Unnamed (Cobblestone River)

Occurrence in Alaska, United States with commodities Beryllium, Thorium, Uranium

Geologic information

Identification information

Deposit ID 10307911
Record type Site
Current site name Unnamed (Cobblestone River)

Geographic coordinates

Geographic coordinates: -165.46732, 64.97989 (WGS84)
Relative position The occurrence is on a steep ridge about 1 mile east of the Cobblestone River and about 3.3 miles north of Mosquito Pass. The occurrence is locality 114 of Hummel (1975). It is in the SE1/4 section 12, T. 6 S., R. 34 W., Kateel River Meridian at an elevation of about 2,200 feet. The occurrence is a pegmatite; it probably is located within about 1,000 feet, but may be representative of one or more pegmatite bodies that occur near this location.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Beryllium Primary
Thorium Primary
Uranium Primary

Materials information

Materials Type of material
Beryl Ore
Feldspar Gangue
Garnet Gangue
Quartz Gangue
Tourmaline Gangue

Nearby scientific data

(1) -165.46732, 64.97989

Comments on the geologic information

  • Geologic Description = This granite pegmatite is an isolated occurrence north of the Thompson Creek orthogneiss, and its age is uncertain. Granite pegmatites are abundant in the Kigluaik Mountains, and others may be present near this occurrence. The pegmatites are noticeably radioactive; radioactivity measured on the ground with a scintillometer is as much as 500 counts per second or 3 to 5 times common background (Hawley and Associates, 1978, Section IV). Tourmaline and garnet are common accessory minerals, and the more radioactive pegmatites commonly contain smoky quartz. Beryl occurs in some of the pegmatite, including a body described by Moffit (1913, p. 25) about 1 mile west of the mouth of North Star Creek (NM046). Some granite pegmatites are within the Thompson Creek orthogneiss or appear to be spatially associated with it, particularly on its south or hanging wall side (Hummel, 1962 [MF248]; Till, 1980). The Thompson Creek orthogneiss has been dated as latest Proterozoic (555 Ma, Amato and Wright, 1998) and some pegmatites may also be this age. However, metasedimentary rocks of the Kigluaik Mountains underwent granulite facies metamorphism and partial melting in the mid-Cretaceous, and some pegmatites are crosscutting to local structure and mid-Cretaceous in age (Throckmorton and Hummel, 1979; Till, 1983; Miller and Hudson, 1991; Hudson, 1994; Till and Dumoulin, 1994; Amato and others, 1994; Amato and Wright, 1997, 1998). The host rocks to this pegmatite are upper amphibolite facies metasedimentary rocks that are probably derived from Precambrian protolith (Sainsbury, 1972; Bunker and others, 1979; Till and Dumoulin, 1994). They are thought to have undergone regional high-pressure metamorphism along with many other rocks of Seward Peninsula in the Late Jurassic or Early Cretaceous (Sainsbury, Coleman, and Kachadoorian, 1970; Forbes and others, 1984; Thurston, 1985; Patrick, 1988; Patrick and Evans, 1989; Armstrong and others, 1986; Hannula and McWilliams, 1995). Higher temperature metamorphism overprinted these rocks in conjunction with regional extension, crustal melting, and magmatism in the mid-Cretaceous (Throckmorton and Hummel, 1979; Till, 1983; Evans and Patrick, 1987; Leiberman, 1988; Patrick and Leiberman, 1988; Miller and Hudson, 1991; Miller and others, 1992; Dumitru and others, 1995; Hannula and others, 1995; Hudson and Arth, 1983; Hudson, 1994; Amato and others, 1994; Amato and Wright, 1997, 1998). Uplift of the higher temperature metamorphic rocks took place in the mid- to Late Cretaceous and in the Eocene (Calvert, 1992; Dumitru and others, 1995).
  • Ore Material = unknown thorium- and uranium-bearing minerals
  • Age = Late Proterozoic or mid-Cretaceous; either the age of the Late Proterozoic Thompson Creek orthogneiss or mid-Cretaceous granulite facies metamorphism.

Economic information

Economic information about the deposit and operations

Development status Occurrence

Comments on exploration

  • Status = Probably inactive

Mining district

District name Nome

Comments on the workings information

  • Workings / Exploration = Reconnaissance uranium exploration including airborne radiometrics, stream sediment surveys, and ground traverses have been completed in the Kigluaik Mountains.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF NM021

Bibliographic references

  • Deposit

    Moffit, F.H., 1913, Geology of the Nome and Grand Central quadrangles, Alaska: U.S. Geological Survey Bulletin 533, 140 p.

  • Deposit

    Hummel, C.L., 1962, Preliminary geologic map of the Nome D-1 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-248, 1 sheet, scale 1:63,360.

  • Deposit

    Sainsbury, C.L., Coleman, R.G., and Kachadoorian, Reuben, 1970, Blueschist and related greenschist faces rocks of the Seward Peninsula, Alaska, in Geological Survey research 1970: U.S. Geological Survey Professional Paper 700-B, p. B33-B42.

  • Deposit

    Sainsbury, C.L., 1972, Geologic map of the Teller quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Map I-685, 4 p., 1 sheet, scale 1:250,000.

  • Deposit

    Hummel, C.L., 1975, Mineral deposits and occurrences, and associated altered rocks, in southwest Seward Peninsula, western Alaska: U.S. Geological Survey Open-File Report 75-2, 1 sheet, scale 1:125,000.

  • Deposit

    Hawley, C.C., and Associates, 1978, Uranium evaluation of the Seward-Selawik area, Alaska: Department of Energy, Grand Junction, Colo., Report GJBX-105(78), 155 p.

