Bonanza Creek; Little Eldorado Creek; Skookum Creek; Coarse Money Creek; Snow Gulch Mine, Chisana District, Valdez-Cordova Borough, Alaska, USA
|Latitude & Longitude (WGS84):||62° 6' 8'' North , 141° 49' 44'' West|
|Latitude & Longitude (decimal):||62.10222,-141.82889|
|Köppen climate type:||ET : Tundra|
The mine is in the Wrangell-St. Elias National Preserve.
Location: Bonanza Creek was placer mined for about 2.3 miles of its length above the mouth of Canyon Creek. Tributaries that were placer mined on the north side of this part of Bonanza Creek, include Skookum Creek, Little Eldorado Creek, Snow Gulch, and Coarse Money Creek. These creeks are included in this record and the map site is arbitrarily plotted at the mouth of Little Eldorado Creek on Bonanza Creek. The site is in the NE1/4 of section 25, T. 4 N., R. 19 E. of the Copper River Meridian. This is locality 65 of Richter and others (1975) and National Park Service locality WRST-62 (unpublished data). Cobb and Richter (1980) included this mine under the name 'Bonanza Cr.'. It is accurately located.
Geology: Bonanza Creek was placer mined for about 2.3 miles of its length above the mouth of Canyon Creek. Tributaries that were also placer mined on the north side of this part of Bonanza Creek, include Skookum Creek, Little Eldorado Creek, Snow Gulch, and Coarse Money Creek were also placer mined (Capps, 1915; Capps 1916; Moffit, 1954; Richter and Jones, 1973). The placers along Bonanza Creek were in the active stream channel and in various bench deposits including abandoned channels over 100 feet above the present stream. The placer concentrates included cinnabar, native copper, galena, molybdenite, and native silver. Much of the gold in the present stream, where gravels are 2 to 12 feet thick, was concentrated on and within the top 1 to 2.5 feet of fractured bedrock. The overburden deposits, commonly frozen, could be over 50 feet thick on the benches (Moffit, 1943). Some of the gold may have been derived from reworking of Tertiary or Quaternary gravels like those exposed on the summit of Gold Hill (Richter and Jones, 1973). However, the mineralogical complexity of the placer concentrates suggests that this is not the only source. The tributaries and upper reaches of Bonanza Creek also rework various younger Quaternary surficial deposits that could be more locally derived. Bedrock exposed along Bonanza Creek and its tributaries is mostly Cretaceous volcanic and volcaniclastic rock, but Jurassic or Cretaceous siliciclastic rocks are present in its headwaters. Cretaceous or Tertiary dikes or small intrusive bodies are locally present. This area is about 2 miles east of Gold Hill, where the Chisana pluton intrudes Cretaceous volcanic and volcaniclastic rocks. This placer is one of several developed within or peripheral to the pluton (Richter and Jones, 1973; Richter and others, 1975). About 50,000 ounces of gold were recovered from placers in the Chisana area (Richter and others, 1975). Most of this production was from this site and Gold Run (NB077) and about half was produced between between 1913 and 1915; some mining continued in the area up to the 1970s.
Workings: Bonanza Creek was placer mined over about 2.3 miles of its length above the mouth of Canyon Creek. Tributaries that were also mined on the north side of this part of Bonanza Creek, include Skookum Creek, Little Eldorado Creek, Snow Gulch, and Coarse Money Creek were also placer mined. The bench gravels were frozen and an attempt was made to drift mine these deposits. An 85-foot deep shaft and 25-foot long drift were dug, but no paystreak was found.
Production: Assuming a price of $20.00 per ounce, about 50,000 ounces of gold were recovered from placers in the Chisana area (Richter and others, 1975). Most of this production was from the Gold Run (NB077) and Bonanza Creek (this site) drainages and about half was produced between 1913 and 1915. Some mining continued in the area up to the 1970s.
Commodities (Major) - Ag, Au; (Minor) - Cu, Hg, Mo, Pb
Development Status: Yes; small
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a)
6 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
66 - 145 Ma
|Igneous: extrusive; Extrusive: intermediate|
Age: Cretaceous (66 - 145 Ma)
Description: Okhotsk, Bering Sea, Pacific Alaska, Alaska Range
Comments: Orogen, magmatic arc/suite; Wilson & Hults, unpublished compilation, 2007-08
Reference: J.C. Harrison, M.R. St-Onge, O.V. Petrov, S.I. Strelnikov, B.G. Lopatin, F.H. Wilson, S. Tella, D. Paul, T. Lynds, S.P. Shokalsky, C.K. Hults, S. Bergman, H.F. Jepsen, and A. Solli. Geological map of the Arctic. doi:10.4095/287868. Geological Survey of Canada Map 2159A. 
|Late Jurassic - Early Cretaceous|
|Volcanic rocks of the Gravina-Nutzotin belt|
Age: Late Jurassic (145 Ma)
Description: Subaqueous and subaerial volcanic and volcaniclastic rocks; Upper Part: primarily andesite, basaltic andesite flows, fragmental volcanic rocks, subordinate porphyritic andesite, thin-bedded conglomerate, grit, sandstone, and tuff. Lower Part: fragmental volcanic rocks, dacite to andesite porphyritic flows, volcanic sandstone and siltstone, argillite, graywacke, conglomerate, and a tuffaceous mudstone
Reference: Wilson, F.H., Hults, C.P., Mull, C.G, and Karl, S.M. (compilers). Geologic map of Alaska. doi: 10.3133/sim3340. U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196.