Rare Earth Research Articles

Rare-Earth Chalcogenides: An Inspiring Playground For Exploring Frustrated Magnetism

Abstract The rare-earth chalcogenide $ARECh_{2}$ family ($A =$ alkali metal or monovalent ions, $RE =$ rare earth, $Ch =$ chalcogen) has emerged as a paradigmatic platform for studying frustrated magnetism on a triangular lattice. The family members exhibit a variety of ground states, from quantum spin liquid to exotic ordered phases, providing fascinating insight into quantum magnetism. Their simple crystal structure and chemical tunability enable systematic exploration of competing interactions in quantum magnets. Recent neutron scattering and thermodynamic studies have revealed rich phase diagrams and unusual excitations, refining theoretical models of frustrated systems. This review provides a succinct introduction to $ARECh_{2}$ research. It summarizes key findings on crystal structures, single-ion physics, magnetic Hamiltonians, ground states, and low-energy excitations. By highlighting current developments and open questions, we aim to catalyze further exploration and deeper physical understanding on this frontier of quantum magnetism.

Application of Y-MOF-CNT-Derived Y2O3-C@CNT Composites in Lithium-Sulfur Battery Separators.

In order to mitigate the shuttle effect of lithium polysulfides in lithium-sulfur batteries, we propose a yttrium-metal-organic framework-carbon nanotube (Y-MOF-CNT)-derived Y2O3-C@CNT composite for modifying the separator in this study. The Y-MOFs, comprising yttrium (Y) rare earth metal and terephthalic acid, exemplify a prototypical category of metal-organic framework (MOF) materials. They manifest the advantageous attributes associated with MOFs while concurrently possessing distinctive catalytic traits ascribed to rare earth elements. In this study, Y-MOF nanoparticles were synthesized on carbon nanotube (CNT) substrates via a facile aqueous solution method, succeeded by high-temperature carbonization to yield Y2O3-C@CNT composite materials. These composites were subsequently employed as coatings on one side of polyethylene (PE) separators. The resultant Y2O3-C@CNT composite inherits the particle-like morphology and porosity from its precursor Y-MOF, alongside the inherent conductivity in carbon-based materials. This amalgamation is conducive to polysulfide capture and catalytic conversion processes within lithium-sulfur batteries. The application of the Y2O3-C@CNT-coated PE separator effectively mitigated polysulfide shuttle effects and significantly enhanced the battery electrochemical performance. At a sulfur loading level of 3 mg cm-2 under a 0.5 C rate, an initial discharge specific capacity of 900 mAh g-1 was achieved. After 400 cycles, the discharge specific capacity remained at 483.85 mAh g-1 with a capacity retention rate of 53.7%. Upon increasing sulfur loading to 5 mg cm-2, the discharge specific capacity at a lower rate (0.1 C) reached 817.8 mAh g-1; even after 100 cycles, it maintained a value of 700 mAh g-1 with a capacity retention rate of 85.6%. Notably, our modified Y2O3-C@CNT separator demonstrated exceptional cycling stability, even under conditions involving high sulfur loading.

High-precision U–Pb geochronology of the Lundy igneous complex: implications for North Atlantic volcanism and the far-field Paleocene–Eocene ash record

The Lundy Island (Bristol Channel, UK) granite is a felsic expression of the southernmost igneous centre of the North Atlantic Igneous Province that emplaced millions of cubic kilometres of magma during the Paleogene. The granite's distinctive S-type, peraluminous, two-mica ± garnet ± tourmaline composition has led to the hypothesis that eruptions from the Lundy volcanic centre may be the source of thick felsic ash layers within the early Eocene Fur Formation (Denmark) that act as key marker horizons for the onset and duration of the Paleocene–Eocene Thermal Maximum. This paper presents high-precision zircon U–Pb emplacement ages of 57.24 ± 0.11/0.12/0.13 Ma for the granite and 55.970 ± 0.021/0.030/0.070 Ma for a felsic ‘lundyite’ dyke. Trace and rare earth element patterns indicate close similarities between late-stage Lundy activity and ash layer −33 in Denmark. This ash layer was deposited during the Paleocene–Eocene Thermal Maximum carbon isotope excursion, suggesting that the Lundy volcanic centre is likely to be the source of this key ash horizon and that magmatism at Lundy likely continued into the early Eocene.

