Sandstone-hosted Uranium Deposits Research Articles

In situ microzones U–Pb isotopic dating and its geological significance for sandstone-type uranium deposits in the northern Ordos Basin

Based on the verification of the suitability of the pitchblende certified reference material (GBW04420) for uranium mineral dating, this study conducted in-situ micro-area U-Pb dating on sandstone-hosted uranium deposits in the northern Ordos Basin by integrating femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICP-MS) and secondary ion mass spectrometry (SIMS). The fs-LA-ICP-MS method enables age determination for uranium minerals larger than 20 μm, while SIMS complements the analysis for micro-minerals ranging from 5 to 20 μm. Thus, this combined approach delivers highly precise and comprehensive age results. The overall dating results reveal four distinct mineralization periods: Late Cretaceous, Eocene-Oligocene, Miocene, and Pliocene. The uranium mineralization demonstrates clear multi-phase characteristics, showing strong correlation with later geological events such as basin reworking. This coherence further validates the reliability of the obtained age data.

Constraints from Geochemistry of Mineralization-Hosting Sandstone and Sulfur Isotopes of Pyrite on Uranium Mineralization in the Liuhuanggou Area, Southern Junggar Basin

A combination of microstructural, fluid inclusion, and in situ sulfur isotopic analyses of pyrite, along with major and trace element studies of the mineralization-hosting sandstone, reveals the complexity of its genesis from the Jurassic Toutunhe Formation in the Liuhuanggou sandstone-hosted uranium deposit, Southern Junggar Basin. Based on field geological investigations and the geochemical characteristics, it is concluded that the source of the ore-bearing sandstones originates from felsic igneous rocks in the Northern Tianshan and Central Tianshan regions. Through optical microscopy and scanning electron microscopy (SEM), three generations of pyrite were identified: framboidal pyrite, concentric overgrown pyrite, and sub-idiomorphic to idiomorphic cement pyrite. The sulfur isotopes of the pyrite were analyzed using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The results indicate that each type of pyrite has distinct sulfur isotope compositions (the framboidal pyrite: −16.85‰ to +2.16‰, the concentric overgrown pyrite: −7.86‰ to +10.32‰, the sub-idiomorphic to idiomorphic cement pyrite: +9.16‰ to +16.77‰). The framboidal pyrite and the sub-idiomorphic to idiomorphic cement pyrite were formed through bacterial sulfate reduction (BSR), while the concentric overgrown pyrite was formed through thermochemical sulfate reduction (TSR) triggered by the upward migration of hydrocarbons. The discovery of hydrocarbon inclusions provides evidence for the involvement of deep-seated reducing fluids in uranium mineralization. Uranium mineralization occurred in two distinct stages: (1) The early stage involved the interaction of uranium-bearing fluids with reductants in the mineralization-hosting strata under the influence of groundwater dynamics, leading to initial uranium enrichment. (2) The later stage involved the upward migration of deep-seated hydrocarbons along faults, which enhanced the reducing capacity of the sandstone and resulted in further uranium enrichment and mineralization.

Epigenetic Alteration of the Hailijin Sandstone-Hosted Uranium Deposit and Its Indications on Uranium Metallogenesis in the Songliao Basin, NE China

