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Otter Creek Mines, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA

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Latitude & Longitude (WGS84): 62° 27' 5'' North , 157° 57' 54'' West
Latitude & Longitude (decimal): 62.45139,-157.96500


Location: Otter Creek has been mined for about 4 miles by several mining operations. The area that has been placered is up to 0.8 mile wide. The coordinates are at about the center of the area that has been mined; it is 0.3 mile west of the northeast corner of section 10, T. 27 N., R. 47 W., of the Seward Meridian. The location is accurate.
Geology: Otter Creek is the second largest producer of placer gold in the Iditarod district; the largest is Flat Creek (ID104), one of its tributaries (Bundtzen and others, 1992). The placers in Otter Creek has been mined for about 4 miles; the deposit averages about 0.5 mile wide and reaches a maximum width of about 0.8 mile at its lower end near Flat. The gold occurs in both ancestral terrace gravels and modern alluvial gravels. The auriferous gravels begin just upstream from the confluence of Granite and Otter Creeks and continue west to a point about 1 mile below the junction of Otter and Flat Creeks. Many workers, including Mertie (1936) and Bundtzen and others (1992), believe that most of the placer gold and associated heavy minerals in the fluvial gravels of Otter Creek are derived from: 1) gold lodes on Chicken Mountain, the gold being transported down Flat Creek (ID108 and ID109); 2) lodes in upper Otter Creek (ID106, ID110, and ID115); and 3) lodes in the Granite Creek area (ID116, ID118, ID121, and ID122). Some gold-bearing veins also occur in the bedrock below the auriferous gravel of Otter Creek; an example is the gold-bearing stibnite veins near the mouth of Glen Gulch (ID114). The gold from Otter Creek varies from 822 to 891 fine. The fineness decreases downstream, suggesting sources for the gold on Otter Creek (Bundtzen and others, 1992). In addition to gold, the principal heavy minerals include arsenopyrite, cinnabar, fluorapatite, scheelite, argentiferous Pb-Sb sulfosalts, monazite, cassiterite, magnetite, ilmenite, chromite, stibnite, and radioactive zircon (Mertie, 1936; White and Killeen, 1953; Cobb, 1976 [OFR 76-576]). Elevated PGEs also have been detected in heavy mineral concentrates (Bundtzen, Cox, and Veach, 1987). Gold on Otter Creek was discovered in upper Otter Creek on Christmas Day, 1908, by John Beaton and William Dikeman (Maddren 1910, 1911). A rush ensued in 1910 and within a year, there were large scraper plants and underground drift mines in operation on Otter Creek. Otter Creek was drilled by the Yukon Gold Company in 1913. Subsequently the composite placer deposit has been dredged and mined by backhoe and dragline and, in a few places, with drift mines (Mertie, 1936). Exploration and development on Otter Creek was almost continuous between 1910 to the early 1960s (Cobb, 1976 [OFR 76-576]). Mining was greatly affected by distribution of permafrost. The ground was thawed within 100 meters of the present channel of Otter Creek, probably due to the active thaw bulb of the active water channel. The rest of the Otter Creek valley was frozen and required thawing. Overburden was removed hydraulically. From 1914-1966, two bucketline dredging companies and predecessor companies mined Otter Creek: 1) the Riley Investment Company dredge; and 2) the North American Dredging Company dredge (Bundtzen and others, 1992). After 1958, the Riley Dredge could only mine thawed ground near Otter Creek as thaw field development had become too costly. From 1966 to 1990, mining on Otter creek consisted of remining tailings and fractions of unmined ground using bulldozer, dragline, and excavator equipment. Production from Otter Creek was 235,721 ounces of gold and 30,628 ounces of silver from 1910 to 1966 (Kimball, 1966). Another 354,210 ounces of gold was produced from Otter and Flat Creeks. Otter Creek is estimated to have produced a grand total of about 417,000 ounces of gold from 1910 to present (Bundtzen and others, 1992; Miller, Bundtzen, and Gray, 2005).
Workings: Gold was discovered in upper Otter Creek on Christmas Day, 1908, by John Beaton and William Dikeman (Maddren 1910, 1911). A rush ensued in 1910 and within a year, there were large scraper plants and underground drift mines in operation. Otter Creek was drilled by the Yukon Gold Company in 1913. Subsequently the placer deposit was dredged and mined by backhoe and dragline and, in a few places, with drift mines (Mertie, 1936). Peter Miscovich introduced bulldozer, backhoe mining on the creek in the 1930s. The backhoe could dig deeply into bedrock, and pay extended many feet into bedrock. Miscovich also developed the hydraulic lift or gravel elevator, which was used by other operators in the Iditarod district from the 1920s to the 1950s (Harold Stranberg, oral commun., 2001). Exploration and development on Otter Creek was almost continuous between 1910 to the early 1960s (Cobb, 1976 [OFR 76-576]). Mining was greatly affected by distribution of permafrost. Ground was thawed within 300 feet of Otter Creek, probably due to the active thaw bulb of the active water channel. The rest of the Otter Creek valley was frozen and required thawing. Overburden was removed hydraulically. From 1914 to 1966, two bucketline dredging companies and their predecessor companies mined Otter Creek: 1) the Riley Investment Company dredge; and 2) the North American Dredging Company dredge (Bundtzen and others, 1992). After 1958, the Riley Dredge could only mine thawed ground near Otter Creek thawing had become too expensive. From 1966 to 1990, mining on Otter creek consisted of remining tailings and fractions of unmined ground using bulldozer, dragline, and excavator equipment.
Age: Probably Tertiary and Quaternary by analogy with other placer deposits in Interior Alaska (Hopkins and others, 1971).
Production: Otter Creek has produced 235,721 ounces of gold and 30,628 ounces of silver from 1910 to 1966 (Kimball, 1966). An additional 354,210 ounces of gold was produced from a combination of Otter and Flat Creeks. Otter Creek is estimated to have produced a total of about 417,000 ounces of gold from 1910 to present (Bundtzen and others, 1992; Miller, Bundtzen, and Gray, 2005). The North American Dredging Company and Riley Investment Company dredges produced 291,972 ounces of gold from 1914 to 1966, or about 21.0 percent of the total for the Iditarod district and 70.0 percent of the total for Otter Creek. Small scale operations on Otter Creek have been dominated by Miscovich and Sons, Inc. and later by the Otter Creek Dredging Company (a John Miscovich family operation) that produced gold through 1992.
Reserves: Much of the paystreak on Otter Creek has been mined. However, according to John Miscovich and Richard Fullerton (oral communication, 1986), the lower end of the placer below the townsite of Flat, which has never been mined, contains about 100,000 ounces of gold in ground that averages about 0.1 ounce per cubic yard. This estimate was calculated from the results of a churn drilling program conducted in the 1940s and 1950s.

