|Quadrangle map, 1:250,000-scale||CR|
|Quadrangle map, 1:63,360-scale||B-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is a vein that extends from near the head of the south arm of Port San Antonio about 4,000 feet south-southeast toward Mount Miramar. The coordinates are at the north end of the vein in about the center of the SE1/4 section 30, T. 75 S., R. 78 E.|
Geologic descriptionA quartz vein crops out on the beach at the southeast end of the south arm of Port San Antonio (Roehm (1936 [PE 119-3]). It can be traced S65E for about 4,000 feet and averages about 2 to 3 feet thick. The veins cuts both the Cretaceous granite south of Port San Antonio and the Silurian or Ordovician argillite and graywacke of the Descon Formation peripheral to the granite (Eberlein and others, 1983; Brew, 1996). The most intense mineralization is 200 to 300 feet from the granite contact. The vein contains pyrite, sphalerite, and galena, with minor chalcopyrite and bornite. Several channel samples contained a trace of gold and up to 2 ounces of silver per ton. In 1916, the prospector who discovered the vein said that it averaged about $3 per ton in gold (at $20.67 per ounce?) and 4 ounces of silver per ton over a distance of 3,000 feet. The vein has been prospected by several trenches and open cuts. This may be the prospect described by Wright and Wright (1908) as quartz veinlets with galena, sphalerite, and pyrite that cut argillite, but they locate it on the north side of Port San Antonio.
|Geologic map unit||(-133.611214340688, 55.333201673427)|
|Mineral deposit model||Polymetallic vein (Cox and Singer, 1986; model 22c).|
|Mineral deposit model number||22c|
|Age of mineralization||The vein cuts a Cretaceous pluton.|
|Workings or exploration||The vein has been prospected by several trenches and open cuts.|
|Indication of production||None|
Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 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 Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-869, 262 p.
Eberlein, G.D., Churkin, Michael, Jr., Carter, Claire, Berg, H.C., and Ovenshine, A. T., 1983, Geology of the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-91, 52 p.
Roehm, J.C., 1936, Preliminary report of holdings of San Antonio Metals Company, Port San Antonio, Baker Island: Alaska Territorial Department of Mines Property Examination 119-3, 5 p.
Twenhofel, W.S., Robinson, G.D., and Gault, H.R., 1946, Molybdenite investigations in southeastern Alaska: U.S. Geological Survey Bulletin 947-B, p. 7-38.
|Reporters||D.J. Grybeck (Applied Geology)|
|Last report date||5/1/2004|