Search Results (1,190)

Phosphorites are a vital source of phosphorus for agricultural and industrial applications and are increasingly recognized for their potential as secondary repositories of critical raw materials (CRMs) such as rare earth elements plus yttrium (REYs). This study investigates deep-sea phosphorites from the Galicia Bank, Madeira, and Canary Seamounts, in the NE Atlantic Ocean, which are spatially associated with ferromanganese (Fe-Mn) mineralization. Through integrated petrographic, geochemical, and in situ isotopic analyses (O and Sr), we assess the timing, processes, and paleoenvironmental conditions of phosphogenesis and its implications for CRM enrichment. Rare earth element patterns in apatite reflect a predominant seawater-derived signature with variable Ce anomalies. Nevertheless, variable Y/Ho ratios point to evolving fluid sources including a hydrogenous component (directly derived from seawater), modified porewaters and, locally, volcanic or possibly hydrothermal inputs. Oxygen and strontium isotope compositions constrain phosphogenesis to several episodes ranging from the Upper Cretaceous to the Middle Miocene, with distinct isotopic shifts identifying both primary formation and later overprinting processes mostly linked to Fe-Mn oxyhydroxide growth or volcanic–hydrothermal activity. These findings highlight the dynamic and multiphase nature of phosphorite formation in deep-marine settings. The integration of high-resolution geochemical and isotopic tools proves essential for reconstructing genetic histories, defining metallogenic context and evaluating CRM prospectivity in complex submarine systems. Full article

This paper presents the results of apatite fission-track (AFT) and zircon fission-track (ZFT) analysis (dating) on samples collected from the surface exposures of six Precambrian intrusions in the southeastern Fennoscandian Shield: the Avdeevo and Shala dykes, the Valaam sill, the Salmi and Wiborg batholiths, and the Kuznechenskii massif. The short mean track lengths in apatite (10.7–13.5 μm) indicate that the studied rocks resided for a prolonged period within the apatite partial annealing zone (APAZ, 60–120 °C). We suggest that the AFT ages obtained from two of the granitic intrusions—the Salmi batholith and the Kuznechenskii massif—are apparent due to α-radiation-enhanced annealing (REA), as evidenced by an inverse correlation between single-grain AFT age and effective uranium (eU) concentration, and high dispersion and a negative chi-square test. An attempt to minimize the contribution of the REA effect to the AFT data for the Salmi batholith allowed its AFT age to be estimated as 1251 ± 125 (2σ) Ma, but the same approach was unsuccessful for the Kuznechenskii massif. In contrast, the mafic intrusions show no such correlation and yield reliable AFT ages: the Avdeevo dyke, 1040 ± 104 Ma; the Shala dyke, 1145 ± 89 Ma; and the Valaam sill, 1184 ± 78 Ma. The AFT data from the Wiborg batholith can be regarded as preliminary only. The most reliable AFT ages and thermal evolution models for the studied intrusions are similar and indicate prolonged exhumation of the intrusions to the surface over more than 1 billion years, with a marked increase in cooling rates around 300 Ma, which possibly has far-field causes, such as mantle dynamics related to the initial fragmentation of Pangea. Our data, as a first approximation, suggest a similar tectono–thermal evolution for intrusions located both within the northeastern margin of the Svecofennian orogen and on the Archean Karelian craton. Full article

