Unnamed (near Mount Muravief)

Occurrences, Probably inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Zn
Ore minerals chalcocite; chalcopyrite; malachite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale PA
Quadrangle map, 1:63,360-scale C-3
Latitude 56.51925
Longitude -134.76715
Nearby scientific data Find additional scientific data near this location
Location and accuracy This deposit consists of several occurrences that are strung out in an arc that extends northwest for about a mile. The center of these occurrences is about 0.4 mile west of Mount Muravief and about 0.5 mile east-southeast of the center of section 3, T. 62 S., R. 68 E. The location is accurate and figures 8 and 9 of Bittenbender and others (1999) show the occurrences in detail.

Geologic setting

Geologic description

These occurrences were first identified in the 1930s but there was little systematic work on them until the late 1990s when Bittenbender and others (1999) examined them. The rocks in the vicinity are graywacke and argillite with minor greenstone and volcanic breccia. Locally bedding can be identified but most of the rocks are metamorphosed and often tightly folded and foliated. The rocks generally strike northwest and dip steeply southwest. Loney and others (1975) maps them as part of the Sitka Graywacke of Cretaceous age.
The mineralization is associated with folded layers of greenstone up to 100 feet thick that extend for up to 1,000 feet along strike. Three such occurrence occur along an arcuate band that extends for about 6,000 feet (Bittenbender and others, 1999, figs. 8 and 9). The mineralization consists of chalcopyrite and pyrrhotite that occur both disseminated in the graywacke and greenstone and in massive lenses up to 3 feet thick and 10 feet long. The lenses are often associated with volcanic breccia. Malachite staining is common. Thirty-two samples were collected by Bittenbender and others (1999). They contained up to 6.33 percent copper, 600 parts per billion gold, 14.5 parts per million (ppm) silver, and 2,200 ppm zinc. A sample across 18 feet of mineralization on the west ridge of Mount Muravief contained 1.63 percent copper, 3.6 ppm silver, and 500 ppm zinc. Work by the Bureau of Mines in the late 1960s (Gnagy, 1969) identified bands of chalcocite in samples collected in this vicinity; these samples may come from other as-yet-unidentified mineralization.
Geologic map unit (-134.76892158147, 56.5188749165563)
Age of mineralization Cretaceous or younger based on the age of the host rock.

Production and reserves

Workings or exploration These occurrences were discovered in the 1930s but apparently little work was done on them until the late 1990s when they were mapped in detail by the U.S. Bureau of Land Management.
Indication of production None
Reserve estimates None.

Additional comments

These occurrences are now in the South Baranof Wilderness Area which is closed to mineral exploration and mining.

References

References

Bittenbender, P.B., and Still, J.C., 1997, Mineral investigations on Chichagof and Baranof Islands, and vicinity, southeast Alaska: U.S. Bureau of Land Management, Alaska Open-File Report 67, 34 p.
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.
Gnagy, W.L., 1969, Petrographic report of the U.S. Bureau of Mines on sample submitted by Donald E. MacDonald: Unpublished report, U.S. Bureau of Mines, 1 p. (On file at the Juneau Mineral Information Center, U.S. Bureau of Land Management, Juneau, Alaska.)
Reporters Donald J. Grybeck (U.S. Geological Survey)
Last report date 2-Jan-05