Unnamed (northwest of terminus of Nabesna Glacier)

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu; Pb; Zn
Ore minerals chalcopyrite; galena; gold; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale NB
Quadrangle map, 1:63,360-scale A-4
Latitude 62.2003
Longitude -142.9503
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the west side of Nabesna River valley about 1.5 miles northwest of the terminus of Nabesna Glacier. It is at an elevation of about 3,500 feet, 5,500 feet northwest of hill 3290. The site is near the center of section 28, T. 5 N., R. 13 E. of the Copper River Meridian. This is locality 5 of Richter (1973), locality 17 of Richter and others (1975), and at least close to National Park Service locality WRST-23 (unpublished data). It was included by Cobb and Richter (1980) as an 'Unnamed prospect'. It is located to within a few hundred feet.

Geologic setting

Geologic description

Abundant quartz veins and irregular pods of quartz up to 1 foot thick in recrystallized Triassic limestone contain sphalerite, galena, and minor chalcopyrite. A chip sample across a 6-inch-wide sphalerite-chalcopyrite-galena vein contained 2.4 parts per million (ppm) gold, 200 ppm silver, and more than 2 percent copper, 2 percent lead, and 1 percent zinc (Richter and Matson, 1970 [OFR 70-276]). A chip sample across a 1-foot-wide quartz vein contained 0.2 parts per million (ppm) gold, 150 ppm silver, 300 ppm molybdenum, 5,000 ppm copper, 5,000 ppm lead, and 7,000 ppm zinc. The prospect is in the contact zone of the mid-Cretaceous Nabesna pluton (Richter, 1973). K/Ar dates for the Nabesna pluton range in age from 105 +/- 4.0 to 114 +/- 3.4 Ma (Richter and others, 1975; Richter, Lanphere, and Matson, 1975).
Geologic map unit (-142.95242572019, 62.1999090834001)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Mid-Cretaceous. K/Ar dates for the Nabesna pluton range from 105 +/- 4.0 to 114 +/- 3.4 Ma (Richter and others, 1975; Richter, Lanphere, and Matson, 1975).
Alteration of deposit Recrystallization of limestone adjacent a granodiorite pluton. Oxidation.

Production and reserves

Workings or exploration Small prospect pits have been dug on the veins.
Indication of production None

Additional comments

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

References