Unnamed Occurrence (ARDF - EA127; north of South Fork bridge), Fortymile District, Southeast Fairbanks Borough, Alaska, USA
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Geology: This prospect is in upper Paleozoic greenschist-facies metasedimentary and metavolcanic rocks (Werdon and others, 2001). Light-gray to black chert (silicified limestone?) is cut by white quartz stringers and discontinuous pyrite veins. Portions of the outcrop have a banded appearance, and other portions are distinctly brecciated with a light matrix and dark clasts. Some fractures are filled with an unidentified yellow-orange material. Overall, brecciation is minor, and it probably is associated with quartz veining. An assay of a representative sample of quartz-veined and pyrite-rich chert (silicified limestone?) breccia contains 65 ppm gold (Szumigala and others, 2000).
Age: The veins cut upper Paleozoic rocks.
Alteration: Possible silicification of limestone?
Commodities (Major) - Au
Development Status: None
Mineral List
3 entries listed. 3 valid minerals.
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References
Szumigala, D.J., Newberry, R.J., Werdon, M.B., Finseth, B.A., Pinney, D.S., and Flynn, R.L., 2000, Major-oxide, minor-oxide, trace-element, and geochemical data from rocks collected in a portion of the Fortymile mining district, Alaska, in 1999: Alaska Division of Geological and Geophysical Surveys Raw-Data File 2000-1, 24 p., 2 sheets, scale 1:63,360. Werdon, M.B., Newberry, R.J., and Szumigala, D.J., 2001, Bedrock geologic map of the Eagle A-2 quadrangle, Fortymile mining district, Alaska: Alaska Division of Geological and Geophysical Surveys Preliminary Interpretive Report 2001-3b, 1sheet, scale 1:63,360.