Canadian Mineralogist Vol. 30, pp. l2L-136 (1992)

HYDROTHERMALORIGIN OF PLATINUM.GROUPMINERALIZATION IN THE TWO DUCK LAKE INTRUSION.COLDWELL COMPLEX, NORTHWESTERN ONTARIO

DAVID H. WATKINSON Departmentof Earth Sciences,Ottawa-Carleton Geoscience Centre, Carleton University' Ottawa, Ontario KIS 586

DANIEL OHNENSTETTER Centrede Recherchessur la Synthdseet Chimiedes Mindraux, Centre National de la RechercheScientifique' 45071Orldans Cedex 2, France

ABSTRACT grainsde plagioclaseau contactde la chalcopyrite'4) dans les filonets s6parantla chalcopyritedes autres min6raux, et 5) dansles zones d'alt€ration desparagenbses primaires Platinum-groupminerals (PGM) occurin chalcopyrite- de silicateset d'oxydes. Certains MPG sont fortement rich sulfide assemblages + Ni) = 0.94, [Cul(Cu zon6s, en pafiiculier la hollingworthite et la sdrie Ptl(Pt+Pd) = 0,221 from very coarse-grainedto d'autres ont des compositions pegmatitic gabbroic rocks of the Two Duck Lake atokite-zvyagintsevite, (sperrylite, kotulskite riche en Bi, Pd5As); intrusion at the easterncontact of the Coldwell alkaline homogbnes MGP se pr€sententen agregatscomplexes rock complex with Archean metavolcanic rocks, in enfin, certains II associ6ei Pdz(Sb,As)'la nickeline nonhwesternOntario. The PGMoccur: l) in sulfides or commela mertieite palladifbre, la majakite, la sperrylite et I'or, et I'atokite at their contacts,2) in postcumuluschalcopyrite, 3) in the la zvyagintseviteet A la kotulskite enrichieen rim of plagioclasegrains with chalcopyrite, 4) in veins associ6ed plomb. des MGP avec: l) les plages along the contacts of chalcopyrite and other minerals, Les relations gabbrospegmatitiques, 2) du mica et de and 5) in veins and areas of alteration of the primary interstitiellesdes 3) la calciteet la chlorite silicate and oxide assemblage.Some PGM are strikingly I'apatite richesen fluor et chlore, 4) les assemblagesde chlorite zoned(hollingworthite and atokite-zvyagintsevite);others dansles zonesd'alt€ration, s€ricite, de calcite are single homogeneousgrains (sperrylite, bismuth-rich ferrifdre, d'6pidote, d'amphibole, de pr6fdrentiellementla magn6tite, et 5) kotulskite, Pd5As), and some occur in complex ag- qui remplacent - qui pyrrhotite' sont gregares(such as mertieiteII with Pd2(Sb,As),palladium- chalcopyrite cubanite remplacentla et en 6l6ments bearing nickeline, majakite, sperrylite and gold; atokite compatiblesavec l'enrichissement en cuivre des with zvyagintseviteand lead-richkotulskite). The relation- du groupe du platine dessulfures lors de l'interaction avec les shipof theplatinum-groupminerals to: l) interstitial areas fluides hydrothermaux de basse temp6rature in pegmatitic gabbro, 2) F- and Cl-bearing biotite and min€rauxmagmatiques. apatite, 3) chloritic and calcitic veinsat mineral contacts, alt6ration, analyses ?r la 4) assemblagesof iron-rich chlorite, epidote, amphibole, Mots-clds: hydrothermale, fluides, min6raux du sericite, calcite, especially after magnetite, and 5) microsonde, chalcopyrite, platine, de Coldwell, Ontario. chalcopyrite- cubanitereplacing primary pyrrhotite, are groupe du complexe compatible with enrichment of sulfides by Cu and platinum-group elemenlswhere hydrous fluid has inter- INTRODUCTION actedwith primary igneousminerals at low temperature.

Keywords: hydrothermal, alteration, chalcopyrite, elec- The Coldwell Complex, in northwestern Ontario tron microprobe, fluid, platinum-group minerals, (Fig. l), is an unmetamorphosed, undeformed, ColdwellComplex, Ontario. alkaline plutonic complex emplaced at l.l Ga (Heaman & Machado 1987, unpubl. manuscript) Sotrltr4alns into Archean metavolcanic, metasedimentary and granitic plutonic rocks (Puskas 1967, Dahl et al. Les min6raux du groupe du platine (MGP) sont 1986). The ultramafic to felsic, silica-saturated to associ6saux paragenbsessulfur6es, riches en chalcopyrite silica-undersaturated suites of rocks were inter- = = tCu/(Cu+Ni) 0,94,Pt/(Pt+ Pd) 9,221'desgabbros preted to group around three intrusive centers ferrogabbrosi texture grenue et pegmatitiquede et des (Currie 1980, Mitchell & Platt 1982). The first I'intrusion de Two Duck Lake du complexe alcalin de of an arcuate, massive to.layered Coldwell, situee au contact oriental des rochesm6tavol- center consists gabbroic (Eastern gabbro, host to caniquesarch6ennes, dans le nord-ouestde I'Ontario. Les succession of MGP apparaissent:l) dansles sulfuresou i leur contact, most of the sulfide-rich rocks) and syenitic rocks 2) dans la chalcopyrite postcumulus,3) en bordure des (Wilkinson 1983, Watkinson 1987). t2l t22 THE CANADIAN MINERALOGIST

Ftc. l. Geologicalmap of the Coldwell Complex showingthe locationsof the Two Duck Lake deposit(star) and GeordieLake deposit(square); map after Puskas (1967)and Mitchell & Plau (1982).

Dahl et ol. (1986, unpubl. manuscript) have outlined a 30 Mt deposit grading 0.4390 Cu, 0.69 shown that the rocks enriched in the platinum- g/t Pt and 1.85 g/t Pd; Cul(Cu+Ni) and group elements(PGE) and Cu near the contact of Ptl(Pt+Pd) are about 0.94 and 0.22, respectively the complex with Archean metavolcanicrocks are (Watkinson 1987). Based on detailed mapping not a faciesof the Easterngabbro, but are part of (Dahl et al. 1986, Watkinson 1987), samples a later intrusive complex, the Two Duck Lake relatively enrichedin sulfides ard PGE, as well as intrusion (Fig. 2). This is a coarse-grainedto rocks with pegmatitic and other coarse-grained pegmatitic, zoned intrusion with a central mag- textures,were investigated to establishthe mineral- netite-bearing unit underlain and overlain by ogy and petrology of the PGE- and sulfide-rich sulfide-rich rocks. Fleck Resources Ltd. has assemblages. HyDRoTHERMAL pcE MINERALIZATIoN. Two DUCK LAKE INTRUSIoN 123

GEoLocy oF THEEesrenN CoLDwELLCotr,rplrx

O+ The Easterngabbro of the Coldwell Complex is 47 ii! a massive to layered intrusion ranging from wehrlite to diorite, and locally to anorthosite;these units are generally unaltered. Marginal units are O+ massiveto weakly layered, but the main layered rgo seriesconsists of laminated cumulates,mainly of magnetite,olivine, plagioclase,clinopyroxene and o+ minor orthopyroxene. The Eastern gabbro has 49 o+ variable concentrations of magmatic sulfides 85-18 (Wilkinson 1983, Watkinson 1987) and locally abundant, partially digested xenoliths; there ap- E pearsto be a positivecorrelation in the occurrences of sulfides and xenoliths of country rocks. Detailed mapping (Dahl et al. 1986, unpubl. manuscript) of the (Cu + PGE)-rich sulfide units has revealedthat most of the sulfide-bearingrocks nearthe easterncontact, on the Marathon property of Fleck ResourcesLtd., are part of a cross-cutting suite of sillJike intrusions that comprisethe Two Duck Lake intrusion (Fig. 2). This complex unit was subdividedfrom bottom to top into: l) a fine- to medium-grained hornblende gabbro to mon- fbo Duck zodiorite, 2) a coarse-grainedto pegmatitic olivine La&e ferrogabbroto ferrodiorite, and 3) a coarse-to very coarse-grainedolivine gabbro to diorite. All these units contain abundant xenoliths of Archean volcanic rocks and Coldwell Complex (Eastern gabbro), partial digestion of which has modified the compositionof the Two Duck Lake magmaor magmasand has resulted in pods of granophyric material(Watkinson & Dahl 1988).

