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21 pages, 8591 KB  
Article
Simulation of Compaction Process of Tight Sandstone in Xiashihezi Formation, North Ordos Basin: Insights from SEM, EDS and MIP
by Hongxiang Jin, Feiyang Wang, Chong Han, Chunpu Wang, Yi Wu and Yang Hu
Processes 2025, 13(10), 3191; https://doi.org/10.3390/pr13103191 - 8 Oct 2025
Abstract
The Permian Xiashihezi Formation in the Ordos Basin is a typical tight sandstone gas reservoir, which is characterized by low porosity and strong heterogeneity. Diagenesis plays a crucial role in controlling reservoir quality. However, the multiple phases and types of diagenetic processes throughout [...] Read more.
The Permian Xiashihezi Formation in the Ordos Basin is a typical tight sandstone gas reservoir, which is characterized by low porosity and strong heterogeneity. Diagenesis plays a crucial role in controlling reservoir quality. However, the multiple phases and types of diagenetic processes throughout geological history make the compaction mechanisms highly complex. This study employed a high-temperature and high-pressure diagenesis simulation system to conduct geological simulation experiments. Typical reservoir samples from the 2nd Member of the Permian Xiashihezi Formation were selected for these simulations. The experiments replicated the diagenetic evolution of the reservoirs under various temperature, pressure, and fluid conditions, successfully reproducing the diagenetic sequences. The diagenetic sequence included early-stage porosity reduction through compaction, early carbonate cementation, quartz overgrowth, chlorite rim formation, feldspar dissolution, and late-stage illite and quartz cementation. Mechanical compaction is the primary factor reducing reservoir porosity, exhibiting a distinct four-stage porosity reduction pattern: (1) continuous burial stage (>4000 m); (2) stagnation stage of burial (3900 m–4100 m); (3) the secondary continuous burial stage (>5000 m); (4) tectonic uplift stage (3600 m). The experiments confirmed that the formation of various authigenic minerals is strictly controlled by temperature, pressure, and fluid chemistry. Chlorite rims formed in an alkaline environment enriched with Fe2+ and Mg2+ (simulated temperatures of 280–295 °C), effectively inhibiting quartz overgrowth. Illite appeared at higher temperatures (>300 °C) in platy or fibrous forms. Feldspar dissolution was noticeable upon injection of acidic fluids (simulated organic acids), providing material for authigenic quartz and kaolinite. The key mineral composition significantly impacts reservoir diagenesis. The dissolution released Mg2+ and Fe2+ ions, crucial for forming early chlorite rims in the overlying sandstones, confirming the importance of inter-strata interactions in “source-facies coupling.” Through physical simulation methods, this study deepened the understanding of the diagenetic evolution and compaction mechanisms of tight sandstones. This provides significant experimental evidence and theoretical support for predicting “sweet spot” reservoirs in the area. Full article
(This article belongs to the Topic Exploitation and Underground Storage of Oil and Gas)
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17 pages, 9190 KB  
Article
Mineralogical and Gemological Characteristics and Color Genesis of Zibai Jade
by Linhui Song, Mingyue He, Ziyun Zhang and Ling Yang
Crystals 2025, 15(10), 871; https://doi.org/10.3390/cryst15100871 - 8 Oct 2025
Abstract
Zibai Jade is a recently identified hydrogrossular-dominant jade originating from Shaanxi Province, China. It constitutes a polymineralic aggregate composed predominantly of hydrogrossular, with minor proportions of vesuvianite, diopside, chlorite, uvarovite, and calcite. A multi-method analytical approach was employed to characterize this jade, incorporating [...] Read more.