This study focuses on the Hailijing sandstone-hosted uranium deposit in the Songliao Basin. Through a combination of petrographic analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and geochemical analysis, the epigenetic alteration of the deposit was systematically investigated, and the alteration zonation was delineated. On this basis, the metallogenic mechanisms were further explored. The results indicate that six major types of alteration can be identified in the ore-bearing strata of the Hailijing uranium deposit: hematitization, limonitization, carbonatization, pyritization, clay mineralization (including kaolinite, illite, and illite-smectite mixed-layer), and baritization. The mineral assemblages at different stages of alteration vary: during the sedimentary diagenetic stage, the assemblage consists of “hematite + clay minerals + II-type pyrite (framboidal pyrite) + III-type pyrite (euhedral granular pyrite)”; during the uranium mineralization stage, it transitions to “ankerite + barite + I-type pyrite (colloidal pyrite) + minor kaolinite”; and in the post-ore stage, alteration is characterized by calcite cementation in red sandstones. Based on petrological, mineralogical, and geochemical characteristics, as well as the spatial distribution of the host gray sandstones, it is inferred that during uranium mineralization stage, the ore-bearing strata underwent reduction by uranium-rich reducing fluids sourced from the Lower Cretaceous Jiufotang Formation. The primary red sandstones of the Lower Yaojia Formation, formed under arid to semi-arid conditions, experienced varying degrees of reduction, resulting in a color transition from light red, brownish red, and yellowish brown to grayish-yellow and gray. Accordingly, four alteration zones are distinguished in the Hailijing uranium deposit: the primary red zone, weakly reduced pink zone, moderately reduced grayish-yellow zone, and strongly reduced gray zone. Furthermore, as the uranium-rich reducing fluids migrated from a high-temperature, high-pressure deep system to the low-temperature, low-pressure ore-bearing sandstone strata near the surface, uranium was unloaded, precipitated, and enriched, ultimately forming multi-layered and tabular-shaped uranium orebodies within the gray sandstone. This study elucidates the epigenetic alteration processes and metallogenic mechanisms of the Hailijing uranium deposit, providing a critical theoretical basis for further uranium exploration in the southern Songliao Basin.

Integrated geophysical response characteristics of Nuheting uranium deposits: Implication for a predictive model of syn-sedimentary–diagenetic uranium mineralization

The Erlian basin is one of the most significant uranium-producing basins in China, mainly yielding two types of uranium deposits: roll-front (e.g., sandstone-related) and sedimentary-diagenetic (e.g., mudstone-siltstone-related). While geophysical research has been provided valuable insight into sandstone-hosted uranium deposits (SUD), there is a paucity of findings regarding mudstone-siltstone-related uranium mineralization. Therefore, the geophysical characteristics of mudstone-siltstone-related uranium deposits remain unclear, and a cost-effective prediction pattern on geophysical data has yet to be created. To address these challenges, we employed integrated geophysical exploration methods (e.g., gravitational surveying, ground magnetic prospecting, radon surveying, electromagnetic surveying, and seismic exploration) to study the Nuheting syn-sedimentary-diagenetic uranium deposits (SDUD), which represent the largest mudstone-siltstone-related deposits in this basin. The results revealed essential geophysical response characteristics associated with uranium-favorable sites. These areas tend to exhibit low-medium magnetic and gravity readings; a distinct pattern of soil radon anomalies was noted, following a “high–low–high” trend at these sites; the geophysical properties of the upper member of the target formation indicate low resistivity and unstable seismic facies, whereas the lower layers show high resistivity and scrambled seismic facies. Furthermore, this type of uranium mineralization often occurs in a “U”-shaped stratigraphic formation, typically situated in regions underlying faults. Based on the findings, we established a prediction pattern of the SDUD for the first time. In conclusion, a combination of gravitational, magnetic, radon, electromagnetic, and seismic prospecting techniques prove to be a method for effectively estimating U environments and it is more efficiently than any single approach in exploring the SDUD. Furthermore, the geophysical prediction pattern we propose allows the discovery of similar SDUD in sedimentary basins to be economical and efficient. By optimizing the use of integrated geophysical techniques, this approach enhances uranium exploration while reducing time and costs associated with traditional methods.

Petrological, mineralogical, carbonate C-O and sulfide S isotope study of the Bayinqinggeli sandstone-hosted uranium deposit in the northern Ordos Basin

Petrological, mineralogical, carbonate C-O and sulfide S isotope study of the Bayinqinggeli sandstone-hosted uranium deposit in the northern Ordos Basin

In situ U–Pb dating of dolomite: Reliable ages for sandstone-hosted uranium deposits in the southern Songliao Basin, NE China

In situ U–Pb dating of dolomite: Reliable ages for sandstone-hosted uranium deposits in the southern Songliao Basin, NE China