PETROLOGY OT PGM-BT,IRING ASSEMBLAGES (!ii The sulfide assemblagein rocks of the Coldwell Complex is predominantly pyrrhotite + chal- copyrite + pentlandite. The fourth major mineral is either pyrite or cubanite, but some specimens contain mackinawite or other Fe sulfide minerals that are interpreted to be secondary after chal- copyrite or pyrrhotite. The assemblageof primary sulfides and their textures (massiveand dissemi- :'.+ justifiably l.%' natedin gabbroicrocks) were interpreted j .'.' to be of magmaticorigin (Puskas1967). However, aspointed out by Wilkinson(1983) and Watkinson O lOOm (1987),the PG.E-enrichedsulfides are found in the $

Ftc. 2. Ceologicalmap of the Two Duck Lake intrusion Watkinson, & J. McGoran); sulfide- and xenolith- showing the location of drill holes and trenches bearingunit (mainly gabbro):intensely dotted patrern; (simplified from unpublishedmap of R. Dahl, D.H. ferrogabbroicrocks: sparselydotted pattern. t24 THE CANADIAN MINERALOGIST most Cu-rich rocks, and the platinum-group grained to pegmatitic gabbro. Most rocks in the minerals (PGM) (Figs. 3-5) are associatedwith Two Duck Lake intrusion are unaltered, but the pyrrhotite-poor assemblagesof chalcopyrite and PGE- and Cu-rich assemblagesare partly altered cubanite, with minor bornite, digenite and chal- to an assemblageof actinolite + chlorite + epidote cocite (Watkinson 1990). There is a positive + sericite + calcite (Watkinson & Dahl 1988). correlation of the PGE-rich sulfides with biotite, PGE contents are generally low in fine-grained apatite and granophyric intergrofihs in coarse- rocks; the highestcontents occur in coarse-grained to pegmatiticrocks, but contentsare slighlly lower in pegmatiteswith the coarsestgrain-size. The PGM have been found in the following settingsin the Two Duck Lake rocks: l) included in or adjacent to postcumulus sulfides, mainly chalcopyrite and cubanite, 2) in chalcopyrite or pentlandite along sulfide-oxide grain boundaries, 3) in the rim of plagioclasegrains with chalcopyrite, and 4) in veinletsalong the contactsof chalcopyrite with other minerals,or 5) in veinscutting magnetite (with ilmenite lamellae)that is partly altered, and in other areas of altered primary magmatic minerals. Some of the petrographic relationships are illustrated in Figures3-5 for the largest and most complex assemblagesof PGM. However, most PGM occur as isolatedgrains in chalcopyritewith cubanite lamellae, commonly related spatially to galena and altaite. In only one case was a PGM (Bi-rich kotulskite) found within plrrhotite @g. 5D). There is a close spatial relationship of the PGM with mica and apatite; the mica contains as much as 0.35 wt.Vo Cl and l.l wt.9o F, whereas apatitehas as much as I .07wt.9o Cl and 4.15wt.7o F. The PGM are evenmore closelyassociated with minerals of the alteration assemblagechlorite + actinolite + epidote + sericite + calcite. In addition, some of the PGM occur in veins and within or at contacts where the primary Fe minerals, such as pyrrhotite and magnetite (Figs. 4A, B), have been partly replaced. Magnetite is replacedby Fe-rich chlorite, epidote and siderite- calcite, whereasthe ilmenite lamellae are fresh or

Frc. 3. Petrographicrelationshtp of PGM to the silicate, sulfide and oxide minerals. A) Pb-rich kotulskite, zvyagintsevite and atokite with chalcopyrite with abundant cubanite lamellae, enclosedin margin of plagioclase(pl) in contact with pentlandite (pn) and altered pyrrhotite: trench 289.5. Scalebar: 0.60 mm. B) Complex assemblageof platinum-group minerals (pgm)enclosed by pentlanditeadjacent to chalcopyrite (ccp) and enclosedby chlorite (chl) after plagioclase: drill hole 43-320. Scale bar: 0.67 mm. C) Zoned hollingworthite (hol) along chlorite + calcite vein adjacentto chalcopyrite + biotite (bi) + apatite (ap) + plagioclaseassemblage; vein alsocontains argentian pentlandite:drill hole 43-290. Scalebar: 0.1 mm. HYDROTHERMAL PGE MINERALIZATION, TWO DUCK LAKE INTRUSION I25 less strongly altered to titanite and rutile. Some entrants into pyrrhotite indicative of replacement PGM with chalcopyrite occur in veins that cut of early pyrrhotite. In some specimens,there are magnetite with ilmenite lamellae that have under- pyrrhotite gratns where replacementby siderite is gone penecontemporaneousalteration @igs. 5A, evidentbecause the pentlanditeflames in pyrrhotite B). Pyrrhotite is commonlyrimmed by chalcopyrite protrude into siderite. (commonly with cubanite lamellae), with re- Tnr P ntNuu-GnouP MtNsneI-s

The PGM in sulfide-rich rocks of the Coldwell Complexhave been described by Wilkinson (1983), Watkinson(1987), Mulja (1989),Mulja & Mitchell (1990,1991), Watkinson (1990), Ohnenstetter el a/. (1991) and Ohnenstetter& Watkinson (1991). Mulja's study concernedthe MacRae occurrence, Geordie Lake area, in the central part of the Coldwell Complex (Fig. l), whereasthe other data are from the easternpart. PGM discoveredto date from the Two Duck Lake rocks are hollingworthite (ideally RhAsS; Ohnenstetter et al. 1991), merenskyite(PdTe2; Wilkinson 1983), moncheile (PtTer, sperrylite (PtAsr, kotulskite (PdTe, in- cluding Bi- and Pb-bearing varieties), atokite (PdrSn), zvyagintsevite (Pd3Pb), guanglinite (Pd3As), mertieite II (Pdssb3), sopcheite (Pd3AgaTe), unnamed minerals [Pd5As2 and Pd2(Sb,As)1,majakite (NiPdAs) and Pd-bearing nickeline.Other precious-metalminerals are argen- tian gold (Au/Ag ratio near l), hessite and argentian pentlandite. Kotulskite is the most aburrdantPGM, and sperrylite, hollingworthite and the atokite-zvyagintsevitesolid-solution group also are relatively abundant. The minerals found during routine petrography were examined by scanning electron microscopy using energy-dispersionspectrometry (SEM-EDS; see Figs. 4, 5) in laboratories at Carleton University, Geological Survey of Canada, and Bureau de RecherchesG6ologiques et Minidres (BRGM). Quantitative analyseswere performed at BRGM by wavelength-dispersionspectrometry using the X-ray lines TeLe, AuLa, AsZa, SKo, SbZa, PtIa, BMa, AgL?, NirKo, PbMa, SnLa, HgMa, PdZo, FeKo, IrKa, CuKo, RhIa; stand-

Frc. 4. Scanningelectron micrographs of platinum-group minerals. A) Complexly zoned hollingworthite (Oh- nenstetteret al. l99l) in chalcopydte adjacent to plagioclase,ilmenite, calcite (cc) and pyrrhotite (po): drill hole 85-13-109.5. B) Kotulskite (white) in chalcopyrite along contact of partially altered mag- netite (mte) and ilmenite (ilm). Alteration assemblage is chlorite + epidote + titanite (tit) + calcite: drill hole 43-319.5. C) Atokite + zvyagintstevite + Pb-bearing kotulskite assemblageadjacent to chal- copyrite, enclosedby plagioclase(see Fig. 3A). t26 THE CANADIAN MINERALOCIST