Zibai Jade is a recently identified hydrogrossular-dominant jade originating from Shaanxi Province, China. It constitutes a polymineralic aggregate composed predominantly of hydrogrossular, with minor proportions of vesuvianite, diopside, chlorite, uvarovite, and calcite. A multi-method analytical approach was employed to characterize this jade, incorporating conventional gemological testing, polarizing microscopy, SEM, XRD, BSE, XRF, and EPMA, as well as UV-Vis and infrared (IR). These techniques enabled a detailed examination of its mineralogy, surface features, and color origin. The stone displays a heterogeneous color distribution, featuring a base hue of light green to yellowish-green, accompanied by distinct occurrences of emerald-green spots, dark green spots, mossy green inclusions, white patches, white veinlets, and a black dot with a green ring. Microanalytical results indicate that the emerald-green spots are principally composed of uvarovite; the dark green spots are dominated by hydrogrossular, diopside, and chlorite; fibrous green inclusions consist mainly of chlorite and Cr-bearing grossular; white patches and veinlets are primarily composed of calcite; and the black dot with a green ring predominantly comprises chromite and uvarovite. Coloration is attributed to the combined influence of Fe and Cr3+. The formation of Zibai Jade involved three mineralization stages: deposition of a carbonate protolith, high-temperature metasomatism, and retrograde alteration. The metasomatism was driven by hydrothermal fluids derived from granodioritic and ultramafic rocks, which provided Si, Al, and the essential Cr, respectively. The interplay of these processes resulted in the development of Zibai Jade, which exhibits a dense texture and attractive coloration. Full article
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18 pages, 11049 KB  
Article
Pore Diagenetic Evolution and Its Coupling Relationship with Natural Gas Accumulation in Tight Sandstone Reservoirs of the Second Member of the Xujiahe Formation, Xinchang Area, Western Sichuan
by Zongze Li, Sibing Liu, Youyi Bi, Junqi Li, Meizhou Deng, Jinxi Wang and Hengyi Gao
Minerals 2025, 15(10), 1052; https://doi.org/10.3390/min15101052 - 3 Oct 2025
Viewed by 174
Abstract
By employing thin section analysis, scanning electron microscopy (SEM), homogenization temperatures of fluid inclusions, and carbon–oxygen isotope analysis of carbonate cements, this study conducted a temporal-quantitative investigation into the porosity evolution of relatively high-quality reservoirs in the Second Member of the Xujiahe Formation [...] Read more.
By employing thin section analysis, scanning electron microscopy (SEM), homogenization temperatures of fluid inclusions, and carbon–oxygen isotope analysis of carbonate cements, this study conducted a temporal-quantitative investigation into the porosity evolution of relatively high-quality reservoirs in the Second Member of the Xujiahe Formation (Xu-2 Member) in the Xinchang area of western Sichuan. The analysis focused on quantifying porosity loss due to compaction, cementation, and porosity enhancement from dissolution. Results indicate that compaction exerted the most significant impact on reservoir quality in the Xu-2 Member, causing over 70% of total porosity loss. Cementation processes, including carbonate cements, silica cements, and authigenic chlorite, further degraded reservoir properties. Authigenic chlorite precipitated earliest at burial depths of 600–800 m, while authigenic quartz and carbonate cements persistently affected the reservoir at depths of 2000–5000 m, reducing porosity by at least 10% (up to 21%). Dissolution processes initiated at approximately 3500 m burial depth, generating secondary porosity of ≥2%, with a maximum increase of 16%. Integrating these findings with the natural gas accumulation history, the coupling relationship between pore evolution and gas accumulation was elucidated. The study reveals that reservoir tightness in the Xu-2 Member developed at burial depths of 4050–5300 m, with large-scale gas accumulation predominantly occurring prior to reservoir densification. The findings provide critical guidance for identifying high-quality tight sandstone reservoirs and optimizing exploration targets in the Xu-2 Member of the Xinchang area, Western Sichuan Basin, thereby supporting efficient development of regional tight gas resources. Full article
(This article belongs to the Special Issue Natural and Induced Diagenesis in Clastic Rock)
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36 pages, 9762 KB  
Article
Mineral Prospectivity Mapping for Exploration Targeting of Porphyry Cu-Polymetallic Deposits Based on Machine Learning Algorithms, Remote Sensing and Multi-Source Geo-Information
by Jialiang Tang, Hongwei Zhang, Ru Bai, Jingwei Zhang and Tao Sun
Minerals 2025, 15(10), 1050; https://doi.org/10.3390/min15101050 - 3 Oct 2025
Viewed by 113
Abstract
Machine learning (ML) algorithms have promoted the development of predictive modeling of mineral prospectivity, enabling data-driven decision-making processes by integrating multi-source geological information, leading to efficient and accurate prediction of mineral exploration targets. However, it is challenging to conduct ML-based mineral prospectivity mapping [...] Read more.