Framboidal pyrite in Dongsheng sandstone-hosted uranium deposit, northern Ordos Basin: Implications for fluid evolution and uranium mineralization

Framboidal pyrite in Dongsheng sandstone-hosted uranium deposit, northern Ordos Basin: Implications for fluid evolution and uranium mineralization

Comprehensive Study on Hydrogeological Conditions and Suitability Evaluation of In Situ Leaching for Sandstone-Hosted Uranium Deposit in Erlian Basin

As a strategic mineral and energy resource, the enrichment and metallogenic mechanism of sandstone-hosted uranium deposits are highly dependent on hydrogeological conditions. However, the relationship between sandstone uranium mineralization and hydrogeological conditions has not received sufficient attention yet. The pumping test, hydrogeological parameters and hydrochemical characteristics were employed to analyze the change characteristics of hydrogeological conditions and evaluate the suitability of in situ leaching (ISL). The results showed that the study area in the Inner Mongolia Autonomous Region could be divided into two groundwater subsystems, namely Quanzha-Engeriyin and Luhai-Zhendai. The latter with relatively high water richness is confined and a main ore-bearing aquifer, which consists of four orebodies. The well discharge (Q) and hydraulic conductivity (K) of Orebody II ranged from 98.40 to 867.36 m3/d and 0.25 to 5.64 m/d, respectively, indicating the aquifer is suitable for the migration, enrichment and mineralization of uranium due to relatively high permeability and fast flow rate. The water storage of Orebodies III-IV gradually deteriorated from east to west in a stepped pattern. And the highest values of Q and K in Orebodies III-IV decreased from 1200 m3/d to 120 m3/d and 1.75 m/d to 0.035 m/d, respectively, suggesting these were conducive to a reduction in and accumulation of uranium under poor hydrodynamic conditions. Additionally, the study area would be defined as three grades, including favorable, relatively favorable and unfavorable areas of ISL according to a comprehensive evaluation. This study provided a scientific basis for evaluating the possibility of in situ leaching for sandstone-hosted uranium deposit.

The Role of Hydrocarbons in the Formation of Uranium Mineralization, Louzhuangzi District, Southern Junggar Basin (China)

In recent years, there have been important breakthroughs in the exploration for sandstone-hosted uranium (U) deposits in the Louzhuangzi district of the southern Junggar Basin. Between 2020 and 2023, a medium-sized sandstone-hosted uranium deposit production area was identified in the region. Only a few investigations have been conducted at the Louzhuangzi U deposit, including those analyzing its geological–tectonic evolution, basic geological features, hydrogeology, and ore-controlling factors. It is generally believed that uranium mineralization at the Louzhuangzi U deposit is controlled by a redox zone. Organic matter (referred to as OM hereafter) consisting of bitumen and carbonaceous debris is very common in the uranium ores (especially in high-grade ores) at the Louzhuangzi U deposit. However, the characteristics of the OM and its contribution to uranium’s mineralization have not been studied in detail. In this study, OM-rich U-ores, altered sandstone, and barren sandstone samples were collected for petrography, mineralogical, micro-spectroscopy, carbon, and sulfur isotope studies. The results of this study show that the distribution of U minerals and metal sulfides (pyrite, sphalerite, etc.) was strictly controlled by bitumen at the Louzhuangzi U deposit. The bitumen may have been formed by hydrocarbon-rich and U-rich ore-forming fluids, which were formed after hydrocarbon generation and expulsion in the underlying Jurassic coal-bearing source rocks. The fluids contained U, Zn, Fe, and other metal elements, which migrated together and then precipitated into the oxidized Toutunhe Formation sandstone through cracking and differentiation processes. Therefore, the results indicate that migrated hydrocarbons were involved in U mineralization, in addition to oxidation–reduction processes, in the Louzhuangzi district, south of the Junggar Basin (China).

