Unnamed (in Port Malmesbury)

Prospects, Probably inactive

Commodities and mineralogy

Main commodities Ag; Au; Bi; Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PA
Quadrangle map, 1:63,360-scale B-1
Latitude 56.30868
Longitude -134.20703
Nearby scientific data Find additional scientific data near this location
Location and accuracy Although claims were located in Port Malmesbury from at least 1926 into the 1950's, there is little information on their location and their deposits. However, Still and others (2002) identified one area of mineralization and that location is used here. The location is accurate but the claims and mineralization are probably more extensive as indicated by mineralized float found at the end of the south arm of Port Malmesbury. The occurrence identified by Still and others (2002) is near triangulation station 'Fan' on the west side of the peninsula that bounds the east arm of Port Malmesbury. It is about 0.8 mile northwest of the southeast corner of section 20, T. 64 S., R. 72 E.

Geologic setting

Geologic description

Although claims were located in Port Malmesbury from at least 1926 into the 1950s (Berg and Cobb, 1967; Still and others, 2002), there is little information on their location and their deposits. However, Still and others (2002) identified one area of mineralization and that location is used here. The location is accurate but the claims and mineralization are probably more extensive.
The rocks in the area are mainly volcanic graywacke of the Bay of Pillers Formation of Late Silurian and Early Ordovician age (Brew and others, 1984). A large Cretaceous granodiorite and diorite stock crops out just to the south.
Mineralization is exposed in the intertidal zone over an area of about 50 feet by 250 feet in tightly folded, silty limestone, mudstone, and graywacke (Still and others, 2002). About 1 percent of the area consists of undeformed quartz veinlets 1 to 6 inches thick that trend northeast and dip northwest. The veinlets contain about 30 percent sulfides, mainly pyrite, sphalerite, and chalcopyrite. Samples contained 7.8 to 10.2 percent zinc with minor copper, silver, and gold. One sample contained 541 parts per million (ppm) bismuth. Another sample contained 1,695 parts per billion gold and 10,000 ppm arsenic.
Still and others (2002) reported old information about occurrences at the head of the southern arm of Port Malmesbury. They could not find them but a piece of quartz float from the area with banded pyrite, arsenopyrite, and minor chalcopyrite contained 0.526 ounce of gold per ton, more than 10,000 ppm arsenic, and 392 ppm bismuth. Samples from the area submitted earlier to the Bureau of Mines consisted of quartz with pyrite, sphalerite, arsenopyrite, galena, and chalcopyrite.
Geologic map unit (-134.208761312998, 56.308302084192)
Mineral deposit model Polymetallic quartz veinlets (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization The quartz-sulfide veinlets cut sedimentary rocks of Late Silurian or Early Ordovician age and may be related to a nearby Cretaceous intrusion.

Production and reserves

Workings or exploration Claims were staked in the area from the 1920s to the 1950s and there probably was considerable prospecting in the area. However, specific workings could not be located by Still and others (2002).
Indication of production None
Reserve estimates None.

Additional comments

MAS number: 021160020.
The area is now part of the Tebenkof Bay Wilderness which is closed to mineral exploration and mining.

References

References

Reporters Donald J. Grybeck (U.S. Geological Survey)
Last report date 2-Jan-05