Yousure; Yushur Prospect, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: The Yousure prospect is a swarm of north to northeast-trending, quartz-sulfide veins and veinlets that cuts black shale and siltstone of the Upper Cretaceous, Kuskokwim Group, and a mafic dike altered to silica-carbonate minerals (Miller and Bundtzen, 1994; Bundtzen and Miller, 1997; Miller, Bundtzen, and Gray, 2005). The individual quartz-sulfide veins and veinlets vary from 0.4 to 1 inch thick; the zone they occur in is about 100 feet wide and can be traced for about 160 feet. Deep red cinnabar crystals up to about 5 millimeters in diameter are locally abundant in the quartz vein. Grab samples contain up to 15.0 percent cinnabar and 5.0 percent stibnite. Grains of yellow scheelite were identified in one sample. Grab samples of mineralization contained more than 1.0 percent mercury, 0.46 percent antimony, more than 1.0 percent arsenic, 50 parts per million (ppm) tungsten, and 5,000 ppm barium (McGimsey and others, 1988).
Workings: The Yousure prospect was discovered by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in 1985 (McGimsey and others, 1988).
Alteration: Silica-carbonate alteration of mafic dikes; silicification.
Commodities (Major) - Hg, Sb; (Minor) - As, Ba, W
Development Status: None
Deposit Model: Either hot spring Hg or Silicate-carbonate Hg deposit (Cox and Singer, 1986; m
4 entries listed. 4 valid minerals.
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Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286. Gray, J.E., Gent, C.A., Snee, L.W., and Wilson, F.H., 1997, Epithermal mercury-antimony and gold-bearing vein lodes of southwest Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 287-305. McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet. Wells, J.T., and Ghiorso, M.S., 1988, Rock alteration, mercury transport, and metal deposition at Sulphur Bank, California: Economic Geology, vol. 83, p. 606-618. White, D. E., and Robinson, C. E., 1962, Sulphur Bank, California, a major hot spring quicksilver deposit, in Engel, A.E.J., James, H.L., and Leonard, B.F., eds., Petrologic studies: A volume in honor of A.F. Buddington: Boulder, Colorado, Geological Society of America p. 397-428.