Search Results (3,315)

Fresh flotation tailings represent an underutilized archive of mineralogical and geochemical information in which multiple strands of evidence for ore-forming processes and post-depositional modification can be preserved. Detailed characterization of tailings is also vital for assessment of their future potential as a secondary source of recoverable by-products. This study investigates residual mineral speciation and mineral distributions in size fractions of tailings from the Prominent Hill iron oxide–copper–gold (IOCG) deposit, South Australia, with emphasis on rare earth element (REE) minerals and associated phases containing uranium (U). Assemblages of REE minerals can be highly complex at the micron scale and include sequences of mineral replacement, notably monazite → florencite, and monazite → synchysite. Bastnäsite-(Ce) commonly appears paragenetically early and is frequently altered or replaced by synchysite and parisite, supporting episodes of REE remobilization and reconcentration over geological time. Uranium is closely associated with REEs, and U-mineral assemblages are similarly characterized by intricate replacement relationships between uraninite and secondary phases. Uraninite is variably replaced by coffinite and the U-carbonate wyartite, reflecting changes in redox state, silica activity, and fluid composition. Additional replacement pathways from uraninite to Cu–Fe sulphides, including bornite and chalcopyrite, are documented and indicate coupled dissolution–reprecipitation of sulphides and U-minerals during superimposed hydrothermal activity. Preservation of mineralogical relationships within tailings drawn from multiple parts of a large deposit highlights their value as an essentially untapped library of information to reconstruct deposit evolution, complementing traditional study of selected drill core samples. Systematic investigation of tailings from large deposits can improve genetic models for large copper deposits, including but not restricted to IOCGs, and provide essential insights into REE behaviour, uranium remobilization, and critical metal potential. These findings emphasize the scientific and economic value of tailings-based studies for improved resource characterization, refining metallogenic interpretations, guiding future exploration strategies, and assessing opportunities for reprocessing and metal recovery in large ore systems worldwide across diverse geological settings. Full article

The magmatic Ni-Co-Cu mineralization in the Iken deposit in the central part of the Kun-Manie complex, Amur Oblast, Russia, hosted by an olivine-bearing websterite, is of a low-sulfide type. The fine-grained disseminations of base metal sulfides (BMS), dominantly pyrrhotite, pentlandite (a major source of Ni of industrial importance), and chalcopyrite, are followed by a scarce Pd-Pt-Ag mineralization. Elevated contents of Al in orthopyroxene (mean 2.78 wt.% Al₂O₃) along with Al–Na enrichment in clinopyroxene (diopside; mean 5.10 wt.% Al₂O₃) are associated with highly aluminous compositions of low-chromium members of the spinel–hercynite series. High levels of TiO₂ in kaersutite and titanian phlogopite also reflect a pronounced degree of fractionation of the ore-forming melt. Minor portions of sulfide melt are distributed evenly as a result of immiscibility at advanced stages of orthopyroxene crystallization, after the formation of olivine. Differentiated grains of droplet-like BMS largely settled in situ close to grain boundaries of orthopyroxene or occupied interstitial spaces of pyroxenes and olivine in association with spinel–hercynite and fluorapatite. A combination of late saturation in S with relatively quick cooling rates of the hypabyssal body prevented the effective settlement and accumulation of sulfide droplets in the ore zone. The well-developed lamellae of troilite (Fe₅₀S₅₀) exsolved from the host pyrrhotite Fe₄₈S₅₂ during subsolidus cooling, as a consequence of a low-temperature reaction triggered by a sudden drop in fO₂. An influx of mantle-derived fluid bearing CO₂, CO, and CH₄ with the rising magma could be the primary cause of the fO₂ reduction. Also, graphite-bearing metasedimentary rocks could have been assimilated. Tiny grains of minerals of noble metals (moncheite and merenskyite with essential amounts of melonite component, sperrylite, hessite, alloy Au_63.2Ag_36.8, and argentopentlandite) deposited late in a fluid-enriched medium under submagmatic conditions. Full article

