Unnamed (north wall of South Crillon Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu; Ni
Other commodities Au; Co; Fe
Ore minerals chalcopyrite; magnetite; pentlandite

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale C-4
Latitude 58.64
Longitude -137.304
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The occurrence is on the north wall of South Crillon Glacier at about 3600 feet elevation and about 1.4 miles north-northwest of hill 6902, which was called Mt. Lookout by Rossman (1963, B 1121-F). The location given is that of Kimball and others (1978, fig. C32, occurrence in fig. C33). It is probably 0.2-0.3 mile northeast of location 80 in MacKevett and others (1971) and location 3 of Cobb (1972, MF-436). (Also see MF020).
The occurrence is probably accurate to 0.1 mile.

Geologic setting

Geologic description

The copper-nickel occurrence is in the Crillon-LaPerouse layered mafic-ultramafic pluton, near its western contact. The pluton is of Tertiary age; it was intruded into biotite and hornblende schist (Brew and others, 1978). The schist units are in the upper Chugach terrane of Berg and others (1972).
At the occurrence, iron-stained zones as much as 20 feet thick and traceable visually for thousands of feet occur in layered gabbro. The zones appear to cut the layering of the gabbro at a small angle and are proposed to be shear zones (Kimball and others, 1978, p. C101-102). At one accessible location a 6-8 foot thick heavily iron stained layer was mapped and sampled over a strike length of 120 feet. The zone contains disseminated chalcopyrite and pyrrhotite. Within this zone, a thin (0.6) foot lens about 12 feet long contains semimassive sulfide concentrations of chalcopyrite, pyrrhotite and pentlandite. A sample from the zone contained 3000 ppm copper, 2500 ppm nickel, and 700 ppm cobalt. Gold was detected in two samples; the select sample contains greater than 20 percent iron (Kimball and others, 1978, p. C102 and figures C32 and C33).
Geologic map unit (-137.305928283212, 58.6396306940234)
Mineral deposit model Sulfide segregations in shear zones that cut layered gabbro.
Age of mineralization Tertiary.
Alteration of deposit Conspicuous iron-stained zones.

Production and reserves

Workings or exploration The occurrences are surface exposures with no workings. The U.S. Bureau of Mines (Kimball and others, 1978, p. C101-102, figs. C32 and 33) found as much as 0.24 percent copper, 700 ppm nickel, 150 ppm cobalt, and 0.10 ppm gold in the mineralized zone which is as much as 8 feet thick. Mineralized sheared gabbro contains as much as 0.3 percent copper, 2500 ppm nickel and 700 ppm cobalt in a narrow (0.6 foot) high grade lens within the mineralized zone.
Indication of production None

Additional comments

The area is near the contact of the Crillon-La Perouse stock of layered gabbro in Glacier Bay National Park and Monument. The area is extremely rugged. Other deposits could exist nearby.
The site is in Glacier Bay National Park and Preserve.

References