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Radon (Rn) and helium (He) gases from uranium decay form distinct anomalies related to buried uranium deposits. In order to trace the geochemical anomalous sources from the volcanic-related uranium deposits in deeply buried areas, systematical Rn contents and He isotope ratios were analyzed from the Daguanchang uranium deposit. The soil gas Rn concentrations above the deep uranium are ten times higher than those in barren areas, indicating that instantaneous Rn content measurements can be used to detect deeply buried uranium. The helium isotope ratios (3He/4He) of the unmineralized samples from the mineralized drill hole (ZK1) are relatively lower and uniform compared to those of the samples from no-mineral drill hole (ZK2). However, the Th and U contents of the drill core samples from ZK1 are slightly lower than those of the samples from ZK2, indicating that the lower 3He/4He ratios in ZK1 are most likely due to the addition of 4He from underlying uranium intervals. The differences in the instantaneous Rn contents are consistent with the variations in the He isotope ratios of the drill core samples. These results demonstrate that soil gas Rn and 3He/4He ratios are useful tracers and can indicate the existence of deeply buried volcanic-related hydrothermal uranium ores. [ABSTRACT FROM AUTHOR]

The reaction between the lixiviant and the minerals in the aquifer of In-situ uranium leaching (ISL) will result mineral dissolution and precipitation. ISL will cause changes in the chemical composition of groundwater and the porosity and permeability of aquifer, as well as groundwater pollution. Previous studies lack three-dimension numerical simulation that includes a variety of minerals and considers changes in porosity and permeability properties simultaneously. To solve these problems, a three-dimensional reactive transport model (RTM) which considered minerals, main water components and changes in porosity and permeability properties in Bayanwula mine has been established. The results revealed that: (1) Uranium elements were mainly distributed inside the mining area and had a weak trend of migration to the outside. The strong acidity liquid is mainly in the mining area, and the acidity liquid dissolved the minerals during migrating to the outside of the mining area. The concentration front of major metal cations such as K+, Na+, Ca2+ and Mg2+ is about 150m away from the boundary. (2) The main dissolved minerals include feldspar, pyrite, calcite, sodium montmorillonite and calcium montmorillonite. Calcite is the most soluble mineral and one of the sources of gypsum precipitation. Other minerals will dissolve significantly after calcite is dissolved. (3) ISL will cause changes in porosity and permeability of the mining area. Mineral dissolution raises porosity and permeability near the injection well. Mineral precipitation reduced porosity and permeability near the pumping well, which can plugging the pore throat and affect recovery efficiency negatively. [ABSTRACT FROM AUTHOR]

The sandstone-type uranium deposit of the Kelulun Depression is the first industrially valuable uranium deposit discovered in the Hailar Basin. This study performed a systematic examination of 17 sandstone samples from the Yimin Formation in the Kelulun Depression based on various analytical techniques. The findings of the current study were synthesized with previous research to investigate the impact of the redox conditions and the tectonic background of the source area, as well as the paleoclimatic evolution of the Yimin Formation on uranium mineralization. The elemental Mo, U/Th, V/Cr, Ni/Co, and V/(V + Ni) ratios indicate that the paleowater was in an oxygen-rich environment during the deposition of the Yimin Formation. Additionally, the C-value, Sr/Cu, Al2O3/MgO, and Rb/Sr ratios indicate that the Yimin Formation was formed in a paleoclimate characterized by arid-to-semi-arid conditions. The geochemical characteristics of the observed elements indicated that the sediment source of the Yimin Formation was mainly felsic rocks from the upper continental crust, the weathering of the rock was weak, and the tectonic background was a passive continental margin. Coffinite is distributed in the form of cementation and stellates within or around pyrite crystals, and uranium-titanium oxide is mostly distributed in an irregular granular distribution in the biotite cleavage fractures of the study area. In summary, the findings of this study reveal that the tectonic settings, provenance, uranium source, paleoclimate, and oxygen-rich paleowater of the Yimin Formation have important geological significance for the large-scale uranium mineralization of the Kelulun Depression. [ABSTRACT FROM AUTHOR]

The large-sized Tarangaole uranium deposit and its neighboring Daying and Nalinggou deposits, located in the northeastern margin of the Ordos Basin, constitutes a major uranium resource base in northern China. In order to further clarify the sedimentary material source, uranium source and regional sediment–tectonic setting of the uranium-fed clastic rocks (i.e., Zhiluo Formation(J2z)) in the district, this paper carried out whole-rock geochemistry, heavy minerals composition and in situ U-Pb dating of detrital zircons for sandstones from the lower section of the Zhiluo Formation. The results have shown that the average chemical differentiation index (CIA) for the host rocks is 73.16 and the chemical weathering degree is moderate. Heavy minerals are mainly composed of ilmenite, garnet, chlorpyrite, zircon, pyrite, apatite, hematite, etc. The U-Pb dating of detrital zircon generally indicates three age peaks, i.e., 260~Ma, 1850~Ma and 2450~Ma, respectively. In conclusion, the source rocks may have been formed at active continental margins, e.g., in a continental margin arc environment. The sedimentary materials mainly come from khondalite series, TTGs, granulite, and mafic–ultramafic intrusive rocks distributed among the Daqing–Ula Mountains and adjacent areas, etc. The Late Paleozoic U-rich intermediate and acidic magmatic rocks spreading over the eastern part of the Ula–Daqing and Wolf mountains have provided the main uranium sources for the formation of major U deposits in the northern Ordos Basin. [ABSTRACT FROM AUTHOR]

The Huayangchuan U-polymetallic deposit in the Qinling Orogen is a newly verified carbonatite-hosted deposit on the southern margin of the North China Craton (NCC) in Central China. Granitic magmatism is extensively developed in the Huayangchuan deposit area and is lacking analysis on the reasons for these situations; however, its ages, petrogenesis, and relationship with uranium mineralization are not well constrained. Zircon U–Pb ages for the hornblende-bearing granite porphyry and medium-fine-grained biotite granites in close proximity to carbonatite rocks are 229.8 ± 1.1 and 135.3 ± 0.6 Ma, respectively. High-K calc-alkaline series and weakly peraluminous Triassic hornblende-bearing granite porphyry are slightly enriched in light rare earth elements (LREE) with flat heavy rare earth element (HREE) patterns, enriched in Ba and Sr, and depleted in Nb, Ta, P, and Ti, i.e., geochemical characteristics similar to those of adakite-like rocks. The Early Cretaceous medium-fine-grained biotite granites are characterized by LREE enrichment and flat HREE patterns, which belong to high-K calc-alkaline series, and metaluminous belong to weakly peraluminous I-type granite, with U and large ion lithophile element (LILE) enrichment and high field strength element depletion. The high initial 87Sr/86Sr ratios and enriched Nd (εNd(t) = −10.7 to −9.5 and −19.9 to −18.9, respectively) and Hf (εHf(t) = −21.8 to −13.0 and −30.5 to −19.0, respectively) isotopes revealed that both granitic rocks from the Huayangchuan deposit mainly originated from lower crustal materials, generated by partial melting of the ancient basement materials of the Taihua Group. Triassic hornblende-bearing granite porphyry is significantly different from the mantle origin of the contemporaneous U-mineralization carbonatite. In combination with tectonic evolution, we argue that the Qinling Orogenic Belt was affected by the subduction of the North Mianlian Ocean during the Late Triassic. The ongoing northward subduction of the Yangtze Craton resulted in crustal thickening, forming large-scale Indosinian carbonatites, U-polymetallic mineralization, and contemporaneous intermediate-acid magmatism. Additionally, due to the tectonic system transformation caused by Paleo-Pacific Plate subduction, intracontinental lithosphere extension and lithospheric thinning occurred along the southern NCC margin in the Early Cretaceous. Intense magma underplating of the post-orogeny created a large number of magmatic rocks. The tremendous heat could have provided a thermal source and dynamic mechanism for the Yanshanian large-scale U-polymetallic mineralization events. [ABSTRACT FROM AUTHOR]

