Search Results (276)

The Qiubudong silver deposit on the western margin of the Fuping ore cluster in the central North China Craton is a representative breccia-type deposit characterized by relatively high-grade ores, thick mineralized zones, and extensive alteration, indicating considerable potential for economic resource development and further exploration. Previous studies on this deposit have not addressed its genetic mineralogical characteristics. This study focuses on pyrite and quartz to investigate their typomorphic features, such as crystal morphology, trace element composition, thermoelectric properties, and luminescence characteristics, and their implications for ore-forming processes. Pyrite crystals are predominantly cubic in early stages, while pentagonal dodecahedral and cubic–dodecahedral combinations peak during the main mineralization stage. The pyrite is sulfur-deficient and iron-rich, enriched in Au, and relatively high in Ag, Cu, Pb, and Bi contents during the main ore-forming stage. Rare earth element (REE) concentrations are low, with weak LREE-HREE fractionation and a strong negative Eu anomaly. The thermoelectric coefficient of pyrite ranges from −328.9 to +335.6 μV/°C, with a mean of +197.63 μV/°C; P-type conduction dominates, with an occurrence rate of 58%–100% and an average of 88.78%. A weak–low temperature and a strong–high temperature peak characterize quartz thermoluminescence during the main mineralization stage. Fluid inclusions in quartz include liquid-rich, vapor-rich, and two-phase types, with salinities ranging from 10.11% to 12.62% NaCl equiv. (average 11.16%) and densities from 0.91 to 0.95 g/cm³ (average 0.90 g/cm³). The ore-forming fluids are interpreted as F-rich, low-salinity, low-density hydrothermal fluids of volcanic origin at medium–low temperatures. The abundance of pentagonal dodecahedral pyrite, low Co/Ni ratios, high Cu contents, and complex quartz thermoluminescence signatures are key mineralogical indicators for deep prospecting. Combined with thermoelectric data and morphological analysis, the depth interval around 800 m between drill holes ZK3204 and ZK3201 has high mineralization potential. This study fills a research gap on the genetic mineralogy of the Qiubudong deposit and provides a scientific basis for deep exploration. Full article

In this study, the neutron and gamma radiation-shielding properties of serpentinites from the Guleman ophiolite complex were investigated, and results were evaluated in comparison with rare earth element (REE) content. The linear and mass attenuation coefficients (LAC and MAC), half-value layer (HVL), mean free path (MFP), and effective atomic numbers (Z_eff) of serpentinite samples were experimentally measured in the energy range of 80.99–383.85 keV. Theoretical MAC values were calculated. Additionally, fast neutron removal cross-sections, as well as thermal and fast neutron macroscopic cross-sections, were theoretically determined. The absorbed equivalent dose rates of serpentinite samples were also measured. The radiation protection efficiency (RPE) for gamma rays and neutrons were determined. It was observed that the presence of rare earth elements within serpentinite structure has a significant impact on thermal neutron cross-sections, while crystalline water content (LOI) plays an influential role in fast neutron cross-sections. Moreover, it has been observed that the concentration of gadolinium exerts a more substantial influence on the macroscopic cross-sections of thermal neutrons than on those of fast neutrons. The research results reveal the mineralogical, geochemical, morphological and radiation-shielding properties of serpentinite rocks contribute significantly to new visions for the use of this naturally occurring rock as a geological repository for nuclear waste or as a wall-covering material in radiotherapy centers and nuclear facilities instead of concrete. Full article

This study explores the feasibility of utilizing granite sawing sludge (FC) as a precursor to produce alkali-activated materials (AAMs). To enhance the reactivity of the system, metakaolin (MK) was added and binary mixtures were synthetized. A multidisciplinary approach, including mineralogical, chemical and mechanical analysis, was employed to assess the suitability of these precursors to produce AAMs. X-Ray diffraction (XRD) and Fourier-Transform Infrared spectroscopy (FT-IR) confirmed the occurred activation reaction with the consequent increase in the amorphous content. Raman spectroscopy was used to further explore the mineralogical composition of the consolidated specimens, helping in the detection of salts, whose formation is ascribed to secondary carbonatation processes. Morphological analysis (SEM-EDS) displayed relatively uniform microstructures for all specimens. Compressive strength tests revealed that MK rich samples achieved best values compared to FC rich formulations, which exhibited reduced strength resistance. This study highlights, for the first time, the benefits of incorporating Cuasso al Monte granite sawing sludges into alkali-activated binders. Results suggested that the incorporation of FC is recommended for both environmental and economic advantages. Full article

