|Quadrangle map, 1:250,000-scale||VA|
|Quadrangle map, 1:63,360-scale||A-7|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is on the southwest side of Uno Basin, about seven-tenths of a mile northwest of peak 2733; it is at an elevation of about 1,800 feet in the NW1/4 section 30, T. 8 S., R. 7 W., of the Copper River Meridian. This prospect is probably located to within one-quarter mile. It is locality 16 of Cobb and Matson (1972) and locality 13 of Winkler and others (1981 [OFR 80-892-B]).|
Geologic descriptionA gold-bearing quartz vein from 1 to 10 feet thick cuts sheared metaflysch of the Valdez Group (Johnson, 1915). The quartz vein contains calcite, chlorite, pyrite, chalcopyrite, arsenopyrite, sphalerite, and galena. The vein was traced on the surface for about 100 feet and explored by a 140-foot-long adit, a 90-foot-long crosscut, and 50 feet of drifts (Johnson, 1915; Jansons and others, 1984). Four U.S. Bureau of Mines grab samples from this area contained as much as 1.5 ppm gold and 19 ppm silver (Jansons and others, 1984). This vein is probably similar to other gold-bearing quartz veins cutting metaflysch of the Valdez Group in the southern Valdez quadrangle. Data summarized by Goldfarb and others (1997) show that gold-bearing quartz veins in the Valdez Group commonly contain pyrite, arsenopyrite, carbonate minerals, chlorite, and white mica and formed from water-rich fluids with 5 to 15 mole percent CO2 and significant amounts of CH4, N2, and H2S. The vein-forming fluid salinities were less than 8 percent, vein formation temperatures ranged from 225 to 375 degrees centigrade, and emplacement depths varied from 3 to 10 kilometers. The vein-forming fluids were produced by metamorphic devolatilization reactions. Radiometric dating indicates that the veins formed from 57 to 49 Ma (Goldfarb and others, 1997, p. 171), when deep parts of the accreted Valdez Group flysch underwent high-grade metamorphism and partial melting (Hudson, 1994).
|Geologic map unit||(-146.556537250806, 61.1464773847755)|
|Mineral deposit model||Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)|
|Mineral deposit model number||36a|
|Age of mineralization||Radiometric dating indicates that the gold-bearing quartz veins in the Valdez Group formed from 57 to 49 Ma (Goldfarb and others, 1997, p. 171), when deep parts of the accreted Valdez Group flysch underwent high-grade metamorphism and partial melting (Hudson, 1994).|
|Alteration of deposit||Country rocks to gold-bearing quartz veins in Valdez Group metaflysch can be variably silicified, carbonitized, and sericitized (Goldfarb and others, 1997).|
|Workings or exploration||The vein was traced on the surface for about 100 feet and explored by a 140-foot-long adit, a 90-foot-long crosscut, and 50 feet of drifts (Johnson, 1915; Jansons and others, 1984).|
|Indication of production||Undetermined|
|Production notes||Production has not been reported from this deposit (Jansons and others, 1984).|
Cobb, E.H., and Matson, N.A., Jr., 1972, Metallic mineral resources map of the Valdez quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-438, 1 sheet, scale 1:250,000.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Hudson, T.L., 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol. G-1, p. 657-670.
Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral occurrences in the Chugach National Forest, southcentral Alaska: U.S. Bureau of Mines Mineral Land Assessment 5-84, 218 p., 2 sheets, scale 1:250,000.
Johnson, B.L., 1915, Mining on Prince William Sound: U.S. Geological Survey Bulletin 622-E, p. 131-139.
Winkler, G.R., Miller, R.J., MacKevett, E.M., Jr., and Holloway, C.D., 1981, Map and summary table describing mineral deposits in the Valdez quadrangle, southern Alaska: U.S. Geological Survey Open-File Report 80-892-B, 2 sheets, scale l:250,000.
|Reporters||Travis L. Hudson|
|Last report date||12/14/2001|