Minerals

13 pages, 5095 KiB

Open AccessArticle

Dissolution of Diamond in Water–Chloride Fluids at Mantle P-T Conditions

by Alexander Khokhryakov, Alexey Kruk, Alexander Sokol and Denis Nechaev

Minerals 2025, 15(9), 897; https://doi.org/10.3390/min15090897 - 24 Aug 2025

Syngenetic fluid inclusions in natural diamonds are indicators of the composition of fluids responsible for growth and crystallization conditions. The chloride concentration in saline fluid inclusions of natural diamonds reaches 50 wt%. We study the dissolution of diamonds in the H₂O-KCl-NaCl [...] Read more.

Syngenetic fluid inclusions in natural diamonds are indicators of the composition of fluids responsible for growth and crystallization conditions. The chloride concentration in saline fluid inclusions of natural diamonds reaches 50 wt%. We study the dissolution of diamonds in the H₂O-KCl-NaCl system at temperatures of 1200 °C and 1400 °C and a pressure of 5.5 GPa using a BARS high-pressure multi-anvil apparatus. Two scenarios of diamond dissolution were experimentally investigated: (i) metasomatism by saline brines at high oxygen fugacity of the magnetite–hematite buffer; (ii) interaction with reduced carbon-unsaturated water–chloride fluid at low fO₂ imposed by the iron–wüstite buffer. It is found that the presence of alkaline chlorides in the aqueous fluid significantly accelerates diamond dissolution at high oxygen fugacity but inhibits the process under reduced conditions. The morphology of diamond dissolution features is controlled by the presence of water in the fluid over the entire range of the studied P-T-fO₂ conditions. Experimental results indicate that the interaction with oxidizing highly saline fluids during metasomatic events could negatively affect diamond preservation in mantle rocks and eventually lead to the formation of uneconomic kimberlites. Under reducing conditions, water–chloride fluids favor diamond preservation. Full article

(This article belongs to the Special Issue Unveiling the Depths: Advances in Kimberlite Research as Windows into Earth’s Evolution and Resource Potential)

21 pages, 5880 KiB

Open AccessArticle

Petrographic and Geochemical Insights from Fibrous Calcite Veins: Unraveling Overpressure and Fracture Evolution in the Upper Permian Dalong Formation, South China

by An Liu, Lin Chen, Shu Jiang, Hai Li, Baomin Zhang, Yingxiong Cai, Jingyu Zhang, Wei Wei and Feiyong Xia

Minerals 2025, 15(9), 896; https://doi.org/10.3390/min15090896 - 24 Aug 2025

Abstract

The characteristics and evolution of fibrous calcite veins in organic-rich shales have gained significant attention due to the recent advancements in shale oil and gas exploration. However, the fibrous calcite veins in the Upper Permian Dalong Formation remain lacking in awareness. To investigate [...] Read more.

The characteristics and evolution of fibrous calcite veins in organic-rich shales have gained significant attention due to the recent advancements in shale oil and gas exploration. However, the fibrous calcite veins in the Upper Permian Dalong Formation remain lacking in awareness. To investigate the formation and significance of bedding-parallel fibrous calcite veins in the Dalong Formation, we conducted an extensive study utilizing petrography, geochemistry, isotopic analysis, and fluid inclusion studies on outcrops of the Dalong Formation in South China. Our findings reveal that fibrous calcite veins predominantly develop in the middle section of the Dalong Formation, specifically within the transitional interval between siliceous and calcareous shales, characterized by symmetric, antitaxial fibrous calcite veins. The δ¹³C values of these veins exhibit a broad range (−4.53‰ to +3.39‰) and display a decreasing trend in the directions of fiber growth from the central part, indicating an increased contribution of organic carbon to the calcite veins. Additionally, a consistent increase in trace element concentrations from the central part toward the fiber growth directions suggests a singular fluid source in a relatively closed environment, while other samples exhibit no distinct pattern, possibly due to the mixing of fluids from multiple layers resulting from repeated opening and closing of bedding-parallel fractures in the shales. The notable difference in δEu between the fibers on either side of the median zone indicates that previously formed veins acted as barriers, impeding the mixing of fluids, with the variation in δEu reflecting the differing sedimentary properties of the surrounding rocks. The in situ U-Pb dating of fibrous calcite veins yields an absolute age of 211 ± 23 Ma, signifying formation during the Late Triassic, which correlates with a shale maturity of 1.0‰ to 1.25‰. This integrated study suggests that the geochemical records of fibrous calcite veins document the processes related to overpressure generation and the opening and healing of bedding-parallel fractures within the Dalong Formation. Full article

(This article belongs to the Special Issue Organic Petrology and Geochemistry: Exploring the Organic-Rich Facies)

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14 pages, 1250 KiB

Open AccessArticle

A Study on Copper Mine Tailings to Be Used as Precursor of Alkali-Activated Materials for Construction Applications

by Luis Morales-Castro, Estefania Loyola, Matias Castro-Quijada, Felipe Vargas, Ivan Navarrete, Claudia Eugenin, Carlos Marquardt and Alvaro Videla

Minerals 2025, 15(9), 895; https://doi.org/10.3390/min15090895 - 23 Aug 2025

Abstract

This research presents a novel methodology to classify copper tailings according to their potential as alkali-activated materials (AAMs) for construction applications. The methodology includes geochemical and mineralogical characterization via QEMSCAN and X-ray fluorescence, with mechanical performance evaluation through compressive strength test (UCS). A [...] Read more.

