Unnamed (near Walden Point)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Au
Ore minerals pyrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale B-5
Latitude 55.257
Longitude -131.589
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the shoreline of northwest Annette Island, about 1.2 miles south of Walden Point. The site is in section 28, T. 76 S., R. 91 E., of the Copper River Meridian. It corresponds to loc. 1 in Karl (1992). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this occurrence are Upper Jurassic or Cretaceous flyschlike metasedimentary rocks that are gradationally interbedded with andesitic or basaltic metavolcanic rocks (Berg, 1972 [I 684]; Berg and others, 1988). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.
The occurrence consists of abundant quartz-calcite fissure veins up to at least 3 feet thick in pyritic argillite (Karl, 1992, loc. 1). The veins contain pyrite and inclusions of argillite country rock. The pyrite in the argillite occurs as disseminated cubes as large as a half inch or so. A sample of a quartz vein contained 0.26 ppm Au, 1% As, and 2 ppm Sb.
Geologic map unit (-131.590682713323, 55.2566539370087)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Probably Late Cretaceous or younger.
Alteration of deposit Pyritization of argillic country rock.

Production and reserves

Workings or exploration A sample of a quartz vein contained 0.26 ppm Au, 1% As, and 2 ppm Sb (Karl, 1992, loc. 1).
Indication of production None

References