The Bralorne-Pioneer gold-bearing veins were deposited from low salinity fluids at 300°C to 400°C and 1.25 kbar to 1.75 kbar (Leitch, 1990). The vein style, structure, mineralogy, and alteration are all similar to those defined for orogenic gold deposits (Groves et al., 1998).
The Bralorne Pioneer gold deposit, therefore, belongs to a well-recognized group of deposits referred to as mesothermal, orogenic or greenstone-hosted quartz-carbonate gold vein deposits. These deposits include the Mother Lode district in California and most of the greenstone-hosted gold deposits in the Canadian Shield, including the Timmins, Val d'Or and Red Lake camps. These deposits are quartz-carbonate veins hosted in moderately to steeply dipping brittle-ductile shear zones and, locally, in shallow dipping extensional fractures.
The gold-quartz veins form an approximate en echelon array. They have strike lengths of as much as 1,500 m between bounding fault structures, and extend to at least 2,000 m in depth, with no significant changes in grade or style of mineralization recorded. Ores consist mainly of ribboned fissure veins with septa defined by fine-grained chlorite, sericite, graphite or sulphide minerals. Massive white quartz tension veins also comprise some of the ore, although thinner connecting cross-veins are generally sub-economic. The fissure veins tend to be larger, thicker, and host the higher gold grades. The most conspicuous alteration mineral is bright green, ........
