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

Résumé

Most models of how PGE deposits form suggest that a sulphide liquid collects the PGE and concentrates them in a zone sufficiently rich in PGE to be exploited. If this were the case then one might expect the PGE to be present in solid solution in magmatic base metal sulphides (BMS) such as pyrrhotite (po), pentlandite (pn) and chalcopyrite (ccp). However, in most ores studied to date PGM account for a large part of the PGE budget. The origin of these PGM could be: exsolution from the BMS, crystallization from the sulphide liquid, or precipitation from a deuteric fluid. Sulphide droplets from MORB represent natural examples of rapidly quenched sulphide liquid. Thus, it is possible that exsolution did not occur and that deuteric processes were not important. Furthermore, the sulphide liquid would not have fractionated sufficiently to crystallize PGM. To test these ideas we are determining PGE and chalcophile element contents of sulphide droplets in MORB glasses.