Sheep Creek

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals azurite; bornite; chalcopyrite; cuprite; malachite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale WI
Quadrangle map, 1:63,360-scale C-4
Latitude 67.5624
Longitude -151.9818
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 3,600 feet, about 1,00 feet northeast of the top of hill 3914, near the southeast corner of section 27, T. 32 N., R. 20 W., of the Fairbanks Meridian. The occurrence is near the midpoint of a mile-long, east-northeast belt defined by the locations of several mineralized samples (Degenhart and others, 1978). It also corresponds to the location of mineralization described by Brosge and Reiser (1960) and by Cobb (1972, MF 469, loc. 7). The location is accurate within one-half mile.

Geologic setting

Geologic description

This occurrence is one of several that define a northeast trending zone of minor copper occurrences that extends for about 5 miles to the northeast from VABM Allen on the Wiseman C-5 topographic map (see also WI005, 006, and 012-014). Mineralization at this site was first described by Brosge and Reiser (1960; Cobb, 1972, locality 7 [MF 469] ), as conglomerate containing unspecified copper sulfides and malachite staining. Degenhart and others (1978) cite minor chalcopyrite, malachite, and azurite in a 5-foot-thick layer of quartz-chlorite schist. The schist underlies Middle Devonian, Skajit Limestone, which in this area is thrust over Upper Devonian shale, phyllite and schist. Degenhart and others (1978) suggested that the quartz-chlorite schist may represent the plane of a thrust fault . A select sample of mineralized talus material, collected about 0.2 mile east of the Brosge and Reiser location, contains 1,920 ppm copper and 4.2 ppm silver but no significant gold, lead, zinc, or molybdenum (Degenhart and others, 1978, sample BM1197). They interpret the mineralization as stratabound although its extent appears to be no more than 20 feet along strike and 5 feet in thickness.
Dillon and others (1981; sample 304 [AOF 133B]) collected a composite rock sample about 0.5 mile west of the Brosge and Reiser's site. It consists of graphitic, chlorite-sericite-quartz schist and vein quartz with disseminated cuprite(?) and malachite; it contains 5,000 ppm copper.
Kurtak and others (1999) found podiform copper mineralization in schist and marble in upper Sheep Creek that could be traced along strike for about 1,700 feet. They also observed chalcopyrite and bornite in quartz veins and in fracture fillings along a marble-schist contact. The orientation of these mineralized veins and fractures is parallel to the bedding of the overlying marble. They collected seven rock samples of float and outcrop, one of which contains an estimated 20% chalcopyrite. The samples contain 872 ppm to 16.53% copper, less than 5 to 46 ppb gold, and 0.3 to 78.6 ppm silver.
Geologic map unit (-151.984556756913, 67.5619441342214)
Mineral deposit model Polymetallic replacement deposit? (Cox and Singer, 1986; model 19a?).
Mineral deposit model number 19a?
Alteration of deposit Local oxidation of copper minerals.

Production and reserves

Workings or exploration Only surface sampling.
Indication of production None
Reserve estimates Degenhart and others (1978) noted that a few tons of mineralized material with about 0.5% Cu may be present.

Additional comments

See also WI014. This occurrence is located within Gates of the Arctic National Park.

References

MRDS Number A011987

References

Reporters J.M. Britton (Anchorage)
Last report date 8/9/2002