Unnamed (Crab Bay area)

Occurrences, Undetermined

Commodities and mineralogy

Main commodities Ag; barite; Pb; Zn
Ore minerals barite; galena; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.119
Longitude -131.389
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents five occurrences in about a half-mile-square area, west of the inner arm of Crab Bay. All of the occurrences are about 0.4-0.5 mile inland from the bay: three are at elevations of 100-200 feet, and one is at an elevation of about 400 feet. The occurrences are in section 10, T. 78 S., R. 93 E., of the Copper River Meridian. The map site is at the approximate center of the area of occurrences. The site corresponds to loc. 32a-d in Karl (1992). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of the site are recrystallized, locally phyllitic, rhyolite, and massive, dolomitic limestone that conformably overlies the rhyolite (Berg, 1972 [I 684]; Berg and others, 1988). These Upper Triassic rocks were regionally metamorphosed to greenschist grade in Late Cretaceous time.
The occurrences are quartz fissure veins in dolomite and at a dolomite-rhyolite contact (Karl, 1992a-d). The veins, which contain barite, galena, and sphalerite, have the character of ladder veins, and are most abundant at the dolomite-rhyolite contact.
At a locality informally called 'Cave Creek,' exploration in the 1970s by private interests showed galena and sphalerite in quartz veins up to 3 feet thick, as well as disseminated galena and sphalerite, in a 75-foot-wide zone in dolomite. Their exploration reportedly also showed two other occurrences of sulfide-bearing quartz veins at the dolomite-rhyolite contact. A sample of a quartz vein contained 5000 ppm Ba (Karl, 1992, loc. 32a-d).
Geologic map unit (-131.390680656457, 55.1186596150248)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Probably Late Cretaceous or younger.
Alteration of deposit Dolomitization of limestone country rock.

Production and reserves

Workings or exploration At a locality informally called 'Cave Creek,' exploration in the 1970s by private interests showed galena and sphalerite in quartz veins up to 3 feet thick, as well as disseminated galena and sphalerite, in a 75-foot-wide zone in dolomite. Their exploration reportedly also showed two other occurrences of sulfide-bearing quartz veins at the dolomite-rhyolite contact. A sample of a quartz vein contained 5000 ppm Ba (Karl, 1992, loc. 32a-d).
Indication of production None

References