Scandio-fluoro-eckermannite (IMA 2024-002), a new Sc-dominant amphibole-supergroup mineral, has been discovered in the Bayan Obo REE-Nb-Fe polymetallic deposit, China. The new mineral was collected from banded Fe-REE ores that have formed due to the fenitization caused by carbonatite intrusion, in the Main and East open pits at Bayan Obo. Associated minerals include monazite, bastnasite, magnetite, biotite, fluorite, bazzite, thortveitite, and magnesio-fluoro-arfvedsonite. The new mineral occurs as euhedral to subhedral crystals and aggregates, appearing both as inner zones of a crystallization sequence from scandio-fluoro-eckermannite to magnesio-fluoro-arfvedsonite as well as homogeneous fine-grained particles, reaching up to 350 mu m in size and similar to 7 wt% in Sc2O3 content. Scandio-fluoro-eckermannite displays a light yellow to light blue color under plane-polarized transmitted light, with perfect cleavage on {110}, non-magnetic, and no fluorescence. The hardness is 5-6 by analogy to eckermannite, and the calculated density is 3.097 g/cm(3). Electron microprobe analyses determined the main components (average value in wt%): Sc2O3 6.39; SiO2 54.30; MgO 13.42; Na2O 8.38; Al2O3 1.29; MnO 1.47; CaO 1.21; K2O 0.47; FeOcalc 6.43; Fe2O3calc 3.80; F 3.01; H2Ocalc+ 0.67; F equivalent to O-1.27; total 99.74. The composition normalized on the basis of 24 anions (O, OH, F, Cl), with the assumption of (OH, F, Cl) = 2 apfu, corresponds to the empirical formula (A)(Na0.52K0.09 square(0.39))(Sigma 1.00) (B)(Na1.81Ca0.19)(Sigma 2.00) (c)(Mg2.87Fe2+ Mn-0.77(3+) 0.18Sc0.80Fe3+ (0.41))(Sigma 5.03) (T)(Si7.78Al0.22)(Sigma 8.00) O-22(W)[F-1.36(OH)(0.64)](Sigma 2.00). It leads to the simplified formula (Na,square)(Na,Ca)(2)[(Mg,Fe2+)(4)(Sc,Fe3+,Mn3+)][(Si,Al)(8)O-22)](F,OH)(2) and the ideal formula NaNa2(Mg4Sc)Si8O22F2. The crystal structure was refined in the monoclinic system, space group C2/m (#12). Its unit-cell parameters are: a = 9.8212(3) angstrom, b = 18.0866(5) angstrom, c = 5.3091(2) angstrom, beta = 103.767(4)degrees, and Z = 2, with the a:b:c ratio of 0.543:1:0.294. The crystal-structure refinement indicates that Na is the dominant cation at the A(m) and M(4) sites, Mg is the dominant cation at the M(1) and M(3) sites, Sc is the dominant trivalent cation at the M(2) site, and F is the dominant cation at the O(3) site. Therefore, this is the Sc-dominant variety of fluoro-eckermannite. This discovery highlights the importance of amphibole in controlling Sc in this type of ore-forming system. Scandio-fluoro-eckermannite might also be used as a potential recorder to investigate the enrichment process of Sc in the Bayan Obo deposit.
The Bayan Obo giant Fe-Nb-REE deposit is recognized as the world's largest rare earth elements (REE) deposit. The Precambrian outcrop in the area includes Archean gneiss and amphibolite, and Mesoproterozoic Bayan Obo group which has been divided into H1-H9 litho-units. The H8 is now widely accepted as ore-hosting carbonatite, the other litho-units (H1-H7 and H9 litho-units) have been referred to as meta-sedimentary and meta-volcanic rocks. Both intrusive and extrusive origins have been proposed for the ore-hosting carbonatite (H8), the petrogenesis of the other units in Bayan Obo group is also controversial. The different genetic understandings to the ore-hosting carbonatites and their wall rocks have led to diverse deposit models. Through integrated geological profile investigation, combined with micrographic observations, SEM/EDS, TIMA analyses, zircon U-Pb and monazite Th-Pb geochronology, this study investigates the influences of deformations and alterations to the lithologies and the petrogenesis of the wall rock of carbonatite. A schematic model for the ore deposit genesis is proposed, showing the two overprinting stages of REE-Nb mineralization, and the alteration zonation. Our findings reveal that the H9 litho-unit, together with H1-H7 litho-units, may constitute a Paleoproterozoic felsic intrusive complex (zircon U-Pb age similar to 1.95 Ga). This complex is intruded by variable scale carbonatite-biotitite and biotite syenite dikes (zircon U-Pb ages similar to 1.3 Ga), resulting in pervasive aegirine-augite, biotite, albite, and graphite alteration. The H9 litho-unit, the direct wall rock of carbonatite, displays intensive biotite, albite and graphite alteration in an alteration halo to the carbonatite. Both the ore-hosting carbonatite and its wall rocks exhibit varying degrees of ductile shearing. The intensely altered H9 litho-unit shows stronger ductile shear deformation than the other litho-units leading to their foliated texture. Postshearing hydrothermal alterations, characterized by arfvedsonite-pyrite mineralization, occur as veins or disseminated along NE-trending faults/fractures and in shear cleavages. Post-shearing