The Jurassic Zhiluo Formation in the western Ordos Basin is known for hosting economically significant sandstone-type uranium deposits. However, the understanding of sediment sources for this formation, crucial for guiding uranium exploration, has been a subject of controversy. This study aims to address this issue by presenting a systematic dataset derived from detrital zircons found in the uranium-bearing sandstones of the Zhiluo Formation. The dataset includes U‒Pb dating, trace element analyses, and in-situ Hf isotope compositions. The detrital zircons analysed are predominantly of magmatic origin, as indicated by a Th/U ratio greater than 0.4. Their U‒Pb ages can be broadly categorized into a predominant population ranging from 170 to 500 Ma, with a peak ca. 300 Ma. Additionally, there are two minor age populations: 1600–2050 Ma (peaking at ca. 1850 Ma) and 2300–2650 Ma (peaking at ca. 2500 Ma). The εHf(t) values of these zircons exhibit a range from −27 to 7, concentrating mostly from −16 to 5. Importantly, none of them aligns above the deficit mantle evolutionary line in an εHf(t) vs. age covariant diagram. A comprehensive comparison of the analytical U‒Pb ages and Hf isotopic results with previously reported data from adjacent geological units surrounding the western Ordos Basin suggests that the primary provenance supply area for the sandstones is the Alxa Block, particularly the uranium-rich felsic rocks within it. Minor contributions are inferred from the Yinshan Block and the Qilian Orogenic Belt. The northwestern region of the study appears to be the primary prospect area for uranium exploration, and we have proposed effective measures to refine the exploration target area and enhance exploration efficiency. Overall, the study provided crucial insights into deducing provenance supply areas and transport paths, with implications for uranium exploration in sedimentary basins worldwide. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) is widespread in uranium (U) hosting aquifer, a key substance affecting CO2 + O2 in situ leaching (ISL) of U by consuming injected O2. However, molecular composition and molecular transformation of DOM are poorly understood in this aquifer during the U mining. To address this issue, Fourier transform ion cyclotron resonance mass spectrometry was applied to investigate DOM molecules in groundwater samples and rock samples collected from a U mining aquifer. The high proportion of labile tyrosine‐like component and BIX value in monitoring wells (BM) indicated the biological origin of DOM. CHOS and aliphatic were the major components of water‐soluble organic matter (WSOM) in U‐bearing rocks, but CHO and highly unsaturated structures with high oxygen (HUSHO) were the main components of DOM in BM. The ISL led to the release of WSOM and the oxidation of DOM, which accounted for 24.5%–57.4% and 39.1%–65.7% of expected DOM, respectively. Potential molecular transformations (PMTs) results showed that the intragroup transformations dominated, and remarkable transformations from CHON and CHONS to CHO occurred during ISL. The positive net PMTs of condensed aromatic structure (CAS), aromatic structures (AS), and aliphatic suggested that they were transformed from HUSLO and HUSHO. A gradual decrease in (DBE−O)/Cwa and a gradual increase in NOSCwa indicated that the saturated degree and oxidation state of DOM increased during mining. This work successfully identified molecular characteristics of DOM in U hosting aquifer, and proposed a paradigm of DOM transformation pathways during ISL. Plain Language Summary: Dissolved organic matter (DOM) was a key substance widely distributed in Uranium (U) hosting aquifer, however, the characteristics and its potential molecular transformation during neutral in situ leaching (ISL) remained unclear. Here, 13 groundwater samples and 5 rock samples were collected from the Qianjiadian U deposit, a sandstone‐type U deposit by neutral ISL in China. Groundwater chemistry, 3D fluorescence spectroscopy, FT‐ICR MS, and carbon isotope approaches were employed to investigate the characteristics of DOM, identify and quantify the processes affecting the composition of DOM during ISL. Spectral and molecular characteristics of DOM revealed the biological origin of DOM and the biological activity in U‐hosting aquifers. CHOS and aliphatic were the major components of water‐soluble organic matter (WSOM) in U‐bearing rocks. The release of WSOM (24.5%–57.4%) and oxidative degradation of DOM (39.1%–65.7%) together controlled the composition of DOM during ISL. The gradual decrease of (DBE−O)/Cwa and gradual increase of NOSCwa indicated that the saturated degree and oxidation state of DOM increased as mining. This work improves our understanding of molecular characteristics of DOM in U hosting aquifer and molecular transformation pathways of DOM during ISL. [ABSTRACT FROM AUTHOR]

The DL deposit is a typical tabular-shaped U deposit hosted in sandstones of the Upper Cretaceous Yaojia Formation in the southwestern Songliao Basin, northeast China. Owing to its recent discovery, the origin of the deposit remains unclear. In this study, mineralogical and geochemical data were used to constrain the genesis of the DL deposit. Two sources of U were recognized: (1) pre-ore U enrichment in the Yaojia Formation during diagenesis; and (2) the provenance of the Yaojia Formation, which comprises late Permian–Early Cretaceous granitic rocks from the southern Great Xing'an Range and northern margin of the North China Craton, rather than the oils and diabase dikes in the study area. Mineralogical and geochemical characteristics indicate that organic matter (OM) in the Yaojia Formation was derived mainly from plant debris and hydrocarbons. In situ S isotope data for pyrite from the ore-bearing sandstones show that most of the pyrite has similar δ34S values (−43.8‰ to −20.6‰) to those of pyrite associated with bacterial sulfate reduction (BSR). The pyrite is often typically replaced and/or overgrown by pitchblende, which has a high P2O5 content (0.07–1.64 wt.%), indicative of a genetic relationship between BSR and U mineralization. The geological, mineralogical, and geochemical features suggest that the U mineralization in the DL deposit was mainly associated with BSR. [ABSTRACT FROM AUTHOR]

Sandstone-hosted uranium deposits are indeed significant sources of uranium resources globally. They are typically found in sedimentary basins and have been extensively explored and exploited in various countries. They play a significant role in meeting global uranium demand and are considered important resources for nuclear energy production. Erlian Basin, as one of the sedimentary basins in northern China, is known for its uranium mineralization hosted within sandstone formations. In this research, machine learning (ML) methodology was applied to mineral prospectivity mapping (MPM) of the metallogenic zone in the Manite depression of the Erlian Basin. An ML model of 92% accuracy was implemented with the random forest algorithm. Additionally, the confusion matrix and receiver operating characteristic curve were used as model evaluation indicators. Furthermore, the model explainability research with post hoc interpretability algorithms bridged the gap between complex opaque (black-box) models and geological cognition, enabling the effective and responsible use of AI technologies. The MPM results shown in QGIS provided vivid geological insights for ML-based metallogenic prediction. With the favorable prospective targets delineated, geologists can make decisions for further uranium exploration. [ABSTRACT FROM AUTHOR]

