Sealy-Davis

Mine, Probably inactive

Alternative names

Gold Bluff

Commodities and mineralogy

Main commodities Au
Other commodities Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; gold; pyrite; pyrrhotite; sphalerite
Gangue minerals calcite; chlorite; quartz; white mica

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale A-7
Latitude 61.1277
Longitude -146.5713
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is about 500 feet east of Shoup Bay and one-third mile northwest of the Cliff mine (VA107); it is at an elevation of about 300 feet in the SE1/4 section 36, T. 8 S., R. 8 W., of the Copper River Meridian. This prospect is probably located to within one-quarter mile. It is locality 15 of Cobb and Matson (1972) and locality 12 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

A gold-bearing quartz vein cuts metaflysch of the Valdez Group. The vein is 2 to 3.5 feet thick, strikes northwest, and dips from 60 to 85 degrees south (Johnson, 1915; Smith, 1917). It contains gold, pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, and pyrrhotite. On the Gold Bluff claim, a shear zone with 4-inch-wide quartz lenses and thinner quartz stringers contains calcite, chlorite, pyrite, pyrrhotite, and chalcopyrite (Johnson, 1915). The Gold Bluff deposit was explored by 200-foot adit by 1914. The Sealy-Davis deposit was explored and developed by open cuts and over 1,500 feet of underground workings on four levels. Smith (1917) indicated the workings included adits, raises, winzes, drifts, and stopes over a vertical extent of as much as 450 feet. At least two ore shipments were made by 1915, but the total reported production is only 38 ounces of gold (Jansons and others, 1984). The U.S. Bureau of Mines collected 15 chip samples from three adits that contained 0.1 to 7.9 ppm gold and less than 0.1 to 1.6 ppm silver; one selected grab sample contained 17 ppm gold and 2.8 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 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 (-146.57333294457, 61.1271763946078)
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 The Gold Bluff deposit was explored by 200-foot adit by 1914. The Sealy-Davis deposit was explored and developed by open cuts and more than 1,500 feet of underground workings on four levels. Smith (1917) indicated that the workings included adits, raises, winzes, drifts, and stopes over a vertical extent of 450 feet.
Indication of production Yes; small
Reserve estimates Janson and others (1984) estimate inferred reserves at the Sealy-Davis mine of 50 tons of material containing 7.9 ppm of gold and 1.6 ppm of silver.
Production notes The total reported production from the Sealy-Davis mine is 38 ounces of gold (Jansons and others, 1984).

References

MRDS Number A011456

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.
Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1916: U.S. Bureau of Mines Bulletin 153, 89 p.
Reporters Travis L. Hudson
Last report date 12/14/2001