Unnamed (east of Gakona Glacier)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Au; Cu; Pd; Pt
Other commodities Co
Ore minerals chalcopyrite; magnetite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-3
Latitude 63.213
Longitude -145.072
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site includes several outcrops of mineralized rock in the cirque of an unnamed glacier east of the Gakona Glacier. They are centered about 2.1 miles north-northeast of VABM 5206 'Ona' and about 0.2 mile north of the center of section 4, T. 20 S., R. 14 E.

Geologic setting

Geologic description

The rocks in the area consist of mafic and ultramafic intrusive rocks associated with volcanic rocks that are probably part of the Pennsylvanian to Permian, Slana Spur Formation (Rose, 1967; Nokleberg and others, 1992 [MF]; 1992 [Open-File]; 1992 [Open-File]; Bittenbender and others, 2007). The volcanic rocks are hornfelsed near the intrusive rocks. Cretaceous K/Ar dates from the mafic and ultramafic rocks probably reflect regional metamorphism and their protoliths may be Paleozoic.
Numerous stream-sediment samples collected by the U.S. Geological Survey and Bureau of Land Management that contained anomalous platinum-group elements led to the search for their source (O'Leary and others, 1982; Bittenbender and others, 2003). Bittenbender and others (2007) identified several outcrops, one up to 160 feet long, of pyroxenite and peridotite with persistent but minor chalcopyrite, pyrrhotite, and pyrite. Two, 20-foot samples contained 127 and 65 parts per billion (ppb) palladium, 52 and 36 ppb platinum, 18 and 15 ppb gold, and 824 and 1,005 parts per million (ppm) copper. A sample selected for its high sulfide content contained 144 ppb palladium, 104 ppb platinum, 34 ppb gold, 1,055 ppm copper, and 34 ppm nickel. They considered the mineralization to be too low grade to account for the anomalous PGE in the geochemical samples.
Geologic map unit (-145.074222400607, 63.2125972500081)
Mineral deposit model Disseminated chalcopyrite, pyrrhotite, and pyrite in mafic and ultramafic rocks.
Age of mineralization Unclear whether the host rocks are Cretaceous or Paleozoic.
Alteration of deposit Hornfelsing of volcanic rocks adjacent to mafic and ultramafic intrusive rocks.

Production and reserves

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

References

References

Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2003, Mineral investigations in the Delta River Mining District, east-central Alaska, 2001-2001: Bureau of Land Management-Alaska Open-File Report 91, 82 p.
Bittenbender, P.E., Bean, K.W., Kurtak, J.M., and Deininger, James Jr., 2007, Mineral assessment of the Delta River Mining District area, east-central, Alaska: U.S. Bureau of Land Management, Alaska Technical Report 57, 675 p.
Reporters D.J. Grybeck (Contractor, USGS)
Last report date 5/13/2012