Massive sulphide - associated gold: Brunswick No. 12 Mine, Bathurst, New Brunswick
University of New Brunswick
Two different gold occurrences were observed at Brunswick no. 12 Mine. In both instances, the gold occurs as electrum. Electron microprobe analysis determined that the electrum grains were of different compositions. Sample BMS12-SD is gold rich electrum (Au91Ag9) while electrum in sample 48233(1) is silver rich Au49Ag51) Sphalerite and electrum compositions indicated that the partial pressures of sulphur differ for these two electrum samples and also differ from the partial pressure of sulphur for associated sphalerites. These electrum samples were found to occur at two different stratigraphic levels. The gold rich electrum was found in stratigraphically lower units such as the stockwork ore veins in the hangingwall (footwall) sediments. The silver -rich electrum, on the other hand, was found in chert/pyrite iron formation which is a stratigraphica lly high unit. It was determined that only the electrum of sample 48233(1) would be liberated by the grinding process at Brunswick no. 12 Mine.