|Quadrangle map, 1:250,000-scale||PE|
|Quadrangle map, 1:63,360-scale||B-4|
|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.|
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.|
|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.'|
|MRDS Number||A010332; A010333|
Brew, D.A., 1997, Reconnaissance geologic map of the Petersburg B-4 quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-F, 20 p., 1 sheet, scale 1:63,360.
Cobb, E.H., 1972, Metallic mineral resources map of the Petersburg quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-415, 1 sheet, scale 1:250,000.
Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Petersburg quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-870, 53 p.
Eakins, G.R., 1975, Uranium investigations in southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 44, 62 p.
Glover, A.E., 1951, Salmon Bay - Red Bay reconnaissance, Prince of Wales Island: Alaska Territorial Department of Mines Mineral Investigation 117-1, 6 p.
Grybeck, D.J., Berg, H.C., and Karl, S.M., 1984, Map and description of the mineral deposits in the Petersburg and eastern Port Alexander quadrangles: U.S. Geological Survey Open-File Report 84-837, 86 p., 1 sheet, scale 1:250,000.
Houston, J.R., Bates, R.G., Velikanje, R.S., and Wedow, Helmuth, Jr., 1958, Reconnaissance for radioactive deposits in southeastern Alaska, 1952: U.S. Geological Survey Bulletin 1058-A, p. 1-31.
Overstreet, W.C., 1967, The geologic occurrence of monazite: U.S. Geological Survey Professional Paper 530, 327 p.
U.S. Bureau of Mines, 1980, Claim map, Petersburg quadrangle, Alaska: U.S. Bureau of Mines Map 117, 1 sheet, scale 1:250,000.
Warner, J.D., 1989, Columbium-, rare-earth element-, and thorium-bearing veins near Salmon Bay, southeastern Alaska: U.S. Bureau of Mines Open-File Report 6-89, 25 p.
Wedow, Helmuth, Jr., 1953, Preliminary summary of reconnaissance for uranium and thorium in Alaska, 1952: U.S. Geological Survey Circular 248, 15 p.
|Reporters||H.C. Berg (Fullerton, California) and D.J. Grybeck (USGS)|
|Last report date||11/1/1998|