Eldorado Basin

The Eldorado Basin is a gold mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Eldorado Basin
Secondary: Moose Jaw Mountain

Commodity

Primary: Gold
Secondary: Antimony
Secondary: Copper

Location

State: Alaska
District: Innoko

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Epithermal vein, Creede
Model Name: Epithermal vein, Comstock

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: The headwater regions of Eldorado Creek contain limonite-stained, gossanous breccia (Avalon Development Corp., 1998).

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Stibnite
Ore: Chalcopyrite
Ore: Arsenopyrite
Gangue: Quartz
Gangue: Epidote
Gangue: Actinolite

Comments

Comment (Reference): Primary Reference = Duncan, 1999

Comment (Workings): Workings / Exploration = 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 collecteed 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).

Comment (Deposit): Model Name = Epithermal Au? (Cox and Singer, 1986; model 25b, 25c?)

Comment (Deposit): Model Number = 25b, 25c?

Comment (Deposit): Other Comments = For more information, contact Ron Rosander, in McGrath, AK.

Comment (Geology): Age = the igneous rocks inferred to be responsible for this deposit intrude Cretaceous strata of the Kuskowkwim Group.

Comment (Exploration): Status = Active

Comment (Geology): 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 headwaters of Eldorado Creek contain limonite-stained, gossanous breccia (Avalon Development Corp., 1998). The Eldorado Basin prospect is on a mineralized zone that trends northeast across the headwaters of the Eldorado Creek for 2200 meters. This zone extends northeast into the Medfra quadrangle and terminates at Colorado Creek, northeast of the summit of Moose Jaw Mountain. At the Eldorado Basin prospect, the zone contains scattered, thin veins of quartz and stibnite, of arsenopyrite and quartz, and locally of actinolite, chalcopyrite, or epidote. Soil samples collected from the Eldorado Basin contain up to 674 ppm copper, 2250 ppb gold, 2818 ppm arsenic, 945 ppm antimony, and 12 ppm bismuth (Avalon Development Corp., 1998). The northeast extension of this zone is defined by soil samples on Moose Jaw Mountain. Two mineralized areas have been identified: a NW-SE-trending, 400-meter by 50-meter area; and an adjacent area 1400 meters long by 200 to 400 meters wide. The 1400-meter-long area is open to the south (Duncan, 1999). Soil samples from these areas contain up to 515 ppb gold, 2770 ppm arsenic, 2942 ppm antimony, and 9 ppm bismuth (Avalon Development, 1998). Hypabyssal, porphyryritic rock at the top of Moose Jaw Mountain is cut by veins less than 5 centimeters thick of crystalline quartz, stibnite, arsenopyrite, and scorodite (Avalon Development, 1998). Exploration in the Eldorado Basin includes geologic mapping and sampling by Barker during 1994, 1995, and 1996; soil sampling, rock sampling, and geologic mapping by NovaGold during 1998; and mobile-metallic-ion (MMI) sampling by Poseidon Minerals Ltd. during 1999 (Barker, 1996; Avalon Development Corp., 1998; Duncan, 1999). Also see OP002 and OP031-033.

References

Reference (Deposit): Duncan, R.G., 1999, Colorado Creek project, Alaska, interim report: unpublished report for Poseidon Minerals Ltd., 22 p.

Reference (Deposit): Avalon Development Corp., 1998, Colorado Creek project, Ophir and Medfra quadrangles, southwest Alaska: report prepared for NovaGold Resources Inc., 9 p.

Reference (Deposit): McGinnis, M.F., McCoy, M.E., Nerup, M.R., and Barnett, D., 1997, Colorado Creek project Alaska, 1997 summary report: unpublished Placer Dome Exploration Inc. report, 37 p.

Reference (Deposit): Dashevsky, S.S., 2000, Colorado Creek project (Au) Innoko district, Alaska: unpublished report for Rosander Mining Company, 7 p.

Reference (Deposit): Barker, J.C., 1996, Geologic evaluation of the Colorado Creek prospect area, Alaska: Summary report prepared for Placer Dome Exploration, San Franscisco, California, 73 p.

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