Abstract

High concentrations of palladium and platinum (average 75 ppm and 4 ppm, respectively) are associated with copper ores at the New Rambler mine. The ore deposit is of hydrothermal origin and occurs in metagabbroic rocks at the intersection of a mylonite zone, several closely spaced faults, and a major shear zone.Three principal mineral assemblages have been defined in the hypogene ore paragenesis: (1) an early assemblage consisting mainly of pyrite, with magnetite, pyrrhotite, pentlandite, and chalcopyrite as accessories; (2) and (3) copper-rich assemblages representing the main stage of ore deposition and consisting principally of chalcopyrite + pyrrhotite but differing in accessory platinoid and base metal minerals. Thermochemical data on mineral compatibilities suggest deposition of asesmblage 1 at temperatures in the vicinity of 335 degrees C or somewhat higher and the principal mineralization with deposition of copper- and platinoid-rich assemblages at temperatures somewhat below 335 degrees C. Ten platinum and palladium minerals are recognized in the ore. Eight of these minerals are bismutho-tellurides or tellurides. Pt and Pd apparently occur in the ore principally as their own minerals.A comparative study of the distribution and geochemical behavior of the precious metals Pt, Pd, Rh, Au, and Ag in the weathered portions of the deposit has shown that Pt and Rh are substantially enriched in the strongly oxidized ore horizons, possibly due to supergene processes. Pd and Ag have been extensively mobilized from the upper levels during weathering. Ag has undergone dramatic enrichment in the supergene sulfide zone, but Pd apparently has been removed from the system.

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