This research presents a novel methodology to classify copper tailings according to their potential as alkali-activated materials (AAMs) for construction applications. The methodology includes geochemical and mineralogical characterization via QEMSCAN and X-ray fluorescence, with mechanical performance evaluation through compressive strength test (UCS). A three-phase diagram based on Al₂O₃, Fe₂O₃, and CaO-MgO-K₂O is proposed for a fast screening of copper tailing potential to be used as a construction material. In this paper, three copper tailings were chosen to test the methodology, and a set of five samples for each tailing have been geopolymerized for testing. Copper tailing samples were mixed with 0, 2.5, 5, 7.5 and 10% by mass of Ordinary Portland Cement (OPC) to evaluate the effect on performance when a chemical co-activator is used to improve material reactivity. Compressive strength testing was applied on 2 cm³ cubes after 28 days of curing at 60 °C, yielding values from 6 to 26.1 MPa. The best performing sample featured a Si/Al ≅ 3 ratio and a mineralogy with significant presence of reactive species such as plagioclase and K-feldspar (≅42%). In contrast, high levels of Fe₂O₃ (≥12%), clay (≥7%), and pyrite (≥4%) were associated with reduced mechanical performance. Full article

(This article belongs to the Special Issue Alkali-Activated Cements and Concretes, 2nd Edition)

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24 pages, 9686 KiB

Open AccessArticle

The Petrogenesis of Early Permian Granodiorites in the Northern Segment of the Changning-Menglian Suture Zone, Western Yunnan, and Their Tectonic Implications

by Jiajia Liu, Zhen Jia, Jiyuan Wang, Feng Zhao, Junbao Luo, Feiyang Xu and Fuchuan Chen

Minerals 2025, 15(9), 894; https://doi.org/10.3390/min15090894 - 23 Aug 2025

Abstract

The Changning-Menglian suture zone, as the remnant of the main Paleo-Tethyan oceanic basin in its southern segment, lacks direct magmatic evidence constraining the timing of subduction initiation in its northern segment. The petrogenesis and tectonic setting of the newly discovered Early Permian (~280 [...] Read more.

The Changning-Menglian suture zone, as the remnant of the main Paleo-Tethyan oceanic basin in its southern segment, lacks direct magmatic evidence constraining the timing of subduction initiation in its northern segment. The petrogenesis and tectonic setting of the newly discovered Early Permian (~280 Ma) Wayao granodiorite in the northern segment remain unclear, hindering our understanding of the timing of subduction initiation and processes of the Paleo-Tethyan Ocean in the Changning-Menglian suture zone. This study presents systematic petrographic, zircon U-Pb geochronological, whole-rock major and trace element geochemical, and Sr-Nd-Hf isotopic analyses on the newly discovered Early Permian granodiorite in the Wayao area, northern segment of the Changning-Menglian suture zone, western Yunnan. Zircon U-Pb dating yields a crystallization age of ca. 280 Ma, confirming its emplacement during the Early Permian. The petrogeochemical characteristics indicate that it belongs to the metaluminous, calc-alkaline series of I-type granite. It is enriched in large-ion lithophile elements (LILEs; e.g., Rb, Th, U, La, Pb) and depleted in high-field-strength elements (HFSEs; e.g., Ba, Nb, Sr, Ti), exhibiting a pronounced negative Eu anomaly. Whole-rock Sr-Nd isotopes (εNd(t) = −5.6–−6.1) and zircon Hf isotopes (εHf(t) = −1.34–−10.01) suggest that the magma was predominantly derived from the partial melting of ancient crustal material (primarily metamorphosed basic rocks, such as amphibolite), with a minor addition of mantle-derived components (magma mixing). Combined with petrogeochemical discriminant diagrams (e.g., Sr/Y vs. Y, Rb vs. Yb + Ta) and the regional geological context, this granodiorite is interpreted to have formed in an active continental margin tectonic setting associated with the eastward subduction of the Paleo-Tethys Ocean (represented by the Changning-Menglian Ocean). This discovery fills the gap in the record of Early Permian subduction-related magmatic rocks in the northern segment of the Changning-Menglian suture zone. It provides crucial petrological evidence constraining that the eastward subduction and consumption of the northern Paleo-Tethys Ocean had already commenced by the Early Permian. Full article

(This article belongs to the Special Issue Granitoids and Their Importance in the Identification of Tectonic Environments, Geodynamic Evolution and Crustal Growth: Mineralizations, Geochronology, Elemental and Isotope Geochemistry)

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17 pages, 3187 KiB

Open AccessArticle

Tectonic Uplift and Hydrocarbon Generation Constraints from Low-Temperature Thermochronology in the Yindongzi Area, Ordos Basin

by Guangyuan Xing, Zhanli Ren, Kai Qi, Liyong Fan, Junping Cui, Jinbu Li, Zhuo Han and Sasa Guo

Minerals 2025, 15(9), 893; https://doi.org/10.3390/min15090893 - 22 Aug 2025

Abstract

This study investigates the uplift and exhumation history of the southern segment of the western margin of the Ordos Basin using low-temperature thermochronology, including zircon (U-Th)/He (ZHe), apatite fission-track (AFT), and apatite (U-Th)/He (AHe) data, combined with thermal history modeling. The study area [...] Read more.

