Search Results (95)

Characterizing tight reservoirs is challenging due to the complex pore structure and strong heterogeneity at various scales. Current digital rock physics often struggles to reconcile high-resolution imaging with representative sample sizes, and 3D digital cores are frequently used primarily as visualization tools rather than predictive, computable platforms. Thus, a clear methodological gap persists: high-resolution models typically lack macroscopic geological features, while existing 3D digital models are seldom leveraged for quantitative, predictive analysis. This study, based on a full-diameter core sample of a single lithology (gray-black shale), aims to bridge this gap by developing an integrated workflow to construct a high-fidelity, computable 3D model that connects the micro–nano to the macroscopic scale. The core was scanned using high-resolution X-ray computed tomography (CT) at 0.4 μm resolution. The raw CT images were processed through a dedicated pipeline to mitigate artifacts and noise, followed by segmentation using Otsu’s algorithm and region-growing techniques in Avizo 9.0 to isolate minerals, pores, and the matrix. The segmented model was converted into an unstructured tetrahedral finite element mesh within ANSYS 2024 Workbench, with quality control (aspect ratio ≤ 3; skewness ≤ 0.4), enabling mechanical property assignment and simulation. The digital core model was rigorously validated against physical laboratory measurements, showing excellent agreement with relative errors below 5% for key properties, including porosity (4.52% vs. 4.615%), permeability (0.0186 mD vs. 0.0192 mD), and elastic modulus (38.2 GPa vs. 39.5 GPa). Pore network analysis quantified the poor connectivity of the tight reservoir, revealing an average coordination number of 2.8 and a pore throat radius distribution of 0.05–0.32 μm. The presented workflow successfully creates a quantitatively validated “digital twin” of a full-diameter core. It provides a tangible solution to the scale-representativeness trade-off and transitions digital core analysis from a visualization tool to a computable platform for predicting key reservoir properties, such as permeability and elastic modulus, through numerical simulation, offering a robust technical means for the accurate evaluation of tight reservoirs. Full article

This study presents an integrated geological and environmental radiological analysis of basaltic volcanic rocks, which have been characterized by their suitability and potential for risk when used as construction materials. A total of thirty-five representative basaltic samples from the environment of studied area, located in the Northern Eastern Desert of Egypt, were utilized for this study. The rocks were then analyzed by means of HPGe high-resolution gamma-ray spectrometry methods. The petrographic studies show that the basalt samples were composed mostly of three main minerals: plagioclase, olivine, and pyroxene. In addition, these rocks have a significant degree of secondary alteration products, including sericite, epidote, and zoethite. For uranium-238 (²³⁸U), thorium-232 (²³²Th), and potassium-40 (⁴⁰K), the average activity concentration measured 53 ± 20 Bq kg⁻¹, 54 ± 14 Bq kg⁻¹, and 1178 ± 269 Bq kg⁻¹, respectively. Using the current global reference limits, all the measured values are above acceptable levels for the radionuclides ²³⁸U, ²³²Th, and ⁴⁰K. The radiological indices calculated for each of the basalt volcanic samples measured radium equivalent activity (Ra_eq = 221 Bq kg⁻¹), external hazard index (H_ex = 0.60), internal hazard index (H_in = 0.74), gamma index (Iγ = 0.84), and annual effective dose (AED = 0.52 mSv y⁻¹) indicate that the radiological hazard values of these samples are acceptable, unlike several samples, where values are near or exceed the accepted standards for indoor hazards. The most significant finding of this study reveals that the major contributions in the environment from radiological risk can be attributed to radionuclides ²³⁸U and ⁴⁰K based on correlation analysis, hierarchical clustering, and PCA analyses, and this study establishes the first multivariate perspective of how radiogenic materials controlled by the environment can affect basaltic rocks. Therefore, this study creates an important baseline for future environmental monitoring and states that caution is warranted when using basalt as a finished material for constructed environments, and for using basaltic products as raw materials in indoor environments. Full article

