Caracterisation de la mineralisation en nickel-cuivre-elements du groupe platine des indices de la region du lac a Paul, Suite anorthositique de Lac St-Jean (French text, Quebec)

The subject of this master's project is the characterization and study of the origin of the Ni-Cu sulfide mineralization of the Lac à Paul area located in the northwestern part of the Lac Saint-Jean anorthositic suite. The Ni-Cu sulfide mineralizations are magmatic in origin and are associated with the margins of a Meso-proterozoïc anorthosite intrusion. The average values obtained for the massive and semi-massive sulfides of the Lac à Paul area are in the order of 0,66% Ni, 1,2% Cu, 0,06% Co and 55 ppb Pd. The values for Pt generally fall under the detection limit.; The extremely low concentration of platinium group elements (PGE) of the samples and of Ni in the olivines of the Lac à Paul area reflects the important magmatic evolution undergone by the different lithologies of the study area. Only dykes of dioritic composition seem to constrain the order of crystallisation of some of the lithologies of the Lac à Paul area. The composition of the parental sulfide liquid is similar to the disseminated sulfides with a 100% sulfide recalculated average of 1,6% Ni and 1,7% Cu, yielding a Ni to Cu ratio of 1:1. The S/Se ratio (S/Se ratios of 8000 to 26 000) suggests an external source of the sulfur.; Comparison between the Lac à Paul showings, Voisey's Bay, Lac Volant and some Norwegian showings indicates similar tectonic setting which favoured an early segregation of the sulfides. The main differences are: a kilometer size intrusion; no evidence of re-enrichment of the mineralization by multiple magma injections; syn- to late-tectonic emplacement of the mineralization; and a significant evolution of the ore-bearing lithologies.