|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||
This site represents two prospects. The upper McGonogill prospect (Cobb, 1980 [OFR 80-363]) is at an elevation of about 3400 feet at the head of the north fork of upper Glacier Creek, a fork locally called McGonogill Gulch. The prospect is about on the north border of the SW1/4 SW1/4 section 35, T. 15 S., R. 17 W., Fairbanks Meridian. The lower McGonogill (sometimes spelled McGonagall) prospect is about a half-mile to the west, at an elevation of about 2700 feet (Davis, 1923). It is in the SE1/4 section 34, T. 15 S., R. 17 W. The location is for the upper prospect and is accurate within 300 feet.The upper McGonogill prospect corresponds to number 13 of Cobb (1972 [MF 366]), 44 of Bundtzen, Smith, and Tosdal (1976), 51 of Bundtzen (1981), 64 of Thornsberry, McKee, and Salisbury (1984), and 218 of Hawley and Associates (1978). The lower prospect has not been cited in published reports since about 1970.
The country rocks in the area of the McGonogill prospects are schists correlated with the upper Precambrian Birch Creek Schist (Bundtzen, 1981). Wells (1933, p. 372) reported that an adit at the upper prospect was driven in graphitic schist. Thornsberry, McKee, and Salisbury (1984, v. 2, occurrence 64) reported that the country rock is mainly micaceous quartzite that strikes NNW and dips SW at a low angle.
The upper McGonogill deposit is a mineralized shear zone as much as 8 feet thick. It contains polymetallic quartz-sulfide veins, strikes about N 58 E, and dips 34 SW (Wells, 1933, p. 372). The quartz contains disseminated and veinlet pyrite and arsenopyrite, and smaller amounts of galena, stibnite, chalcopyrite, boulangerite, and sphalerite. The sulfides locally are oxidized to limonite, scorodite, and stibiconite (Bundtzen, 1981; Thornsberry, McKee, and Salisbury, 1984, v. 2). The deposit was explored by a 40-foot adit. Davis (1923) reported that the vein exposed at the face of the adit assayed about 0.6 ounce of gold per ton and 63 ounces of silver per ton. Typical ore is much lower in grade. Bundtzen (1981) reported that quartz vein material containing abundant arsenopyrite and rarer boulangerite and galena assayed as much as 2. 2 percent lead and 8.51 percent arsenic, but only about 0.1 ounce of gold per ton and 1 ounce of silver per ton. Other veins in the area include one that crops out northeast of the workings. It assayed 3.5 percent lead, 1.5 percent zinc, 0.13 ounce of gold per ton, 3 ounces of silver per ton, 2800 ppm antimony, and 89 ppm mercury (Hawley and Associates, 1978, sample 218).At the lower McGonogill prospect, a quartz vein containing free gold is offset by a shear zone impregnated with tetrahedrite, stibnite, and chalcopyrite (Davis, 1923, p. 131-132). Samples of the mineralized shear zone assayed as much as 52 ounces of silver per ton.
|Geologic map unit||(, )|
|Mineral deposit model||Polymetallic veins and low-sulfide Au-quartz veins (Cox and Singer, 1986; models 22c and 36a).|
|Mineral deposit model number||22c, 36a|
|Age of mineralization||The deposits are assumed to be Eocene (see record DN091). At the lower McGonogill prospect, a polymetallic, mineralized shear zone postdates a low-sulfide gold-quartz vein.|
|Alteration of deposit||Silicification and sulfidization of shear zones. Oxidation of iron, arsenic, and antimony minerals.|
|Workings or exploration||The McGonogill deposits were discovered and prospected before 1916 (Capps, 1919, p. 100). By about 1930, the upper deposit was explored by a 40-foot tunnel (Davis, 1923; Wells, 1933). Apparently not much work was done after that.|
|Indication of production||Yes; small|
|Production notes||About 1 ton of gold-bearing quartz was shipped for testing purposes from the lower McGonogill prospect.|
Additional commentsThe upper and lower McGonogill prospects are 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.
Davis, J. A., 1923, The Kantishna region, Alaska, in Stewart, B. D., Annual Report of the Mine Inspector to the Governor of Alaska, 1922: Alaska Division of Geological and Geophysical Surveys AR-1922.
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||5/2/2001|