Abstract

During a search for the source of a quartzite glacial erratic carrying galena, newly published aeromagnetic maps attracted attention to an unsuspected metasedimentary series. Subsequent prospecting in this belt uncovered quartzite boulders containing finely-disseminated sphalerite together with minor galena, pyrite, and pyrrhotite. These boulders formed a glacial train some 10 miles in length flanked by pyrite-bearing quartzite boulders along a length of 40 miles. Samples of the sphalerite-bearing float assayed up to 14% Zn and 4 1/2% Pb.The surficial geology showed that the valley along which the float was found represents a melt water channel that had exposed the boulders from the till.The source of the float was found to be at the east side of the southwest end of George Lake where bedrock was covered by drift ranging from 0-100 feet in thickness.Surface drilling indicated a deposit of 5 million tons averaging 2.65% Zn and 0.35% Pb, which included a higher grade core of 2.9 million tons averaging 3.67% Zn and 0.53% Pb. These estimated tonnages are based on shallow drilling and are assumed to extend to a maximum depth of 400 feet. The grade of material found at the source of the float was much lower than that indicated by assays of the erratics. This difference was ascribed to irregular sampling of the float.The metal contents of the adjacent rock units are listed and compared with average results from other similar types elsewhere.The trace element content of the sphalerite indicates certain similarities when compared with sphalerites from "Mississippi Valley Type" deposits.The sulfides are considered to have been deposited syngenetically. Metamorphism subsequently resulted in some minor redistribution of ore minerals as shown by the inclusion of sphalerite grains in metamorphic garnets.

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