Investigation of in-field heterogeneities in the development of soybean according to remote sensing data and properties of the plow horizon (on the example of the south of the Far East)

Assessment of crop heterogeneities is one of the key conditions for predicting crop yield and increasing the economic efficiency of farming. The aim of the study is to develop methods for assessing in-field heterogeneities of soybean based on remote sensing data and to determine the relationship between soybean productivity indicators and soil characteristics. The work was carried out on meadow-brown heavy loamy soil, 10 plots of soybean field with a total area of 36.9 ha (Khabarovsk Krai) were selected for sampling in May and August 2023. The research was based on the results of remote sensing data processing (Sentinel-2 satellite, DJI Mavic3M quadrocopter), assessment of soybean productivity indicators, agrochemical, physical and chemical characteristics of soils and micro- and macroelement composition. The spatial distribution of NDVI modeled from Sentinel-2 data (early August) corresponded to the distribution of NDVI from DJI Mavic3M data. NDVI index values in August 2023 were found to be significantly correlated with soybean height (R = 0.64) and number of beans (R = 0.64). Soil moisture has a positive correlation with NDVI (R = 0.87) and soybean height (R = 0.68) for the entire growing season of the crop. NDVI was positively correlated with Hg (R = 0.79) and negatively correlated with pH (R = –0.79). The content of N-NO3 ranged from 2.51 to 6.84 mg/kg (V = 35.12 %), mobile forms of Р2О5 – from 2.47 to 6.07 mg/100 g (V = 33.13 %), К2О – from 4.98 to 9.37 mg/100 g (V = 20.07 %). The variability of N-NO3 and Р2О5 content decreased to 11.61 % and 21.99 % by August. No significant changes in soil bulk composition were observed between the first and second sampling. Variation of content of rare-earth elements (Sc, Y, lanthanides) in the selected sites did not exceed 5 %. By the date of the second sampling a significant decrease by 4–10.5 % (p 0.05) in the content of rare earth elements in soil was noted.

Study of structure and properties of dual-size grain copper matrix composites prepared by NbC and rare earth element La

Study of structure and properties of dual-size grain copper matrix composites prepared by NbC and rare earth element La

Rare Earth Elements in Fe oxyhydroxides from biofilms containing iron-oxidizing bacteria

Fe oxyhydroxides extracted from modern-day biofilms with iron-oxidizing bacteria Arthrobacter spp., Gallionella spp и Leptothrix ochracea in the north-west of the East European platform display the enhanced content of rare earth elements – up to 1100 ppm. REE concentration in bacterial oxyhydroxides increase by one order in magnitude during 1 year suggesting the high sorption capacity of newly formed Fe mineral phases. La/YbN, Ce and Y anomalies in bacterial oxyhydroxides are consistent with geochemistry of the surface water facies where bacterial communities live. Isotopic composition of Nd in studied bacterial oxyhydroxides is controlled by the lithology of the Q-R underlying sediment and ambient water. 143Nd/144Nd values in Fe minerals of bacterial origin vary from 0.511570 to 0.512220 (eNd(0) from –21.8 to –9.2), the high proportion of radiogenic Nd is typical for the samples located on platform cover with Palaeozoic carbonate sediment.

Determination of rare earth elements in synthetic calcium phosphates by high-resolution continuum source electrothermal atomic absorption spectrometry

Ceramic, cement and composite biomaterials have been developed based on hydroxyapatites (HA) and tricalcium phosphates (TCP), which are analogous in phase and chemical composition to the mineral component of bone tissue. The crystal structures of HA and TCP are arranged in isomorphic substitutions. Recently, research has focused on the modification of HA and TCP structures with ions of various metals, including rare earth ions (REEs), with the aim of creating materials with a range of beneficial properties for medical applications. REEs are known to have a number of useful properties, including antibacterial, antitumour, catalytic, magnetic and luminescent properties. The replacement of some of the Ca ions in the structures of HA and TCP with REE ions therefore makes it possible to obtain a material with biocompatibility and biological activity, giving it the required properties depending on the REE used and its concentration. In order to achieve the specified properties, it is necessary to control not only the structure (phase composition, lattice parameters of the powders) and the presence of characteristic functional groups, but also the chemical elemental composition. Modifications of hydroxyapatites and tricalcium phosphates containing from one to several different alloying elements are currently being developed. Various analytical methods are used for this purpose, including X-ray, atomic emission and a number of others. This article is devoted to the study of the analytical capabilities of the method of atomic absorption spectrometry with electrothermal atomization and a continuous spectrum source in relation to the determination of Eu and Yb in hydroxyapatites and tricalcium phosphates. The article considers the optimal conditions and modes of analysis, including temperature-time programs, the use of modifiers, the construction of calibration curves, and other factors that can be adjusted for more precise results. The results demonstrated the possibility of simultaneous determination of both Eu and Yb in the concentration range of 0.09 to 2 wt.%, with a relative standard deviation of less than 6 rel.%.

