| 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 | A-7 |
| Latitude | 61.0734 |
| Longitude | -146.4035 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | This prospect is on the west side of lower Sawmill Creek valley, about eight-tenths of a mile south of the shoreline near the Trans-Alaska oil pipeline terminal. It is at an elevation of about 1,200 feet in the SW1/4 section 24, T. 9 S., R. 7 W., of the Copper River Meridian. This prospect is approximately located, perhaps to within one-quarter mile. This is locality 77 of Winkler and others (1981 [OFR 80-892-B]). |
Geologic descriptionA 160-foot adit was driven in 1917 on gold-bearing quartz veins that cut metaflysch of the Valdez Group at this locality (Johnson, 1919). These veins 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 | (-146.405518865712, 61.0728743514467) |
|---|---|
| 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 | A 160-foot adit was reported to have been driven in 1917 on gold-bearing quartz veins that cut metaflysch of the Valdez Group at this locality (Johnson, 1919). These deposits may have been restaked as the Golden and Happy Sys claims in 1954 (Mulligan, 1974). |
|---|---|
| Indication of production | Undetermined |
| MRDS Number | A011535 |
|---|---|
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 |