Latitude: 64°55'42"N
Longitude: 141°39'50"W
Location: Crooked Creek is an 8-mile-long north tributary of the Seventymile River. The placer deposits are located in the lower 2 miles of Crooked Creek, downstream of Eldorado Creek; the coordinates are about 1 mile upstream of the mouth of Crooked Creek, in section 9, T. 1 N., R. 30 E., of the Fairbanks Meridian. Crooked Creek is locality 29 of Cobb (1972 [MF-393]), locality 19 of Eberlein and others (1977), and locality 12 of Burleigh and Lear (1994).
Geology: The rocks along Crooked Creek are primarily Cretaceous to Pliocene conglomerate with lesser sandstone and shale (Clark and Foster, 1971; Foster, 1976). Trachyte porphyry and other dikes cut the sedimentary rocks (Clark and Foster, 1971). Mining in 1936 took place about 2 miles upstream of the mouth of the creek, where the paystreak was about 270 feet wide (Mertie, 1938). In general, 3 to 4 feet of muck covered the gravel, which is generally 5 to 6 feet thick, but locally as much as 8 feet thick. The gravel consists of well-rounded cobbles of rather uniform size; some boulders reach 2 feet in diameter. Gold was recovered from the entire section of gravel, rather than concentrated near bedrock. The gold was fine-grained, and some small silver nuggets were also recovered. Three assays of placer gold collected from Crooked Creek in 1934 and 1935 averaged 902 parts of gold and 92 parts of silver per thousand, the highest grade in the Seventymile area (Mertie, 1938). Mertie (1942) later reported 20 assays of placer gold from Crooked Creek that averaged 908 parts of gold and 88 parts of silver per thousand. Galena and hematite were also recovered from sluice boxes on Crooked Creek (Clark and Foster, 1971). Arsenic was found in all stream-sediment samples collected from Crooked Creek by Clark and Foster (1971). No workable placers on Crooked Creek have been found above the mouth of Eldorado Creek, which heads against the same ridge as Lucky Gulch (see EA020). Mertie (1942) suggests that gold in Crooked Creek and Lucky Gulch is derived from the area between them. Placer gold has been produced on the Seventymile River (see EA025) near the mouth of Crooked Creek. There are reports of mining on Crooked Creek for the most years from 1909 to 1940. A hydraulic plant was installed in 1916 (Brooks, 1918), and it was operating in 1921 (Brooks, 1923). In 1936, Crooked Creek had the only good-size hydraulic plant in the Seventymile River basin (Mertie, 1938). Mining in 1936 on Crooked Creek was taking place about 2 miles upstream from its mouth; earlier mining was located farther downstream (Mertie, 1938).
Workings: There are reports of mining on Crooked Creek for the most years from 1909 to 1940. A hydraulic plant was installed in 1916 (Brooks, 1918), and it was operating in 1921 (Brooks, 1923). In 1936, Crooked Creek had the only good-size hydraulic plant in the Seventymile River basin (Mertie, 1938). Mining in 1936 on Crooked Creek was taking place about 2 miles upstream from its mouth; earlier mining was located farther downstream (Mertie, 1938).
Age: Quaternary.
Production: Three assays of placer gold collected from Crooked Creek in 1934 and 1935 averaged 902 parts of gold and 92 parts of silver per thousand, the highest grade in the Seventymile area (Mertie, 1938). Mertie (1942) later reported 20 assays of placer gold from Crooked Creek that averaged 908 parts of gold and 88 parts of silver per thousand.
Commodities (Major) - Au; (Minor) - Ag, Pb
Development Status: Yes
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a).