The behavior of pyrite during in-situ leaching of uranium by CO2 + O2: A case study of the Qianjiadian uranium deposit in the Songliao Basin, northeastern China

The behavior of pyrite during in-situ leaching of uranium by CO2 + O2: A case study of the Qianjiadian uranium deposit in the Songliao Basin, northeastern China

Jurassic sedimentary evolution model and its implication for the sandstone-type uranium mineralization in the Kamusite area in eastern Junggar Basin, NW China

Jurassic sedimentary evolution model and its implication for the sandstone-type uranium mineralization in the Kamusite area in eastern Junggar Basin, NW China

Polymorphic transformations of titanium oxides contribute to economic uranium mineralization in sandstone

Abstract Sandstone-hosted uranium (U) deposits provide a significant U resource for nuclear energy worldwide. Driven by redox reactions, tetravalent uranium-bearing minerals are commonly associated with reductants (e.g., pyrite and organic matter). However, numerous observations have revealed that tetravalent uranium-bearing minerals can spatially coexist with chemically stabilized titanium oxides in sandstone-hosted U deposits, requiring a complementary mechanism to interpret these findings. We present a new model based on in situ texture, trace-element content, and titanium isotopic ratio, as well as polymorph type and related transformation for titanium oxides from the Yaojia Formation of the southwestern Songliao Basin in northeast China. Specifically, in our model, abundant nanopores were generated during the spontaneous transformation of anatase to rutile, producing a porous material for hexavalent U adsorption. Facilitated by a U-rich source rock, adsorbed U in porous titanium oxide from the lower Yaojia Formation was up to several thousand parts per million. In order to minimize surface energy, a subsequent decrease in surface area by merging small pores is inevitable. When the evolved surface area was small enough, hexavalent U would be desorbed and subsequently transformed to tetravalent U by local reductants, forming uraninite nanoparticles on the surface of U-rich rutile with relatively large pores. Our newly proposed mechanism not only contributes to a better understanding of economic U mineralization in sandstone, but also suggests that U occurred as uranium oxide instead of brannerite in sandstone-hosted U deposits, providing a nano-mineralogical perspective required for industrial processing.

Using seismic petrophysical modeling and prestack simultaneous inversion to provide insights into the physical properties of uranium-bearing reservoirs: Implications for favorable sites of sandstone-hosted uranium deposits

Seismic prospecting has been accepted as one of the most widely available methods for exploring sandstone-hosted uranium deposits (SUDs). However, conventional seismic interpretation faces a challenge in the identification and characterization of a uranium reservoir’s complexity. How to characterize in detail a uranium reservoir’s physical complexity and effectively improve uranium reservoir prediction accuracy remain unresolved problems. To address this, we develop a novel combination of petrophysical modeling and prestack simultaneous inversion to understand in detail the physical properties of uranium-bearing reservoirs and efficiently predict favorable SUD sites. First, we develop a workflow of rock-physics modeling for SUD logs using the Xu-White method to calculate the modulus of elasticity of the grain matrix; subsequently, we extend the Walton model for the modulus prediction of the dry rocks and the Gassmann equation for one of the saturated rocks after a massive calculation test; and then, we predict the S-wave data used for the following inversion. Second, we execute a prestack simultaneous inversion to obtain the petrophysical parameters (e.g., P-impedance, density [[Formula: see text]], shear modulus [[Formula: see text]], Lamé coefficient [[Formula: see text]], and Young’s modulus) that can provide insights into the physical properties of a uranium metallogenic environment. Accordingly, we discover that sites bearing uranium mineralization strongly correspond to areas with low elastic-parameter values (especially [Formula: see text] and [Formula: see text]), whereas nonuranium anomalies occur in high-value sites. This indicates that weakened elastic characteristics are caused by the enhancement of the total organic content and total clay mineral volumes of the uranium-bearing layers. In summary, the developed combination approach can yield an effective and accurate characterization of the geologic properties of uranium-bearing formations, and it can provide prediction factors (e.g., parameters related to the shear modulus) for uranium mineralization.

Sulfur isotope and trace element constraints on the conditions of pyrite formation from the Diantou-Shuanglong sandstone-hosted uranium deposit, Ordos Basin, China: Implications for uranium mineralization

Sulfur isotope and trace element constraints on the conditions of pyrite formation from the Diantou-Shuanglong sandstone-hosted uranium deposit, Ordos Basin, China: Implications for uranium mineralization

Machine Learning-Based Uranium Prospectivity Mapping and Model Explainability Research

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.