This study investigates the spatial distribution of transition metals—iron (Fe), titanium (Ti), and chromium (Cr)—within the Dryden crater on the Moon using hyperspectral data from the Moon Mineralogy Mapper (M³). By applying spectral parameters and false color composite techniques, geospatial maps of chromite distribution and FeO, TiO₂ wt.% distribution were generated at a resolution of ~140 m. The findings reveal distinct elemental enrichments along geomorphologically active regions such as crater walls, terraces, and central peaks, highlighting impact-driven material differentiation, the influence of morphology, degradation, and space weathering. These results enhance our understanding of lunar crustal evolution and support future exploration and resource utilization efforts. Full article

Amid increasing interest in enhanced oil recovery and carbon geological sequestration programs, improved static reservoir lithofacies models are emerging as a requirement for well-guided project management. Building reservoir models can leverage seismic attribute clustering for seismic facies mapping. One challenge is that machine learning (ML) seismic facies mapping is prone to a wide range of equally possible outcomes when traditional unsupervised ML classification is used. There is a need to constrain ML seismic facies outcomes to limit the predicted seismic facies to those that meet the requirements of geological plausibility for a given depositional setting. To this end, this study utilizes an unsupervised comparative hierarchical and K-means ML classification of the whole 3D seismic data spectrum and a suite of spectral bands to overcome the cluster “facies” number uncertainty in ML data partition algorithms. This comparative ML, which was leveraged with seismic resolution data preconditioning, predicted geologically plausible seismic facies, i.e., seismic facies with spatial continuity, consistent morphology across seismic bands, and two ML algorithms. Furthermore, the variation of seismic facies classes was validated against observed lithofacies at well locations for the Mississippian carbonates of Kansas. The study provides a benchmark for both unsupervised ML seismic facies clustering and an understanding of seismic facies implications for reservoir/saline-aquifer aspects in building reliable static reservoir models. Three-dimensional seismic reflection P-wave data and a suite of well logs and drilling reports constitute the data for predicting seismic facies based on seismic attribute input to hierarchical analysis and K-means clustering models. The results of seismic facies, six facies clusters, are analyzed in integration with the target-interval mineralogy and reservoir porosity. The study unravels the nature of the seismic (litho) facies interplay with porosity and sheds light on interpreting unsupervised machine learning facies in tandem with both reservoir porosity and estimated (Umaa-RHOmaa) mineralogy. Full article

The complexity of the pore system hindered our understanding of the storage and transport properties of organic-rich shales, which in turn brought challenges to the efficient exploration and development of shale oil and gas. This study, based on elemental, mineralogical, petrographic, and petrophysical approaches, attempts to reveal the pore structure and fractal characteristics of a suite of Permian shales collected from the northeastern Sichuan Basin, China. The results showed that meso-pores make up the main proportion of the total pore volume in the Permian shale in this study; most of the pore size distribution patterns for micro pores and meso-macropores are bimodal. Pores related to clay minerals, organic matter pores, and intragranular dissolution pores are the main storage spaces in these shales. In these samples, ink-bottle pores dominate, with some slit and wedge-shaped ones developed. The morphology of the pores in the studied shales is mainly ink-bottle pores, with some slit-shaped and wedge-shaped pores. The fractal dimension D₂ is greater than D₁, indicating that the homogeneity of pore space is stronger than that of the specific surface area. Quartz in Permian shales inhibits the development of macro- and mesopore spaces and enhances pore heterogeneity, while clay minerals facilitate the development of macro- and mesopore spaces and attenuate pore heterogeneity. The organic matter content shows a negative impact on the macropore volume due to the stripped occurrence and matrix filling. This study has a vital significance for current exploration and development of shale gas in Permian strata in the Sichuan Basin and offers insights for Permian shales in other basins all over the world. Full article

