Search Results (52)

Rare earth elements (REEs) play an important role in emerging renewable energy technology, the production of advanced materials, energy conservation, and high-end manufacturing industries, making them an irreplaceable strategic resource. The diagnostic spectral absorption features of REEs in the visible and near-infrared spectrum can be effectively used for identifying the occurrences of REEs on the Earth’s surface. This study systematically compared three airborne hyperspectral sensors—HyMap, CASI-1500h, and AisaFENIX 1K—for detecting REEs in the Bayan Obo area of Inner Mongolia, China. The CASI-1500h imagery performed most effectively in identifying the locations of REEs among the three sensors evaluated here. Additionally, this study proposed a hyperspectral workflow for REE identification, which enabled the detection of REE-bearing minerals regardless of the host rock types—including carbonatites and associated dikes, fenite-syenites, and metamorphic feldspar-quartz sandstone. Laboratory-based spectroscopy and mineral chemistry analyses indicated that the absorption features of the REE-bearing mineral monazite within the 400–1000 nm range can be ascribed to Nd³⁺. This study demonstrates the potential of airborne hyperspectral technology for efficient and large-scale exploration of REE deposits. Full article

The Bayan Obo Mining District, recognized as the largest rare-earth resource base worldwide, has experienced significant surface instability due to intensive mining and large-scale dumping activities. To address the challenges posed by complex geological conditions and mining-induced disturbances, this study employs dual-ascending Sentinel-1A C-band Synthetic Aperture Radar (SAR) datasets (Path 11 and Path 113) and applies the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technique to retrieve time-series deformation along the line-of-sight (LOS) direction for each track. Through temporal normalization and spatial matching, paired LOS observations from the two tracks were established. Based on the SAR observation geometry and under the assumption that the north–south component is negligible, a LOS projection model was constructed and a geometric decomposition was performed to derive the east–west and vertical two-dimensional deformation fields. The results indicate that the study area is generally stable, while significant subsidence occurs in the northern pit and adjacent waste-dump zones, with local maximum rates approaching 50 mm/year, predominantly controlled by the vertical component. The two-dimensional deformation analysis reveals that vertical displacement dominates surface motion, whereas east–west movement shows smaller amplitudes but clear directional concentration. In particular, the east–west slopes exhibit slightly higher velocities, suggesting a lateral adjustment tendency along this direction, likely related to the overall east–west geometric configuration of the open-pit and waste-dump areas. Time-series observations further reveal that precipitation-related surface deformation occurs with an approximate two-month delay, reflecting the hydrological–mechanical coupling processes of rainfall infiltration, pore-water pressure propagation, and dump-material consolidation. Overall, this study reveals the multi-dimensional deformation characteristics and precipitation-driven stage-wise response of the mining area, demonstrating the effectiveness of the dual-ascending SBAS-InSAR for two-dimensional deformation monitoring in highly disturbed environments, and providing a scientific basis for surface stability assessment and geohazard prevention. Full article

To reveal the evolution of the North China Craton (NCC) and the breakup process of the Columbia supercontinent, this study conducted zircon geochronology and garnet mineralogical analyses on kimberlites from the Bayan Obo area, on the northern margin of the NCC. Zircon U-Pb dating yielded four groups of concordant ages: 2505 ± 46 Ma, 2210 ± 57 Ma, 1928 ± 58 Ma, and 1455 ± 88 Ma. Among these, 1455 ± 88 Ma represents the formation age of the kimberlite, corresponding to a regional extensional tectonic setting. The other three groups are xenocrystic zircon ages, recording the formation of the Archean basement of the NCC, extensional magmatic activity in the middle Paleoproterozoic, and collisional metamorphic events in the late Paleoproterozoic, respectively. The major element characteristics of the garnets indicate they are granulite-facies crust-derived garnets (G4 type), formed under temperature and pressure conditions of 791 ± 50–876 ± 50 °C and 14 ± 3.0 kbar. This corresponds to a mantle heat flow value of approximately 60 ± 5 mW/m², suggesting an unstable state of the lithosphere in the study area. Combined with the regional geological background, the depositional age of the Bilute Formation in Bayan Obo is determined to be between 1455 and 1524 Ma. The emplacement of kimberlite is related to extensional rifting driven by the breakup of the Columbia supercontinent, and garnets hosted in kimberlite record the crustal extension and mantle magma underplating during the rift-spreading stage of this period. This study provides key petrological and chronological evidence for the tectonic evolution of the northern margin of the NCC and the breakup of the Columbia supercontinent. Full article