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental contaminants whose mobility in soil and groundwater is strongly controlled by adsorption and desorption processes. In saturated clay-rich soils, these processes are complex because PFASs interact with hydrated mineral surfaces, organic matter, metal oxides, exchangeable cations, and pore-water constituents. This review synthesizes the current literature on PFAS adsorption and desorption in saturated soils, with an emphasis on clay mineralogy, mineral–water interfaces, pore-water chemistry, and electrochemical double layer (EDL) effects. PFAS retention is influenced by molecular properties such as chain length, functional head group, and charge state, as well as soil properties such as organic carbon content, clay mineral type, surface charge, cation exchange capacity, and Fe/Al oxide content. Longer-chain PFASs and sulfonate-based compounds generally show stronger retention, while shorter-chain PFASs tend to remain more mobile. This review focuses particularly on how an EDL affects PFAS behavior in saturated clay systems. Unlike dry clay surfaces, saturated clay surfaces are covered by structured water, exchangeable ions, and diffuse counterion layers. These hydrated interfacial conditions influence how closely anionic PFASs can approach negatively charged clay surfaces, how dissolved cations reduce electrostatic repulsion or promote cation-mediated binding, and how effectively short-range interactions such as hydrophobic association, van der Waals forces, hydrogen bonding, and surface association contribute to adsorption. Desorption is also emphasized because adsorption does not necessarily represent permanent immobilization. Changes in pH, ionic strength, cation composition, dissolved organic matter, or competing solutes can weaken retention and promote PFAS release. Overall, PFAS mobility in saturated clay-rich soils should be interpreted as a coupled interfacial process rather than simple partitioning to soil solids. Future work should better connect molecular-scale mechanisms, EDL behavior, adsorption–desorption experiments, and saturated transport studies to improve predictions of PFAS retention and long-term groundwater release. Full article

Pegmatite-related rare-metal exploration in high-altitude mountainous regions is commonly limited by rugged terrain, complex structural frameworks, and uneven bedrock exposure. This study presents a multi-source remote-sensing workflow for regional-scale rare-metal prospectivity assessment in the Pusharong area of western Sichuan, China, by integrating GF-5A Advanced Hyperspectral Imager (AHSI) data, ASTER thermal infrared (TIR) data, and structural interpretation. GF-5A hyperspectral data were used as the primary source for extracting mineral-related anomaly responses associated with muscovite, tourmaline, cookeite, and spodumene. Mixture Tuned Matched Filtering (MTMF) was applied to enhance weak target-related spectral responses, whereas Spectral Angle Mapper (SAM) provided an independent spectral-consistency constraint to reduce potential over-identification. ASTER TIR-derived Quartz Index (QI) and Feldspar Ratio Index (FRI) responses were used as supplementary lithological and differentiation-related background constraints rather than as continuous quartz–feldspar mineral-distribution maps. Structural interpretation was further integrated to evaluate the spatial relationship between mineral-related anomalies and favourable fault settings. Preliminary point-based validation shows a high degree of consistency between the mapped anomaly zones and available field or geochemical observations, with an overall consistency of 92.86% and a Kappa coefficient of 0.91. The integrated workflow delineated four prospective target zones for follow-up verification, with T1 showing the strongest multi-source support, followed by T2 and T3, whereas T4 is regarded as a lower-priority verification target. These results demonstrate the usefulness of the workflow for first-pass regional target prioritisation in complex mountainous terrain, but the delineated targets require further field, mineralogical, geochemical, and drilling verification before any deposit-scale interpretation can be made. Full article