Frc. 5. Scanning electron micrographs of platinum-group minerals. A) Zoned zvyagintsevite(zvy) adjacent to chalcopyrite along vein in magnetite + ilmenite, the latter altered to chlorite + epidote + calcite + titanite; differing shadesof grey result from complexzoning of Pd, Pt, Pb, Ag, Te, Sn, As: drill hole 47-444.B) Delicate habit of atokite with Pd and Pt zonation, about I mm from 5A; drill hole 47-tfi4. C) Atokite (ato) + zvyagintsevite + gold (Au) assemblageadjacent to chalcopyritein vein cutting pyroxene;trench 266. D) Bismuth-richkotulskite (kot) in pyrrhotite with pentlanditeflames; somepyrrhotite partly replacedby siderite,and very small amount of pentlandite altered to argentian pentlandite; drill hole 85-5-160. E) Atokite + zvyagintsevite+ Pb-bearing kotulskite enclosedby plagioclaseand chalcopyrite(see Fig. 4C). F) Complex assemblageof mertieite II (mer II) + sperrylite + majakite + argentiangold (white) + Pdz(Sb,As)+ palladiannickeline (nic) enclosedby pentlandite (seeFig. 3B). Note various shadesof grey in nickeline and mertieite II, indicating variable Pd/Ni and Sb,/As, respectively. HYDROTHERMAL PGE MINERALIZATION, TWO DUCK LAKE INTRUSION 127 ards were pure metals,and pyrite for S, galenafor with argentian gold (Fig. 5C). Gold-bearing Pb, sperrylitefor As, stibnite for Sb, cinnabar for zvyagintseviteassociated with an Ag-Au alloy from Hg and synthetic SnO2 for Sn. Analytical condi- Noril'sk was describedby Cabri & Traill (1966). tions were: acceleratingvoltage 25 kV, reference Zvyagintsevite (Fig. 5A) also tends to As-rich current 30 nA, counting time l0 s, data reduction compositions, and one composition is closer to by MBXCOR-ZAF (Henoc & Tong 1978). guanglinite (Pd3As) than to PdiPb. Te contents Representativecompositions of the PGM are (atomic) nearly attain those of Pb, Sn and As; presentedin Tables l-8; all other PGM data and details of these solid solutions are discussedby compositionsof coexistingsulfides and silicatesare Ohnenstetter& Watkinson (1991). presentedby Ohnenstetter(1990). Cu, Fe and S Three groups of kotulskite compositions are contents of the PGM are mainly the result of apparent in Figure 7; similar compositions of analysisof small grains enclosedin chalcopyrite. kotulskitewere reviewed by Cabri (1981).The most The composition of most minerals varies only Bi-rich cluster of compositions(Table 3) is similar slightly; however,hollingworthite from Two Duck to those describedby Beaudoin et ol. (1990) a\d Lake (Ohnenstetrer et al. l99l) and atokite- Mulja & Mitchell (1990). This may indicate that zvyagintseviteare intricately zoned. Atokite and solid solution exists toward sobolevskite(PdBi). rustenburgite@t3Sn) may form a completesolid- Kotulskite with Pb contents as high as 9.5 wt.9o solution (Mihelik et al, 1975, Malevskiy el a/. Pb (Table 4) is significantly more Pb-rich than 1978), and a complete solid-solution exists from those compositionsdescribed by Kovalerrkeret al, atokite to zvyagintsevite (Genkin et a/. 1966, (1973) from Noril'sk and by Cabri et al. (1979) Mihelik et ol. 1975). Chemical compositions of from Stillwater. atokite - zvyagintsevite from Two Duck Lake Sperrylite (Table 5) occurs as isolated grains, specimensare illustrated in Figure 6; there appears with an overgrowthof zonedhollingworthite, or as to be complete solid-solution between the two inclusions in mertieite II (Table 6, Fig. 5F). intermetallic compounds. Ptl(Pt + Pd) versus Unnamed Pd5As2 (Table 7) occurs with chal- Sn/(Sn+ Pb) data define a line y = 0.2x; variance copyrite; the associationof PdrAs2with palladoar- about the line is 0.77 (n=45). The subtlevariation senide,sperrylite, chalcopyrite and stillwateritealso in compositions is revealed in some SEM-EDS has been describedby Cabri et al, (1975). photographs (Figs. 5 A, B,); however, sharp The complex association of mertieite II with contacts (Figs. 5C, E) may result from low- palladium-antimony arsenide(Table 7), majakite temperature exsolution that produced coexisting and nickeline (Fig. 8, Table 8) plus argentiangold Pt-rich and Pt-poor compositions(Fig. 5C). This is shown in Figure 5f. This mertieite II is relatively proposed exsolution is compatible with the Au rich in As compared to examplesfrom Noril'sk contentsof somephases with intermediatecomposi- (Kovalenker et al. 1978) and similar to those tions(as much as 1.84wt.Vo: Table l), ascompared describedby Cabri & Chen (1976)from Tweefon- with Au-free compositionsin the grains coexisting tein, South Africa. The Pd2(Sb,As)mineral may

+ : 0.4

,::

t' ,

0.0 o.2 0.4 0.6 0,8 1.0 Sni(Sn+Pb) Fro. 6. Linear regressionof Pt,/(Pt+Pd) versas Sn,/(Sn+Pb) for atokite and zvyagintsevitesolid-solutions. Points well below line refer mainly to As-rich compositions. t28 THE CANADIAN MINERALOGIST

