National

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Au
Other commodities Pb
Ore minerals arsenopyrite; galena; gold; pyrite
Gangue minerals carbonate minerals; chlorite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale A-8
Latitude 61.159
Longitude -146.8499
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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).

Geologic setting

Geologic description

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 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 (-146.851971034059, 61.1584696680577)
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).

Production and reserves

Workings or exploration An open cut explored this deposit (Jansons and others, 1984).
Indication of production None

References

MRDS Number A011448

References

Reporters Travis L. Hudson
Last report date 12/14/2001