Investigating the microstructural damage and mechanical properties of coal under deep mine hygrothermal conditions is essential for ensuring the safe and efficient extraction of coal resources. In this study, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and nanoindentation techniques were employed to examine the surface morphology and microscale mechanical properties of coal samples exposed to four environmental conditions, initial, humidified, heated, and coupled hygrothermal, under a peak indentation load of 70 mN. The results indicate that humidification led to the formation of dissolution pores and localized surface softening, resulting in a 15.9% increase in the peak indentation depth and reductions in the hardness and elastic modulus by 29.53% and 17.14%, respectively. Heating caused localized disintegration and the collapse of the coal surface, accompanied by surface hardening, with a slight 0.4% decrease in the peak indentation depth and increases in hardness and the elastic modulus by 1.32% and 1.56%, respectively. Under the coupled hygrothermal condition, numerous fine dissolution pores and microcracks developed on the coal surface, and the mechanical properties exhibited intermediate values between those observed in the humidified and heated states. Notably, the elevated temperature suppressed the moisture penetration into the coal matrix to some extent in the hygrothermal environment. A positive correlation was found between the hardness and elastic modulus, independent of the coal sample condition. The mineralogical composition significantly influenced the microscale mechanical behavior, with hard quartz minerals corresponding to lower peak indentation depths and a higher hardness, whereas soft kaolinite showed the opposite trend. Full article

This study explores the potential of using sustainable materials in brick manufacturing by designing a novel brick mix in the laboratory, incorporating sand, lime kiln dust (LKD) waste, tyre rubber, and ground granulated blast furnace slag (GGBFS) waste. These cementless bricks blended LKD–GGBFS wastes as the binder agent and fine crumb rubber from waste tyres as a partial replacement for sand in measured increments of 0%, 5%, and 10% by volume of sand. Ordinary Portland cement (OPC) and fired clay bricks were sourced from the industry, and their properties were compared to those of the laboratory bricks. Tests performed on the industry and laboratory bricks included compressive strength (CS), freeze-thaw (F-T), and water absorption (WA) tests for comparison purposes. Additionally, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed on the bricks to assess the morphological and mineralogical changes responsible for the observed strengths and durability. The CS and WA values of the engineered bricks were 12, 6, and 4 MPa, and 7, 12, and 15%, respectively, for 0, 5, and 10% crumb rubber replacements. The industry bricks’ average CS and WA values were 13 MPa and 8%, respectively. From the results obtained, the green laboratory bricks passed the minimum strength requirements for load-bearing and non-load-bearing bricks, which can be used to construct small houses. Lastly, the engineered bricks demonstrated strength and durability properties comparable to those of the industry-standard bricks, indicating their potential as a sustainable alternative to help divert waste from landfills, reduce the pressure on natural fine sand extraction, and support eco-conscious brick production for a sustainable environment. Full article

Tubular fossils are a unique metazoan group emerging in the late Ediacaran Period and demonstrating early skeletogenesis and an increase in the diversity of early biocommunities. Among the known records, Sinotubulites is widely distributed and distinct in morphology and ultrastructure, holding important evolutionary and stratigraphic significance comparable to the well-known Cloudina. However, its biological affinity remains unclear until now. Among various reasons, taphonomic bias is one of the major factors responsible for this, as it not only altered the primary morphology but also modified the ultrastructure and composition of the fossil. Thus, a further study on its taphonomic process would help to decode the biological affinity of Sinotubulites. For this purpose, we conducted a taphonomic study on Sinotubulites from the top of the Shibantan Member of the Dengying Formation at the Zhongling section in the Yangtze Gorges area (Hubei Province, China). We applied electron backscatter diffraction (EBSD) and cathodoluminescence (CL) to reveal its mineralogical features. EBSD and CL analyses demonstrate that both the fossils and matrix are composed of unoriented calcite, and the matrix shows slight dolomitization with sporadic dolomite grains. The calcite crystals within the Sinotubulites tubes are significantly larger than those in the matrix, indicating that the tubular structure provided sufficient space for crystal growth. The absence of lamellar structures in the tubular walls further suggests that the original biogenic material may have been dissolved during diagenetic calcification. The absence of dolomitization in the fossils indicates that this process may have been inhibited by either their large calcite crystals or the enclosed space confined by the outer shell. The identical non-luminescent features of the matrix and fossils suggest that their calcification likely occurred during the same stage. This study demonstrates that taphonomic biases must be accounted for when analyzing the original structure and composition. Additionally, this research documents the occurrence of Sinotubulites in the Shibantan Member, representing its lowest stratigraphic horizon in the Yangtze Block. Full article

