Hecla

Prospect, Probably inactive

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale A-8
Latitude 61.1339
Longitude -146.6652
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the ridge crest at the head of McAllister Creek; it is at an elevation of 1,900 feet just northeast of the center of section 33, T. 8 S., R. 8 W., of the Copper River Meridian. This prospect is probably located to within one-quarter mile. It is locality 9 of Cobb and Matson (1972) and locality 6 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

Shear zones as much as 8 feet thick with irregularly distributed gold-bearing quartz lenses cut metaflysch of the Valdez Group (Brooks, 1912). The quartz lenses also contain arsenopyrite, pyrite, and galena. These mineralized zones 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 (-146.667244935789, 61.1333749128271)
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 At least surface exploration has taken place on this prospect; two claims were staked. and the shear zone was reported to have been traced for about one-half mile (Brooks, 1912).
Indication of production Undetermined

References