TABLE I. SELECTEDEIICTRON-MICR,OPROBE TABLE 2. SELECTEDELECTRON-MIG,OPROBE DATA DATAONATOKITE ON ZVYAGINIIEWTE

Weight percent Weight percent Pt 7.79 13.93 10.04 7.29 8.76 I 1.00 t2.28 As 0.05 0.00 0.01 0.00 0.00 0.1 0.00 Pt 23.t3 25.68 24.40 22.53 25.56 23.40 I Pd 53.86 50.55 53.35 52.30 53.82 53.32 52.t'l As r.o9 o.ro 0.01 0.84 0.16 0.00 I r 0.81 0.00 0.91 1.36 l.t 6 0.88 0.44 Pd 48.83 43.78 46.47 48.91 47.17 4E.63 Cu 0.21 0.13 0.19 O.24 0.41 0.28 0.41 Ir 0.13 0.00 0.00 0.00 0.00 0.00 Ni 0.03 0.00 0.00 0.00 0.00 0.00 0.00 Cu 0.28 0.25 4.23 0.5E 0.33 0.19 Fe 0.40 0.29 0.48 0.31 0.43 0.32 0.00 Ni 0.00 0.00 0.00 0.01 0.00 0.09 s 0.05 0.a2 0.08 0.11 0.06 0.00 0.00 Fe 0.35 0.33 0.34 0.38 0.21 0.28 Sn 4.79 tz.st 6.18 4.7s 5.56 6.48 9.11 S o.o3 o.l2 0.05 0.07 0.05 0.09 Bi 0.13 0.60 0.18 0.26 o.25 0.rI 0.72 Pb 31.63 t7.82 26.74 3t.37 29.47 26.16 24.39 Rh 0.00 0.00 0.00 0.00 0.05 0.00 sb 0.00 0.00 0.00 0.02 0.00 0.00 0.00 Te o.oo o.oo 0.00 0.00 0.00 0.00 Hg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sn 22.66 2t,16 15.40 23.39 23.89 23.88 Ag o.oo o.oo o.oo o.oo 0.00 0.00 0.00 Bi 0.61 0.rI o.22 4.23 0.05 0.00 Au 0.00 1.51 0.00 0.00 0.00 0.00 0.00 Pb r.43 7.76 11.46 2.61 2,15 l.4l Toral 99.75 91.36 98.!6 98.07 99.92 9E.66 99.52 Sb o.oo o.oo 0.00 0.00 0.00 0.00 (total: Hg 0.00 0.00 0.rl 0.14 o.l7 0.41 Atomic percent 4 atoms) Ag 0.00 0.21 0.11 0.00 0.00 0.00 PT 0.21r 0.378 0.271 0.201 0.235 0.299 0.331 Au 1.84 1.16 l.l3 n.d. n.d. n.d. As 0.004 0.000 0.001 0.000 0.000 0.008 0.000 Pd 2.674 2.5t3 2.661 2.648 2.652 2.655 2.5t1 Total 100.38 100.66 99.93 99.69 99.79 98.38 Ir o.o22 0.000 0.025 0.038 0.032 0.024 0.012 Atomic percent (rotal: 4 atoms) Cu 0.017 0.011 0.016 0.02 0.034 0.023 0.034 Ni 0.003 0.000 0.000 0.000 0.000 0.000 0.000 0.038 Pt 0.582 0.6?3 0.653 0.566 0.655 0,600 0.427 0.046 0.036 0.040 0.030 0.000 s 0.008 0.003 0.013 0.01E 0.010 0.000 0.000 As o.o?I 0.00? 0.001 0.055 0.011 0.000 Sn 4.213 0.557 0.276 0.2t6 0.246 0.289 4.404 2.144 2.279 Pd 2.254 2.253 2.216 2.287 Bi 0.003 0.015 0.005 0.007 0.006 0.003 0.01t I r 0.003 0.000 0.000 0.000 0.000 0.000 Pb 0.E06 0.455 0.685 0.815 0.746 0.669 0.620 Cu o.a22 0.020 0.o19 0.045 0.026 0.015 sb 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Ni o.ooo 0.000 0.000 0.001 0.000 0.oo8 Hg 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Fe 0.031 0.030 0.032 0.033 0.019 0.025 Ag 0.000 0.000 0.000 0.000 0.000 0.000 0,000 S o.oo5 0.019 0.008 0.01I 0.008 0.014 Au 0.000 0.041 0.000 0.000 0.000 0.000 0,000 Rh 0.000 0.000 0.000 0.000 0.002 0.000 Te 0.000 0.000 0.000 0.000 0.000 0.000 l-2: lsolated grain, 3-7: grain cciatod elth atollte ud Pb- ba - Sn 0.93E 4,912 4.671 0.966 1.006 1.007 ring kolubkits; trench 289.5. Bi 0.014 0.003 0.005 0.005 0.00r 0.000 Pb 0.034 0.192 0.289 0.062 0.052 0.034 sb 0.000 0.000 0.000 0.000 0.000 0.000 Hg 0.000 0.000 0.003 0.003 0.004 0.010 association;nickeline (Table 8) is either Pd-poor Ag 0.000 0.010 0.005 0.000 0.000 0.000 (4-8 wt.Vo; black in Fie. 5F) or Pd-rich (as high as Au 0.046 0.030 0.030 30 wt.Yo; dark grey in Fig. 5F). Their occurrence with mertieiteII and the unnamedphase may result Atokite associat€d with Pb - bearing totulskite and zvya - from unmixing of a solid solution. ginstevite (n.d. = not determined); trench 289.5. Pb-bearingminerals are common withthe PGM. The relative abundanceof Pb and Sn compounds with PGE and the observation that galena and altaite are found as very minor constituents of almost all PGE-rich rocks at Two Duck Lake may relate to the interaction of gabbroic magma relate to (Pd,Pt,Ni)2(Sb,Sn) and Pd2(Sn,Sb) (probable source of the PGE) and felsic metavol- describedby Ren & Huang (1973)and Yakovlev et canic xenoliths (possiblesource of Pb and Sn). Sn al, (1991), respectively.Majakite (Genkin e/ a/. may be held in magnetite and releasedto form 1976)and Sb-richmajakite, as well as nickelineand intermetalliccompounds when it was altered(Figs. Pd-bearing nickeline, also are members of this 4, 5), t29 HYDROTHERMAL PGE MINERALIZATION' TWO DUCK LAKE INTRUSION

TABLE 3. SELECTEDELECTRON.MAOFROBE DATAONKOTULSKITE

Weight p€rcelt Pr 0.79 0.65 o.5l o.tl 0.2t 1.33 l.r2 As o.oo o.oo o.oo 0.00 0,00 0.00 0.o0 Pd 36.70 38.t5 39.34 38.58 38.75 36.82 39.59 Ir 0.08 o.24 0.13 0,19 4.27 0.06 0.08 Cu 0.03 0.08 0.o0 0.o2 0.00 0.03 4.57 Pb Ni 0.00 0.oo a.o2 0.00 0.00 0.02 0,00 Fe 0.40 0.32 o.42 0.35 0.40 t.62 0.52 s 0.06 0.04 0.05 0.o2 0.04 0.27 0.07 Rh 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Te 38.76 38.19 37.t6 38.5t 39.44 28.t2 24.96 Sn o.oo o.oo o.oo 0.00 0.07 0.00 0.00 Bi 19.5E 20.2r 19.79 19.9t 19.60 30.2t 32.21 Pb 0.15 0.12 0.03 0.21 0.05 0.00 0.o2 sb 1.00 1.03 1.29 1.ll 1.27 t.o2 0.t7 Hg 0.00 0.00 0.00 0.01 0.04 0.10 0.00 Ag 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 99.55 99.73 99.44 99.86 100.r7 100.37 !00.03 Atomic percent (total: 2 atoms) Pt 0.010 0.009 0.00? 0.011 0.004 0.018 0.015 As o.ooo 0.000 0.000 0.000 0.000 0.000 0.000 Pd 0.928 0.933 0.942 0.926 0.923 0.89t 0.985 I r o.ool 0.003 0.002 0.003 0.004 0.001 0.001 Cu 0.001 0.003 0.000 0.001 0.000 0.001 o.o74 l\Ii 0.000 0.000 0.001 0.000 0.000 0.001 0.000 Fe o.ol8 0.015 0.019 0.016 0.01t 0.075 0.025 s 0.005 0.003 0.004 0.002 0.003 0.022 0.006 Rh 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Bi Pb Te o.775 0.764 0.756 0.772 0.182 0.586 0.5r8 Sn 0.000 0.000 0.000 0.000 0.001 0.000 0.000 Frc. 7. Clustersof kotulskite compositionsprojected onto Bi 0.239 0.241 0.241 o.244 0.238 0.376 0.408 the Te-Bi-Sb-Pb tetrahedronand on two triangular Pb 0.002 0.001 0.000 0.003 0.001 0.000 0.000 faces. sb 0.021 o.a22 0.027 0.023 4.026 0.022 0.019 Hg 0.000 0.000 0.000 0.000 0,001 0.001 0.000 Ag o.ooo 0.000 0.000 0.000 0.000 0.000 0.000

DISCUSSION 1-6: tlr@ diff€rilt gldns from &itl hole t5'E-2'14.08, 7: drill hole 43-319.5. Previous studies of sulfide assemblagesin the Two Duck Lake area (Puskas 1967, Wilkinson 1983, Good & Crocket 1989) have led some researchersto interpret that sulfide mineralization similar in origin to those was a magmatic process and that the present Cu-rich assemblageswere and Cu-enriched sulfide as- mineralogy resulted from exsolution from from other PGE at the Salt Chuck mine monosulfide solid-solution that had precipitated semblages, such as (Watkinson Watkinson& Melling 1992),New from gabbroic magma. However, the PGE- and 1990, (Loucks & McCallum 1978),Thierry Cu-rich sulfide assemblagesare unusualfor classic, Ramblermine Watkinson 1984),Shebandowan magmatic assemblages(Naldrett 1989)in that the mine (Patterson& Messinamine (Mih Iik et al. mineralogy is dominated by chalcopyrite and mine iMorton 1982), pluton (Dobrovol'skaya el cubanite. Pyrrhotite and magnetite with ilmenite 1974'1,and Murunsky lamellae (presumably of high-temperature mag- ol. 1985\. matic origin) are partly replaced, and many PGM The field, petrographic and mineral-chemical occur in veinlets,some of which cut partly altered data from the Two Duck Lake intrusion lead us to primary magmatic minerals. These types of fea- interpret that the concentrationsof the PGE and tures, among others, led Watkinson (1990) to Cu in the sulfide assemblagesresult from the conclude that the Two Duck Lake PGE and interaction of a fluid phasewith early-precipitated 130 THE CANADIAN MINERALOGIST

TABLE 4. SEI.ECTEDETECTRON-MCROPROBE TABLE 5. SELECTEDEITCIRON-MCROFROBE DATA ONLEAD BEARING KOTI.JISKNE DATA ON SPERRYI.ITE

