|Main commodities||U; Th; REE|
|Ore minerals||bastnaesite; chalcopyrite; red and specular hematite; magnetite; marcasite; monazite; parisite; pyrite; thorite; zircon|
|Gangue minerals||apatite; chalcedony; chert; dolomite-ankerite; chlorite; epidote; alkali feldspar; fluorite; garnet; kaolinite; muscovite; quartz; sericite; topaz|
|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||Several radioactive and non-radioactive REE-bearing carbonate veins occur along the shoreline of Pitcher Island in an area about 500 feet by 100 feet that comprises the northeastern two-thirds of the island. Pitcher Island is about 3.3 miles south, southwest of the mouth of Salmon Bay on northeastern Prince of Wales Island. (Pitcher Island is not named on the current (1998) USGS 1,63,360-scale topographic map, but is identified as such in Houston and others, 1950.) Locality 57 of Grybeck, Berg, and Karl (1984). See also PE056, a similar deposit nearby.|
Two steeply dipping, radioactive carbonate-hematite veins, the Paystreak and Marker veins, are exposed along the shoreline on the northeast end of Pitcher Island (Houston and others, 1958). They each are exposed for about 100 feet, and the largest, the Pitcher vein, is about 2-4 feet thick. The veins consist dominantly of a carbonate of the dolomite-ankerite series, with up to 10 percent alkalic feldspar, and hematite. The radioactive mineral have not fully been defined but the veins contain small to rare amounts of pyrite magnetite, quartz and chalcedony, chlorite, parisite, bastnaesite, muscovite, fluorite, radioactive apatite, monazite, thorite, zircon, and minute amounts of several other minerals. The only uranium bearing minerals that have been identified are thorite, monazite, zircon, and apatite in trace amounts. Only traces of REE are present in the radioactive veins. The maximum radioactivity of the veins as measured by the USGS is 0.095 eU; the average for the Paystreak vein is 0.03 eU and the highest uranium content is 0.3 percent.
There are also three (relatively) non-radioactive, REE-carbonate veins that can be traced along the shoreline on either side of Pitcher Island for up to 300 feet (Houston and others, 1958). They range in size from several inches to as thick as 10 feet. They consistently strike northeast and have steep dips to the southeast. They carry many of the same minerals as the radioactive veins but contain parisite as the main REE-bearing mineral. These rare-earth carbonate veins contain an average of 0.79 percent combined rare-earth oxides; one high-grade grab sample from a similar vein nearby (PE056) contains about 5 percent rare-earth oxides. The radioactive carbonate veins and the REE-carbonate veins are probably genetically related and share much of the same mineralogy. 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, Karl, and Berg, 1984).Recent work by Warner (1989) to define the columbium potential of the deposit indicates the Paystreak vein contains a weighted average of 1670 ppm Th and 0.13 percent REE across a width of 2.6 feet over a length of 180 feet. The host rock for both types of veins is a Silurian sedimentary sequence mainly of volcaniclastic graywacke, argillitic turbidites, and minor limestone that is widespread on the northeast corner of Prince of Wales Island (Brew, 1997 [OF 97-156-F]).
|Geologic map unit||(-133.116719365181, 56.2616465195373)|
|Mineral deposit model||Radioactive carbonate veins 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 commodities.|
|Indication of production||None|
Houston and others (1958) calculated that the Paystreak vein contained 'about 70 pounds of thorium or 80 pounds of thorium dioxide per foot of depth for the 100-foot section of the vein sampled'. (They considered that most of the radioactivity was due to thorium).Warner (1989) indicates that the veins at this site and similar veins nearby at Salmon Bay (PE056) '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|