Browsing by Subject "Uranium ores -- Texas"

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Catahoula formation of the Texas Coastal Plain : Depositional systems, composition, structural development, ground-water flow history, and uranium distribution
(University of Texas at Austin. Bureau of Economic Geology, 1977) Galloway, William E.
The Catahoula Formation of the Texas Gulf Coastal Plain consists of two depositional systems--the Gueydan bedload fluvial system of the Rio Grande embayment and the Chita-Corrigan mixed load fluvial system of the Houston embayment. Both systems contain distinctive fluvial channel-fill, crevasse splay, floodplain, and lacustrine facies, which tend to persist vertically through the section. The paleoclimate varied from subarid in the Gueydan system to humid in northeastern parts of the Chita-Corrigan system. Gueydan sands are dominated by plagioclase feldspar and volcanic rock fragments reflecting a western source; in contrast, Chita-Corrigan sands are quartzose and were primarily reworked from mixed sedimentary terranes. Clay composition reflects alteration to montmorillonite and kaolinite of large volumes of volcanic ash deposited in both systems in response to pedogenesis and shallow burial diagenesis. Growth faults initiated by early Tertiary deltaic progradation extend up into the Catahoula and profoundly influence trends of fluvial sand units and post-depositional ground-water flow. Consequently, fault zones may localize uranium mineralization, but faulting is not necessary for development of commercial deposits. Diagenetic features, distribution of trace uranium in fine-grained tuffaceous facies, and reconstructed ground-water flow history in the Catahoula provide the basis for interpretation of a terrigenous coastal plain uranium cycle. 1. Uranium was leached from volcanic ash soon after deposition by pedogenic processes and moved into shallow ground-water circulation cells. 2. Oxidizing uranium-enriched waters entered semi-confined aquifer sands in areas of regional recharge. 3. Geometry of the flow system was determined by the three-dimensional facies and structural framework of the aquifer system. 4. Uranium was concentrated by aqueous geochemical gradients as discrete mineralization fronts that were closely associated with iron oxidation fronts. Uranium was preferentially deposited where facies changes or faulting induced cross-stratal flow from permeable fluvial channel facies into interbedded or less permeable overbank facies. 5. Post-mineralization decrease of regional and local ground-water flux has resulted in reequilibration of large parts of the aquifer with the regionally reducing subsurface environment. The inferred uranium cycle provides criteria that can be used to compare the uranium potential of the Gueydan and Chita-Corrigan fluvial systems and to determine the possible distribution and nature of mineralization within each depositional system. These criteria apply similarly to other potential coastal plain uranium host systems.
Catahoula formation of the Texas Coastal Plain : origin, geochemical evolution, and characteristics of uranium deposits
(University of Texas at Austin. Bureau of Economic Geology, 1980) Galloway, William E.; Kaiser, W. R.
The Catahoula Formation is composed of ancient fluvial sediments that controlled a wide range of water/sediment interactions responsible for uranium mobilization, transportation, and concentration. Uranium was released from volcanic glass deposited within the Catahoula through early pedogenic and diagenetic processes. Soil development produced plasmic clay cutans, oxide nodules, and vacuoles; open hydrologic system diagenesis produced shard-moldic porosity and clinoptilolite pore-filling cement. Pedogenesis was the most efficient process for mobilizing uranium. Original uranium content in fresh Catahoula glass is estimated to have averaged at least 10 ppm; about 5 ppm was mobilized after deposition and made available for migration. Uranium was transported predominantly as uranyl bicarbonate ion by oxidizing neutral to mildly basic, bicarbonate- and silica-rich ground waters. Uranium transport is continuing today in parts of the Catahoula aquifer in oxidizing (+240to +300 mV) and neutral to highly basic (pH 7 to 11) ground waters. The chemistry of modern Catahoula ground waters reflects down flow ionic evolution and localized mixing with compositionally diverse waters discharged vertically from underlying aquifers. Chlorinity mapping reveals modern ground-water flow patterns, suggests hydrodynamic interpretation of alteration-front geometry, and provides clues to flow dynamics extant during earlier aquifer evolution. Isochemical contours reproduce geometries reminiscent of alteration fronts, reveal vertical discharge of saline waters across aquitards and up fault zones, and demonstrate updip movement of sulfide-rich waters apparently intruded into shallow aquifers along faults. Six uranium deposits representative of the spectrum of Catahoula ores were studied. Uranium-bearing meteoric