Latitude: 64°55'52"N
Longitude: 141°43'26"W
Location: Broken Neck Creek is a small north tributary of the Seventymile River. Prindle (1905) reported that Broken Neck Creek was worked for about one-half mile upstream from the mouth. The coordinates are the approximate midpoint of this part of the creek, in section 7, T. 1 N., R. 30 E., of the Fairbanks Meridian. The location is accurate. Broken Neck Creek is locality 28 of Cobb (1972 [MF-393]), locality 7 of Eberlein and others (1977), and locality 10 of Burleigh and Lear (1994).
Geology: Broken Neck Creek flows through a narrow, steep-walled valley; the canyon walls are only 120 feet apart where the creek emerges onto the Seventymile River flats. Bedrock along the creek consists of Upper Cretaceous to Pliocene conglomerate interbedded with shale containing abundant fossil leaves (Prindle, 1905; Foster, 1976). Placer gold has been produced on the Seventymile River (see EA025) downstream from the mouth of Broken Neck Creek. In 1903, the placer workings at Broken Neck Creek were 100 feet wide, and extended about one-half mile upstream from the mouth (Prindle, 1905). The paystreak at this time was about 6 feet wide, and total production was about $10,000 (gold at $20.67 per ounce). Mining on Broken Neck Creek is sporadically reported from 1910 to 1940. Gravel worked in Broken Neck Creek was later reported to be 3 to 5 feet thick; the pay streak was 20 to 50 feet wide at the mouth of the canyon and much narrower upstream (Mertie, 1938). Work in the 1930's was confined to benches on the west side of the creek. Most of the gold on the benches was located close to and on bedrock; no coarse gold was recovered. An average of four assays of gold from the benches, collected in four separate years, was 829 parts of gold and 165 parts of silver per thousand (Mertie, 1938). Clark and Foster (1971) found anomalous lead and zinc were found in stream sediments from Broken Neck Creek.
Workings: In 1903, the placer workings at Broken Neck Creek were 100 feet wide and extended about one-half mile upstream from the mouth (Prindle, 1905). The paystreak at this time was about 6 feet wide. Mining on Broken Neck Creek is sporadically reported from 1910 to 1940. Gravel worked in Broken Neck Creek was later reported to be 3 to 5 feet thick; the pay streak was 20 to 50 feet wide at the mouth of the canyon and much narrower upstream (Mertie, 1938). Work in the 1930's was confined to benches on the west side of the creek.
Age: Quaternary.
Production: Total gold production from Broken Neck Creek as of 1903 was about $10,000 (gold at $20.67 per ounce) (Prindle, 1905). An average of four assays of gold from the benches, collected in four separate years, was 829 parts of gold and 165 parts of silver per thousand (Mertie, 1938).
Commodities (Major) - Au
Development Status: Yes; small
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a).
References
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., 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. 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. Prindle, L.M., 1905, The gold placers of the Fortymile, Birch Creek, and Fairbanks regions, Alaska: U.S. Geological Survey Bulletin 251, 89 p. Prindle, L.M., 1909, The Fortymile quadrangle, Yukon-Tanana region, Alaska: U.S. Geological Survey Bulletin 375, 52 p. 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., 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., 1942, Mineral industry of Alaska in 1940: U.S. Geological Survey Bulletin 933-A, p. 1-102.
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