|Quadrangle map, 1:250,000-scale||NB|
|Quadrangle map, 1:63,360-scale||A-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This placer gold mine is on Big Eldorado Creek, a drainage on the west flank of Gold Hill. The site is the approximate midpoint of the 2,500 feet of placer workings mapped by Richter and Jones (1973 ). It is in the SW1/4 of section 21, T. 4 N., R. 19 E. of the Copper River Meridian. This is locality 64 of Richter and others (1975) and it is included in National Park Service locality WRST-59 (unpublished data). Cobb and Richter (1980) included this mine under the name 'Big Eldorado Cr.' It is accurately located.|
Geologic descriptionCoarse, bright and rough gold was mined from this placer deposit on the northwest flank of Gold Hill as early as 1915 (Capps, 1915; 1916). The gravels were up to 10 feet thick but two placer workings described by Capps (1915) had dimensions of 600 feet by 12 feet in 6 feet of gravel, and 250 feet by 30 feet in 2 feet of gravel. Placer gold was also mined from the top 2 to 4 feet of fractured bedrock and some of the ground was frozen. This placer is unique in the area because it is probably a primary concentration of placer gold. All other placers in the district are probably derived from reworked Quaternary deposits (Richter and others, 1975). Bedrock in Big Eldorado Creek varies from clinopyroxene diorite to monzonite of the mid-Cretaceous Chisana pluton (Richter and Jones, 1973; Richter, Lanphere, and Matson, 1975).
|Geologic map unit||(-141.951627255995, 62.1092337015825)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||Holocene.|
|Workings or exploration||Surface placer mine workings are present along about 3,000 feet of Big Eldorado Creek (Richter and Jones, 1973).|
|Indication of production||Yes; small|
|Production notes||Assuming a price of $20.00 per ounce, about 50,000 ounces of gold were produced from placers in the Chisana area (Richter and others, 1975). Most of this production was from the Gold Run (NB077) and Bonanza Creek (NB079) drainages, and about half was produced between 1913 and 1915; some mining continued in the area up to the 1970s.|
Additional commentsThe mine is in the Wrangell-St. Elias National Preserve.
Capps, S.R., 1915, Mineral resources of the Chisana-White River district: U.S. Geological Survey Bulletin 622-F, p. 189-228.
Capps, S.R., 1916, The Chisana-White River district, Alaska: U.S. Geological Survey Bulletin 630, 130 p.
Cobb, E.H., and Richter, D.H., 1980, Summaries of data on and list of references to metallic and selected nonmetallic mineral deposits in the Nabesna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-927, 117 p.
Richter, D.H., and Jones, D.L., 1973, Reconnaissance geologic map of the Nabesna A-2 quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-749, 1 sheet, scale 1:63,360.
Richter, D.H., Lanphere, M.A., and Matson, N.A., Jr., 1975, Granite plutonism and metamorphism, eeastern Alaska Range, Alaska: Geological Society of American Bulletin, v. 86, p. 819-820.
|Reporters||Travis L. Hudson (Applied Geology)|
|Last report date||11/24/2002|