|Quadrangle map, 1:250,000-scale||MM|
|Quadrangle map, 1:63,360-scale||C-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Lower Caribou Creek (Cobb, 1980 [OFR 80-363]) is the part of Caribou Creek below the Kantishna Hills. The lower Caribou Creek placer deposit is about 3 miles long. It extends from the NW1/4 of section 7, T. 15 S., R. 17 W., Fairbank Meridian, to the midpoint of sections 31 and 36 on the R. 17 W.-18 W. township line. The location marks the north limit of placer tailings shown on the 1954 (rev. 1978) edition of the Mt. McKinley C-2 quadrangle topographic map. It approximately coincides with number 47 of Cobb (1972 [MF 366]), placer resource block C-2 of Thornsberry, McKee, and Salisbury (1984, fig. K-3), and the mined area shown by Hawley and Associates (1978).|
Lower Caribou Creek has a gradient of about 150 feet per mile. It flows through a broad alluvial valley cut into bedrock of the Birch Creek Schist (Levell, 1984, v. 1 and 2; Bundtzen, 1981). The broad terrace on the east side of lower Caribou Creek is called the Lee bench. The lower Caribou Creek placer deposit consists of 4 to 7 feet of subrounded to rounded gravel on top of weathered, clayey, bedrock. The lowest 1 to 2 feet of gravel is weakly cemented. The gold was mainly in the gravel, but about 1/2 foot of bedrock was auriferous and was mined with the gravel. Most of the gold was fine and flaky, a little was nuggety, and its fineness was about 680. The gold was weakly to moderately stained with iron and manganese oxides. Garnet and magnetite were abundant in the concentrate. Grade, calculated from production, was about 0.027 ounce (0.019 fine ounce) of gold per cubic yard (Levell, 1984, v. 2, operation 6).The nature of the Lee bench placer is uncertain, as most of it has not been tested. The deposit mainly is on schist bedrock, and consists of 4 to 10 feet of gravel overlain by 2 to 3 feet of frozen muck (Levell, 1984, v. 2). At an exposure about 1/2 mile downstream from the schist-floored deposit, 10 to 15 feet of gravel lies on false bedrock of quartz-rich, Tertiary(?) sand. Spoils from nearby pits include blue clay that is possibly Tertiary lake sediment. The average grade of the Lee bench deposit, calculated from ground mined and gold recovered in 1975, is 0.026 ounce (0.019 fine ounce) of gold per cubic yard.
|Geologic map unit||(-150.938300020093, 63.6570940063852)|
|Mineral deposit model||Au-PGE placer (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||Holocene and late Pleistocene; some deposits may be as old as late Tertiary.|
|Workings or exploration||More than a mile of lower Caribou Creek was mined prior to 1951-52, probably mainly by dragline in about 1940. At least one operation worked the lower Lee bench in 1975 (Levell, 1984, v. 2; Bundtzen, Tosdal, and Smith, 1976). The alluvial deposit in and near the modern valley was mined in 1983 and probably 1984.|
|Indication of production||Yes; small|
|Reserve estimates||Resource block C-2 (Levell, 1984) contains about 840,000 cubic yards of alluvium on claimed ground (1983) in or adjacent to modern lower Caribou Creek. The gold resource at the calculated grade of 0.019 fine ounce of gold per cubic yard is 15,960 ounces. There is a much larger, but less quantified, resource on the Lee bench. The estimated volume of claimed (1983) gravel in the bench deposits is 4,300,000 cubic yards. Using the grade calculated from 1975 production from the bench (0.019 fine ounce of gold per cubic yard), the resource is about 81,700 ounces of gold.|
|Production notes||Total gold production is uncertain. An operator in 1975 recovered about 70.5 ounces. An efficient 1983 operation had recovered more than 1000 ounces before the end of August, and was in production when visited by Levell (Levell, 1984, v. 2). Based on the grade of mined material, and on the extent of the mining, the lower Caribou placer deposit has probably produced at least 5000 ounces of gold.|
Additional commentsCaribou Creek is in Denali 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).
Levell, J. H., 1984, Appendix A, Placer, in 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, Vol. 2, p. 1-219.
Levell, J. H., 1984, Placer deposits, in 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, Vol. 1, p. 48-112.
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||4/19/2001|