|Quadrangle map, 1:250,000-scale||ID|
|Quadrangle map, 1:63,360-scale||A-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Snow Gulch is a 4-mile-long, northwest-flowing tributary of Donlin Creek. About 1.2 mile of lower Snow Gulch has been mined or is known to be gold-bearing. The coordinates are near its mouth where the richest placers are found. This location is at an elevation of about 500 feet, about 0.7 mile southeast of the center of section 14, T. 23 N., R. 49 W., of the Seward Meridian. The location is accurate. The Snow Gulch placer mine is locality 20 of Cobb (1972 [MF 363]); also described in Cobb (1976 [OFR 76-576]).|
Snow Gulch has been the principal placer-gold producer in the Donlin Creek district. The richest segment of the creek is about 0.5 mile long, just above the mouth of the creek; however, about 1.2 mile of the creek has good gold prospects (Maddren, 1915). The most productive zone along the creek was at the intersection of Snow Gulch and the ancestral 'Donlin Creek' terrace or bench deposit. According to Cady and others (1955) and Bundtzen and Miller (1997), Donlin Creek originally flowed northeast into the Iditarod River. After regional tilting, the drainage reversed direction and Donlin and Crooked Creeks flowed into the Kuskokwim River. In Snow Gulch, low grade auriferous gravel deposits in the ancestral channel were reworked to form locally rich gold placers. The pay streaks in Snow Gulch also extend for about 2,000 feet to both the northeast and southwest along the the Donlin terrace deposits. As pointed out by Maddren (1915), this productive section of the creek also the beginning of the abundant igneous intrusions upstream in the valley of the gulch.
The gravel in Snow Gulch varies from 16 to 50 feet thick. The gold is distributed irregularly on the bedrock at the base of the terrace. The pay zones locally contain between 0.12 to 0.2 ounces of gold per cubic yard (Spencer Lyman, oral communication, 1984). In addition to gold, the principal heavy minerals identified in the placer concentrates are auriferous arsenopyrite, arsenian pyrite, garnet, cassiterite, calcite, scheelite, stibnite, magnetite, and monazite. The concentrates are radioactive; the radioactivity is probably caused by U and Th and their daughter products in monazite (Bundtzen, Cox, and Veach, 1987). Garnet is abundant; it is likely derived from the swarm of granitic dikes and sills in the area. The gold varies from 802 to 930 fine and averages 927 fine; silver and mercury are the major trace metals in the gold (Smith, 1941 [B910]; Bundtzen, Cox, and Veach, 1987; T.K. Bundtzen, unpublished laboratory data, 1994). In 1983, a 9.8 ounce gold nugget was recovered from Snow Gulch (Spencer Lyman, oral communication, 1984).Unpublished mint records and more recent production estimates indicate that Snow Gulch has produced 8,238 ounces of gold and 605 ounces of silver from 1910 to 1992. Much of the gold was produced from 1983 to 1992 by Lyman Resources of Alaska, Inc. Some addition production may be included with the production from Donlin Creek and Crooked Creek.
|Geologic map unit||(-158.198360736345, 62.0758575548885)|
|Mineral deposit model||Placer Au deposit (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||The alluvium in modern Snow Gulch is probably Quaternary; the ancestral terrace is probably Late Tertiary.|
|Workings or exploration||Gold was found on Snow Gulch in 1909 and economic placers were found in 1910 (Brooks, 1912; Maddren, 1915). The deposit was mined mainly by open-cut methods (Cobb, 1974). The largest post World War II production began in 1983 when Lyman Resources of Alaska, Inc. began open-cut mining with bulldozer and dragline; they produced substantial amounts of gold intermittently through 1992.|
|Indication of production||Yes|
|Production notes||Unpublished mint records and more recent production estimates indicate that Snow Gulch has produced 8,238 ounces of gold and 605 ounces of silver from 1910 to 1992. Production was more-or-less continuous on a small scale through World War II. Some addition production may be included with the production from Donlin Creek and Crooked Creek. Lyman Resources of Alaska, Inc. accounted for a considerable percentage of the total production from Snow Gulch as a result of their mining from 1983 to 1992.|
|MRDS Number||A015045; A015064|
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.
Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
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.
Cady, W.M., Wallace, R.E., Hoare, J.M., and Webber, E.J., 1955, The central Kuskokwim region, Alaska: U.S. Geological Survey Professional Paper 268, 132 p.
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., 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.
Maddren, A.G., 1911, Gold placer mining developments in the Innoko-Iditarod region: U.S. Geological Survey Bulletin 480-I, p. 236-270.
Maddren, A.G., 1915, Gold placers of the lower Kuskokwim, with a note on copper in the Russian Mountains: U.S. Geological Survey Bulletin 622-H, p. 292-360.
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.
|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||5/26/2003|