Unnamed (west shore of South Arm)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ba
Ore minerals chalcopyrite; pyrite; pyrrhotite
Gangue minerals chert

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale B-2
Latitude 60.3763
Longitude -147.7108
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is located near tidewater on the west shore of South Arm of Bay of Isles. It is in the SE1/4 section 4, T. 3 N., R. 10 E., of the Seward Meridian. This is location 209 of Tysdal (1978 [MF-880-A]) and location S-70 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 thin chert lens a few feet long surrounded by graywacke (Kurtak and Jeske, 1986). Nelson and others (1985) mapped this area as Orca Group of early Tertiary age. As much as 1 percent pyrite is concentrated at the chert and graywacke contact (Richter, 1965). Tysdal (1978 [MF-880-A]) indicated that chalcopyrite and pyrrhotite occurred in the shale (not graywacke) at its contact with the chert lens. A single sample from the mineralized graywacke contained 125 ppm copper and 481 ppm barium (Kurtak and Jeske, 1986).
Geologic map unit (-147.712814034234, 60.3757092972879)
Mineral deposit model Besshi massive sulfide (Cox and Singer, 1986; model 24b)
Mineral deposit model number 24b
Age of mineralization Tertiary or younger; the occurrence is in rocks of the Orca Group of Tertiary age.

Production and reserves

Workings or exploration A single sample from the mineralized graywacke contained 125 ppm copper and 481 ppm barium (Kurtak and Jeske, 1986). No workings or improvements are reported in the literature.
Indication of production None

Additional comments

This occurrence is not of economic significance, but it is a good example of structural control of ore deposits.

References