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Gamma Spectrometry in the Northwest Territories, Canada for Polymetallic Au-Co-Cu-Bi-W

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An exciting new polymetallic deposit has been discovered at Lou Lake, Northwest Territories, where a recent, multiparameter airborne geophysical survey has delineated a large 3 by 4 km area of intense potassium enrichment (fig. A) coincident with low eTh/K ratio (fig.B) and high total field magnetic anomalies.

The anomalous area contains numerous Au-Co-Cu-Bi-W bearing arsenopyrite-pyrite-magnetite veins and disseminations, localized along the unconformity between early Proterozoic metasediments/ granites and overlying, gently dipping rhyolitic volcanics. Fig. C shows one of these polymetallic veins bordered by potassically altered rhyolite, Preliminary drill indicated resources for the Bowl Zone, in the Lou Lake area, as of January 1997, include 42 million tonnes grading 0.85g/t gold, 0.11% bismuth, 0.1% cobalt, 0.05% copper and 0.03% tungsten oxide.

Using a GR-320 spectrometer the degree of alteration in the extensive hydrothermal system can be quickly detected and quantified. Traverses along selected grid lines in the mineralized zone (fig. D) produced in-situ assays of up to 15% K in rocks which would normally contain less the 4% K.

As with many deposit types, low eTh/K ratio in the hydrothermally altered rocks permits distinction of K anomalies that have exploration significance from those related solely to lithological variations. These patterns, in conjunction with ongoing metallogenic, geological and other geophysical studies, have helped industry focus on an important new exploration target, comparable to the giant Olympic Dam deposit in South Australia.