Environmental risk and mobilization of uranium and potentially toxic elements during leaching of the sandstone-type uranium ore.

Characterization of groundwater and cores in the decommissioned acid in-situ leach uranium mining area: Enlightenment for uranium contaminated groundwater remediation

The article deals with the issues of software and mathematical support for the prompt fission neutron logging method using the dual-probe equipment AINK-49. Standalone software provides the automation of its log data processing and interpretation for determining uranium content in ores of sandstone-type deposits. The description of the software for logging survey and automated processing and interpretation of the obtained log data is presented.

Abstract In India, Atomic Minerals Directorate for Exploration and Research (AMD), the oldest unit under the Department of Atomic Energy (DAE) is mandated with the exploration and augmentation of atomic mineral(s) resources of the country to support the Nuclear Power Programme (NPP) of India. AMD, till date have established four (04) generations of uranium metallogeny in India, distributed in 46 deposits and several other occurrences, major share of which are contributed by the globally unique, stratabound carbonate hosted, syn-diagenetic Tummalapalle Group of deposit (~59%), metamorphite type deposits along the Singhbhum Shear Zone (~21%), unconformity related deposits in northern part of Cuddapah Basin (~5%) and sandstone type deposits in Cretaceous Mahadek Basin (~6%). Besides these, metasomatite type deposits along the North Delhi Fold Belt (4%) and granite related-structurally controlled, high grade deposits in Bhima Basin (2%) along with some small hydrothermal/metamorphite/migmatite type deposits in Aravalli, Kotri-Dongargarh, Higher Himalaya belts and Chhotanagpur Granite Gneiss Complex contribute to the national inventory which stands at 3,76,000 tonne uranium oxide. AMD have stockpiled substantial quantities of Nb-Ta, Be and Li minerals needed for the NPP of India from prospective pegmatite belts in the country. AMD have established immense potential for REE mineralization in carbonatite complexes of Ambadungar in Gujarat and per-alkaline granite-rhyolite of Siwana Ring Complex, Barmer district, Rajasthan. Exploration along the coastal and riverine placers of the country has established 130 heavy mineral placer deposits with substantial thorium and REE resources. The progressive advancements by AMD through adaptation of integrated multidisciplinary exploration techniques coupled with major thrust in airborne/ground geophysics and expansion of state-of-the-art analytical facilities have facilitated systematic planning for future augmentation of atomic mineral(s) resources. Exploration inputs are envisaged to be intensified in the brownfield target areas for resource augmentation while R&D and phase-wise exploration inputs will be focused for developing the identified greenfield areas following a planned roadmap to ensure selfsufficiency in atomic mineral resources for sustained growth of the NPP to reach the target of net zero carbon emissions by 2070.

This study, carried out in tailings from two sediment-hosted stratiform copper deposits in the Lublin-Głogów Copper District in Poland (Kupferschiefer-type deposit) and Zhezkazgan (cupriferous sandstone-type deposit) in Kazakhstan, analysed the mineralogy of copper, zinc, and lead minerals as related to metal accumulation in sediments. Microscopic study in reflected light and SEM–EDS (Scanning Electron Microscope—Energy Dispersive Spectrometer) analysis, as well as chemical diversity in the used INAA (Instrumental Neutron Activation Analysis), ICP (Inductively Coupled Plasma), and AAS (Atomic Absorption Spectroscopy) methods in 35 samples from Kazakhstan and 35 from Poland were examined due to their diversity. In both tailing deposits in Kazakhstan and Poland, heavy fractions were dominated by copper sulphides: chalcopyrite (CuFeS2), bornite (Cu5FeS4). and chalcocite (Cu2S). Moreover, sphalerite, galena, and cerussite have been recognized as a carriers of Zn and Pb. Their geochemistry was dominated by Cu, showing a mean content of 2500 ppm, in both Poland and Kazakhstan. Zinc and lead also occurred, showing a content of approximately 200 ppm and 500 ppm in Poland, and 1500 ppm Zn and 2500 ppm Pb in Kazakhstan, respectively. Grain size analysis indicated that the dominant grain size in both districts corresponded to the silt and fine sands fractions. Copper, zinc and lead sulphides accumulated in fine fractions in tailings from Kazakhstan (in sandstones and quartz grains), and mainly in coarse fractions in Poland (within carbonates, sandstones, and black shales). Mineralogical and geochemical features should be taken into consideration when assessing potential metal sources of technogenic materials.