This study investigates the uplift and exhumation history of the southern segment of the western margin of the Ordos Basin using low-temperature thermochronology, including zircon (U-Th)/He (ZHe), apatite fission-track (AFT), and apatite (U-Th)/He (AHe) data, combined with thermal history modeling. The study area exhibits a complex structural framework shaped by multiple deformation events, leading to the formation of extensively developed fault systems. Such faulting can adversely affect hydrocarbon preservation. To better constrain the timing of fault reactivation in this area, we carried out an integrated study involving low-temperature thermochronology and burial history modeling. The results reveal a complex, multi-phase thermal-tectonic evolution since the Late Paleozoic. The ZHe ages (291–410 Ma) indicate deep burial and heating related to Late Devonian–Early Permian tectonism and basin sedimentation, reflecting early orogenic activity along the western North China Craton. During the Late Jurassic to Early Cretaceous (165–120 Ma), the study area experienced widespread and differential uplift and cooling, controlled by the Yanshanian Orogeny. Samples on the western side of the fault show earlier and more rapid cooling than those on the eastern side, suggesting a fault-controlled, basinward-propagating exhumation pattern. The cooling period indicated by AHe data and thermal models reflects the Cenozoic uplift, likely induced by far-field compression from the rising northeastern Tibetan Plateau. These findings emphasize the critical role of inherited faults not only as thermal-tectonic boundaries during the Mesozoic but also as a pathway for hydrocarbon migration. Meanwhile, thermal history models based on borehole data further reveal that the study area underwent prolonged burial and heating during the Mesozoic, reaching peak temperatures for hydrocarbon generation in the Late Jurassic. The timing of major cooling events corresponds to the main stages of hydrocarbon expulsion and migration. In particular, the differential uplift since the Mesozoic created structural traps and migration pathways that likely facilitated hydrocarbon accumulation along the western fault zones. The spatial and temporal differences among the samples underscore the structural segmentation and dynamic response of the continental interior to both regional and far-field tectonic forces, while also providing crucial constraints on the petroleum system evolution in this tectonically complex region. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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3 pages, 132 KiB

Open AccessEditorial

Editorial for Special Issue “Metallogenesis of the Central Asian Orogenic Belt”

by Xiaoyong Yang and Wenhua Ji

Minerals 2025, 15(9), 892; https://doi.org/10.3390/min15090892 - 22 Aug 2025

Abstract

The Central Asian Orogenic Belt (CAOB), or Altaid orogenic collage, is one of the largest Neoproterozoic to Early Mesozoic accretionary orogenic belts on Earth [...] Full article

(This article belongs to the Special Issue Metallogenesis of the Central Asian Orogenic Belt)

18 pages, 961 KiB

Open AccessReview

Blending Characterization for Effective Management in Mining Operations

by Matias Saavedra, Nathalie Risso, Moe Momayez, Ricardo Nunes, Victor Tenorio and Jinhong Zhang

Minerals 2025, 15(9), 891; https://doi.org/10.3390/min15090891 - 22 Aug 2025

Abstract

Ore blending plays a critical role in ensuring feed consistency and optimizing downstream processes in the mining industry. Despite its importance, effective blending remains challenging due to ore variability and operational constraints. This review focuses exclusively on modern, data-driven blending methodologies, with particular [...] Read more.

Ore blending plays a critical role in ensuring feed consistency and optimizing downstream processes in the mining industry. Despite its importance, effective blending remains challenging due to ore variability and operational constraints. This review focuses exclusively on modern, data-driven blending methodologies, with particular emphasis on the application of data science and machine learning (ML) in predicting key process variables and supporting real-time decision-making. It discusses core challenges such as data quality, feature engineering, and model generalization, alongside enabling technologies including sensor integration, automation platforms, and real-time data acquisition systems. By consolidating the recent literature and highlighting emerging trends, this work outlines future directions for advancing intelligent blending systems and underscores the importance of standardized, high-quality data in the development of robust digital solutions for mineral processing. Full article

(This article belongs to the Special Issue Application of Machine Learning in Mining, Mineral Processing and Extractive Metallurgy)

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33 pages, 8250 KiB

Open AccessArticle

Fluid Components in Cordierites from Granulite- and Amphibolite-Facies Rocks of the Aldan Shield and Yenisei Ridge, Russia: Evidence from Pyrolysis-Free GC-MS, Raman, and IR Spectroscopy

by Ksenia Zatolokina, Anatoly Tomilenko, Taras Bul’bak and Nikolay Popov

Minerals 2025, 15(9), 890; https://doi.org/10.3390/min15090890 - 22 Aug 2025

Abstract

This study provides the first comprehensive characterization of fluid components in cordierites from both moderate- to high-pressure granulite facies of the Aldan Shield (Sutam and Nimnyr blocks), and granulite–amphibolite facies of the Yenisei Ridge (Kan and Yenisei series of the Angara–Kan complex), Russia, [...] Read more.

