PLATINUM-GROUP MINERALS FROM THE DEEP COPPER ZONE OF THE STRATHCONA DEPOSIT, SUDBURY, ONTARIO

Among the different ore zones of the Strathcona deposit, in the Sudbur y district, Ontario, the Deep Copper Zone has the highest concentratio ns of platinum and palladium. Most of the Pt and Pd is not present in solid solution in base-metal sulfides and magnetite: rather, they occu r as platinum-group minerals (PGM). These include niggliite, froodite, insizwaite, paolovite, sperrylite, michenerite, sobolevskite and a pa lladium chloride. The PGM, up to 50 mum across, are intergrown with te llurides (hessite and altaite), native bismuth and bismutite. They occ ur mainly along grain boundaries and in microfractures in sulfide mine rals, magnetite. and silicates. Mass-balance calculations indicate tha t sperrylite and niggliite are the most abundant platinum-bearing mine rals, and froodite and michenerite are the most abundant palladium-bea ring minerals. Textural relationships suggest that the deposition of t he PGM occurred mostly tater than that of base-metal sulfides and magn etite. The occurrence of Pd chloride associated with other PGM suggest s that Cl may have been an important agent for the transport and depos ition of Pd. Other important elements involved in the precipitation of the PGM include Bi, Te, As and Sn.