Distribution of gold mineralization at the New Britannia Mine in Snow Lake, Manitoba, implications for exploration and processing
Fulton, Pamela J.
Gold is distributed in three ways in the New Britannia Mine, as free gold, as gold in the form of inclusions in sulphide minerals and as "invisible" gold within sulphide minerals. Invisible and inclusion gold are interpreted as being deposited before free gold, along with the sulphide minerals pyrite and arsenopyrite. Free gold was found overgrowing pyrite and arsenopyrite. Free gold grains have a composition of 40-99% gold with 1-60% silver and trace amounts of copper and mercury. Free gold in association with sulphide minerals ranges in size from 15 to 75 microns, free gold in association with only silicates and calcite ranges in size from 15 to 190 microns. Inclusion gold ranges in size from 3 to 16 microns. Arsenopyrite usually contains higher concentrations of "invisible" gold than pyrite. Ion imaging shows this gold can be zoned within arsenopyrite and heterogeneous within pyrite. These distributions are interpreted as growth features, with lower concentration gold fluids depositing blebs of gold in pyrite and higher concentration gold fluids depositing the continuous zones in arsenopyrite. The Dick and the Ruttan Zones of the New Britannia Mine and the No. 3 Zone produced favorable results that would indicate good recoveries in the mill. The Birch zone produced results that would indicate low recoveries in the mill, and in the Boundary Zone results indicate good recoveries from H1, 5 & 6, but relatively poor recoveries in H2, 3 & 4. Results suggest that gold amenable to conventional milling techniques is to be found in proximity to faults with associated arsenopyrite, where the invisible gold in arsenopyrite has been remobilized to produce free gold. (Abstract shortened by UMI.)