Rock art in the Albarracín Cultural Park represents one of Spain’s most significant concentrations of post-Paleolithic paintings, yet comprehensive chemical characterization across multiple shelters remained lacking. This study analyzes 102 pigment samples (54 white, 31 black, 17 red) from 12 shelters using portable X-ray fluorescence spectroscopy. Centered log-ratio transformation addressed compositional data constraints, enabling multivariate analyses (PCA, LDA, MANOVA) that properly account for the constant-sum constraint inherent in geochemical data. Linear discriminant analysis achieved 92.6%–100% classification accuracy for site attribution, with barium emerging as the universal discriminating element across all pigment types (Cohen’s d = 4.91–9.19). Iron concentrations confirmed hematite/goethite use in red pigments, with inter-shelter variations suggesting different ochre sources. Black pigments revealed dual technologies: manganese oxides (pyrolusite) and carbon-based materials, with phosphorus enrichment in some samples consistent with possible bone-derived materials, though alternative phosphorus sources cannot be definitively excluded. This technological duality occurred within individual shelters, documenting greater complexity than previously recognized. White pigments combined substrate-derived materials with gypsum and aluminosilicate clay minerals (likely of the kaolinite group), occasionally incorporating phosphate-rich phases. The documented coexistence of compositionally distinct pigments within single shelters (whether from different raw material sources or varied preparation techniques) confirms the technical heterogeneity of Albarracín rock art and challenges assumptions about technological homogeneity in Levantine art production. This interplay between natural geological constraints and cultural technological choices underscores the need for complementary surface-sensitive techniques to fully resolve the technological repertoire of Levantine artists. Full article

The expansion of copper mining operations has led to the accumulation of a large amount of phyllite waste rock. Re-purposing this material into manufactured sand presents a promising solution for its large-scale consumption. In this study, phyllite waste rock from the Dexing Copper Mine was used as raw materials to prepare manufactured sand. A precise mineralogical analysis was conducted using Tescan Integrated Mineral Analyzer (TIMA) to determine the mineral composition, intergeneration and distribution relationships, particle size and shape, and elemental distribution. The performance of the resulting manufactured sand was comprehensively evaluated. Key findings showed a needle and flake particle content of 5.2%, a methylene blue (MB) value of 1.3, and a stone powder content of 9%. The physical properties, including solidity, crushing index, density, and porosity, as well as mica content, complied with the national standard GB14684-2022 (Sand for Construction). Additionally, phyllite-sand concrete exhibited a third-month expansion rate below the standard limit of 0.1%, indicating no potential risk for alkali-silica reaction. The radioactive index of the material met the standard requirements, posing no radiation hazard. However, the excessive sulfur compounds in phyllite present a risk of corrosion of the concrete structures, necessitating mitigation measures. Full article

High-purity quartz (HPQ) is a critical raw material for advanced technologies including semiconductors, photovoltaic cells, and optical fibers. This study reviews the geological occurrence, beneficiation routes, and strategic significance of HPQ within the European context. Quartz processing follows a sequential flowsheet of comminution, magnetic separation, flotation, acid leaching, and thermal treatment, designed to remove mineral impurities such as Fe, Al, Ti, and mica. The resulting ultra-high-purity quartz (UHPQ) achieves the chemical and physical specifications required for high-tech industries. Quartz, which is the most common mineral on Earth, can be found in a variety of geological locations such as granitic rocks and pegmatites in the Variscan Belt, metamorphic quartzites, hydrothermal veins, and Pleistocene periglacial and aeolian sediments. Case studies of European deposits demonstrate that geological origin directly influences processing requirements, and that tailored beneficiation strategies are essential to unlock viable resources. To our knowledge, this is the first Europe-focused synthesis that links these findings with the EU Critical Raw Materials Act, the work that emphasizes the potential for domestic HPQ development to strengthen European supply chain resilience, reduce dependence on imports, and support the transition to a green and digital economy. Full article

Phonolite is a fine-grained, shallow extrusive rock rich in alkali minerals and containing iron/titanium-bearing minerals. This rock is widely used as a construction material for building exteriors due to its excellent abrasion resistance and insulation properties. However, during the cutting process, approximately 70% of the rock is discarded as tailing. So, this study aims to repurpose tailings from a phonolite cutting and sizing plant into a high-alkali ceramic raw mineral concentrate. To enable the use of phonolite tailings in ceramic manufacturing, it is necessary to remove coloring iron/titanium-bearing minerals, which negatively affect the final product. To achieve this removal, dry/wet magnetic separation processes, along with flotation, were employed both individually and in combination. The results demonstrated that using dry high-intensity magnetic separation (DHIMS) resulted in a concentrate with an Fe₂O₃ + TiO₂ grade of 0.95% and a removal efficiency of 85%. The wet high-intensity magnetic separation (WHIMS) process reduced the Fe₂O₃ + TiO₂ grade of the concentrate to 1.2%, with 70% removal efficiency. During flotation tests, both pH levels and collector concentration impacted the efficiency and Fe₂O₃ + TiO₂ grade (%) of the concentrate. The lowest Fe₂O₃ + TiO₂ grade of 1.65% was achieved at a pH level of 10 with a collector concentration of 2000 g/t. Flotation concentrates processed with DHIMS achieved a minimum Fe₂O₃ + TiO₂ grade of 0.90%, while those processed with WHIMS exhibited higher Fe₂O₃ + TiO₂ grades (>1.1%) and higher recovery rates (80%). Additionally, studies on flotation applied to WHIMS concentrates showed that collector concentration, pulp density, and conditioning time significantly influenced the Fe₂O₃ + TiO₂ grade of the final concentrate. Full article

