at both, or at the top or bottom of the massivesulfide lenses(data from Beaudoin& Laurent 1989).

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dards, and Dr. M. MacKinnon gave expert advice Elements: Mineralogy, Geology, Recovery (L.J. regarding microprobe operation. The authors Cabri, ed.). Can. Inst. Min. Metall., Spec. Vol.23, acknowledgeF. El Kaliobi, J. Breton (BRGM, t5l-t74. Orl6ans),and JEOL Francefor the SEM and back- Clenr, T., BreuDorN,G. & Leunrr.r-r,R. (1989):Les scatteredelectron images,respectively, and C. Gillep gites de Cu-Ni-Pd-Pt du Lac Retty, Fosse du (BRGM, Orl6ans)for someof the microprobeanal- Labrador. Can. Inst. Min. Metall. Bull. 82, 108 yses.The paperwas $eatly improvedby L.J. Cabri, (abstr.). G.K. Czamanske,R.F. Martin, and two anonymous reviewers. DiLr-oN-LsrcH,H.C.H., WarrtNsotl, D.H, & Coers, C.J.A. (1986): Distribution of platinum-group ele- REFERENCES ments in the Donaldson West deposit, Cape Smith Belt, Quebec.Econ Geol.81, l147-1158. BnauoorN,G. & LaunrNr, R. (1989): M€tallog6nie des €l€ments du groupe du platine dans la rdgion du Lac Drunotr, E. (1978):R€gion de la Fossedu Labrador. Retty (zones Center et Pogo Lake), Fosse du Ministdre de I'Energie et des Ressourcesdu Qudbec, Labrador. Rapp. final, Ministdre de I'Energie et des Rapp. gdol. RG.193. Ressources du Qudbec, MB-E9-2E. OnNrNstgttln, D., WarxtNsoN,D.H., JoNrs, P.C. & Canu, L.J. (l98la): The platinum-group minerals. .Iz TALrrNcroN, R. (1980: Cryptic compositional var- Platinum-Group Elements: Mineralogy, Geology, iation in laurite and enclosing chromite from the Recovery(L.J. Cabri, ed.). Can. Inst. Min. Metall., Bird River sill, Manitoba. Econ. Geol. El' Spec.Vol.23, 85-150. I 159-1168.

- (l98lb): Unnamed platinum-group minerals. 1n RoHoN, M.L. (1989): Magmatisme protdrozoique et Platinum-Group Elements: Mineralogy, Geology, Indices de Cu-Ni sulfurds (+EGP) dans la Fosse Recovery(L.J. Cabri, ed.). Can. Inst. Min. Metall., du Labrador (Qudbec-Canada) entre les Lacs Retty Spec.Vol.23,175-195. et Low. Thdse D.Sc., Universit€ Paris VI, Paris.

Hannrs, D.C. & Garr, R.I. (1973): Michenerite (PdBiTe) redefined and froodite STETTER,D., Roosn, G., TnEuIL,M. & VIlel, P. (PdBit confirmed from the Sudbury area. Con. (1988): Indices de Cu-Ni sulfur€s li6s au mag- Mineral. 11.903-912. matisme mafique et ultramafique prot6rozoique dans la fosse du Labrador (Qu6bec, Canada). Dans & LanLevue, J.H.G. (1974):Sudburyite, a Gisements m6tallifbres dans leur contexte g€olo- new palladium-antimony mineral from Sudbury, gique (2. Johan & D. Ohnenstetter, eds'). Bur. Ontario. Can. Mineral. 12. 275-279. Rech. G6ol. Min., Doc. liE' 24'7-284.

& - (1976): The mineralogy of the Zrcnovo, T.O. (1967): Precision and sensitivity in elec- platinum-group elementsfrom some copper-nickel tron microprobe analysis.Anal. Chem. 39' 858-861. depositsof the Sudbury area, Ontario. Econ. Geol. 71. ll59-1195.

& - (198I): Analyses of minerals contain- Received June 6, 1989, revised manuscript accepted ing platinum-group elements. 1r Platinum-Group April 5, 1990.

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