V/eight percent Weighr percent Pt 7.21 r.34 1.33 t.52 t.24 0.79 r.03 Pt 55.01 st.77 i3.36 53.85 53.04 53.56 53.2! As 0.00 o.0o o.oo o.oo o.oo o.0o 0.00 As 39.58 42.t4 42.tt 42.93 43.22 43.31 42.2r Pd 35.4 36.66 36.63 37.94 38.5 3t.64 36.t7 pd O.OO O.0o O.O0 0.09 0.00 o.oo o.ol Ir 0.00 0.00 0.00 0.oo o.sl o.4l o.4l Ir 0.18 o.4o 0.65 0.16 0.80 0.69 o.El cu 0.47 0.34 0.47 0.56 0.41 o:79 0.20 Cu t.17 0.39 0.54 o.5o O.?9 o.t3 o.r5 Ni 0.00 0.00 o.o0 0.oo o.0o 0.00 0.00 Ni o.oo 0.oo o.oo o.oz o.0o o.o4 0.00 Fe 0.52 0.31 0.45 0.64 0,54 0.54 0.55 Fe O.37 A32 0.36 0.38 0.51 0.51 0.59 s 0.04 0.04 0.04 o.o0 o.ot o.o0 0.00 s 2.46 0.58 o.'E 0.52 0.48 0.54 0.49 Rh 0.00 0.00 0.00 0.00 0.oo 0.00 o.oc Rh 0.39 0.53 0.39 0.35 0.39 0.37 0.34 Te 25.59 24.07 24.49 2.s.79 zs.t1 2s.43 2s.4o Te 0.06 0.04 o.oo 0.00 0.00 o.oo o.oo Sa o.00 0.02 0.oo o.o1 0.oo o.o7 o.0o Sn 0.00 o.ol 0.00 o.o0 o.o? o.o0 0.oo Bi 27.65 28.19 27.65 26.08 24.77 25.68 26.7t Bi 0.OO 0.01 0.26 o.0o o.oo 0.01, 0.06 Pb 7.93 E.5o 7.36 9.4? 7.96 6.36 9.55 pb 0.31 a.2g 0.45 0.51 0.?6 0.36 0.48 sb 0.00 0.00 o.oo o.oo o.0o 0.oo o.o7 sb 0.00 o.o2 0.oo 0.01 o.o0 0.oo o.l9 Hg 0.00 0.00 0.00 o.oo o.oo 0.08 o.o0 l-otal 99.73 99.20 99,47 99.32 100.06100.21 Ag g.ri 0.14 o.ot o.0o 0.oO O.0O o.OO 99.26 Atomic percent (totql: 3 atoms) Total 99.02 99.61 98.42 100.96 99.48 to0.?9 t00.86 Atomic percent (total: 2 atoms) P! 0,918 0.933 0.92t 0.933 0.909 0.915 0.923 As r.7t9 1.935 1.93 1.936 1.92t 1.924 1.905 Pt o.olt 0.019 0.019 0.021 0.017 0.01I 0.014 Pd 0.000 0.000 0.000 0.003 0.000 0.000 0.000 As o.ooo 0.000 0.000 0.000 0.000 0.000 0.000 Ir 0.003 0.007 0.01I 0.003 0.014 0.012 0.014 Pd 0.912 0.945 0.946 0.948 0.971 0.962 0.936 Cu 0.070 0.021 0.029 0.027 o.o42 0.044 0.045 Ir o.ooo 0.000 0.000 0.000 0.011 0.006 0.006 Ni 0.000 0.000 0.000 0.001 0.000 0.000 0.000 Cu 0.020 0.015 0.020 0.a23 0.0r? 0.033 0.008 Fe 0.022 0.019 0.072 0.023 o.o3l 0.030 0.b36 Ni o.ooo 0.000 0.000 0.000 0.000 0.000 0.000 s 0.250 0.061 0.061 0.055 0.05 0.056 0.052 Fe 0.026 0.015 o.o22 0.030 0.026 0.026 0.027 Rh 0.012 0.017 0.013 0.01I 0.013 0.012 0.011 S o.oo3 0.003 0.003 0.000 0.007 0.000 0.000 0.002 0.001 0.000 0.000 0;000 0.000 0.000 Rh 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Sn 0,000 0.000 0.000 0.000 0.002 0.000 0.000 Te 0.550 0.517 0.527 0.537 0.529 0.528 0.537 Bi 0.000 0.000 0.004 0.000 0.000 0.000 0.001 Sn o.ooo 0.000 0.000 0.000 0.000 0.000 0.000 Pb 0.005 0.005 0.007 0.006 0.0r2 0.006 0.008 Bi 0.363 0.370 0.364 0.332 0.318 0.326 0.346 sb 0.000 0.001 0.000 0.000 0.000 0.000 0.005 Pb 0.105 0.1l2 0.098 0.10t 0.103 0.107 0.124 Sb o.ooo 0.000 0.000 0.000 0.000 0.000 0.002 Hg o.ooo 0.000 0.000 0.000 0.000 0.001 0.000 Specimen from trgnch 266 Ag 0.004 0.004 0.000 0.000 0.000 0.000 0.000

l-3: gBin Miated eith atokite and zyyrglmtevits, 4-6: bohred grar4 7: lsoluted gnin; tr@ch 289J. the probable explanation of the atokite- zvyagintsevitecompositions, especiallyin light of the occurrence of these Pb- and Sn-bearing minerals in veins and alteration assemblagesthat magmatic sulfides, oxides and silicates.The fluid cut primary magmatic minerals. was probably derived from a combination of Watkinson (1990)concluded that the enrichment magmatic fluid, and fluid from the breakdown of in Cu, PGE and other precious metals in some xenoliths of metamorphosedArchean rocks. This pegmatitic and vein-like depositsis directly related is compatiblewith the spatial relationshipof PGM to the occurrence of an alteration assemblage to rocks of coarse-grainedto pegmatitic texture, composed of calcic amphibole + epidote + with partly digested xenoliths and granophyric chlorite, commonlywith sericite,calcite and qvartz, patches, Cl-bearing mica and apatite, local as- Furthermore, there are very saline fluid inclusions semblagesof alteration minerals(chlorite, epidote, in some quartz and epidote grains from the host amphibole, sericite, calcite), and their occurrence rocks to someCu- and PGE-enrichedsulfides from in veinletsin marginal units of the Two Duck Lake the Coldwell Complex and other deposits(Watkin- intrusion. The occurrence of intricately zoned son 1990, unpubl. data); these are interpreted to hollingworthite was interpretedby Ohnenstetteret representtrapped fluid that reactedwith primary al. (1991)to have resultedfrom precipitation from minerals to produce the hydrated (and somewhat fluid of changingcomposition; this processis also oxidized) phases such as Fe-rich epidote, and HYDROTHERMAL PGE MINERALIZATION, TWO DUCK LAKE TNTRUSION t3l

TABIT 6. SELrcTEDELECTRON-MCROPROBE TABLE7. SELECTEDELECTRON-MICROPROBE DATA ON MERTIEITEtr DATA ON UNNAMEDPAII.ADITJM ARSENIDE AND PALLADIUM ANTIMOI.IIDEMINERAIS

