Flint Creek Prospect, Ruby District, Yukon-Koyukuk Borough, Alaska, USA

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Tributaries of Flint Creek along which there are prospects or mines include Granite Creek (RB025), Eldorado Creek (RB026), Root Creek (RB032), Gold Run (RB033), Glen Gulch (RB030), Lucky Creek (RB034), and Birch Creek (RB035). Additionally, tributaries Straight Creek (RB029), Crooked Creek (RB031), and Lucky Creek (RB027) tributary of Birch Creek contain gold.
Location: Flint Creek is location 17 of Cobb. Flint Creek is a northeast-flowing tributary of the Sulatna River. The better prospects are found on the bench along the west side of the creek, between Gold Run and Eldorado Creek. The coordinates given mark the approximate locations of the better prospects found in section 5, T. 13 S., R. 18 E. of the Kateel River merdian. This placer area corresponds to location 17 of Cobb (1972 [MF405]) although Cobb locates the Flint Creek prospect approximately 1 mile further north, just downstream of Gold Run Creek. As a result, accuracy is within 1 1/2 miles.
Geology: Flint Creek drains the contact zone of a granitic body with phyllite and quartzite (Mertie, 1936). Prospectors first identified gold on Flint Creek in 1911 (Maddren, 1912). There is no data concerning any actual mining at Flint Creek, and the area probably was not mined. Later years of prospecting resulted in poorer results than in 1911 (Mertie, 1936; White and Stevens, 1953). Cassiterite was found in heavy mineral concentrates. Concentrates of gravels derived from the granite also contained a uranium-thorium mineral (possibly uranothorite), sphene, allanite, ilmenite, magnetite, and zircon (White and Stevens, 1953). Bismuth was reported in a spectrographic analysis of uranothorite, but no bismuth mineral was found (White and Stevens, 1953).
Workings: Flint Creek was prospected between 1911 and at least 1936. Chapman and others (1963) speculated that the results were probably never good enough to warrant mining.
Age: Quaternary.

Commodities (Major) - Au; (Minor) - Bi?, Sn, Th, U
Development Status: Undetermined.
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a).

References

Chapman, R.M., Coats, R.R., and Payne, T.G., 1963, Placer tin deposits in central Alaska: U.S. Geological Survey Open-File Report 239, 53 p. Cobb, E.H., 1972, Metallic mineral resources map of the Ruby quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-405, 1 sheet, scale 1:250,000. Cobb, E.H., and Chapman, R.M., 1981, Mineral occurrences (other than mineral fuels and construction materials) in the Kantishna River and Ruby quadrangles, Alaska: U.S. Geological Survey Open-File Report 81-170, 94 p. Eberlein, G.D., Chapman, R.M., Foster, H.L., and Gassaway, J.S., 1977, Map and table describing known metalliferous and selected nonmetalliferous mineral deposits in central Alaska: U.S. Geological Survey Open-File Report 77-168-D, 132 p., 1 sheet, scale 1:1,000,000. Maddren, A.G., 1912, The Ruby placer district: U.S. Geological Survey Bulletin 520-J, p. 287-296. Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. Mertie, J.B., Jr., and Harrington, G.L., 1916, Mineral resources of the Ruby-Kuskokwim region, in Brooks, A.H., and others, Mineral Resources of Alaska, Report on Progress of Investigations in 1915: U.S. Geological Survey Bulletin 642-H, p. 223-266. White, M.G., and Stevens, J.M., 1953, Reconnaissance for radioactive minerals in the Ruby-Poorman and Nixon Fork districts, west-central Alaska, in 1949: U.S. Geological Survey Circular 279, 19 pages.

Mineral List

Cassiterite

Gold

Thorite var: Uranothorite

3 entries listed. 2 valid minerals.