Structural controls on Ni-Cu sulfide mineralization and metal mobility at the Garson Mine, Sudbury

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The Garson Mine is one of several nickel-copper mines in the world-class Sudbury mining camp in Ontario.  Two thirds of Canada's annual nickel production is from Sudbury mines.  The nickel-copper deposits occur at the base of the 1850 million years old Sudbury Igneous Complex.  They formed as heavy sulphide metal droplets segregated from the cooling magma and accumulated along the floor of the igneous complex.  Several millions of years after crystallization of the complex, the Sudbury rocks were faulted, folded, and sheared during tectonic collisional growth of the North American continent.  Several deposits, including the Garson deposit, were deformed during this tectonic event.  This changed the shape of the deposits, their metal content, and distribution of sulphide minerals.  At the Garson Mine, Ni-Cu sulfide mineralization occurs within two main shear zones.  The degree to which shear deformation has affected the nature and distribution of the mineralization is uncertain.  Mineralization either remained largely in place during deformation, or was mobilized during ductile flow of sulfide minerals as high-temperature malleable pastes and during transport of metals and sulfur in solution within hydrothermal fluids that migrated along the shear zones.  The proposed research will establish the degree to which sulfide minerals have been affected by this deformation and will determine the relative importance of solution transport versus ductile solid flow during mobilization of the sulfides.  It will further characterize favorable structural sites for the concentration of metals along the shear zones and will identify geochemical enrichment /depletion signatures that can be used to vector toward nickel-copper mineralization.