In this paper, uranium ore samples collected from different hole depth and different numbered hole. The effects of uranium speciation to in situ leaching of uranium were analyzed by sequential chemical extraction and sulfuric acid leaching tests. These results imply that the distribution characteristics of uranium speciation are significantly different whether they are in the same numbered uranium ore sample or in the different numbered uranium ore samples. The residual uranium are the most component in primary mineral. The acidity has a great influence on the leaching rate of uranium ore in situ leaching of uranium.

Coupled uranium mineralisation and bacterial sulphate reduction for the genesis of the Baxingtu sandstone-hosted U deposit, SW Songliao Basin, NE China

The 238U/235U ratio was precisely measured in uranium minerals from 11 hydrothermal deposits of different geologic settings and ages situated in ore regions of Asia, Europe, Africa, and North America by MC-ICP-MS using a 233U-236U double spike. The spike was calibrated in reference to the CRM-112A standard with 238U/235U = 137.837 ± 0.015 (Richter et al, 2010). The long-term reproducibility of 238U/235U measurement was estimated as ±0.07‰ by the analysis of monitor samples and the IRMM-3184 standard. The analyses were performed using 0.02–0.04-mg microsamples of uraninite, pitchblende, and coffinite, which were locally extracted from polished sections under an optical microscope. The 238U/235U values obtained for 50 samples of U-bearing minerals range from 137.703 to 137.821, with a 0.86‰ difference and a mean 238U/235U value of 137.773 ± 0.056 (±2SD). The range of 238U/235U variations in seven deposits with uraninite is 0.41‰, which is twice as low as for the deposits with pitchblende-dominated ores. Our study provided the first results for 238U/235U variations in minerals from individual deposits. The largest variations were found in the Oktyabr'skii (Eastern Transbaikalia), Schlema-Alberoda (Erzgebirge), and Shea Creek (Athabasca basin) deposits: 0.70, 0.33, and 0.59‰, respectively. Uranium from the early growth zones of 4–5 mm thick pitchblende spherulitic crusts is isotopically heavier (by 0.22–0.45‰) than uranium from the latest growth zones. A similar isotopic shift in 238U/235U in terms of magnitude (0.31‰) and sense was observed between pitchblende and coffinite overgrowths. The uranium isotopic composition of late pitchblende generations, the products of dissolution and reprecipitation of early phases, is 0.46‰ lighter than that of early pitchblende phases. The character of uranium isotope distribution in pitchblende aggregates is consistent with nuclear-volume-dependent isotope fractionation accompanying U(VI) reduction to U(IV) (Bigeleisen, 1996; Schauble, 2007; Stirling et al., 2007), which causes an enrichment of the U(IV)-bearing solid phase in the heavy isotope 238U. The range of 238U/235U ratios for 11 hydrothermal (high-temperature) deposits (137.703–137.821) lies well within the broader (two-fold) range of values determined for the low-temperature deposits Dybryn in Transbaikalia (Golubev et al., 2013) and Pepegoona in South Australia (Murphy et al., 2014). This can be explained by the fact that the uranium isotopic fractionation associating with U(VI) → U(IV) reduction is accompanied by isotope shifts owing to the long-term interaction of groundwater with early phases within sandstone-type deposits. At the same time, owing to the higher temperatures (by 100–300°C) of formation of hydrothermal deposits compared with sandstone-type deposits, nuclear-volume-dependent uranium isotope fractionation decreases by more than a factor of 2 (Bopp et al., 2009).

The sandstone-type Cu deposits in the Chuxiong Basin occur in the Cretaceous Gaofengsi Formation and the Maotoushan Formation and the orebodies are stratoid and lenticular in form, structurally controlled by their stratigraphical position. Ore structures are dominated by impregnated and striped ones. In addition, it has been observed that copper mineralization is controlled by water-discharge and deformation structures. Orebodies are commonly seen on the gently inclined limbs of the anticline, with the involution front. Copper mineralization shows a distinct zonation. S, Pb isotope and REE data suggest that the copper would stem from the country rocks and the sulfur largely from the lower strata. During diagenesis oxidized Cu-bearing brines derived from the upper parts and reduced brines from the lower parts are involved in metallogenetic reactions in the stress neutral plane, which is the key to the formation of copper deposits in the Chuxiong Basin.

