Sedimentary uranium

Rose, A.W. Wright, R.J. 1980. Geochemical exploration models for sedimentary uranium deposits geochemical exploration for uranium. Journal of Geochemical Exploration, 13, 153-179. 

What geologic conditions lead to the formation of sedimentary uranium ore deposits and to their preservation for geologic times ... 

An example of such a system is the sedimentary uranium deposit in Tono, Japan, studied by Nohara et al. The ground water moves through the area with a velocity of 0.001 to 1... 

Scott J. H. and Daniels J. J. Non-radiometric borehole geophysical detection of geochemical haloes surrounding sedimentary uranium deposits. Reference 5, 379-90. 

Ertle H. J. Kneuper G. and Muller H. Sedimentary uranium occurrences in the Upper Carboniferous of the northern Black Forest. In Recognition and evaluation of uraniferous provinces (Vienna IAEA, 1977), 217-27. 

Phosphorite Deposits. Sedimentary phosphorites contain low concentrations of uranium in fine-grained apatite. Uranium of this type is considered an unconventional resource. Significant examples of these uranium ore types include the U.S. deposits in Elorida, where uranium is recovered as a by-product, and the large deposits in North African and Middle Eastern countries (16). 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Langmuir D (1978) Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits. Geochim Cosmochim Acta 42 547-569 Langmuir D, Herman JS (1980) The mobility of thorium in natural waters at low temperatures. Geochim Cosmochim Acta 44 1753-1766... 

In the Delaware and Chesapeake estuaries (USA), uranium shows distinctly nonconservative behavior at salinities <5 (Sarin and Church 1994 Church et al. 1996). This was suggested to be due to sedimentary redox processes in the extensive salt marshes in the Delaware and Chesapeake bays. From mass balance calculations it was concluded that almost two-thirds of the uranium in the tidal waters were retained in the sediments. It was also suggested that, extrapolated globally, uranium removal in salt marshes and marine wetlands, including mangroves, are important sinks for U that may responsible for up to 50% of the total marine removal (Church et al. 1996). Removal of U is also observed within the Baltic Sea, related to the association of U with colloids (see Section 2.5). 

As in the case of igneous processes, the sedimentary processes of rock formation lead to the formation economic mineral deposits. Many valuable mineral deposits of iron, manganese, copper, phosphorus, sulfur, zirconium, the rare Earths, uranium and vanadium owe their origin to sedimentary processes. Some of these constitute special types of sedimentary rocks, while others form important constituents of sedimentary rocks. 

Palaeoplacers are placer concentrations that have occurred in the geological past and which are preserved till the present by a cover of later sedimentary rocks. The Witwatersrand gold-uranium deposits (South Africa) and the uranium deposits at Blind River (Ontario, Canada) and Jacobina (Brazil) are the most important examples of palaeoplacers. 

Syn-sedimentary chemical deposits form by chemical and biochemical precipitation of valuable metal components carried in solution, concomitant with the formation of the enclosing sedimentary rock. The manner of such deposition depends on the concentration of the metal in the solvent, the solubility of the precipitating product, the solution chemistry, and the deposition environment. Iron, manganese, phosphorus, lead, zinc, sulfur and uranium are some of the elements that have formed economically valuable deposits by chemical precipitation during sedimentation. 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

In the fertilizer manufacturing scheme, the wet process phosphoric acid most commonly ensues from dissolution of sedimentary phosphate rock in sulfuric acid. Such acid solution contains around 1 g 1 1 uranium which is recovered as the byproduct. This task is accomplished by three well-proven extraction processes, some salient details of which are presented in Table 5.10. 

Kyser, T.K., Chipley, D., Vuletich, A., Alexandre, P. 2008. Variations in 238U/235U ratios in natural uranium ore minerals from sedimentary basins Abstracts of the 18th annual V. M. Goldschmidt conference. Geochimica et Cosmochimica Acta, 72(12), A508. 

Field measurements in sedimentary fluvial-type calcrete deposits also suggest that present-day groundwater in these areas may also display potential to both dissolve and precipitate uranium in the near surface. Chemical dilatancy and evaporation-driven diffusion that promote de-complexing, diffusion, and reprecipitation mechanisms are seen to play integral parts in the continued chemical reworking and modification of these calcrete-hosted carnotite deposits. 

Most uranium deposits in sedimentary rocks are associated with geochemical provinces enriched in U and Th or with U-... 

FIolk, G.J., Kyser, T.K. Don Chipley, FIiatt, E.E., Marlatt, J. 2003. Mobile Pb-isotopes in Proterozoic sedimentary basins as guides for exploration of uranium deposits. Journal of Geochemical Exploration, 80, 297-320. 

Unconformity-type uranium deposits from the Athabasca Basin (Saskatchewan, Canada) represent the worid-richest uranium ores with the McArthur River deposit as a prime exampie. They are mainiy iocated ciose to the unconformity between a Paieo- to Meso-Proterozoic sedimentary basin, the Athabasca Basin, and an Archean to Paieoproterozoic metamorphic to piutonic basement. For severai years, a new type of uraniferous mineraiization, entireiy iocated in the basement, has been driiied in the South-Eastern part of the basin. Few data are avaiiabie for this type of deposit, iimiting the comparison of their characteristics and possibie genetic iinks with deposits iocated at the unconformity. 

Adams, S.S. Smith, R.B. 1988. Geology and recognition criteria for sandstone uranium deposits in mixed fluvial-shallow marine sedimentary sequences, South Texas. Bendix Field Engineering Corporation, Grand Junction, Colorado NURE Report GJBX-4(81), 146 p. 

Parsons, A. 2007. Potential for Uranium mobilization from weathered outcrops of uranium-bearing sedimentary strata, southern Nova Scotia. BSc Honours Thesis, Earth Sciences, Dalhousie University. 

Miocene sandstone overlying Jurassic sedimentary rocks occur in the Turpan-Hami Basin. Sandstone-type uranium... 

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