Otter Creek

Mines, Active

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Cr; Hg; Sb; Sn; U; Zr
Ore minerals arsenopyrite; cassiterite; chromite; cinnabar; gold; ilmenite; lead-antimony sulfosalts; magnetite; scheelite; stibnite
Gangue minerals fluorapatite; monazite; zircon

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale B-4
Latitude 62.45141
Longitude -157.96482
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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.

Geologic setting

Geologic description

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).
Geologic map unit (-157.967222810517, 62.4507256957929)
Mineral deposit model Placer Au deposit (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Probably Tertiary and Quaternary by analogy with other placer deposits in Interior Alaska (Hopkins and others, 1971).

Production and reserves

Workings or exploration
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 communication, 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.
Indication of production Yes
Reserve estimates 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.
Production notes
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.

References

MRDS Number A015072; A015073; D002701

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.
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.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date 5/21/2003