|Quadrangle map, 1:250,000-scale||CI|
|Quadrangle map, 1:63,360-scale||B-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The location is approximately 1500 ft NE of the Ketchem Dome summit at the site of the Ketchem Dome tin prospect trench reported in Dahlin and others (1987). The Ketchem Dome tin prospect is located approximately 5 miles southwest of Circle Hot Springs. The prospect lies 1 mile to the west of, and approximately 1300 ft above, a gravel road that leads north to the Steese Highway.|
Geologic descriptionThe following information is taken from a Bureau of Mines report by Dahlin and others (1987). The tin mineralization on Ketchem Dome consists of cassiterite which occurs as grains disseminated in a greisen matrix. A bulk sample from the largest and best-developed greisen vein exposed at Ketchem Dome contained 0.51 percent Sn. Concentration of the cassiterite by gravity table methods resulted in a product that contained 56 percent cassiterite at a grade of 41.4 percent Sn. The tin-bearing greisen vein mineralization near Ketchem Dome cuts a leucocratic, seriate phase of the Circle Hot Springs biotite granite pluton near its contact with hornfelsed sedimentary rocks. The pluton has been K-Ar dated at 60.5 +/- 1.8 m.a. (Wilson and Shew, 1981). Four hand-excavated trenches expose the greisen near Ketchem Dome. The greisen is mineralogically zoned, with a selvage of muscovite-altered granite that grades into a core of dense, black, chlorite- and sericite-altered granite with traces of limonite after pyrite and veinlets of quartz. Purple fluorite occurs on fractures, and topaz is locally associated with more pervasive alteration. The mineralization exposed at Ketchem Dome is typical of greisen found elsewhere in the area. One sample assayed greater than 1,000 ppm Sn (Dave Menzie, USGS, field notes, 1984).
|Geologic map unit||(-144.789445298552, 65.4666373518365)|
|Mineral deposit model||Sn greisen deposit (Cox and Singer, 1986; model 15c)|
|Mineral deposit model number||15c|
|Age of mineralization||The tin-bearing greisen vein mineralization near Ketchem Dome cuts a biotite granite pluton near its contact with hornfelsed sedimentary rocks. The pluton has been K-Ar dated at 60.5 +/- 1.8 m.a. (Wilson and Shew, 1981).|
|Alteration of deposit||Chloritic, quartz-white mica, topaz, fluorite.|
|Workings or exploration||Five pits in area, excavated by Resource Associates of Alaska in 1983.|
|Indication of production||None|
Dahlin, D.C., Brown, L.L., and Warner J.D., 1987, Characterization of Ketchem Dome tin prospect, east-central Alaska: U.S. Bureau of Mines Report of Investigation 9145, 11 p.
Foster, H.L., Laird, Jo, Keith T.E.C., Cushing, G.W., and Menzie, W.D., 1983, Preliminary geologic map of the Circle quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-170-A, 32 p., 1 sheet, scale 1:250,000.
Menzie, W.D., Foster, H.L., Tripp, R.B., and Yeend, W.E., 1983, Mineral resource assessment of the Circle quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-170-B, 61 p., 1 sheet, 1:250,000.
Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000.
Wilkinson, Katy, 1987, Geology of a subarctic, tin-bearing batholith, Circle Hot Springs, Alaska: University of Alaska, Mineral Industry Research Laboratory Report 74, 70 p.
|Reporters||C.J. Freeman, J.R. Guidetti Schaefer, A.S. Clements (Avalon Development Corporation)|
|Last report date||9/9/1998|