Commodities (Major) - Ag, Au; (Minor) - As, Cr, Hg, Sb, Sn, U, Zr
Development Status: Yes
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).

Mineral List


11 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: Symmetrical to irregular piles of artificially water-worked, sorted gravel and in situ slab rock derived from bedrock.

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]

Late Cretaceous
66 - 100.5 Ma
Sedimentary; Slope and deep water

Age: Late Cretaceous (66 - 100.5 Ma)

Description: Interior western Alaska, Southwest Basin

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

Lithology: Shale, chert, iron-formation, greywacke, turbidite, argillaceous limestone, matrix-supported conglomerate or 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

Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Process Mineralogy VII, The Metallurgical Society, p. 221-246. Bundtzen, T.K., Miller, M.L., Laird, G.M., and Bull, K.F., 1992, Geology and mineral resources of Iditarod mining district, Iditarod B-4 and eastern B-5 quadrangles, southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 97, 46 p., 2 sheets, scale 1:63,360. Cobb, E.H., 1972, Metallic mineral resources map of the Iditarod quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-363, 1 sheet, scale 1:250,000. Cobb, E.H., 1974, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 pages. 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. Hopkins, D.M., Matthews, J.V., Wolfe, J.A., and Silberman, M.L., 1971, A Pliocene flora and insect fauna from the Bering Sea region: Paleoecology, vol. 9, p. 211-231. Kimball, A.L., 1969, Reconnaissance sampling of decomposed monzonite for gold near Flat, Alaska: U.S. Bureau of Mines Open File Report 6-69, 39 p. 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. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet. White, M.G., and Killeen, P.L., 1953, Reconnaissance for radioactive deposits in the lower Yukon-Kuskokwim highlands region, Alaska, 1947: U.S. Geological Survey Circular 255, 18 p.

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