Implications of the geology and geochemistry of the Maclean Five uranium deposit, Three Rivers, Texas
The Maclean Five uranium deposit is an unusual ''dike-like'' accumulation of uranium and molybdenum minerals in the Miocene fluvial Oakville Sandstone, along a down-to-coast normal fault that displaces both the Catahoula and Oakville Formations. The fault-related configuration of these ores presents a marked contrast with adjacent rollfront and tabular deposits to the north. Petrographic analysis of the barren host rock reveals a composition including 17.3% limestone rock fragments (LRF's), 22.2% volcanic rock fragments (VRF's), and 19.4% calcite cement. X-ray diffraction and electron microprobe analyses indicate the ore assemblage to be predominantly uraninite and coffinite, with subordinate sphalerite and marcasite. Neutron activation analysis data establish that elements fixed in inherent host rock minerals are pseudonormally or normally distributed, whereas elements associated with uranium are lognormally distributed. Depth-concentration plots show three vertical zones of uranium enrichment. Uranium in the core samples displays highly significant positive correlations with Mo and As. The proposed ''fault-trap'' model of ore formation includes three phases: (1) dissolution of pre-existing mineralized bodies in response to weathering and stream erosion; (2) discharge of uraniferous carbonate solutions to a restricted fault zone; (3) precipitation of calcite within the microenvironments of pre-existing cement and deposition of ore-stage minerals, due to sharp, local reductions in pH. Eh remains relatively constant at the fault zone due to a continual influx of reducing gases from hydrocarbon deposits at depth. Narrow linear anomalies of U, Mo, and As in geochemical sampling media should serve as potential pathfinders for this deposit-type. 52 refs., 32 figs., 17 tabs.
- Research Organization:
- Oak Ridge Associated Universities, Inc., TN (USA)
- DOE Contract Number:
- AC05-76OR00033
- OSTI ID:
- 5660832
- Report Number(s):
- DOE/OR/00033-T102; ON: DE85015015
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products. Thesis. Submitted to Univ. of Tennessee, Knoxville
- Country of Publication:
- United States
- Language:
- English
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