AN OVERVIEW OF CHALCOPHILE ELEMENT CONTENTS OF PYRRHOTITE, PENTLANDITE, CHALCOPYRITE AND PYRITE FROM MAGMATIC NI-CU- PGE DEPOSITS

We have compiled the trace-element concentrations in base-metal sulfides (BMS; pyrrhotite, pentlandite, chalcopyrite and pyrite) from magmatic Ni-Cu-PGE deposits to highlight how they record ore-forming processes. Among the samples are some of the most studied Ni-Cu-PGE deposits (Aguablanca, Duluth, Jinchuan, Noril’sk-Talnakh, Sudbury, Voisey’s Bay, Bushveld, Lac des Iles, Stillwater, Great Dyke). Crustal assimilation by parental liquids may be constrained using the concentration of slightly chalcophile elements (D^{sulf liq/sil liq} from 1 to 10) in BMS. This is because the effect of the R-factor is smaller on elements with lower D^{sulf liq/sil liq}. Pentlandite from ores that formed from more contaminated liquids have higher As/Se and Sb/Se ratios. The BMS from Ni-Cu deposits and PGE-dominated deposits can be separated based on concentrations of highly chalcophile elements (D^{sulf liq/sil liq} above 1000). The higher R-factors in PGE-dominated deposits relative to Ni-Cu deposits lead to higher concentrations of these elements in the sulfide liquid, and thus in the BMS. The BMS also record the fractional crystallization of the sulfide liquid. The concentrations of elements compatible with monosulfide solid solution (MSS) and intermediate solid solution (ISS) are lower in BMS from more fractionated ores, whereas concentrations of incompatible elements increase in BMS from more fractionated ores. Pyrite formed by exsolution from MSS has higher Rh, Ru, Ir and Os relative to co-existing pyrrhotite, whereas pyrite formed by alteration of the BMS assemblage inherits the Rh, Ru, Ir and Os contents of the pyrrhotite it replaced. Finally, BMS can be used as indicator minerals since their trace-element chemistry can be used to discriminate their source. Pentlandite from Ni-Cu deposits has much lower Rh and Pd concentrations than those from PGE-dominated deposits, pyrite from magmatic Ni-Cu-PGE deposits has higher Co/Sb and Se/As relative to pyrite from hydrothermal deposits. Chalcopyrite from magmatic deposits has much higher Ni and lower Cd concentrations than those from hydrothermal deposits.