Acid in situ leaching (ISL) is a common approach to the recovery of uranium in the subsurface. In acid ISL, there are numerous of chemical reactions among the injected sulfuric acid, groundwater, and porous media containing ore layers. A substantial amount of radioactive elements including U, Ra, Rn, as well as conventional elements like K, Na, and Ca, and trace elements such as As, Cd, and Pb, are released into the groundwater. Thus, in acid ISL, understanding the transport and reactions of these substances and managing pollution control is crucial. In this study, a three-dimensional reactive transport modeling (RTM) using TOUGHREACT was built to investigate the dynamic reactive migration process of UO22+, H+, and SO42− at a typical uranium mine of Bayan-Uul. The model considering the partial penetration through wellbore in confined aquifer and complex chemical reactions among main minerals like uranium, K-feldspar, calcite, dolomite, anhydrite, gypsum, iron minerals, clay minerals, and other secondary minerals. The results show that after mining for one year, from the injection well to the extraction well, the spatial distribution of uranium volume fraction does not consistently increase or decrease, but it decreases initially and then increases. After mining for one year, the concentration front of UO22+ is about 20 m outside the mining area, the high concentration zone is mainly inside the mining area. The concentration front of H+ is no more than 50 m. SO42− is the index with the highest concentration among the three indexes, the concentration front of SO42− is no more than 100 m. The concentration breakthrough curve of the observation well 10 m from the mining area indicates that the concentrations of the three indicators began to significantly rise approximately after mining 0.05 years, reached the maximum value after mining 0.08 to 0.1 years, and then stabilized. The parameter sensitivity of absolute permeability and specific surface area of minerals shows that the concentration of H+ and SO42− is positively correlated with absolute permeability. The concentration of H+ is negatively correlated with the specific surface area of calcite, anhydrite, K-feldspar, gypsum, hematite, and dolomite. The concentration of SO42− is positively correlated with the specific surface area of K-feldspar and Hematite, and negatively correlated with the specific surface area of calcite, anhydrite, gypsum, and dolomite. The influence analysis of pumping ratio and non-uniform injection ratio shows that the non-uniform injection scheme has a more significant impact on pollution control. The water table, streamline, capture envelope, and the concentration breakthrough curve of five schemes with different pumping ratios and non-uniform injection ratio were obtained. The water table characteristics of five schemes shown that increase in the pumping ratio and the non-uniform injection ratio, the water table convex near the outer injection well is weakened and the groundwater depression cone near the pumping well is strengthened. This characteristic of water table exerts a notable retarding influence on the migration of pollutants from the mining area to the outside. For the scheme with a pumping ratio is 0 (the total pumping flow rate is equal to the total injection flow rate) and a non-uniform injection ratio is 0 (the flow rate of inner injection well Q1,Q2,Q3 is equal to the flow rate of outer injection well Q4,Q5,Q6), the streamline characteristics shown that a segment of the streamline of is diverging from inner region to the outer region. For other schemes, the streamline exhibits a convergent feature. It is indicated that by increasing the pumping ratio and non-uniform injection ratio, a closure flow field can be established, confining the groundwater pollutants resulting from mining within the capture envelope. Hence, the best scheme for preventing pollution migration is the scheme with a pumping ratio is 0 (the total pumping flow rate is equal to the total injection flow rate) and a non-uniform injection ratio is 0.1 (the flow rate of inner injection well Q1,Q2,Q3 is 10% more than the flow rate of outer injection well Q4,Q5,Q6). In this scheme, the optimal stable concentration of UO22+, H+, and SO42− at the observation well obtained by RTM is lower than other schemes, and the values are 0.00316 mol/kg, 2.792 (pH), and 0.0952 mol/kg. The inner well injection rate is 194.09 m3/d, the outer well injection rate is 158.89 m3/d, and the pumping rate is 264.00 m3/d. Numerical simulation analysis suggests that a scheme with a larger non-uniform injection ratio is more conducive to the formation of a strong hydraulic capture zone, thereby controlling the migration of pollutants in the acid ISL. A reasonable suggestion is to adopt non-uniform injection mining mode in acid ISL. [ABSTRACT FROM AUTHOR]

Rhenium is an extremely rare critical metal element in Earth's continental crust. Owing to its extremely high melting point and heat-stable crystalline structure, rhenium is an essential component of alloy materials used in high-performance aircraft engines. Demand for rhenium resources is therefore growing. Currently, most rhenium is produced as a byproduct of molybdenum mining in porphyry copper–molybdenum deposits. Research has therefore focused on the enrichment characteristics of rhenium in this type of deposit, with little attention paid to rhenium in other types of deposits. This study reports the occurrence state and enrichment mechanism of rhenium in the Qianjiadian sandstone-type uranium deposit in the Songliao Basin, Northeast China. Sequential extraction revealed that the average proportions of different forms of rhenium are as follows: water-soluble (57.86%) > organic-sulfide-bound (13.11%) > residual (12.26%) > Fe/Mn oxide-bound (10.67%) > carbonate-bound (6.10%). Combining mineralogical analysis techniques such as SEM-EDS, EMPA, and XRD, it has been established that rhenium does not occur as a substitute in sulfides (e.g., molybdenite) or uranium minerals in various types of deposits. Instead, it is mainly adsorbed onto clay minerals and Fe-Ti oxides, and in a small number of other minerals (pyrite, organic matter, and pitchblende). Rhenium is similar to redox-sensitive elements such as uranium and vanadium, and it is transported in a water-soluble form by oxidizing groundwater to the redox transition zone for enrichment. However, unlike uranium, which generally forms as uranium minerals, rhenium is mainly adsorbed and enriched onto clay minerals (kaolinite and interlayered illite–smectite). Most of the rhenium in sandstone-type uranium deposits occurs in an ion-adsorption state, and is easily leached and extracted during in-situ leaching mining of uranium ores. This type of deposit demonstrates excellent production potential and will become a crucial recoverable resource for future rhenium supply. [ABSTRACT FROM AUTHOR]

In order to achieve a breakthrough in the exploration of uranium orebodies in the Changjiang area of Guangdong province in China, the geo-electrochemical exploration method is used for mineral resource prediction. The logarithmically and isometric log-ratio (ilr) transformations are applied to the geo-electrochemical data in this study area to extract geochemical anomalies. The relationship between element associations and mineralization is revealed through descriptive statistical analysis and further biplot analysis. Then, the energy spectrum density–area fractal model (S-A model) is used to identify geochemical backgrounds and anomalies. The results show that: (i) the logarithmically and ilr-transformed data are more uniform, and they more or less obey the rules of normal distribution; (ii) the biplot shows that the ilr-transformed data eliminates the closure effect, and the robust principal component analysis (RPCA) has a better indicative significance for element associations—PC1 reveals the mineralization element association dominated by U and the multiple periods of hydrothermal activity; (iii) the S-A method could extract the local anomalies from different geochemical backgrounds, which indicates mineralization is more reliable. Finally, four favorable prospecting targets are delineated based on the geological and geochemical indicators. [ABSTRACT FROM AUTHOR]

Uranium mining activities have contributed to the distribution and uptake of radionuclides, which have increased the active concentrations of natural radionuclides in environmental media, causing elevated human health risks. The present study aims to assess the spatial distribution characteristics of natural radionuclides in the surface soils and river sediments of the typical granite uranium mining area in South China, as well as investigate the geochemical features of natural radionuclides in the soil and sediments to understand their migration processes. The activity concentrations for 238U, 226Ra, 232Th, and 40K ranged from 17–3925 Bq/kg, 50–1180 Bq/kg, 29–459 Bq/kg, and 240–1890 Bq/kg, respectively. The open-pit mining areas and tailings pond locations exhibited the highest concentrations of activity for all these radionuclides. This distribution points to an elevated potential health risk due to radiological exposure in these specific areas. Additionally, the values of radium equivalent activity (Raeq) and annual gonadal dose equivalent (AGDE) in those areas were higher than the limits recommended by ICRP (2021). 238U and 226Ra have a significant correlation (0.724), and the cluster analysis was showing a statistically meaningful cluster below 5 indicated that they have similar behavior during parent rock weathering and watershed erosion, and the distribution of 232Th and 40K were influenced by the addition of rock types. The activity ratios of 226Ra/238U, 226Ra/232Th, 238U/40K, and 226Ra/40K variation indicated that 40K more mobile than 226Ra and 238U, U(VI) was reduced to U(IV) by organic matter in the downstream area and re-entered into the sediment during the sediment surface runoff in the small watershed of the uranium ore open-pit mining area. Therefore, it is necessary to further seal up and repair the tailings landfill area. [ABSTRACT FROM AUTHOR]