  • Deposit

    Bunker, C.M., Hedge, C.E., and Sainsbury, C.L., 1979, Radioelement concentrations and preliminary radiometric ages of rock in the Kigluaik Mountains, Seward Peninsula, Alaska: U.S. Geological Survey Professional Paper 1129-C, 12 p.

  • Deposit

    Till, A.B., 1980, Crystalline rocks of the Kigluaik Mountains, Seward Peninsula, Alaska: University of Washington, Seattle, M.Sc. thesis, 97 p.

  • Deposit

    Till, A.B., 1983, Granulite, peridotite, and blueschist: Precambrian to Mesozoic history of Seward Peninsula: Alaska Geological Society Journal, Proceedings of the 1982 Symposium on Western Alaska Resources and Geology, p. 59-65.

  • Deposit

    Hudson, T.L., and Arth, J. G., 1983, Tin-granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.

  • Deposit

    Forbes, R.B., Evans, B.W., and Thurston, S.P., 1984, Regional progressive high-pressure metamorphism, Seward Peninsula, Alaska: Journal of Metamorphic Geology, v. 2, p. 43-54.

  • Deposit

    Thurston, S.P., 1985, Structure, petrology, and metamorphic history of the Nome Group blueschist terrane, Salmon Lake area, Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 96, p. 600-617.

  • Deposit

    Armstrong, R.L., Harakal, J.E., Forbes, R.B., Evans, B.W., and Thurston, S.P., 1986, Rb-Sr and K-Ar study of metamorphic rocks of the Seward Peninsula and southern Brooks Range, Alaska, in Evans, B.W., and Brown, E.H., eds., Blueschists and eclogites: Geological Society of America Memoir 164, p. 184-203.

  • Deposit

    Evans, B.W. and Patrick, B.E., 1987, Phengite 3-T in high pressure metamorphosed granitic orthogneisses, Seward Peninsula, Alaska: Canadian Mineralogist, v. 25, part 1, p. 141-158.

  • Deposit

    Leiberman, J.E., 1988, Metamorphic and structural studies of the Kigluaik Mountains, western Alaska: Seattle, University of Washington, Ph.D. dissertation, 191 p.

  • Deposit

    Patrick, B.E., 1988, Synmetamorphic structural evolution of the Seward Peninsula blueschist terrane, Alaska: Journal of Structural Geology, v. 10, p. 555-565.

  • Deposit

    Patrick, B.E., and Leiberman, J.E., 1988, Thermal overprint on blueschists of the Seward Peninsula, the Lepontine in Alaska: Geology, v. 16, p. 1100-1103.

  • Deposit

    Patrick, B.E., and Evans B.W., 1989, Metamorphic evolution of the Seward Peninsula blueschist terrane: Journal of Petrology, v. 30, p. 531-555.

  • Deposit

    Miller, E.L., and Hudson, T.L., 1991, Mid-Cretaceous extensional fragmentation of a Jurassic-Early Cretaceous compressional orogen, Alaska: Tectonics, v. 10, p. 781-796.

  • Deposit

    Miller, E.L., Calvert, A.T., and Little, T.A., 1992, Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska: Geology, v. 20, p. 487-490.

  • Deposit

    Calvert, A.T., 1992, Structural evolution and thermochronology of the Kigluaik Mountains, Seward Peninsula, Alaska: Stanford Califronia, Stanford University, M.Sc. thesis, 50 p.

  • Deposit

    Hudson, T.L. 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G-1, p. 657-670.

  • Deposit

    Amato, J.M., Wright, J.E., Gans, P.B., and Miller, E.L., 1994, Magmatically induced metamorphism and deformation in the Kigluaik gneiss dome, Seward Peninsula, Alaska: Tectonics, v. 13, p. 515-527.

  • Deposit

    Dumitru, T.A., Miller, E.L., O'Sullivan, P.B., Amato, J.M., Hannula, K.A., Calvert, A.T., and Gans, P.B., 1995, Cretaceous to Recent extension in the Bering Strait region, Alaska: Tectonics, v. 14, p. 549-563.

  • Deposit

    Hannula, K.A., Miller, E.L., Dumitru, T.A., Lee, Jeffrey, and Rubin, C.M., 1995, Structural and metamorphic relations in the southwest Seward Peninsula, Alaska; Crustal extension and the unroofing of blueschists: Geological Society of America Bulletin, v. 107, p. 536-553.

  • Deposit

    Hannula, K.A., and McWilliams, M.O., 1995, Reconsideration of the age of blueschist facies metamorphism on the Seward Peninusla, Alaska, based on phengite 40Ar/39Ar results: Journal of Metamorphic Geology, v. 13, p. 125-139.

  • Deposit

    Amato, J.M., and Wright, J.E., 1997, Potassic mafic magmatism in the Kigluaik gneiss dome, northern Alaska -- A geochemical study of arc magmatism in an extensional tectonic setting: Journal of Geophysical Research, v. B102, no. 4, p. 8065-8084.

  • Deposit

    Amato, J.M., and Wright, J.E., 1998, Geochronologic investigations of magmatism and metamorphism within the Kigluaik Mountains gneiss dome, Seward Peninsula, Alaska, in Clough, J.G., and Larson, Frank, eds., Short Notes on Alaskan Geology 1997: Alaska Division of Geological and Geophysical Surveys Professional Report 118a, p. 1-21.

Comments on the references

  • Primary Reference = Hawley and Associates, 1978

General comments

Subject category Comment text
Deposit Model Name = Simple granite pegmatite with rudimentary zoning.

Reporter information

Type Date Name Affiliation Comment
Reporter 22-OCT-99 Hawley, C.C. and Hudson, Travis L. Hawley Resource Group