Unnamed (Chenega Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Mn
Ore minerals magnetite; pyrite; pyroxmangite; pyrrhotite; rhodochrosite
Gangue minerals chert

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale B-3
Latitude 60.3708
Longitude -147.9937
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is located at tidewater in a small bay on the northeast shore of Chenega Island. It is in the NW1/4 section 12, T. 3 N., R. 8 E., of the Seward Meridian. This is location S-90 of Jansons and others (1984). This location is accurate to within a quarter of a mile.

Geologic setting

Geologic description

The occurrence consists of a resistant calcareous chert bed that is exposed between the beach gravel and muskeg vegetation. The exposure is 6 feet wide by 50 feet long; the bed strikes N 10 E and dips 80W (Kurtak and Jeske, 1986). The chert is interbedded with calcareous shale and phyllite. Manganese minerals in the chert include rhodochrosite and pyroxmangite. Other minerals include magnetite, pyrrhotite, and a trace of pyrite (Kurtak and Jeske, 1986). The bedrock in this area is Orca Group of early Tertiary age (Nelson and others, 1985). A 3.5-foot-wide chip sample contained 17 percent manganese; two grab samples contained 36 and 37 percent manganese (Kurtak and Jeske, 1986).
Geologic map unit (-147.995792611997, 60.3702606117246)
Mineral deposit model Volcanogenic Mn (Cox and Singer, 1986; model 24c)
Mineral deposit model number 24c
Age of mineralization Tertiary or younger; the mineralization is in rocks of the Orca Group of Tertiary age.

Production and reserves

Workings or exploration A 3.5-foot-wide chip sample contained 17 percent manganese; two grab samples contained 36 and 37 percent manganese (Kurtak and Jeske, 1986). No workings or improvements are present.
Indication of production None
Reserve estimates Inferred reserves are 700 tons of ore at an unknown grade (Kurtak, 1982).

References