This study provides the first comprehensive characterization of fluid components in cordierites from both moderate- to high-pressure granulite facies of the Aldan Shield (Sutam and Nimnyr blocks), and granulite–amphibolite facies of the Yenisei Ridge (Kan and Yenisei series of the Angara–Kan complex), Russia, using integrated infrared and Raman spectroscopy coupled with pyrolysis-free gas chromatography–mass spectrometry (GC-MS). Granulite-facies cordierites record CO₂-dominated fluids (X_CO2 = CO₂/(H₂O + CO₂) = 0.74–0.99) with elevated values (X_CO2 = 0.89–0.99) in high-pressure, high-temperature (high-P-T) samples from the Sutam block and Kan series compared to moderate-P-T samples from the Nimnyr block (X_CO2 = 0.74–0.84). Amphibolite-facies cordierites (Yenisei series) show significantly lower CO₂ contents (X_CO2 = 0.51–0.57) and higher H₂O concentrations relative to high-pressure granulites. Critically, we report the first identification in cordierites of at least 12 homologous series of organic compounds and nitrogenated, sulfonated, and halogenated compounds. These results provide new constraints on fluid behavior across metamorphic facies transitions. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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18 pages, 3300 KiB

Open AccessArticle

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

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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30 pages, 12874 KiB

Open AccessArticle

Reservoir Properties of Lacustrine Deep-Water Gravity Flow Deposits in the Late Triassic–Early Jurassic Anyao Formation, Paleo-Ordos Basin, China

by Zhen He, Minfang Yang, Lei Wang, Lusheng Yin, Peixin Zhang, Kai Zhou, Peter Turner, Zhangxing Chen, Longyi Shao and Jing Lu

Minerals 2025, 15(9), 888; https://doi.org/10.3390/min15090888 - 22 Aug 2025

Abstract

The development of gravity flow sedimentology has improved our understanding of the physical properties of different types of gravity flow deposits, especially the advancement of various gravity flow models. Although studies of gravity flows have developed greatly, the linkage between different sub-facies and [...] Read more.

The development of gravity flow sedimentology has improved our understanding of the physical properties of different types of gravity flow deposits, especially the advancement of various gravity flow models. Although studies of gravity flows have developed greatly, the linkage between different sub-facies and their reservoir properties is hindered by a lack of detailed sedimentary records. Here, integrated test data (including thin-section petrology, high-pressure mercury injection experiments, capillary pressure curve analysis, and scanning electron microscopy) are used to evaluate links between different types of gravity flows and their reservoir properties from the Late Triassic–Early Jurassic Anyao Formation, southeastern Paleo-Ordos Basin, China. The petrological and sedimentological data reveal two types of deep-water gravity flow deposits comprising sandy debris flow (SDF) and turbidity current (TC) deposits. Both are fine-grained lithic sandstones and form low-porosity and ultra-low permeability reservoirs. Secondary porosity, formed by the dissolution of framework grains, including feldspars and lithic fragments, dominates the pore types. This secondary porosity is widely developed in the Anyao Formation and formed by reaction with organic acids during burial (early mesodiagenesis). The associated mud rocks have reached the early mature stage of the oil window with Tmax of 442–448 °C. Compared with the turbidites, the sandy debris flows have higher framework grain content (87.9 vs. 84.8%), framework grain size (0.091 vs. 0.008 mm), porosity (6.97 vs. 3.44%), pore throat radius (0.102 vs. 0.025 μm), and permeability (0.025 vs. 0.005 mD) but are relatively poor in the sorting of framework grains and pore throat radii. The most important petrological factors affecting porosity and permeability of the SDF reservoirs are framework grain size and feldspar grain content, respectively, but those of the TC reservoirs are feldspar grain content and the maximum pore throat radius. Diagenetic dissolution of framework grains is the most important porosity-affecting factor for both SDF and TC reservoirs. Our multi-proxy study provides new insights into the links between gravity flow sub-facies and reservoir properties in the lacustrine deep-water environment. Full article

(This article belongs to the Section Mineral Exploration Methods and Applications)

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42 pages, 15245 KiB

Open AccessArticle

Effect of Mixing Water Temperature on the Thermal and Microstructural Evolution of Cemented Paste Backfill in Underground Mining

by Amin Safari, Cody Tennant, Aliakbar Gholampour, Jeremy Palmer and Abbas Taheri

Minerals 2025, 15(9), 887; https://doi.org/10.3390/min15090887 - 22 Aug 2025

Abstract

Cemented paste backfill (CPB) gains strength through the hydration of the binder constituent of the CPB, where mix temperature is a key influencing factor. Both rate of strength development and ultimate strength are influenced by the overarching temperature conditions in which the binder [...] Read more.

Cemented paste backfill (CPB) gains strength through the hydration of the binder constituent of the CPB, where mix temperature is a key influencing factor. Both rate of strength development and ultimate strength are influenced by the overarching temperature conditions in which the binder hydration occurs. This study investigates the influence of mixing water temperature on the thermal behaviour, hydration kinetics, and microstructural development of CPB using a combination of thermal finite element modelling, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Five CPB mixtures were prepared, with water temperatures ranging from 5 °C to 50 °C, and tested under controlled conditions to isolate the effects of the initial thermal input. Results show that moderate mixing water temperatures (20–35 °C) optimize hydration and mechanical strength, while excessive temperatures (≥50 °C) increase the risk of thermal cracking due to generation of excessive heat. The thermal modelling results demonstrated that the highest temperatures were observed in the bottom section of the fill mass, in contact with the surrounding rock, where the combined effects of mix-generated heat and rock conduction were most pronounced. The 50 °C mix reached a peak internal temperature of 85.6 °C with a thermal gradient of 40.5 °C, while the 5 °C mix recorded a much lower peak of 55.7 °C and a gradient of 16.8 °C. These results highlight that higher mixing water temperatures accelerate early hydration reactions and significantly influence the internal thermal profile during the first 21 days of curing. Based on these findings, the design of paste plants can be improved by incorporating a heating/cooling system for the mixing water tank—firstly, to ensure the water temperature does not exceed 50 °C and secondly, to maintain water within an optimal temperature range, potentially reducing binder consumption. Full article

