Lacustrine-humate model for primary uranium ore deposits, Grants Uranium Region, New Mexico
Two generations of uranium ore, primary and redistributed, occur in fluvial sandstones of the Upper Jurassic Morrison Formation in the San Juan basin; the two stages of ore formation can be related to the hydrologic history of the basin. Primary ore formed soon after Morrison deposition, in the Late Jurassic to Early Cretaceous, and a model, the lacustrine-humate model, is offered that views primary mineralization as a diagenetic event related to early pore fluid evolution. The basic premise is that the humate, a pore-filling organic material closely associated with primary ore, originated as humic acids dissolved in pore waters of greenish-gray lacustrine mudstones deposited in the mud-flat facies of the Brushy Basin Member and similar K shale beds in the Westwater Canyon Member. During compaction associated with early burial, formation water expelled from lacustrine mudstone units carried these humic acids into adjacent sandstone beds where the organics precipitated, forming the humate deposits that concentrated uranium. During the Tertiary, much later in the hydrologic history of the basin, when Jurassic sediments were largely compacted, oxygenated ground water flowed basinward from uplifted basin margins. This invasion of Morrison sandstone beds by oxidizing ground waters redistributed uranium from primary ores along redox boundaries, forming ore deposits that resemble roll-front-type uranium ores. 11 figures.
- Research Organization:
- Geological Survey, Denver, CO
- OSTI ID:
- 5942373
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 69:11; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
Similar Records
Sedimentology of the Westwater Canyon and Brushy Basin Members, Upper Jurassic Morrison Formation, Colorado Plateau, and relationship to uranium mineralization
Geology and ore deposits of Johnny M mine, Ambrosia Lake District
Related Subjects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
CRETACEOUS PERIOD
DEPOSITION
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
JURASSIC PERIOD
MESOZOIC ERA
MINERAL RESOURCES
NEW MEXICO
NORTH AMERICA
ORIGIN
RESOURCES
SEDIMENTARY BASINS
URANIUM DEPOSITS
USA