Artisanal and small-scale gold mining (ASGM) generates complex metal mixtures, yet their biological effects remain poorly characterized in high-altitude populations, where occupational exposure occurs against a hypoxic environmental background. This study evaluated 49 occupationally exposed gold miners from the Vetas–California mining district, near the Santurbán páramo in Colombia, and 25 non-exposed individuals from a comparable high-altitude area. Hair concentrations of essential and toxic elements were quantified by ICP-MS, and serum catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), oxidized glutathione (GSSG), and the GSH/GSSG ratio were assessed. Miners showed a distinct multielement profile, with a higher toxic-metal burden and a dominant mixture mainly characterized by Fe, Mn, As, Pb, Cd, and Hg. CAT and SOD activities did not differ markedly between groups, although SOD activity decreased along the main exposure gradient among exposed workers. In contrast, glutathione-related biomarkers showed a more consistent exposure-related pattern, with higher GSSG and a lower GSH/GSSG ratio, suggesting a shift toward a more oxidized glutathione redox status. Together with positive within-group associations between selected elements and the GSH/GSSG ratio, these results are consistent with a mixture-associated perturbation of glutathione redox homeostasis, with heterogeneous adaptive responses. Overall, this study supports the use of integrated biomonitoring strategies and highlights glutathione-related markers as potential indicators of early redox perturbation in high-altitude mining populations. Full article

Precise control of sinter reducibility is essential for stable blast furnace operation. Each mineral phase present in sinter, such as hematite, magnetite and calcium ferrite exhibits different reducibility. In XRD analysis, the requirement for sample pulverization leads to the loss of mineralogical texture information. This makes it difficult to quantitatively correlate the complex mineral phases present in the sinter with reducibility. This study introduces a novel quantitative approach using hyperspectral imaging to distinguish specific mineral morphologies. Reduction experiments simulating blast furnace thermal and gas conditions were conducted on several sinters. Multiple regression analysis was applied to correlate mineral fractions and macroporosity with reduction rates across three distinct reduction stages. In the low-temperature stage, hematite, macroporosity and acicular calcium ferrites were identified as the primary drivers of reduction. In the intermediate stage, acicular calcium ferrites continued to enhance reactivity, whereas coarse calcium ferrite showed a significant negative influence. In the high-temperature stage, macroporosity strongly promoted reduction, while coarse calcium ferrite and magnetite hindered it due to the formation of shell-like metallic iron structures which impede gas diffusion. These findings demonstrate that hyperspectral imaging combined with multi-stage regression analysis offers a useful tool for designing optimal sinter mineralogy for blast furnace performance. Full article

As a rare metal element, niobium is widely used in steel, electronics, aerospace and many other fields. Eschynite is one of the most important niobium-bearing minerals in Bayan Obo niobium ores. Investigating the beneficiation process and associated reagents is of great significance for improving niobium resource utilization. In this study, mixed ore with eschynite as the main niobium-bearing mineral was used as the research object. Under the condition that the Nb₂O₅ grade of the feed ore was 0.37%, a niobium concentrate with an Nb₂O₅ grade of 5.250% was obtained through one rougher stage and four cleaner stages, followed by magnetic separation. The content of eschynite in the niobium concentrate increased from 0.76% in the run-of-mine ore to 26.32%, with an enrichment ratio of 34.63 times, and the proportion of eschynite in all niobium-bearing minerals rose from 50.67% to 86.10%. Experimental results show that the combined flotation–magnetic separation process can realize the efficient concentration of niobium minerals dominated by eschynite, providing a technical reference for the subsequent development and utilization of eschynite-type niobium ore resources. Full article

