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Ophir Creek Mines, Innoko District, Yukon-Koyukuk Borough, Alaska, USA

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Latitude & Longitude (WGS84): 63° 7' 25'' North , 156° 31' 51'' West
Latitude & Longitude (decimal): 63.12361,-156.53083


Location: Ophir Creek has been mined for about 2 1/2 miles above its mouth, near the town of Ophir on the Innoko River. Mining also took place near its head. The coordinates are for the approximate midpoint of mine tailings marked on the U.S. Geological Survey Ophir A-2 topographic map (1954, minor revisions 1965). This point is on lower Ophir Creek, in sec. 26, T. 27 S., R. 12 E., Kateel River Meridian. Ophir Creek corresponds to localities 13 and 14 of Cobb (1972 [MF 367]). The location is accurate.
Geology: Bedrock in the vicinity of Ophir Creek consists of shale and siltstone (Chapman and others, 1985). The creek also drains small monzonite intrusive bodies, and igneous rock pebbles and cobbles are reported in the stream gravels (Mertie, 1936). Some vein quartz is also reported in the gravels (Mertie, 1936). Most of the gold on Ophir Creek is in crevices in the top 2 to 5 feet of bedrock (Maddren, 1910). The gold is coarse with many nuggets. It also occurs in bench and stream gravels (Maddren, 1910; Maddren, 1911). In 1933, one claim on Ophir Creek averaged $7 to 8 per square foot of bedrock. Nuggets as large as 14 ounces have been recovered (Mertie, 1936). The gold averages 898 fine (Smith, 1941). Heavy minerals in pan concentrates include magnetite, ilmenite, edenite, zircon, rutile, orthoferrosilite, and pyrite (Bundtzen and others, 1987). The likely source of the gold is nearby rhyolite dikes and monzonite plutons (Bundtzen and others, 1987). Gold was discovered on Ophir Creek in 1908, and mining occurred nearly continuously until 1940 (Cobb, 1976 [OFR 76-576]). In 1950, at least one person was mining along Ophir Creek (Williams, 1950). Mining is also reported during 1959, but the operator at that time planned to move to the Ruby district in 1960 (Saunders, 1960). More recent exploration or mining is probable but not documented. The estimated production from Ophir Creek from 1908 to1961 is 66,489 ounces of gold and 7,004 ounces of silver. Production figures for more recent mining from 1978 to 1985 are unknown (Bundtzen and others, 1987).
Workings: Gold was discovered on Ophir Creek in 1908, and mining occurred nearly continuously until 1940 (Cobb, 1976 [OFR 76-576]). By 1914, the creek was one of the chief gold-producing streams in the area, and 8 mines were operating (Eakin, 1914; Brooks, 1915). Drifting, draglines, and hydraulicking were all used to recover the gold. In 1950, at least one person was mining along Ophir Creek (Williams, 1950). Mining is also reported during 1959, but the operator at that time planned to move to the Ruby district in 1960 (Saunders, 1960). More recent exploration or mining is probable but not documented.
Age: Quaternary. The likely source of placer gold at Ophir Creek is nearby Cretaceous or Tertiary rhyolite dikes and monzonite plutons (Bundtzen and others, 1987).
Production: The estimated production from Ophir Creek from 1908 to1961 is 66,489 ounces of gold and 7,004 ounces of silver. Production figures for more recent mining from 1978 to 1985 are unknown (Bundtzen and others, 1987).

Commodities (Major) - Au; (Minor) - Ag
Development Status: Yes; medium
Deposit Model: Placer Au (stream and bench) (Cox and Singer, 1986; model 39a)

Mineral List


5 valid minerals.

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

Quaternary
0 - 2.588 Ma
Unconsolidated surficial deposits, undivided

Age: Pleistocene (0 - 2.588 Ma)

Description: Alluvium

Lithology: Unconsolidated

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]

Maastrichtian - Campanian
66 - 83.6 Ma
Sedimentary; Sedimentary: undivided

Age: Late Cretaceous (66 - 83.6 Ma)

Description: Interior western Alaska, Southwest Basin

Comments: Sedimentary basin; Wilson & Hults, unpublished compilation, 2007-08

Lithology: Sandstone, siltstone, shale, limestone

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

Brooks, A.H., 1910, Mineral resources of Alaska, report on progress of investigations in 1909: U.S. Geological Survey Bulletin 442, 426 p. Brooks, A.H., 1912, The mining industry in 1911, in Brooks, A.H., and others, Mineral resources of Alaska, report on progress of investigations in 1911: U.S. Geological Survey Bulletin 520-A, p. 17-44. Brooks, A.H., 1915, Mineral resources of Alaska; report on progress of investigations in 1914: U.S. Geological Survey Bulletin 622, 380 p. Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Alaska Division of Geological and Geophysical Surveys Public-Data File 87-16, 25 p. Chapman, R.M., Patton, W.W., and Moll, E.J., 1985, Reconnaissance geologic map of the Ophir quadrangle, Alaska: U.S. Geological Survey Open-File Report 85-203, 19 p., 1 sheet, scale 1:250,000. Cobb, E.H., 1972, Metallic mineral resources map of the Ophir quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-367, 1 sheet, scale 1:250,000. Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction material) in the Iditarod and Ophir quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-576, 101 p. Eakin, H.M., 1914, The Iditarod-Ruby region, Alaska: U.S. Geological Survey Bulletin 578, 45 p. Maddren, A.G., 1909, Gold placers of the Innoko district: U.S. Geological Survey Bulletin 379-E, p. 238-266. Maddren, A.G., 1910, The Innoko gold-placer district, Alaska, with accounts of the central Kuskokwim valley and the Ruby Creek and Gold Hill placers: U.S. Geological Survey Bulletin 410, 87 p. Maddren, A.G., 1911, Gold placer mining developments in the Innoko-Iditarod region: U.S. Geological Survey Bulletin 480-I, p. 236-270 Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. Saunders, R.H., 1960, Itinerary report on a trip to the Flat and Ophir Districts: Alaska Territorial Department of Mines Itinerary Report 64-2, 15 p. Williams, J.A., 1950, Mining operations in the Fairbanks district and Innoko and Koyukuk precincts: Alaska Territorial Department of Mines Miscellaneous Report 194-13, 20 p.

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