Unnamed Occurrence (ARDF - MD012), McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence consists of heavily altered, limonitic rhyolite breccia of Sischu Volcanic Field (Miller and others, 1980; Moll and others, 1981; Clautice and others, 1993). Mineral occurrence is inferred to be Late Cretaceous, based on isotopic age of Sischu Volcanics (Moll and others, 1981). Clautice and others (1993) and Miller and others (1980) report anomalous zinc, rubidium and cerium values from the limonitic breccia zones.
Workings: Clautice and others (1993) and Miller and others (1980) report anomalous zinc, rubidium, and cerium values from limonitic breccia zones.
Age: Mineral occurrence is inferred to be Late Cretaceous, based on isotopic age of Sischu Volcanics (Moll and others, 1981).
Alteration: Extensive clay and chalcedonic alteration.
Commodities (Major) - Zn; (Minor) - Ce, Rb
Development Status: No
1 entry listed.
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Clautice, K.H., Bowman, N.D., Clough, J.G., Gilbert, W.G., Kline, J.T., Smith, T.E., and Blodgett, R.B., 1993, Land selection Unit 8 (Kantishna River, Ruby, and Medfra quadrangles); References, lead isotope, geochemical and major oxide data: Alaska Division of Geological and Geophysical Surveys, 42 p., 1 sheet, scale 1:250,000. Miller, T.P., Moll, E.J., and Patton, W.W. Jr., 1980, Uranium and thorium rich volcanic rocks of the Sischu Creek area, Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-803, 9 p. Moll, E.J., Silberman, M.L., and Patton, W.W. Jr., 1981, Chemistry, mineralogy, and K-Ar ages of igneous and metamorphic rocks of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811-C, 15 p., 2 sheets, scale 1:250,000.