Colorado Creek Mines, Innoko District, Yukon-Koyukuk Borough, Alaska, USA
|Latitude & Longitude (WGS84):||63° 34' 20'' North , 156° 0' 28'' West|
|Latitude & Longitude (decimal):||63.5722222222, -156.007777778|
For more information on Colorado Creek, contact the current claim owner, Ron Rosander, in McGrath, AK.
Location: 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.
Geology: 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 paystreak extends along Colorado Creek from the Cripple Creek Mountains. This paystreak 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.
Workings: 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 commun., 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.
Age: 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).
Production: A conservative estimate of production from Colorado Creek is 110,000 ounces of gold (Bundtzen, 1999).
Commodities (Major) - Au; (Minor) - Ag
Development Status: Yes; medium
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a)
8 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
0 - 2.588 Ma
|Unconsolidated surficial deposits, undivided|
Age: Pleistocene (0 - 2.588 Ma)
Description: Gravel, sand, silt, and peat. Floodplain deposits in Koyukuk Flats and along Yukon River composed mainly of light gray micaceous silt. Deposits occur along floodplains of major drainages and on tidal flats bordering the shores of Selawik Lake, Hotham Inlet, Eschscholtz Bay, Norton Sound, and Norton Bay. Floodplain deposits characterized physiographically by bars, oxbow lakes, meander scrolls, abandoned channels, and other evidence of recent floodplain building
Reference: Wilson, F.H., Hults, C.P., Mull, C.G, and Karl, S.M. (compilers). Geologic map of Alaska. doi: 10.3133/sim3340. U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196. 
100.5 - 145 Ma
|Sedimentary; Clastic: shallow marine|
Age: Early Cretaceous (100.5 - 145 Ma)
Description: Interior western Alaska, Yukon-Koyukuk Basin
Comments: Sedimentary basin; Wilson & Hults, unpublished compilation, 2007-08
Reference: J.C. Harrison, M.R. St-Onge, O.V. Petrov, S.I. Strelnikov, B.G. Lopatin, F.H. Wilson, S. Tella, D. Paul, T. Lynds, S.P. Shokalsky, C.K. Hults, S. Bergman, H.F. Jepsen, and A. Solli. Geological map of the Arctic. doi:10.4095/287868. Geological Survey of Canada Map 2159A.