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Unnamed (in the canyon of Sheep Creek)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Fe
Ore minerals marcasite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale B-2
Latitude 62.413
Longitude -153.868
Nearby scientific data Find additional scientific data near this location
Location and accuracy This unnamed occurrence is located in a steep canyon of the west fork of Sheep Creek, on its east bank, at an elevation of 2,450 feet (746 m) in the SW1/4 sec. 23, T. 27 N., R. 25 W., of the Seward Meridian. The reporter visited the site in 1998 at station no. 98BT448.

Geologic setting

Geologic description

This occurrence is a highly sulfidized, alteration zone in a rhyodacite unit of the Paleocene to Eocene, Sheep Creek Volcanic Field (Bundtzen, Harris, and Gilbert, 1997). A very distinct, ferricrete gossan occurs in a cliff wall on the east side of Sheep Creek; the incompetent, mineralized walls have partially caved into the creek channel. The mineralization consists of disseminated to massive pyrite-quartz veins and stockworks up to 2 meters in width. Strike lengths were not determined. The mineralized area averages about 25 percent pyrite. Grab samples of massive pyrite-quartz veins contained an average 15.5 percent iron, 255 ppm copper, and 0.45 ppm silver (T.K. Bundtzen and G.M. Laird, written communication, 1998).
Geologic map unit (-153.870223454612, 62.4123883088346)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Mineralization is undated.
Alteration of deposit Strong silicification and sericite zones.

Production and reserves

Workings or exploration The reporter investigated the site in 1981. Grab samples that contained massive pyrite-quartz stockwork veins yielded an average 255 ppm copper, 15.5 percent iron, and 0.45 ppm silver (T.K. Bundtzen and G.M. Laird, written communication, 1998).
Indication of production None
Reserve estimates None.

References

MRDS Number 10307854

References

Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 p., 1 sheet, scale 1:125,000.
Bundtzen, T.K., Kline, J.T., and Clough, J.G., 1982, Preliminary geologiy of the McGrath B-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File report 149, 22 p., 1 sheet, scale 1:40,000.
Solie, D.N., Bundtzen, T.K., and Gilbert, W.G., 1991, K/Ar ages of igneous rocks in the McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File 91-23, 7 p., 1 sheet, 1:250,000 scale.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting)
Last report date 12/4/1998