Unnamed (near Cascade Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au
Ore minerals chalcopyrite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale C-5
Latitude 58.664
Longitude -137.439
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is about 0.75 mile south of Cascade Glacier on a steep southwest-facing slope above Crillon Inlet. Iron-stained amphibolite crops out from about 3400 to 3600 foot elevation. The location is probably accurate to 0.15 mile. It is location 19 of Kimball and others (1978).

Geologic setting

Geologic description

Amphibolite schist is extensively exposed in the Fairweather terrane of Brew and others (1978). The rocks probably are in the Chugach terrane of Berg and others (1972).
Amphibolite schist above Cascade Glacier is extensively iron-stained. The stain is developed on sulfidized (pyrite and pyrrhotite(?) layers that crop out from about 3400 to 3600 feet elevation and are traceable along strike for 100s of feet. A float sample contained 1000 ppm copper. Samples representative of the schist unit contained elevated background amounts of copper, as much as 240 ppm (Kimball and others, 1978, p. C125). A heavily stained sulfide-rich lens about 0.4 feet thick and 10 feet long contained 800 ppm copper, 0.15 ppm gold and 7 ppm silver. (About 0.03 weight percent chalcopyrite is equivalent to 1000 ppm copper and chalcopyrite is the most likely copper phase in the unit.)
Kimball and others (1978) proposed that the site should be investigated more thoroughly. Iron-staining is widespread in the schistose units, and copper has been reported elsewhere in schist, as from the moraine coming out of North Crillon Glacier, where amphibolite-quartz schist fragments are stained with copper carbonates (MacKevett and others, 1971, p. 53 after Kennedy and Walton, 1946, p. 71). (The North Crillon location is 86 of plate 1 of MacKevett and others, 1971).
Geologic map unit (-137.440932797752, 58.663634425667)
Mineral deposit model Mineralized amphibolite schist.
Age of mineralization Tertiary.

Production and reserves

Workings or exploration There are no workings. Kimball and others (1978) followed up a USGS collected float sample which contained 1000 ppm copper. Select samples of the iron-stained schist contained as much as 7 ppm silver, 0.15 ppm gold, and 800 ppm copper.
Indication of production None

Additional comments

The area is extremely rugged; higher grade units could exist within the mineralized schist unit, an element of the Chugach terrane. The area is in Glacier Bay National Park and Preserve.

References