Unnamed (on Flat Island) (ARDF #CR145) Au, Cu

Unnamed (on Flat Island)

Prospect, Undetermined

Commodities and mineralogy

Main commodities	Au; Cu
Ore minerals	chalcopyrite
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	CR
Quadrangle map, 1:63,360-scale	A-3
Latitude	55.0906
Longitude	-132.69376
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This prospect reportedly is near the east shoreline of central Flat Island, in section 24, T. 78 S., R. 84 E.

Geologic setting

Geologic description Bufvers (1967) reports that a rich quartz vein was found on the beach at this site, probably in the late 1880s. Too much powder was used to expose it and most of the gold was blasted into the water. A few thousand dollars in gold was said to have been recovered. Maas and others (1991) searched for this prospect without success, but did find several slightly mineralized quartz veins in the area. The best of these, a sample from Blanket Island with chalcopyrite in the quartz, contained 1,734 parts per million copper and no gold. The rocks in the area are basalt and andesite of Silurian or Ordovician age (Eberlein and others, 1983; Brew, 1996).
Geologic map unit	(-132.695419534492, 55.0902506712496)
Mineral deposit model	Gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number	36a
Age of mineralization	Unknown other than that the prospect is in Silurian or Ordovician rocks.

Production and reserves

Workings or exploration	Some gold was said to be have produced from unspecified, probably surface workings, probably in the 1880s.
Indication of production	Yes; small
Reserve estimates	None.
Production notes	A few thousand dollars in gold (at $20.67 per ounce?) was said to have been recovered in the 1880s.

References

MRDS Number	A010073
References Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000. Bufvers, John, 1967, History of mines and prospects, Ketchikan district, prior to 1952: Alaska Division of Mines and Minerals Special Report 1, 32 p. Cobb, E. H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-869, 262 p. Eberlein, G.D., Churkin, Michael, Jr., Carter, Claire, Berg, H.C., and Ovenshine, A. T., 1983, Geology of the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-91, 52 p. Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p. Maas, K.M., Still, J.C., Clough, A.H., and Oliver, L.K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: southern Prince of Wales Island and vicinity: U.S. Bureau of Mines Open-File Report 33-91, 139 p., 12 sheets, scale 1:63,360.
Reporters	D.J. Grybeck (Applied Geology)
Last report date	5/1/2004