| Main commodities | Au |
|---|---|
| Other commodities | Cu; Pb; Zn |
| Ore minerals | arsenopyrite; chalcopyrite; galena; gold; limonite; pyrite; pyrrhotite; sphalerite |
| Gangue minerals | carbonate minerals; chlorite; quartz; white mica |
| Quadrangle map, 1:250,000-scale | VA |
|---|---|
| Quadrangle map, 1:63,360-scale | A-7 |
| Latitude | 61.2166 |
| Longitude | -146.2944 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | This mine is on the south side of Glacier Creek. It is marked as the Giant mine on the USGS Valdez A-7 topographic map (1996) and located with an adit symbol. It is locality 29 of Cobb and Matson (1972) and locality 23 of Winkler and others (1981 [OFR 80-892-B]). |
Geologic descriptionGold-bearing quartz veins cut metaflysch of the Valdez Group at this locality. The veins, which are from an inch to 4 feet in thickness, are semi-parallel to the foliation in the country rock (Johnson, 1915). They contain free gold, carbonate, chalcopyrite, pyrite, galena, sphalerite, and pyrrhotite (Johnson, 1915; Smith, 1937). Two grab samples contained 0.364 and 1.35 ounces of gold per ton and 1.4 and 5.8 ounces of silver per ton (Jansons and others, 1984). About 120 feet of underground workings and some surface stripping had been completed by 1914; several tons of ore gathered from outcrop were milled in 1914 (Johnson, 1915). Work on these deposits continued intermittently to 1937 (Cobb, 197 [OFR 79-1241]), and workings eventually included a vertical shaft, three inclined shafts, an underground mill, and a 165-foot-long adit (Smith, 1937; Jansons and others, 1984). 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 | (-146.296455054931, 61.2160821715428) |
|---|---|
| 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 | About 120 feet of underground workings and some surface stripping had been completed by 1914; several tons of ore gathered from outcrop were milled in 1914 (Johnson, 1915). Work on these deposits continued intermittently to 1937 (Cobb, 1979 [OFR 79-1241]); the workings eventually included a vertical shaft, three inclined shafts, an underground mill, and a 165-foot-long adit (Smith, 1937; Jonsons and others, 1984). |
|---|---|
| Indication of production | Yes; small |
| Production notes | The reported production from this property is 367 ounces of gold and 152 ounces of silver (Jansons and others, 1984). |
| MRDS Number | A011469 |
|---|---|
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 |