Abstract The Brucejack intermediate-sulfidation epithermal Au-Ag deposit, located 65 km north of Stewart, BC, forms part of a well-mineralized, structurally controlled, north-south gossanous trend associated with Early Jurassic intrusions straddling the Late Triassic-Early Jurassic Stuhini-Hazelton Group unconformity in the Sulphurets mineral district. Mining of the deposit commenced in mid-2017 after a long history of exploration dating back to the 1880s. Mineralization is hosted in deformed Lower Jurassic island-arc volcanic rocks of the Hazelton Group exposed on the eastern limb of the Cretaceous McTagg anticlinorium. High-grade Au-Ag mineralization was formed from ~184 to 183 Ma in association with a telescoped, multipulsed magmatic-hydrothermal system beneath an active local volcanic center. Precious metal mineralization occurs as coarse aggregates of electrum and silver sulfosalts in steeply dipping, E- to SE-trending quartz-carbonate vein stockwork zones cutting low-grade intrusion-related phyllic alteration. Epithermal vein development is interpreted to have occurred during the waning stages of Early Jurassic sinistral transpression in a compressive arc environment, followed by a limited Cretaceous deformation overprint.

Abstract The Cordilleran orogen of western Canada and Alaska records tectonic processes than span over 1.8 billion years, from assembly of the Laurentian cratonic core of Ancestral North America in the Precambrian to sea-floor spreading, subduction, and geometrically linked transform faulting along the modern continental margin. The evolution of tectonic regimes, from Proterozoic intracratonic basin subsidence and Paleozoic rifting to construction of Mesozoic and younger intraoceanic and continent-margin arcs, has led to diverse metallogenetic styles. The northern Cordillera consists of four large-scale paleogeographic realms. The Ancestral North American (Laurentian) realm comprises 2.3 to 1.8 Ga cratonic basement, Paleoproterozoic through Triassic cover successions, and younger synorogenic clastic deposits. Terranes of the peri-Laurentian realm, although allochthonous, have a northwestern Laurentian heritage. They include continental fragments, arcs, accompanying accretionary complexes, and back-arc marginal ocean basins that developed off western (present coordinates) Ancestral North America, in a setting similar to the modern western Pacific basin. Terranes of the Arctic-northeastern Pacific realm include the following: pre-Devonian pericratonic and arc fragments that originated near the Baltican and Siberian margins of the Arctic basin and Late Devonian to early Jurassic arc, back-arc, and accretionary terranes that developed during transport into and within the northeastern paleo-Pacific basin. Some Arctic realm terranes may have impinged on the outer peri-Laurentian margin in the Devonian. However, main-stage accretion of the two realms to each other and to the Laurentian margin began in mid-Jurassic time and continued through the Cretaceous. Terranes of the Coastal realm occupy the western edge of the present continent; they include later Mesozoic to Cenozoic accretionary prisms and seamounts that were scraped off of Pacific oceanic plates during subduction beneath the margin of North America. Each realm carries its own metallogenetic signature. Proterozoic basins of Ancestral North America host polymetallic SEDEX, Cu-Au-U-Co-enriched breccias, MVT, and sedimentary copper deposits. Paleozoic syngenetic sulfides occur in continental rift and arc settings in Ancestral North America, the peri-Laurentian terranes, and in two of the older pericratonic Arctic terranes, Arctic Alaska, and Alexander. The early Mesozoic peri-Laurentian arcs of Stikinia and Quesnellia host prolific porphyry Cu-Au and Cu-Mo and related precious metal-enriched deposits. Superimposed postaccretionary magmatic arcs and compressional and extensional tectonic regimes have also given rise to important mineral deposit suites, particularly gold, but also porphyries. Very young (5 Ma) porphyry Cu deposits in northwestern Vancouver Island and sea-floor hotspring deposits along the modern Juan de Fuca Ridge off the southwest coast of British Columbia show that Cordilleran metallogeny continues.