|Quadrangle map, 1:250,000-scale||KC|
|Quadrangle map, 1:63,360-scale||A-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This site includes 4 occurrences in about a half-mile-square area northeast of Round Mountain. The occurrences are in sections 3, 9, and 10, T. 77 S., R. 92 E., of the Copper River Meridian, and are at elevations of 1200-1500 feet on and near the northeast spur of Round Mountain, and about a mile northeast of the top of the mountain. The map site is at the approximate center of the area of occurrences. The site corresponds to loc. 21 in Berg (1972 [I 684]), loc. 132 in Elliott and others (1978), and loc. 11a-d in Karl (1992). The location is accurate within about 0.1 mile.|
The hostrocks of these occurrences are bounded by faults, and consist of recrystallized, Upper Triassic sedimentary and volcanic rocks that unconformably overlie a sequence of undivided, metamorphosed Silurian and Ordovician volcanic, sedimentary, and intrusive rocks (Berg, 1972). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.The occurrences are in bleached, Upper Triassic, rhyolite tuff-breccia, black shale and limestone, and conglomerate. They consist of quartz-calcite-pyrite fissure veins in shear zones; of minute cubes of pyrite disseminated in the country rocks; and of local copper-staining (malachite) (Berg, 1972; Karl, 1992). A sample of felsic tuff-breccia contained 150 ppm Pb; a sample of a quartz-calcite-pyrite fissure vein contained 300 ppm Cu; and a sample of sheared rhyolite breccia contained 700 ppm Pb (Karl, 1992, loc. 11a-d).
|Geologic map unit||(-131.544681413463, 55.2116549595515)|
|Mineral deposit model||Polymetallic veins? (Cox and Singer, 1986; model 22c)|
|Mineral deposit model number||22c?|
|Age of mineralization||The fissure veins probably are Late Cretaceous or younger in age.|
|Alteration of deposit||Local bleaching and iron and copper staining.|
|Workings or exploration||A sample of felsic tuff-breccia contained 150 ppm Pb; a sample of a quartz-calcite-pyrite fissure vein contained 300 ppm Cu; and a sample of sheared rhyolite breccia contained 700 ppm Pb (Karl, 1992, loc. 11a-d).|
|Indication of production||None|
Berg, H.C., 1972, Geologic map of Annette Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-684, 8 p., 1 sheet, scale 1:63,360.
|Reporters||H.C. Berg, USGS|
|Last report date||7/6/1999|