Search Results (100)

Hydrogen, as the smallest atom and a key component of water, can penetrate minerals in various forms (e.g., atoms, molecules), significantly influencing their properties. The hydrogen diffusion behavior in corundum (α-Al₂O₃) under high pressure was systematically investigated using the DFT + NEB method. The results indicate that H atoms tend to aggregate into H₂ molecules within corundum under both ambient and high-pressure conditions. However, hydrogen predominantly migrates in its atomic form (H) under both low- and high-pressure environments. The energy barriers for H and H₂ diffusion increase with pressure, and hydrogen diffusion weakens the chemical bonds nearby. Using the Arrhenius equation, we calculated the diffusion coefficient of H in corundum, which increases with temperature but decreases with pressure. On geological time scales, hydrogen diffusion is relatively slow, potentially resulting in a heterogeneous distribution of water in the lower mantle. These findings provide novel insights into hydrogen diffusion mechanisms in corundum under extreme conditions, with significant implications for hydrogen behavior in mantle minerals at high pressures. Full article

In this article, we consider the roles of transcrustal magma- and fluid-conducting faults (TCMFCFs) in the formation of mineral deposits, showing the importance of deep sources of heat and hydrothermal solutions in the genesis and history of deposit formation. As a result of the impact on the lithosphere of mantle plumes rising along TCMFCFs, intense block deformations and tectonic movements are generated; rift systems, and volcanic–plutonic belts spatially combined with them, are formed; and intrusive bodies are introduced. These processes cause epithermal ore formation as a consequence of the impact of mantle plumes rising along TCMFCF to the lithosphere. At hydrocarbon fields, they play extremely important roles in conductive and convective heat, as well as in mass transfer to the area of hydrocarbon generation, determining the relationship between the processes of lithogenesis and tectogenesis, and activating the generation of hydrocarbons from oil and gas source rock. Detection of TCMFCFs was carried out using MMSS (the method of microseismic sounding) and MTSM (the magnetotelluric sounding method), in combination with other geological and geophysical data. Practical examples are provided for mineral deposits where subvertical transcrustal columns of increased permeability, traced to considerable depths, have been found; the nature of these unique structures is related to faults of pre-Paleozoic emplacement, which determined the fragmentation of the sub-crystalline structure of the Earth and later, while developing, inherited the conditions of volumetric fluid dynamics, where the residual forms of functioning of fluid-conducting thermohydrocolumns are granitoid batholiths and other magmatic bodies. Experimental modeling of deep processes allowed us to identify the quantum character of crystal structure interactions of minerals with “inert” gases under elevated thermobaric conditions. The roles of helium, nitrogen, and hydrogen in changing the physical properties of rocks, in accordance with their intrastructural diffusion, has been clarified; as a result of low-energy impact, stress fields are formed in the solid rock skeleton, the structures and textures of rocks are rearranged, and general porosity develops. As the pressure increases, energetic interactions intensify, leading to deformations, phase transitions, and the formation of chemical bonds under the conditions of an unstable geological environment, instability which grows with increasing gas saturation, pressure, and temperature. The processes of heat and mass transfer through TCMFCFs to the Earth’s surface occur in stages, accompanied by a release of energy that can manifest as explosions on the surface, in coal and ore mines, and during earthquakes and volcanic eruptions. Full article

The Kesikköprü iron deposit, located in the Central Anatolian Crystalline Complex, occurs in the triple contact of Kesikköprü granitoid, mafic–ultramafic rocks, and marble. The causative Kesikköprü granitoid, consisting of diorite, granodiorite, and granite, is classified as sub-alkaline, calc-alkaline, and shoshonitic, displaying metaluminous to partially peraluminous properties. Sr-Nd isotope data and the geochemical characteristics of the Kesikköprü granitoid indicate a metasomatized mantle origin, with its ultimate composition arising from crustal contamination and magma mixing along with fractional crystallization in a post-collisional setting. The ⁴⁰Ar/³⁹Ar geochronology reveals a total fusion age of 73.41 ± 0.32 Ma for the biotite of the Kesikköprü granitoid. The alteration pattern in the deposit is characterized by an endoskarn zone comprising garnet–pyroxene (±phlogopite ± epidote) and an exoskarn zone displaying a zoning of garnet (±pyroxene ± phlogopite), pyroxene (±garnet ± phlogopite ± epidote), epidote–garnet, and epidote-rich subzones. Magnetite is extracted from massive lenses within the exoskarn zones and shows vein, disseminated, banded, massive, and brecciated textures. The low potassium content of phlogopites which are associated with magnetite mineralization prevents the determination of a reliable alteration age. δ¹⁸O thermometry reveals a temperature range between 462 and 528 °C for the magnetite mineralization. According to geochemical (trace and rare earth elements), stable (δ¹⁸O, δ²H, δ³⁴S, and δ¹³C), and radiogenic (⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd) isotope data, the hydrothermal fluid responsible for the alteration and mineralization is related to the Kesikköprü granitoid, from which a significant magmatic component originates initially, followed by meteoric fluids at lower temperatures (123 °C) during the late-stage formation of calcite–quartz veins. Full article

