|Quadrangle map, 1:250,000-scale||HU|
|Quadrangle map, 1:63,360-scale||A-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This occurrence is about 4 miles west of Hogatza and 2.3 miles northeast of the summit of Caribou Mountain. It is at an elevation of about 2,500 feet, in the SW1/4 of section 10, T. 9 N., R. 14 E. of the Kateel River Meridian. The location is accurate within 1 mile.|
This occurrence consists of radioactive and rare-earth accessory minerals in the border phases of the Cretaceous, Zane Hills pluton. Miller and Ferrians (l968) note that the quartz monzonitic to monzonitic border phase of the generally granodioritic Zane Hills pluton is 5 to 10 times more radioactive than background. They also noted that large K-feldspar phenocrysts, with tourmaline-bearing aplite dikes, are common in the border phase. A sample of porphyritic quartz monzonite from the border phase contains 20 ppm uranium. Miller and Elliot (1977) subsequently described the border phase rocks as monzonite, syenite, quartz monzonite and hybrid diorite. They propose an intrusive contact between the border phase and the main Zane Hills granodiorite, and suggest that the monzonitic border phase is younger. Samples of border-phase rocks contain 11 to 99 ppm uranium, and 46 to 269 ppm thorium. The uranium and thorium are concentrated in grains of uranothorianite, thorite, betafite, allanite, zircon, and sphene, which occur as disseminated accessory minerals in the monzonite. They found no vein-type mineralization and concluded that the border phase intrusives are enriched in U and Th.Sphene from two samples gneissic monzonite (presumed to be border phase rocks ) from the Zane Hills pluton a few kilometers upstream of the Hogatza placer deposit (HU014) contains from 27,890 to 39,180 ppm REE, including 380 to 760 ppm thorium (Staatz and others, 1977). Later investigations, however, indicate that the border phase rocks contain no unusual concentrations of REE (Barker, 1991).
|Geologic map unit||(-155.882152478665, 66.1913374739319)|
|Mineral deposit model||Felsic plutonic U-REE (Nokleberg and others, 1987)|
|Age of mineralization||K-Ar age dating of hornblende from the monzonite at the south end of the Zane Hills pluton gives an age of 81.9 Ma (Miller and others, 1966).|
|Alteration of deposit||At the contact between border-phase, monzonite-quartz monzonite and the core granodiorite, the granodiorite is, at least locally, strongly altered to a bleached, fine-grained, sericitic rock. Although the alteration diminishes in intensity away from the contact, all of the original biotite is completely altered to sericite. The granodiorite exhibits cataclastic texture near the contact.|
|Workings or exploration||Only surface sampling.|
|Indication of production||None|
Additional commentsSee also HU016.
Barker, J.C., 1991, Investigations of rare-earth and associated elements, Zane Hills pluton, northwestern Alaska: U.S. Bureau of Mines Open-File Report 36-91, 33 p.
Eakins, G.R., and Forbes, R.B., 1976, Investigation of Alaska's uranium potential: Alaska Division of Geological and Geophysical Surveys Special Report 12, 372 p., 5 sheets, scale 1:1,000,000.
Eakins, G.R., Jones, B.K. and Forbes, R.B., 1977, Investigation of Alaska's uranium potential: Alaska Division of Geological and Geophysical Surveys Open-File Report 109, 213 p., 10 sheets, scale 1:40,000.
Jones, Brian, 1977, Uranium-thorium bearing rocks of western Alaska: Fairbanks, University of Alaska, M.S. thesis, 80 p.
Miller, T.P., 1976, Hardrock uranium potential of Alaska: U.S. Geological Survey Open-File Report 76-246, 5 p.
Miller, T.P., and Bunker, C.M., 1975, Uranium, thorium and potassium analyses of selected plutonic rocks from west-central Alaska: U.S. Geological Survey Open-File Report 75-216, 3 p.
Miller, T.P., and Elliott, R.L., 1977, Progress report on uranium investigations in the Zane Hills area, west-central Alaska: U.S. Geological Survey Open-File Report 77-428, 12 p.
Miller, T.P., and Ferrians, O.J., Jr., 1968, Suggested areas for prospecting in the central Koyukuk River region, Alaska: U.S. Geological Survey Circular 570, 12 p.
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.
Nokleberg, W.J., Bundtzen, T.K., Dawson, K.M., Eremin, R.A., Goryachev, N.A., Koch, R.D., Ratkin, V.V, Rozenblum, I.S., Shpikerman, V.I., Frolov, Y.F., Gorodinsky, M.E., Melnikov, V.D., Diggles, M.F., Ognyanov, N.V., Petrachenko, E.D., Petrochenko, R.I., Pozdeev, A.I., Ross, K.V., Wood, D.H., Grybeck, D., Khanchuck, A.I., Kovbas, L.I., Nekrasov, I.Y., and Sidorov, A.A., 1996, Significant metalliferous and selected non-metalliferous lode mineral deposits and placer districts, and for metallogenesis of the Russian Far East, Alaska, and the Canadian Cordillera: U.S. Geological Survey Open-File Report 96-513-B, 385 p.; U.S. Geological Survey Open-File Report 96-513-B, 385 p. (CD-ROM format).
Staatz, M.H., and Miller, T.P., 1976, Uranium and thorium content of radioactive phases of the Zane Hills pluton, in Cobb, E.H., ed., The U.S. Geological Survey in Alaska--Accomplishments during 1975: U.S. Geological Survey Circular 733, p. 39-41.
|Reporters||J.M. Britton (Anchorage)|
|Last report date||8/1/2002|