Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Magmatic Ni-Cu sulfide ores may contain platinum-group elements (PGE) that are recoverable as by-products of mining these ores. It is of interest to understand which minerals host the PGE for two reasons: 1) to efficiently extract the PGE; 2) to understand the petrogenesis of the ores. The distribution of PGE from magmatic Ni-Cu-PGE deposits at the Creighton Mine, Sudbury, Canada has been investigated. A PGE mass balance has been carried out by comparing whole rock PGE concentrations to the sum of solid solution concentrations of PGE in base metal sulfides (BMS) and the associated PGM. Calculations show that the BMS host the majority of Ru and Pd (80-95%) and Os (65%), but Ir, Rh, Pt and Au are absent from the BMS. In contrast, Ir, Rh and Pt are hosted by sulfarsenide-bearing PGM within the BMS. These comprise irarsite (IrAsS)-hollingworthite (RhAsS) cores, containing some Pt, Os and Ru, and Ni-cobaltite (NiCoAsS) rims. Pentlandite is the main host for Pd because Pd diffuses from nearby Cu-rich phases into early-forming coarse-grained pentlandite. Pd-bearing PGM (michenerite PdBiTe), Pt-bearing PGM (sperrylite PtAs2) and Au (electrum AuAg) are present but rare.