(This article belongs to the Special Issue Rheological, Mechanical and Hydration Properties of Cemented Paste Backfill)

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23 pages, 12646 KiB

Open AccessArticle

Titanite Textures, U-Pb Dating, Chemistry, and In Situ Nd Isotopes of the Lalingzaohuo Mafic Magmatic Enclaves and Host Granodiorites in the East Kunlun Orogen Belt: Insights into Magma Mixing Processes

by Zisong Zhao, Bingzhang Wang, Shengwei Wu and Jiqing Li

Minerals 2025, 15(9), 886; https://doi.org/10.3390/min15090886 - 22 Aug 2025

Abstract

Widespread Triassic granitic magmatism is archived in the East Kunlun Orogen Belt (EKOB) of Northern Qinghai–Tibet Plateau. Mafic magmatic enclaves (MMEs), commonly hosted in these plutons, are generally interpreted as products of magma mixing; however, the specific magmatic processes remain poorly understood. In [...] Read more.

Widespread Triassic granitic magmatism is archived in the East Kunlun Orogen Belt (EKOB) of Northern Qinghai–Tibet Plateau. Mafic magmatic enclaves (MMEs), commonly hosted in these plutons, are generally interpreted as products of magma mixing; however, the specific magmatic processes remain poorly understood. In this study, we present new data on the complex zoning patterns, in situ U–Pb ages, trace element compositions, and Nd isotopic characteristics of titanite grains from the MMEs and host granodiorite of Laningzaohuo Zhongyou pluton. Whole-rock geochemical data indicate that the pluton is composed of volcanic arc-related, calc-alkaline, metaluminous I-type granodiorite. Titanite in the MMEs and the granodiorite yield similar U–Pb ages of ~244 Ma but display distinct textural and compositional features. Titanite from the granodiorite is typically euhedral, characterized by magmatic core and mantle with deuteric rim, and exhibits sector and fir-tree zoning in the core. In contrast, titanite from the MMEs is generally anhedral, also showing magmatic core and mantle as well as deuteric rims, but exhibits oscillatory zoning and incomplete sector and fir-tree zoning in the core. Titanite cores in the MMEs have ε_Nd(t) ranging from −2.5 to −3.4, comparable to those of the coeval gabbro and MMEs elsewhere in the EKOB. These cores also show higher LREE/HREE ratios compared to titanite cores in the granodiorite, suggesting crystallization from mixed magmas with greater contributions from enriched lithospheric mantle sources. Titanite mantles in the MMEs yield ε_Nd(t) of −4.0 to −4.8, slightly lower than the cores in the MMEs but higher than those of titanite cores and mantles in the granodiorite (−4.6 to −5.5). The mantle can be interpreted as crystallized from mixed magmas with less mafic components. Titanite rims in the MMEs have ε_Nd(t) of −5.0 to −5.7, identical to those in the granodiorite, and have REE concentrations and Th/U and Nb/Ta ratios consistent with the titanite rims in the granodiorite, clearly indicative of crystallization from evolved, hydrated, granodioritic magmas. Plagioclase in the MMEs exhibits disequilibrium textures such as sieve texture and reverse zoning, with An_36–66, contrasting with the more uniform An contents (An_35–37) in the granodiorite. This suggests that plagioclase in the MMEs crystallized in an environment influenced by both mafic and felsic magmas. Amphibole thermobarometry indicates that amphibole in the MMEs crystallized at ~788 °C and ~295 MPa, slightly higher than the crystallization conditions in the granodiorite (~778 °C and ~259 MPa). We thus propose that the chemical and textural differences between titanite in the MMEs and granodiorite suggest that the MMEs formed within a mushy hybrid layer generated by injection of upwelling basaltic magma into a pre-existing granitic magma chamber. Titanite cores and mantles in the MMEs likely crystallized from variably mixed magmas. They subsequently underwent resorption and disequilibrium growth within the hybrid layer, and were eventually overgrown by rims formed from evolved interstitial granitic melts within the mushy enclaves. These findings demonstrate that the complex zoning and geochemical titanite in the MMEs provide valuable insights into magma mixing processes. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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29 pages, 28833 KiB

Open AccessArticle

Mineralization Styles in the Orogenic (Quartz Vein) Gold Deposits of the Eastern Kazakhstan Gold Belt: Implications for Regional Prospecting

by Dmitry L. Konopelko, Valeriia S. Zhdanova, Sergei Y. Stepanov, Ekaterina S. Sidorova, Sergei V. Petrov, Aleksandr K. Kozin, Emil S. Aliyev, Vasiliy A. Saltanov, Mikhail A. Kalinin, Andrey V. Korneev and Reimar Seltmann

Minerals 2025, 15(8), 885; https://doi.org/10.3390/min15080885 - 21 Aug 2025

Abstract

The Eastern Kazakhstan Gold Belt is a major black-shale-hosted gold province in Central Asia where the main types of deposits comprise mineralized zones with auriferous sulfides (micro- and nano-inclusions of gold and refractory gold) and quartz veins with visible gold. The quartz vein [...] Read more.