Sandstone-type uranium deposits are the most important uranium producers among various types of uranium deposits. Geologic setting and diagenetic alteration mineralogy of this type of deposits have been well documented. The genesis of sandstone-type uranium deposits have been argued based on geologic and mineralogic studies (Nash et al., 1981). However, it is essentially important to estimate chemical features (Eh, pH) and isotopic compositions of fluids responsible for uranium mineralization and associated diagenetic alteration in order to elucidate genesis of the uranium deposits and diagenetic alteration mechanism. A few such geochemical studies on the sandstone-type deposits have been carried out. In this study, the geochemical features of the diagenetic alteration in the Tone mine area are used to provide constraints on the relationship between uranium mineralization and diagenetic alteration process and the estimation of chemical environments responsible for uranium mineralization.

Geochemical exploration models for sedimentary uranium deposits

Helium emanometry is rapidly becoming a widely employed exploration tool in searching for deeply buried uranium deposits. It has been used in many uraniferous and potentially uraniferous regions including the Colorado Plateau, Texas Gulf Coast, Wyoming, Appalachian orogenic belt, Athabasca basin, and Canadian Northwest Territories. Helium escaping from radioactive mineral deposits can be detected and serves as a guide to the location of uranium ore. This gas is an almost ideal geochemical indicator of uranium because it is inert, stable, slightly End_Page 766------------------------------ soluble in ground fluids, practically non-adsorbable, highly mobile, and a direct product of radioactive decay. The technique can be applied by collecting soil, soil gas, water or bottom sediment samples in reconnaissance, and semi-detailed and detailed arrays under a wide range of environmental conditions. Helium analyses are made by gas-source mass spectrometry. The resultant data are interpreted and presented with the aid of computers. In interpreting the helium data, it is necessary to consider the effect of some parameters which must be determined for each sample. Helium anomalies have been found in near-surface soil and soil gas over known sandstone-type deposits in New Mexico, Texas, and Wyoming; hydrothermal(?) ore in Washington; unconformity-type mineralization in the Athabasca basin; and pegmatitic ore zones in Ontario. Anomalies have also been detected in lake bottom water and sediment overlying these types of deposits and in the groundwater recovered from wells and boreholes located close to them. The results from resurveys over several of these deposits indicate that even though the magnitude of the helium anomalies may vary from season to season, the anomalies themselves persist and hence define the location of the mineralization. This technique therefore seems to offer great promise as an economical indicator of deeply buried uranium eposits in a wide range of geologic environments. End_of_Article - Last_Page 767------------

Uranium in the Texas Gulf coastal plain occurs primarily in two types of deposits: (1) in sandstone-type deposits of Goliad, Oakville, Catahoula, Frio, and upper Jackson, and (2) in Tertiary Wilcox, Yegua-Jackson, and upper Jackson lignite. Total potential resources of uranium in the coastal plain have been estimated to be about 0.25 million tons, ranking third in the United States. Analyses of several thousand samples from the coastal plain show the following results. 1. In the sandstone-type deposits, uranium is both roll type and nonroll type. Most uranium concentrates are in reduced ores. Uranium is closely associated with (a) lignite or disseminated organic matter, (b) clays, particularly smectite, (c) zeolites, particularly with clinoptilolite, and (d) carbonate rocks and calcite. Uranium minerals present are uraninite, coffinite, carnotite. Adsorption of uranium by clays is largely dependent on pH. 2. In lignite, the concentration of uranium decreases with geologic age. Uranium is generally concentrated at the contacts of lignite seams with sandstones or shales rather than in the middle of the seam. Recovery of uranium has been either by surface or in-situ mining. However, development of in-situ leaching has gained new impetus because of the unique situation of south Texas uranium deposits. Results of laboratory tests show that hydrochloric acid is the most effective solvent to recover uranium from either oxidized or reduced sandstone-type ore deposits, and from lignite without the addition of oxidant (e.g., H2O2). End_of_Article - Last_Page 470------------

In the Grants Mineral Belt (N. Mex.) are found accumulations of reduced U(IV) as coffinite and/or uraninite, not only in the immediate proximity of the hematite--pyrite redox interface but in the oxidized hematitic rocks upgradient from the interface and well removed from the interface in pyritiferous sandstone downgradient from the interface. This paper shows that the idea that U in significant quantities may occur downgradient from the main trend of the Grants Mineral Belt should be re-emphasized. (DLC)

