Bessie Williams

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Au
Ore minerals arsenopyrite; 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 61.1516
Longitude -146.7737
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is about one-half mile northwest of the east end of Lake No. 1 and 1.2 miles northwest of Anderson Pass; it is at an elevation of about 3,000 feet on the boundary between sections 25 and 26, T. 8 S., R. 9 W., of the Copper River Meridian. This prospect is probably located to within one-half mile. It is locality 8 of Cobb and Matson (1972) and locality 5 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

A 3-foot-thick shear zone with quartz veins as much as 1 foot thick cuts metaflysch of the Valdez Group at this prospect (Jansons and other, 1984). It was explored by a 25-foot-long adit. A chip sample collected by the U.S. Bureau of Mines contained 0.42 ppm gold and 0.3 ppm silver (Jansons and others, 1984). 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 (-146.775768443989, 61.1510724485487)
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 This prospect was explored by a 25-foot-long adit (Jansons and others, 1984).
Indication of production None

References

MRDS Number A011449

References

Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Hudson, T.L., 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol. G-1, p. 657-670.
Pickthorn, W.J., 1982, Stable isotope and fluid inclusion study of the Port Valdez district, southern Alaska: Los Angeles, University of California at Los Angeles, M.S. thesis, 66 p.
Reporters Travis L. Hudson
Last report date 12/14/2001