The Eastern Kazakhstan Gold Belt is a major black-shale-hosted gold province in Central Asia where the main types of deposits comprise mineralized zones with auriferous sulfides (micro- and nano-inclusions of gold and refractory gold) and quartz veins with visible gold. The quartz vein deposits are economically less important but may potentially represent the upper parts of bigger ore systems concealed at depth. In this work, the mineralogy of the quartz vein deposits and related wall rock alteration zones was studied using microscopy and SEM-EDS analysis, and the geochemical dispersion of the ore elements in primary alteration haloes was documented utilizing spatial distribution maps and statistical treatment methods. The studied auriferous quartz veins are classified as epizonal black-shale-hosted orogenic gold deposits. The veins generally have linear shapes with an average width of ca. 1 m and length up to 150 m and contain high-grade native gold with minor amounts of sulfides. In supergene oxidation zones, the native gold is closely associated with Fe-hydroxide minerals cementing brecciated zones within the veins. The auriferous quartz veins are usually enclosed by the wall rock alteration envelopes, where two types of alteration are distinguished. Proximal phyllic alteration (sericite-albite-pyrite ± chlorite, Fe-Mg-Ca carbonates, arsenopyrite, and pyrrhotite) develops as localized alteration envelopes, and pervasive carbonation accompanied by chlorite ± sericite and albite is the dominant process in the distal alteration zones. The rocks within the alteration zones are enriched in Au and chalcophile elements, and three groups of chemical elements showing significant positive mutual correlation have been identified: (1) an early geochemical assemblage includes V, P, and Co (±Ni), which are the chemical elements characteristic for black shale formations, (2) association of Au, As, and other chalcophile elements is distinctly overprinting, and manifests the main stage of sulfide-hosted Au mineralization, and (3) association of Bi and Hg (±Sb and U) includes the chemical elements that are mobile at low temperatures, and can be explained by activity of the late-stage hydrothermal or supergene fluids. The chalcophile elements show negative slopes from proximal to distal alteration zones and form overlapping positive anomalies on spatial distribution mono-elemental maps. Thus, the geochemical methods can provide useful tools to delineate the ore elemental associations and to outline reproducible anomalies for subsequent regional gold prospecting. Full article

(This article belongs to the Special Issue Structure and Origin of Gold Mineralization: From Primary to Placer Gold Deposits)

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20 pages, 3784 KiB

Open AccessArticle

Mineralogical Characterization and Provenance of Black Sand in the Xiahenan Area, Tarim Large Igneous Province

by Songqiu Zhang, Renyu Zeng, Shigang Duan, Jiayong Pan, Dong Liang, Jie Yan, Jianjun Wan, Qing Liu and You Zhang

Minerals 2025, 15(8), 884; https://doi.org/10.3390/min15080884 - 21 Aug 2025

Abstract

The Tarim Large Igneous Province (TLIP) in NW China hosts abundant Fe–Ti–V oxide deposits associated with mafic–ultramafic intrusions. In the Xiahenan area, on the western margin of the TLIP, a distinct magnetic anomaly is linked to widespread surface accumulations of black sand. However, [...] Read more.

The Tarim Large Igneous Province (TLIP) in NW China hosts abundant Fe–Ti–V oxide deposits associated with mafic–ultramafic intrusions. In the Xiahenan area, on the western margin of the TLIP, a distinct magnetic anomaly is linked to widespread surface accumulations of black sand. However, the genesis and origin of these black sand grains remain unclear. Based on mineral assemblages, this study classifies the grains of the black sand into three types: (i) plagioclase (An_10–90)–ilmenite–olivine–magnetite assemblage (Sand I), (ii) plagioclase (An_0–10)-fine-grained magnetite assemblage (Sand II), and (iii) hornblende–magnetite highly complex assemblage (Sand III). Mineral geochemical studies demonstrate that magnetite in Sand I and Sand II is of magmatic origin, with protolith being basaltic magma. Magnetite in Sand III was eroded from veins formed by hydrothermal processes at 300–500 °C. Ilmenite in Sand I contains a high FeTiO₃ component, representing basaltic ilmenite. Olivine in Sand I has a low Fo content (43.86–47.27), belonging to hortonolite olivine. Research indicates that Sand I and Sand II share similar mineral assemblages and mineral geochemical characteristics with basalts in the Xiahenan area, suggesting they are weathering products of Xiahenan basalts or their cognate magmas. In contrast, the veined magnetite of Sand III formed during post-magmatic hydrothermal events. Full article

(This article belongs to the Special Issue Mineralization and Metallogeny of Iron Deposits)

18 pages, 2307 KiB

Open AccessArticle

Technological Properties Contrast of Galena, Sphalerite, Carbonaceous Material and Choice of Flotation Technology

by Akim Yergeshev, Rustam Tokpayev, Marina Karmeeva, Tamina Khavaza, Nazymarzu Yergesheva, Azhar Atchabarova, Mikhail Nauryzbayev and Vladislava Ignatkina

Minerals 2025, 15(8), 883; https://doi.org/10.3390/min15080883 - 21 Aug 2025

Abstract

The presence of galena, sphalerite (cleiophane), and Carbonaceous Material (CM) in sulphide ore complicates the application of a direct-differential flotation flowsheet due to increased mutual interactions between both marketable concentrates and final tailings. Flotation tests, measurements of electrokinetic (zeta) potential, adsorption of sulphydric [...] Read more.