Plurigaussian conditional simulation (PGS) of the Budenovskoe uranium roll-front deposit, central Kazakhstan: 3D model of the host sedimentary sequence

ABSTRACT The current paper presents case study of the Budenovskoe sandstone-hosted uranium deposit, the host sequence of which has been modelled geostatistically, using Plurigaussian conditional simulation (PGS) and Sequential Gaussian conditional simulation (SGS). The PGS method minimises subjectivism of the geological interpretations, by constraining the lithological models to geostatistical and lithostratigraphic characteristics of the host sequence, and accurately reproduces litho-stratigraphy of the sedimentary sequence, realistically conveying its complexity. This was integrated with the rock permeability generated using SGS. Integrating two models has significantly enhanced definition of the fluid infiltration passages in the host sequence. The model was built using stochastic algorithms of PGS and SGS, and therefore can be used for estimation the project risk. In practice, the errors, initially estimated to the blocks used for the conditional simulation, are grouped to the volumes of a practical interest, including the resource and reserve domains, production blocks and the leach cells.

Constraints of in-situ S-isotopic compositions of pyrite on the genesis of the Bayinqinggeli sandstone-hosted uranium deposit, Ordos Basin, Northern China

Constraints of in-situ S-isotopic compositions of pyrite on the genesis of the Bayinqinggeli sandstone-hosted uranium deposit, Ordos Basin, Northern China

Characters and Metallogenetic Significance of Organic Matter in Coal from the Daying Sandstone-Hosted Uranium Deposit in the Northern Ordos Basin, China

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.

Detection and visualization of micron-scale U-Ca phosphates as a key to redox and acid-base conditions in ores: sandstone-hosted uranium deposit

Detection and visualization of micron-scale U-Ca phosphates as a key to redox and acid-base conditions in ores: sandstone-hosted uranium deposit

Geochemical Characteristics of Trace Elements and REEs and their Geological Significance for Uranium Mineralization within the Qianjiadian Sandstone-Hosted Uranium Deposit, Songliao Basin

The Qianjiadian uranium deposit is a typical interstratified oxidized zone sandstone-hosted uranium deposit hosted in the Upper Cretaceous Yaojia Formation of the southern Songliao Basin. Despite its significance, little research has been conducted on the relationship between trace elements, REEs, and uranium mineralization in this deposit. This study presents new geochemical data from sandstones in the oxidation, transition, and reduction zones. The sandstones in the transition zone are highly enriched in U and moderately enriched in Mo, Cd, and V compared to those in the oxidation and reduction zones. They are also weakly enriched in Co, Ni, and Zn. The oxidation and transition zone sandstones have higher ∑LREE and ∑HREE contents than those in the reduction zone. However, the oxidation zone sandstones are characterized by LREE enrichment and flat HRRE distribution, while the transition zone sandstones show HRRE enrichment and flat LREE distribution. These trace element and REE differentiation characteristics within each subzone are closely related to the geological process of interstratified oxygenation. Oxygenated uranium-bearing fluids from southwestern provenance areas carried multiple trace elements and REEs and infiltrated along the oxidation sandstones to reach the Yaojia Formation’s transition zone. During this process, a certain amount of Mo, V, Cd, and LREE from the oxygenated ore-forming fluids was precipitated by Fe-Mn hydroxide adsorption or calcite and siderite cementation. Meanwhile, about 20.33% of preexisting U in the oxidation zone sandstones was continuously extracted and entered into the oxygenated ore-forming fluids. In the transition zone, where dissolved oxygen was exhausted and hydrocarbons were continuously injected, U, Mo, Cd, V, Co, Ni, Zn, and REEs were unloaded and precipitated as uranium minerals, sulfide minerals, or carbonate minerals. The enrichment of Mo, Cd, V, and HREEs in the sandstones can serve as new prospecting indicators for the Qianjiadian uranium deposit.