We studied the chemical composition and morphostructural features of micron and submicron-sized particles of native gold in apocarbonate tremolite–diopside skarns of the Ryabinovoye deposit located on the southeastern margin of the Aldan Shield (Far East, Russia). Polished sections of lump ore samples containing native gold were analyzed by scanning electron microscopy in combination with X-ray microanalysis using different modes of visualization and X-ray diffraction methods. Gold particles, clearly visible after etching the surface of some polished sections with acids and partial or complete dissolution of some host minerals, were also examined. Native gold from the studied deposit is of high fineness (above 970‰) and contains (in wt.%) <1.59 Ag and less commonly <0.37 Cu and <0.15 Zn. Native gold is found intergrown with tremolite, diopside, and other magnesian silicates, as well as calcite, fluorite, magnetite, and sphalerite. Rare microinclusions of pyrrhotite, galena, and clinohumite are present in gold grains. It was found that native gold inherits the morphology of tremolite crystals and aggregates, which is determined by the size and shape of the voids bounded by its crystals. Gold localized in the intercrystalline spaces and in the zones of conjugation with remobilized calcite has irregular, lumpy shapes and partially or completely faceted grains with a dense structure. The nature of the localization and distribution of native gold in ores is due to the crystallization of the tremolite component of skarns. Apparently, the processes of gold accumulation are caused by the thermal activation of solid-phase differentiation of the substance of carbonate rocks, in which the processes of destruction of the original minerals and collective recrystallization play a significant role. It is likely that at some gold skarn deposits, carbonate rocks could be the source of gold. Data on the morphology and sizes of native gold segregations, as well as on the intergrown minerals, can be used to improve gold extraction technologies. A specific group of minerals intergrown with native gold in gold skarn deposits can be used as a diagnostic feature in the primary search for placer gold. The obtained results will help to better understand the formation of native gold in apocarbonate tremolite–diopside skarns. Full article

The growing demand for lightweight aggregates (LWAs) in the construction industry is driving the development of sustainable alternatives based on the reuse of solid industrial waste. The aim of this study was to assess the technical feasibility of using red ceramic waste (RCW) as a partial or total substitute for red clay (RC) to produce lightweight expandable aggregates. Six formulations were made with different proportions of RCW and RC and sintered at four temperatures (1100, 1150, 1200 and 1250 °C). They were characterised using physical, thermal, morphological, chemical and mechanical analyses, according to standard protocols. The results showed that almost all the formulations sintered at 1200 and 1250 °C had a positive bloating index (BI > 0), particle density of less than 2.0 g/cm³, low water absorption of less than 2% and mechanical strength of more than 5.4 MPa, revealing strong potential for use in lightweight structural and non-structural concrete. The main conclusion is that RCW, even used in isolation, has physicochemical and mineralogical properties suitable for the production of lightweight aggregates under optimised thermal conditions, contributing to the development of sustainable materials with a competitive technical performance compared to commercial LWAs. Full article

The pursuit of effective climate change mitigation strategies is driving research into geological carbon dioxide (CO₂) storage. The present work explores the interaction of CO₂ with carbonate rocks from the El Abra formation in the Tampico-Misantla basin, focusing on the comparative influence of organic matter (OM) content on mineralization processes, hypothesizing that variations in OM content significantly modulate the mineralization process affecting both the rate and type of carbonate formation. Expanding on a previous study, CO₂ is studied and injected under high-pressure (1350-2350 PSI) and high-temperature (60–110 °C) conditions into two contrasting samples: one with high OM content and another with low OM content. Structural, morphological, and physical adsorption changes were evaluated through Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analyses. The findings indicate that the mineralogy of El Abra promotes secondary carbonate precipitation, with rock–fluid interactions significantly enhanced by brine presence. Samples with high OM exhibited a dramatic reduction in average particle size from 13 μm to 2 μm, along with the formation of metastable phases, such as vaterite—evidenced by XRD peak shifting and modifications in the FT-IR spectrum of carbonate bands. Meanwhile, low-OM samples showed an increase in particle size from 1.6 μm to between 3.26 and 4.12 μm, indicating predominant recrystallization. BET analysis confirmed a significant porosity enhancement in high-OM samples (up to 2.918 m²/g). Therefore, OM content plays a critical role in modulating both the rate and type of mineralization, potentially enhancing physical storage capacity in low-OM samples. These integrated findings demonstrate that OM critically governs calcite dissolution, secondary carbonate formation, and microstructural evolution, providing key insights for optimizing CO₂ storage in complex carbonate reservoirs. Full article