The presence of galena, sphalerite (cleiophane), and Carbonaceous Material (CM) in sulphide ore complicates the application of a direct-differential flotation flowsheet due to increased mutual interactions between both marketable concentrates and final tailings. Flotation tests, measurements of electrokinetic (zeta) potential, adsorption of sulphydric collectors, and colorimetric indicators were employed to elucidate the cause-and-effect relationships underlying the reduction in contrast of the flotation properties of galena and cleiophane surfaces. It was established that galena and cleiophane exhibit comparable flotation responses when using diesel oil within a pH range of 6–8. While high galena recovery is anticipated, the similar recovery of cleiophane is attributed to the ZnS zeta potential approaching zero in this pH interval. Experimental results demonstrated a distinct difference in the flotation behavior of galena and cleiophane, both with natural surface oxidation and following the removal of sulphoxy films. The application of Carbonaceous Material depressants derived from wood processing by-products (lignin-sulphonates) resulted in a significant decrease in sphalerite recovery. Although the flotation rate constant for Carbonaceous Material in the presence of lignin-sulphonate-based depressants decreases, the overall recovery to concentrate increases over time. The implementation of a bulk-differential flowsheet, involving the preliminary removal of CM prior to the bulk Pb-Zn flotation of lead-zinc sulphide ore, has been demonstrated to be effective. Full article

(This article belongs to the Special Issue Mineral Processing and Recycling Technologies for Sustainable Future)

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35 pages, 10915 KiB

Open AccessReview

Geochemistry of Mars with Laser-Induced Breakdown Spectroscopy (LIBS): ChemCam, SuperCam, and MarSCoDe

by Roger C. Wiens, Agnes Cousin, Samuel M. Clegg, Olivier Gasnault, Zhaopeng Chen, Sylvestre Maurice and Rong Shu

Minerals 2025, 15(8), 882; https://doi.org/10.3390/min15080882 - 21 Aug 2025

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been used to explore the chemistry of three regions of Mars on respective missions by NASA and CNSA, with CNES contributions. All three LIBS instruments use ~100 mm diameter telescopes projecting pulsed infrared laser beams of 10–14 mJ [...] Read more.

Laser-induced breakdown spectroscopy (LIBS) has been used to explore the chemistry of three regions of Mars on respective missions by NASA and CNSA, with CNES contributions. All three LIBS instruments use ~100 mm diameter telescopes projecting pulsed infrared laser beams of 10–14 mJ to enable LIBS at 2–10 m distances, eliminating the need to position the rover and instrument directly onto targets. Over 1.3 million LIBS spectra have been used to provide routine compositions for eight major elements and several minor and trace elements on >3000 targets on Mars. Onboard calibration targets common to all three instruments allow careful intercomparison of results. Operating over thirteen years, ChemCam on Curiosity has explored lacustrine sediments and diagenetic features in Gale crater, which was a long-lasting (>1 My) lake during Mars’ Hesperian period. SuperCam on Perseverance is exploring the ultramafic igneous floor, fluvial–deltaic features, and the rim of Jezero crater. MarSCoDe on the Zhurong rover investigated for one year the local blocks, soils, and transverse aeolian ridges of Utopia Planitia. The pioneering work of these three stand-off LIBS instruments paves the way for future space exploration with LIBS, where advantages of light-element (H, C, N, O) quantification can be used on icy regions. Full article

(This article belongs to the Special Issue Understanding Geological Processes through Laser-Induced Breakdown Spectroscopy Analysis)

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22 pages, 2291 KiB

Open AccessArticle

Heavy Metal Pollution Assessment and Survey of Rhizosphere Bacterial Communities from Saccharum spontaneum L. in a Rehabilitated Nickel-Laterite Mine in the Philippines

by Shiela W. Mainit, Carlito Baltazar Tabelin, Florifern C. Paglinawan, Jaime Q. Guihawan, Alissa Jane S. Mondejar, Vannie Joy T. Resabal, Maria Reina Suzette B. Madamba, Dennis Alonzo, Aileen H. Orbecido, Michael Angelo Promentilla, Joshua B. Zoleta, Dayle Tranz Daño, Ilhwan Park, Mayumi Ito, Takahiko Arima, Theerayut Phengsaart and Mylah Villacorte-Tabelin

Minerals 2025, 15(8), 881; https://doi.org/10.3390/min15080881 - 21 Aug 2025

Abstract

In this study, we assessed soil pollutants and surveyed the bacterial communities using 16S rRNA sequencing to better understand how to improve rehabilitation strategies for nickel-laterite mines in the Philippines. Representative soil samples and rhizospheres from Saccharum spontaneum L. in three post-mining sites [...] Read more.