Weigha percent 4 Pr 0.61 0.17 0.10 0.23 0.10 0.64 0.62 As 4.32 3.63 3.06 r.81 2.91 3.00 2.53 Vy'eight percent Pd 69.93 71.08 ?0.00 67.17 68.81 69.29 6t.13 P r o.oo 0.1I 0.00 0.53 0.89 o./tg Ir 0.20 o.tt 0.31 0.00 0.00 0.17 0.00 As 22.28 21.68 22.t4 9.36 11 .02 10.92 Cu 0.0! 0.04 0.0o 0.ll 0.o0 0.12 0.31 ?3.00 72.36 7 t.33 64.30 59.90 64.32 Ni 0.39 0.23 0.58 r.0l 0.t3 0.64 0.24 Pd 0.3,:l Fe 0.20 0.10 0.3t 0.t0 0.70 0.30 0.36 I r 0.00 0.23 0.04 0.76 0.61 s 0.09 0.03 0.10 0.22 0.t2 0.13 0.16 Cu 3.11 3.7r 2.98 0.02 0.35 0.13 Rh 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ni 0.08 0.14 0.10 0.38 4.36 0.47 Te 0.13 0.00 0.09 0,00 0.02 0.01 0.16 Fe 0.90 l.l? 0.95 0.35 0.30 0.28 o.oz 0.05 0.12 0.18 0.lz Sn 0.09 0.19 s 0.02 0.11 0.02 0.07 0.18 0.07 Bi 0.10 0.04 0.00 0.37 0.00 0.00 0.10 Rh 0.00 0.00 0.00 n.d. n.d. n.d. Pb 0.03 0.lE 0.14 0,00 0.23 0.02 0.00 0.00 0.00 0.01 0.01 0.02 sb 24.t9 24.80 25.44 2t.00 26.74 26.27 27.45 Te 0.00 Hg 0.00 0.00 0.00 0.00 0.00 0.00 0.05 Sn O.2l 0.28 0.36 0.06 0.11 0.16 Bi 0.00 0.11 0.00 0.00 0.00 0.05 Total 100.31100.50 100.25100.44 100.64 100.76 100.36 Pb 0.00 0.26 o.tz 0.00 0.33 0.33 Atomic percent (total: 1l atoms) Sb n.d. n.d. n.d, 23.32 22.32 22.74 Hg 0.00 0.33 0.29 0.00 0.00 0.00 Pr 0.037 0.0r0 0.006 0.014 0.006 0.039 0.038 As 4.679 0.573 0.4t2 0.284 0.45t 0.471 0.400 Total 99.66 100.49 98,34 99.16 100.38 100.29 Pd 7.74? 7.E97 7.769 7.491 7.576 1.661 1.592 I r 0.o12 0.01I 0.019 0.000 0.000 0.0r0 0.000 Atomic percent Cu 0.006 0.007 0.000 0.020 0.000 0.022 0.069 Ni 0.078 0.046 0.117 0.202 0.166 0.12E 0.048 Pr 0.000 0.004 0.000 0.009 0.014 0.007 Fs 0.042 0.021 0.080 0.168 a.147 0.063 0.076 As 1.976 r.907 L.994 0.397 o,144 0.455 s 0.033 0.011 0.037 0.0E1 o.044 0.048 0.059 Pd 4.560 4,482 4.523 1.922 1.698 1.885 Rh 0.000 0.000 0.000 0.000 0.000 0.000 0.000 I r 0.000 0.008 0.001 0.013 0.010 0.005 Te 0.012 0.000 0.008 0.000 0.002 0.001 0.015 Cu 0.332 0.385 0.316 0.001 0.017 0.006 Sn 0.009 0.002 0.005 0.012 0.01E 0.017 0.019 Ni 0.009 0.016 0.011 0.021 0.224 0.025 Bi 0.006 0.002 0.000 0.021 0.000 0.000 0.006 0.116 0.020 0.016 0.016 Pb 0.002 0.010 0.008 0.000 0.013 0.001 0.000 Fe 0.107 0.138 sb 2.912 2.409 2.46t 2.106 2.574 2.539 2.674 S o.oo4 0.023 0.004 0.007 0.017 0.007 Hg 0.000 0.000 0.000 0.000 0.000 0.000 0.003 Rh 0.000 0.000 0.000 Te o.ooo 0.000 0.000 0.000 0.000 0.000 0.003 0.004 SDcimm ftom drtu hole 43-320. Sn 0.012 0.016 0.020 0,002 Bi 0.000 0.003 0.000 0.000 0.000 0.001 Pb 0.000 0.008 0.004 0.000 0.005 0.005 sb 0.609 0.553 0.584 Hg 0.000 0.01I 0.010 0.000 0.000 0.000 precipitatedCu-rich and precious-metal(especially l-3: unnamedpalladium arsenide from drill hole 43-2104' Pd-bearing) minerals. Fluid inclusions have been 4-6: unnamed palladium antimonide from drill hole 43-320. documentedin PG.E-bearingrocks from Bushveld The structural formulae are calculated on the basis of 7 Watkinson (Ballhaus & Stumpfl 1986, Johan & and 3 atom! for the arsenide and antimonide, tespecrively (Farrow 1992) and 1987), Sudbury & Watkinson ( n.d.: not determined). New Rambler (Nyman et al. 1990). PGE- and Cu-rich sulfides in troctolite-gabbro of the GeordieLake intrusion, a northerly striking unit intruded into Coldwell Complex rocks, were describedby Good & Crocket (1989)and Mulja & Mitchell (1990).Cul(Cu + Ni) and Ptl(Pt + Pd) are about 0.92 and 0.05, respectively.Mulja (1989) tellurides. He ascribed a late magmatic origin to described sperrylite, kotulskite, merenskyite, the PGM and concluded that crystallization of michenerite,sopcheite, paolovite, guanglinite, and sulfide-rich magma was induced by magnetite other palladianarsenides, antimonides and bismuth precipitation and cyclic deposition of Cu-rich t32 THE CANADIAN MINERALOGIST

TABLE E. SELECTEDFI FCf,RON.MCROPROBE and biotite. Watkinson (1990)noted the similarity DATA ON MAIAKITE AND MCKELINE of some assemblagesfrom Geordie Lake that he had examined,to those from the Salt Chuck and New Rambler mines, and interpreted the Cu sulfides (chalcopyrite + bornite + digenite -r Weight percent chalcocite) and PGM to have resulted from replacement (essentially Pt 0.76 o.4o o.5t o.oo 0.00 0.34 of magmatic sulfides pyr- rhotite + chalcopyrite pentlandite) As 31.08 33.01 s1.92 s2.81 48.33 34,54 + by fluid enrichedin Cu+Pd+Pb+Ag+Au Pd 49.02 37.04 4.18 7.44 t2.35 30.55 after con- solidation of the silicate + sulfide assemblage. Ir 0.16 o.2l 0.25 o.l8 n.d. n.d. Mihdlik et al. (1974)described PGMin association Cu 0.81 O.O2 0.57 0.56 0.59 4.26 with similar alteration assemblages from Ni 16.69 23.2s 38.27 36.28 33.71 18.29 a hydrothermal environment Messina, Fe 1.04 0.1? 0.76 0.80 at South 0.75 4.77 Africa. S o.5o 0,26 o.4l 0.38 4.37 6,07 Johan & Watkinson (1987) proposed Rh n.d. 0.00 0.13 0.04 0.00 0.10 that the chlorine that could have complexedPGE Te o.l8 0.19 0.39 o.29 0.26 0.17 in fluids of the Upper Critical Zone, Bushveld Complex, Sn 0.00 O.O2 0.00 0.00 n.d. n.d. could originate from the breakdown of magmatic Bi o.t5 o.oo o.oo o.o2 0.00 0.02 Cl-bearing mica and apatite; the samemechanism Pb a.25 o.oo o.3l 0.36 0.00 0.00 was proposed independently by Boudreau el c/. Sb o.o4 ?.88 0.72 1.38 2.69 0.00 (1986) for PGE enrichment in rhe Bushveld and Hg n.d. n.d. 0.33 o.oo n.d. n.d. Stillwater complexes.The resultsof fluid-inclusion Total 100.68 102.43 100.?5 100.54 99.05 99.1l studieson host mineralsto PGE deposits(Ballhaus & Stumpfl 1986,Johan & Watkinson1987, Nyman Atomic percent et ol. 1990)provide confirmation that a fluid phase may well be necessarypart Pr o.o1o o.oo5 o.oo4 o.ooo 0.000 0.002 a of somePGE-enrich- ment processes. Wood's (1987) As t.024 t.o44 0.983 a.976 0.926 0.656 calculations revealed that the transport PGE Pd t.r3? 0.825 0.054 o.o9? 0.767 0.409 of as chloride complexesin Ir 0.002 0.003 0.002 0.001 supercriticalsolutions is one but not the solesuch possibility, becauseofthe appreciable Cu 0.031 0.001 0.012 0.012 0.013 0.095 solubility of other metals under these conditions. Ni o.7az 0.939 0.89r 0.856 0.824 0.443 Mountain & Wood (1987)concluded that the PGE Fe 0.046 o.oo? o.ol9 o.o2o 0.019 0.122 may be transported as chloride complexesin very s 0.039 0.019 0.017 0.016 0.017 0.269 acidic and oxidizedfluids, although other complex- Rh o.ooo o.oo2 o.oo1 0.000 0.001 ing agentsunder different conditions could not be Te 0.003 0.004 0.004 0.003 0.003 0.002 ruled out. Sassani& Shock (1990)confirmed that Sn 0.000 0.000 0.000 0.000 Pd was sufficiently soluble in fluids under ap- Bi o.oo2 o.ooo o.ooo o.ooo 0.000 0.000 propriate conditions of f(O), pH, Cl activity, P Pb 0.003 0.000 0.002 0.002 0.o00 0.000 and T to account for the petrographic featuresin Sb o.ool 0.153 o.oo8 o.ot6 o.032 0.000 PGE deposits; such petrographic features are Hg 0.002 0.000 similar to those outlined in this study and to those describedby Ballhaus & Stumpfl (1986) and as l: majakite, 2: Sb-bearing majakite, 3 and 4: nickeline, 5 reviewedby Mathez (1990) for the Stillwater and and 6: Pd-bearing nickeline from drill hole 43 - 320. The Bushveldcomplexes. structural formulae are calculated on the basis of 3 atoms We contend that the PGM of the Two Duck for majakitg and 2 atoms for nickeline (n.d.: not derermi - Lake intrusion may have precipitated from a ned). chloride-bearingsolution, probably under reducing conditions (Johan & Watkinson 1987), when it interacted with magnetite (and pyrrhotite) to producechlorite, epidote,carbonates, cubanite and chalcopyrite. The occurrenceof some PGM wilh argentiangold in fractures in altered magnetiteor at magnetite-chalcopyritecontacts at Two Duck sulfide and magnetite.However, Mulja noted that Lake is compatible with this mechanism. This whereassulfides are concentratednear the baseof reaction would not be unlike that proposedfor Au the intrusion, they do extend into the enclosing deposition in some Fe-rich rocks (Phillips et al. syenite. He also stated that the abundance of 1984),in which caseoxygen is releasedto the ore sulfide is correfatedwith the amount of amphibole fluid during magnetitereplacement. HYDROTHERMAL PGE MINERALIZATION, TWO DUCK LAKE INTRUSION 133