In order to enhance the separation efficiency of fine-grained Bayan Obo Niobium Ore, a novel gravity separation equipment named Slime Vibrating Table (SVT) was developed. The SVT employs an electromagnetic drive to generate a reciprocating motion for the table, with a lower stroke and higher frequency than a conventional Slime Shaking Table (SST). Key parameters of SVT, including table slope, wash-water flow rate, vibration voltage, and vibration frequency, were tested for a niobium ore assaying 0.19% Nb₂O₅ with a particle size below 74 um by 68.78%. Under the optimized condition, SVT was able to obtain a primary concentrate assaying 1.31% Nb₂O₅ with a recovery of 52.64%, which was 0.22% and 26.59% higher than that of SST, respectively. Size-by-size analysis indicated that the enhanced separation performance of SVT was mainly attributed to its superior recovery of Nb₂O₅ in the −38 μm fraction. The SVT introduced in this study shows great potential for efficient recovery of fine-grained strategic metals, including rare earths, tantalum, tungsten, tin, and antimony, etc. Full article

The spatial variability in rock mass mechanical parameters critically affects slope stability assessments. This study investigated the southern slope of the Bayan Obo open-pit mine. A representative elementary volume (REV) with a side length of 14 m was determined through discrete fracture network (DFN) simulations. Based on the rock quality designation (RQD) data from 40 boreholes, a three-dimensional spatial distribution model of the RQD was constructed using Ordinary Kriging interpolation. The RQD values were converted into geological strength index (GSI) values through an empirical correlation, and the generalized Hoek–Brown criterion was applied to develop a spatially heterogeneous equivalent mechanical parameter field. Numerical simulations were performed using FLAC3D, with the slope stability evaluated using the point safety factor (PSF) method. For comparison, three homogeneous benchmark models based on the 5th, 25th, and 50th percentiles produced profile-scale safety factors of 0.96–1.92 and failed to replicate the observed failure geometry. By contrast, the heterogeneous model yielded safety factors of approximately 1.03–1.08 and accurately reproduced the mapped sliding surface. These findings demonstrate that incorporating spatial heterogeneity significantly improves the accuracy of slope stability assessments, providing a robust theoretical basis for targeted monitoring and reinforcement design. Full article

The Bayan Obo deposit, located on the northern margin of the North China Plate (NCP), is the world’s largest comprehensive Fe-REE-Nb deposit. After its formation, this deposit was affected by multiple tectonic thermal events, but the ages of these geological events are controversial. To determine the evolutionary history of the Bayan Obo deposit, we conducted a detailed study of the macroscopic and microscopic deformation characteristics of the ore district and selected representative minerals, such as riebeckite and biotite, which are widely present in the banded rocks of the deposit, for an ⁴⁰Ar-³⁹Ar isotopic analysis. The results show that a large number of deformation structures have developed in the carbonatite and surrounding rocks, including mineral bands, boudins, tight folds, and rotated porphyroclasts, suggesting that the region has undergone intense compression and shearing and that the deformation temperature can reach ~550 °C. ⁴⁰Ar-³⁹Ar plateau ages of 414.9 ± 1.4 Ma and 264.5 ± 2.5 Ma were obtained for the riebeckite and biotite, respectively. Using these results in conjunction with regional geological data and considering the closure temperature of the mineral isotope system, it was inferred that these two ages corresponded to two distinct reworking events experienced by the deposit during the Early Paleozoic and Late Paleozoic following its initial formation. These events corresponded to the collision between the Bainaomiao Arc and the NCP and the magmatic activity induced by a continental–continental collision during the closure of the Paleo-Asian Ocean (PAO), respectively. Full article

To address the limitations of traditional early warning methods in open-pit slope displacement monitoring—particularly their neglect of spatiotemporal correlations and their difficulty in analyzing multi-scale non-stationary sequences—this study proposes an early warning framework that integrates spatiotemporal clustering with multi-scale decomposition. Taking the southern slope of the Bayan Obo Main Pit as a case study, high-risk deformation zones were identified using DBSCAN-based spatiotemporal clustering applied to slope radar monitoring data. The displacement time series were decomposed using Variational Mode Decomposition (VMD) into trend and periodic components, for which Gated Recurrent Unit (GRU) and Long Short-Term Memory (LSTM) models were respectively developed. The results indicate that (1) DBSCAN effectively detects clusters characterized by high average cumulative displacement and broad spatial distribution, while filtering out isolated outliers. (2) The trend component prediction achieved a coefficient of determination (R²) of 0.99755, while the periodic component prediction yielded a root mean square error (RMSE) of just 0.0978 mm. The reconstructed total displacement achieved an R² of 0.9973, verifying the proposed multi-scale decomposition and hybrid modeling framework’s high accuracy and robustness in slope deformation modeling and early warning. Full article