Machine learning (ML) algorithms have promoted the development of predictive modeling of mineral prospectivity, enabling data-driven decision-making processes by integrating multi-source geological information, leading to efficient and accurate prediction of mineral exploration targets. However, it is challenging to conduct ML-based mineral prospectivity mapping (MPM) in under-explored areas where scarce data are available. In this study, the Narigongma district of the Qiangtang block in the Himalayan–Tibetan orogen was chosen as a case study. Five typical alterations related to porphyry mineralization in the study area, namely pyritization, sericitization, silicification, chloritization and propylitization, were extracted by remote sensing interpretation to enrich the data source for MPM. The extracted alteration evidences, combined with geological, geophysical and geochemical multi-source information, were employed to train the ML models. Four machine learning models, including artificial neural network (ANN), random forest (RF), support vector machine and logistic regression, were employed to map the Cu-polymetallic prospectivity in the study area. The predictive performances of the models were evaluated through confusion matrix-based indices and success-rate curves. The results show that the classification accuracy of the four models all exceed 85%, among which the ANN model achieves the highest accuracy of 96.43% and a leading Kappa value of 92.86%. In terms of predictive efficiency, the RF model outperforms the other models, which captures 75% of the mineralization sites within only 3.5% of the predicted area. A total of eight exploration targets were delineated upon a comprehensive assessment of all ML models, and these targets were further ranked based on the verification of high-resolution geochemical anomalies and evaluation of the transportation condition. The interpretability analyses emphasize the key roles of spatial proxies of porphyry intrusions and geochemical exploration in model prediction as well as significant influences everted by pyritization and chloritization, which accords well with the established knowledge about porphyry mineral systems in the study area. The findings of this study provide a robust ML-based framework for the exploration targeting in greenfield areas with good outcrops but low exploration extent, where fusion of a remote sensing technique and multi-source geo-information serve as an effective exploration strategy. Full article
17 pages, 11781 KB  
Article
Identifying New Copper Mineralization via Multispectral Remote Sensing (MSRS) and Short-Wave Infrared (SWIR) Spectral Analysis in Dingyang, Western Gangdese Belt, Xizang
by Zhibin Li, Zhaxi PuBu, Xian Che, Gen Chen, Jiangang Wei, Deng Pan and Xiaojia Jiang
Minerals 2025, 15(10), 1045; https://doi.org/10.3390/min15101045 - 1 Oct 2025
Viewed by 235
Abstract
The Gangdese metallogenic belt (GMB), spanning nearly 2000 km across central Tibet, represents the primary copper–polymetallic metallogenic belt in Tibet and a world-class porphyry copper province. However, extreme high-altitude conditions, ecological fragility, and limited accessibility in western GMB have significantly constrained the efficacy [...] Read more.
The Gangdese metallogenic belt (GMB), spanning nearly 2000 km across central Tibet, represents the primary copper–polymetallic metallogenic belt in Tibet and a world-class porphyry copper province. However, extreme high-altitude conditions, ecological fragility, and limited accessibility in western GMB have significantly constrained the efficacy of conventional exploration methods. Identifying effective mineralogical indicators and rapidly delineating mineralization–hydrothermal centers within this metallogenic system remain critical challenges for exploration geologists. This study integrates multispectral remote sensing (MSRS; Sentinel-2) with short-wave infrared (SWIR) spectral analysis to establish mineral spectroscopic exploration indicators for the periphery of the Zhunuo porphyry copper ore-concentrated area. Principal Component Analysis (PCA) and band ratio techniques were employed to delineate remote sensing alteration anomalies, followed by SWIR spectral features to identify mineralization–hydrothermal centers. Hydrothermal alteration in the study area is dominated by sericite, chlorite, and epidote, with subordinate carbonate and sulfate minerals. Multispectral anomalies (Al-OH, ferric contamination, and carbonate alterations) in the Dingyang area exhibit intensity and compositional patterns comparable to those of the Cimabanshuo, Beimulang, and Zhigunong deposits, indicating high mineralization potential. SWIR analysis identified sericite-based exploration indicators (Pos2200 < 2203 nm, Dep2200 > 0.3, SWIR-IC > 1.6). A Spectral Feature-Based Geological Content Method (SFGCM) model was developed to delineate mineralization–hydrothermal centers, revealing new malachite and azurite mineralization in the Dingyang area. The MSRS-SWIR provides a novel perspective for applying spectroscopy to rapidly identify porphyry copper mineralized hydrothermal centers in high-altitude, ecologically fragile areas. Full article
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32 pages, 12542 KB  
Article
Minor and Trace Elements in Copper Tailings: A Mineralogical and Geometallurgical Approach to Identify and Evaluate New Opportunities
by Zina Habibi, Nigel J. Cook, Kathy Ehrig, Cristiana L. Ciobanu, Yuri T. Campo-Rodriguez and Samuel A. King
Minerals 2025, 15(10), 1018; https://doi.org/10.3390/min15101018 - 26 Sep 2025
Viewed by 397
Abstract
Reliable information on the chemical and physical makeup of mine tailings is critical in meeting environmental and regulatory requirements, as well as identifying whether contained elements, including critical minerals, might be economically recovered in future to meet growing demands. Detailed mineralogical characterization, supported [...] Read more.
