Platinum-group minerals in the raglan Ni-Cu-(PGE) sulfide deposit, Cape Smith, Quebec, Canada

Platinum-group minerals (PGM) have been identified in samples from the Katiniq and Zone 2 orebodies, Raglan deposits, Cape Smith. northern Quebec. The most abundant PGM (in area %) is sperrylite, comprising a third of all the grains. Overall, sudburyite and merenskyite make up the majority of the remaining PGM, with the others consisting of moncheite, temagamite, a Pd-Bi telluride. a Pd-Pb-Bi telluride and a Pt-Os-Ru-bearing Rh sulfarsenide, probably hollingworthite. Sperrylite is more abundant at Katiniq. and merenskyite is more abundant in Zone 2. The majority of the PGM are associated with Sulfide minerals and are either completely enclosed within sulfides, or at a sulfide-silicate boundary. Platinum-bearing PGM are the predominant PGM associated with pyrrhotite and pentlandite in MSS ores. In addition, the PGM in chalcopyrite-rich ores are commonly Pt-bearing, with Pd-bearing PGM concentrated in secondary veins. A notable proportion of the PGM is associated either with carbonate. 13% by area within Zone 2, or with maucherite (nickel arsenide), 9% by area at Katiniq. The platinum-group elements. especially Pd, have been mobilized during both extensive low-temperature alteration of the ultramafic rocks in the greenschist facies and the shearing that affected these deposits. This fact is demonstrated by the occurrence of sudburyite and. more rarely. sperrylite within carbonate in secondary veins and in shear zones. At Katiniq, sudburyite is associated with maucherite, and Pd occurs in solid solution within the maucherite grains, both minerals likely to have been produced as a result of postmagmatic alteration. The morphology of the PGM has been extensively modified during this low-temperature alteration, with sperrylite crystals losing their euhedral form where parts of the crystal are in contact with altered silicates. These PGM may also have indented outlines where they are cross-cut by needles and laths of actinolite-tremolite. In terms of processing and beneficiation, 20% of the PGM grains may currently be unrecoverable owing to their complete enclosure in gangue minerals. Only 17.5% are fully recoverable as a result of their enclosure within chalcopyrite and pentlandite.