Petrography of the gold-bearing vein rocks from Bissett area, southeastern Manitoba
Amukun, Samuel Erasmus
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Vein rocks were examined from the Bissett, Manitoba area, and 250 samples collected from 50 localities. Fifty-nine samples were chemically analysed for 26 elements, and thin sections were prepared from 20 samples. Four generations of gold-bearing quartz injections are located in steeply dipping fractures, shears and faults. The veins occur mostly in rocks of the Rice Lake group (greenstones), in which the most favorable structural areas are noses and axial planes of anticlines. The quartz in these veins exhibits a wide range of colors, textures and transparencies. Other minerals in the vein rocks include chlorite, epidote, carbonates, some feldspars and sulfides (mostly pyrite, arsenopyrite, chalcopyrite, galena and sphalerite). The vein rocks are surrounded by alteration zones. Gold occurs as a native element associated with quartz and carbonates, or within country rocks. The greatest amounts occur as particles in the clear microcrystalline quartz. Some gold is disseminated in pyrite and arsenopyrite, and partially replaces them. There is an enrichment of Si, Co, Cr, Cu, Pb and Ba, and a depletion of Zn, Ni, S Mn, Zr, Ti, P, Li, Rb, and Sr in veins compared to either rocks that contain them or the equivalent average crustal rocks.