Bayan Obo rare earth concentrate (BOREC) is composed of bastnaesite, monazite and fluorite, which is recognized as a refractory mineral in the world. In order to solve the problems of waste gas treatment and comprehensive utilization efficiency of BOREC decomposed by the current concentrated sulfuric acid roasting method (500–700 °C), H₂SO₄-HCl mixed acid assisted by aluminum salt was used to leach out the bastnaesite, and the optimal conditions were determined as follows: c(H⁺) = 7 mol/L, c(1/2H₂SO₄):c(HCl) = 5:1, c(Al₂(SO₄)₃) = 0.25 mol/L, temperature 135 °C, liquid–solid ratio of 42:1, and reaction time 3 h. At this time, the leaching rates of concentrate and rare earth (La, Ce, Pr and Nd) were 74.08% and 71.95%, respectively, and the decomposition rate of bastnaesite was 96.83%. At the same time, the yield of calcium sulfate was 77.35% and the purity was 99.22%. Subsequently, sodium sulfate was added with m(Na₂SO₄):m(RE₂O₃) = 2.5:1, and the recovery rate of rare earth was 99.5%, and the purity of rare earth double salt product was 98.47% at a temperature of 90 °C. After most of the acid had been extracted with triethyloctanamine, sodium fluoride was added with a fluorine–aluminum ratio of 6:1, sodium carbonate was used to adjust pH = 3, and cryolite was obtained with a purity of 95.59% and an aluminum recovery rate of 99.6% at 90 °C. Since the separation of bastnaesite and monazite has been basically realized in the leaching stage, it is conducive to the docking of subsequent alkali decomposition and recovery of trisodium phosphate, realizing the comprehensive recovery of rare earth, fluorine, calcium, aluminum and phosphorus. Full article

The Bayan Obo is the largest carbonatite-type rare earth deposit in the world. It not only has a large amount of light rare earth element (LREE) resources but also hosts approximately 9 million tons of medium and heavy rare earth element (M+HREE) resources. However, the M+HREE resources have not received enough attention, which hinders their further utilization. In this study, we conduct a systematic investigation of the distribution and process mineralogy properties of M+HREE in different types of ores in the Bayan Obo deposit. The high-value area (>0.1%) of M+HREE elements is found concentrated in the central and deeper parts of the Main and East orebodies. The content of M+HREE varies among different types of ores, with the Aegirine type (1005 ppm) and Fluorite type (1204 ppm) showing a higher average M+HREE concentration. The minerals rich in M+HREE include bastnäsite, monazite, Ca-fluorocarbonate, Ba-fluorocarbonate, allanite, aeschynite, and fergusonite, each with concentrations exceeding 4000 ppm. Aeschynite and fergusonite, in particular, exhibit high M+HREE concentrations and are enriched in fluorite-type and aegirine-type ores. Analysis of the mixed raw ores from the production line at the concentrating plant reveals an M+HREE concentration of approximately 0.2% and a concentration of the seven target minerals at around 12%. However, the particle size distribution and monomer dissociation degree are limited to below 22.3 µm and 40%, respectively. Based on these integrated analyses, we propose that the fluorite-type and aegirine-type ores within the Main and East open-pits are potential M+HREE targets. Furthermore, the recycling and utilization of M+HREE resources in the Bayan Obo deposit require a well-structured process flow and the selection of advanced processing equipment in the future. Full article

