Unnamed (near Pinta Point)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Au; Cu; Zn
Ore minerals chalcopyrite; pyrite; pyrrhotite; sphalerite.

Geographic location

Quadrangle map, 1:250,000-scale SD
Quadrangle map, 1:63,360-scale A-6
Latitude 57.0981
Longitude -133.8839
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is along about 500 feet of the shoreline just east of Pinta Point on the northern tip of Kupreanof Island. It is near the northeast corner of section 24, T. 85 S., R. 72 E. The location is accurate.

Geologic setting

Geologic description

This occurrence was discovered and first described by Still and others (2002) as part of a Bureau of Land Management mineral assessment. The rocks at the occurrence consist of siliceous, dark gray, well-foliated graphitic schist that is tightly folded and multiply deformed. Nearby, the unit includes limestone, chert, felsic schist, and greenstone; Brew and others (1984) mapped it as metamorphosed Stephens Passage Group of late Mesozoic age.
The schist near Pinta Point contains finely disseminated sulfides and sulfide-rich layers for about 500 feet of shoreline. The sulfides locally make up as much as 30 percent of the schist in layers up to 1 foot thick. One 15-foot-thick layer consists of about 10 percent sulfides across its entire width. The sulfides are mainly pyrite and pyrrhotite with minor sphalerite and chalcopyrite. A representative sample across 11 feet of the 15-foot-thick layer contained 43 parts per billion gold, 143 parts per million (ppm) copper, and 624 ppm zinc.
Geologic map unit (-133.88563191819, 57.0977630813602)
Mineral deposit model Sulfides in layers and disseminations in schist; possibly a volcanogenic massive sulfide deposit.
Age of mineralization Probably contemporaneous with the Upper Mesozoic host rock.

Production and reserves

Workings or exploration Only sampling by government geologists who first discovered the occurrences in the late 1990s.
Indication of production None

References

References

Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p.
Reporters D.J. Grybeck (Port Ludlow, WA)
Last report date 4/8/2007