Reliable information on the chemical and physical makeup of mine tailings is critical in meeting environmental and regulatory requirements, as well as identifying whether contained elements, including critical minerals, might be economically recovered in future to meet growing demands. Detailed mineralogical characterization, supported by chemical assays and automated mineralogy (MLA) data on different size fractions, underpins a case study of flotation tailings from the processing plant at the Carrapateena mine, South Australia. The study provides valuable insights into the deportment of minor and critical elements, including rare earth elements (REEs), along with uranium (U). REE-minerals are represented by major phosphates (monazite and florencite) and subordinate REE-fluorocarbonates (bastnäsite and synchysite). More than half the REE-minerals are concentrated in the finest size fraction (−10 μm). REEs in coarser fractions are largely locked in gangue, such that economic recovery is unlikely to be viable. MLA data shows that the main REE-minerals all display specific associations with gangue, which change with particle size. Quartz and hematite are the most common associations, followed by sericite. Synchysite shows a strong affiliation to carbonates. The contents of other critical elements (e.g., tungsten, molybdenum, cobalt) are low and for the most part occur within other common minerals as submicron-sized inclusions or in the lattice, rather than discrete minerals. Nevertheless, analysis of mine tailings from a large mining–processing operation provides an opportunity to observe intergrowth and replacement relationships in a composite sample representing different ore types from across the deposit. U-bearing species are brannerite (associated with rutile and chlorite), coffinite (in quartz), and uraninite (in hematite). Understanding the ore mineralogy of the Carrapateena deposit and how the ore has evolved in response to overprinting events is advanced by observation of ore textures, including between hematite and rutile, rutile and brannerite, zircon and xenotime, and the U-carbonate minerals rutherfordine and wyartite, the latter two replacing pre-existing U-minerals (uraninite, coffinite, and brannerite). The results of this study are fundamental inputs into future studies evaluating the technical and economic viability of potentially recovering value metals at Carrapateena. They can also guide efforts in understanding the distributions of valuable metals in analogous tailings from elsewhere. Lastly, the study demonstrates the utility of geometallurgical data on process materials to assist in geological interpretation. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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31 pages, 14210 KB  
Article
Evaluation of Geogenic Enrichment Using Satellite, Geochemical, and Aeromagnetic Data in the Central Anti-Atlas (Morocco): Implications for Soil Enrichment
by Mouna Id-Belqas, Said Boutaleb, Fatima Zahra Echogdali, Mustapha Ikirri, Hasna El Ayady and Mohamed Abioui
Earth 2025, 6(4), 113; https://doi.org/10.3390/earth6040113 - 25 Sep 2025
Viewed by 392
Abstract
Natural geogenic effects lead to alterations in soil heavy metal concentrations. This study assesses the presence of elevated trace-element concentrations in the Oued Irriri watershed in southeastern Morocco. ASTER satellite imagery, geochemical, and aeromagnetic data are combined to determine the origin of these [...] Read more.
Natural geogenic effects lead to alterations in soil heavy metal concentrations. This study assesses the presence of elevated trace-element concentrations in the Oued Irriri watershed in southeastern Morocco. ASTER satellite imagery, geochemical, and aeromagnetic data are combined to determine the origin of these anomalies. Processing of ASTER images delineated alteration zones coinciding with areas of high heavy metal anomalies by detecting hydrothermal alteration minerals, including muscovite, montmorillonite, illite, hematite, jarosite, chlorite, and epidote. Principal Component Analysis (PCA) of geochemical data distribution in soils enabled the characterization of variations in trace-element concentrations, the extraction of geochemical anomalies, and the identification of potential sources of contamination. Comparing satellite image processing results with geochemical analyses facilitated the production of a geogenic enrichment map. The study results indicate high enrichment levels of zinc, Molybdenum, and bismuth in the western basin, of purely lithological origin. Hydrothermal alteration surfaces intersect geochemical anomaly zones in the north and northeast, primarily showing the impact of fault rooting on the surface deposition of Cu, Ba, Hg, and Pb-rich deposits. This study developed a geogenic enrichment map indicating naturally affected areas, identifying potential risks to eco-environmental systems, and better preventing the effects of geogenic enrichment. Full article
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19 pages, 3950 KB  
Article
Provenance of Claystones and Lithium Occurrence State in the Xishanyao Formation, Liuhuanggou Coal Mine
by Jie Liu, Bo Wei, Shuo Feng, Xin Li, Wenfeng Wang, Rongkun Jia and Kexin Che
Minerals 2025, 15(10), 1004; https://doi.org/10.3390/min15101004 - 23 Sep 2025
Viewed by 292
Abstract
Strategic lithium resources are critical to national security and have attained heightened importance in contemporary geopolitical, economic, and military contexts. Persistent geochemical anomalies of lithium were first identified in coal-bearing claystones of the Middle Jurassic Xishanyao Formation at the Liuhuanggou Coal Mine in [...] Read more.