Boosting Coercivity of 3D Printed Hard Magnets through Nano-Modification of the Powder Feedstock.

The demand for strong, compact permanent magnets essential for the energy transition drives innovation in magnet manufacturing. Additive manufacturing, particularly Powder Bed Fusion of metals using a laser beam (PBF-LB/M), offers potential for near-net-shaped Nd-Fe-B permanent magnets but often falls short compared to conventional methods. A less explored strategy to enhance these magnets is feedstock modification with nanoparticles. It is demonstrated that modifying a Nd-Fe-B-based feedstock with 1wt.%Ag nanoparticles boost the coercivity of the magnets to a record value of 935±6kAm-1 without further post-processing or heat treatments. Suitable volumetric energy densities for the PBF-LB/M process are determined using finite element simulations predicting melt pool behavior and part density. Microstructural analyses reveal finer grain sizes and more equiaxed nanocrystalline structures due to the modification. Atom probe tomography identifies three phases in the Ag-modified samples, with Ag forming nanophase regions with rare-earth elements near the amorphous Zr-Ti-B-rich intergranular phase, potentially decoupling the Nd2Fe14B primary phase. The study shows that superior magnetic properties primarily result from microstructure modification rather than part density. These findings highlight inventive material design approaches via feedstock surface modification to achieve superior magnetic performance in additively manufactured Nd-Fe-B magnets.

Characterization of Heavy Minerals and Their Possible Sources in Quaternary Alluvial and Beach Sediments by an Integration of Microanalytical Data and Spectroscopy (FTIR, Raman and UV-Vis)

Quaternary stream sediments and beach black sand in north-western Saudi Arabia (namely Wadi Thalbah, Wadi Haramil and Wadi Al Miyah) are characterized by the enrichment of heavy minerals. Concentrates of the heavy minerals in two size fractions (63–125 μm and 125–250 μm) are considered as potential sources of “strategic” accessory minerals. A combination of mineralogical, geochemical and spectroscopic data of opaque and non-opaque minerals is utilized as clues for provenance. ThO2 (up to 17.46 wt%) is correlated with UO2 (up to 7.18 wt%), indicating a possible uranothorite solid solution in zircon. Hafnoan zircon (3.6–5.75 wt% HfO2) is a provenance indicator that indicates a granitic source, mostly highly fractionated granite. In addition, monazite characterizes the same felsic provenance with rare-earth element oxides (La, Ce, Nd and Sm amounting) up to 67.88 wt%. These contents of radionuclides and rare-earth elements assigned the investigated zircon and monazite as “strategic” minerals. In the bulk black sand, V2O5 (up to 0.36 wt%) and ZrO2 (0.57 wt%) are correlated with percentages of magnetite and zircon. Skeletal or star-shaped Ti-magnetite is derived from the basaltic flows. Mn-bearing ilmenite, with up to 5.5 wt% MnO, is derived from the metasediments. The Fourier-transform infrared transmittance (FTIR) spectra indicate lattice vibrational modes of non-opaque silicate heavy minerals, e.g., amphiboles. In addition, the FTIR spectra show O-H vibrational stretching that is related to magnetite and Fe-oxyhydroxides, particularly in the magnetic fraction. Raman data indicate a Verwey transition in the spectrum of magnetite, which is partially replaced by possible ferrite/wüstite during the measurements. The Raman shifts at 223 cm−1 and 460 cm−1 indicate O-Ti-O symmetric stretching vibration and asymmetric stretching vibration of Fe-O bonding in the FeO6 octahedra, respectively. The ultraviolet-visible-near infrared (UV-Vis-NIR) spectra confirm the dominance of ferric iron (Fe3+) as well as some Si4+ transitions of magnetite (226 and 280 nm) in the opaque-rich fractions. Non-opaque heavy silicates such as hornblende and ferrohornblende are responsible for the 192 nm intensity band.

