Petrography of Four Rock Units Exposed in the Campbell Red Lake Mines, Ontario
Campbell Red Lake Mines is a major gold producing mine located in Balmertown, Ontario on the Precambrian Shield. There are four main rock units recognized at the mine: “andesite”, “altered rock”, “siliceous rock”, and “Campbell diorite”. These units have been presumed to be igneous in origin and intruded by lamprophyre, quartz-feldspar porphyry, and grey dikes. Samples of the four rock units were taken from the mine and analyzed by macroscopic, microscopic, and x-ray diffraction techniques. Field and laboratory observations suggest that the “andesite”, “altered rock” and “siliceous rock” are of sedimentary rather than igneous origin and are now metasediments. The preponderance of quartz and the presence of calcite and dolomite are evidences of sedimentary origin. These fine-grained foliated rocks belong to the greenschist facies and are products of low-grade regional metamorphism. The changes in the mineralogic composition and texture within the limits of the "altered rock" and “andesite” are also evidences of sedimentary origin. Gold is found in the quartz-carbonate veins of the “andesite” which is predominately in contact with the siliceous rock. The siliceous rock may be the source of silica for the “andesite”. The "Campbell diorite" however, may be of igneous origin and the source of fluids involved in alteration. The massive structure of the "Campbell diorite" and the relict pyroxene in the rock show that the rock is a metamorphosed igneous rock (saussurite rock).
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