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

Résumé

A detailed LA-ICP-MS study has been carried out on base-metal sulfides (BMS) from the Aguablanca deposit (Spain) in order to establish the role of the BMS as carriers of PGE and the processes controlling their distribution. The distribution of the PGE is largely governed by the fractionation of the sulfide liquid. IPGE and Rh are concentrated in pyrrhotite and pentlandite of the semi-massive ore (i.e., mss cumulate). These phases have lower IPGE and Rh values in the disseminated and chalcopyrite-veined ores, but pentlandite and chalcopyrite host higher Pd contents. Laser ablation analyses support the interpretation of chalcopyrite veinlets as representing a Cu-rich sulfide liquid. Palladium is present in solid solution within pentlandite, whose concentrations are a function of the textural type (flames host lesser amounts than the granular pentlandites) and the presence of chalcopyrite in the samples (pentlandites related to chalcopyrites are enriched in Pd). Pd diffusion into pentlandite from mss and possibly iss was the key mechanism in its enrichment in pentlandite. Finally, this study demonstrates that pyrite hosts appreciable amounts of Rh and Pt, and therefore pyrite should not be overlooked as a potential carrier of PGE in Ni-Cu-(PGE) ore deposits.