Aiming at the high-value application of rare earth elements lanthanum (La), an Al-50% La alloy was selected and prepared in a vacuum medium-frequency induction furnace. The geometric characteristics of the Al-50% La alloy powders were compared and studied, with the powders prepared by two different methods: mechanical pulverization and gas atomization. The results showed that an Al-49.09% La master alloy was obtained, and the only intermediate phase containing La in the experimental alloy was Al₁₁La₃. From the perspectives of chemical and phase composition, La has a high yield. Additionally, an Al-La alloy with controllable rare earth intermediate phases can be obtained. The Al-La alloy powders prepared by the mechanical pulverization method are irregular in shape, but the particle size is relatively small, ranging from 0.25 to 66.9 μm. Submicron powders were obtained, with 4.38% of the powders having an equivalent particle size of less than 1 μm. Considering the characteristic of the selective laser melting (SLM) process forming micro-melt pools, a small amount of submicron Al-La alloy powders prepared by the mechanical pulverization method can be used as a trace additive for SLM preparation of CP-Ti. The powders prepared by gas atomization have good sphericity, with a particle size range of 1.65 to 76.0 μm. Among them, the powders with a size of 2–10 μm account for 75.52%, and this part of the powders can be used for the powder metallurgy preparation of composite materials. Full article

Nioboixiolite-(□) is a new mineral found in a carbonatite sill from the Bayan Obo mine, Baotou City, Inner Mongolia, China. It occurs as anhedral to subhedral grains (100 to 500 μm in diameter) that are disseminated in carbonatite rock composed of dolomite, calcite, magnetite, apatite, biotite, actionlike, zircon, and columbite-(Fe). Most of these grains are highly serrated, with numerous inclusions of columbite-(Fe). The mineral is gray to deep black in color; is opaque, with a semi-metallic luster; has a black streak; and is brittle, with an uneven conchoidal splintery. The Mohs hardness is 6–6½, and the calculated density is 6.05 g/cm³. The reflection color is gray with a blue tone, and there is no double reflection color. The measured reflectivity of nioboixiolite-(□) is about 10.6%~12.1%, close to that of ixiolite (11%–13%). Nioboixiolite-(□) is non-fluorescent under 254 nm (short-wave) and 366 nm (long-wave) ultraviolet light. The average chemical analysis results (wt.%) of twelve electron microprobe analyses are F 0.01, MnO 0.12, MgO 0.15, BaO 0.62, PbO 0.91, SrO 1.49, CaO 2.76, Al₂O₃ 0.01, TREE₂O₃ 1.58, Fe₂O₃ 3.57, ThO₂ 0.11, SiO₂ 1.69, TiO₂ 3.68, Ta₂O₅ 13.95, Nb₂O₅ 47.04, and UO₃ 21.56, with a total of 99.25. The simplified formula is [Nb⁵⁺, Ta⁵⁺,Ti⁴⁺, Fe³⁺,□,]O₂. X-ray diffraction data show that nioboixiolite-(□) is orthorhombic, belonging to the space group Pbcn (#60). The refined unit cell parameters are a = 4.7071(5) Å, b = 5.7097(7) Å, c = 5.1111(6) Å, V = 138.31(3), and β = 90(1) °Å³ with Z = 4. In the crystal structure of nioboixiolite-(□), all cations occupy a single M1 site. In these minerals, edge-sharing M₁O₆ octahedra form chains along the c direction. In this direction, the chains are connected with each other via common vertices of the octahedra. The strongest measured X-ray powder diffraction lines are [d in Å, (I/I0), (hkl)]: 3.662(20) (110), 2.975(100) (111), 2.501(20) (021), 1.770(20) (122), 1.458(20) (023). A type specimen was deposited in the Geological Museum of China with catalogue number M16118, No. 15, Yangrou Hutong, Xisi, Beijing 100031, People’s Republic of China. Full article

With the development of the steel industry, China’s demand for niobium is increasing. However, domestic niobium resources are not yet stably supplied and are heavily dependent on imports from abroad (nearly 100%). It is urgent to develop domestic niobium resources. The Bayan Obo deposit is the largest rare earth element deposit in the world and contains a huge amount of niobium resources. However, the niobium resource has not been exploited due to the fine-grained size and heterogeneous and scattered occurrences of Nb minerals. To promote the utilization of niobium resources in the Bayan Obo deposit, we focused on the mineralogical and geochemical characterization of six types of ores and mineral processing samples from the Bayan Obo deposit, using optical microscopes, EPMA, TIMA, and LA–ICP–MS. Our results show that: (1) the niobium mineral compositions are complex, with the main Nb minerals including aeschynite group minerals, columbite–(Fe), fluorcalciopyrochlore, Nb–bearing rutile, baotite, fergusonite–(Y), fersmite, and a small amount of samarskite–(Y). Aeschynite group minerals, columbite–(Fe), and fluorcalciopyrochlore are the main niobium-carrying minerals and should be the primary focus of industrial recycling and utilization. Based on mineralogical and geochemical investigation, the size of the aeschynite group minerals is large enough for mineral processing. Aeschynite group minerals are thus a significant potential recovery target for niobium, as well as for medium–heavy REE resources. The Nb–rich aegirine-type ores with aeschynite group mineral megacrysts are suggested to be the most significant niobium resource for mineral processing and prospecting. Combined with geological features, mining, and mineral processing, niobium beneficiation efforts of aeschynite group minerals are crucial for making breakthroughs in the utilization of niobium resources at the Bayan Obo. Full article