Strategic lithium resources are critical to national security and have attained heightened importance in contemporary geopolitical, economic, and military contexts. Persistent geochemical anomalies of lithium were first identified in coal-bearing claystones of the Middle Jurassic Xishanyao Formation at the Liuhuanggou Coal Mine in the southern Junggar Basin, Xinjiang. In this study, a suite of analytical techniques, including X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, time-of-flight secondary ion mass spectrometry, and sequential chemical extraction, was employed to investigate the provenance, depositional environment, and modes of lithium occurrence in the claystone. Results indicated that the claystone at the Liuhuanggou Coal Mine was dominated by moderately felsic rocks. The notable enrichment of lithium in the Liuhuanggou coal mine claystone indicates favorable metallogenic potential. Lithium was primarily hosted in the aluminosilicate-bound fraction with inorganic affinity and was structurally incorporated within clay minerals, such as kaolinite, illite, and Fe-rich chlorite (chamosite). Lithium-rich claystone was deposited under intense chemical weathering conditions in a transitional, slightly brackish environment characterized by elevated temperatures and low oxygen levels. These findings advance our understanding of sedimentary lithium mineralization mechanisms and offer direct practical guidance for lithium resource exploration and metallogenic prediction in the Xinjiang region, thereby supporting the development of efficient extraction technologies. Full article
(This article belongs to the Section Mineral Deposits)
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23 pages, 30956 KB  
Article
Microstructures and Anisotropy of Slates from Northern China
by Jingyi Huang, Hans-Rudolf Wenk and Michelle Devoe
Minerals 2025, 15(9), 979; https://doi.org/10.3390/min15090979 - 15 Sep 2025
Viewed by 353
Abstract
Slates transform from shales at relatively low-grade metamorphic conditions. They often reveal highly anisotropic microstructures and very strong crystal alignment that must be considered in seismic modeling and engineering construction. In this paper, we investigate nine slate samples from four regions in northern [...] Read more.
Slates transform from shales at relatively low-grade metamorphic conditions. They often reveal highly anisotropic microstructures and very strong crystal alignment that must be considered in seismic modeling and engineering construction. In this paper, we investigate nine slate samples from four regions in northern China: Fangshan, Beijing; Xushui, Hebei; Damao Qi, Inner Mongolia; and Zhengxiangbai Qi, Inner Mongolia. The microstructural characteristics were analyzed with scanning electron microscopy and explored with digital crystal size distribution analysis. Preferred crystal orientation characteristics of slate minerals were investigated with high-energy synchrotron X-ray diffraction and subsequent Rietveld refinement. This research shows that the main components of slates in this study are quartz, muscovite, chlorite, and minor orthoclase. In terms of morphology, muscovite, chlorite, and quartz are strongly elongated and oriented. The crystallographic orientation of sheet silicates is very strong, exceeding 100 multiples of random distribution for chlorite from Fangshan. However, quartz with a preferred strong shape orientation has a crystallographic preferred orientation close to random. The preferred orientation characteristics of minerals serve as a basis for calculating elastic properties and anisotropies of the Chinese slate samples that contribute significantly to seismic anisotropy documented in northern China. Full article
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20 pages, 11423 KB  
Article
Clay Mineral Characteristics and Smectite-to-Illite Transformation in the Chang-7 Shale, Ordos Basin: Processes and Controlling Factors
by Kun Ling, Ziyi Wang, Yaqi Cao, Yifei Liu and Lin Dong
Minerals 2025, 15(9), 951; https://doi.org/10.3390/min15090951 - 5 Sep 2025
Cited by 1 | Viewed by 683
Abstract
As critical components in continental shale systems, the composition and evolution of clay minerals are fundamental to their diagenetic processes and petrophysical properties. The Chang-7 shales in the Ordos Basin exhibit abundant clay mineral content, offering a valuable case study for clay mineral [...] Read more.