The raspberry-red grossular, discovered in the Sierra de Cruces in Coahuila, Mexico, is characterized by its zoned coloration, featuring a pink rim and a black mantle with a sharp color transition at the border. However, there is a notable lack of definitive and systematic identification characteristics pertaining to its special zones. The mineral chemical composition and chromogenic mechanism remain unsupported by empirical validation derived from specific experimental data. In this study, the gemological properties, chemical composition, and spectral characteristics are systematically analyzed to explore the chromogenic mechanism and formation of zonal genesis. The results of the X-ray diffraction pattern, Raman spectrum, and major elements’ composition show that the raspberry-red grossular samples are grossular with high purity. Mn ions are a direct coloring factor of the pink rim of the grossular samples, while Fe ions are chromogenic elements of the black mantle. The MnO content of the pink rim ranges from 0.15 wt% to 1.72 wt%. The FeO content of the black mantle ranges from 3.11 wt% to 5.09 wt%, which is generally higher than that of other parts. The trace element compositions reveal that the rim and core of samples were formed in an oxidative environment (δEu = 0.43–2.41), which could be derived from the hydrothermal metasomatic skarn (δ¹⁸O = 11.03–12.14); the mantles of samples were formed in a reducing environment (δEu = 0.42–0.85), which is consistent with the magmatic skarn (δ¹⁸O = 11.40–11.66). They also show that the surrounding rocks provide part of the compositional sources for the raspberry-red grossular and interact with the black mantle, which affects the formation of the pink rim. This study offers geological and mineral compositional insights, addressing a significant void in the study of raspberry-red grossular, and lays the foundation for follow-up investigations. Full article

Oxygen-bearing platinum group minerals (O-bearing PGMs) are intergrown with base metal sulfides (BMS, e.g., pentlandite–[NiFe]₉S₈) within fractures in chromite grains from chromitite bodies on Ouen Island, New Caledonia. These PGMs are hosted in chlorite and serpentine, which formed during serpentinization of olivine and pyroxene. The O-bearing PGM grains are polygonal, show microfracturing (indicating volume loss), and contain Pt-Pd-rich sulfide remnants, suggesting pseudomorphic replacement of primary (magmatic) sulfides. They display chemical zonation, with Pt(-Pd-Ni-Fe) relict sulfide cores replaced by Pt-Fe-Ni oxidized alloy mantles and Pt-Cu-Fe(-Pd) alloy rims (tulameenite), indicating desulfurization. The core and mantle show a nanoporous structure, interpreted as the result of coupled dissolution–reprecipitation reactions between magmatic sulfides and low fO₂–fS₂ serpentinite-related fluids, probably formed during olivine transformation to serpentine + magnetite (early stages of serpentinization). This fluid infiltrated magmatic sulfides (PGE-rich and BMS), degrading them to secondary products and releasing S and metals that were accommodated in the mantle and rim of O-bearing PGMs. Upon olivine exhaustion, an increase in fO₂ might have stabilized Pt-Fe-O compounds (likely Pt⁰/Pt-Fe + Fe oxyhydroxides) alongside Ni-Fe alloys. Our results show that post-magmatic desulfurization of primary sulfides produces complex nano-scale intergrowths, mainly driven by changes in the fluid’s physicochemical properties during serpentinization. Full article