The Gebel Shalman-Wadi Biarn (GSh-WB) area in Egypt’s South Eastern Desert hosts NYF-type rare-metal pegmatites with significant U, Th, Nb-Ta, and REEs mineralization. This study integrates field observations, petrography, mineralogy, whole-rock geochemistry, and gamma-ray spectrometry to characterize these pegmatites and evaluate their economic potential. The pegmatites occur as veins, dykes, and zoned pockets hosted entirely within syenogranites. Petrography, pegmatites, and syenogranites are primarily composed of K-feldspar, albite, and quartz with trace amounts of biotite and muscovite. The environmental scanning electron microscope (ESEM) revealed the presence of the following minerals: autunite, kasolite, thorite, monazite-(Ce), parisite, xenotime-(Y), ferrocolumbite, hydroxyplumbobrtafite, aeschynite-(Y), and zircon, which are the major U-Th, Nb-Ta, and REE-bearing minerals. Additionally, gold, cassiterite, wolframite, pyrrhotite, chalcopyrite, and brass alloy were identified as sources of precious and base metals. Both groups’ chondrite-normalized REE patterns, which display slightly elevated LREE patterns and negative Eu anomalies, point to fractional crystallization involving plagioclase fractionation. Consequently, pegmatite and syenogranites are believed to have mostly formed from the partial melting of a reconstituted juvenile crust and its weathered sediments associated with Neoproterozoic magmatism. The marginally positive Ce anomaly in the (GSh-WB) pegmatites (1.02–0.98) may be associated with monazite crystallization resulting from enhanced fractionation. The Th and U levels range from 101 to 28.6 ppm and from 51 to 5.8 ppm, respectively. The magnitude of the tetrad effect in the rare earth elements of the analyzed rocks exceeds one (T1 = 1.12–1.02, T3 = 0.92–1.08, and T1,3 = 1.01–1.05), suggesting an M-type tetrad effect. The presence of this tetrad effect is indicative of granite that has been significantly altered by hydrothermal processes and is extensively fractionated. Chondrite-normalized REE patterns of the pegmatites (average ΣREE = 439 ppm) and their host syenogranites (average ΣREE = 192 ppm) show similar trends characterized by enrichment of light rare earth elements (LREEs) relative to heavy rare earth elements (HREEs) and pronounced negative Eu anomalies (Eu/Eu* = 0.09–0.22). These features, together with negative Sr and Ba anomalies, likely reflect extensive fractional crystallization of feldspars and feature anorogenic rocks. Spectrometric analysis reveals eU values of 2.0–288 ppm and eTh values of 7.0–455 ppm in pegmatite samples, with eU/eTh ratios (0.49–0.39) exceeding the typical continental crust value of 0.25, indicating uranium enrichment. Both magmatic and hydrothermal processes contributed to the observed radioactivity. The spatial distribution of uranium shows lithological and structural controls. The GSh-WB pegmatites represent a potential target for uranium exploration. Full article

The discharge of pesticide residues (PRs) from agricultural activities into water bodies has raised concerns about their toxicity to humans and the ecosystem. Traditional methods such as adsorption, membrane filtration, biological treatment, and conventional filtration usually result in incomplete removal of PRs. Currently, removal of PRs using advanced oxidation processes, particularly metal oxide-based photocatalysts, is considered a promising way. This review provides a comprehensive overview of recent advances in the photocatalytic degradation of PRs using TiO₂-based photocatalysts (T-BPs), the most widely investigated metal-oxide photocatalyst systems. First, we discuss the distribution, types, and negative impacts of major PRs on humans and the ecosystem. Next, we explore modification methods to enhance the properties of T-BPs, including light absorption behavior, charge separation rate, and photocatalytic degradation performance toward PRs. Afterward, this review carefully examines current challenges, such as complex water matrices, T-BP stability, energy supply for photocatalysis, and toxicity reduction. Finally, we highlight key future research directions, like the development of visible light-driven photocatalysts, enhanced mineralization efficiency, reduced secondary environmental risks, and the design of highly reliable catalyst and reactor systems for sustainable large-scale applications. Full article