Volcanic rocks of the Qi’eshan Group, which are widely distributed in the Dananhu arc of the Eastern Tianshan, NW China, have long been debated in terms of their formation age and tectonic setting. In this study, we conducted an integrated study of U-Pb apatite geochronology, whole-rock major and trace element geochemistry, in situ major element analyses of clinopyroxene, and “Rhyolite-MELTS” thermodynamic modeling on the basalts from the Qi’eshan Group. Geochronological data show that the weighted mean of ²⁰⁶Pb/²³⁸U ages of apatite is 329 ± 10 Ma. The basalts belong to the tholeiitic series and are characterized by enrichment in large ion lithophile elements (LILEs), depletion in high field strength elements (HFSEs), and enrichment of light rare earth elements (LREEs) relative to heavy rare earth elements (HREEs) with weak negative Eu anomalies. They were derived by partial melting of garnet-spinel lherzolite in a depleted mantle source metasomatized by subduction-related fluids, followed by fractional crystallization of spinel, olivine, and clinopyroxene. Clinopyroxene is dominated by augite, characterized by high Mg and Ca contents and low Al and Na contents. Machine-learning-based thermobarometry indicates that clinopyroxene crystallized at temperatures of 1027–1033 °C and pressures of 1.1–1.6 kbar. “Rhyolite-MELTS” isobaric crystallization simulations suggest that mantle-derived magma, with an initial water content of 4 wt.% and oxygen fugacity of FMQ, can generate melts compositionally similar to the volcanic rocks of the Qi’eshan Group through fractional crystallization at a pressure of 1.5 kbar. Combined with previous studies, we propose that the Qi’eshan Group basalts formed in an extensional arc setting related to southward rollback of the northward-subducting Kanguer oceanic slab, which caused asthenosphere upwelling and lithospheric extension, thereby promoting partial melting of the subduction-metasomatized mantle. Our data provide new insights into the Carboniferous rollback of the Kanguer oceanic slab in the northern part of the Eastern Tianshan. Full article

Untreated dental caries in permanent teeth is the most frequent disease of all 371 diseases and traumas assessed by the Global Burden of Disease Study in 2021, and there are reported to be 2.24 billion cases worldwide. Demineralization is a disintegration process of minerals and apatite crystals in hard tissue, provoked by biofilm activities, dietary factors, and the micro-oral environment—the three main mechanisms of dental caries. Restoration of mineral ions in the crystal structure is defined as remineralization. Remineralization enables the deposition of new minerals within the crystal structure of demineralized enamel, aiming to increase mineral production. Environments suitable for remineralization and inhibiting demineralization could be created by using a caries prevention agent. Objectives: Providing scientific evidence regarding Aloe vera as an alternative agent for caries prevention. Materials and Method: The method used in this study is a scoping review, utilizing the PRISMA-ScR as a guideline to conduct article screening and further analysis, following a thematic analysis approach. Database searches were conducted in PubMed, EBSCOhost, and ScienceDirect, based on the keywords generated. Results: A total of 13 articles were gathered for further analysis. Conclusions: Aloe vera shows promising preliminary potential, but further standardized in vivo and randomized clinical studies are necessary to confirm its remineralizing efficacy and clarify its mechanisms of action as a cavity prevention agent. Clinical Relevance: Using Aloe vera as an alternative caries prevention agent. Full article

This research reports on the properties of oxide-ceramic coatings produced by plasma electrolytic oxidation in novel electrolyte solutions for implantology applications. A series of bioactive calcium-phosphate coatings was synthesized on medical-grade Ti-13Zr-13Nb alloy using the plasma electrolytic oxidation (PEO) method. Novel electrolytes enriched with calcium and phosphorus were developed, enabling the formation of coatings with tailored physicochemical and structural characteristics. A correlation was established between the electrolyte composition and the phase composition, thickness, morphology, porosity, and microhardness of the resulting coatings. The optimum coatings exhibited a Ca/P ratio close to that of natural human bone tissue, homogeneity, a well-developed porous surface topography, and controlled resorption behavior. For the first time, a mechanism of calcium-phosphate coating resorption in a biologically active environment has been proposed. It involves partial dissolution, the formation of apatite-like surface structures, and the subsequent controlled release of Ca and P ions. In vitro testing in simulated body fluid indicated the potential bioactivity of the synthesized coatings. The proposed calcium-phosphate coatings may be considered promising candidates for future implant surface modification. The results obtained are significant for the development of advanced orthopedic and dental implants, including those fabricated using additive manufacturing technologies. Full article