The Tuztaşı low-sulfidation epithermal Au–Ag deposit (Biga Peninsula, Türkiye) records a multi-stage hydrothermal history that can be interpreted through the trace and rare-earth-element (REE) chemistry of quartz. High-precision LA-ICP-MS analyses of five representative quartz samples (23 ablation spots; 10 analytically robust) reveal two fluid stages. Early fluids were cold, dilute meteoric waters (δ¹⁸O₍H₂O₎ ≈ −6.8 to +0.7‰), whereas later fluids circulated deeper, interacted with felsic basement rocks, and evolved in composition. Mineralized quartz displays marked enrichment in As (raw mean = 2854 ± 6821 ppm; filtered mean = 70 ± 93 ppm; one spot 16,775 ppm), K (498 ± 179 ppm), and Sb (57.8 ± 113 ppm), coupled with low Ti/Al (<0.005) and elevated Ge/Si (0.14–0.65 µmol mol⁻¹). Chondrite-normalized REE patterns show pronounced but variable LREE enrichment ((La/Yb)_n ≤ 45.3; ΣLREE/ΣHREE up to 10.8) and strongly positive Eu anomalies (δEu ≤ 9.3) with slightly negative Ce anomalies (δCe ≈ 0.29); negligible Ce–Eu covariance (r² ≈ 0.05) indicates discrete redox pulses. These signatures indicate chemically evolved, reducing fluids conducive to Au–Ag deposition. By contrast, barren quartz is characterized by lower pathfinder-element contents, less fractionated REE profiles, higher Ti/Al, and weaker Eu anomalies. A composite exploration toolkit emerges: As > 700 ppm, As/Sb > 25, Ti/Al < 0.005, Ge/Si > 0.15 µmol mol⁻¹, and δEu ≫ 1 reliably identify ore-bearing zones when integrated with δ¹⁸O data and fluid-inclusion microthermometry from earlier studies on the same vein system. This study provides one of the first systematic applications of integrated trace-element and REE analysis of quartz to a Turkish low-sulfidation epithermal system, offering an applicable model for vectoring mineralization in analogous settings worldwide. Full article

The Sanandaj–Sirjan Zone and Zagros Fold–Thrust Belt in Iran host numerous Mediterranean-type karst bauxite deposits; however, their formation mechanisms and critical raw material potential remain ambiguous. This study combines mineralogical and geochemical analyses to explore (1) the formation of authigenic minerals, (2) the role of microbial organic processes in Fe cycling, and (3) the assessment of their critical raw materials potential. Mineralogical analyses of the Late Cretaceous Daresard and Middle–Late Permian Yakshawa bauxites reveal distinct horizons reflecting their genetic conditions: Yakshawa exhibits a vertical weathering sequence (clay-rich base → ferruginous oolites → nodular massive bauxite → bleached cap), while Daresard shows karst-controlled profiles (breccia → oolitic-pisolitic ore → deferrified boehmite). Authigenic illite forms via isochemical reactions involving kaolinite and K-feldspar dissolution. Scanning electron microscopy evidence demonstrates illite replacing kaolinite with burial depth enhancing crystallinity. Diaspore forms through both gibbsite transformation and direct precipitation from aluminum-rich solutions under surface conditions in reducing microbial karst environments, typically associated with pyrite, anatase, and fluorocarbonates under neutral–weakly alkaline conditions. Redox-controlled Fe-Al fractionation governs bauxite horizon development: (1) microbial sulfate reduction facilitates Fe³⁺ → Fe²⁺ reduction under anoxic conditions, forming Fe-rich horizons, while (2) oxidative weathering (↑Eh, ↓moisture) promotes Al-hydroxide/clay enrichment in upper profiles, evidenced by progressive total organic carbon depletion (0.57 → 0.08%). This biotic–abiotic coupling ultimately generates stratified, high-grade bauxite. Finally, both the Yakshawa and Daresard karst bauxite ores are enriched in critical raw materials. It is worth noting that the overall enrichment appears to be mostly driven by the processes that led to the formation of the ores and not by the chemical features of the parent rocks. Divergent bauxitization pathways and early diagenetic processes—controlled by paleoclimatic fluctuations, redox shifts, and organic matter decay—govern critical raw material distributions, unlike typical Mediterranean-type deposits where parent rock composition dominates critical raw material partitioning. Full article

