|Quadrangle map, 1:250,000-scale||CR|
|Quadrangle map, 1:63,360-scale||B-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The location of this old prospect, which is described only by Chapin (1916), is not known precisely. It probably is about midway between the heads of Trocadero Bay and Twelvemile Arm, within a mile of the center of the SE1/4 section 21, T. 75 S., R. 83 E.|
Geologic descriptionThe Nancy prospect is in greenstone interbedded with argillite and conglomerate (Chapin, 1916). The rocks are part of the Descon Formation of Silurian and Ordovician age (Eberlein and others, 1983; Brew, 1996). The deposit consists of a shear zone 25 feet wide that contains silicified greenstone with pyrite and chalcopyrite. Some quartz stringers also contain pyrite and chalcopyrite. A quartz vein 6 feet thick strikes N70E and dips 45NW. The only workings are shallow trenches.
|Geologic map unit||(-132.803264655817, 55.3494277149386)|
|Mineral deposit model||Shear zone with chalcopyrite and pyrite.|
|Age of mineralization||Unknown, other than that the deposit is in Silurian and Ordovician rocks.|
|Alteration of deposit||Greenstone in a mineralized shear zone is silicified.|
|Workings or exploration||Only surface trenching.|
|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.
Chapin, Theodore, 1916, Mining developments in southeastern Alaska: U.S. Geological Survey Bulletin 642-B, p. 73-104.
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.
|Reporters||D.J. Grybeck (Applied Geology)|
|Last report date||5/1/2004|