Knowles

Prospect, Probably inactive

Alternative names

Knowles and Backman Property

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale B-4
Latitude 61.3108
Longitude -145.4392
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the north side of upper Mill Creek; the claims extended over the ridge to the north into the headwaters of Glacier Creek (Moffit, 1935, plate 1). It is at an elevation of about 4,800 feet in the NE1/4 section 32, T. 6 S., R. 1 W., of the Copper River Meridian. This prospect is probably located to within one-half mile. It is locality 43 of Cobb and Matson (1972) and locality 35 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

Gold-bearing, partly oxidized, lenticular quartz veins with arsenopyrite and galena cut metaflysch of the Valdez Group at this prospect; the metaflysch is locally cut by felsic dikes (Moffit, 1935). The veins are as much as 14 inches wide and dip 85 degrees east; they trend northerly, but other sheared quartz masses and veins along faults have different orientations. These veins are 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 (-145.441273286643, 61.310298790726)
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 with open cuts.
Indication of production Undetermined

References