The development of multifunctional biomaterials for bone repair requires precursors that combine bioactivity, moderate antimicrobial growth-inhibitory effect, and imaging. This study demonstrates the multifunctional versatility of a single family of rare-earth-doped β-tricalcium phosphates (β-TCPs), Ca₉Eu(PO₄)₇ and Ca₉Dy(PO₄)₇, across three distinct formats: bioactive thin films (for implant coatings), brushite cements (for injectable bone fillers), and radiopaque PMMA bone composites (for load-bearing applications). This work serves as a proof-of-concept that the same doped phosphate precursors can address different clinical needs while retaining bioactivity, antimicrobial properties, and radiopacity. The phosphate precursors were synthesized via solid-state reaction. Pulsed laser deposition (PLD) was used to form amorphous, dense, and crack-free coatings, which exhibited excellent in vitro bioactivity through the rapid dissolution–reprecipitation of a carbonated apatite layer in simulated body fluid. The brushite-based bone cements were produced from doped β-TCPs. These cements demonstrated high cytocompatibility with mesenchymal stromal cells (>89% viability) and significantly enhanced osteogenic differentiation with antimicrobial activity against common pathogens (S. aureus, E. coli, P. aeruginosa). Furthermore, incorporation of these phosphates as fillers into PMMA bone cement resulted in a homogeneous particle distribution with reduced agglomeration compared to undoped β-TCPs, achieving clinically relevant radiopacity values (913 ± 22.4 HU for Dy-doped sample). Post-mortem studies by the CT method were performed on the vertebrae with PMMA–phosphate composites and brushite cements. It was shown that brushite cement in ovine lumbar vertebrae defects exhibited the highest radiopacity (1450–1550 ± 25 HU). The findings establish rare-earth-doped β-TCP as a unified multifunctional precursor that imparts bioactivity, the ability to support in vitro mineralization, antimicrobial properties, and enhanced radiopacity to thin films, phosphate cements, and polymer composite materials. Full article

Skin injuries are common and can result from surgeries, burns, pressure sores, cuts, and diseases. Proper wound healing is crucial for maintaining homeostasis; wounds can be classified as acute or chronic. Acute wounds heal in four sequential phases: hemostasis, inflammation, proliferation, and remodeling. Chronic wounds arise when this process fails, often due to prolonged inflammation. Existing treatments for chronic wounds are limited, and antibiotic resistance complicates infection control, highlighting the urgent need for new therapies. Biomaterials, particularly gelatin, have gained attention for their biomimetic properties, biocompatibility, and ability to promote healing. Gelatin’s ECM-like structure supports tissue metabolism, and it can be enriched with bioactive compounds to enhance tissue regeneration, collagen deposition, angiogenesis, and antimicrobial activity. This study evaluates the effectiveness of a 3D gelatin-based patch in vivo, using Hirudo verbana as a model. The patch, functionalized with chitosan and bioactive apatite nanoparticles, was implanted in injured leeches, with tissue samples collected at 72 h, 1 week, and 2 weeks. Scaffold integration, cell colonization, and healing effects were assessed through morphological, immunohistochemical, and ultrastructural analyses. The findings confirm H. verbana as a robust in vivo model for regenerative medicine and demonstrate the promising potential of gelatin-based patches. Full article

