Great Northern Development Company

Prospects, Inactive

Commodities and mineralogy

Main commodities Ag; Cu
Other commodities Au
Ore minerals azurite; bornite; chalcopyrite; limonite; malachite; pyrite
Gangue minerals calcite

Geographic location

Quadrangle map, 1:250,000-scale MC
Quadrangle map, 1:63,360-scale C-8
Latitude 61.6279
Longitude -143.8423
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is near the head of Clear Creek. It is at an elevation of about 5,500 feet, 2,000 feet northwest of elevation 6085 and 2,000 feet north of the center of section 7, T. 3 S., R. 9 E. of the Copper River Meridian. This is locality 137 of MacKevett (1976) and locality 22 of MacKevett and others (1978). The location is accurate to within about 100 feet. Cobb and MacKevett (1980) included this prospect under the name 'Clear Cr.'.

Geologic setting

Geologic description

This is one of several prospects in the Clear Creek area that were explored by the Great Northern Development Company in the early 1900s (Moffit and Mertie, 1923). The deposits at this location were explored between 1914 and 1916 by several adits and related underground workings totaling a few thousand feet in length (Moffit and Mertie, 1923; MacKevett, 1976). Altered veins to 2 feet wide are localized along faults that cut Triassic Nikolai Greenstone and small intrusions of Jurassic granodiorite (Van Alstine and Black, 1946; MacKevett, 1976). The vein width of 2 meters reported by MacKevett (1976) is much wider than that of early reports and may be a typographical error. Some pyrite and chalcopyrite is locally disseminated in the granodiorite. The altered fault zones and associated veins contain small amounts of calcite, pyrite, chalcopyrite, bornite, limonite, malachite, and azurite (Van Alstine and Black, 1946). A chip sample of the mineralization contained 0.5 part per million (ppm) gold, 5 ppm silver, and 20,000 ppm copper (MacKevett, 1976). Some exploration took place in this area as late as the 1970s. The widespread deposition of copper in Triassic greenstone and limestone of the area is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic or Early Cretaceous (MacKevett and others, 1997). Copper-bearing minerals were deposited in the underlying Nikolai Greenstone at about 112 Ma (Silberman and others, 1980).
Geologic map unit (-143.844387544411, 61.6274371044397)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23)
Mineral deposit model number 23
Age of mineralization Cretaceous? The widespread deposition of copper in Triassic greenstone and limestone of the area is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic or Early Cretaceous (MacKevett and others, 1997). Copper-bearing minerals were deposited in the underlying Nikolai Greenstone at about 112 Ma (Silberman and others, 1980).
Alteration of deposit Oxidation.

Production and reserves

Workings or exploration This is one of several prospects in the Clear Creek area that were explored by the Great Northern Development Company in the early 1900s (Moffit and Mertie, 1923). The deposits at this location were explored between 1914 and 1916 by several adits and related underground workings totaling a few thousand feet in length (Moffit and Mertie, 1923; MacKevett, 1976). Some exploration took place in this area as late as the 1970s.
Indication of production None

Additional comments

The locality is in the Wrangell-Saint Elias National Park and Preserve.

References

MRDS Number A011739

References

Reporters Travis L. Hudson (Applied Geology, Inc.)
Last report date 1/12/2003