Unnamed (between Fairweather and Sea Otter Glaciers)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu; Ni
Other commodities Ag; Co; Cr; PGE; V
Ore minerals chalcopyrite; pentlandite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale D-5
Latitude 58.883
Longitude -137.649
Nearby scientific data Find additional scientific data near this location
Location and accuracy Sulfide and heavy oxide boulders occur in the moraine about 4.5-7 miles west-southwest of the top of Mt. Fairweather on an east-heading glacier that is between Fairweather and Sea Otter Glaciers. The coordinates given above are for the approximate location of Bureau of Mines sample 7S008 (Kimball and others, 1978) collected at an elevation of about 3500 feet. The Bureau estimated the collection elevation at about 3700 feet which would be about 0.4 mile to the east of the coordinates assumed here. Sample 7S009 was collected in moraine about 0.4 mile south, slightly east, of the 7S008 location. The exact locations of the samples are not believed to be critical.

Geologic setting

Geologic description

This occurrence consists of boulders on a moraine about 1 mile southwest of the contact of the Mt. Fairweather layered mafic intrusion. The boulders consist of mafic intrusive rocks which contain disseminated sulfides, including chalcopyrite and nickel-bearing minerals. The boulders were derived from the intrusion. An area of bedrock about 1.5 miles northeast of the boulder field is conspicuously copper-stained and may be at or near the source of the boulders.
Samples collected from the moraine field by Plafker and MacKevett (1970) and by Kimball and others (1978) contained as much as 0. 5 percent copper, 0.2 percent nickel, a trace of silver, also as much as 0.005 ounce/ton platinum and 0.008 ounce/ton palladium. A sample collected below the copper-stained bedrock area contained 0.2 percent vanadium.
Geologic map unit (-137.650877675617, 58.8826492154329)
Mineral deposit model Metalliferous glacial moraine. The metalliferous boulders are derived from primary cumulate-sulfide segregations in an layered mafic-ultramafic? intrusion.
Age of mineralization Tertiary.

Production and reserves

Workings or exploration Sampling by Plafker and MacKevett (1970) was followed up by the Bureau of Mines (Kimball and others, 1978). Samples collected by the Bureau (7S008 and 009) contain 0.002-0.005 ounce/ton platinum, 0.008-0.01 ounce/ton palladium, as much as 1.5 ppm Ag, about 0. 5 percent copper and 0.2 percent nickel, and 150 ppm cobalt. A sample of gabbro within the intrusive and below the copper-stained area contained 0.2 percent vanadium.
Indication of production None

Additional comments

The site is in Glacier Bay National Park and Preserve. Further search for the source of the metalliferous moraine would need mountaineering support.

References