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Unnamed (terminus of Nabesna Glacier)

Prospect, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Zn
Ore minerals chalcopyrite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale NB
Quadrangle map, 1:63,360-scale A-4
Latitude 62.1892
Longitude -142.9229
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the southeast side of a small hill (whose summit is at an elevation of 3,290 feet) near the terminus of Nabesna Glacier. It is at an elevation of about 3,100 feet and about 500 feet west of Nabesna River. The prospect is about 0.3 mile north of the center of section 25, T. 5 N., R. 13 E. of the Copper River Meridian. This is locality 6 of Richter (1973), locality 18 of Richter and others (1975), and National Park Service locality WRST-24 (unpublished data). Cobb and Richter (1980) included this prospect under the name 'Nabesna River'. It is located to within a few hundred feet.

Geologic setting

Geologic description

A stockwork of quartz-pyrite veins and veinlets, containing minor chalcopyrite, cuts an altered Tertiary hornblende porphyry dacite dike and Triassic, Nikolai Greenstone. A composite chip sample across 200 feet of altered porphyry contained 1,500 parts per million copper (Richter and Matson, 1970 [OFR 70-276]). Some drilling in this deposit indicates grades as high as 0.3 percent copper, with minor silver and zinc values (Richter and others, 1975). The prospect is near the southwest margin of the mid-Cretaceous Nabesna pluton. K/Ar dates for the Nabesna pluton range from 105 +/- 4.0 to 114 +/- 3.4 Ma (Richter, Lanphere, and Matson, 1975; Richter and others, 1975). The porphyry is inferred to be Tertiary because similar rocks on Monte Cristo Creek and Cross Creek have 17 and 39 Ma K/Ar ages (Richter, 1973).
Geologic map unit (-142.925025721196, 62.1888084158636)
Mineral deposit model Vein stockwork
Age of mineralization Tertiary. Veins cut a porphyry inferred to be Tertiary in age.
Alteration of deposit Unspecified hydrothermal alteration of the porphyry (Richter and Matson, 1970 [OFR 70-276]).

Production and reserves

Workings or exploration Surface exploration and some diamond drilling.
Indication of production None

Additional comments

The prospect is in the Wrangell-St. Elias National Preserve.

References

MRDS Number A011391

References

Cobb, E.H., and Richter, D.H., 1980, Summaries of data on and list of references to metallic and selected nonmetallic mineral deposits in the Nabesna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-927, 117 p.
Richter, D.H., and Matson, N.A., Jr., 1970, Geochemical data from the Nabesna A-4 quadrangle, Alaska: U.S. Geological Survey Open-File Report 70-276, 14 p., 1 sheet, scale 1:63,360.
Richter, D.H., Lanphere, M.A., and Matson, N.A., Jr., 1975, Granite plutonism and metamorphism, eeastern Alaska Range, Alaska: Geological Society of American Bulletin, v. 86, p. 819-820.
Richter, D.H., Singer, D.A., and Cox, D.P., 1975, Mineral resources map of the Nabesna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-655-K, 1 sheet, scale 1:250,000.
Reporters Travis L. Hudson (Applied Geology)
Last report date 11/24/2002