Ni As Frc. 8. TetrahedronPd-Ni-As-Sb and triangular facesshowing variation in mineral compositions. Filled circles: mertieite II, open circle: Sb-bearing majakite, asterisk:unnamed Pd2(Sb,As), filled square:nickeline, open square:Pd-bearing nickeline, open triangle: unnamedPd5As2, filled triangle: majakite.

CoNcLUSIoNS in the otherwise fresh and unmetamorphosed gabbroic rocks is epidote + actinolite + chlorite The platinum-group elementsin the easternpart + sericite + calcite. Some PGM occur in veins of the Coldwell Complex are not concentratedin within or at contactswith mineralsof the alteration assemblagesof tlpical magmatic sulfides at the assemblage. contact of the complexwith Archean rocks, but are The PGM are a diverse assemblage of located in Cu-rich sulfide assemblagesin the homogeneousto intricately zonedminerals, mainly separateTwo Duck Lake intrusion (Dahl et al. of Pd, Pt and Rh as intermetalliccompounds with 1986, unpubl. manuscript). Only one example of Sn, Pb, and as arsenides, antimonides and PGM enclosed with pentlandite flames in pyr- tellurides;they may be found in small veins,cutting rhotite, a probable magmatic association (Cabri altered, primary igneous minerals. Primary mag- 1981,Naldrett 1989),was found in the specimens matic Fe minerals (pyrrhotite and magnetite)were examined. Enrichment in Cu and PGE partly replaced, and most of the PGM were (predominantly Pd) occurs in coarse-grainedto precipitatedwhere this replacementoccurred. pegmatitic gabbroic rocks that contain abundant The field, petrographic and mineral-chemical mica and apatite (both Cl- and F-bearing), and data are interpretedas the result of the interaction partially digested xenoliths and granophyric of magmatic mineral assemblageswith a solution, patches derived from assimilation. The mineral probably a mixture of magmatic (deuteric) fluid assemblageadjacent to PcE-enriched Cu-sulfides and volatile speciesgenerated by the breakdownof t34 THE CANADIAN MINERALOGIST the abundant xenoliths, mainly felsic metavolcanic RowleNn, J.F., Larleuur, J.H.G. & rocks. This interaction coincidedwith local replace- Srrwnnr, J.M. (1979): Keithconnite, telluropal- ment of plagioclaseby chlorite, albite and epidote, ladinite and other Pd-Pt tellurides from the and of pyroxene by amphibole. The fluid was Stillwater Complex, Montana. Can. Mineral. 17, 589-594. capable of transporting PGE (especiallyPd), Cu and other metals, probably as chloride complexes, & Tnnrl, R.J. (1966):New palladium minerals of refining the sulfides to give higher contents of from Noril'sk, western Siberia. Can. Mineral. 8, Cu and preciousmetals, and of precipitatingPGM 541-550. (as well as galena, altaite, argentian pentlandite, calcite, and other minerals)when the composition Cunnrr, K.L. (1980):A contribution to the petrology of the fluid was modified during replacementof of the Coldwell alkaline complex, northern On- magnetite by chlorite and carbonate, and of tario. Geol. Surv. Can., Bull. 287. pyrrhotite by chalcopyriteand cubanite. Deul, R., McGonnN,J. & WernNsoN,D.H. (1986): The Coldwell Complex platinum-group-element AcKNowLEDGEMENTS deposit. 1. Geological relationships of layered gabbroic host rocks. Geol. Assoc, Can, - Mineral, We acknowledgeR. Dahl, M. Ohnenstetter,P. Assoc. Can., Program Abstr, ll, 61. Nagerl,C. Gilles,J. Breton,C. Fontaine,P. Jones, and I. Jonasson for their contributions to this DonnovoL'sreye, M.G,, Melov, V.S. & VleovrrN, N.V. (1985): Platinum and palladium minerals in researchproject. Z. Johan made many contribu- charoitic rocks. Dokl. Akad. Nauk SSSR 2E4, tions to this study of the PGE and arranged 438-M2 (in Russ.). excellenthospitalityfor DHW at BRGM-CNRS for sabbatical leave and research. We thank J. Fennow, C.E.G. & WerrrNsoN,D.H. (1992):Altera- McGoran, of Fleck ResourcesLtd., for unlimited tion and the role of fluids in Ni, Cu and accessto data on the Marathon property. Someof platinum-group-element deposition, Sudbury Ig- the funding was provided by Ontario Geological neous Complex contact, Onaping-Levack area, Survey ResearchAgreement 107 and by NSERC Ontario. Mineral. Petrol. 42 (in press). grant 47874 to DHW, and BRGM ResearchGrant RM15to DO. GrNrrN, A.D., Evsrrcreavn, T.L. & TnoNrva, N.V. (1976): Majakite, PdNiAs, a new mineral from copper nickel sulfide ores. Zap. Vses. Mineral, RrrrnENcrs Obshchest. 105, 698-703 (in Russ.).

BeLLueus,C.G. & Srurrarrl,E.F. (1986):Sulfide and Munav'rve, I.V. & Tnoxeva, N.V. (1966): platinum mineralizationin the Merensky Reef: Zvyagintsevite - a natural intermetallic compound evidencefrom hydrous silicates and fluid in- of palladium, platinum, lead and tin. Geol. clusions.Contrib. Mineral. Petrol. 94. 193-204. Rudnykh Mestoroz. 3,94-l0l (in Russ.).