As critical components in continental shale systems, the composition and evolution of clay minerals are fundamental to their diagenetic processes and petrophysical properties. The Chang-7 shales in the Ordos Basin exhibit abundant clay mineral content, offering a valuable case study for clay mineral research under moderate diagenetic conditions. This study employed XRD analysis to determine the whole-rock mineralogy, clay mineral composition, and the evolution characteristics of illite-smectite mixed-layer minerals (I/S). Comprehensive clay mineral datasets compiled from 13 newly analyzed wells and existing literature revealed distinct lateral distribution patterns. Total Organic Carbon (TOC) analysis and vitrinite reflectance (Ro) measurements provided systematic quantification of organic matter abundance and thermal maturation parameters in the studied samples. The results reveal that the Chang-7 shale exhibits a characteristic clay mineral assemblage, with I/S (average 44.2%) predominating over illite (34.7%), followed by chlorite (15.6%) and limited kaolinite (5.4%). Frequent volcanic activities provided substantial precursor materials for smectite formation, which actively participated in subsequent illitization processes, while chlorite and kaolinite distributions were predominantly controlled by provenance inputs and sedimentary facies, respectively. Inconsistencies exist between diagenetic stages inferred from I/S mixed-layer ratios and Ro values, particularly in low-maturity samples exhibiting accelerated illitization. The observed negative correlation between TOC content and mixed-layer ratios in Well YY1 and YSC Section samples demonstrates the catalytic role of organic matter in facilitating smectite-to-illite transformation. These results systematically clarify the coupled effects of sedimentary-diagenetic processes, offering new insights into the mutual interactions between inorganic and organic phases during illitization under natural geological conditions. The findings advance the understanding of Chang-7 shale oil and gas systems and offer practical guidance for future exploration. Full article
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26 pages, 15275 KB  
Article
Application of Multispectral Data in Detecting Porphyry Copper Deposits: The Case of Aidarly Deposit, Eastern Kazakhstan
by Elmira Serikbayeva, Kuanysh Togizov, Dinara Talgarbayeva, Elmira Orynbassarova, Nurmakhambet Sydyk and Aigerim Bermukhanova
Minerals 2025, 15(9), 938; https://doi.org/10.3390/min15090938 - 3 Sep 2025
Viewed by 590
Abstract
The Koldar Massif in southeastern Kazakhstan is a geologically complex area with potential for porphyry copper and rare-metal mineralization. This study applies a multi-scale remote sensing approach to delineate hydrothermal alteration zones using medium-resolution ASTER imagery and very high-resolution WorldView-3 data. Image processing [...] Read more.
The Koldar Massif in southeastern Kazakhstan is a geologically complex area with potential for porphyry copper and rare-metal mineralization. This study applies a multi-scale remote sensing approach to delineate hydrothermal alteration zones using medium-resolution ASTER imagery and very high-resolution WorldView-3 data. Image processing techniques—including false color composites (FCCs), band ratios (BRs), and the Spectral Angle Mapper (SAM)—were employed across the VNIR and SWIR bands to detect alteration minerals such as kaolinite, illite, montmorillonite, chlorite, epidote, calcite, quartz, and muscovite. These minerals correspond to argillic, propylitic, and phyllic alteration zones. While ASTER supported regional-scale mapping, WorldView-3 enabled detailed analysis at the Aidarly deposit. Validation was performed using copper occurrences, lithogeochemical anomaly contours, and ore body boundaries. The results show a strong spatial correlation between the mapped alteration zones and known mineralization patterns. Importantly, this study reports the identification of a previously undocumented hydrothermal zone north of the Aidarly deposit, detected using WorldView-3 data. This zone exhibits concentric phyllic and argillic alterations, similar to those at Aidarly, and may represent an extension of the mineralized system. Unlike earlier studies on the Aktogay deposit based on ASTER and Landsat-8, this work focuses on the Aidarly deposit and introduces higher-resolution analysis and SAM-based classification, offering improved spatial accuracy and target delineation. The proposed methodology provides a reproducible and scalable workflow for early-stage mineral exploration in underexplored regions, especially where field access is limited. These results highlight the value of high-resolution remote sensing in detecting concealed porphyry copper systems in structurally complex terrains. Full article
(This article belongs to the Section Mineral Exploration Methods and Applications)
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30 pages, 11585 KB  
Article
Multifractal Characterization of Marine Shale Pore Structure Alteration Induced by Supercritical CO2–Water–Rock Interaction
by Haonan Wei, Yi Du, Changqing Fu, Gaoqiang Fu, Yingfang Zhou, Jinfeng Ma, Zhenliang Wang, Zhejun Pan and Wei Gao
Fractal Fract. 2025, 9(9), 582; https://doi.org/10.3390/fractalfract9090582 - 2 Sep 2025
Viewed by 501
Abstract
Supercritical CO2 (ScCO2) injection has emerged as a promising method to enhance shale gas recovery while simultaneously achieving CO2 sequestration. This research investigates how ScCO2 interacts with water and shale rock, altering the pore structure characteristics of shale [...] Read more.