Traditional electro-Fenton systems for chlorinated antibiotic wastewater suffer from low mineralization, catalyst deactivation, and secondary pollution caused by chloride ions. In this work, nitrogen-functionalized graphite felt cathodes were synthesized by electrodeposition-pyrolysis. Pyridinic N and graphitic N were identified by XPS. The obtained cathodes were employed in a metal-free electro-Fenton system for effective tetracycline (TC) removal and mineralization. The results show that the optimal electrode (N-GF-3) achieved 93% degradation efficiency and 73% mineralization of TC in 60 min, when the optimized conditions (pH = 3 and current density = 20 mA/cm²) were employed. Unusually, with the presence of Cl⁻, the system showed even higher catalytic performance, having a degradation kinetic constant 2.4 times higher than that without chloride. The electrode was also reusable, maintaining a TC degradation efficiency above 90% in the fifth cycle. Based on fluorescence analysis of ·OH, a possible dual-path reaction mechanism is proposed. This mechanism provides new insights into designing advanced oxidation processes for the treatment of complex chlorinated organic wastewater. Nevertheless, the potential formation of chlorinated byproducts requires additional investigation. Full article

Infectious prion adsorption on metal, minerals, wood, and plastic is well documented, raising the specter of food safety hazards for meat packing workers, sport hunters, and consumers. We previously demonstrated that sodium hypochlorite, and to a lesser extent, potassium peroxymonosulfate, and hypochlorous acid can decontaminate prion-contaminated nonporous surfaces. However, the extent to which chemical aging of surfaces affects subsequent recoverable prion seeding activity is unknown. In this study, we investigated the potential for four chemical decontaminants known for their anti-prion activity (sodium hypochlorite [bleach], hypochlorous acid [Briotech], potassium peroxymonosulfate [Virkon-S], and Wex-Cide-128) to alter the surfaces of steel knives and the subsequent prion decontamination efficacy of each. We found that hypochlorous acid, sodium hypochlorite, and potassium peroxymonosulfate corrode the surfaces of steel knives, resulting in significant physical alterations. Knives exposed to hypochlorous acid exhibited the most substantial corrosion (rust), which is consistent with its oxidizing effects. Oxidation of the knife surface was corroborated by complementary energy-dispersive X-ray spectroscopy data trends. Scanning electron microscopy data indicate corrosion is apparent after minimal exposure to oxidizing agents. Finally, we used the real-time quaking-induced conversion assay on swabs collected from chemically aged knife surfaces to evaluate recoverable surface-associated CWD-prion seeding activity detected by RT-QuIC after prion exposure and decontamination. Our results indicate decreased recoverable prion seeding activity from knife surfaces aged with 40% bleach. We also observed some recoverable seeding activity post-decontamination on knives chemically aged with 10% bleach and Wex-Cide-128, but largely similar efficacy to prior studies. This implies that existing chemical prion decontaminants are likely effective after repeated use on steel surfaces. Full article

During the continuous casting of high-titanium steel, traditional fluorine-containing mold fluxes are prone to causing fluoride contamination, equipment corrosion, and intensified slag–metal interface reactions. There is an urgent need to develop highly adaptable fluorine-free mold flux systems. In this study, titanium-containing blast furnace slag was used as the primary base material, while borax, soda ash, and witherite were selected as fluoride-substituting mineral raw materials. The effects of these mineral raw materials on the melting properties, crystallization behavior, crystalline phases, and microstructure of fluorine-free mold fluxes were systematically investigated, and an optimized mold flux design suitable for continuous casting of high-titanium steel was further developed. The results indicate that borax significantly reduces the melting temperature and viscosity and markedly suppresses the growth of crystalline phases such as calcium borosilicate, nepheline, and perovskite by weakening the polymerization degree of the silicate network, thereby substantially decreasing the crystallization ability of the mold flux. Soda ash primarily acts as a strong fluxing and network-depolymerizing agent, promoting the formation of low-polymerized structural units. It also enhances the tendency toward ordered atomic arrangement, thereby markedly increasing nepheline precipitation and the overall crystallization ratio. Witherite exerts a relatively mild effect on slag structure and phase evolution; its moderate addition helps synergistically reduce the melting point, viscosity, and crystallization ratio, thereby supporting performance stability. The optimized fluorine-free mold flux, designed on the basis of these findings, maintains a suitable initial crystallization temperature and critical crystallization cooling rate while exhibiting lower melting temperature, viscosity, and crystallization ratio than conventional fluorine-bearing flux. The findings establish a theoretical basis for designing eco-friendly mold fluxes suitable for high-titanium steel and for enhancing billet quality. Full article