Incorporating Er:YAP Microcrystals Into Tellurite Fiber Using Volumetric Interface Doping

AbstractIn this semi‐quantitative study, laser crystal microparticles which are potentially capable of generating mid‐infrared (MIR) light are incorporated into MIR transmitting optical fibers using a volumetric interface doping technique that combines interface doping with volumetric doping. Using confocal microscopy with a refractive index matching fluid, the Er:YAP microcrystals (MCs) inside the tellurite glass fiber are observed based on the detection of the green upconversion fluorescence emission of Er3+ ions, produced under excitation at 976 nm and localized at the central region within the fiber. The key outcome from this proof‐of‐concept study is that MC particles that are fused with the glass during the fiber drawing process survived heat treatment because the MC particles are exposed for a short time to a glass fluid with high viscosity of ≈105 Pa.s, which prevented the glass from exerting a dissolution effect. The survival of the MCs demonstrated the viability of the doping technique for fabricating fibers with exotic crystal‐glass combinations for applications including good refractive index matching across the pump and lasing bands of rare earth ions. This latter parameter provides significant particle size flexibility whilst minimizing additional loss from scattering especially at MIR wavelengths where the MC diameter‐to‐wavelength ratio becomes smaller.

Effect of Urea and Thiourea on the color emission of (YxBi1-x)2Zr2O7:Er3+,Yb3+ upconversion phosphors

This study reports the upconversion emission properties of Bi2Zr2O7:Er,Yb (BiZr), Y2Zr2O7:Er,Yb (YZr) and (Y0.25Bi0.75)2Zr2O7:Er,Yb (Y0.25Bi0.75Zr) phosphors. All those samples were synthesized with fixed Er and Yb concentrations of 2 and 20 mol%, respectively. The analysis by X-ray diffraction revealed that the YZr sample had cubic phase, the BiZr sample had a mixture of monoclinic/cubic phases and the Y0.25Bi0.75Zr sample had a mixture of all the phases mentioned above. In addition, the analysis by electron microscopy indicated that all the samples are formed by mixtures of particles with irregular and quasi-spherical shapes. The YZr, BiZr and Y0.25Bi0.75Zr samples were synthesized using urea or thiourea as fuel and an annealing temperature of 775 or 850 °C. For any fuel, the samples produced green (525 and 548 nm) and red (655 nm) emissions by upconversion after exciting them with 975 nm. Interestingly, the Y0.25Bi0.75Zr sample always presented the most intense emission for any fuel or temperature of synthesis. Interestingly, the Y0.25Bi0.75Zr sample made with thiourea had a green emission intensity 49 % higher than that made with urea, but the red emission intensity was 25 % lower in the sample made with thiourea. Color emission tuning was observed in the samples under certain conditions: 1) the color emission for the BiZr sample (made with urea) was changed from yellow to orange-red after increasing the annealing temperature from 775 or 850 °C and 2) the YZr sample (annealed at 775 °C) changed its color emission from green to red after using thiourea instead of urea. Surprisingly, the Y0.25Bi0.75Zr sample always maintained its green emission despite the change of fuel or annealing temperature. In general, the results of this research demonstrate that different fuels or synthesis temperatures can be used to enhance the upconversion emission or to tune the emission color. This avoids the use of high concentrations of rare earths to produce any of these effects as previously reported in the literature.

Cerium-infused tungstate nanocrystals: Illuminating the future of solid-state lighting

Rare earth based luminescent materials have emerged as a focal point of the scientific investigation owing to their remarkable optical behaviour and potential applications. An effort has been made to develop a series of Ce3+ doped CaWO4 nano-phosphors using an ethylene-glycol assisted reflux route. The detailed structural and morphological properties have been examined through various analytical techniques. The +3-oxidation state of the activator ion Ce has been verified through the XPS study. The change in optical band gap due to the substitution is well discussed using diffuse reflectance spectroscopy. In Photoluminescence study, a broad emission centred at 465 nm is observed due to the 5D3/2→2FJ transitions (J = 7/2 and 5/2) and a significant enhancement in the emission peak is obtained for the optimized phosphor. Concentration quenching phenomenon, observed after 3 mol% of Ce3+ is mainly mediated by the electric multipole-multipole type interaction. The CIE diagram indicates the tuning of emission colour from blue to white region and the emission near white region for the optimized phosphor is further authenticated by its low colour purity value (43 %). The effective tunability of photo-physical properties and colorimetric parameters suggest the applicability of the optimized nano-phosphor in solid state lighting especially for outdoor illumination.