The surface properties of bastnaesite and parisite are similar to their associated gangue mineral, fluorite, which makes the flotation separation of these two rare earth minerals from fluorite one of the industry’s most significant challenges. This study systematically investigates the inhibitory effects and mechanisms of sodium silicate (SS) on bastnaesite, parisite, and fluorite in an octyl hydroxamic acid (OHA) collector system through flotation experiments, various modern analytical methods, and DFT simulations. The flotation test results indicate that the inhibition effects of SS on the three minerals are in the order: fluorite > parisite > bastnaesite. Detection and analysis results indicate that SS forms hydrophilic complexes with Ca atoms on the surfaces of fluorite and parisite, enhancing surface hydrophilicity and inhibiting OHA adsorption, but its impact on bastnaesite is relatively minor. DFT simulation results show that OHA forms covalent bonds with metal ions on mineral surfaces, favoring five-membered hydroxamic-(O-O)-Ce/Ca complexes, and reacts more strongly with Ce atoms than Ca atoms. SS primarily forms covalent bonds with metal atoms on mineral surfaces via the SiO(OH)₃⁻ component, and OHA and SS compete for adsorption on the mineral surfaces. OHA has a stronger affinity for bastnaesite, whereas SS shows the highest affinity for fluorite, followed by parisite, and the weakest affinity for bastnaesite. Full article

Industrial pure zirconium plays an essential role as a structural material in the nuclear energy sector. Understanding the deformation mechanisms is crucial for effectively managing the plasticity and texture evolution of industrial pure zirconium. In the present study, the texture and microstructure evolution of industrial pure zirconium during the cold-rolling process have been characterized by XRD, EBSD, and TEM. The influences of various twins on texture evolution have also been simulated by the reaction stress model. The effects of slip and twinning on the deformation behavior and texture evolution have been discussed based on crystallographic and experimental considerations. Cold rolling yields a typical bimodal texture, resulting in the preferential <$2\stackrel{\mathrm{-}}{1}\stackrel{\mathrm{-}}{1}0$>//RD orientation. The activation of the deformation mechanisms during cold rolling follows the sequential trend of slip, twinning, local slip. Experimental characterization and reaction stress simulation illustrate that T1 twins dominate in the early stage, whereas C2 twins develop at the later stage of the cold-rolling process. Twinning, especially the T1 twin, contributes to the formation of the {0001}<$10\stackrel{\mathrm{-}}{1}0$> orientation. Full article

Bayan Obo is a well-known polymetallic deposit containing significant quantities of rare earth elements, niobium, thorium, and iron. However, the epoch in which mineralization occurred and the mineralization process are still debated due to the complex nature of its mineralization and geological evolution. Inadequate geophysical exploration has further contributed to this lack of clarity surrounding critical issues, such as the deep link between the main orebody and the eastern orebody, the form and distribution of the extensive dolomite, and the geologic structures in the area. Therefore, we implemented the time-domain controlled-source electromagnetic method (CSEM) to acquire electrical structures at depths down to 2.5 km between the Main and Eastern mines. According to the inverted resistivity structure, in conjunction with existing geological and drilling data, we classified the main lithologies and faults based on their resistivity characteristics. Overall, the mineralized carbonatite reflects high to moderately high resistivity. The mineralized carbonatite dips overall from north to south, with a maximum extension depth not exceeding 1.5 km, and its range of occurrence is controlled by nearly east–west-striking faults distributed along the bounding line between the roof and floor rocks. The Main and Eastern mines are connected at depth, but the morphology and position of the ore bodies have significantly changed due to multiple phases of tectonic activity. The electrical structure does not reveal any obvious syncline structures, further refuting the traditional view that the Bayan syncline controls ore formation. Full article