Polymethyl methacrylate (PMMA) bone cement has been a transformative material in orthopedics since its introduction in the mid-20th century. Originally used in dental medicine, PMMA was adopted for orthopedic applications by Sir John Charnley in the 1950s, significantly enhancing joint replacement surgeries. The primary appeal of PMMA lies in its biocompatibility, mechanical strength, and ease of handling, making it a favored choice for various orthopedic procedures, including arthroplasties and limb-salvage surgeries. However, the exothermic polymerization process of PMMA poses a risk of thermal necrosis in the surrounding bone tissue, as local temperatures can exceed 70 °C, causing damage to osteocytes. Research has sought to mitigate these risks by optimizing mixing techniques, reducing cement mantle thickness, and incorporating cooling methods. Recent advancements, such as the use of phase-change materials (PCMs) and alternative monomers, have shown promise in lowering the exothermic peak during polymerization. Other strategies include pre-cooling the cement and prosthetic components and using composite cement. Despite these innovations, managing the balance between minimizing heat generation and maintaining mechanical properties remains a challenge. The impact of thermal necrosis is significant, compromising implant stability and osseointegration. Understanding the complex interactions between PMMA’s thermal properties and its clinical outcomes is essential for improving orthopedic surgical practices and patient recovery. Full article

Olivine in deep-seated ultramafic xenoliths beneath the North China Block serves as a crucial proxy for decoding the compositions, properties, and evolution of the lithospheric mantle. Here, we conduct an investigation on olivine (including gem-grade) hosted in ultramafic xenoliths from Damaping basalt in the northern part of the North China Block. This contribution presents the results from petrographic, Raman spectroscopic, and major and trace elemental studies of olivine, with the aim of characterising the formation environment and genetic type of the olivine. The analysed olivine samples are characterised by high Mg# values (close to 91%) possessing refractory to fertile features and doublet bands with unit Raman spectra beams of 822 and 853 cm⁻¹, which are indicative of a forsterite signature. Major and trace geochemistry of olivine indicates the presence of mantle xenolith olivine. All the analytical olivine assays ≤0.1 wt % CaO, ~40 wt % SiO₂, and ≤0.05 wt % Al₂O₃. Furthermore, olivine displays significantly different concentrations of Ti, Y, Sc, V, Co, and Ni. The Ni/Co values in olivine range from 21.21 to 22.98, indicating that the crystallisation differentiation of basic magma relates to oceanic crust recycling. The V/Sc values in mantle/xenolith olivine vary from 0.54 to 2.64, indicating a more oxidised state of the mantle. Rare earth element (REE) patterns show that the LREEs and HREEs of olivine host obviously differentiated characteristics. The HREE enrichments of olivine and the LREE depletion of clinopyroxene further assert that the mantle in the Damaping area underwent partial melting. The wide variations of Mg# values in olivine and the Cr# values in clinopyroxene, along with major element geochemistry indicate transitional characteristics of different peridotite xenoliths. This is possibly indicative of a newly accreted lithospheric mantle interaction with an old lithospheric mantle at the time of the basaltic eruption during the Paleozoic to Cenozoic. Full article