Glyphosate, the most extensively used herbicide worldwide, is frequently detected in aquatic environments due to its high solubility, persistence, and intensive agricultural application. Its occurrence, together with that of its principal metabolite aminomethylphosphonic acid (AMPA), raises substantial environmental and public health concerns. Conventional water treatment technologies generally exhibit limited efficiency in achieving complete removal and mineralization of this compound. In recent years, advanced electrochemical oxidation processes, and particularly anodic oxidation, have emerged as promising alternatives owing to their ability to generate highly reactive hydroxyl radicals in situ. This review provides the first contaminant-specific and mechanistic assessment dedicated exclusively to the anodic electro-oxidation of glyphosate. In contrast to previous reviews offering broad surveys of electrode materials or generalized evaluations of glyphosate treatment technologies, this work synthesizes all mechanistic, kinetic, and material-dependent insights reported between 2016 and 2025. A comparative analysis of major anode families (including boron-doped diamond (BDD), ${\mathrm{P}\mathrm{b}\mathrm{O}}_2$, mixed-metal oxides, and Magnéli-phase Ti₄O₇) is presented, highlighting glyphosate-specific degradation pathways, intermediate formation, and the operational parameters controlling mineralization efficiency and energy demand. By establishing a structured framework that links electrode properties, radical-generation mechanisms, and pollutant-specific degradation chemistry, this review addresses a critical gap in the literature and provides a scientific basis for designing next-generation electrochemical processes for the efficient and sustainable removal of glyphosate and related organophosphorus contaminants. Full article

Pegmatite dikes are important prospecting indicators for rare-metal deposits, whereas traditional methods for pegmatite dike identification are constrained by the limited capability of human visual interpretation to capture information from remote sensing imagery, resulting in low identification accuracy and efficiency. In recent years, global research on semantic segmentation of different surface features and remote sensing-based mineral exploration using deep learning methods and high-resolution remote sensing imagery has made significant progress; however, studies on surface-exposed geological bodies such as pegmatite dikes remain highly insufficient. To address the key problem of efficiently identifying pegmatite dikes in remote sensing imagery, this study proposes an improved model based on UNet++, termed GAD-UNet++. In the field of remote sensing geology, this study constructed a pegmatite dike semantic segmentation dataset based on high-resolution RGB imagery by using 0.66 m RGB imagery for visual delineation and ZY1F hyperspectral data for spectral constraint and label refinement; on this basis, semantic segmentation of surface pegmatite dikes in the Yilanlike area of the South Tianshan Mountains, Xinjiang, was conducted using RGB remote sensing image patches as model input. Specifically, because pegmatite dikes are small targets characterized by slender structures, indistinct boundaries, and sparse regional distribution, this study introduced a lightweight feature extraction structure (GhostNetV2) and a long-range dependency attention module (DFC) at the encoder stage, and further incorporated the Coordinate Attention module (CA) to enhance spatial localization and boundary representation of the targets. Finally, focal cross-entropy loss and a deep supervision strategy were adopted to improve the accuracy of semantic information extraction for pegmatite dikes, as well as the training stability and segmentation accuracy under class-imbalance conditions. The results show that the proposed model achieved an mIoU of 93.11% and an F1-score of 94.95% on the test set. Compared with existing semantic segmentation models, the proposed model achieved superior performance in both identification accuracy and computational efficiency for pegmatite dikes. In addition, this study delineated 18 potential pegmatite dike enrichment zones in the Yilanlike area, providing technical support for remote sensing-based rare-metal prospecting and geological interpretation in the study area. Full article