Unnamed

Occurrence, Inactive

Commodities and mineralogy

Main commodities Mn
Other commodities Fe
Ore minerals manganese carbonate; pyrolusite

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale A-4
Latitude 63.06
Longitude -154.84
Nearby scientific data Find additional scientific data near this location
Location and accuracy The unamed manganese occurrence is situated along the banks of the Kuskokwim River at an elevation of 380 feet in Section 15, T. 28 S., R. 21 E., of the Kateel River Meridian. Patton and Moll (1983) located the occurrence within a 2,500 feet (762 m) radius. Th reporter visited the site in 1988.

Geologic setting

Geologic description

Both iron and manganese oxides are strongly developed in deformed shale and sandstone for about 500 feet along the banks of the Kuskokwim River. The age of the shale is unknown and could be either Paleozoic (Nixon Fork subterrane) or Late Cretaceous (Kuskokwim Group). The apparently bedding in the shale is N 55 E with steep southeasterly dips. A strong shear zone plunges N25E at 20 degrees. The main ore minerals present are pyrolusite and goethite, both of which occur as coatings and impregnations on fracture surfaces in the shear zone. A distinct N10E lineament, which controls the trend of the hills north of the river, runs through the manganiferous area. Although Patton and Moll (1983) suggest this is a sedimentary manganese deposit, field evidence suggests that it may also be an accumulation of iron and manganese oxides within a shear zone. Surface samples have yielded up to 23.00 percent manganese (Berg and Cobb, 1967).
Geologic map unit (-154.842317290726, 63.0593851128102)
Mineral deposit model Sedimentary Mn? (Cox and Singer, 1986; model 34b?).
Mineral deposit model number 34b?
Alteration of deposit Extensive development of iron and manganese oxides.

Production and reserves

Workings or exploration Surface samples contained up to 23 percent manganese (Berg and Cobb, 1967).
Indication of production None
Reserve estimates None.

Additional comments

In Nixon Fork subterrane of Farewell Composite Terrane (Bundtzen and others, 1997), or Cretaceous Kuskokwim Group.

References

MRDS Number A012424

References

Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Reporters Bundtzen, T.K. (Pacific Rim Geological Consulting)
Last report date 6/7/1998