Uranium extraction through the in situ leaching method stands as a pivotal approach in uranium mining. In an effort to comprehensively assess the repercussions of in situ uranium leaching on groundwater quality, this study collected 12 representative groundwater samples within the Bayan-Uul mining area. The basic statistical characteristics of the water samples showed that the concentrations of SO42− and total dissolved solids (TDS) were relatively high. Through the use of cluster analysis, the water samples were categorized into two distinct clusters. Seven samples from wells W-d, W-u, N01, W10-2, W08-1, W10-1, and W13-1, situated at a considerable distance from the mining area, were grouped together. Conversely, five samples from wells W08-2, W13-2, W01-1, W02-2, and the pumping well located in closer proximity to the mining area, formed a separate cluster. A decision tree-based machine learning approach was employed to discern the influence of various hydrochemical indicators in forming these clusters, with results indicating that SO42− exerts the most substantial influence, followed by Ca2+. The mineral saturation indices from geochemical modeling indicated that, as the distance from the mining area increased, the trend of calcium minerals changed from dissolution to precipitation; iron minerals were in a precipitation state, and the precipitation trend was gradually weakening. In light of these findings, it is clear that in situ uranium leaching significantly impacted the groundwater in the vicinity of the mining area. The prolonged consumption of groundwater sourced near the study area, or its use for animal husbandry, poses potential health risks that demand heightened attention. [ABSTRACT FROM AUTHOR]

Uranium (U) contamination in groundwater of the uranium mines exploited using the in situ leaching (ISL) technology (also referred to as the ISL uranium mines) has attracted wide international attention. Since the adsorption of U in groundwater by aquifer media influences the migration scope of U, understanding the U adsorption by aquifer media is of great significance for accurately predicting the influencing scope of ISL uranium mines on groundwater. This study collected sandstone samples from the ore-bearing aquifer outside a typical mining area in a uranium mine exploited using the acid ISL (AISL) technology (also referred to as an AISL uranium mine) in northern China. Using these sandstone samples, this study conducted batch adsorption experiments and column experiments of U to reveal the characteristics and major influencing factors of U adsorption under different conditions. The results show that the adsorption of U by sandstones in the ore-bearing aquifer outside a mining area satisfies the pseudo-second-order kinetic equation and the linear isothermal adsorption model. In the batch U adsorption experiments, the adsorption efficiency and capacity for U reached maxima of 77.45% and 0.069 mg/g at pH 7, respectively. As shown by column experiments, the sandstones showed a significant increase in the U adsorption and retardation as pH increased. The SO42− concentration has minor effects on U adsorption under experimental conditions. Sandstones from different monitoring wells exhibited different U adsorption characteristics. Sandstone cores with relatively high contents of clay minerals such as illite showed strong U adsorption. Under the same experimental conditions, the U distribution coefficient Kd (6.91 × 10–2 L/g) obtained from column experiments is much less than that (0.14 L/g) obtained from the batch U adsorption experiments. These results suggest that it is necessary to take into account the U adsorption and retardation by aquifer media in predicting the impacts of ISL uranium mines on the groundwater environment. [ABSTRACT FROM AUTHOR]

The Hailijin (HLJ) sandstone-type uranium deposit was newly discovered in the southwestern Songliao Basin in recent years. Different from the roll-front orebody of the sandstone-type uranium deposits with (phreatic oxidation) interlayer redox origin (or phreatic oxidation), the orebody of the HLJ uranium deposit is tabular-shaped and multi-stratiform. The kaolinite content in ore-controlling gray sandstones is significantly higher than that in oxidized sandstones, which have the highest kaolinite content in the less oxidized zone of sandstone-type uranium deposits in the basins of western China (such as Yili Basin and Turpan-Hami Basin). In order to identify the properties of ore-forming fluids and the genesis of the tabular-shaped orebody of the HLJ uranium deposit, trace element, scanning electron microscopy (SEM), X-ray diffraction (XRD), and uranium mineral electron probe (EPMA) analyses of different geochemical zone sandstones in ore-bearing strata were carried out. As a result, kaolinite, illite, and illite/smectite formation (I/S) appear to alternate with one another in ore-controlling gray sandstones, and the content of kaolinite is the highest in ores. SEM analysis also suggests that uranium minerals are commonly adsorbed on the surface of foliated and vermicular kaolinite or trapped within micropores of kaolinite. In this case, it is inferred that kaolinite in ore-controlling gray sandstones is of epigenetic origin, and the ore-bearing sandstones have undergone at least one transformation of acidic fluids. Combined with the regional paleoclimate, regional tectonics, and regional burial history, it is concluded that the acidic fluid originated from the uranium-rich source rocks of the Lower Cretaceous Jiufotang Formation, and the tabular-shaped orebody of the HLJ uranium deposit was formed by exudative metallogeny. When the uranium-rich acidic organic fluids exuded upward from deep levels along the faults to the target strata, the solubility of uranium and other polymetallic elements decreased because of the decrease in temperature and pressure, and uranium eventually precipitated and accumulated in sandstones with suitable permeability and porosity. However, it cannot be ruled out that the superimposition and transformation of uranium mineralization was caused by phreatic oxidation or local interlayer redox during the interval of exudative metallogeny. [ABSTRACT FROM AUTHOR]

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Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coal is usually found in many sandstone-hosted uranium deposits in western China. However, it remains unclear whether coal organic matter is related to the mineralization of uranium in sandstone. In this study, the organic matter of coal containing lenticular carbon plant strips and carbon clastics was analyzed in different alteration zones in the Daying sandstone-hosted uranium deposit located in the northern Ordos Basin. According to geological and geochemical characters, Daying sandstone can be classified into three alteration zones: the oxidation zone, the transition zone, and the reduction zone. The results are as follows. Firstly, the maceral organic matter of the coal at Daying is mostly vitrinite, indicating the characters of humic coal. The maturity of the organic matter is low, which is in the transitional evolution stage of immature lignite or lignite-long-flame coal. Secondly, the kerogen is mainly type III (humic type), which can be easily transformed into humic acid with a strong adsorption capacity for uranium. Thirdly, the vitrinite reflectance (Ro) of the coal organic matter in the transition zone is higher than that of the other alteration zones. Meanwhile, there are bright white bands in the microscopic components of the organic matter of the coal in the transition zone (mineralized zone) and a certain composition of the sapropelite has strong fluorescence. All three aforementioned phenomena are related to the radioactivity of uranium, and each of them possesses the potential for application in mineral exploration. Fourthly, the extraction and separation of humic substances indicates that humic acid plays a key role in organic matter-related uranium mineralization. In the transition zone, uranium can co-precipitate as a humate, and the transition zone's organic carbon content increases. Therefore, the organic matter in coal contributes to sandstone-hosted uranium mineralization, providing a further guide to prospecting methodologies. [ABSTRACT FROM AUTHOR]

With the gradual depletion of high-grade uranium resources in southern China, it is necessary to recover uranium from low-grade complex and refractory uranium resources However, the traditional acid mining process has certain drawbacks such as high acid consumption, low uranium recovery, and potential environmental pollution. There is an urgent need to develop new technologies for the extraction of refractory uranium ores. A tonne-scale column bioleaching for low-grade refractory vocanogenic uranium ore containing brannerite and pitchblende was performed. The uranium leaching efficiency reached 85.86% with an acid consumption of only 10.15% after leaching for 130 d. In the bioleaching stage, the Fe3+ concentration had a good correlation with the Eh value; the higher the Fe3+ concentration, the better was the leaching of uranium. The solution pH was kept below 2.5 during the leaching process, which avoided the precipitation of iron and ensured a higher Fe3+ concentration in the solution. Efficient leaching of uranium from UTi2O6 and UO2 was achieved through oxidation of Fe3+ and the action of microorganisms. The results may provide technical support for industrial leaching of low-grade volcanogenic uranium deposits. [ABSTRACT FROM AUTHOR]

