Moore Creek Mine, Iditarod Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Moore Creek Mine	Mine
Iditarod Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: The Moore Creek Mine is shown on the USGS 1:63,360-scale topographic map. The coordinates are at the center of the mine in the SW1/4, section 15, T. 29 N., R. 42 W., of the Seward Meridian. The location is accurate. The Moore Creek mine is locality 37 of Cobb (1972 [MF 363]); also described in Cobb (1976 [OFR 76-576]).
Geology: The Moore Creek Mine is a placer gold deposit that has worked several ages of ancestral terrace gravels as well as modern stream alluvium. The paystreak, as defined by exploration and mining, is about 2 miles long and 300 to 1,300 feet wide. The fluvial pay gravels, which are composed of rocks of local derivation range from 12 to 20 feet thick and are overlain by 5 to 7 feet of overburden. The principal heavy minerals identified in concentrates include native gold, cinnabar, scheelite, native silver, tetrahedrite, chromite, magnetite, and zircon (Mertie, 1936; Bundtzen and others, 1987, 1988; McGimsey and others, 1988). Concentrates from mining contain up to 35.00 percent chromite, i.e., a low grade chrome resource. A mineral separate of screened, minus-28-mesh material from a 100-kilogram, bulk sample of gravel contained 2,300 parts per million (ppm) chromium, 5,200 ppm titanium, 70 parts per billion (ppb) palladium, 200 ppm nickel, and 8.25 percent iron (Bundtzen, Laird, and Lockwood, 1988). The gold fineness averages about 758, which is low as compared to other deposits in the Innoko or Iditarod districts (Smith, 1941 [B 910]). Gold nuggets up to 19 ounces in in weight have been found in the deposit. The high chromium content of the placer concentrates is somewhat enigmatic as there are no known masses of ultramafic rock in the area. The source for the gold, silver, tungsten and mercury minerals is probably a mineralized monzonite intrusion and its contact zones about 1.2 mile to the northwest and upstream of the placer deposit (see Broken Shovel lode, ID081). The northeast-trending Iditarod-Nixon Fork fault forms the southern structural boundary of the Moore Creek pluton and Bundtzen, Laird, and Lockwood (1988) have postulated that the Late Tertiary to Pleistocene placer deposits at Moore Creek may have been successively offset right-laterally by transcurrent fault movement and the oldest placers occur southwest of the pluton. From 1911 to 1986, at least 53,990 ounces of gold and 12,520 ounces silver have been recovered from the Moore Creek placer deposit (Bundtzen and others, 1988; Miller, Bundtzen, and Gray, 2005). About 1,383 ounces of gold and 64 ounces of silver have been produced from nearby Nevada Gulch, mainly from 1911 to 1929.
Workings: Gold was discovered on Nevada Gulch, a short tributary of Moore Creek in 1910 (Maddren, 1911) and the Discovery claim on Moore Creek was staked in 1911 (Mertie, 1936). Shallow deposits were worked by opencut scraper and hand methods in the first 20 years of operation. In 1913, some ground was being prepared for a dredge; however, a dredge never operated on Moore Creek. In 1927, a Northwest dragline, one of the first in southwest Alaska (Smith, 1931) was brought into the district for exploration, development, and mining. By the 1930s, mechanized placer mines equipped with draglines and bulldozers dominated activities in the district. The dragline stacked tailings in regular, linear tailing piles up to 6 meters high down the valley of Moore Creek. In the mid-1930s, the USSR&M company initiated a churn drill program in Moore Creek basin with the idea of developing ground for a large-scale dredging operation (Smith, 1937). Large scale mechanized mining was nearly continuous until Statehood and then intermittent through 1986. Small scale exploration and development activities continued through 2001.
Age: Not dated; however, older terrace deposits are inferred to be Late Tertiary to early Pleistocene, based on similarities with other dated deposits in Interior Alaska (Hopkins and others, 1971). Pleistocene fossils (mammoth and horse bones) in the overburden were dated at 36,000 BP with radiocarbon methods (Jeff Kline written communication, 1986).
Production: From 1911 to 1986, at least 53,990 ounces of gold and 12,520 ounces of silver have been produced from the Moore Creek Mine (Bundtzen and others, 1988; Miller, Bundtzen, and Gray, 2005). About 1,383 ounces of gold and 64 ounces of silver have been produced from nearby Nevada Gulch, mainly from 1911 to 1929. Beginning in the early 1930s, Gus Uotila, Charlie Uotila, John Ogriz, and Elmer Keturi operated the first bulldozer-based placer mine and established Moore Creek Mining Company. More than 70 percent of the total historic production occurred from the mid 1930s to about 1955, when a highly successful dragline/bulldozer plant operated by Elmer Keturi and Jules Stuver mined the deposit. Annual production ranged from 2,000 to 6,500 ounces of placer gold throughout the 1930s and the 1950s (unpublished U.S. Mint records). From 1933 to 1937, the Moore Creek Mining Company was the largest producer of gold in the Iditarod District (Smith, 1936, 1936, 1941 [B 926-A]). The best year of production was 1937 when 6,500 ounces of placer gold was produced. Moore Creek Mining Company also found abundant cinnabar during mine operations (Joesting, 1942). Work in the 1980s concentrated on recovering coarse nuggets from tailing piles.
Reserves: Not determined. Early dragline operations did not have nugget collectors and coarse nuggets have been found in tailings in recent years.

Commodities (Major) - Au; (Minor) - Ag, Cr, Hg, Ti, W, Zr
Development Status: None
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).

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Link to USGS - Alaska:	ID084

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References