Concrete and mortar production consumes significant natural resources, leading to environmental concerns and sustainability challenges. Sustainable alternatives, such as industrial byproducts, have been explored to replace clinkers and aggregates. Basalt rock powder (BRP) is a promising option due to its physical and chemical properties, including its better particle size distribution and compatibility with cementitious composites, and studies have highlighted its pozzolanic activity and its potential to improve mechanical properties (compressive strength, flexural strength, and durability). Reusing rock dust as a raw material could transform it into a mineral byproduct, benefiting the new material and reducing waste volumes. This article presents a systematic literature review on the use of BRP in construction materials, conducted using the Scopus, ScienceDirect, PubMed, and Web of Science databases and following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) procedures. The search resulted in 787 articles (up to December 2024) and, after the screening process, 17 met the inclusion criteria. From the selected articles, information regarding the utilization of this waste product; its influence on mechanical properties, pozzolanic activity, and durability; and the sustainability associated with its use was compiled. The risk of bias was low as the search was comprehensive, all the papers were peer-reviewed, and all authors reviewed the papers independently. In conclusion, the studies demonstrate the potential of using BRP as a component of cementitious materials, indicating it as a possible innovative solution to the current challenges in the construction industry. Full article

The key objectives of both European Union and Portuguese policies are energy efficiency and carbon neutrality in the building sector. Timber construction offers unique advantages in achieving these goals, such as increased productivity through faster and more efficient building processes, using renewable resources with lower carbon emissions during production and throughout the lifecycle, and contributions to forest conservation. However, in many countries, timber construction remains underutilised due to concerns about its thermal and acoustic performance, fire safety, and limited availability of raw materials. This study addresses these challenges by evaluating the potential of various insulation materials, including polystyrenes, mineral wools, natural fibres, composites, and acoustic mats, for incorporation into prefabricated timber components. Key performance criteria included thermal insulation, sound absorption, fire reaction, environmental impact, and local availability. Among the materials analysed, glass wool, rock wool, and cork emerged as the most favourable options, offering excellent thermal and acoustic performance and presenting strong results in other key parameters. These findings underscore the potential of incorporating these materials into timber construction systems, contributing to developing sustainable and high-performance building solutions. Full article

Based on a review of the existing literature on the use of diatomite and the functioning of phase-change heat accumulators, in this study, we conducted empirical research on the creation of a phase-change composite based on Carpathian diatomite. As part of our mineralogical research, we determined the phase composition of the Carpathian diatomites in this work. Their internal nanostructure was identified. Nanopores create regular systems that, depending on the variety of diatoms, may have sieve, tubular, or “honeycomb” shapes. Diatomites’ internal structure benefits the absorption capacity of phase-change materials (PCM). The obtained calorimetric thermograms of the organic phase-change material and the diatomite compound highlighted an extension of the temperature range in which phase transformation occurs from 4–5 °C (for pure PCM RT28HC) to 15–17 °C for the composites tested with weight proportions of 1:1 and 4:6. In the case of water-rich varieties, the presence of mixed-package minerals, i.e., montmorillonite, with its small size and specific 2:1 package structure, can hinder the penetration and accumulation of PCM. The ability to bind and accumulate heat will be influenced by the size of the diatomite particles or the relative size of the PCM and pores, i.e., structural and textural features. Full article

Graphite is a critical raw material due to its pivotal role in the green transition; hence, there is a renewed interest in its exploration across Europe. The Chisone and Germanasca Valleys (Piemonte, IT) were home to significant graphite exploitation until the 20th century, owing to the widespread presence of graphite ore bodies hosted in the metasedimentary succession of the Pinerolo Unit in the Dora-Maira Massif (Western Alps). This contribution presents a renewed study on the geology, mineralogy, petrography, and geochemistry of graphite ores and their host rocks, employing OM, SEM-EDS, and BSE, μRaman, and ICP-OES/MS and INAA analyses. Mineralization occurs in two metasedimentary successions: (i) the Bourcet-type succession (meta-conglomerates and meta-sandstones intercalated with meta-siltstones/metapelites) and (ii) the Pons-type succession (meta-siltstones/metapelites intercalated with minor meta-arenites). Graphite occurs as (i) high-purity, fine-grained crystals dispersed within or concentrated in layers along the regional schistosity, or (ii) low-purity, coarse-grained crystals within shear zones. Based on crystallinity, three types of graphite were distinguished: high (Type I), intermediate (Type II), and poor (Type III) crystalline graphite, likely formed under different genetic conditions. The comparison of these findings has implications for future exploration and provides new insights into the metallogeny and geological evolution of the area. Full article

