Minnie; Olson; Bald Mountain Group Mine, Prince William Sound Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
Minnie; Olson; Bald Mountain Group Mine	Mine
Prince William Sound Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

Location: This mine is eight-tenths of a mile southeast of Mount Cameron at an elevation of about 3,000 feet in the SW1/4 section 3, T. 8 S., R. 8 W., of the Copper River Meridian. This mine is located to within one-half mile. It is locality 4 of Cobb and Matson (1972).
Geology: Gold-bearing quartz veins as much as 2 feet wide cut metaflysch of the Valdez Group (Johnson, 1915). The veins strike northwest and dip steeply to both the north and south. The quartz veins also contain pyrite, sphalerite, galena, and a brown-weathering carbonate mineral. The Minnie deposit was explored by three or four short adits, and the Olson deposit was explored by an adit and drifts that totaled about 250 feet in length (Johnson, 1915). Open cuts explored the deposits on the surface. A few tons of ore were processed from each deposit. The U.S. Bureau of Mines collected three chip samples from the Minnie deposit that contained as much as 12.0 ppm gold and 7.0 ppm silver; a grab sample contained 45 ppm gold and 12.5 ppm silver (Jansons and others, 1984). These deposits 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 devolatization 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).
Workings: The Minnie deposit was explored by three or four short adits, and the Olson deposit was explored by an adit and drifts that totaled about 250 feet in length (Johnson, 1915). Open cuts explored the deposits on the surface.
Age: 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: Country rocks to gold-bearing quartz veins in Valdez Group metaflysch can be variably silicified, carbonitized, and sericitized (Goldfarb and others, 1997).
Production: A few tons of ore were processed from each deposit (Johnson, 1915).

Commodities (Major) - Au; (Minor) - Pb, Zn
Development Status: Yes; small
Deposit Model: Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

Other Databases

Link to USGS - Alaska:	VA096

Other Regions, Features and Areas containing this locality

References