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Geologic Controls and Radon Occurrence in New England
Published in Barbara Graves, Radon, Radium, and Other Radioactivity in Ground Water, 2020
Francis R. Hall, Eugene L. Boudette, William J. Olszewski
As field evidence accumulated, it became clear that high radon levels were correlated with rock type. In fact, the highest values are associated with two-mica granites (Figure 1, Group 2). Concentrations in ground water in the range of 50,000-100,000 pCi/l are fairly common and values in excess of 1,000,000 pCi/l are documented. Very high levels of radon commonly occur where pegmatite dikes are present in the granite [14, 17]. The two-mica granite is anatectic, formed by the partial melting of some protolith. If this protolith is enriched with uranium, then the partial melting can preferentially fractionate uranium into two-mica magma, thus further enriching it in uranium. Uranium in two-mica granite and associated pegmatite is commonly dispersed uranium oxides such as uraninite and coffinite, and it is nearly all labile. Labile uranium is readily transported by ground water, especially at a pH less than 7, over a wide range of redox conditions. Deposits of secondary uranium minerals are common in two-mica granite.
Nuclear Fuel Resources
Published in Kenneth D. Kok, Nuclear Engineering Handbook, 2016
Sandstone deposits constitute about 18% of world uranium resources. Ore bodies of this type are commonly low-to-medium grade (0.05%–0.4% U3O8), and individual ore bodies are small to medium in size (ranging up to a maximum of 50,000 t U3O8). The main primary uranium minerals are uraninite and coffinite. Conventional mining/milling operations of sandstone deposits have been progressively undercut by cheaper in situ leach mining methods. The United States has large resources in sandstone deposits in the Western Cordillera region, and most of its uranium production has been from these deposits, recently by ISL mining. The Powder River Basin in Wyoming, the Colorado Plateau, and the Gulf Coast Plain in south Texas are major sandstone uranium provinces. Other large sandstone deposits occur in Niger, Kazakhstan, Uzbekistan, Gabon (Franceville Basin), and South Africa (Karoo Basin). Kazakhstan has reported substantial reserves in sandstone deposits with average grades ranging from 0.02% to 0.07% U.
Acid In Situ Leach uranium mining — 1. USA and Australia
Published in A.A. Balkema, Tailings and Mine Waste 2000, 2022
The uranium ore at NML was precipitated at the interface of oxidation-reduction boundaries in the Teapot sandstone, due to the presence of carbonaceous material and pyrite. The principal uranium mineral was uraninite, with minor quantities of coffinite. Vanadium was associated with the mineralization (about 1.3%) and was proposed to be extracted from a commercial facility. The ore contained less than 0.1% carbonate, although total carbon content was higher at 0.2–2.0%. The major clay mineral present was kaolinite (2–5%), with minor montmorillonite, although this had a low cation exchange capacity at about 5 meq/100 g.
Laboratory core investigations of sandstone-hosted uranium for in situ recovery
Published in Applied Earth Science, 2020
Micha Zauner, Andreas Weller, Matthias Halisch
Figures 5 and 6 show the modal mineralogy and GXMAP images of the analysed thin sections of selected drill cores, emphasizing rock texture and mineralization style. Both are medium- to coarse-grained arkosic sandstones composed of quartz, feldspar (K-fsp and plagioclase), accessory clay minerals (kaolinite/dickite, illite), and organics/carbonates. The elemental composition represents typical arkosic sandstone, whereas aluminium, sodium, potassium, and calcium are mostly incorporated in residual feldspar. Calcium is also present in accessory carbonates forming a binding component in the cement. The uranium minerals are generally very fine grained (<1 µm) but also form mixed grains or agglomerates up to 100 µm. Since the individual grain size of the single V or U crystal phase is <1 µm, it is below the LOD of the SEM, and thus they are classified as mixed phases (U-V-silicates mixed phases). Other methods are required for unambiguous phase identification. According to local geology, most of the uranium is probably mineralized as coffinite and uraninite. The uranium minerals form coatings around the silicates and occur as fine agglomerates in interstitial pore spaces, as illustrated in Figure 6.