Unnamed (North Crillon Glacier)

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu; Ni
Other commodities Co; Fe; PGE; Ti
Ore minerals chalcopyrite; ilmenite; magnetite; pentlandite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale C-4
Latitude 58.66
Longitude -137.31
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is at an elevation of 3000-3500 feet adjacent to the south wall of North Crillon Glacier. The coordinate location is accurate within about 0.2 mile. It is approximately in the center of the SW 1/4, section 15, T. 37 S., R. 40 E., of the Copper River Meridian The occurrence is approximately that of number 79 of MacKevett and others (1971), number 4 of Cobb (1972), and the location of samples 7S011-015 of Kimball and others (1978).

Geologic setting

Geologic description

The deposit is in the Crillon-LaPerouse layered mafic-ultramafic pluton near its northwest contact with schistose rocks of probable Mesozoic age. The Crillon-LaPerouse body is the largest of four complexes within Glacier Bay National Park and it hosts the Brady Glacier nickel-copper deposit (MF003) of Brew and others (1978).
Disseminated to semi-massive sulfide minerals occur in layered gabbro on the south side of North Crillon Glacier. Conspicuous iron-stained zones estimated to be about 20 feet thick occur in the gabbro body and appear to be continuous for thousands of feet. They are separated by from 30 to 100s of feet of less-stained gabbro. Surface access was gained to one zone that contained a 1-2 foot thick vein of pyrrhotite with some chalcopyrite and ilmenite (Kimball and others, 1978, p. C106-107). The samples contained as much as 3000 ppm nickel, 980 ppm copper, and 0.7 ppm platinum.
In the same area, Kennedy and Walton (1946) reported a 5-foot thick zone traceable for thousands of feet that contained as much as 60 percent ilmenite and some sulfides; the same authors (p. 71) report that the weathered metal-rich outcrops are bright red.
Kimball and others (1978) note the similarity of mineralization with that reported on the north wall of South Crillon Glacier about one and one-half miles to the south, suggesting similar mineralization in heavily stained but inaccessible zones between the two occurrences.
Geologic map unit (-137.311925029968, 58.6596284279167)
Mineral deposit model Sulfide/oxide segregations in a layered mafic complex. Occurrences are of the type associated with 'Synorogenic layered mafic complexes of Tertiary age, southeastern Alaska' of Foley and others (1997, p. 441-443).
Mineral deposit model number 5a?
Age of mineralization Tertiary.
Alteration of deposit Conspicuous iron-stained zones that resulted from oxidation of iron-rich minerals in the oxide-sulfide segregations.

Production and reserves

Workings or exploration
The area is extremely steep, and access to the rock exposures from the glaciers is across bergschrunds. A 1 to 2 foot thick zone rich in pyrrhotite was sampled by Kimball and others (1978) at about 30 foot intervals. Nickel content was as much as 3000 ppm, copper was 980 ppm, and cobalt (probably erroneously called chromium in table C-26B) was as much as to 300 ppm. Trace amounts of platinum and palladium were found in one sample.
Kennedy and Walton (1946) reported one 5-foot thick layer in the same approximate area that contained 60 percent ilmenite.
Indication of production None

Additional comments

Zones possibly project southerly to occurrences on the north side of South Crillon Glacier, and north across North Crillon Glacier to other similar occurrences. The possible continuity of deposits suggests that Brady Glacier-type nickel-copper deposits could exist in the northwest part of the Crillon-La Perouse layered complex.
The site is in Glacier Bay National Park and Preserve.

References