The Huayangchuan uranium deposit, located in the west of the Xiaoqinling belt on the southern margin of the North China Craton, is a large U–Nb–Pb deposit accompanied with rare–earth elements. The Huayangchuan uranium deposit, discovered in the 1950s, has long been known as a carbonatite–type uranium deposit. Recently, new geological work has found uranium mineralization in many granitic pegmatite veins in the Huayangchuan deposit and adjacent areas. Here, we report a systematic investigation of the petrography, whole–rock geochemistry, zircon U–Pb ages, and in situ Lu–Hf isotopic characteristics of newly discovered U–rich granitic pegmatite veins in the west of Huayangchuan deposit. The petrological results showed that the lithology of the samples is granite pegmatite. The U–Pb ages of zircon were 1826.3 ± 7.9 and 1829 ± 11 Ma. Microscopically, the paragenetic characteristics of zircon, betafite, and uraninite exist in the intergranular fissures of K–feldspar and quartz, reflecting metallogenic phenomena in the rock formation process. Almost all whole–rock samples were rich in SiO2 (64.37−70.69 wt.%), total alkalis (K2O + Na2O = 8.50–10.30 wt.%), and Al2O3 (12.20–14.41 wt.%) but poor in TiO2 (0.23–0.73 wt.%), MgO (0.38–0.90 wt.%), CaO (1.23–2.22 wt.%), P2O5 (0.14–0.83 wt.%), and MnO (0.04–0.57 wt.%). Additionally, they showed enrichment of LILEs (such as Rb, Ba, Th, U, and K), depletion of HFSEs (such as Ta, P, Ti, and Hf), and no alkaline dark minerals, and the characteristics are intraplate A1–type granite. The A1–type granite displayed low zircon εHf(t) values (−19.42–−15.02) with zircon two–stage Hf model aged 3.10–2.76 Ga, indicating that the U–rich granitic pegmatite was derived predominantly from partial melting of the ancient continental crust (such as the early Taihua group formed in Archean–Neoarchean). Combined with the above results and regional geological data, the U–rich granitic pegmatite discovered in the Huayangchuan deposit was formed in a post–collisional regime after the Luliang movement in the late Paleoproterozoic. This study suggests that future uranium prospecting work in this area should focus on late Paleoproterozoic U–rich granitic pegmatites. [ABSTRACT FROM AUTHOR]

Allanite is an important rare earth element (REE)-U-bearing mineral in granites, and it can act as a metal source for the formation of some hydrothermal uranium deposits and ion-adsorption REE deposits. To investigate the potential of allanite as a mineral probe of granite-related uranium mineralization processes and the formation of ion-adsorption REE deposits, we present textures, geochemistry, and in situ U-Pb isotope data for allanite from the fertile Changjiang granite associated with the Changjiang uranium ore field and barren Jiufeng granite in the Zhuguangshan batholith, South China. Alteration of allanite in the Changjiang granite is characterized by the altered domains with lower backscattered electron (BSE) intensities than the unaltered domains and replacement by other secondary minerals such as REE fluorocarbonates, calcite, fluorite, thorite, clay minerals, quartz, chlorite, and epidote. Crystals from the Jiufeng granite were partly replaced by the altered domains appearing darker in BSE images and minor REE fluorocarbonates. The darker domains of the Changjiang and Jiufeng allanite grains have higher Fe3+/(Fe3++Fe2+) ratios and U concentrations than those of the brighter domains, indicating that the alteration of allanite was probably related to more oxidized fluids. This study suggests that the Changjiang granite might have been subjected to the influx of F- and CO2-bearing fluids. The brighter domains of the Changjiang and Jiufeng allanite grains have weighted mean 207Pb-corrected 206Pb/238U ages of 156.7 ± 4.3 Ma and 161.6 ± 5.3 Ma, respectively, consistent with the corresponding zircon 206Pb/238U ages of 156.1 ± 1.4 Ma and 159.8 ± 1.8 Ma. The darker domains of the Changjiang allanite grains yield a weighted mean 206Pb/238U age of 141.4 ± 5.6 Ma, which overlaps within error the timing of a uranium mineralization event (~140 Ma) in the Changjiang uranium ore field and the age of a crustal extension event (140–135 Ma) in South China. The BSE images and elemental maps reveal that rare earth elements such as La and Ce have been released from the Changjiang allanites during alteration and were precipitated as REE-fluorocarbonates that are susceptible to chemical weathering, which sets the stage for the formation of an ion-adsorption REE deposit. Our study suggests that the regional crustal extension might have played an important role in the formation of both granite-related uranium and ion-adsorption REE deposits in South China, as it could have triggered alteration or breakdown of REE-U-bearing minerals in source rocks. [ABSTRACT FROM AUTHOR]

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In this paper, the typical sand-conglomerate uranium ore in north China was taken as the research object. The uniaxial compression and tensile tests of sand-conglomerate specimens under natural status and acidic solution status were used to research the compressive strength, tensile strength, Young's modulus, cohesion and internal friction angle. Focusing on this type of uranium deposit, during the underground design of the in-situ leaching mining method, the three-dimensional finite element method was used to conduct a numerical simulation of the liquid collecting tunnel with different structural parameters of 10 m×2 m, 3 m×2 m, 2 m×2 m, and comprehensively analyse the vertical displacement, principal stress and plastic deformation zone changes of the tunnelbefore and after leaching. Based on the results, influenced by an acidic aqueous solution, the grain of the conglomerate became soft and secondary pores appeared, resulting in the superimposed effect of physical damage and chemical damage. Macroscopically, an obvious decrease was witnessed in mechanical property. Based on the stability and economy factor of three scenarios before and after leaching, the scenario was recommended as the experimental testing scenario, specifically, two longitudinal collecting tunnel were arranged along the strike of the orebody, with the size of 3 m×2 m and the width of the middle pillar of 4 m. The results of the numerical simulation are significant in guiding the design of underground in-situ leaching technology and determining the structural parameters of the deposit. [ABSTRACT FROM AUTHOR]

Sandstone type uranium is the most valuable and has the most potential for mining among the known uranium deposits. In the process of forming, the hydrolytic migration and enrichment of uranium require special basin sedimentary environment and tectonic background. Therefore, the mineralization process of sandstone type uranium deposits has certain layering characteristics and distribution rules in the underground vertical depth space. It is important to mine the spatial distribution characteristics of vertical uranium-bearing layers, and thus, reconstruct the three-dimensions of uranium orebodies. In this paper, according to the metallogenic law and distribution characteristics of sandstone type uranium in the underground vertical space, a nonlinear uranium-bearing layers identification (NULI) method of sandstone type uranium is proposed by using different types, resolutions and scales of borehole data. Then, the depth of uranium mineralization for the Daying uranium deposit within northern Ordos Basin is identified accurately and the spatial distribution characteristics of the uranium-bearing layer on the exploration line are obtained. Finally, the occurrence mode of the underground uranium orebodies are presented by using three-dimensional reconstruction analysis. It provides a basis for the prediction, exploration and mining of sandstone type uranium deposits within the Ordos Basin. [ABSTRACT FROM AUTHOR]

As a valuable mineral resource, uranium is extensively utilized in nuclear power generation, radiation therapy, isotope labeling, and tracing. In order to achieve energy structure diversification, reduce dependence on traditional fossil fuels, and promote the sustainable development of energy production and consumption, research on the metallogenic mechanisms and related development technologies of uranium resources has been one of the focuses of China's energy development. Sandstone-type uranium deposits make up approximately 43% of all deposits in China, making them the most prevalent form of uranium deposit there. Sandstone-type uranium deposits and hydrocarbon resources frequently coexist in the same basin in China. Therefore, this study summarizes the spatial and chronological distribution, as well as the geological characteristics, of typical sandstone-type uranium deposits in China's hydrocarbon-bearing basins. From the perspectives of fluid action, geological structure, and sedimentary environment, the metallogenic mechanisms of sandstone-type uranium deposits in hydrocarbon-bearing basins are explored. According to the research, the rapid reduction effect of oil and gas in the same basin is a major factor in the generation of relatively large uranium deposits. Additionally, ions such as CO32− and HCO3− in hydrothermal fluids of hydrocarbon-bearing basins, which typically originate from dispersed oil and gas, are more conducive to uranium enrichment and sedimentation. This study provides guidance for efficient sandstone-type uranium deposit exploration and production in hydrocarbon-bearing basins and helps to achieve significant improvements in uranium resource exploitation efficiency. [ABSTRACT FROM AUTHOR]

