Spring Ridge Prospects, McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Location: The Spring Ridge prospects consists of two areas of mineralization about 1,000 feet apart on northwest spurs at 1,900 feet in elevation (580 m) in Section 25, T. 23 S., R. 23 E., of the Kateel River Meridian. Location is accurate within 1,000 feet (304 m).
Geology: At the Spring Ridge prospects, smithsonite-bearing gossans occur on two adjacent ridge spurs about 1,000 feet (300 m) apart, and about 30 feet by 50 feet (9 m by 15 m) in size, in the lower part of the Whirlwind Creek Formation of Dutro and Patton (1982); this is unit 'Dda' of Andrews and Rishel (1982). Mineralization in both areas occur in well developed solution breccias in dolomite. Host rock is inferred to be Latest Silurian based on fossils; however, the age of the mineralization is unknown. A grab sample from surface exploration along the eastern spur yielded 2.72 percent zinc and 0.14 percent lead. Two grab samples from the western spur contained 9.07 percent zinc and 12.00 percent zinc respectively; no lead was detected in either sample (Andrews and Rishel, 1982).
Workings: The Spring Ridge prospects were found by WGM Inc. and Patino Ltd. during base metal exploration conducted in the 1970s on lands selected by Doyon Ltd. (Andrews and Rishel, 1982). A grab sample from surface exploration along the eastern spur yielded 2.72 percent zinc and 0.14 percent lead. Two grab samples from the western spur contained 9.07 percent zinc and 12.00 percent zinc respectively; no lead was detected in either sample.
Age: Host rock is inferred to be Latest Silurian based on fossils (Dutro and Patton, 1982); however, the age of the mineralization is unknown.
Alteration: Secondary dolomite in fractures.
Commodities (Major) - Zn; (Minor) - Pb
Development Status: No
Deposit Model: Southeast Missouri Pb-Zn (Cox and Singer, 1986; model no. 32a) or Mississippi V
2 entries listed. 2 valid minerals.
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Andrews, Tom, and Rishel, John, 1982, Annual Report for 1981, Reef Ridge I-to-XIII Project Areas, Kuskokwim Block, Alaska: Anchorage, Alaska, WGM Inc., Project Report 4, 45 p., 2 sheets, scales 1:63,360 and 1:20,000. (Report held by Doyon, Limited, Fairbanks, Alaska.) Dutro, J.T. Jr., and Patton,W.W. Jr., 1982, New Paleozoic formations in the northern Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, p. H13-H22. Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811, one sheet at 1:250,000 scale. Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.