We report the first low-temperature thermochronologic data from the Oregon Coast Range. This includes apatite and zircon fission-track data from fifteen samples of the Umpqua Group and Dothan Formation collected across the Wildlife Safari Fault near Roseburg, Oregon. This structure marks the boundary between the Siletzia terrane and the Klamath Mountains Province, where collision and accretion at 51–49 Ma produced a fold-and-thrust belt. Our sampling was designed to test whether fission track thermochronometry records structurally controlled exhumation across this fault during Siletzia accretion. The data fail to support this hypothesis. Instead, apatite fission track ages define a single thermally reset population at 45.3 ± 1.1 Ma that is uniform across all sampled stratigraphic and structural positions. Unimodal, moderately shortened track lengths (12.5–14.1 μm) record protracted cooling through the apatite partial annealing zone. Zircon fission track data show a time-continuous partial annealing pattern with youngest grain ages of 49–43 Ma, indicating temperatures reached at least the lower zircon partial annealing zone. These data record a regionally pervasive mid-Eocene thermal event that we interpret as syn-collisional heating followed by protracted cooling. Full article

This study investigates the composition, morphology and cultural significance of red pigment traces identified on bone pointed tools discovered in the Chalcolithic tell settlement of Pietrele–Măgura Gorgana, attributed to the Kodjadermen–Gumelnița–Karanovo VI cultural complex (4600–4250 BC). The observed use-wear patterns are consistent with repeated contact with soft, non-abrasive materials, including hide working, pigment application on leather or other organic surfaces, fiber manipulation, and perforation of soft substrates. Use-wear analysis revealed polished and flattened distal ends, compatible with repeated use on soft, non-abrasive materials, such as hide, leather, fiber, or other organic substrates. The possibility of pigment application directly on skin, in a practice analogous to tattooing, as previously published, cannot be excluded but remains speculative in the absence of experimental reference data or residue evidence specifically linked to such use. An associated ceramic container was tentatively interpreted as a possible vessel for ochre preparation, suggesting local processing of the pigment. The artifacts were investigated using multi-analytical archaeometric methods: SEM-EDS, AFM, TEM, FTIR, Raman, TGA, CLSM and pseudo-color image segmentation and 3D rendering of porosity distribution. The results consistently identified an iron oxide-based pigment, dominated by hematite and/or goethite, specific to ochre. Pigment particles (50–300 nm) form a well-defined superficial layer on the bone substrate, without Fe–Ca reactions at the interface. The simultaneous presence of Ca, P, Si, Mg and K indicates a silicate matrix with an apatite component, compatible with local and poorly purified raw materials. CIELAB colorimetric analyses revealed significant chromatic variability, suggesting the use of hematite-rich pigments and possible thermal transformations of goethite. The results contribute to the understanding of the pigment technologies of the Chalcolithic communities of the Lower Danube. Full article

Most existing dental restorative materials exhibit limited bioactivity, insufficient acid resistance, and poor mechanical compatibility with natural tooth structures. This study involved an in vitro approach in which a biomimetic fluoride-modified functionally gradient dental restorative material was prepared from sol–gel-derived mesoporous silica through mineralization induced via SBF solution. They synthesized bioactive restorative materials by introducing silica into a simulated body fluid (SBF) for biomimetic mineralization and generating hydroxyapatite on the silica surface. XRD, FTIR, SEM, and EDS analyses confirmed the presence of hydroxyapatite and fluorapatite-like phases. The results showed statistically significant improvements (p < 0.05) in the mechanical properties. The surface hardness of the developed restorative system ranged from 214 HV for the prepared silica to 392 HV for the fluoride-modified specimens. Biomimetic mineralization and fluoride modification increased the shear bond strength to dentin substrates from 9.2 MPa to 21.4 MPa and the wear from 12.8 mg to 3.6 mg, respectively. Acid resistance evaluation also showed that the specimens with fluoride modification had the highest value of hardness retention (92.1%) after acid resistance due to the formation of chemically stable and dense apatite-rich layers on the surface. The functionally graded structure demonstrated a partial biomimetic resemblance to certain hierarchical and functional characteristics of natural dental tissues under in vitro conditions. In vitro studies on bioactivity, mechanical properties, and resistance to acidic environments of the synthesized restorative showed promising results for future dental restoration applications. Full article

