Distribution of Some Noble Metals in Sulfide and Oxide Minerals in Strathcona Mine, Sudbury

Abstract

<p>Neutron activation analysis has been carried out to determine the concentrations of Pd, Ir, Pt, and Au in coexisting pyrrhotite-magnetite-chalcopyrite-pentlandite from deep zone ore of Strathcona mine, Sudbury. The concentration profiles of Pd, Ir, and Au from disseminated sulfide along the 2750 cross-cut of the mine were also measured.</p> <p>It has been shown that the dominant mode of occurrence of these metals is solid solution in host sulfide and oxide minerals at average concentration ranges from 1.5 p.p.m. for Pt to 3 p.p.b. for Ir. The distribution of the noble metals is considered in terms of magmatic temperature and subsolidus events. At magmatic temperatures, all four noble metals are found to fractionate fairly strongly into pyrrhotite solid solution: at subsolidus conditions, Pt strongly prefers chalcopyrite and Pd and Au, pentlandite. The basis of these effects are discussed in the light of thermodynamic, molecular orbital, and diffusion theories.</p> <p>The implications of the concentration profiles of Pd, Ir, and Au in the petrogenesis and origin of the Strathcona sulfides are discussed.</p>