National Uranium Resource Evaluation: Lewistown Quadrangle, Montana
Uranium resources in the Lewistown Quadrangle, Montana, were evaluated to a depth of 1500 m (5000 ft). All existing geologic data were considered, including geologic surveys, literature, theses, radiometric surveys, oil- and water-well logs. Additional data were generated during the course of two field seasons, including the collection of more than 350 water, rock, crude oil and panned concentrate samples for analyses, sedimentary facies maps, structural geology and isopach maps, and field examination of reported areas of anomalous radioactivity. Three environments with potential for the occurrence of a minimum of 100 t of 0.01% U/sub 3/O/sub 8/ were delineated. The most favorable environment is located in the southeastern portion of the quadrangle; here, Tertiary felsic dikes intrude four potential sandstone host rocks in the Kootenai Formation and the Colorado Shale. Structural-chemical traps for allogenic uranium are provided by the juxtaposition of oil-bearing domes. A second potential environment is located in the Eagle Sandstone in the northwestern and western portions of the quadrangle; here, anomalous water samples were obtained downtip from oxidized outcrops that are structurally related to Tertiary intrusive rocks of the Bearpaw and Highwood Mountains. Lignitic lenses and carbonaceous sandstones deposited in a near-shore lagoonal and deltaic environment provide potential reductants for hexavalent uranium in this environment. A third environment, in the Judith River Formation, was selected as favorable on the basis of water-well and gamma-ray log anomalies and their structural relationship with the Bearpaw Mountains. Organic materials are present in the Judith River Formation as potential reductants. They were deposited in a near-shore fluvial and lagoonal system similar to the depositional environment of the Jackson Group of the Texas Gulf Coast.
- Research Organization:
- Robinson (Charles S.) and Associates, Inc., Lakewood, CO (USA)
- DOE Contract Number:
- AC13-76GJ01664
- OSTI ID:
- 6815347
- Report Number(s):
- PGJ/F-111-82; ON: DE82021652
- Resource Relation:
- Other Information: Includes 3 sheets of 24x reduction microfiche. Portions of document are illegible
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGICAL SURVEYS
DATA ANALYSIS
MONTANA
RADIOMETRIC SURVEYS
URANIUM DEPOSITS
EVALUATION
EXPLORATION
WELL LOGGING
FEDERAL REGION VIII
GEOLOGIC DEPOSITS
GEOPHYSICAL SURVEYS
MINERAL RESOURCES
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