Organic-rich shales in China’s deep-water shelf environments possess significant shale gas resource potential. To investigate the reservoir development characteristics of deep-water shelf shale, 143 shale samples were collected from the low-maturity Xiamaling Formation in the Zhangjiakou area and the high to over-mature Wufeng–Longmaxi Formations in the southeastern margin of the Sichuan Basin. Basic analytical methods, including X-ray diffraction (XRD), total organic carbon (TOC) analysis, rock pyrolysis, and solid bitumen reflectance measurements, were employed alongside advanced reservoir characterization techniques such as field-emission scanning electron microscopy (FE-SEM), low-pressure CO₂/N₂ physisorption, mercury intrusion porosimetry (MIP), and focused ion beam scanning electron microscopy (FIB-SEM). This study focuses on the petrographical, geochemical, and microscopic pore structure characteristics of these marine shales. The results indicate that the mineral composition of deep-water shelf sedimentary shale is dominated by quartz, clay minerals, feldspar, calcite, dolomite, apatite, and pyrite, with quartz being the most abundant. The Xiamaling Formation shales, at low maturity, are relatively rich in siliceous components, while the high to over-mature Wufeng and Longmaxi Formation shales are richer in carbonate components. The kerogen type of organic matter in the Xiamaling Formation is primarily Types II₁ and II₂, whereas the Wufeng–Longmaxi shales are predominantly Types I and II₁. TOC content is highest in the Wufeng Formation, followed by the Longmaxi Formation, with the Xiamaling Formation exhibiting the lowest TOC levels. Pore development in the Wufeng and Longmaxi shales is significantly superior to that in the Xiamaling shales. Overall, the Wufeng and Longmaxi Formations demonstrate more favorable pore characteristics and hydrocarbon generation potential compared to the Xiamaling Formation. The Wufeng and Longmaxi Formations’ shales will be the key targets for shale gas exploration in the future. The findings of this study contribute to the understanding and development of theories of marine shale gas accumulation in China and hold both theoretical and practical significance for the efficient and rational exploitation of shale oil and gas resources. Full article

Flotation is a fundamental unit operation in mineral processing; however, achieving high selectivity while reducing the environmental impact of reagents remains a major challenge in phosphate ore beneficiation. Conventional depressants often exhibit limited selectivity and may pose environmental concerns, highlighting the need for sustainable alternatives. This study reports, for the first time, the application of starch nanostructures derived from potato pulp processing residues as a depressant in phosphate flotation, representing an innovative and eco-friendly approach. An exploratory and experimental methodology was adopted, including nanostarch synthesis via acid hydrolysis followed by centrifugation and sonication, as well as comprehensive physicochemical characterization. The primary objective was to evaluate the selective depressant performance of the nanomaterial in apatite–calcite flotation systems. The synthesized nanostructures exhibited particle diameters ranging from 179 to 443.6 nm. Microflotation tests conducted in a Hallimond tube using pure mineral samples under alkaline conditions (pH ≈ 9), at a depressant dosage of 500 mg/L and in combination with a plant-based fatty acid collector, revealed a pronounced selectivity window, resulting in an approximately 77% difference in flotation recovery between apatite and calcite. These findings demonstrate that nanostarch derived from agro-industrial residues is a promising, biodegradable, and sustainable depressant capable of enhancing selectivity in phosphate flotation. The results contribute to the advancement of greener mineral processing Technologies, although Further studies are required to elucidate the underlying interaction mechanisms. Full article

