Geochronological and Regional Metallogenic Investigations in the Bralorne – Bridge River Mining District (parts of Nts 092d, J, I, O), Southwestern British Columbia: Project Rationale 1

Orogenic gold de pos its are char ac ter ized by struc tur ally con trolled, low-sul phide quartz veins that formed prox i mal to deep-crustal faults in greenschist-fa cies meta mor phic ter ranes. These de pos its, pre vi ously re ferred to as mesothermal, greenstone-hosted, shear-hosted and turbidite-hosted de pos its, have a wide range of as so ci ated min er al iza tion styles and as so ci ated met als that are de pend ent upon the depth (pres sure) and tem per a ture at which they formed in the crust, as well as the char ac ter of the hostrocks. Whereas the ver ti cal ex tent of an orogenic lode gold de posit is known to span sev eral kilo metres at an in di vid ual mine, the range of pos si ble for ma tion depths for these de pos its ex tends from the deep hypozonal (15– 20 km) to the shal low epizonal (2–5 km) en vi ron ments (Groves et al., 1998). This rec og ni tion led to the de vel op ment of the con tin uum model (Colvine, 1989; Groves, 1993; Groves et al., 1998), whereby a di verse range of de pos its is ac com mo dated within a sin gle de posit model, with fea tures spe cific to their tem per a ture and depth of for ma tion. For ex am ple, a range of Alas kan orogenic gold de pos its with vari able min er al og i cal as sem blages and struc tural styles (Goldfarb et al., 1997, 2005) would in clude those of the hypozonal Alaska-Ju neau de pos i t (15 km) , mesothermal Chugach Terrane de pos its (5–10 km) and epizonal Donlin Creek de posit (2–3 km), all of which are clas si fied by the orogenic de posit model.