Geology and ore deposits of Johnny M mine, Ambrosia Lake District
The Johnny M mine is one of very few mines in the Ambrosia Lake district with uranium ore in two members of the Morrison Formation (Jurassic); these members are the Westwater Canyon Sandstone and the Brushy Basin Shale. The Westwater Canyon ore is contained in the two upper sandstone units of the member, and the Brushy Basin ore is contained in the Poison Canyon sandstone (informal usage). The sedimentary features and structures in the Westwater Canyon sandstones indicate that the sediments were deposited by a system of aggrading braided streams, possibly at the distal end of coalescing alluvial fans. The Poison Canyon sandstone was probably the result of deposition in a complex environment of meandering and braided streams. Paleocurrent-direction indicators, such as fossilized-log orientation, foreset azimuths, and the axes of crossbeds and channel scours, suggest that the local palostream flow was to the east and southeast. The uranium mineralization is closely associated with 1) local accumulations of carbonaceous (humate) matter derived from the decay of organic material and 2) paleostream channels preserved in the rocks. The ore elements were derived from the leaching of volcanic air-fall tuffs and ash, which were introduced into the fluvial system during volcanic activity in the western United States. The mobile ore-element ions were reduce and concentrated by humic acids and bacteria present in the fluvial system and ultimately remobilized into the forms present today. The uranium is thus envisioned as forming either essentially on the surface as the sediments were being deposited or at very shallow depth.
- Research Organization:
- Shell Oil Co., Houston, TX
- OSTI ID:
- 6033804
- Report Number(s):
- CONF-7905120-; TRN: 81-017866
- Journal Information:
- Mem. - N.M. Bur. Mines Miner. Resour.; (United States), Vol. 38; Conference: New Mexico Bureau of Mines and Mineral Resources conference, Albuquerque, NM, USA, 13 May 1979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NEW MEXICO
URANIUM DEPOSITS
EXPLORATION
GEOLOGY
JURASSIC PERIOD
SANDSTONES
SHALES
URANIUM ORES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
MESOZOIC ERA
MINERAL RESOURCES
NORTH AMERICA
ORES
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SOUTHWEST REGION
USA
050100* - Nuclear Fuels- Reserves
Exploration
& Mining
050200 - Nuclear Fuels- Exploration- (-1987)