Unnamed (on Shrubby Island)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Au
Ore minerals galena; pyrite; sphalerite
Gangue minerals calcite

Geographic location

Quadrangle map, 1:250,000-scale PE
Quadrangle map, 1:63,360-scale A-3
Latitude 56.2385
Longitude -132.986
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is in a borrow pit about 0.8 mile east-southeast of the northwest tip of Shrubby Island; the pit is shown on the 1:63,360-scale topographic map. It is in the NE1/4, section 14, T. 65 S., R. 80 E.

Geologic setting

Geologic description

Still and others (2002) visited the borrow pits on Shubby Island and examined the road cuts on the logging roads of the island to try to discover the source of the strongly anomalous stream sediment samples that were reported earlier by the U.S. Geological Survey. They discovered mineralization in a borrow pit on the northwest end of the island. The mineralization consists of pods of sulfides in blocky, dark gray to white limestone of the Heceta Limestone (Karl and others, 1999). The pods are up to 2 feet long, 1 foot thick, and are mainly of fine grained pyrite with sphalerite and minor galena. The sulfides also occur in a network of thin veinlets that cut the limestone in an area about 10 feet in diameter. A 0.5-foot sample across one of the pods contained 8.1 percent zinc, and 3,646 parts per million (ppm) lead. A sample across 2.1 feet of the sulfide veinlets in the limestone contained 1.3 percent zinc and 476 ppm lead. The highest gold value in the samples Still and others (2002) collected was 19 parts per billion; the highest silver value was 2.6 ppm.
Geologic map unit (-132.987713294603, 56.2381454823341)
Mineral deposit model Pb-Zn sulfide pods in limestone.
Age of mineralization Silurian or younger based on the age of the Heceta Limestone that hosts the mineralization.

Production and reserves

Workings or exploration Only sampling by government engineers and geologists.
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