Unnamed (south of head of Twelvemile Arm) (ARDF #CR111) Ag, Au, Cu

Unnamed (south of head of Twelvemile Arm)

Prospect, Undetermined

Commodities and mineralogy

Main commodities	Ag; Au; Cu
Ore minerals	chalcopyrite; tetrahedrite
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	CR
Quadrangle map, 1:63,360-scale	B-3
Latitude	55.33123
Longitude	-132.73373
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This is locality 1 of Herreid and Rose (1966) and its location is accurate. It is about 1.2 miles south of the head of Twelvemile Arm and about 0.6 mile south-southwest of the center of section 25, T. 75 S., R. 83 E.

Geologic setting

Geologic description At this site, a series of discontinuous quartz veins that strike N10E and dip 80NW contain small amounts of chalcopyrite and tetrahedrite (Herreid and Rose, 1966). A sample of a vein contained 0.06 ounce of gold per ton and 8.64 ounces of silver per ton. The veins cut massive, light-gray dolomite that is part of the Wales Group of Cambrian and older age. The workings consist of a 110-foot adit and several prospect pits.
Geologic map unit	(-132.735378015682, 55.3308776505451)
Mineral deposit model	Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number	22c
Age of mineralization	Unknown, other than that the deposit consists of quartz veins that cut dolomite of Cambrian or older age.

Production and reserves

Workings or exploration	The workings consist of a 110-foot adit and several prospect pits.
Indication of production	None

References

References Herreid, Gordon, and Rose, A.W., 1966, Geology and geochemistry of the Hollis and Twelvemile Creek area, Prince of Wales Island southeastern Alaska: Alaska Division of Mines and Minerals Geologic Report 17, 32 p.
Reporters	D.J. Grybeck (Applied Geology)
Last report date	5/1/2004