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Unnamed (upper Specimen Creek)

Occurrence, Active

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Commodities and mineralogy

Main commodities Au; Cr
Other commodities Cu
Ore minerals chromite; malachite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3178
Longitude -146.06
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at an elevation of 4,400 feet in the headwaters of an unnamed west fork of Specimen Creek, in the NW1/4NE1/4 section 32, T. 18 S., R. 9 E., Fairbanks Meridian. The occurrence corresponds to localities 51 and 52 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

The rock at this occurrence consists of Upper Triassic olivine cumulate intruded by a metadiabase dike (Nokleberg and others, 1991). Rose (1965, figure 2) mapped a peridotite body in the headwaters of Specimen Gulch.
The olivine cumulate contains disseminated chromite; sample 79CH010B assayed more than 5,000 parts per million chromium (Nokleberg and others, 1991). Malachite occurs along fractures in the metadiabase dike; grab sample 79CH010C of dike material contained 150 parts per billion gold.
Geologic map unit (-146.062262919191, 63.3173803618724)
Mineral deposit model Disseminated chromite in ultramafic rocks; epigenetic? shear zone mineralization.
Age of mineralization The chromite is Late Triassic, the presumed age of the ultramafic host rock. The copper and gold are Late Triassic or younger.
Alteration of deposit Oxidation of copper mineral(s).

Production and reserves

Workings or exploration The occurrence is on active MAN Resources claims.
Indication of production None

References

References

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.
Rose, A.W., 1965, Geology and mineral deposits of the Rainy Creek area, Mt. Hayes quadrangle, Alaska: Alaska Division of Mines and Minerals Geologic Report 14, 57 p., 1 sheet, scale 1:36,000.
Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 6/19/2001