U and V in sandstone-type deposits of the western United States apparently have been transported to their present environment from external sources by low-temperature aqueous solutions. In this paper an attempt is made to interpret the characteristics of aqueous solutions capable of transporting significant quantities of U and V through continental sedimentary rocks, and the changes in these characteristics that might result in precipitation of uraninite and other ore minerals in concentrations of ore grade. On the basis of present knowledge, the transportation environment is shown to be that of weakly alkaline, moderately reducing ground water, with an average or larger than average concentration of dissolved carbonate species (H 2 CO 3 +HCO (sub 3-) +CO (sub 3-) ). Precipitation is induced by reduction, probably by carbonaceous material or hydrogen sulfide, or both. U is transported mainly in the form of the highly stable uranyl dicarbonate and tricarbonate complexes. Precipitation results from reduction of hexavalent aqueous U species to form uraninite, reduction of tetravalent V to form montroseite, and fixation of uranyl ions by combination with K ions and quinquivalent V to form the mineral carnotite.

Investigations of the minor- and trace-element content of sulfides associated with uranium ore deposits from sandstone-type deposits have shown that selenium commonly substitutes for sulfur. The Morrison formation and Entrada sandstone of Jurassic age and the Wind River formation of Eocene age seem to be seleniferous stratigraphic zones; sulfides deposited within these formations generally contain abnormal amounts of selenium. The selenium content of the pyrite, marcasite, and chalcocite is much greater than that reported in previously published data.Under the prevailing temperatures and pressures of formation of the Colorado Plateau uranium deposits the maximum amount of Se substituting for S in the pyrite structure was found to be 3 percent by weight. Ferroselite, the iron selenide (FeSe 2 ), was found in two deposits on the Colorado Plateau and it was also established that galena (PbS) forms an isomorphous series with clausthalite (PbSe) in nature.During oxidation of the selenium-bearing sulfides and selenides from the Colorado Plateau and Wyoming, the selenium forms pinkish crusts of either monoclinic or hexagonal native selenium intergrown with soluble sulfates, suggesting that under normal oxidizing conditions native selenium is more stable than selenites or selenates. The above-normal selenium content of these sulfides from sedimentary rocks of Mesozoic and Tertiary age is significant. The high selenium in these sulfides is related to periods of volcanic and intrusive activity penecontemporaneous with the formation of the containing sediments.

A group of claylike silicates from zones of vanadium mineralization in the sandstone-type deposits of the Colorado Plateau have been examined by x-ray powder diffraction methods to determine their mineralogic composition. The materials studied were separated by water elutriation, bromoform separation, or both, and oriented aggregates as well as randomly oriented powders were prepared. A comparison of the x-ray diffractometer patterns of these specimens with roscoelite from Coloma, California (AMNH 13,565) shows that most of the nine samples examined differ from roscoelite in two important ways: by interstratification of mica layers with montmorillonite, and by variation in octahedral substitution of V for A1. The mixed layering of mica-montmorillonite is revealed by distinct changes .in position and intensity of the first-order basal spacings on treatment with ethylene glycol and on heating of the samples to 400 ~ C and 500 ~ C. Variations in octahedral substitutions are inferred from variations in the intensity of the second-order basal spacings relative to the first and third orders. Low relative intensity of the second order is interpreted as indicative of high electron density in the octahedral positions caused by substitution of V for A1. One sample (ALB-34-54) from Placerville, Colorado, shows x-ray characteristics very similar to the roscoelite from California and a chemical composition which gives a sum of 1.969 for octahedrally coordinated cations, indicating that it is a dioctahedral mineral. Two samples from Rifle, Colorado, also show characteristics closely resembling roseoelite although one of these, from an oxidized zone, exhibits a relatively stronger second-order basal spacing, and the suggestion is made that the amount of vanadium substitution is less than in the Coloma, California, or the Placerville, Colorado, material. The rest of the samples show mixed layering to various degrees, with the first-order basal spacing of the untreated material ranging from 10.1 A to 10.5 A. Chlorite is present in at least seven of the samples and is the dominant mineral in at least two of them. Only in the materials from Coloma, California, and Placerville, Colorado, was chlorite absent. The chlorites in two samples show mixed layering with expanding material, although one of these--from Thompson, Utah may be more closely allied to vermiculite than to chlorite. This indeterminant sample differs considerably from the other materials examined in that the mixed-layered mica-montmorillonite as well as the vermiculitic (?) mineral do not survive heating to 500 ~ C. The nonmixed-layered chlorites are characterized by almost equal intensities of the first four basal