The relationship between PM2.5 concentration and typical metal elements around a uranium deposit in eastern China was analyzed. The correlation between PM2.5 concentration and metal content in PM2.5 is generally poor, while the correlation between metal elements is generally good. The analysis shows that PM2.5 concentration and U content show the same trend with seasonal replacement, and Th content has a positive correlation with PM2.5 concentration on the whole. PM2.5 concentration was positively correlated with the content of Pb, Cd and Al. There is no obvious relationship between PM2.5 concentration and Ti content, and other theoretical explanations need to be studied. [ABSTRACT FROM AUTHOR]

Under the new development philosophy of carbon peaking and carbon neutrality, CO2 and O2 in situ leaching (ISL) has been identified as a promising technique for uranium mining in China, not only because it solves carbon dioxide utilization and sequestration, but it also alleviates the environmental burden. However, significant challenges exist in assessment of CO2 footprint and water‐rock interactions, due to complex geochemical processes. Herein this study conducts a three‐dimensional, multicomponent reactive transport model (RTM) of a field‐scale CO2 and O2 ISL process at a typical sandstone‐hosted uranium deposit in Songliao Basin, China. Numerical simulations are performed to provide new insight into quantitative interpretation of the greenhouse gas (CO2) footprint and environmental impact (SO42–) of the CO2 and O2 ISL, considering the potential chemical reaction network for uranium recovery at the field scale. RTM results demonstrate that the fate of the CO2 could be summarized as injected CO2 dissolution, dissolved CO2 mineralization and storage of CO2 as a gas phase during the CO2 and O2 ISL process. Furthermore, compared to acid ISL, CO2 and O2 ISL has a potentially smaller environmental footprint, with 20% of SO42– concentration in the aquifer. The findings improve our fundamental understanding of carbon utilization in a long‐term CO2 and O2 ISL system and provide important environmental implications when considering complex geochemical processes. [ABSTRACT FROM AUTHOR]

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Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Uranium is an important strategic resource, and its safe and efficient development and utilization are of great significance to ensuring a nation's energy supply and strategic security. Sandstone-type uranium ore is commonly mined by CO2 + O2 in situ leaching, for which understanding the coupling mechanism between the hydrodynamic and chemical fields is key to predicting uranium leaching. This study focused on a coal–uranium ore deposit in China. A convection and dispersion model of the solute transport by in situ leaching was constructed in COMSOL, and a thermodynamic model of CO2 + O2 in situ leaching in sandstone-type uranium ore was constructed in PHREEQC. The two models were coupled to simulate the reactive transport and dynamic leaching processes of uranium by CO2 + O2 in situ leaching. A sensitivity analysis was performed to quantitatively analyze the effects of different model parameters on the uranium leaching efficiency and uranium contamination remediation. The results showed that the coupled model could simulate and predict the reaction and transport of uranium. The sensitivity analysis indicated that the production rate and the injected CO2 and O2 concentrations are the key parameters that control the uranium leaching efficiency, followed by the formation permeability and injection rate. The uranium leaching efficiency does not increase monotonically with the formation permeability and production rate. The results also indicated that natural dilution is insufficient for remediating uranium-contaminated groundwater, but the remediation efficiency can be improved by increasing solution extraction. The results of this study can be used to develop guidelines for the safe and efficient development and utilization of uranium ore while protecting the ecological environment. [ABSTRACT FROM AUTHOR]

Hydrothermal alteration records fluid–rock interactions and can therefore be used to constrain element migrations during mineralization. Although hydrothermal alteration is widely developed in hydrothermal vein-type uranium deposits in South China, consideration of elemental mass changes during alteration has not been examined. The Egongtang uranium deposit in the central Nanling Range is mainly hosted by the Qingzhangshan granite in South China, and was strongly altered by K-feldspar, quartz, chlorite, illite, haematite, pyrite and carbonates. The alteration section can be divided into five horizontal zones: fresh granite (Zone V), a distal alkaline alteration zone (Zone IV), a chlorite-rich zone (Zone III), a close-to-ore sericite/illite alteration zone (Zone II) and a central mineralization zone with strong haematitization (Zone I). Whole-rock geochemistry of the altered samples indicates that from Zone IV to Zone I, the content of SiO2 and U increases significantly. The mass gains of SiO2, MgO and Fe2O3 were proportional to the concentration of U. The content of trace elements (such as Ba, K, La, Ce, Pr, Sr, P, Eu, etc.) gradually decreases from Zone V to Zone I. The rare earth elements manifest a decrease in light rare earth elements and a slight increase in heavy rare earth elements accordingly from Zone V to Zone I. This study shows that the ore materials of the Egongtang deposit were mainly derived from the Qingzhangshan granites. In the early alkali alterations, large amounts of U were partitioned into the fluids. In the ore-forming stage, ores precipitated accompanied by acid metasomatism such as chloritization, haematitization and carbonation. [ABSTRACT FROM AUTHOR]

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Since the 1990s, sandstone-type uranium in the northern basin of China has become the main target for mining. Uranium mining can cause a series of impacts on the environment. A conceptual model of the geo-environment for sandstone-type uranium in northern China was described, which covers the changes in the geo-environmental characteristics in the natural state, in the mining process, during decommissioning and after treatment. Sandstone-type uranium is mainly distributed in the Songliao, Erlian, Ordos, Turpan–Hami and Ili Basins, which have arid climates and poor stratum permeability. Pitchblende is the main uranium-bearing mineral and is associated with iron, copper, coal, organic matter and other minerals. The mineral often has a low ore grade (0.01–1.0%) and high carbonate content (2–25%). Uranyl carbonate accounts for more than 90% of the total uranium in groundwater. The uranyl content is closely related to the TDS. The TDS of groundwater in the eastern and central ore belts is usually lower than 2 g/L, while in the western region, such as Xinjiang, it can exceed 10 g/L. In situ leaching (ISL) is the main mining method that results in groundwater pollution. Acid leaching leads to a pH decrease (<3), and heavy metals represented by U and Fe exceed the background values by hundreds of times, resulting in groundwater pollution. CO2 leaching is more environmentally friendly, and the excess ions are usually Ca2+, Mg2+, NO3− and HCO3−. Soil chemical anomalies originate mostly from wind erosion and precipitation leaching of decommissioned tailings. Uranium pollution is mainly concentrated within 20 cm of the surface, and the exceedance generally varies from two to 40 times. During ISL, a series of environmental measures will be taken to prevent pollution from being exposed to the surface. After treatment, the decommissioned uranium mines will likely have no impact on the surrounding environment. In the future, the protection of groundwater should be strengthened during production, and remediation methods based on electrokinetic, microbial and permeable reactive barrier (PRB) technology should be further researched. [ABSTRACT FROM AUTHOR]

The Baishuizhai, Shituling and Zhushanxia deposits from the Xiazhuang district represent to date the only known occurrences of early Yanshanian (Middle to Upper Jurassic) granite-related high-temperature hydrothermal uranium deposits (175–145 Ma) in the Nanling Metallogenic Belt, South China. Whole-rock geochemistry of ore samples combined with chemical and mineralogical signatures of the hydrothermal phases associated with the U mineralisation characterised a coeval potassic and propylitic alteration fingerprint: (i) the potassic alteration is defined by Na and Ca depletion of the granitic host rock and precipitation of adularia, dioctahedral Fe-muscovite, biotite and secondary quartz; and (ii) the propylitic alteration is marked by whole-rock enrichment in Ca, Fe, Mg, Mn and Ti mainly associated with the precipitation of (Mn)-epidote, Fe-chlorite, fluorapatite, titanite, calcite, APS and Fe-Cu-Pb-Cd-Bi-Mo-sulfide minerals. The high-temperature conditions of the hydrothermal system was demonstrated by the typologies of alteration such as greisen, chlorite geothermometry giving temperature estimates of the ore fluid ranging from 316 to 455°C, minor W mineralisation and the high Zr contents in titanite. Besides, high Rb, Ba, Be, Y, Nb, W, Ta and Mo contents in ore samples, mineral assemblages and chemical signatures of the hydrothermal phases showed evidence for the alteration of fractionated felsic granitic host rocks and the contribution of enriched magmatic-derived fluids. Therefore, these characteristics define a magmatic-hydrothermal genetic model directly related to the intrusion of early Yanshanian granites in the Nanling belt. In this new metallogenic model, highly fractionated high-K calc-alkaline A2-type granitic plutons have provided magmatic fluids, heat and metal sources to the early Yanshanian high-temperature hydrothermal U system. Uranium (±W-Sn-Nb-Ta-Li)-rich fluids were derived from fractionated peraluminous residual silicate melts. Uranium was enriched in a high-temperature, highly saline, F-rich, acid and reducing fluid, and dominantly carried as fluoride complexes. This mineralising fluid percolated in the Indosinian U-rich host granites within the cupolas of early Yanshanian granites and produced characteristic propylitic and potassic (including greisen) hydrothermal alteration. During the hydrothermal alteration, the pH and T variations of the mineralising fluid and the subsequent precipitation of F- and P-bearing hydrothermal phases induced the destabilisation of U complexes, winch eventually triggered the deposition of the U mineralisation. [ABSTRACT FROM AUTHOR]

