45

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Au
Other commodities Cu; Pb; Zn
Ore minerals arsenopyrite; galena; gold; pyrite; sphalerite
Gangue minerals carbonate minerals; chlorite; quartz; white mica

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale A-7
Latitude 61.2086
Longitude -146.3473
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the north side of the ridge between Brevier and Mineral Creeks at an elevation of about 2,400 feet in the NW1/4 section 5, T. 8 S., R. 6 W., of the Copper River Meridian. This prospect is probably located to within one-half mile. It is locality 25 of Cobb and Matson (1972) and locality 21 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

Thin gold-bearing quartz veins cut metaflysch of the Valdez group at this locality (Johnson, 1916). Fracture-filling veins in metagraywacke strike northwest and dip 70 degrees north. The veins are 1 to 6 inches thick and contain free gold, galena, sphalerite, and chalcopyrite. A 20-foot adit and an open cut explored this deposit in 1913 (Johnson, 1916). 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 (-146.349350927676, 61.2080810574046)
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 A 20-foot adit and an open cut explored this deposit in 1913 (Johnson, 1916).
Indication of production Undetermined

References