Flexible Composites with Rare-Earth Element Doped Polycrystalline Particles for Piezoelectric Nanogenerators

Energy harvesting plays an important role in advancing personalized wearables by enabling continuous monitoring, enhancing wearable functionality and facilitating sustainable solutions. We aimed to develop a flexible piezoelectric energy harvesting system based on inorganic piezoelectric materials that convert mechanical energy into electricity to power a wide range of mobile and portable electronic devices. There is significant interest in flexible piezoelectric energy harvesting systems that use inorganic piezoelectric materials due to their exceptional physical features and prospective applications. Herein, we successfully demonstrated a flexible piezoelectric nanogenerator (PENG) designed by the co-doped rare-earth element ceramics (RE-PMN-PT) embedded in PVDF and PDMS composite film and attained a significant output performance while avoiding electrical poling process. The impact of dielectric characteristics on the electrical output of nanogenerators was investigated, together with the structure of the composites. The Sm/La-PMN-PT particles effectively amplify both the voltage and current output, showcasing their potential to power portable and wearable devices, as demonstrated by their capacity to illuminate LEDs. The maximal output power of 2 mW was correlated with the high voltage (220 V) and current (90 µA) of Sm/La-PMN-PT/PVDF, which demonstrated that the device has the potential for energy harvesting in biomedical applications.

Effect of Microgravity on Rare Earth Elements Recovery by Burkholderia cepacia and Aspergillus niger

Rare earth elements (REEs) are indispensable in modern industry and technology, driving an urgent demand for innovative, eco-friendly recovery technologies. As space exploration advances, the impact of microgravity on microorganisms has become a focal point, yet the effects on microbial growth and REEss recovery remain uncharted. This study investigates the biosorption of REEs by Burkholderia cepacia (B. cepacia) and Aspergillus niger (A. niger) from a mixed solution containing La, Ce, Pr, Nd, Sm, Er, and Y under varying initial concentrations, pH levels, and microgravity conditions. We observed that the medium’s pH rose with B. cepacia and fell with A. niger when cultured in normal gravity conditions, suggesting distinct metabolic responses. Notably, microgravity significantly altered microbial morphology and metabolite profiles, significantly enhancing REEs recovery efficiency. Specifically, the recovery of B. cepacia of Ce and Pr peaked at 100%, and A. niger achieved full recovery of all tested REEs at pH 1.5 (suboptimal growth conditions). This study pioneers the application of biosorption for the recovery of REEs in microgravity conditions, presenting a promising strategy for future resource exploitation by space biomining.

Rare earth element assessment in Jezero crater using the Planetary Instrument for X-ray Lithochemistry on the Mars 2020 rover Perseverance: A case study of cerium

The “Planetary Instrument for X-ray Lithochemistry” (PIXL) X-ray spectrometer conducts in situ geochemical analyses of martian rocks and regolith interrogated by the Mars 2020 rover, Perseverance. In addition to quantifying primary rock-forming elements, PIXL can quantify trace elements that in turn can provide additional constraints on the geologic history of Mars. Accurate quantifications of trace elements can require additional analytical techniques to mitigate experimental, background, and crystalline effects within PIXL spectra. In this study, we focus on reducing the impact of these effects and investigate the potential presence of rare earth elements (REEs). The study specifically investigates cerium given its typical relative abundance in many geologic materials compared to other REEs and its potential to mimic fluorescence features produced by organics under deep UV excitation. A detailed analysis of PIXL targets analyzed through the first 887 martian days of the Perseverance mission did not produce any conclusive Ce detections. Phosphorus-enriched materials analyzed by PIXL are estimated to contain sub-675 ppm Ce and sulfate-enriched materials sub-450 ppm Ce. The method presented can help constrain limits on the abundance of additional trace elements of interest that also face a similar analytical burden. PIXL's potential to assess REE abundances, outside of yttrium, is limited for expected concentrations in surface materials. Determining most REE concentrations in materials interrogated by Perseverance will therefore likely require terrestrial analyses.

