|Quadrangle map, 1:250,000-scale||MC|
|Quadrangle map, 1:63,360-scale||B-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This mine is on the north valley wall of lower Twaharpies Glacier. It is at an elevation of about 3,800 feet, 500 feet from of the glacier, and 5,800 feet southwest of peak 8235. The site is 700 feet south of the center of section 30, T. 5 S., R. 18 E. of the Copper River Meridian. This is locality 62 of MacKevett (1976) and it is accurately located. Cobb and MacKevett (1980) include this prospect under the name 'Erikson (and Madden)'. The mine is shown on the McCarthy B-4 topographic map (1994 edition).|
Geologic descriptionThis deposit consists of native copper, tenorite, cuprite, and minor amounts of chalcocite and malachite in irregular masses, thin veins, and disseminated grains in the upper parts of Triassic Nikolai Greenstone that consists of amygdaloidal lava flows. To a lesser extent, the ore minerals occurs as fillings in amygdules or associated with quartz-epidote veins in the flows (Miller, 1946; MacKevett, 1976). Most of the native copper occurs as small grains but masses up to 50 or 60 pounds have been found. Samples of the mineralization contained up to 70 parts per million (ppm) silver and more than 20,000 ppm copper (MacKevett and Smith, 1968, samples 141-146). The mine was developed by about 300 feet of underground workings and a little copper was produced in 1917 (MacKevett, 1976). Copper mineralization is common in Nikolai Greenstone and is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic to Early Cretaceous (MacKevett and others, 1997).
|Geologic map unit||(-142.25745138086, 61.4075833355429)|
|Mineral deposit model||Basaltic Cu (Cox and Singer, 1986; model 23)|
|Mineral deposit model number||23|
|Age of mineralization||Cretaceous? Copper mineralization is common in Nikolai Greenstone and is thought to have accompanied regional deformation and low-grade metamorphism in the Late Jurassic to Early Cretaceous (MacKevett and others, 1997).|
|Alteration of deposit||Quartz-epidote veining and replacement.|
|Workings or exploration||The deposit was developed on 3 levels by about 300 feet of underground workings accessed from two adits.|
|Indication of production||Yes; small|
|Production notes||A small amount of copper was produced in 1917.|
Additional commentsThe locality is in the Wrangell-Saint Elias National Park and Preserve.
Cobb, E.H., and MacKevett, E.M., Jr., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the McCarthy quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-885, 156 p.
MacKevett, E.M., Jr., 1976, Mineral deposits and occurrences in the McCarthy quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-773-B, 2 sheets, scale 1:250,000.
MacKevett, E.M., Jr., and Smith, J.G., 1968, Distribution of gold, copper, and some other metals in the McCarthy B-4 and B-5 quadrangles, Alaska: U.S. Geological Survey Circular 604, 25 p.
MacKevett, E.M., Jr., Cox, D.P., Potter, R.W., III, and Silberman, M.L., 1997, Kennecott-type deposits in the Wrangell Mountains, Alaska--High-grade copper ores near a basalt-limestone contact, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 66-89.
|Reporters||Travis L. Hudson (Applied Geology, Inc.)|
|Last report date||1/12/2003|