| Main commodities | Au |
|---|---|
| Other commodities | Pb |
| Ore minerals | arsenopyrite; galena; gold; limonite; pyrite |
| Gangue minerals | carbonate minerals; chlorite; quartz; white mica |
| Quadrangle map, 1:250,000-scale | VA |
|---|---|
| Quadrangle map, 1:63,360-scale | B-4 |
| Latitude | 61.3157 |
| Longitude | -145.4047 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | This mine is on the east side of the cirque at the head of Boulder Creek (Moffit, 1935, plate 1). The map site is 2.1 miles northwest of Mount Tiekel at an elevation of about 4,500 feet in the SE1/4 section 28, T. 6 S., R. 1 W., of the Copper River Meridian. This mine is probably located to within one-half mile. It is locality 44 of Cobb and Matson (1972) and locality 36 of Winkler and others (1981 [OFR 80-892-B]). |
Geologic descriptionOxidized, gold-bearing quartz veins with arsenopyrite and galena cut metaflysch of the Valdez Group at this mine; the metaflysch is locally cut by felsic dikes (Moffit, 1918). The veins, varying from 1 to 6 feet thick, and felsic dikes trend N20W parallel to a prominent joint set. An open cut and adit with about 125 feet of underground workings developed this mine. A small mill was installed in 1918; oxidized ore was amalgamated in an arrastre on site or shipped to the Cliff mine (VA107) for milling. Moffit (1935) estimated that $10,000 to $20,000 worth of gold (500 to 1,000 ounces) were produced. 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 | (-145.406773251841, 61.3152001637046) |
|---|---|
| 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 | An open cut and adit with about 125 feet of underground workings developed this mine. A small mill was installed in 1918; oxidized ore was amalgamated in an arrastre on site or shipped to the Cliff mine (VA107) for milling. |
|---|---|
| Indication of production | Yes; small |
| Production notes | Moffit (1935) estimated that $10,000 to $20,000 worth of gold (500 to 1,000 ounces) were produced. |
| MRDS Number | A011485 |
|---|---|
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 |