Colloidal down-shifting Gd2O3:Eu3+/SiO2 phosphors nanocomposites using one-pot modified surfactants-based soft templates for catalytic applications

The application of rare earth (RE)-based phosphor materials faces a significant challenge in adopting strategies to bring down the cost without compromising their properties. The most straightforward approach is to minimize the use of RE elements. Herein, we demonstrate the use of SiO2 as an economical solid nano-matrix for lanthanides-based phosphor nanomaterials. Gd2O3:Eu3+(x%) and Gd2O3:Eu3+(x%)/SiO2 nanophosphor composites were prepared through a modified soft templating technique using cetyltrimethylammonium bromide (CTAB) as the surfactant. The photoluminescence properties were studied by excitation, emission, and luminescence decay investigations. Upon excitation in the O2−(2p)→Eu3+(4f6) LMCT state, these nanophosphors exhibited predominantly red emission from the 5D0→7FJ transition (where J = 0–4) of the Eu3+ ion. Moreover, the synthesized low-cost Gd2O3Eu3+(5 %)/SiO2 composites, with a small number of lanthanides, exhibited excellent photocatalytic degradation activity for organic dye (methylene blue) under visible light (λ ≥ 420 nm), showing promising potential for photocatalytic wastewater treatment.

Rubidium (Rb) enrichment processes in a highly evolved granitic system: Insights from the petrology and geochemistry of the Guobaoshan Rb deposit in eastern Tianshan, NW China

Highly fractionated granitoids are closely associated with Rb mineralization, yet the mechanisms that control Rb enrichment and details about the enrichment process have not been well constrained. The Guobaoshan Rb deposit in eastern Tianshan, NW China, is one of the largest granite-related Rb deposits; it preserves a series of gradual lithofacies ranging from biotite granite and muscovite granite to Rb-rich amazonite granite and pegmatite, and provides an excellent opportunity to constrain the Rb enrichment processes in granitic systems. The large Guobaoshan Rb deposit hosts 281,000 tons of Rb2O at a grade of 0.12% mainly in its amazonite-bearing granite and amazonite granite lithofacies. In this contribution, we integrate geochronology, bulk-rock geochemistry, and analysis of Nd and zircon Hf isotopes to characterize the evolution of the Guobaoshan granitic pluton and the mechanisms that generated Rb enrichment. The zircon U-Pb age of the biotite granite and columbite U-Pb age of the amazonite granite are 244.8 ± 1.8 Ma (1σ, mean square of weighted deviates [MSWD] = 1.1) and 241.9 ± 2.3 Ma (1σ, MSWD = 1.0), respectively. In situ Rb-Sr analysis of orthoclase, mica, and albite from the amazonite-bearing granite, amazonite granite, and pegmatite yields ages of 249.1 ± 7.3 Ma (2σ, MSWD = 1.6), 245.5 ± 16.8 Ma (2σ, MSWD = 0.63), and 245.8 ± 9.8 Ma (2σ, MSWD = 3.3), respectively. Together, these ages demonstrate that the Guobaoshan granitic pluton formed during the Triassic and underwent a protracted magmatic evolution. The Guobaoshan granitic pluton is characterized by high concentrations of SiO2, alkalis, and Al2O3, and low concentrations of MgO, Fe2O3, CaO, P2O5, and TiO2, with an Al saturation index (A/CNK) of 1.01−1.14. It is enriched in Rb, but depleted in Ba, Sr, P, and Eu, has low total rare earth element (REE) contents (83.1−221 ppm), and is characterized by significantly negative anomalies (Eu/Eu* = 0.01−0.44). The biotite granite is enriched in light rare earth elements (LREEs), whereas the muscovite granite, amazonite-bearing granite, amazonite granite, and pegmatite are depleted in LREEs, and exhibit a marked tetrad effect (TE1.3 = 1.05−1.50). These geochemical characteristics, combined with the non-CHARAC (charge-radius−controlled) ratios of Zr/Hf, Nb/Ta, Y/Ho, and K/Rb, are indicative of melt-fluid interaction during the evolution of the Guobaoshan magma. Given that the biotite granite is the least-evolved rock, its petrological and geochemical characteristics suggest that it is an I-type granite. The slightly variable εHf(t) and consistently negative εNd(t) values indicate that the magma from which the Guobaoshan granitic pluton crystallized was likely sourced from the Mesoproterozoic crust, with limited mantle contributions. The coeval ages and coherent geochemical variations and mineral compositions of these rocks suggest that they formed via fractional crystallization of plagioclase, mica, quartz, and K-feldspar in the same magmatic system. This is supported by fractional crystallization simulations using the rhyolite-MELTS software package. Based on the petrological, mineralogical, and geochemical characteristics of the muscovite granite, amazonite-bearing granite, amazonite granite, and pegmatite, as well as simulations using rhyolite-MELTS, high degrees of fractional crystallization of granitic magma and interaction of this evolving magma with F-rich fluids are suggested to have been the key mechanisms that caused enrichment of Rb, while the melt-fluid interaction was more critical for Rb mineralization.