Supercritical CO2 (ScCO2) injection has emerged as a promising method to enhance shale gas recovery while simultaneously achieving CO2 sequestration. This research investigates how ScCO2 interacts with water and shale rock, altering the pore structure characteristics of shale reservoirs. The study examines shale samples from three marine shale formations in southern China under varying thermal and pressure regimes simulating burial conditions at 1000 m (45 °C and 10 MPa) and 2000 m (80 °C and 20 MPa). The research employs multiple analytical techniques including XRD for mineral composition analysis, MICP, N2GA, and CO2GA for comprehensive pore characterization, FE–SEM for visual observation of mineral and pore changes, and multifractal theory to analyze pore structure heterogeneity and connectivity. Key findings indicate that ScCO2–water–shale interactions lead to dissolution of minerals such as kaolinite, calcite, dolomite, and chlorite, and as the reaction proceeds, substantial secondary mineral precipitation occurs, with these changes being more pronounced under 2000 m simulation conditions. Mineral dissolution and precipitation cause changes in pore structure parameters of different pore sizes, with macropores showing increased PV and decreased SSA, mesopores showing decreased PV and SSA, and micropores showing insignificant changes. Moreover, mineral precipitation effects are stronger than dissolution effects. These changes in pore structure parameters lead to alterations in multifractal parameters, with mineral precipitation reducing pore connectivity and consequently enhancing pore heterogeneity. Correlation analysis further revealed that H and D−10D10 exhibit a significant negative correlation, confirming that reduced connectivity corresponds to stronger heterogeneity, while mineral composition strongly controls the multifractal responses of macropores and mesopores, with micropores mainly undergoing morphological changes. However, these changes in micropores are mainly manifested as modifications of internal space. Siliceous shale samples exhibit stronger structural stability compared to argillaceous shale, which is attributed to the mechanical strength of the quartz framework. By integrating multifractal theory with multi–scale pore characterization, this study achieves a unified quantification of shale pore heterogeneity and connectivity under ScCO2–water interactions at reservoir–representative pressure–temperature conditions. This novelty not only advances the methodological framework but also provides critical support for understanding CO2–enhanced shale gas recovery mechanisms and CO2 geological sequestration in depleted shale gas reservoirs, highlighting the complex coupling between geochemical reactions and pore structure evolution. Full article
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16 pages, 6660 KB  
Article
Mineralogical Characteristics and Color Genesis of Vesuvianite Jade from Hanzhong, Shaanxi Province, China
by Ye Yuan, Miao Shi, Ru Jia, Xuren Huang and Yi Zhang
Crystals 2025, 15(9), 765; https://doi.org/10.3390/cryst15090765 - 28 Aug 2025
Viewed by 684
Abstract
A new type of vesuvianite jade has recently been discovered in Hanzhong City, Shaanxi Province, China. However, a systematic investigation into its mineralogical characteristics and the origin of its color is currently lacking. In this study, the gemological, mineralogical, and spectroscopic properties of [...] Read more.
A new type of vesuvianite jade has recently been discovered in Hanzhong City, Shaanxi Province, China. However, a systematic investigation into its mineralogical characteristics and the origin of its color is currently lacking. In this study, the gemological, mineralogical, and spectroscopic properties of the Hanzhong vesuvianite jade were comprehensively analyzed using a suite of modern analytical techniques, including standard gemological testing, polarizing microscopy, X-ray powder diffraction, Fourier-transform infrared spectroscopy, laser Raman spectroscopy, UV-visible absorption spectroscopy, and X-ray fluorescence spectroscopy. The origin of the jade’s color was also preliminarily investigated. The results indicate that the samples are primarily composed of vesuvianite, with associated minerals including minor amounts of grossular, chlorite, and diopside, and trace amounts of calcite, epidote, chromite, and titanite. The pale green patches consist mainly of chlorite and grossular, the dark green bands are predominantly chlorite, and the dark brown patches are composed of abundant, disseminated microcrystalline chromite intermixed with uvarovite (calcium chromium garnet). The major chemical components of the vesuvianite jade matrix are SiO2, Al2O3, and CaO. Specifically, SiO2 ranges from 37.01 to 38.54 wt.%, Al2O3 from 18.48 to 22.84 wt.%, and CaO from 37.16 to 40.04 wt.%. Minor amounts include MgO (0.76–4.39 wt.%) and FeOT (total iron expressed as FeO, 0.56–2.09 wt.%). The yellowish-green color of the matrix originates from a combination of ligand-to-metal charge transfer of Fe3+, crystal field transitions of Fe3+, and intervalence charge transfer between Fe2+ and Fe3+ in vesuvianite. The emerald-green color of the patches results from the synergistic effect of Fe and Cr; Fe provides a yellowish-green background color, upon which the crystal field transitions of Cr3+ (indicated by a doublet at 686/696 nm) impose strong absorption in the red region, resulting in a more vivid green hue. Full article
(This article belongs to the Collection Topic Collection: Mineralogical Crystallography)
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22 pages, 7924 KB  
Article
Confirmation of Significant Iron Formations During “Boring Billion” in Altyn Region, China: A Case Study of the Dimunalike Iron Deposit
by Wencheng Liu, Fanqi Kong, Haibo Ding, Jing Zhang and Mingtian Zhu
Minerals 2025, 15(9), 905; https://doi.org/10.3390/min15090905 - 26 Aug 2025
Viewed by 648
Abstract
It is generally believed that the ancient oceans during the “boring billion” (1.85–0.8 Ga) lacked the capacity to form large-scale iron formations (IFs), though localized small-scale IFs deposition persisted. The Altyn region of China hosts abundant IFs, with the Dimunalike IFs being the [...] Read more.
