Mobilization of komatiite-associated Ni-Cu-(PGE) mineralization in the Southern Manneville fault zone, Southern Abitibi subprovince, Quebec

Abstract

The Cubric showing and Marbridge deposit occur in the 2714 ± 2 Ma La Motte-Vassan Formation, 20-25 km north of Malartic, Québec. Mineralization at the Cubric showing is hosted by a silicate-magnetite facies iron formation as well as gabbro, but the high Ni/Cu and Ir/Pd ratios of the mineralization suggest that it formed from a komatiitic magma, similar to the mineralization at the historic Marbridge deposit. Normal abundances of most metals in the mineralization in the gabbro suggest that it was mechanically mobilized into the gabbro as a high-temperature monosulfide solid solution, whereas low abundances of Cr and Ir-Ru-Rh in the mineralization in the iron formation suggest that Ni-Cu-Pt-Pd-Au and other metals were mobilized into the iron formation by metamorphic-hydrothermal fluids. The host rocks and country rocks have experienced two phases of deformation during regional metamorphism, and it is likely that the mineralization was mobilized from unexposed/eroded mineralized cumulate komatiites during this deformation and metamorphism, which occurred after emplacement of the younger 2680 ± 1.5 Ma gabbro.