Unnamed (south-central Hinchinbrook Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Mn
Other commodities Ba; Fe; Zn
Ore minerals barite; bementite; birnessite; rancieite; todorokite

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale B-7
Latitude 60.352
Longitude -146.425
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is located on Hinchinbrook Island and occupies an area of approximately 0.25 sq. mi. in the center of sec. 34, T. 17 S., R. 7 W., of the Copper River Meridian. The center of the area is at approximately the 1500 ft elevation. Location is accurate to within 600 ft. Shown as site C-98 in Jansons and others (1984).

Geologic setting

Geologic description

This occurrence consists of a 30 x 90 ft. outcrop area of manganese-bearing nodules and encrustations in an interbedded sequence of sedimentary and volcanic rocks of the Tertiary Orca Group (Nelson and others, 1985). The occurrence is interpreted as a sedimentary manganese deposit developed on the sea floor (Goodfellow and others, 1984). Selected samples contained 29-35 percent Mn, 14 percent Fe, 6700 ppm Ba, 3400 ppm Zn (Goodfellow and others, 1984).
Geologic map unit (-146.427022389102, 60.3514449961353)
Mineral deposit model Volcanogenic Mn (Cox and Singer, 1986; model 24c)
Mineral deposit model number 24c
Age of mineralization Probably Tertiary based on the age of the host rocks.

Production and reserves

Workings or exploration
Site discovered during regional geologic mapping (Nelson and others, 1985). Minor interest by industry during exploration activity in mid-1980s.
Selected samples contained 29-35 percent Mn, 14 percent Fe, 6700 ppm Ba, 3400 ppm Zn (Goodfellow and others, 1984).
Indication of production None

Additional comments

Location is within the Chugach National Forest.

References