waters were reduced by reaction with pre-ore stage pyrite formed by extrinsically introduced fault-leaked sulfide (for example, Bruni deposit) or intrinsically by organic matter (for example, Washington-Fayette deposit). Uranium was concentrated in part by adsorption on Ca-montmorillonite cutans, amorphous TiO2, and/ or organic matter followed by uranyl reduction to U4+ in amorphous uranous silicates. Field and geochemical evidence shows that clinoptilolite, a potential adsorber of uranium, is not correlative with mineralization. Calcite is pervasive throughout host sands but shows no spatial or temporal relationship to uranium mineralization. Waters presently associated with Catahoula uranium deposits are oxidizing, alkaline waters of high ionic strength and are not appropriate models for the primary mineralizing waters, which are postulated to have been reducing, acid waters of low to moderate ionic strength. The presence of marcasite and uranium together at the alteration front strongly supports an acid pH during Catahoula mineralization. Maximum adsorption and minimum solubility of uranium occur at approximately pH 6 in carbonate-rich waters. Solution and mineral equilibria were used to test activities and mineral saturation against the occurrence of uranium in four deposits. Log activity ratios of individual waters more highly supersaturated with respect to montmorillonite, taken from montmorillonite-clinoptilolite activity diagrams, show a positive correlation with uranium mineralization. High Ca2+, Mg2+, Al(OH)-4, and H+ activities promote the formation of montmorillonite relative to clinoptilolite. High saturation ratios for montmorillonite show fair correlation with mineralization. The mineral-solution equilibria approach is a potential method of geochemical exploration.
Epigenetic zonation and fluid flow history of uranium-bearing fluvial aquifer systems, South Texas uranium province
(University of Texas at Austin. Bureau of Economic Geology, 1982) University of Texas at Austin. Bureau of Economic Geology
The Oligocene-Miocene fluvial uranium host aquifers of the South Texas uranium province were deposited principally as syndepositionally oxidized sands and muds. Early intrusion of reactive sulfide- enriched waters produced large intrastratal islands of epigenetic sulfidic alteration, which contain isotopically heavy pyrite exhibiting unique replacement textures. The only known reservoir containing such sulfidic waters is the deeply buried Mesozoic carbonate section beneath the thick, geopressured Tertiary basin fill. Thermobaric waters were expulsed upward along major fault zones into shallow aquifers in response to a pressure head generated by compaction and dehydration in the abyssal ground-water regime. Vertical migration of gaseous hydrogen sulfide was less important. Repeated flushing of the shallow aquifers by oxidizing meteoric waters containing anomalous amounts of uranium, selenium, and molybdenum alternating with sulfidic thermobaric waters caused cyclic precipitation and oxidation of iron disulfide. Uranium deposits formed along hydrologically active oxidation interfaces separating epigenetic sulfidic and epigenetic oxidation zones. Multiple epigenetic events are recorded in imperfectly superimposed, multiple mineralization fronts, in regional and local geometric relations between different alteration zones, and in the bulk matrix geochemistry and mineralogy of alteration zones. The dynamic mineralization model described in this report may reflect processes active in many large, depositionally active basins.
Uranium in Texas, 1967
(University of Texas at Austin. Bureau of Economic Geology, 1967) Flawn, Peter Tyrell
The uranium industry, born in boom in the late 1940's and early 1950's, fell upon hard times after about a decade of lusty growth as anticipated private markets failed to develop on schedule and the United States Atomic Energy Commission cut back and stretched out its purchase program. Exploration for uranium in the United States came to a halt. Mills closed down or operated on reduced schedules as contracts expired. But in 1965 there were signs of change as more and more announcements of construction of nuclear reactors for generation of electric power appeared in the newspapers, and by 1966, the discouraged uranium salesman found doors opening rapidly and smiles on the faces of his potential customers. The hoped-for private-sector market for uranium had become a reality. By September 1, 1966, a total of 47 reactors were either in operation, under construction, or firmly committed in the United States; of the total, orders for or commitments for 32 were made since February of 1965. The industry considered this sharply rising curve, looked at the nuclear fuel requirements, appraised the known reserves of uranium ore, and literally sprang into action. In the first half of 1966, only about half a million feet of exploratory drilling was completed; twice this was scheduled for the second half of the year and a million and a half feet has been budgeted for 1967.