| 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 | B-4 |
| Latitude | 61.3794 |
| Longitude | -145.438 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | This mine is on the east side of an unnamed south tributary to Hurtle Creek (Moffit, 1935, plate 1) 1.2 miles southwest of elevation (peak) 5640. It is at an elevation of about 3,900 feet in the NE1/4 section 5, T. 6 S., R. 1 W., of the Copper River Meridian. This mine is probably located to within one-half mile. It is locality 49 of Cobb and Matson (1972) and included in locality 40 of Winkler and others (1981 [OFR 80-892-B]). |
Geologic descriptionEn echelon quartz veins as much as 1.5 feet thick that cut metaflysch of the Valdez Group contain gold, galena, arsenopyrite, sphalerite, and chalcopyrite (Moffit, 1918; 1935). Tertiary felsic dikes locally cross-cut the veins and metaflysch. The veins strike northerly and dip 60 degrees east. They have been traced on the surface in open cuts for about 300 feet and explored underground by a short shaft and about 200 feet of adit and short drifts (Moffit, 1918, 1935). 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 | (-145.44008934657, 61.3788956891235) |
|---|---|
| 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 | Veins at this prospect have been traced on the surface in open cuts for about 300 feet and explored underground by a short shaft and about 200 feet of adit and short drifts (Moffit, 1918, 1935). |
|---|---|
| Indication of production | Yes; small |
| MRDS Number | A011489 |
|---|---|
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.
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| Reporters | Travis L. Hudson |
| Last report date | 12/14/2001 |