|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 mine is east of the Johnson Glacier and west of Mineral Creek. It is about nine-tenths of a mile northwest of the Smith Mill on Mineral Creek. The USGS Valdez A-7 topographic map (1996) shows this location with adit symbols and identifies it as the Big Four mine. However, this record follows Cobb and Matson (1972, locality 24), who showed this location to be the group of mines named above.|
An irregular body of quartz and an offshoot vein to it (the Monte Carlo claim) and quartz veins and stockworks (the Chesna claim) cut metaflysch of the Valdez Group (Johnson, 1915). The Monte Carlo quartz vein is as much as 5 feet thick and contains free gold, pyrite, and galena. This deposit was developed by two adits, and 4 tons of ore were mined in 1913. The lower adit was driven 145 feet and did not find the quartz vein. The upper adit intersected the vein about 36 feet in from the portal (Johnson, 1915). The quartz vein on the Chesna claim is 3 to 4 feet thick on the surface but narrows underground where it merges into a stockwork zone of quartz stringers (Johnson, 1915). The Chesna deposits were developed on three levels by adits that totaled about 750 feet in length. A thin quartz vein was explored by a 25-foot adit on the Sunshine claim (Brooks, 1912).These veins are 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||(-146.347356674177, 61.2282818335422)|
|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 Monte Carlo deposit was developed by two adits, and 4 tons of ore were mined in 1913. The lower adit was driven 145 feet and did not find the quartz vein. The upper adit intersected the vein about 36 feet from the portal (Johnson, 1915). The Chesna deposits were developed on three levels by adits that totaled about 750 feet in length. A 25-foot adit was driven on a thin vein on the Sunshine claim (Brooks, 1912).|
|Indication of production||Yes; small|
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.
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|