Dillon quadrangle, Montana and Idaho

Technical Report · Tue Mar 31 23:00:00 EST 1981

DOI:https://doi.org/10.2172/6444656· OSTI ID:6444656

Wodzicki, A.; Krason, J.

All geologic conditions in the Dillon quadrangle (Montana and Idaho) have been thoroughly examined, and, using National Uranium Resource Evaluation criteria, environments are favorable for uranium deposits along fractured zones of Precambrian Y metasediments, in the McGowan Creek Formation, and in some Tertiary sedimentary basins. A 9-m-wide quartz-bearing fractured zone in Precambrian Y quartzites near Gibbonsville contains 175 ppM uranium, probably derived from formerly overlying Challis Volcanics by supergene processes. The Mississippian McGowan Creek Formation consists of uraniferous, black, siliceous mudstone and chert. In the Melrose district it has been fractured by a low-angle fault, and uranium has been further concentrated by circulating ground water in the 2- to 6-m-thick brecciated zones that in outcrop contain 90 to 170 ppM uranium. The Wise River, northern Divide Creek, Jefferson River, Salmon River, Horse Prairie, Beaverhead River, and upper Ruby River Basins are considered favorable for uranium deposits in sandstone. Present are suitable uraniferous source rocks such as the Boulder batholith, rhyolitic flow breccia, laharic deposits, or strongly welded tuffs; permeable sediments, including most sandstones and conglomerates, providing they do not contain devitrified glass; suitable reductants such as lignite, pyrite, or low-Eh geothermal water; and uranium occurrences.

• Research Organization: Geoexplorers International, Inc., Denver, CO (USA)
• DOE Contract Number: AC13-76GJ01664
• OSTI ID: 6444656
• Report Number(s): GJQ-007(81)
• Country of Publication: United States
• Language: English

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