Unnamed (east of Crater Lake)

Occurrences, Undetermined

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Pb
Ore minerals bornite; chalcopyrite; malachite; pyrite
Gangue minerals calcite; hematite; quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.058
Longitude -131.352
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents three occurrences along a 0.3 mile stretch of the southeast shoreline of Annette Island, about 0.7 mile east of Crater Lake. The occurrences are in section 35, T. 78 S., R. 93 E., of the Copper River Meridian. The coordinates are for the approximate center of this group of occurrences. The site corresponds to loc. 7 in Berg (1972 [I 684]), loc. 153 in Elliott and others (1978), and loc. 39a-c in Karl (1992). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this site include undivided, metamorphosed Silurian and Ordovician volcanic, sedimentary, and intrusive rocks; and Silurian felsic granitic rocks that intrude the undivided assemblage (Berg, 1972). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time, and are intensely sheared, sericitized, and locally permeated with hydrothermal hematite.
The occurrences consist of sparse sulfide pods and sulfide-bearing quartz-calcite veins in the sheared granitic rock (Berg, 1972, loc. 7; Karl, 1992, loc. 39). The metalliferous minerals occur in iron-stained zones an inch or so wide and about a foot long. Sulfides include pyrite, chalcopyrite, and traces of bornite; some of the occurrences contain a little malachite, and the sheared rocks locally contain finely disseminated hematite.
Samples of sulfide-bearing granitic rock and of a pyritic quartz vein contained up to 0.41 ppm Au, 20 ppm Ag, and 2% Cu; a sample of a pyrite- and bornite-bearing quartz-calcite vein contained 0.07 ppm Au, 7 ppm Ag, 1% Cu, and 100 ppm Pb (Karl, 1992, loc. 39a-c).
Geologic map unit (-131.3536803501, 55.0576623166674)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Alteration of deposit Local iron staining. Hydrothermal alteration (sericite, hematite) of country rocks.

Production and reserves

Workings or exploration Samples of sulfide-bearing granitic rock and of a pyritic quartz vein contained up to 0.41 ppm Au, 20 ppm Ag, and 2% Cu; a sample of a pyrite- and bornite-bearing quartz-calcite vein contained 0.07 ppm Au, 7 ppm Ag, 1% Cu, and 100 ppm Pb (Karl, 1992, loc. 39a-c).
Indication of production None

References