In this study, we assessed soil pollutants and surveyed the bacterial communities using 16S rRNA sequencing to better understand how to improve rehabilitation strategies for nickel-laterite mines in the Philippines. Representative soil samples and rhizospheres from Saccharum spontaneum L. in three post-mining sites rehabilitated in 2015, 2017, and 2019 were collected and analyzed. X-ray diffraction (XRD) identified iron oxyhydroxides, silicates, and clays as major soil components. Based on the pollution load index and contamination degree, the 2015A and 2015B sites were classified as “pristine” and had a “low degree of pollution”, while the remaining sites (2017A, 2017B, 2019A, and 2019B) were considered “moderately contaminated” with nickel, chromium, cobalt, lead, zinc, and copper. An analysis of the bacterial community composition revealed that the phyla Proteobacteria and Actinobacteria, along with the genus Ralstonia, were the most abundant groups across both control and rehabilitated sites. Our results showed that the soil pH and organic matter contents were strongly linked to specific bacterial community composition. These taxa have potential for inoculation in nickel-laterite soils to promote the growth of hyperaccumulator plants. Our results also showed a significant correlation between the structure of the bacterial communities and nickel, chromium, and manganese soil contents, but not with rehabilitation time. Furthermore, we identified the genera Diaphorobacter as potential bioindicators because they are sensitive to nickel and chromium. This study provides valuable baseline data on heavy metal pollution and microbial diversity in a rehabilitated Ni-laterite mine site. Full article

(This article belongs to the Special Issue Sustainable Mining: Advancements, Challenges and Future Directions)

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16 pages, 5670 KiB

Open AccessArticle

Experimental Investigation on Spontaneous Combustion Characteristics of Sulfide Ores with Different Sulfur Content

by Qisong Huang, Bo Xu, Junjun Feng, Yugen Lu, Xiangyu Wang and Qinglang Liu

Minerals 2025, 15(8), 880; https://doi.org/10.3390/min15080880 - 21 Aug 2025

Abstract

The spontaneous combustion of sulfide ores (SOSC) is an extremely dangerous mining disaster that directly threatens safety production in mines and causes far-reaching negative impacts on the surrounding ecosystem. In this study, oxidation weight gain experiments, self-heating temperature and ignition temperature tests, and [...] Read more.

The spontaneous combustion of sulfide ores (SOSC) is an extremely dangerous mining disaster that directly threatens safety production in mines and causes far-reaching negative impacts on the surrounding ecosystem. In this study, oxidation weight gain experiments, self-heating temperature and ignition temperature tests, and thermogravimetric analysis (TGA) were conducted to detect the spontaneous combustion characteristics of sulfide ores with different sulfur contents (40.29%, 34.56%, 24.81%, and 14.2%). The results show that the sulfur content significantly affects the spontaneous combustion characteristics of sulfide ores. As the sulfur content decreased, the oxidized weight gain rate decreased overall, and the self-heating temperature (135, 152.5, 162.5, and 176.9 °C) and ignition temperature (425.3, 438.6, 455.4, and >500 °C) increased. The three combustion stages of the SOSC were divided based on the TG and DTG curves: low-temperature oxidation stage, combustion decomposition stage, and slow burnout stage. Furthermore, KAS and FWO methods were used to obtain the apparent activation energy in the combustion decomposition stage. The apparent activation energy decreased significantly with the increase in the sulfur content. The results of all experiments and analyses showed that sulfide ores with high sulfur content have a stronger tendency to undergo spontaneous combustion. The research results have important theoretical and practical implications for the prevention of SOSC. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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16 pages, 7939 KiB

Open AccessArticle

Assessment of the Valorization Potential of Municipal Sewage Treatment Plant (STP) Sludge to Produce Red-Firing Wall Tiles

by Isabela Oliveira Rangel Areias, Felipe Sardinha Maciel and José Nilson França Holanda

Minerals 2025, 15(8), 879; https://doi.org/10.3390/min15080879 - 21 Aug 2025

Abstract

Municipal sewage treatment plants generate significant amounts of polluting sludge, which demands innovative valorization approaches to support its sustainable recycling. This work aimed to evaluate the valorization potential of sludge from a municipal sewage treatment plant (STP) as an alternative raw material to [...] Read more.

Municipal sewage treatment plants generate significant amounts of polluting sludge, which demands innovative valorization approaches to support its sustainable recycling. This work aimed to evaluate the valorization potential of sludge from a municipal sewage treatment plant (STP) as an alternative raw material to traditional limestone in red wall tile formulations. For this purpose, four red wall tile formulations were performed with 0%, 5%, 10%, and 15% weight of STP sludge replacing traditional limestone. The tile formulations prepared by the dry process were characterized to determine their chemical and mineral compositions, thermal analysis, and sintering behavior. The red wall tile pieces were manufactured by pressing and firing at temperatures ranging from 1150 °C to 1180 °C. The effects of STP sludge incorporation and firing temperature on the densification behavior and technological properties were investigated. The results indicated that the STP sludge exhibited good chemical compatibility for use in red wall tile formulations. Water absorption values varied between 16.52% and 19.70%, indicating compliance with the red wall tile production (BIII group). These findings demonstrate the valorization potential of STP sludge in red wall tiles, which offers a relevant recycling option for the sanitation sector and the circular economy. Full article

(This article belongs to the Special Issue From Clay Minerals to Ceramics: Progress and Challenges)

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