The sandstone-hosted uranium deposits in the SW Songliao Basin differ from typical sandstone-hosted uranium deposits in terms of the geological features of the ore-deposits, including the geometry of the orebodies, mineral assemblage and petrography. Detailed drill core and microscopic observations, scanning electron microscopy (SEM), electron microprobe analysis (EMPA), heavy mineral concentrates, and fluid inclusion studies of the Upper Cretaceous Yaojia Formation, i. e., the uranium-bearing layer, were integrated to investigate the roles of hydrothermal fluids in the formation of these uranium deposits. We found that the kaolinite alteration is developed in the mineralized zones, but it is less common in the peripheral areas. The fluid inclusions are hydrothermal fluids with a medium-low temperature (67 to 179 °C) and a high salinity (5.9 wt.% to 20.1 wt.%). According to the analyses, three kinds of hydrothermal fluids, i.e., the acid fluid, the groundwater heated by the mafic magma, and the alkaline fluid rich in Ca2+ and CO32−, were identified. The fluids might have low U content, but they have participated in the formation of the uranium deposits successively. Kaolinite formed by the acid-hydrothermal fluid absorbed large amounts of uranium. Subsequently, the thermal energy from the hydrothermal fluids changed the intrastratal redox environment and increased the solubility of the uranium minerals in the fluid. The alkaline-hydrothermal fluid rich in Ca2+ and CO32− facilitated the formation of stable Ca-U(VI)-CO3 complex, which led to the enrichment of soluble uranium in solution, and final precipitation as pitchblende, brannerite and Ti-bearing uranium minerals in the uranium ores. [ABSTRACT FROM AUTHOR]

As the scale of nuclear power in China continues to expand, the problem of external dependence on uranium resources has become more and more prominent. The guarantee of uranium resources is facing great risks, especially the procurement risks. Therefore, the procurement risks of uranium resources based on the analytic hierarchy process and fuzzy comprehensive assessment method from multiple perspectives is analyzed in this paper. The results show that the risk values of target region selection, supplier selection and uranium mining are 73.6, 71.3 and 71.8 respectively, which are the main risks. The risk values of procurement contract and procurement cost are 69.3 and 67.5, which are relatively low. They can be regarded as the secondary risks. In addition, the countermeasures of uranium resource procurement risk are put forward from six aspects including risk mitigation, risk prevention, risk transfer, risk avoidance, risk retention and risk backup measures. It is helpful to guide the risk management of China's uranium resources in procurement and transportation activities [ABSTRACT FROM AUTHOR]

The continuous temperature rise has raised global concerns about CO2 emissions. As the country with the largest CO2 emissions, China is facing the challenge of achieving large CO2 emission reductions (or even net-zero CO2 emissions) in a short period. With the strong support and encouragement of the Chinese government, technological breakthroughs and practical applications of carbon capture, utilization, and storage (CCUS) are being aggressively pursued, and some outstanding accomplishments have been realized. Based on the numerous information from a wide variety of sources including publications and news reports only available in Chinese, this paper highlights the latest CCUS progress in China after 2019 by providing an overview of known technologies and typical projects, aiming to provide theoretical and practical guidance for achieving net-zero CO2 emissions in the future. [ABSTRACT FROM AUTHOR]

Many sandstone-type uranium mineralization sites have been identified along the northern margin of the Qaidam Basin in North China. Intense tectonism and multistage magmatism that occurred there have restricted the use of conventional techniques (petrogeochemistry) to deduce the sources of detritus and uranium in these sediments, and to further explore the sandstone-type uranium deposits. In this study, U-Pb geochronological and Hf isotopic analyses were conducted on detrital zircon grains collected from Jurassic to Paleogene sandstones exposed in the Yuqia area of the Qaidam Basin. The results indicate that the U-Pb ages of the analyzed zircon grains are clustered into four groups, 285–229, 498–401, 999–806, and 2 520–2 305 Ma. The εHf(t) of the analyzed zircon grains ranges from -21.9 to +10.5, with two-stage Hf model ages (TDM2) concentrated between 2.1 and 1.3 Ga. Based on paleocurrent studies and results of petrological, detrital zircon geochronology, and Hf isotopic analyses, the Jurassic sediments in the Yuqia area were likely derived from the tectonic belt along the northern margin of the Qaidam Basin, such as the Qilian Mountains and the Quanji Block. In contrast, the Paleogene sediments were probably sourced from the northern margin of the Qaidam Basin and the Qilian Mountains. The uranium and thorium content and Th/U value of the rock mass and sedimentary strata in the source area show that the Indosinian Early Paleozoic uranium-rich granites and the Middle Jurassic uranium-rich strata of the northern margin of the Qaidam tectonic belt in the source area provide dual uranium sources for the Yuqia sandstone-type uranium mineralization. Therefore, the study area appears to be favorable for sandstone-type uranium mineralization and may have potential for uranium prospecting. [ABSTRACT FROM AUTHOR]

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Uraninite from intrusive-related deposits has MREE-enriched patterns with significant contents of Th, Y, and ∑REE. • Uraninite REE patterns for deposits of epigenetic origin typically resemble the host rocks. • Uraninite REE signatures can help constrain genetic model of uranium deposits and discriminate deposit types. Uraninite is generally the most principal component of uranium ores and can record the significant information about uranium mineralization processes. Here, chemical compositions of uraninites from thirty-five uranium deposits of nine types (including granite-related, sandstone-hosted, volcanic-related, black shale-hosted, Na-metasomatite-hosted, peralkaline syenite-hosted, pegmatite-hosted, carbonatite-hosted, and leucocratic dyke-hosted) in China were examined, with the aim to investigate the chemical variations of uraninite from each deposit type and fingerprint uranium metallogenesis. Uraninites from the last five types contain significant abundances of ThO 2 (median = 3.81 wt%), Y 2 O 3 (0.96 wt%), and ∑REE (typically ≥ 1 wt%) and low concentrations of Si, Fe, and Ca (SiO 2 + CaO+FeO typically < 1 wt%) and have middle rare earth elements (MREE)-enriched chondrite-normalized REE patterns with pronounced negative Eu anomalies, although the carbonatite-hosted type shows insignificant Eu anomaly. These characterize the affinity of intrusive-related deposits that formed at high temperatures. Uraninites from granite-related deposits generally contain negligible abundances of Th and Y, the highest CaO (up to 9.89 wt%), and highly variable ∑REE concentrations. Their chondrite-normalized REE patterns typically resemble those of the host granites, suggesting that the REE signatures were mainly controlled by the sources of REE (U). Uraniferous phases from sandstone-hosted deposits have the lowest concentrations of UO 2 (median = 66.87 wt%) and the highest SiO 2 (up to 21.63 wt%), FeO (15.72 wt%), Y 2 O 3 (10.35 wt%), and P 2 O 5 (9.69 wt%) and generally show LREE-enriched REE patterns, which are indicative of the predominant role of LREE-rich sources in the mineralization. In contrast, those particles characterized by flat REE patterns probably suggest the involvement of hydrothermal fluids in the mineralization. Although uraninites from black shale-hosted uranium deposits have a LREE-rich source-controlled REE pattern, they are poor in P and Y and rich in W, which can discriminate them from the sandstone-hosted type. Uraninites from volcanic-related uranium deposits have variable REE signatures, suggesting the various formation conditions from which the uraninites form. Our study indicates that uraninite chemistry can help constrain the genesis of uranium deposits and discriminate deposit types. [ABSTRACT FROM AUTHOR]