Serpentine (Mg₃Si₂O₅(OH)₄), like quartz, dolomite and magnesite minerals, is a versatile mineral group characterized by silica and magnesium silicate contents with multiple polymorphic phases. Among the phases composed of antigorite, lizardite, and chrysotile, lizardite and chrysotile are the most prevalent phases in the serpentinites studied here. The formation process of serpentinites, which arise from the hydrothermal alteration of peridotites, influences the ratio of light rare earth elements (LREE) to heavy rare earth elements (HREE). In serpentinites, the ratio of light rare earth elements (LREE)/heavy rare earth elements (HREE) provides insights into formation conditions, geochemical evolution, and magmatic processes. The depletion of REE compositions in serpentinites indicates high melting extraction for fore-arc/mantle wedge serpentinites. The studied serpentinites show a depletion in REE concentrations compared to chondrite values, with HREE exhibiting a lesser degree of depletion compared to LREE. The high ΣLREE/ΣHREE ratios of the samples are between 0.16 and 4 ppm. While Ce shows a strong negative anomaly (0.1–12), Eu shows a weak positive anomaly (0.1–0.3). This indicates that fluid interacts significantly with rock during serpentinization, and highly incompatible elements (HIEs) gradually become involved in the serpentinization process. While high REE concentrations indicate mantle wedge serpentinites, REE levels are lower in mid-ocean ridge serpentinites. The enrichment of LREE in the analyzed samples reflects melt/rock interaction with depleted mantle and is consistent with rock–water interaction during serpentinization. The gradual increase in highly incompatible elements (HIEs) suggests that they result from fluid integration into the system and a subduction process. The large differential thermal analysis (DTA) peak at 810–830 °C is an important sign of dehydration, transformation reactions and thermal decomposition, and is compatible with H₂O phyllosilicates in the mineral structure losing water at this temperature. In SEM images, chrysotile, which has a fibrous structure, and lizardite, which has a flat appearance, transform into talc as a result of dehydration with increasing temperature. Therefore, the sudden temperature drop observed in DTA graphs is an indicator of crystal form transformation and CO₂ loss. In this study, the mineralogical and structural properties and the formation of serpentinites were examined for the first time using thermo-gravimetric analysis methods. In addition, the mineralogical and physical properties of serpentinites can be recommended for industrial use as additives in polymers or in the adsorption of organic pollutants. As a result, the high refractory nature of examined serpentine suggests that it is well-suited for applications involving high temperatures. This includes industries such as metallurgy and steel production, glass manufacturing, ceramic production, and the chemical industry. Full article

Early Jurassic mafic–ultramafic igneous rocks are sporadically exposed in the eastern part of northeastern China. Understanding their petrogenesis and geological implications is essential for elucidating the evolution of magma in subduction zones and the evolutionary history of the Paleo-Pacific Ocean. This study presents a detailed petrological, zircon U-Pb geochronological, and whole-rock geochemical analysis of the Jurassic hornblende gabbro in the Yanbian area of northeastern China. The emplacement age of the hornblende gabbro is constrained to 175.3 ± 1.6 Ma. All samples exhibit low SiO₂ content, metaluminous properties, and geochemical characteristics indicative of a subduction environment. By integrating trace elemental ratios, such as Th/Sm, Th/Ce, Ba/La, Rb/Nb, Hf/Sm, Ba/Nb, and ε_Nd(t), our data propose that the hornblende gabbro originated from a mixture of depleted mantle and approximately 10%–20% continental sediment, and that the magmatism is generated by processes involving metasomatic addition to the source mantle wedge by ‘supercritical’ fluids. Contrasting with several recent hypotheses, the magma of the Early Jurassic gabbro originated from the mantle wedge, incorporating contributions from sediment melts and ‘supercritical’ fluids, and formed during the westward subduction of the Paleo-Pacific Ocean. The Yanbian area in Jilin Province was primarily influenced by this westward subduction during the Early Jurassic. Full article

The present research’s main objective was to apply thorough exploration approaches that combine remote sensing data with geochemical sampling and analysis to predict and identify potential chromitite locations in a complex geological site, particularly in rugged mountainous terrain, and differentiate the ultramafic massif containing chromitite orebodies from other lithologies. The ultramafic massif forming the mantle section of the Kırdağ ophiolite, located within the Erzurum–Kars Ophiolite Zone and emerging in the east of Oltu district (Erzurum, NE Turkey), was selected as the study area. Optimum index factor (OIF), false-color composite (FCC), decorrelation stretch (DS), band rationing (BR), minimum noise fraction (MNF), and principal and independent component analyses (PCA-ICA) were performed to differentiate the lithological features and identify the chromitite host formations. The petrography, mineral chemistry, and whole-rock geochemical properties of the harzburgites, which are the host rocks of chromitites in the research area, were evaluated to verify and confirm the remote sensing results. In addition, detailed petrographic properties of the pyroxenite and chromitite samples are presented. The results support the existence of potential chromitite formations in the mantle section of the Kırdağ ophiolite. Our remote sensing results also demonstrate the successful detection of the spectral anomalies of this ultramafic massif. The mineral and whole-rock geochemical features provide clear evidence of petrological processes, such as partial melting and melt–peridotite interactions during the harzburgite formation. The chromian spinels’ Cr#, Mg#, Fe³⁺, Al₂O₃, and TiO₂ concentrations indicate that the harzburgite formed in a fore-arc environment. The Al₂O₃ content and Mg# of the pyroxenes and the whole-rock Al₂O₃/MgO ratio and V contents of the harzburgite are also compatible with these processes. Consequently, the combined approaches demonstrated clear advantages over conventional chromitite exploration techniques, decreasing the overall costs and supporting the occurrence of chromite production at the site. Full article

