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Smith Creek Mine, Fortymile District, Southeast Fairbanks Borough, Alaska, USA

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Latitude & Longitude (WGS84): 64° 15' 13'' North , 141° 4' 44'' West
Latitude & Longitude (decimal): 64.2536111111, -141.078888889


Location: Smith Creek is a 12-mile-long south tributary of the lower Fortymile River, located about 3 miles west of the Canadian border and about 2 miles south of the Eldon landing strip. Pay was found for at least 2 miles along Smith Creek. The coordinates are placed about 1 mile upstream of the mouth of the creek, in section 6, T. 8 S., R. 34 E., of the Fairbanks Meridian. The location is accurate within 1 mile. Smith Creek is locality 54 of Eberlein and others (1977).
Geology: The rocks along most of Smith Creek are Paleozoic gneiss, schist, amphibolite, quartzite, and marble (Foster, 1969 [B 1271-G]). Dioritic to granodioritic gneiss and graphitic quartzite and quartz-muscovite schist of the Nasina Series of Devonian to Mississippian age crop out at the head of Smith Creek (Mortensen, 1988; Mortensen, 1999). Extensive terrace gravel deposits occur on both sides of the lower portion of the Fortymile River (see EA071), including in the Smith Creek valley. Gold-bearing gravels were found for at least 2 miles along Smith Creek and its benches, but the creek was not regarded as rich (Powers, 1935). Mining occurred on Smith Creek in 1932 (Smith, 1934 [B 857-A]), and two men were working on Smith Creek in the mid-1930's (Powers, 1935). There was prospecting on Smith Creek in 2000 (R.L. Flynn, unpub. data, 2000). Placer gold has also been produced on the lower Fortymile River near the mouth of Smith Creek.
Workings: Gold-bearing gravels were found for at least 2 miles along Smith Creek and its benches, but the creek was not regarded as rich (Powers, 1935). Mining occurred on Smith Creek in 1932 (Smith, 1934 [B 857-A]), and two men were working on Smith Creek in the mid-1930's (Powers, 1935). There was prospecting on Smith Creek in 2000 (R.L. Flynn, unpub. data, 2000). Placer gold has also been produced on the lower Fortymile River (see EA071) near the mouth of Smith Creek.
Age: Quaternary.

Commodities (Major) - Au
Development Status: Yes; small
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a).

Mineral List


1 valid mineral.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Devonian
358.9 - 419.2 Ma
Biotite gneiss, marble, schist, quartzite, and amphibolite

Age: Devonian (358.9 - 419.2 Ma)

Description: Mixed unit characterized by abundant aluminous metasedimentary rocks. Small-scale isoclinal folds are locally visible, suggesting that the entire unit is isoclinally folded. Primarily interlayered, medium- to coarse-grained, schist (commonly crenulated and folded) and paragneiss, with minor local biotite quartzite, marble, and fine-grained plagioclase-rich (metavolcanic?) gneiss. The schist contains a minimum of 30 percent mica and typically contains 110 percent rotated, poikiloblastic garnet, 1015 percent biotite, 1575 percent muscovite, 220 percent plagioclase, 2050 percent quartz, and 05 percent K-feldspar. Garnets are commonly 15 mm, other minerals typically 12 mm in size. Kyanite (0.20.5 mm, to 5 percent), staurolite (0.31 mm, to 5 percent), and tourmaline (0.1 mm, to 1 percent) are variably present, especially in the northwestern part of the Eagle A-1 Quadrangle. Staurolite, kyanite, and tourmaline are more abundant than shown on the geologic map, as they are virtually never identifiable in hand specimen. The common occurrence of staurolite with kyanite and tourmaline suggests that their occurrence is caused by aluminumboron-rich bulk composition and not variations in metamorphic grade within the Fortymile River Assemblage. The paragneiss contains less than 30 percent micas and typically 4060 percent quartz, 520 percent biotite, 120 percent muscovite, 1025 percent plagioclase and 02 percent garnet, all with average grain sizes of 0.51 mm. The plagioclase-rich gneiss contains mineral abundances similar to that of the tonalite gneiss (Motn), but grain sizes of 0.20.5 mm suggest it may represent local (andesitic?) metavolcanic layers within a largely metasedimentary sequence. Magnetic susceptibilities for rocks of this unit are highly variable, with values between 0 and 20 x 10-3 SI, although low values (< 0.3 x 10-3 SI) are more common

Lithology: Metamorphic

Reference: Wilson, F.H., Hults, C.P., Mull, C.G, and Karl, S.M. (compilers). Geologic map of Alaska. doi: 10.3133/sim3340. U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196. [21]

Devonian - Cambrian
358.9 - 541 Ma
Sedimentary; Clastic: shallow marine

Age: Paleozoic (358.9 - 541 Ma)

Description: Eastern Alaska, Yukon, Mackenzie region, Yukon-Tanana upland

Comments: Orogen, magmatic arc/suite; Wilson & Hults, unpublished compilation, 2007-08

Lithology: Sandstone, siltstone, shale; marine fossils; metamorphosed equivalent

Reference: J.C. Harrison, M.R. St-Onge, O.V. Petrov, S.I. Strelnikov, B.G. Lopatin, F.H. Wilson, S. Tella, D. Paul, T. Lynds, S.P. Shokalsky, C.K. Hults, S. Bergman, H.F. Jepsen, and A. Solli. Geological map of the Arctic. doi:10.4095/287868. Geological Survey of Canada Map 2159A. [2]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License



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References

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. Foster, H.L., 1969, Reconnaissance geology of the Eagle A-1 and A-2 quadrangles, Alaska: U.S. Geological Survey Bulletin 1271-G, p. G1-G30. Foster, H.L., and Keith, T.C., 1968, Preliminary geologic map of the Eagle B-1 and C-1 quadrangles: U.S. Geological Survey Open-File Report 68-103, 1 sheet, scale 1:63,360. Mortensen, J. K., compiler, 1988, Geology, southwestern Dawson map area, Yukon Territory (NTS 116B, C): Geological Survey of Canada Open File 1927, 1 sheet, scale 1:250 000. Mortensen, J.K. (compiler), 1999, Yukonage--An isotopic age database for the Yukon Territory, in Gordey, S.P., and Makepeace, A.J., compilers, Yukon Digital Geology: Indian and Northern Affairs Canada, Exploration and Geological Services Division, Yukon Region. 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., 1934, Mineral industry of Alaska in 1932: U.S. Geological Survey Bulletin 857-A, p. 1-91.

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