Minerals’ criticality and countries' mining competitiveness: Two faces of the same coin

This article introduces a novel theoretical and empirical framework for estimating the criticality of key minerals that are intensively used in the energy transition and the mining competitiveness of countries producing them, using economic complexity techniques.The theoretical framework proposes that the most competitive countries are those exporting a broad range of mineral goods, including the most critical ones. Meanwhile, the most critical minerals are the least ubiquitous and are exported by the most competitive countries. The empirical framework relies on an endogenous system of equations in which countries’ mining competitiveness and mineral criticality are simultaneously co-determined. The equation system is solved using the Fitness-Criticality algorithm (FCa), an adaptation of the Economic Fitness-Complexity algorithm.The results show that South Africa, Russia, the United States, and China are the most competitive mining countries. Meanwhile, the platinum group metals, silicon, rare earths, and lithium are the most critical minerals. These results are consistent with other methodologies employed by different experts that separately estimate both dimensions and derive rankings of countries and minerals, but are obtained with a methodology that offers substantial advantages.

Rare-earth elements in dictyonema shales of the Baltic sedimentary paleobasin

The results of a study of rare-earth metals in dictyonema shales of the Paleozoic Baltic sedimentary basin, have been given. On the territory of the studied Kaibolovo-Gostilitsy prospecting area, high up to potentially industrial contents of rare-earth elements were confirmed on a large factual and analytical material. The average REE concentration is 289 g/t with maximum up to 724 g/t. REE are found in dictyonema shales in various forms (mineral, organic, ionic, molecular, colloidal). Apparently, the occurrence of REE in the mineral part of dictyonema shales prevails. The proportion of heavy (and most valuable) lanthanides (15.6% in the relative total amount) in the studied dictyonema shales is twice the ore deposits range. This, and the presence of large geological resources of the REE in the dictyonema shales of the Baltic region of Russia, determine the need for their integrated development with other associated components.

Gold Mineralization at the Syenite-Hosted Anwangshan Gold Deposit, Western Qinling Orogen, Central China

The Anwangshan gold deposit is located in the northwestern part of the Fengtai Basin, Western Qinling Orogen (WQO). The gold ore is hosted within quartz syenite and its contact zone. The U–Pb weighted mean age of the quartz syenite is 231 ± 1.8 Ma. It is characterized by high potassium (K2O = 10.13%, K2O/Na2O > 1) and high magnesium (Mg# = 55.31 to 72.78) content, enriched in large ion lithophile elements (Th, U, and Ba) and light rare earth elements (LREE), with a typical “TNT” (Ti, Nb, and Ta) deficiency. The geochemical features and Hf isotope compositions (εHf(t) = −6.68 to +2.25) suggest that the quartz syenite would form from partial melting of an enriched lithospheric mantle under an extensional setting. Three generations of gold mineralization have been identified, including the quartz–sericite–pyrite (Py1) stage I, the quartz–pyrite (Py2)–polymetallic sulfide–early calcite stage II, and the epidote–late calcite stage III. In situ sulfur isotope analysis of pyrite shows that Py1 (δ34S = −1.1 to +3.8‰) possesses mantle sulfur characteristics. However, Py2 has totally different δ34S (+5.1 to +6.7‰), which lies between the typical orogenic gold deposits in the WQO (δ34S = +8 to +12‰) and mantle sulfur. This suggests a mixed source of metamorphosed sediments and magmatic sulfur during stage II gold mineralization. The fluid inclusions in auriferous quartz have three different types, including the liquid-rich phase type, pure (gas or liquid)-phase type, and daughter-minerals-bearing phase type. Multiple-stage fluid inclusions indicate that the ore fluids are medium-temperature (concentrated at 220 to 270 °C), medium-salinity (7.85 to 13.80% NaCleq) CO2–H2O–NaCl systems. The salinity is quite different from typical orogenic gold deposits in WQO and worldwide, and this is more likely to be a mixture of magmatic and metamorphic fluids as well. In summary, the quartz syenite should have not only a spatio-temporal but also a genetical relationship with the Anwangshan gold deposit. It could provide most of the gold and ore fluids at the first stage, with metamorphic fluids and/or gold joining in during the later stages.