Distribution of gold and arsenic in turbidites at Harrigan Cove, Nova Scotia: implications on gold mineralization.

Gold, As and Sb were determined by NAA in host rock greywackes and slates, auriferous quartz veins and arsenopyrite from Harrigan Cove, Halifax County (M.A.87M/5784). The same metal suite was also analysed in slates from the Goldenville deposit, Guysborough County. The veins are typical of the turbidite-hosted gold-quartz veins of the Goldenville formation, the lower sandy flysch member of the Cambro-early Ordovician Meguma group of SE Nova Scotia. Harrigan Cove greywacke and slate are slightly enriched in Au and strongly enriched in As (as arsenopyrite) relative to similar rocks in barren Meguma terrain. Greywacke is the main sink for As, whereas quartz veins carry the highest Au contents. Gold and As correlate strongly in greywackes and slates, but not in quartz veins. In the host rocks, arsenopyrite is the main gold concentrator mineral. The metal distributions support a polygenetic origin for the mineralization. Early As- and S-bearing fluids introduce arsenopyrite and sulphides, mainly into greywackes. Gold is concentrated by these minerals and later remobilized with large quantities of silica in the very early stages of deformation through pressure solution which generates a spaced cleavage. These silicic fluids and their metals are injected by hydraulic fracture, mainly into slate, forming auriferous bedding-parallel quartz veins. (Authors' abstract) -A.W.H.