| Main commodities | Au |
|---|---|
| Other commodities | Cu; Pb; Zn |
| Ore minerals | arsenopyrite; chalcopyrite; galena; gold; pyrite; sphalerite |
| Gangue minerals | carbonate minerals; chlorite; quartz; white mica |
| Quadrangle map, 1:250,000-scale | VA |
|---|---|
| Quadrangle map, 1:63,360-scale | A-6 |
| Latitude | 61.1837 |
| Longitude | -146.1632 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | This prospect is along the east side of Valdez Glacier at an elevation of about 1,300 feet; it is near the center of the south boundary of section 8, T. 8 S., R. 5 W., of the Copper River Meridian. This prospect is probably located to within one-half mile. It is locality 34 of Cobb and Matson (1972) and locality 26 of Winkler and others (1981 [OFR 80-892-B]). |
Geologic descriptionGold-bearing quartz veins from a few inches to a few feet thick cut metaflysch of the Valdez Group at this locality (Johnson, 1915). A small mill was installed in 1914 but was only operated for a short time. About 50 ounces of gold were reported to have been produced (Jansons and others, 1984). The vein observed by Johnson (1915) was a few inches wide; it trended east-west and was vertical. Specimens said to have come from this property contained gold, pyrite, chalcopyrite, galena, and sphalerite(?). The gold-bearing veins at this locality 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 | (-146.165266279226, 61.1831854749062) |
|---|---|
| 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). |
| Workings or exploration | Open cuts, short adits, and a 20-foot shaft explored this property by 1915 (Johnson, 1915). |
|---|---|
| Indication of production | Yes; small |
| Production notes | About 50 ounces of gold were reported to have been produced from this property (Jansons and others, 1984). |
| MRDS Number | A011475 |
|---|---|
ReferencesGoldfarb, 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.
| |
| Reporters | Travis L. Hudson |
| Last report date | 12/14/2001 |