| Main commodities | Au |
|---|---|
| Ore minerals | arsenopyrite; gold; pyrite |
| Gangue minerals | carbonate minerals; chlorite; quartz; white mica |
| Quadrangle map, 1:250,000-scale | VA |
|---|---|
| Quadrangle map, 1:63,360-scale | B-5 |
| Latitude | 61.4322 |
| Longitude | -145.5076 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | This prospect is on the south side of lower Hurtle Creek, about 1 mile southeast of the mouth of Hurtle Creek on Tonsina Lake. It is at an elevation of about 2,400 feet in the SW1/4 section 13, T. 5 S., R. 2 W., of the Copper River Meridian. This prospect is probably located to within one-half mile. It is locality 95 of Winkler and others (1981 [OFR 80-892-B]). |
Geologic descriptionLode gold claims were staked here and were active from 1953 to 1972 (U.S. Bureau of Mines, 1980; Winklerand others, 1981 [OFR 80-892-B]). These deposits are probably gold-bearing quartz veins cutting metaflysch of the Valdez Group and 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 | (-145.50969940658, 61.4316942604882) |
|---|---|
| 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 | At least some surface prospecting has occurred at this prospect. |
|---|---|
| Indication of production | Undetermined |
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.
U.S. Bureau of Mines, 1980, Valdez 1:250,000 quadrangle map overlay showing mineral deposit locations, principal minerals, and number and type of claims: U.S. Bureau of Mines Open-File Report, August 1980.
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| Reporters | Travis L. Hudson |
|---|---|
| Last report date | 12/14/2001 |