Eldorado Creek (tributary of Colorado Creek)

Mine, Active

Commodities and mineralogy

Main commodities Au
Ore minerals gold; magnetite
Gangue minerals garnet; quartz

Geographic location

Quadrangle map, 1:250,000-scale OP
Quadrangle map, 1:63,360-scale C-1
Latitude 63.5479
Longitude -156.0106
Nearby scientific data Find additional scientific data near this location
Location and accuracy Eldorado Creek is a short, generally north-flowing headwater tributary to Colorado Creek. Placer mining on Eldorado Creek was an extension of mining on Colorado Creek. Placer tailings begin at the mouth of Eldorado Creek and continue for nearly 1 mile upstream. The coordinates are for the approximate midpoint of the lower group of tailings, in the southern half of sec. 29, T. 22 S., R. 15 E., Kateel River Meridian. The location is accurate.

Geologic setting

Geologic description

The rocks in the vicinity of Eldorado Creek consist of intermediate to mafic volcanic and volcaniclastic rocks, and of Cretaceous Kuskokwim Group black shale, limestone, graywacke, and conglomerate intruded by Cripple Mountain monzonite (McGinnis, 1997; Avalon Development Corp., 1998; Duncan, 1999). The rocks adjacent to the monzonite are hornfelsed, with local development of garnet- and magnetite-bearing skarn in calcareous volcanic and sedimentary rocks (Avalon Development Corp., 1998; S. Dashevsky, oral communication, 2001).
Extensive placer mining was carried out along El Dorado Creek for about one mile upstream from its junction with Colorado Creek. Tailings in the upper part of Eldorado Creek do not follow the modern streambed and extend to the western walls of the stream drainage up to the flanks of Porphyry Knob (OP031) (S. Dashevsky, oral communication, 2001).
Placer mining on Eldorado Creek was conducted by the Strandberg family in the 1950s and by Mr. Nerod in the 1970s (McGinnis, 1997). Production figures for Eldorado Creek are not available (see OP002; and in the Medfra quadrangle, MD014, for Colorado Creek drainage production figures).
Also see OP002, 031, and 032; and in the Medfra quadrangle, MD014.
Geologic map unit (-156.012976502333, 63.5472889748298)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a) and Skarn (Cox and Singer, 1986; model 18d)
Mineral deposit model number 39a; 18d
Age of mineralization Placer deposits along nearby Colorado Creek area are middle Pleistocene, based on isotopic dates from overburden and geological inference (Bundtzen and others, 1987; Thorson and Guthrie, 1992). The skarn deposits are Cretaceous or younger.
Alteration of deposit Rocks adjacent to the monzonite are hornfelsed, with local development of garnet- and magnetite-bearing skarn in calcareous volcanic and sedimentary rocks (Avalon Development Corp., 1998; S. Dashevsky, 2001, oral communication).

Production and reserves

Workings or exploration
Prior to World War II, placer mining was conducted by William Critchley along the lower portion of Eldorado Creek, and William (Billy the Greek) Senatikis mined the upper portion (Ron Rosander, oral communication, 2001). The Strandberg family mined on Eldorado Creek in the 1950s and Mr. Nerod mined in the 1970s (McGinnis, 1997).
During 1994, 1995, and 1996, claimholder Ron Rosander contracted geologist James Barker to evaluate the lode sources of placer gold in the Colorado Creek area. Barker collected 254 soil samples, 93 rock samples, and 12 samples of placer gold for scanning-electron microscope and trace element analysis. Geologic mapping and a ground-based magnetometer survey were also carried out (Barker, 1996; McGinnis, 1997). In 1996, the Alaska Division of Geological and Geophysical Surveys conducted geologic mapping in the Cripple Creek Mountains and Placer Dome Exploration flew an east-west-oriented aeromagnetic survey over the Cripple Creek Mountains. Nova Gold conducted geologic mapping, rock sampling, and soil sampling during the summer of 1998 (Avalon Development, 1998). During 1999, Poseidon Minerals, Ltd. carried out soil sampling in the Colorado Creek area, and used mobile-metallic-ion (MMI) analyses (Duncan, 1999).
Indication of production Yes

Additional comments

For more information on Eldorado Creek, contact Ron Rosander in McGrath, AK.

References

MRDS Number 10308033

References

Avalon Development Corp., 1998, Colorado Creek project, Ophir and Medfra quadrangles, southwest Alaska: Avalon Development Corp. report prepared for NovaGold Resources Inc., 9 p.
Dashevsky, S.S., 2000, Colorado Creek project (Au) Innoko district, Alaska: Unpublished report for Rosander Mining Company, 7 p.
Duncan, R.G., 1999, Colorado Creek project, Alaska, interim report: Unpublished report for Poseidon Minerals Ltd., 22 p.
McGinnis, M.F., McCoy, M.E., Nerup, M.R., and Barnett, D., 1997, Colorado Creek project Alaska, 1997 summary report: Placer Dome Exploration Inc. unpublished report, 37 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.
Reporters C.E. Cameron
Last report date 8/7/2001