Marble waste is produced on a large scale in many countries, resulting in serious pollution problems. This investigation aimed to study the valorization potential of marble waste from the ornamental rock industry used in the synthesis of a novel calcium niobate–magnesium niobate composite powder prepared by a solid-state reaction between 1000 °C and 1200 °C. The chemical and mineralogical characteristics of the marble waste were determined. Structural and morphological characterizations of the synthesized calcium niobate–magnesium niobate composite powders were conducted by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The thermophysical properties were measured using open photoacoustic cell and photothermal techniques. Structurally, at all synthesis temperatures, the calcium niobate–magnesium niobate powders were found to be composed of a complex mixture of CaNb₂O₆/Ca₂Nb₂O₇/MgNb₂O₆/CaMg_0.33Nb_0.67O₃. In addition, the calcium niobate–magnesium niobate composite powders exhibited low values of thermal diffusivity (1.88–2.15 × 10⁻⁷ m²/s) and thermal conductivity (0.12–0.16 W/mK). The findings of this investigation highlight the potential of marble waste as a promising sustainable source of carbonate for obtaining calcium niobate–magnesium niobate composite powder, which has thermophysical properties that should be explored in low-thermal-conductivity applications. Full article

The valorization of agricultural and industrial solid by-products as secondary resources in the development of value-added materials can contribute to environmental health protection, particularly in the climate change era. Current advances in environmental legislation also encourage manufacturers to optimize waste management, upgrading and utilization towards resource conservation, energy efficiency and cost reduction in the context of a circular economy. In the present research, the elaboration of novel sustainable ceramics is investigated by sintering (at 800 °C for 2 or 6 h) of compacted mixtures composed of lignite fly ashes along with biomass ash (olive kernel ash) at different proportions. It appears that the chemical, mineralogical and morphological characteristics of these by-products promote their use as starting materials in ceramic engineering. Characterization and evaluation of the ceramics obtained via XRD and SEM-EDX analysis, as well as Vickers microhardness measurements, confirm the effectiveness of the consolidation process. In fact, the material derived from an 85% Class-C fly ash and 15% biomass ash compact, after 6 h sintering, exhibited greater results in terms of ceramic microstructure and microhardness (380 Hv), while a sintering time of 2 h was barely acceptable. The materials developed can be considered for use in various applications. Full article

In Korea, asbestos-containing waste (ACW) is disposed of in landfills. However, due to the limited landfill capacity and the potential health risks of asbestos contamination, alternative, safer disposal methods are needed. Heat treatment has been suggested as an alternative disposal method for ACW. Therefore, it is necessary to determine the optimal conditions for the thermal decomposition of chrysotile in ACW and reveal the mineralogical composition of heat-treated ACW. In this study, asbestos cement roof (ACR) and asbestos gypsum board (AGB) samples were heat-treated at 600, 700, 800, and 900 °C to identify the optimal heat treatment parameters to eliminate chrysotile fibers. The thermal, chemical, and mineralogical characteristics of the ACW were determined before and after heat treatment using multiple analytical methods. The ACR consisted of chrysotile, calcite, and ettringite, and the AGB consisted of chrysotile, gypsum, and calcite. After heat treatment at 900 °C, the ACR was mainly composed of cement component minerals and lime, while the AGB additionally contained anhydrite. SEM-EDS analysis confirmed the persistence of fibrous minerals in the ACW up to 800 °C. Furthermore, TEM-EDS analysis revealed hollow tubular morphology of chrysotile in the heat-treated ACR at up to 700 °C and in the heat-treated AGB at 600 °C. These results suggest that heat treatment at temperatures of at least 900 °C may be necessary for the complete thermal decomposition of chrysotile in ACW. Full article