Minerals

27 pages, 22432 KiB

Open AccessArticle

The B-Zone 4611 Silver-Rich Pod—An Unusual Ag-Ge-Sb-As-Ni Assemblage Within the Irish-Type Zn-Pb Silvermines Deposit, County Tipperary, Ireland

by Colin J. Andrew and John H. Ashton

Minerals 2025, 15(5), 540; https://doi.org/10.3390/min15050540 - 19 May 2025

Abstract

The Silvermines Pb-Zn-Ag-Ba orebodies comprise vein, replacement, cross-cutting and stratiform mineralization mostly hosted in Lower Carboniferous limestones in the vicinity of a major ENE and E-W trending normal fault array and represent a classic example of Irish-Type Zn-Pb mineralization. Historically the deposits have [...] Read more.

The Silvermines Pb-Zn-Ag-Ba orebodies comprise vein, replacement, cross-cutting and stratiform mineralization mostly hosted in Lower Carboniferous limestones in the vicinity of a major ENE and E-W trending normal fault array and represent a classic example of Irish-Type Zn-Pb mineralization. Historically the deposits have been exploited at various times, but the major limestone-hosted Zn-Pb-Ba mineralization was not discovered until the 1960s. Structurally controlled crosscutting vein and breccia mineralization represent pathways of hydrothermal fluids escaping from the Silvermines fault at depth that exhaled and replaced shallowly buried Waulsortian limestones creating the larger stratiform orebodies such as the Upper G and B-Zones. The B-Zone, comprising a pre-mining resource of 4.64 Mt of 4.53% Zn, 3.58% Pb, 30 g/t Ag has a locally highly variable host mineralogy dominated by pyrite, barite, siderite, within dolomitic and limestone breccias with local silica-haematite alteration. A small, highly unusual pod of very high-grade Ag-rich mineralization in the B-Zone, the 4611 Pod, discovered in 1978, has not been previously documented. Unpublished records, field notes, and mineralogical and chemical data from consultant reports have been assimilated to document this interesting and unusual occurrence. The pod, representing an irregular lens of mineralization ca 2 m thick and representing 500 t, occurs within the B-Zone orebody and comprises high grade Zn and Pb sulfides with significant patches of proustite-pyrargyrite (ruby silvers) and a host of associated Pb, Ag, Sb, As, Cu, Ge sulfide minerals, including significant argyrodite. Although evidence of any distinct feeder below the pod is lacking, the nature of the pod, its unusual mineralogy and its paragenesis suggests that it represents a small, possibly late source of exotic hydrothermal fluid where it entered the B-Zone stratiform mineralizing system. Full article

(This article belongs to the Special Issue Genesis and Evolution of Pb-Zn-Ag Polymetallic Deposits: 2nd Edition)

23 pages, 22456 KiB

Open AccessArticle

Thermal Maturity of the Silurian “Hot” Shales and Correlation with the Present Geothermal Variations in West Lithuania, Baltic Basin

by Saulius Šliaupa, Jurga Lazauskienė and Rasa Šliaupienė

Minerals 2025, 15(5), 539; https://doi.org/10.3390/min15050539 - 19 May 2025

Abstract

The most organic-rich shales are defined in the Dobele Fm. of the Aeronian Stage of about 10 m thick in west Lithuania. This particular layer is documented in the whole Baltic Basin. Compatible shales are widely distributed in other basins referred to as [...] Read more.

The most organic-rich shales are defined in the Dobele Fm. of the Aeronian Stage of about 10 m thick in west Lithuania. This particular layer is documented in the whole Baltic Basin. Compatible shales are widely distributed in other basins referred to as similar Silurian “hot” shales. The average TOC was estimated at 6.67 wt.% (good and excellent source rock). The thermal maturity of shales was evaluated through organic geochemical techniques, including TOC determination, Rock–Eval pyrolysis, and organic petrography studies. The thermal maturity varies from T_max = 431 °C and eq.VR_o = 0.65% (early oil) to T_max = 468 °C and VR_o = 1.38% (locally up to 1.94%) (late oil and wet to dry gas generation). It is notable, most of the study area is confined to regional-scale West Lithuanian Geothermal Anomaly. Most of the geothermal features, both palaeo- and recent, recorded in lateral variation in thermal maturity of shales unravel persistence of heat flow. Locally, the Variscan tectonic activity was imprinted in thermal maturity of organic matter-rich shales (Žemaičių Naumiestis anomaly). Full article

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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31 pages, 4699 KiB

Open AccessReview

The Utilization of Slag, Steel Slag, and Desulfurization Gypsum as Binder Systems in UHPC with Iron Tailings and Steel Fibers—A Review

by Hocine Heraiz, Jiajie Li, Ziping Pan, Dongdong Zhang, Yingxi Hu, Xinli Mu, Amer Baras, Jinhai Liu, Wen Ni and Michael Hitch

Minerals 2025, 15(5), 538; https://doi.org/10.3390/min15050538 - 18 May 2025

Abstract

Ultra-high-performance concrete (UHPC) is known for its outstanding strength and durability but is often limited by the high cost of traditional materials, like cement, fine aggregates, and silica fume. This review examines the use of industrial by-products—specifically, iron tailings, steel slag, and desulfurization [...] Read more.