hydrothermal veins crosscut both the ore-hosting carbonatite and shear fabrics. In addition to arfvedsonite and pyrite, veins include bastnaesite, monazite, columbite, aeschynite, Sr-Ba-rich carbonates (e.g., Sr-bearing calcite, strontianite, norsethite, barytocalcite), and sulfate minerals (e.g., barite, celestine), indicating REE-Nb-SrBa-SO4 2--rich hydrothermal fluids. Vein monazite Th-Pb ages (similar to 417 Ma) reveal Paleozoic REE-Nb mineralization. Our results indicate that besides the Mesoproterozoic carbonatite-related REE-Fe-Nb mineralization, Early Paleozoic hydrothermal overprinting significantly contributed to the formation of this giant deposit. Key exploration targets, particularly for high-grade REE-Nb ores, occur at intersections between NE-trending faults and H8/H9 litho-units. In addition to fenitization, biotite and graphite alteration may be significant types of carbonatite-related alteration and may serve as critical indicators for carbonatiterelated REE-Nb mineralization. (c) 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). Thi s is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
With the rapid development of artificial intelligence and robotics, enhancing the operational efficiency and autonomy of robots in complex, dynamic environments has become a key research focus. To address core challenges in this domain — particularly the limitations of traditional robot path planning methods, such as slow convergence and local optimum entrapment — this study proposes a novel Tidal Optimization Algorithm (TOA) inspired by the periodic dynamics of ocean tides. The performance of TOA is rigorously evaluated through comprehensive experiments. First, it is benchmarked against six state-of-the-art algorithms on the CEC 2017 test suite. Subsequently, it is applied to grid-based robot path planning tasks and compared with four competitive algorithms. Results demonstrate that TOA achieves superior or highly competitive performance on most benchmark functions, confirming its strong global search capability. In path planning applications, TOA generates shorter and safer trajectories than all competitors. From the perspective of intelligent robotics, this research not only provides an effective optimization tool for path planning but also offers potential algorithmic insights for future applications in areas such as human–robot interaction, adaptive motion control, and Human Action Recognition (HAR)-driven navigation systems.
Heavy-haul railways play a vital role in freight transportation, and the health of the rails directly impacts the safety and efficiency of railway operations. The heavy axle loads and long train compositions of heavy-haul trains make the rail surface susceptible to damage such as rail corrugation, spalling and abrasion, threatening operational safety. To address the issue, this paper proposes a multi-source data fusion method for identifying rail surface defects on heavy-haul railways. First, complete ensemble empirical mode decomposition with adaptive noise is used to decompose vibration signals and extract multi-dimensional vibration features. Next, dynamic time warping is applied to align rail profile data and extract key geometric features. Then, the vibration features and profile features are fused using Relief-F to select the most discriminative features. Finally, a support vector machine is utilized for defect identification. Experiment results show that the proposed method achieves high accuracy in identifying rail surface defects, with an accuracy of 96.4%.
The effects of Ce2O3 and CaF2 on the microstructure of silicate-based mold flux were investigated using an integrated approach combining molecular dynamics (MD) simulations with viscosity testing, SEM-EDS, and XRD analysis. The structural origin of changes in viscosity and crystallization behavior was revealed. It was found that the joint addition of CaF2 and Ce2O3 to the silicate melt leads to a synergistic effect; CaF2 acts as a diluent within the silicate network, while O2− introduced by Ce2O3 promotes the depolymerization of the complex [SiO4]4− network. As a result, highly polymerized structural units (Q2, Q3, and Q4) transform into less polymerized ones (Q0 and Q1), reducing the overall degree of polymerization and enhancing slag fluidity. Moreover, the preferential formation of [SiO4]4−–Ce3+–F− and [SiO4]4−–Ca2+–F− coordination structures replaces the original [SiO4]4−–Ce3+ and [SiO4]4−–Ca2+ linkages. This structural rearrangement facilitates the formation of low-melting-point phases during cooling, thereby suppressing the crystallization tendency and improving the stability of viscous properties of the mold flux. These findings provide theoretical insight for the design of high-performance fluxes used in rare earth-containing steel continuous casting.
