|Quadrangle map, 1:250,000-scale||OP|
|Quadrangle map, 1:63,360-scale||C-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Colorado Creek is a large, generally northwest-flowing tributary to Hunch Creek. Tailings are shown on the U.S. G. S. Ophir C-1 topographic map (1954) for approximately 2 miles along Colorado Creek; the coordinates correspond to the approximate midpoint of these tailings, which is in sec. 20, T. 22 S., R. 15 E., Kateel River Meridian. Colorado Creek also flows in the Medfra C-6 quadrangle; see also MD014. Colorado Creek is locality 9 of Cobb (1972 [MF 367]). This location is accurate.|
The rocks in the vicinity of Colorado Creek are Cretaceous sandstone and conglomerate of the Kuskokwim group and altered volcanic rocks (Bundtzen and others, 1987). The gravel in the creek consists primarily of granitic rocks and chert (Mertie, 1936). The gravel is about 8 feet thick and buried under 10-20 feet of muck (Eakin, 1914; Mertie, 1936).
A 6.5-mile-long pay streak extends along Colorado Creek from the Cripple Creek Mountains. This pay streak crosses into the Medfra C-6 quadrangle for approximately 2 miles and then returns to the Ophir quadrangle. Placer gold was recovered during large, non-float operations that also mined several feet of bedrock (Mertie, 1936; Cobb, 1973 [B 1374]). The fineness of the +10 mesh gold in Colorado Creek is 909.6, with 82.8 parts silver, and 2.57 parts impurities. The -8 to +14 mesh gold is 900.2 fine, with 91.8 parts Ag, and 8.15 parts impurities (Bundtzen and others, 1987). Heavy minerals found in concentrates from the Rosander Mining Co. placers include magnetite, ilmenite, coulsonite, anthophyllite, samarskite, powellite, and xanthoconite. An estimated 50% of the concentrate is magnetite; some platinum is reported in gold bullion (Bundtzen and others, 1987). Roehm (1937) reports the presence of scheelite and stibnite at Colorado Creek. The gold at Colorado Creek may be derived from Cretaceous or Tertiary meta-aluminous, alkali-calcic to quartz-alkalic monzonite plutons that are located nearby (Bundtzen and others, 1987), with local contributions from quartz-stibnite veins (see OP032), and mineralized fault zones and epithermal systems (see OP031).
Mining along Colorado Creek began in 1913 (Eakin, 1913) and continues to the present (2001) . Colorado Creek has consistently been one of the largest placer mines in the area and has been active nearly continuously with documentation of mining in 1913, 1915, 1924, 1930, 1935, 1937, 1939, 1940, 1950, and from 1979 to the present (Eakin, 1913; Mertie and Harrington, 1916; Smith, 1933; Smith, 1937; Roehm, 1937; Smith, 1941; Smith, 1942; Bundtzen and others, 1992). Both creek and bench placers of Colorado Creek have been mined (Cobb, 1973 [B 1374]). A conservative estimate of the total production for Colorado Creek is 110,000 ounces of gold and 4,644 ounces of silver (Bundtzen, 1999).Also see OP005 and OP031-033.
|Geologic map unit||(-156.010177816084, 63.5717893114233)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||The Colorado Creek placer deposit is middle Pleistocene, based on isotopic dates from overburden and geological inference (Bundtzen and others, 1987; Thorson and Guthrie, 1992). The source of the placer gold may be the Cretaceous or Tertiary meta-aluminous, alkali-calcic to quartz-alkalic monzonite plutons that are located nearby (Bundtzen and others, 1987).|
|Workings or exploration||Mining began in 1913 and continues to the present 2001). Colorado Creek has consistently been one of the largest placer mines in the district. Mining at Colorado Creek may be nearly continuous. Reports exist of mining in 1913, 1915, 1924, 1930, 1935, 1937, 1939, 1940, 1950, and from 1979 to the present (Eakin, 1913; Mertie and Harrington, 1916; Smith, 1933; Smith, 1937; Roehm, 1937; Smith, 1941; Smith, 1942; Bundtzen and others, 1992). Both creek and bench placers of Colorado Creek have been mined (Cobb, 1973 [B 1374]). The first mechanized mining along Colorado Creek was prior to World War II, when Sidney Paulson began mining with a dragline. The Fullerton brothers (Colorado Creek Mining Co.) mined Colorado Creek from about 1950 until about 1957 (Ron Rosander, oral communication, 2001). In 1983, a woolly mammoth skeleton was found at Colorado Creek; Rosander Mining Co. donated the skeleton to the University of Alaska Museum. Rosander Mining Co. has worked the ancestral channels of Colorado Creek's right bench since 1979 (Bundtzen and others, 1992). Additional exploration of the Colorado Creek area, including soil sampling, took place during the summer of 1998.|
|Indication of production||Yes; medium|
|Production notes||A conservative estimate of production from Colorado Creek is 110,000 ounces of gold (Bundtzen, 1999).|
Additional commentsFor more information on Colorado Creek, contact the current claim owner, Ron Rosander, in McGrath, AK.
|MRDS Number||A010750; A015007|
Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Alaska Division of Geological and Geophysical Surveys Public-Data File 87-16, 25 p.
Bundtzen, T.K., Swainbank, R.C., Wood, J.E., and Clough, A.H., 1992, Alaska's mineral industry 1991: Alaska Division of Geological and Geophysical Surveys Special Report SR 46, 89 p.
Cobb, E.H., 1972, Metallic mineral resources map of the Ophir quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-367, 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.
Eakin, H.M., 1913, Gold placers of the Innoko-Iditarod region: U.S. Geological Survey Bulletin 542-G, p. 293-303.
Mertie, J.B., Jr., and Harrington, G.L., 1916, Mineral resources of the Ruby-Kuskokwim region, in Brooks, A.H., and others, Mineral Resources of Alaska, Report on Progress of Investigations in 1915: U.S. Geological Survey Bulletin 642-H, p. 223-266.
Roehm, J.C., 1937, Summary report of mining investigations in the Innoko, Mt. McKinley, Knik, and Talkeetna precincts: Alaska Territorial Department of Mines Itinerary Report 195-17, 16 p.
Smith, P.S., 1933, Mineral industry of Alaska in 1930: U.S. Geological Survey Bulletin 836-A, p. 1-83.
Smith, P.S., 1937, Mineral industry of Alaska in 1935: U.S. Geological Survey Bulletin 880-A, p. 1-95.
Smith, P.S., 1941, Mineral industry of Alaska in 1939: U.S. Geological Survey Bulletin 926-A, p. 1-106.
Smith, P.S., 1942, Mineral industry of Alaska in 1940: U.S. Geological Survey Bulletin 933-A, p. 1-102.
Swainbank, R.C., Szumigala, D.J., Henning, M.W., and Pillifant, F.M., 2000, Alaska's mineral industry, 1999: Alaska Division of Geological and Geophysical Surveys Special Report 54, 73 p.
Thorson, R.M., and Guthrie, R.D., 1992, Stratigraphy of the Colorado Creek mammoth locality, Alaska: Quaternary Research, v. 37, no. 2, p. 214-228.
|Last report date||8/7/2001|