Unnamed (near Triplet Island)

Prospect, Undetermined

Commodities and mineralogy

Main commodities Cu; Pb; Zn
Ore minerals chalcopyrite; galena; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale C-7
Latitude 57.7254
Longitude -136.2265
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at sea level at the south end of Triplet Island in Portlock Harbor. The prospect is in the NE1/4 sec. 7, T. 48 S., R. 57 E. It is location P-54 of Bittenbender and others (1999) and MAS no. 0021140169 (U.S. Bureau of Land Management, 2002). The location is accurate within 0.2 mile.

Geologic setting

Geologic description

Johnson and Karl (1985) map the rocks in the area of this prospect as hornfelsed Cretaceous graywacke and argillite interbedded with sparse, lenticular beds of recrystallized basalt ('greenstone'). The rocks are cut by numerous steeply-dipping, mainly northwest-striking faults.
Bittenbender and others (1999), citing Still and Weir (1981), describe this prospect as a volcanogenic massive sulfide deposit containing copper, lead, and zinc. A sample across a 0.1-foot lens of sphalerite-rich rock contained 35 percent zinc, 0.15 percent lead, and 0.11 percent copper. The host rock is not specified, nor are any of the sulfides identified.
Geologic map unit (-136.228328548275, 57.7250275227124)
Mineral deposit model Volcanogenic massive-sulfide deposit?
Age of mineralization If the prospect is a volcanogenic massive sulfide deposit, it probably is Cretaceous, the age of the greenstone host rock.

Production and reserves

Workings or exploration Only surface sampling.
Indication of production Undetermined

Additional comments

The prospect is in West Chichagof-Yakobi Wilderness.



Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p.
U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]
Reporters H.C. Berg (U.S. Geological Survey)
Last report date 10/16/2004