National Prospect, Prince William Sound Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
National Prospect	Prospect
Prince William Sound Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

Location: This prospect is seven-tenths of a mile northwest of the northwest end of Lake No. 1, on the east side of Columbia Glacier; it is at an elevation of about 2,500 feet in the SE1/4 section 21, T. 8 S., R. 9 W., of the Copper River Meridian. This prospect is approximately located, perhaps to within one-half mile. It is locality 6 of Cobb and Matson (1972).
Geology: A 5-foot-wide vuggy, gold-bearing quartz vein cuts metaflysch of the Valdez Group at this locality (Jansons and others, 1984). Johnson (1916) reported that some gold was mortared from this deposit in 1915. The U.S. Bureau of Mines collected a chip sample that contained 0.13 ppm gold and 4.9 ppm silver; a grab sample contained 0.08 ppm gold and 14.1 ppm silver (Jansons and others, 1984). This prospect was explored by an open cut. This deposit 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 devolatization 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).
Workings: An open cut explored this deposit (Jansons and others, 1984).
Age: 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: Country rocks to gold-bearing quartz veins in Valdez Group metaflysch can be variably silicified, carbonitized, and sericitized (Goldfarb and others, 1997).

Commodities (Major) - Au; (Minor) - Pb
Development Status: None
Deposit Model: Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

Other Databases

Link to USGS - Alaska:	VA094

Other Regions, Features and Areas containing this locality

References