|Quadrangle map, 1:250,000-scale||DN|
|Quadrangle map, 1:63,360-scale||C-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Bosart mine (Cobb, 1980 [OFR 80-363]) is at an elevation of about 2700 feet on the west wall of the west fork of Twentytwo Gulch. It is in the SW1/4 SW1/4 of section 32, T. 15 S., R. 17 W., Fairbanks Meridian. The location is accurate within 500 feet. The mine site corresponds to number 14 of Cobb (1972 [MF 366]), 36 of Bundtzen, Smith, and Tosdal (1976), 42 of Bundtzen (1981), 116 of Hawley and Associates (1978), and 48 of Thornsberry, McKee, and Salisbury (1984).|
The country rocks at the Bosart mine are interlayered quartz-feldspar schist and micaceous quartz schist of the Precambrian Birch Creek Schist. Greenschist is also present locally and garnet amphibolite underlies a prominent ridge about 75 feet west of the mine workings (Bundtzen, 1981, pl. 3; Thornsberry, McKee, and Salisbury, 1984, v. 2, occurrence 48).
The deposit is a thin, sulfide-rich vein that strikes N 50 E, and dips 70-80 NW. The vein contains arsenopyrite, pyrite, chalcopyrite, galena, sphalerite, tetrahedrite, and polybasite (Wells, 1933, p. 370-371; Bundtzen, 1981). The polybasite occurs mainly in high-grade, silver-lead ore. Some of the galena may be oxidized to cerussite.
The sulfide-rich ore contains silver assaying from a few ounces to about 40 ounces per ton; some veins assayed more than 230 ounces of silver per ton. Twenty tons of hand-picked ore shipped in 1980 averaged 0.328 ounce of gold and 78.22 ounces of silver per ton; some ore contained more than 1000 ounces of silver per ton.The Bosart vein projects towards the Florence vein (DN082), which is about 0.75 mile to the southwest.
|Geologic map unit||(, )|
|Mineral deposit model||Polymetallic vein (Cox and Singer, 1986; model 22c).|
|Mineral deposit model number||22c|
|Age of mineralization||The deposit is assumed to be Eocene (see record DN091).|
|Alteration of deposit||Possible oxidation of lead mineral.|
|Workings or exploration||The vein was developed by Otto Bosart before 1931(Wells, 1933). It was prospected in the 1960s and 1970s by Arley Taylor and Jim Dale. In 1980, a small quantity of ore was mined and shipped. Mill ore was left in place.|
|Indication of production||Yes; small|
|Reserve estimates||About 75 tons of low-to medium-grade gold-silver ore was not mined; exploration probably would develop more reserves at the property.|
|Production notes||The mine produced at least 20 tons of high-grade ore in 1980. This ore contained as much as 6.56 ounces of gold and 1564.4 ounces of silver per ton. About 75 tons of mill-grade ore was left in the walls of the high-grade vein, and a Harz-type jig plant was on the property in 1983. Probably no mining occurred after 1983 (Thornsberry, McKee, and Salisbury, 1984, v. 2).|
Additional commentsThe Bosart mine is in Denal National Park and Preserve.
Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p.
Bundtzen, T.K., Smith, T.E., and Tosdal, R.M., 1976, Progress report--Geology and mineral deposits of the Kantishna Hills: Alaska Division of Geological and Geophysical Surveys Open-File Report AOF-98, 80 p., 2 sheets, scale 1:63,360.
Cobb, E. H., 1972, Metallic mineral resources map of the Mount McKinley quadrangle, Alaska: U. S. Geological Survey Miscellaneous Field Studies Map MF-366, 1 sheet, scale 1:250,000.
Cobb, E.H., 1980, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount McKinley quadrangle, Alaska: U. S. Geological Survey Open-File Report 80-363, 150 p.
Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p.
Hawley, C. C. and Associates, Inc, 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska: U. S. Bureau of Mines Open-File Report 24-78, 275 p. (paged by sections).
Thornsberry, V. V., McKee, C. J., and Salisbury, W. G., eds, 1984, 1983 Mineral Resource Studies: Kantishna Hills and Dunkle Mine Areas, Denali National Park and Preserve, Alaska: U. S. Bureau of Mines Open-File Report 129-84. 3 Volumes: v. 1, Text; v. 2, Appendices; v. 3, Maps. Prepared by Salisbury & Dietz, Inc., Spokane, WA.
|Last report date||1/12/2001|