Abstract

High-grade Ni-Cu-Co and precious metal mineralization forms footwall veins in close proximity (<~750 m) to the base of the Sudbury Igneous Complex. Successful exploration for these economically significant sulfide ore deposits benefits from an understanding of the geologic processes associated with their formation, notably within the framework of meteorite impact cratering. Based on examination of drill core and drilling logs of Vale’s Capre 3000 ore zone, we delineate petrographic and microstructural characteristics of sulfide veins and the adjacent host rocks. We show that transport, emplacement, and modification of sulfides are controlled by the dynamic conditions in the thermal aureole of the Sudbury Igneous Complex during early stages of crustal relaxation following impact cratering. This process accounts for the following observations: (1) occurrence of sulfide veins at preexisting structural discontinuities, (2) spatial distribution and thickness of veins, and (3) distinct spatial distribution of partial melting and static recrystallization textures in footwall rocks in the vicinity of sulfide mineralization. We suggest that the identification of high-temperature mineral textures in the footwall rocks lends itself as an exploration tool for footwall deposit identification.

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