|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||This old placer mine on Ruby Gulch which flows into Crooked Creek; the mouth of Ruby Gulch is about 800 feet upstream from the mouth of Queen Gulch (ID164). The placer deposit in Ruby Gulch is at an elevation of about 400 feet, about 0.3 mile southwest of the center of section 23, T. 23 N., R. 49 W., Seward Meridian. The location is accurate. Ruby Gulch is locality 19 of Cobb (1972 [MF 363]); also described in Cobb (1976 [OFR 76-576]).|
Geologic descriptionThe Ruby Gulch placer deposit is in a small stream that flows across the lower slopes of the ridge separating Snow Gulch (ID166) and Queen Gulch (ID164). The placer formed where Ruby Gulch intersects the ancestral 'Donlin Creek' alluvial terrace. 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 Ruby Gulch, low grade auriferous gravel deposits in the ancestral channel were reworked to form locally rich gold placers. The placer in Ruby Gulch is about 1,600 feet long; the gold-bearing gravel varies from about 16 to 50 feet thick. In addition to gold, the principal heavy minerals identified in concentrates include gold-bearing arsenopyrite, cinnabar, cassiterite, arsenian-pyrite, scheelite, stibnite, and magnetite (Bundtzen, Cox, and Veach, 1987). Seven samples of gold from Ruby Gulch varied from 902 to 910 fine (Smith, 1941 [B 910]; Cobb, 1972 (MF 363); Cobb, 1976 [OFR 76-576]). The placer gold in Ruby Gulch probably originated in the Donlin Creek lode deposit which is just southeast of Ruby Gulch (ID167) (Miller and Bundtzen, 1994; Bundtzen and Miller, 1997). Unpublished mint records indicate that Ruby Gulch produced about 145 ounces of gold in 1911.
|Geologic map unit||(-158.216980726379, 62.0662771252496)|
|Mineral deposit model||Placer Au deposit (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||The alluvium in modern Ruby Gulch is probably Quaternary; the ancestral terrace is probably Late Tertiary.|
|Workings or exploration||The Ruby Gulch placer deposit was discovered in 1910 and was mined by open-cut methods (Maddren, 1911, 1915; Brooks, 1912; Cobb, 1974). The only production that is recorded was in 1911.|
|Indication of production||Yes; small|
|Production notes||Unpublished mint records indicate that Ruby Gulch produced 145 ounces of gold in 1911.|
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|