Unnamed (northwest of the terminus of Chistochina Glacier)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Au; Cu; Pd; Pt
Ore minerals chalcopyrite; magnetite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-2
Latitude 63.1998
Longitude -144.8786
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on a ridge on the northwest side of the terminus of the Chistochina Glacier at an elevation of about 5,700 feet. It is about 0.4 mile northeast of the center of section 9, T. 20 S., R. 15 E.

Geologic setting

Geologic description

The rocks in the area consist of mafic and ultramafic intrusive rocks associated with volcanic rocks, probably part of the Pennsylvanian to Permian, Slana Spur Formation (Rose, 1967; Nokleberg and others, 1992 [MF]; 1992 [Open-File]; Bittenbender and others, 2007). Nokleberg and others (2007 [MF] suggest that Cretaceous K/Ar dates (123-126 Ma) from the mafic and ultramafic rocks reflect regional metamorphism of rocks deposited in the Paleozoic. Bittenbender and others (2007) have also dated the rocks as Early Cretaceous but interpret the dates as the age of primary crystallization. The mafic and ultramafic rocks are cut by discontinues inch-wide veinlets of magnetite.
As described by Rose (1967), the host rock of the mineralization is dunite in a composite ultramafic body that also contains peridotite, pyroxenite, and hornblendite (Rose, 1967). Thin veinlets of cross-fiber chrysotile cut the dunite. Boulders of hornblendite near the site contain as much as 10 percent magnetite. Bittenbender and others (2007) examined the occurrence and collected four samples. The richest sample was from serpentinized pyroxenite with minor chalcopyrite and copper staining. It contained 1.8 percent copper, 125 parts per billion (ppb) palladium, 48 ppb platinum, and 58 ppb gold. A sample from a gabbro dike contained 3,870 parts per million (ppm) copper, 462 ppb palladium, 326 ppb platinum, and 348 ppb gold.
Geologic map unit (-144.880829035415, 63.1994040194846)
Mineral deposit model Disseminated chalcopyrite and magnetite in mafic-ultramafic rocks.
Age of mineralization Uncertain whether the host rocks are Late Cretaceous or as old as Paleozoic.
Alteration of deposit Mafic and ultramafic rocks are locally serpentinized.

Production and reserves

Workings or exploration Only limited sampled by state and federal agencies.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS); D.J. Grybeck (Contractor, USGS)
Last report date 5/13/2012