Wide varieties of igneous rocks are extensively utilized as stones for decoration purposes and as a potential source for building. With the use of petrological (mineralogical and chemical) and physico-mechanical analyses, the current work accurately mapped the Dokhan Volcanics (DV) and utilized them as decorative stones and their prospective in building materials using Frattini’s test. Field observations indicate that metavolcanics, DV, and monzogranites are the principal rock units exposed in the studied area. The DV rocks are characterized by a dense series of stratified, rhyolitic to andesitic lava interspersed with a few pyroclastics. Andesite, andesite porphyry, dacite, and rhyolite are the primary representatives of the selected DV. The lack of infrequent appearance of mafic units in the current volcanic eruptions indicates that the primary magma is not mantle-derived. This is supported by their Mg# (17.86–33.57). Additionally, the examined DV rocks have Y/Nb ratios above 1.2, suggesting a crustal source. The role of fractionation is interpreted by their variation from andesite passing through dacite to rhyolite, which is indicated by gradual negative distribution groups between silica and TiO₂, Fe₂O₃, CaO, MgO, Co, and Cu from andesite to rhyolitic lava. Additionally, a wide range of widely used DV rocks like Y/Nb, Rb/Zr, and Ba/Nb point to crustal contamination in the rhyolitic rocks. The partial melting of the lower crust can produce andesitic magma, which ascend to higher crustal levels and form lava of calc-alkaline. A portion of this lava may split, settle at shallow crustal depths, and undergo differentiation to create the DV rocks. Based on the results of physico-mechanical properties, the studied samples met the requirements for natural stone to be used as decorative stones, whether as interior or exterior installations. The pozzolanic assessment of the studied rocks revealed their usability as supplementary cementitious materials in the building sector. Full article

The Qinzhou fold belt, situated at the contact zone between the Yangtze and Cathaysia blocks in South China, was affected by the 1936 Lingshan M6¾ earthquake and the 1958 Lingshan M5¾ earthquake, both of which occurred within the conjugate structure. Understanding the deep seismogenic setting and causal mechanism of the Lingshan conjugate earthquake is of great significance for assessing the seismic disaster risk in the region. In this study, we utilized 237 magnetotelluric datasets and employed three-dimensional electromagnetic inversion to characterize the deep-seated three-dimensional resistivity structure of the Qinzhou fold belt and the Lingshan seismic zone. The results reveal that: (1) The NE-trending faults within the Qinzhou fold belt and adjacent areas are classified as trans-crustal faults. The faults exhibit crust-mantle ductile shear zones in their deeper sections, which are essential in governing regional tectonic deformation and seismic activity; (2) The electrical structure of the Qinzhou fold belt is in line with the tectonic characteristics of a composite orogenic belt, having experienced several phases of tectonic modification. The southeastern region is being influenced by mantle-derived magmatic activities originating from the Leiqiong area over a significant distance; (3) In the Lingshan seismic zone, the NE-trending Fangcheng-Lingshan fault is a trans-crustal fault and the NW-trending Zhaixu fault is an intra-crustal fault. The electrical structure pattern “two low, one high” in the zone has a significant impact on the deep tectonic framework of the area and influences the deformation behavior of shallow faults; and (4) The seismogenic structure of the 1936 Lingshan M6¾ earthquake was the Fangcheng-Lingshan fault. The earthquake’s genesis was influenced by the coupling effect of tectonic stress and deep thermal dynamics. The seismogenic structure of the 1958 Lingshan M5¾ earthquake was the Zhaixu fault. The earthquake’s genesis was influenced by tectonic stress and static stress triggering from the 1936 Lingshan M6¾ earthquake. The conjugate rupture mode in the Lingshan seismic zone is influenced by various factors, including differences in physical properties, rheology of deep materials, and the scale and depth of fault development. Full article