Groundwater is a key medium for the migration and enrichment of elements into ore bodies in sandstone-type uranium deposits, with anomalies of uranium elements and their associated components in water serving as indicators for exploring such deposits. The Erlian Basin, located in central-northern Inner Mongolia, is a crucial production area for sandstone-type uranium deposits in China. The groundwater flow system in the basin plays a significant role in the formation of uranium deposits. To study the hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian Basin, 269 groundwater samples were collected. Hydrogeochemical analysis methods, such as Piper diagrams, Gibbs diagrams, and contour maps, were employed to determine the distribution characteristics and occurrence forms of groundwater uranium in the study area. The primary water chemistry types in the study area were HCO 3 –Ca•Na, HCO 3 –Na, HCO 3 •SO 4 –Na, and SO 4 •HCO 3 –Na•Ca. The distribution range of uranium content in groundwater in the study area was 0.1–453 μg/L (average of 53.08 μg/L). A comprehensive analysis, based on the direction of groundwater flow and changes in the redox environment, suggested that the higher uranium values in groundwater were distributed in the runoff and discharge areas, with uranium anomaly points existing in areas with alternating oxidation and reduction zones. These uranium anomaly points were in good agreement with the known large uranium deposits of Nuheting, Qiharigetu, Daoersu, and others, thereby predicting six other uranium hydrochemical anomaly points as prospective areas for uranium mineralization. The pH value distribution range in the study area's groundwater was 6.8–9.1, and the redox potential (Eh) value range was -126–52 mV, indicating that uranium exists in groundwater in the form of UO 2 (CO 3) 3 4− and UO 2 (CO 3) 2 2−. An increase in bicarbonate (HCO 3 −) is conducive to uranium dissolution. The enrichment and occurrence forms of uranium in groundwater are influenced by the concentrations of Fe and (Ca2++Mg2+), with uranium precipitation and enrichment occurring as the groundwater evolves and changes in the redox environment. The uranium content in deep wells is higher than in nearby shallow wells, indicating that deep water circulation is beneficial for mineralization. The pH, Eh, HCO 3 −, Fe, and other hydrogeochemical indicators are indicative of uranium enrichment; thus, they can be considered as reference bases when exploring for potential uranium resources. • Hydrogeochemical composition of groundwater varies from recharge to discharge zones. • The majority of U anomalies in groundwater correspond to known large U deposits. • Six U hydrogeochemical anomaly points were delineated as U prospecting areas. • The enrichment and occurrences of U are influenced by Fe, (Ca2+ + Mg2+), pH, and Eh. • Deep water circulation is conductive to the development of U mineralization. [ABSTRACT FROM AUTHOR]

In situ leaching (ISL) is becoming the main mining practice for sandstone-type uranium deposits in China. The key to ISL technology is to aid the leaching solution in contacting the ore bed over a large range, which will induce a series of chemical reactions to extract uranium; thus, it is essential to thoroughly understand the reservoir physical properties of uranium deposits. Taking the Qianjiadian sandstone-type uranium deposits (southern Songliao Basin, China) as an example, the mineral composition and pore structure of samples in different layers were measured using X-ray diffraction (XRD), thin section analysis (TSA), low-temperature N2 adsorption (LTN2A), and mercury intrusion porosimetry (MIP), and their influences on the ISL effect were analyzed. The results show that more than 65% of the minerals in the Qianjiadian uranium deposits are felsic minerals, and the carbonate minerals, clay minerals, and augite are auxiliary minerals. The primary intergranular pores, intergranular-dissolved pores, intragranular-dissolved pores, intercrystalline pores, and microfractures are developed in uranium deposits with various lithologies to different degrees. The macropores (>1000 nm) and mesopores (100-1000 nm) of medium sandstone, argillaceous sandstone, and siltstone are well developed; in contrast, the proportions of micropores (<10 nm) and transition pores (10-100 nm) in coarse sandstone, fine sandstone, and sandy mudstone are quite high. The heterogeneity of pores in uranium deposits of different lithologies is strong and influences the mineral composition and its fabric mode. Coarse sandstone, fine sandstone, and sandy mudstone are favorable for ISL mining in Qianjiadian uranium deposits because their permeability is above the required permeability threshold of ISL. The uranium deposits with permeability below the threshold are recommended to adopt the blasting-enhanced permeability method to improve their permeability for achieving large-scale and high-efficiency ISL mining. This study can provide guidance for the selection of favorable ore beds for ISL mining and reservoir stimulation methods in low-permeability sandstone-type uranium deposits. [ABSTRACT FROM AUTHOR]

Since 1972, China's uranium mining technology has developed from the first generation of technology system to the third generation of technology system, and has gradually played a leading role in the field of uranium mining and metallurgy. This paper reviews the research progress of uranium mining technology such as conventional mining,heap leaching, in-situ blasting leaching and in-situ leaching, and focuses on the mainstream technology of uranium mining-in-situ leaching technology. The ecological restoration technologies of plants, soil, landscape and groundwater microorganisms in uranium mines were reviewed. It is worth noting that microbial leaching and remediation technology will have broad application prospects in uranium mining and remediation technology because of its economic, environmental protection and high efficiency. [ABSTRACT FROM AUTHOR]

The waste rock heap is a kind of potential uranium (U) pollution source in U mining and metallurgy areas. In this study, we discussed the distribution characteristics of U in the soil (sludge) around a waste rock heap of a granite-type U mine in southern China, and the aim was to indicate U releasing behavior from the pollution source from the perspective of the sink. This work proves that U carried by colloidal solution can be transported for a longer distance. Thus, in the follow-up regulation engineering for U waste rock heap to inhibit U from entering the environment, it should be concerned on not only the diffusion of U in the form of debris, but especially the migration of U as colloidal solution. [ABSTRACT FROM AUTHOR]

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BACKGROUND: As an epigenetic deposit dominated by supergene fluid, a sandstone type uranium deposit has many low-temperature minerals. In recent years, the Pengyang uranium deposit, a deep sandstone type uranium deposit, has been discovered in the southwest edge of the Ordos Basin, China. The deposit has the characteristics of large sand body scale, wide uranium mineralization area, large thickness and high grade. Many low-temperature altered minerals have developed, including calcite, gypsum, pyrite, and clay minerals. It is of great significance to study the spatial distribution characteristics of minerals and their relationship with uranium minerals to identify the main sources and properties of ore-forming fluids and their controlling on uranium mineralization. Near-infrared core spectral scanning technology can identify layered silicate minerals such as kaolinite, montmorillonite, sericite, and sulfate minerals such as gypsum and alunite, and carbonate minerals such as calcite and dolomite. OBJECTIVES: To study the distribution characteristics of minerals and their relationship with uranium mineralization. METHODS: Core samples were scanned by VNIR-SWIR spectroscopy core scanning system and analyzed by TSG 8. 0. In addition, the microscopic occurrence characteristics of minerals related to uranium minerals were observed by scanning electron microscopy. RESULTS: Minerals such as kaolinite, montmorillonite, illite, chlorite, carbonate, gypsum, and iron oxide were identified in the Luohe Formation. The mineral assemblage of uranium ore section was “illite+gypsum+carbonate”, and minor kaolinite was present locally. CONCLUSIONS: The uranium-bearing section of the Luohe Formation is mainly a set of alkaline environments in the sedimentary period. However, there is also an injection of reducing acid fluid in the metallogenic period. [ABSTRACT FROM AUTHOR]

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Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)