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Unnamed (west of Clearwater Creek)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals azurite; chalcocite; chrysocolla; malachite; native copper
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.1355
Longitude -146.998
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 4,500 feet about 1.6 miles south-southwest of the junction of Clearwater and Pass Creeks, in the NW1/4SW1/4 section 33, T. 20 S., R. 4 E., Fairbanks Meridian. The occurrence corresponds to locality A41 of Kurtak and others (1992), to locality 2 in figure 4 of Cobb (1979 [OFR 79-238]), and to locality 41 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

Bedrock in the area consists of Nikolai Greenstone of Late Triassic age that is locally sheared and silicified and cut by quartz veinlets (Nokleberg and others, 1991; Kurtak and others, 1992, table A41).
The deposits consist of copper minerals, including chalcocite, chrysocolla, native copper, azurite, and malachite, in quartz veins, in vesicles, and on joint and fracture surfaces of propylitized and locally silicified basalt (Smith and others, 1973; Kurtak and others, 1992). Copper content of three samples of basalt with visible copper minerals assayed from 2.52 to 4.9 percent copper and 1.2 to 5.2 parts per million silver; gold was not reported (Kurtak and others, 1992).
Geologic map unit (-147.000260275642, 63.1350557484748)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization The copper deposits are probably either Cretaceous or early Tertiary in age (see see MH060 and MH100).
Alteration of deposit Basalt is propylitized and locally silicified.

Production and reserves

Workings or exploration Several zones stained by copper oxides were sampled by the U.S. Bureau of Mines (Kurtak and others, 1992, table A41). Samples contained as much as 4.9 percent copper; a placer sample collected one mile south of the occurrence contained no gold.
Indication of production None

Additional comments

Copper values are locally very high, but the occurrences are small and there is a low potential for copper (Kurtak and others, 1992).

References

References

Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount Hayes quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-238, 140 p.
Kurtak, J.M., Southworth, D.D., Balen, M.D., and Clautice, K.H., 1991, Mineral investigations in the Valdez Creek Mining District, south-central Alaska: U.S. Bureau of Mines Open-File Report 1-92, 658 p., 2 sheets, scale 1:250,000.
Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000.
Smith, T.E., Trible, T.C., and Stein, D.R., 1973, Analyses of rock and stream-sediment samples, Mt. Hayes A-6 quadrangle, south-central Alaska: Alaska Division of Geological and Geophysical Surveys Geochemical Report 26, 1 plate, scale 1:63,360.
Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 8/5/2001