BreuoorN,G., LeuneNr,R. & OnNeNsrrrrrn,D. Gooo, D.J. & Cnocrrr, J.H. (1989): PGE study of (1990):First report of platinum-groupminerals at the Geordie Lake and Marathon Cu-Ni-precious BIue Lake, Labrador Trough, Quebec. Can. metal deposits, Coldwell alkalic complex. Ontario Mineral. 28,409-418. Geol. Sum., Misc. Pap. 143, 186-198. (1987): BouoREau,A.E., MarHrz, E.A. & McCelr-uv,I.S. HEauaN, L.M. & Mecueoo, N. Isotope geochemistry I. (1986):Halogen geochemistry of the Stillwaterand of the Coldwell alkaline complex. Bushveldcomplexes: evidence for transportof the U-Pb studies on accessoryminerals. Geol. Assoc. - Abstr, 12, platinum-group elementsby Cl-rich fluids. ,I. Can, Mineral, Assoc. Con., Program Petrol.27.967-986. 54. (1978): la (1981): HrNoc, J. & ToNc, M. Automatisation de Cennr,L.J., ed. Platinum-groupelements: Electr. geology, microsonde. J, Microsc. Spectrosc. 3. mineralogy, recovery.Can. Inst. Min. 247-254. Metall., Spec. Vol. 23. JounN, Z. & WerrrNsoN, D.H. (1987): Phase fluide & CUEN,T.T. (1970: Stibiopalladinitefrom riche en Na-CI-H-O-N et son r6le dans le the type locality. Am. Mineral. 61, 1249-1254. concentration des 6l6mentsgroupe de platine et de la chromite: "Upper Critical Zone", complexe de LIFTAMME, J.H.G., Srrwanr, J.M,, Bushveld. 1rl Guides de prospection pour les RowLeNo,J.F. & CHrN, T.T.. (1975):New data on gisements de platinoides dans les complexes some palladium arsenides and antimonides. Can. ophiolitiques et stratifi6s. Commission des Mineral. f3, 321-335. Communautds Europdennes,Rapport finol, 6l-85. HYDROTHERMAL PCE MINERALIZATION, TWO DUCK LAKE INTRUSION I35

Kover-ENxrn,V.A., Evsrtcrgeve, T.L. & Bectzov, minerals and tellurides from the Geordie Lake V.D. (1978): Mertieite II - a palladium mineral intrusion, Coldwell complex, northwestern On- from exocontact copper-nickel ores from October tario. Can. Mineral. 28, 489-501' deposit. Geol. Rudnykh. Mestoroz 20, lll-l15 (in Russ.). & - (1991):The Geordie Lake intrusion, Coldwell Complex, Ontario: a palladium- and Lapurrre, I.P., Vvel'sov, L.N., GENrrN, tellurium-rich disseminated sulfide occurrence A.D. & Ysvsrroxrvsva, T.L. (1973): Tellurium derived from an evolved tholeiitic magma, Econ. minerals in copper-nickel sulphide ores at Talnakh Geol. 86,1050-1069. and Oktyabr (Noril'sk district). Intern. Geol. Rev. 15,1284-1294. Neronrrr, A.J. (1989): Mogmatic Sulfide Deposits. Oxford University Press, New York. Loucxs, R.R. & McCerlulr, M.E. (1978):Platinum- group minerals in the New Rambler copper-nickel NyvaN, M.W., SuErrs, R.W. & Booren, R.J. (1990): deposit, Wyoming: a preliminary report. P,'oc. Fluid-inclusion evidence for the physical and XIth Int. Mineral. Assoc. Meet. (Novosibirsk) l, chemical conditions associatedwith intermediate- 204-218. temperature PGE mineralization at the New Rambler deposit, southeastern Wyoming. Can. MaLpvsrry, A.Yu., Yusnro-Zarrnnove, O.YE. & Mineral. 2E, 629-638. DurenNe, L.S. (1978): Minerals of the series Pt3Sn-Pd3Sn.Intern. Ceol. Rev. 20, 229-235. OurrNsrerrnn, D. (1990): Mindralisations associAes aux comp lexes mafi ques-ultromafiques en domaine MnrHrz, E.A. (1990):Interactions involving fluids in ocdanique et continental. Thise Dr. is Sciences the Stillwater and Bushveld complexes: observa- Naturelles, Univ. Nancy, Nancy, France. tions from the rocks. .Ir Ore Deposition Associated with Magmas(J.A. Whitney & A.J. Naldrett, eds.). & WerrrNsoN,D.H. (1991):Platinum-group Rev. Econ. Geol. 4,167-119. mineralogy in Cu-rich sulfides, Two Duck Lake intrusion, Coldwell Complex, northwestern On- MrsAlrr, P., Hrrusrne, S.A. & DE Vu-lrrns, J.P.R. tario, Canada. Abstr. Sixth Int. Platinum Symp. (1975): Rustenburgite and atokite, two new (Perth) (in press). platinum-group minerals from the Merensky Reef, Bushveld igneous complex. Can. Minerol. 13, & Daur, R. (1991):Zoned hollingwor- 146-150. thite from the Coldwell Complex, nofthwestern Ontario. Am. Minerol. 76, JecorseN,J.B.E. & Hmusrne, S.A. (1974): Platinum-group minerals from a hydrothermal D.H. (1984): The -262. Parrrnsor, G.C. & WerrlrsoN, environment. Econ. Geol. 69. 257 geology of the Thierry Cu-Ni mine, northwestern Ontario. Can. Minerol. 22,3-ll. MrrcuELL, R.H. & Prerr, R.G. (1982): Mineralogy and petrology of nepheline syenites from the PsrLLrps,G.N., Gnovrs,D.I. & MentvN, J.E' (1984): Coldwell alkaline complex, Ontario, Canada. J. An epigenetic origin for Archean banded iron-for- Petrol. 23. 186-214. mation-hosted gold deposits. Econ. Geol. 79, t62-l'l l. MonroN, P. (1982): Archean Volconic Stratigraphy, and Petrology and Chemistry of Mafic and F. (1967):Ceology ofthe Port Coldwell area, Ultramafic Rocks, Chromite, ond the Sheban- Pusras, Thunder Bay, Ontario. Ontarto Dep. dowan Ni-Cu Mine, Shebandowan, Northwestern District of 10. Ontario. Ph.D. thesis, Carleton Univ., Ottawa, Mines, Geol. Circ. Ontario. RrN, Y.C. & HueNc, W.K. (1973): On some new platinum-group MourrarN, B.W. & Woop, S.A. (1987):Solubility and minerals and varieties of the (in Chinese)' transport of platinum-group elementsin hydrother- elements. Geochimica l, 23-30 mal solutions: thermodynamic and physical chemi- cal constraints, In Geo-platinum 87 (H.M. SesseNr,D.C. & Suocr, E.L. (1990):Speciation and Prichard, P.J. Potts, J.F.W. Bowles& S.J. Cribb, solubility of palladium in aqueous magmatic- eds.). Elsevier, London (57-82). hydrothermal solutions. Geology 18, 925-928.

MuLrn, T. (1989): Petrology, Geochemistry, Sulphide WemNsoN, D.H. (1987): Platinum-group element and Platinum-Group Element Mineralization of the potential in alkaline rocks ofnorthwestern Ontario. Geordie Lake Intrusion, Coldwell Complex, On- Ont. Geol. Surv., Open File, Final Rep.: Res. tcrfo. M.Sc. thesis, Lakehead Univ., Thunder Bay, Agreement GRI07. Ontario. (1990): Platinum-group minerals in Cu-rich & MrrcurLL, R.H. (1990): Platinum-group sulfides from some North American mafic- 136 THE CANAD]AN MINERALOGIST

ultramafic complexes. 2nd Symp. Modern Coldwell Complex, Northwestern Ontario. M.Sc. Mineral., Mineral. Soc. Korea, 37-51. thesis, Carleton Univ., Ottawa, Ontario.

- & Daul, R. (1988): Platinum-group mineral Wooo, S.A. (1987): Thermodynamic calculationsof precipitation from fluids in pegmatitic gabbro: the volatility of the platinum group elements Two Duck Lake Intrusion, Coldwell Complex, (PGE): the PGE content of fluids at magmatic Ontario. /n Geo-platinum87 (H.M. Prichard, P.J. temperatures. Geochim. Cosmochim. Acta 51, Potts, J.F.W. Bowles& S.J. Cribb, eds.).Elsevier, 3041-3050. London (273). Yerolrv, Yu.N., Dtsrrsn, V.V., MtrnoneNov, F.P,, & Mnr-rNc, D.R. (1992):Hydrothermal origin RezHrv, S.A., GnornovsKAyA,T.L. & Vrsnovsrv, of platinum-group mineralization in low-tempera- N.N. (1991): Mineralogy of PGE in the mafic- ture copper sulfide-rich assemblages,Salt Chuck ultramafic massifs of the Kola rcgion. Mineral, intrusion. Alaska. Econ. Geol.87. 175-184. Petrol., 43, l8l-192.

WrlKrNsolr, S.J. (1983): Geology and Sulphide ReceivedJanuary4, 1991, revisedmanuscript accepted Mineralization of the Marginal Phases of the May 24, 1991.