Gold Mineralization Patterns at the Doyon Mine (Silverstack), Bousquet, Quebec

Special Volume, Vol. SV 24, No. 1982, 1982

The Doyon Mine gold deposits in Bousquet township occur in a felsic pyroclastic horizon of the Archean Blake River Group. Initial work outlined zone number I, within a lapilli tuff, and zone number 2, mainly within the underlying blocky tuff Zone number 2 has been mined by open pit since February 1980. The lapilli tuff around number I is intensely altered to sericite and carries abundant pyrite; gold is fine grained in the silicate minerals in close association with pyrite. In zone number 2, there are two principal types of gold: the first occurs as fine grains disseminated within the pyroclastic rocks along silicate and pyrite grain bounderies, and as inclusions in pyrite; the second type occurs within quartz-carbonate stringers, parallel or at an angle to the foliation. The gold mineralogy is more complex in this type, as telluride minerals more common than in the first type. The volcanic-sedimentary rock assemblage has a widespread chemical alteration pattern characterized by sodium and calcium depletion, potash and sulphur gain, and localized magnesium and alumina gain. This alteration band developed during the evolution of the volcanic pile enclosing the goldbearing zone. Fluid inclusion studies on quartz from the quartz-carbonate stringers indicate a COrrich fluid with increasing density. · A two-stage evolution of this gold mineralization is envisaged: an initial deposition of gold in volcanogenic sediments followed much later by the evolution of metamorphic fluids. The initial gold concentration was essentialy redistributed within the deposit, with probably some local enrichment or reconcentration, but without new addition of gold.
Keywords: Gold, mineralization, Doyon Mine, gold deposits, volcanogenic sediments, metamorphic fluids