Limestone uranium

Mineralization in underlying rudistid limestones uranium occurs in faults, solution cavities, palaeo-karsts and other zones in fetid limestone beneath volcanics at Domatilla mine. 

Other Deposits. Those deposits which cannot be classified as one of the previous 14 deposit types are called other. These include the uranium deposits in the Jurassic Todilto Limestone in the Grants district in New Mexico (17). 

Ratios of U and U to Th and Ra daughters, combined with differences in chemical reactivity have been used to investigate the formation and weathering of limestone in karst soils of the Jura Mountains, and of the mountains in the central part of Switzerland. Uranium contained within calcite is released during weathering, and migrates as stable uranyl(VI) carbonato complexes through the soil. In contrast, the uranium decay products, Th and Ra,... 

Figure 20. Secular variation in 5 U(0) for Bahamas flowstone sequence. Changes in 5 U(0) are related to uranium-series disequilibrium conditions in host limestone, periodic addition of new material with elevated (marine) 5 U(0), alpha recoil effects and variation in recharge, and hence water-rock interaction times (see text for details).

Cowart, J. B., Osmond, J. K., Oxidation/reduction in the Edwards Limestone aquifer as indicated by dissolved uranium isotopes, Geol. Soc. America, Abstracts with Programs, 9(7), 938 (1977). 

Non-metamorphic equivalents of this Th-free mineralization may be sought in some rare limestone-hosted U-occurences, such as the Jurassic Todilto lacustrine formation in the Grant Uranium Belt (Rawson Richard 1980), the Cretaceous Toolebuc marine formation in Eromanga Basin (Ramsden 1982), the Mesoproterozoic Vempale marine formation in Cuddapah Basin (Sinha et al. 1989), and the Cretaceous Probeer marine formation in the Huab deposit (Hartleb 1988). 

Rawson, R. Richard, R. 2002. Uranium in Todilto Limestone (Jurassic) of New Mexico... 

TYUYANUN1TE. An ore of uranium with the composition. Ca(U02)2 (V04)2 5 — 8H2O, which occurs in yellow incrustations as a secondary mineral. The mineral is orthorhombic, It occurs as a secondary mineral as incrustations on limestones, and as disseminated impregnations in sandstones. Found abundantly 111 the Western United Stales, at Grants, New Mexico, and in Wyoming, Utah, Colorado. Nevada, Arizona and Texas. Also at Tyuya Muyan in Turkestan, the former U.S.S.R. 

There are several uranium ore-bodies in the world that cannot be leached economically with sulfuric acid because of the high limestone content of the ore. Such ore-bodies are generally leached with an alkaline solution of sodium carbonate and bicarbonate. Carbonate also forms anionic complexes with the uranyl ion the predominant species being UC fCC 4- — and may therefore also be treated with anion-exchange resins. 

The behavior of uranium varies considerably across samples studied. Palmer and Edmond (1993) have reported increasing trends of uranium concentration with river alkahnity in the Orinoco, Amazon and Ganga river basins, showing the importance of limestone and black shale dissolution for the control of uranium concentrations in river waters. The association of uranium and major soluble elements is also reported by Elbaz-Poulichet et al. (1999) for the upper Amazonian basins of Bohvia. However, under the organic-rich conditions of Scandinavian rivers (Porcelli et al., 1997) or African rivers (Viers et al., 1997), uranium concentrations can be decoupled from those of major elements, due to the existence of a colloidal fraction of uranium. 

Gomes F. V. M. and Cabral F. C. F. (1981) Utilization of natural uranium isotopes for the study of ground water in Bambui limestone aquifer, Bahia. Revista Brasileira de Geociencias 11, 179—184. 

Muhs D. R. and Szabo B. J. (1994) New uranium-series ages of the Waimanalo Limestone, Oahu, Hawaii implications for sea level during the last interglacial period. Mar. Geol. 118, 315-326. 

Limestone cave levels within the Dukes system in the Buchan district of East Gippsland in Victoria, southeastern Australia (Fig. 1) can be correlated with a series of three river terraces in the valley of the Buchan River (Webb et al., 1992). Both caves and terraces are thought to have developed in the Pleistocene, because uranium series dating of speleothems in this system gives ages of more than 350,000 years, and perhaps greater... 

Some uranium ore bodies are high in limestone and dolomitic content which is wasteful on acid employed for leaching. Such sources are successfully treated by an alkaline mixed sodium carbonate and bicarbonate leach, the later being required to buffer the pH so as not to precipitate the uranium. Sorption occurs as the uranyl carbonate complex anion, U02(C03)3 , but elution is with sodium nitrate since acid would cause evolution of carbon dioxide gas. 

This technique depends on the fact that the three uranium L x-rays, which accompany 25% of all 23sp decays, are of slightly differing energies and therefore have different absorption coefficients in the limestone. Figure 2 shows the spectrum of these L x-rays observed through several samples of wet limestone. These were thin measured slices of the limestone which were interposed as absorbers between a source of 238p radiation and the detector. The ratio of the intensities of the L1/L2 x-rays decreases with the thickness of the stone similarly the L3/L2 ratio increases with thickness. It is a simple matter to calibrate... 

The types of substance that are thermoluminescent, either in their natural state or after radiation bombardment, include (112) the alkali metal halides, calcite, dolomite, fluorite, aluminum oxide, magnesium oxide, gypsum, quartz, glass, feldspars, feldspathoids, certain dried clays, and ceramic materials. Of over 3000 rock samples examined for thermoluminescence, some 75% showed visible fight emission (112). Nearly all limestones and acid igneous rocks are naturally thermoluminescent, due mainly to the presence of trace elements of uranium, thorium, and so on. Calcium and magnesium... 

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