Geological, geophysical and geochemical studies around the Allan Lake carbonatite, Algonquin Park, Ontario |
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| Authors: | KL Ford RNW Dilabio AN Rencz |
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| Abstract: | The Allan Lake carbonatite, found in 1977 by an airborne gamma-ray spectrometric survey, is a small (about 0.4 km2), unexposed, ankeritic-sideritic, REE-enriched carbonatite. Minor phases include biotite silico-carbonatite, orthoclase-dolomite carbonatite, apatite-rich carbonatite and narrow zones of intense chloritization. A poorly exposed fenitized aureole dominated by abundant hematitic veining and minor acmite-bearing veins grades into a brecciated border zone surrounding the carbonatite. Radial, breccia, lamprophyre and hematite-rich dykes are present within the fenitic aureole.Glacial erosion has produced a dispersal train of lithologically distinctive till which covers an area of approximately 10 km2 and is characterized by anomalous (10–20 times background), concentrations of Ba, Nb, Th, Ce, La, Zn, Mn and Fe; and elevated (5–10 times background) concentrations of Y, P, Cu, Pb, Mo, Co and U. This dispersal train is detectable by airborne and ground gamma-ray spectrometry, till geochemistry, boulder mapping and biogeochemistry. |
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