Structural controls and modification of the Big Bulk Cu-Au porphyry system, Stewart District (northwest BC): constraining the geologic environment during porphyry emplacement
Porphyry Cu-Au-Mo systems, especially those formed along continental active margins, are generally considered to have formed in contractional tectonic environments of crustal thickening, surface uplift and rapid exhumation (e.g., Sillitoe, 2010). The tectonic environment of porphyry systems formed in island arcs, such as those located within the Stikine terrane of northwestern BC, are not as well understood. The Stewart district is a ~170 km long, linear belt of mineralization within the Stikine terrane and hosts the Kerr-Mitchell-Sulphurets deposit, the largest undeveloped gold reserve in Canada. Recent regional and detailed mapping studies in the district have presented compelling evidence for emplacement of these systems into an extensional regime, which contradicts the classic contractional model. My research seeks to test this model and its applicability to the region as a whole by reconstructing the Early Jurassic basin geometry, structural architecture and stress regime that provided permeable pathways for magmatism and hydrothermal fluids at several less well studied mineralized systems within the district. If the observations indicate that the porphyries were deposited in extensional basins, a new exploration model for porphyry emplacement can be implemented which will benefit exploration in Canada.