Role of Fluid State Mobilization during Metamorphism of the Henderson Ore Bodies, Chibougamau, Quebec, Canada

Abstract

The Henderson Cu-Au deposit occurs in discordant structures within the anorthosite zone of the Doré Lake Complex. The Doré Lake Complex is intruded into volcanic rocks of the Chibougamau greenstone belt on the southeastern side of the Superior Province. Massive to disseminated sulfide ores are associated with sericite, carbonate, chlorite and/or chloritoid schists within a large 'shear zone'. These ores show structural and textural evidence of intense deformation, recrystallization, and metamorphic mobilization.The deposit comprises not only sulfide schist ore with alternating sulfide and schist layers, but also 'hydrothermal' vein-type segregation ore. The latter is characterized by sulfide-bearing quartz-calcite veins that occur in the 'shear zone' and in the subsidiary fractures adjacent to it.The sulfide schist and vein types of ores can be attributed to partly solid state mobilization combined with fluid state mobilization from a pre-existing ore, and is an excellent example of extensive fluid state mobilization of sulfides under relatively low-grade regional metamorphism. It is suggested that fluid state mobilization can play an important role during the metamorphism of a pre-existing sulfide body, especially in the presence of differential stress accompanied with rupture. The deformational features of the ore are the important indication for syn- and/or pre-metamorphic origin of the ore.