Unnamed (on Shapka Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Sb
Other commodities As
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SB
Quadrangle map, 1:63,360-scale D-4
Latitude 55.887
Longitude -159.128
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is located on the shore of Shapka Island approximately 2 miles south of Perryville. It represents several samples collected on the shoreline around the island. The site is referred to as SBRGX-47 in Wilson and others (1988, locality 21). The location is accurate to within 1,200 feet.

Geologic setting

Geologic description

This occurrence is in rocks mapped as Eocene to Oligocene Mashik Formation (Wilson and others, 1995). Potassium-argon dating of hornblende from leuco-basalt gave an age of 43 million years (Wilson and others, 1994). Sandstone and siltstone are cut by felsic and porphyritic hornblende andesite(?) or diorite dikes. Some of the dikes are sulfide-bearing (Wilson and others, 1988). A slightly altered hornblende diorite dike is cut by a shear zone or by fractures filled with carbonate or quartz veins. Rock samples are reported to be anomalous in antimony and arsenic.
Geologic map unit (-159.12999573232, 55.8862088254276)
Age of mineralization Eocene or younger.
Alteration of deposit Some of the dikes are described as 'altered'.

Production and reserves

Workings or exploration Rock samples 84ACe113-116, collected by the U.S. Geological Survey in the mid-1980s, were reported to be anomalous in antimony and arsenic (Wilson and others, 1988).
Indication of production None

References