Polymerization shrinkage remains a primary cause of marginal failure in posterior composite restorations, contributing to interfacial gap formation and secondary caries development. Bioactive filler technologies represent a paradigm shift, offering simultaneous stress reduction and therapeutic ion release through engineered matrix–filler interactions. This narrative review synthesizes current evidence on how bioactive glass (including 45S5), amorphous calcium phosphate, and surface pre-reacted glass-ionomer fillers modulate polymerization shrinkage dynamics and mechanical performance in bulk-fill systems. These systems exhibit distinct mechanisms of bioactivity, with bioactive glass (45S5) promoting ion release and apatite formation, amorphous calcium phosphate (ACP) enabling rapid calcium phosphate ion delivery for remineralization, and surface pre-reacted glass-ionomer (S-PRG) fillers providing sustained multi-ion release with buffering and antibacterial potential. A comprehensive literature search was conducted in PubMed/MEDLINE, Scopus, and Web of Science for studies published up to June 2025, including experimental investigations and reviews assessing bioactive filler integration, with studies selected based on predefined inclusion and exclusion criteria focusing on relevance and reported outcomes. The available evidence indicates that optimized bioactive formulations reduce shrinkage stress by approximately 25–40%, decreasing from 35–40 MPa in conventional systems to 22–32 MPa in bioactive bulk-fill composites while maintaining flexural strength above 100 MPa and elastic modulus within clinically acceptable ranges (11–13 GPa). However, substantial heterogeneity in filler chemistry, loading protocols, and testing methodologies limits cross-study comparisons. This variability also reflects differences in testing conditions, material compositions, and evaluation protocols across studies. Full article

In this study, a streptomycin sulfate-loaded bioactive glass/chitosan (STRS–BG/CH) composite scaffold was fabricated via an improved unidirectional freeze-drying method, with drug loadings of 20–40%. The scaffolds were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis before and after in vitro testing. Antibacterial efficacy was evaluated against Gram-positive (Enterococcus faecalis, Staphylococcus aureus) and Gram-negative (Klebsiella pneumoniae, Escherichia coli) microorganisms via the agar diffusion method. The STRS–BG/CH scaffolds exhibited highly interconnected porous structures, prolonged antibacterial activity, and enhanced apatite-forming ability in vitro. Compared with bead-based carriers, scaffold-based systems provide enhanced structural integrity and interconnected porosity, which are advantageous for sustained drug release, apatite formation, and tissue integration. Accordingly, these multifunctional scaffolds may simultaneously provide localized antibacterial activity and potential relevance to bone tissue engineering applications. The prepared STRS–BG/CH scaffolds functioned as controlled release carriers for streptomycin sulfate while simultaneously maintaining antibacterial efficacy and bioactive performance. These results illustrate the importance of STRS–BG/CH scaffolds as a promising antibacterial bioactive scaffold system, warranting further biological investigation. Full article

The Niutougou ore area (~31 t Au) is located in the Xiong’ershan district at the southern margin of the North China Craton (NCC). From north to south, the Niutougou ore area is divided into three main parts, corresponding to the gold deposits in the Songligou altered rocks, the J25-J26 breccia, the Vein VII lode gold deposit, and the Shangzhuang altered rocks. The timing of gold mineralization and the formation age of the J26 breccia pipe have not been well constrained in this ore area. Hydrothermal xenotime and apatite are closely related to gold mineralization. The in situ xenotime U–Pb ages of the J26 breccia pipe and Vein VII show U–Pb lower intercept ages of 151.2 ± 2.0 Ma and 155.9 ± 1.6 Ma, respectively. The in situ U–Pb age of the Shangzhuang apatite shows a U–Pb lower intercept ages of 153.4 ± 2.6 Ma. The U–Pb concordia ages and weighted mean ages of the cement zircons from the J26 breccia pipe are 155.8 ± 0.4 Ma, and 155.9 ± 0.8 Ma, respectively, determined via sensitive high-resolution ion microprobe (SHRIMP) analysis. The molybdenite veins in the J26 breccia pipe cut the cement and different types of breccia and have a Re–Os isochron age of 155.9 ± 2.9 Ma and weighted mean age of 155.9 ± 1.1 Ma. Thus, the formation age of the breccia pipe is Late Jurassic. The subduction of the paleo-Pacific Plate beneath the NCC and the back-arc extensional setting in the Late Jurassic might have caused gold mineralization in the southern margin of the NCC. Full article