Unnamed (north wall Grinnell Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Zn
Ore minerals arsenopyrite; chalcopyrite; malachite; pyrite; pyrrhotite; sphalerite
Gangue minerals quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale C-3
Latitude 60.727
Longitude -144.781
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 2200 feet on the north wall of Grinnell Glacier. It is in SE1/4 sec. 24, T. 13 S., R. 3 E., of the Copper River Meridian. Site is accurately located to within 1000 ft. This location is site C-11 of Jansons and others (1984).

Geologic setting

Geologic description

This occurrence consists of sulfide-bearing shear zones 2 to 10 feet wide in slate and greenstone of the Upper Cretaceous Valdez Group (Nelson and others, 1985). Ore minerals include arsenopyrite, chalcopyrite, malachite, pyrite, and pyrrhotite. Four chip samples collected and analyzed by the U.S. Bureau of Mines contained 255 ppm to 0.13% Cu; nine grab samples contained 13 ppm to 0.19% Cu (Jansons and others, 1984). This site is at the eastern end of a 65-mile-long belt of similar rocks that to the west host massive sulfide deposits (Nelson and others, 1984; 1985; Crowe and others, 1992).
A massive-sulfide boulder found on the south side of Grinnel Glacier contained 30% pyrite, 3% chalcopyrite, 1% sphalerite in a quartz-sericite gangue (Kodosky and Teller, 1989). Assays of selected samples ranged from 1100 ppm to 1.8% Cu.
Geologic map unit (-144.782997765789, 60.7264847647281)
Mineral deposit model Besshi massive sulfide (Cox and Singer, 1986; model 24b)
Mineral deposit model number 24b
Age of mineralization Late Cretaceous based on the age of the host rocks.
Alteration of deposit Local alteration of copper minerals.

Production and reserves

Workings or exploration
Site examined during U.S. Bureau of Mines and U.S.G.S. mineral resource assessment of the Chugach National Forest (Jansons and others, 1984; Nelson and others, 1984). Site also examined in 1988 by Kodosky and Teller (1989) for the Chugach Alaska Corporation. Their evaluation indicated some potential for copper mineralization.
Four chip samples collected and analyzed by the U.S. Bureau of Mines contained 255 ppm to 0.13% Cu; nine grab samples contained 13 ppm to 0.19% Cu (Jansons and others, 1984). A massive-sulfide boulder found on the south side of Grinnel Glacier contained 30% pyrite, 3% chalcopyrite, 1% sphalerite in a quartz-sericite gangue. Assays of selected samples ranged from 1100 ppm to 1.8% Cu.
Indication of production None

Additional comments

Chugach Alaska Corporation, Anchorage, Alaska has control of these lands.

References