Unnamed Occurrence (ARDF - EA127; north of South Fork bridge), Fortymile District, Southeast Fairbanks Borough, Alaska, USA

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Location: This unnamed occurrence is at the waterline on the west bank of the South Fork of the Fortymile River; it may be under water during times of high water. The occurrence is about 1.5 miles north of the South Fork bridge on the Taylor Highway, and about 1.5 miles south of the mouth of Walker Fork, on the western edge of section 31, T. 27 N., R. 19 E., of the Copper River Meridian. The location is accurate.
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

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.

Mineral List

Gold

Pyrite

Quartz

3 entries listed. 3 valid minerals.