Pinochle

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Ore minerals arsenopyrite; gold; pyrite
Gangue minerals carbonate minerals; chlorite; quartz; white mica

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale A-6
Latitude 61.201
Longitude -146.1355
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is about nine-tenths of a mile west of the Ramsey-Rutherford Camp; it is at an elevation of about 3,300 feet in the S1/2 section 4, T. 8 S., R. 5 W., of the Copper River Meridian. This prospect is probably located to within one-quarter mile. It is locality 35 of Cobb and Matson (1972) and locality 27 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

A quartz vein, assumed to be gold-bearing, cuts metaflysch of the Valdez Group at this prospect. This vertical vein, which trends N 30-60 W, can be traced on the surface for 110 feet, but it pinches and swells such that the width varies from very thin to 3 feet (Johnson, 1915). About 200 feet of underground workings, a shaft, and several open cuts explored this prospect (Cobb, 1979 [OFR 79-1241]).
This vein is probably similar to others that are widespread 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 (-146.137576489452, 61.2004864391816)
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 About 200 feet of underground workings, a shaft, and several open cuts explored this prospect (Cobb, 1979 [OFR 79-1241]).
Indication of production None

References

MRDS Number A011476

References

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