Unnamed (near Salmon Bay)

Prospects, Inactive

Commodities and mineralogy

Main commodities REE; Th; U
Other commodities Mo
Ore minerals bastnaesite; chalcopyrite; monazite; parisite; thorite
Gangue minerals mainly chert; dolomite-ankerite; alkali feldspar; and quartz

Geographic location

Quadrangle map, 1:250,000-scale PE
Quadrangle map, 1:63,360-scale B-4
Latitude 56.32
Longitude -133.169
Nearby scientific data Find additional scientific data near this location
Location and accuracy Coordinates are approximately the center of several sites that extend along the shoreline from about the mouth of Salmon Bay to Point Colpoys on northeastern Prince of Wales Island; in sections 11 to 13, and 19 to 24, T. 64 S., R. 78 E.

Geologic setting

Geologic description

Steeply-dipping, locally highly radioactive, carbonate veins occur at three localities in hematitically altered, hornfelsed Silurian graywacke. The graywacke is cut by deformed and sheared felsic dikes and undeformed basalt dikes (Brew, 1997 [OF 97-156-F]). The veins contain fluorite, monazite, and a variety of rare-earth fluorocarbonate minerals, some of which are highly radioactive (Houston and others, 1953; Eakins, 1975, and Grybeck, Berg, and Karl, 1984). The veins are up to four feet thick but most are thinner and can be only traced for a few hundred feet where they disappear under vegetation or under water.
The ore mineralogy of the veins varies greatly and includes red hematite, specular hematite, magnetite, pyrite, marcasite, chalcopyrite, thorite, monazite, zircon, parisite, and bastnaesite. Gangue minerals are mainly dolomite-ankerite, with varying amounts of alkali feldspar, chert, quartz, chalcedony, chlorite, epidote, sericite, kaolinite, fluorite, muscovite, apatite, topaz, and garnet. The maximum radioactivity of the veins as measured by the USGS is 0.095 eU; the average is 0.03 eU and the highest uranium content is 0.3% (Houston and others, 1958). The rare-earth carbonate veins contain an average of 0.79% combined rare-earth oxides; one high-grade grab sample contained about 5% rare-earth oxides. Only trace of the rare earths are present in the radioactive veins. Grab samples of veins and felsic dikes taken during USGS work in the early 1980s commonly contain more than 1000 ppm La, and several contain 1000 ppm Mo (Grybeck, Berg, and Karl, 1984).
Warner (1989) sampled several veins at this site to assess their columbium potential. A vein just south of Bay Point contains 0.2% REE across a width of 8.0 feet and a length of 1,300 feet. A vein at Bay Point contains 850 ppm Cb across a width of 3.4 feet and a length of 1,200 feet.
Also see PE055 for a description of very similar if not identical veins to the south on Pitcher Island.
Geologic map unit (-133.170723616733, 56.3196472546588)
Mineral deposit model Uranium and REE carbonate veins
Age of mineralization Unknown other than host rock is Silurian.
Alteration of deposit The Silurian host rock adjacent to both the radioactive carbonate and the REE-carbonate veins are commonly marked by alteration zones a few inches thick adjacent to them marked by dark red by hematitic alteration. The alteration is somewhat more intense adjacent to the radioactive veins.

Production and reserves

Workings or exploration At least 34 claims were staked on the veins in 1951 and 1952 and some were restaked in 1977 (U.S. Bureau of Mines, 1980). There has been little interest or work on these occurrences in recent years because of the relatively depressed market for radioactive elements.
Indication of production None
Reserve estimates Warner (1989) indicates that the veins at this site and similar veins nearby on Pitcher Island (PE055) 'contain combined indicated reserves of approximately 340,000 lb Cb, 2.2 MMlb REE, minimal estimate, and 11,700 lb Th within approximately 763,000 st of rock.'

References

MRDS Number A010332; A010333

References

U.S. Bureau of Mines, 1980, Claim map, Petersburg quadrangle, Alaska: U.S. Bureau of Mines Map 117, 1 sheet, scale 1:250,000.
Reporters H.C. Berg (Fullerton, California) and D.J. Grybeck (USGS)
Last report date 11/1/1998