Ultra-high-performance concrete (UHPC) is known for its outstanding strength and durability but is often limited by the high cost of traditional materials, like cement, fine aggregates, and silica fume. This review examines the use of industrial by-products—specifically, iron tailings, steel slag, and desulfurization gypsum—as sustainable alternatives in UHPC mix design. These materials serve as supplementary cementitious components and fine aggregates, helping reduce environmental impacts and production costs. This study highlights the synergistic hydration mechanisms between Portland cement and waste-based materials, leading to improved microstructure and long-term strength. The role of steel fibers in enhancing crack resistance is also discussed. Challenges related to workability, cost, and lack of standardization are addressed, along with opportunities for innovative mix designs, low-carbon binders, and 3D printing. Overall, this paper underscores the potential of industrial by-products to advance sustainable, high-performance UHPC solutions. Full article

(This article belongs to the Special Issue Recycling of Industrial Waste for the Development of Sustainable Materials)

13 pages, 936 KiB

Open AccessArticle

Zircon Systematics of the Shionomisaki Volcano–Plutonic Complex (Kii Peninsula, Japan): A Potential Tool for the Study of the Source Region of Silicic Magmas

by Ulrich Knittel, Monika Walia and Shigeyuki Suzuki

Minerals 2025, 15(5), 537; https://doi.org/10.3390/min15050537 - 18 May 2025

Abstract

The Shionomisaki Igneous Complex is part of the Mid Miocene igneous province developed within the Shimanto Accretionary Complex in front of the volcanic front in SW Japan. The igneous rocks in this province mostly have silicic compositions. New U-Pb ages obtained for two [...] Read more.

The Shionomisaki Igneous Complex is part of the Mid Miocene igneous province developed within the Shimanto Accretionary Complex in front of the volcanic front in SW Japan. The igneous rocks in this province mostly have silicic compositions. New U-Pb ages obtained for two samples from the Shionomisaki Complex at the southern tip of the Kii Peninsula (14.6 ± 0.4 Ma and 14.9 ± 0.4 Ma) fall into the range of previous age determinations (14.6 ± 0.2 to 15.4 ± 0.3 Ma). Hf isotopic compositions obtained for co-magmatic zircon (εHf(t) = −0.7 to +4.8) lie between typical values obtained for mantle-derived magmas and values obtained for old crustal rocks. They are thus consistent with previous interpretations that the magmas are mixtures of mantle and crustally derived magmas. In the modelling of the isotopic characteristics of the magmas, the sediments of the Shimanto belt are taken as the protolith of the silicic magmas. Xenocrystal zircon (i.e., zircon picked up during ascent and emplacement of the magma) found in the silicic igneous rocks exhibits a similar age pattern as detrital zircon of the Shimanto sediments. However, the age pattern obtained in this study for zircon cores, which are considered to be restitic zircon (i.e., zircon derived from the source of the anatectic melt), shows little semblance with the age pattern of Shimanto sediments. It is, therefore, tentatively suggested that the source area of the silicic magmas may not be identical with the sediments of the Shimanto Accretionary Complex. Full article

(This article belongs to the Special Issue Igneous Rocks as Archives of Earth's Geological History: Magma Processes and Continental Crust Evolution)

15 pages, 5879 KiB

Open AccessArticle

The Mineralization Mechanism of the Axi Gold Deposit in West Tianshan, NW China: Insights from Fluid Inclusion and Multi-Isotope Analyses

by Fang Xia, Chuan Chen and Weidong Sun

Minerals 2025, 15(5), 536; https://doi.org/10.3390/min15050536 - 18 May 2025

Abstract

The Axi gold deposit, which is located in the Tulasu Basin of the West Tianshan orogenic belt in Northwest China, features vein-type ore bodies hosted in radial structural fractures formed due to volcanic activity. The deposit experienced three distinct mineralization stages: Stage I, [...] Read more.

