Project: The nature and origin of the Brucejack high-grade epithermal gold deposit, British Columbia, Canada
Epithermal gold deposits host a significant portion of the world’s total known near-surface gold endowment and are thus an important target in mineral exploration. Despite supplying a growing fraction of global gold production and receiving increased scientific attention from the mining industry in recent years, discovery rates for new epithermal gold deposits have been in decline since the 1990s. The reasons for this decline are manifold, but a reoccurring issue in many studies is that available genetic models, which are essential guides to exploration, still do not satisfactorily explain the formation of many epithermal and related hydrothermal gold deposits.
Pretium Resource’s Brucejack property in the Stewart-Eskay Creek mining district of northwestern British Columbia is host to one of the highest grade and best exposed intermediate sulphidation epithermal gold deposits in the world (individual electrum bearing quartz-carbonate veins grade up to 41,000 g/ton Au). My project aims to determine the origin of high-grade gold mineralisation at Brucejack and produce a step-by-step reconstruction of the magmatic-hydrothermal history of the deposit by petrographically and chemically (including isotopically) characterising the ore mineralisation and associated hydrothermal alteration, determining the composition of the original mineralising fluids through fluid inclusion analysis, and reconstructing the physicochemical conditions that controlled gold mineralisation through thermodynamic analysis and quantitatively testing plausible models of ore formation (including testing whether boiling-mediated nanoparticle suspensions, or colloids, played a role in greatly increasing the capacity of the ore-forming fluid to carry gold). In addition, the well-explored nature of epithermal gold mineralisation on the Brucejack property, combined with its close proximity to well-explored, world-class copper-gold-molybdenum porphyry deposits (Snowfields and Kerr-Sulphurets-Mitchell), will, through comparative study, allow for the testing of possible genetic links between epithermal and spatially associated higher-temperature porphyry deposits in general. If successful, my project will improve on existing models for the genesis of epithermal gold deposits and the strategies that guide their exploration.