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Black Ridge Prospect, Ketchikan District, Ketchikan Gateway Borough, Alaska, USA

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Location: This prospect is known only from U.S. Bureau of Mines (1977) claim records. Its approximate location is at an elevation of about 200 feet, approximately 0.2 mile inland from the southwest coast of Revillagigedo Island, and midway between the mouths of Carroll Inlet and Thorne Arm. The site is in section 16, T. 76 S., R. 92 E., of the Copper River Meridian. It corresponds to loc. 82 in Elliott and others (1978). The location is probably accurate within about 0.1 mile.
Geology: The principal country rock in this part of Revillagigedo Island is a stock of Cretaceous quartz diorite (Berg and others, 1988). On the north and south, the stock intrudes diverse metamorphosed Mesozoic or Paleozoic sedimentary, volcanic, and intrusive rocks. In part, the southern boundary of the stock also is a moderately northeast-dipping thrust fault and blastomylonite zone (Berg, 1982). The outcrop area of the stock includes roof pendants and inclusions of dioritic metaplutonic rocks and pelitic metasedimentary rocks. Berg and others (1988) assigned these rocks a Mesozoic or Paleozoic premetamorphic age. According to U.S. Bureau of Mines claim records (1977), this prospect, which appears to be in the Cretaceous quartz diorite stock near its south contact, was staked for Ag, Au, Co, and Cr. No other information about it has been made public.

Commodities (Major) - Ag, Au, Co, Cr
Development Status: None

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Berg, H.C., 1982, The Alaska Mineral Resource Assessment Program; guide to information about the geology and mineral resources of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Circular 855, 24 p. Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map I-1807, 27 p., scale 1:250,000. Elliott, R.L., Berg, H.C., and Karl, S.M.,1978, Map and table describing metalliferous and selected non-metalliferous mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-73B, 17 p., 1 sheet, scale 1:250,000. U.S. Bureau of Mines, 1977, Claim map, Ketchikan quadrangle: U.S. Bureau of Mines Map 120, scale 1:250,000.

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