Unnamed Occurrence (ARDF - MG078; in tributary to the Tatina River), McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This unnamed occurrence is a mineralized gossan in shale of the Lower Cretaceous Kahiltna Flysch about 500 meters below the contact between the Upper Triassic to Lower Jurassic Tatina River Volcanics and Lower Cretaceous, Kahiltna Flysch (Bundtzen, Harris, and Gilbert, 1997). The gossan strikes east-west across a steep bedrock canyon subparallel to bedding and is about 3 meters thick; the strikelength was not measured. Disseminated chalcopyrite and pyrite were identified in one hand sample, but most mineralization is oxidized. One grab sample of mineralized shale contained 1,200 ppm zinc, 109 ppm copper, 9.3 ppm cadmium, and 7 ppm molybdenum.
Workings: The reporter investigated the site during geologic mapping of the area in 1984 (Bundtzen, Harris, and Gilbert, 1997). One grab sample of mineralized shale contained 1,200 ppm zinc, 109 ppm copper, 9.3 ppm cadmium, and 7 ppm molybdenum.
Alteration: None.
Reserves: None.
Commodities (Major) - Zn; (Minor) - Cd, Cu, Mo
Development Status: No
Deposit Model: Polymetallic replacement (Cox and Singer, 1986; model 19a).
Mineral List
3 entries listed. 2 valid minerals.
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References
Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 p., 1 sheet, scale 1:125,000.