The thermodynamic properties of MgSiO₃ akimotoite at high temperatures and high pressures are important for investigating the phase equilibria of the Earth’s transition zone and the upper part of the lower mantle. In this paper, we present the self-consistent unit-cell volume, elastic properties, and in particular, thermodynamic properties including thermal expansion, heat capacity, entropy, and Grüneisen parameter of MgSiO₃ akimotoite at pressures up to 30 GPa and temperatures to 2000 K using an iterative numerical method and available experimental data, which are consistent with the previous studies. The results show that the determined thermal expansion, heat capacity, entropy, and Grüneisen parameter exhibit a nonlinear and negative relationship with increasing pressure. Additionally, the pressure derivatives of these thermodynamic parameters along with the temperature are also presented. Full article

The physical properties of lunar regolith are crucial for exploration planning, hazard assessment, and characterizing scientific targets at global and polar scales. The dielectric constant, a key property, offers insights into lunar material distribution within the regolith and serves as a proxy for identifying volatile-rich regoliths. Miniature radio frequency (Mini-RF) on the Lunar Reconnaissance Orbiter (LRO) provides a potential tool for mapping the lunar regolith’s physical nature and assessing the lunar volatile repository. This study presents global and polar S-band Mini-RF dielectric signatures of the Moon, obtained through a novel deep learning inversion model applied to Mini-RF mosaics. We achieved good agreement between training and testing of the model, yielding a coefficient of determination (R² value) of 0.97 and a mean squared error of 0.27 for the dielectric constant. Significant variability in the dielectric constant is observed globally, with high-Ti mare basalts exhibiting lower values than low-Ti highland materials. However, discernibility between the South Pole–Aitken (SPA) basin and highlands is not evident. Despite similar dielectric constants on average, notable spatial variations exist within the south and north polar regions, influenced by crater ejecta, permanently shadowed regions, and crater floors. These dielectric differences are attributed to extensive mantling of lunar materials, impact cratering processes, and ilmenite content. Using the east- and west-looking polar mosaics, we estimated an uncertainty (standard deviation) of 1.01 in the real part and 0.03 in the imaginary part of the dielectric constant due to look direction. Additionally, modeling highlights radar backscatter sensitivity to incidence angle and dielectric constant at the Mini-RF wavelength. The dielectric constant maps provide a new and unique perspective of lunar terrains that could play an important role in characterizing lunar resources in future targeted human and robotic exploration of the Moon. Full article

The Mengshan granitoid complex is located in the central part of Jiangnan Orogen and belongs to the western part of Jiangxi Province, where several phases of granitic magmatism record the crustal evolution of the late-Indosinian. However, its petrogenesis remains uncertain, largely due to controversies over its origin, evolutionary process and tectonic setting during intrusion. In this study, the lithological features and contact relationships observed in the systematic field geological investigations indicate that the late magmatic phases of the Mengshan granitoid complex are mainly composed of medium–fine-grained biotite monzogranite and fine-grained monzogranite, both of which developed primary fine-grained muscovite. Petrological, petrographic, geochemical and zircon U-Pb-Hf isotopic studies were further carried out on these rocks. Zircon U-Pb isotopic analyses suggest that the medium–fine-grained biotite monzogranite mainly formed at 220.7 ± 1.0 Ma to 218.0 ± 0.8 Ma, and that the fine-grained monzogranite formed at 211.5 ± 2.9 Ma to 212.9 ± 1.0 Ma. Whole-rock geochemical analysis results suggest that these rocks are rich in Cs, Rb, and U, and deficient in Ba, Sr, and Ti, and that they have properties characteristic of rocks with high silica, low P content and high K calc-alkali. Mineralogical and geochemical analysis results suggest that they are S-type granites. The ε_Hf(t) values of the early-stage medium–fine-grained biotite monzogranite and late-stage fine-grained monzogranite range from –4.7 to 0.3 and from –3.2 to 0.7, respectively. Geochemical and isotopic data suggest that these granitoids were derived from the partial melting of Proterozoic continent basement rocks, and that minor mantle materials were involved during their generation. The presence of the early Mesozoic Mengshan granitoid complex reflects a reduplicated far-field converge effect of the collision of the North China and South China blocks and the subduction of the Palaeo-Pacific plate into the South China block. The thickening of the Earth’s crust facilitated crustal delamination, underplating of mantle-derived magma, and crustal heating, triggering intense partial melting of the lithosphere and magma enrichment. Full article