References
Brooks, A.H., 1915, Mineral resources of Alaska; report on progress of investigations in 1914: U.S. Geological Survey Bulletin 622, 380 p. Brooks, A.H., 1918, Mineral resources of Alaska, 1916: U.S. Geological Survey Bulletin 662, 469 p. Brooks, A.H., 1923, The Alaska mining industry in 1921: U.S. Geological Survey Bulletin 739-A, p. 1-50. Brooks, A.H., and Capps, S.R., 1924, The Alaska mining industry in 1922: U.S. Geological Survey Bulletin 755-A, p. 1-56. Burleigh, R.E., and Lear, K.G., 1994, Compilation of data for Phase I of the mineral resource evaluation of the Bureau of Land Management Black River and Fortymile subunits: U.S. Bureau of Mines Open-File Report 48-94, 116 p. Clark, S.H.B., and Foster, H.L., 1971, Geochemical and geological reconnaissance in the Seventymile River area, Alaska: U.S. Geological Survey Bulletin 1315, 21 p. Cobb, E.H., 1972, Metallic mineral resources map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-393, 1:250,000 scale, 1 sheet. Cobb, E.H., 1977, Summary of references to mineral occurrences in the Eagle quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-845, 122 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. Ellsworth, C.E., 1910, Placer mining in the Yukon-Tanana region: U.S. Geological Survey Bulletin 442-F, p. 230-245. Ellsworth, C.E., and Davenport, R.W., 1913, Placer mining in the Yukon-Tanana region: U.S. Geological Survey Bulletin 542-F, p. 203-222. Ellsworth, C.E., and Parker, G.L., 1911, Placer mining in the Yukon-Tanana region: U.S. Geological Survey Bulletin 480-F, p. 173-217. Foster, H.L., 1976, Geologic map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series, Map 922, 1 sheet, scale 1:250,000. Mertie, J.B., Jr., 1930, Geology of the Eagle-Circle district, Alaska: U.S. Geological Survey Bulletin 816, 168 p. Mertie, J.B., Jr., 1938, Gold placers of the Fortymile, Eagle, and Circle districts, Alaska: U.S. Geological Survey Bulletin 897-C, p. 133-261. Mertie, J.B., Jr., 1942, Tertiary deposits of the Eagle-Circle district, Alaska: U.S. Geological Survey Bulletin 917-D, p. 213-264. Porter, E.A., 1912, Placer mining in the Fortymile, Eagle, and Seventymile River districts: U.S. Geological Survey Bulletin 520-G, p. 211-218. Powers, J.B., 1935, Brief history of the Fortymile and Eagle Mining Districts to 1935: Alaska Territorial Department of Mines Mineral Report MR 60-2, 19 p. Smith, P.S., 1926, Mineral industry of Alaska in 1924: U.S. Geological Survey Bulletin 783-A, p. 1-30. Smith, P.S., 1929, Mineral industry of Alaska in 1926: U.S. Geological Survey Bulletin 797, p. 1-50. Smith, P.S., 1930, Mineral industry of Alaska in 1928: U.S. Geological Survey Bulletin 813-A, p. 1-72. Smith, P.S., 1932, Mineral industry of Alaska in 1929, in Smith, P.S., and others Mineral resources of Alaska, report on progress of investigations in 1929: U.S. Geological Survey Bulletin 824-A, p. 1-81. Smith, P.S., 1933, Mineral industry of Alaska in 1930: U.S. Geological Survey Bulletin 836-A, p. 1-83. Smith, P.S., 1933, Mineral industry of Alaska in 1931: U.S. Geological Survey Bulletin 844-A, p. 1-81. Smith, P.S., 1936, Mineral industry of Alaska in 1934: U.S. Geological Survey Bulletin 868-A, p. 1-91. Smith, P.S., 1937, Mineral industry of Alaska in 1935: U.S. Geological Survey Bulletin 880-A, p. 1-95. Smith, P.S., 1938, Mineral industry of Alaska in 1936: U.S. Geological Survey Bulletin 897-A, p. 1-107. Smith, P.S., 1939, Mineral industry of Alaska in 1937: U.S. Geological Survey Bulletin 910-A, p. 1-113. Smith, P.S., 1939, Mineral industry of Alaska in 1938: U.S. Geological Survey Bulletin 917-A, p. 1-113. Smith, P.S., 1942, Mineral industry of Alaska in 1940: U.S. Geological Survey Bulletin 933-A, p. 1-102.
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