It is generally believed that the ancient oceans during the “boring billion” (1.85–0.8 Ga) lacked the capacity to form large-scale iron formations (IFs), though localized small-scale IFs deposition persisted. The Altyn region of China hosts abundant IFs, with the Dimunalike IFs being the largest and most representative, characterized by typical banded iron–silica layers. Detailed fieldwork identified a tuff layer conformably contacting the IFs at the roof rocks of IFs and a ferruginous mudstone layer at the floor rocks of IFs in drill core ZK4312. Geochemical and zircon U-Pb-Hf isotopic analyses were performed. The tuff has a typical tuff structure, mostly made of quartz, and contains a significant amount of natural sulfur. It also has high SiO2 content (77.90%–80.49%) and sulfur content (0.78%–3.06%). The ferruginous mudstone has a volcanic clastic structure and is mainly composed of quartz and chlorite, with abundant coeval pyrite. It shows lower SiO2 content (53.83%–60.32%) and higher TFe2O3 content (10.29%–16.24%). Both layers share similar rare earth element (REE) distribution patterns and trace element compositions, with light REE enrichment and negative Eu, Nb, and Ti anomalies, consistent with arc volcanic geochemistry. Zircon U-Pb ages indicate crystallization of the tuff at 1102 ± 13 Ma and maximum deposition of the mudstone at 1110 ± 41 Ma. These data suggest formation during different stages of the same volcanic–sedimentary process. The εHf(t) values (3.60–12.35 for tuff, 2.92–8.19 for mudstone) resemble those of Algoma-type IF host rocks, implying derivation from re-melted new crust. The Dimunalike IFs likely formed in a submarine volcanic–sedimentary environment. In conclusion, although the Mesoproterozoic ocean was generally in a low-oxygen state, which was not conducive to large-scale IF deposition, localized submarine volcanic–hydrothermal activity could still lead to IF formation. Full article
(This article belongs to the Special Issue Geochemical, Isotopic, and Biotic Records of Banded Iron Formations)
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Article
Modes of Occurrence of Critical Elements (Li-Ga-Nb-Zr-REE) in the Late Paleozoic Coals from the Jungar Coalfield, Northern China: An Approach of Sequential Chemical Extraction
by Xiangyang Liu, Yanbo Zhang, Wei Zhao, Jian Wu and Jian Bai
Minerals 2025, 15(9), 889; https://doi.org/10.3390/min15090889 - 22 Aug 2025
Viewed by 562
Abstract
In recent years, recovering critical elements from coal has attracted considerable interest due to their significant potential and resulting advantages. A prime example is the coal-hosted Al-Ga-Li-REE deposit within the Jungar Coalfield of Inner Mongolia, northern China, where lithium (Li), gallium (Ga), and [...] Read more.
In recent years, recovering critical elements from coal has attracted considerable interest due to their significant potential and resulting advantages. A prime example is the coal-hosted Al-Ga-Li-REE deposit within the Jungar Coalfield of Inner Mongolia, northern China, where lithium (Li), gallium (Ga), and aluminum (Al) are successfully extracted from coal ash. However, the specific forms in which these elements exist, crucial for developing effective extraction methods, remain unquantified. This research investigated the distribution of Li, Ga, Nb, Zr, and rare earth elements (REEs) within the coal. The study employed a combination of analytical techniques, including inductively coupled plasma mass spectrometry (ICP-MS), sequential chemical extraction (SCE), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS), and X-ray powder diffraction analysis (XRD). The analyzed coals exhibited enriched levels of Li, Ga, Zr, Nb, and REEs. Kaolinite and boehmite were the primary mineral constituents, along with minor amounts of calcite, pyrite, rutile, goyazite, and chlorite. Sequential chemical extraction revealed that Li and Ga are primarily associated with aluminosilicate phases (71.84%–84.39%) and, to a lesser degree, organic matter (12.15%–25.09%). Zirconium and Nb were also predominantly found within aluminosilicates (68.53%–95.96%). REEs occur mainly in carbonate (28.28%–60.78%), aluminosilicate (11.6%–33.08%), and organic (22.04%–29.42%) fractions. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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