Metal-mining activities inevitably generate contaminants in high quantities, which can pose a risk to soil, water, biota, and humans. This study compares the geochemical properties of waste materials of tailings and waste rock heaps originating from the same high-sulfidation-type epithermal mineralization. Field sampling was conducted in the Recsk Copper Mining Area on the H2 tailings and H7 waste heap, where a total of 48 samples were collected at various depths. The results showed that PTEs were present in varying concentrations and behaved differently in the two waste materials. Copper concentrations were approximately five times higher in H2 tailings (median 1660 mg/kg) than in H7 waste rock (median 347 mg/kg), whereas arsenic was 2.8 times more concentrated in H2 tailings (674 mg/kg vs. 238 mg/kg). Conversely, zinc (114 mg/kg vs. 24 mg/kg), lead (172 mg/kg vs. 42.8 mg/kg), and cadmium (0.83 mg/kg vs. 0.097 mg/kg) show significantly higher concentrations in H7 waste rock. Element mobility analyses revealed that calcium mobility in H7 waste rock (65%) was twice that observed in H2 tailings (32%), with copper showing a threefold higher mobility in H7 despite lower total concentrations. NAG pH values (2.06–3.23) confirmed significant acid-generating potential in both waste types, with the H7 waste rock posing greater immediate environmental risk due to higher element mobility and more advanced weathering indicated by elevated jarosite (4.05%–8.01%) and secondary mineral contents. These findings demonstrate that, despite originating from the same mineralization, the distinct processing histories and physical properties of these materials necessitate unique approaches for successful remediation or secondary raw material extraction. Full article

The growing demand for green and, therefore, sustainable technologies present new challenges for our society. The European Union (EU) identified the critical raw materials (CRMs) and strategic raw materials (SRMs) necessary for these technologies and introduced policies to reduce reliance on external suppliers, which includes investigating the recovery of CRMs from extractive waste. This study assesses the recovery potential of mine waste collected in the Traversella mine district (Piedmont, Italy), known for its polymetallic Fe-Cu-W deposit. The characterization of waste rock samples involved chemical and mineralogical analyses, revealing metallic-bearing minerals such as magnetite and scheelite. Laboratory-scale magnetic and gravity separation tests were carried out and compared. Magnetic separation resulted in a recovery of 75.4% of Fe, 72.3% of Cu, and 83.7% of W, with a weak concentration. Instead, gravity separation produced high-grade Fe (67.6%) and W (1289 ppm) concentrate with lower recovery rates. Full article

The Vali–Janlou kaolin deposit is located in the northern part of the Urmia–Dokhtar magmatic belt, central-northern Iran, and is hosted by middle Eocene rhyodacitic volcanic rocks. The Vali–Janlou kaolin deposit is one of the most important sources of raw material for ceramics industries in Iran. No trace element geochemical characterizations of this deposit have been conducted in detail before, and this is the main objective of the current research work. Kaolinite and quartz are the major mineral phases present in this deposit, accompanied by some minor phases like illite, rutile, pyrophyllite, dickite, alunite, diaspore, and chlorite. The calculation of mass balance changes revealed that the kaolinization of the rhyodacitic rocks was accompanied by the enrichment of Sr, Zr, Hf, Ta, Nb, U, Th, Y, La, and Pr, leaching–fixation of Sm, Nd, and HREEs, and depletion of Rb, Cs, Ba, Pb, V, Cr, Zn, Eu, and Ce. The behavior of trace elements during kaolinization was controlled by factors such as variation in the pH and temperature of the hydrothermal fluids, the residual concentration, and the presence of mineral phases resistant to alteration. The occurrence of negative Eu anomalies during kaolinization indicates plagioclase destruction by high-temperature hydrothermal solutions and also the liberation of Eu²⁺ during a decreasing intensity of hydrothermal alteration. The presence of diaspore, dickite, and pyrophyllite together with the differentiation of HREEs from one to another, the occurrence of robust negative Ce anomalies, the strong positive correlation between P₂O₅ and LOI, and geochemical parameters like Ce + La + Y, Nb + Cr, Rb + Sr, and Y/Ho are all indicative of the effective role of hypogene processes in the evolution of this deposit. Full article