The Axi gold deposit, which is located in the Tulasu Basin of the West Tianshan orogenic belt in Northwest China, features vein-type ore bodies hosted in radial structural fractures formed due to volcanic activity. The deposit experienced three distinct mineralization stages: Stage I, characterized by the microcrystalline quartz–pyrite crust; Stage II, characterized by quartz–sulfide–native gold veins; and Stage III, characterized by quartz–carbonate veins. Fluid inclusion studies have identified four types of inclusions: pure vapor, vapor-rich, liquid-rich, and pure liquid. The number of vapor-rich inclusions decreases when moving from Stage I to Stage III, whereas the number of liquid-rich inclusions increases. The fluid temperature gradually decreases from 178–225 °C in Stage I to 151–193 °C in Stage II and further to 123–161 °C in Stage III, whereas the fluid salinity decreases slightly from 2.1%–5.1% wt.% NaCl eqv to 1.4%–4.6% wt.% NaCl eqv and finally to 0.5%–3.7% wt.% NaCl eqv. As suggested by the results of the oxygen, hydrogen, and carbon isotope analyses, the ore-forming fluids were primarily meteoric water. Sulfur isotopic compositions indicate a single deep mantle source. The lead isotopic compositions closely resemble those of Dahalajunshan Formation volcanic rocks, indicating that these rocks were the primary source of the ore-forming material. In addition, gold mineralization formed in a Devonian–Early Carboniferous volcanic arc environment. Element enrichment was mainly caused by the circulation of heated meteoric water through the volcanic strata, while fluid boiling and water–rock interactions were the main mechanisms driving element precipitation. The integrated model developed in this study underscores the intricate interplay between volcanic processes and meteoric fluids during the formation of the Axi gold deposit, offering a robust framework for an understanding of the formation processes and enhancing the predictive exploration models in analogous geological settings. Full article

(This article belongs to the Special Issue Mineralogy, Geochemistry and Fluid Inclusion Study of Gold Deposits Endowed in Critical Metals)

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31 pages, 54013 KiB

Open AccessArticle

Ore-Forming Fluid Evolution and Ore Genesis of the Cuyu Gold Deposit in Central Jilin Province, NE China: Constraints from Geology, Fluid Inclusions, and H–O–S–Pb Isotope Studies

by Haozhe Li, Qun Yang, Leigang Zhang, Yunsheng Ren, Mingtao Li, Chan Li, Bin Wang, Sitong Chen and Xiaolei Peng

Minerals 2025, 15(5), 535; https://doi.org/10.3390/min15050535 - 17 May 2025

Viewed by 82

Abstract

The Cuyu gold deposit in central Jilin Province in Northeast China is located in the eastern segment of the northern margin of the North China Craton (NCC), as well as the eastern segment of the Xing’an–Mongolian Orogenic Belt (XMOB). Gold ore-bodies are controlled [...] Read more.

The Cuyu gold deposit in central Jilin Province in Northeast China is located in the eastern segment of the northern margin of the North China Craton (NCC), as well as the eastern segment of the Xing’an–Mongolian Orogenic Belt (XMOB). Gold ore-bodies are controlled by NW-trending faults and mainly occur in late Hercynian granodiorite. The mineralization process in the Cuyu deposit can be divided into three stages: quartz + coarse grained arsenopyrite + pyrite (stage I), quartz + sericite + pyrite + arsenopyrite + electrum + chalcopyrite + sphalerite (stage II), and quartz + calcite ± pyrite (stage III). Stage II is the most important for gold mineralization. We conducted analyses including petrography, microthermometry, laser Raman spectroscopy of fluid inclusions, and H–O–S–Pb isotopic analysis to elucidate the mineralization processes in the Cuyu deposit. Five types of primary fluid inclusions (FIs) are present in the hydrothermal quartz and calcite grains of the ore: liquid-rich two-phase aqueous fluid inclusions (L-type), vapor-rich two-phase aqueous fluid inclusions (V-type), CO₂-bearing two- or three-phase inclusions (C1-type), CO₂-rich two- or three-phase inclusions (C2-type), and pure CO₂ mono-phase inclusions (C3-type). From stages I to III, the fluid inclusion assemblages changed from L-, C2-, and C3-types to L-, V-, C1-, C2-, and C3-types and, finally, to L-types only. The corresponding homogenization temperatures for stages I to III were 242–326 °C, 202–298 °C, and 106–188 °C, and the salinities were 4.69–9.73, 1.63–7.30, and 1.39–3.53 wt.% NaCl equiv., respectively. The ore-forming fluid system evolved from a NaCl-H₂O-CO₂ ± CH₄ ± H₂S fluid system in stage I and II with immiscible characteristics to a homogeneous NaC-H₂O fluid system in stage III. Microthermometric data for stages I to III show a decreasing trend in homogenization temperatures and salinities. The mineral assemblages, fluid inclusions, and H–O–S–Pb isotopes indicate that the initial ore-forming fluids of stage I were exsolved from diorite porphyrite and characterized by a high temperature and low salinity. The addition of meteoric water in large quantities led to decreases in temperature and pressure, resulting in a NaCl-H₂O-CO₂ ± CH₄ ± H₂S fluid system with significant immiscibility in stage II, facilitating the deposition of gold and associated polymetallic sulfides. The Cuyu gold deposit has a similar ore genesis to those of gold deposits in the Jiapigou–Haigou gold belt (JHGB) of southeastern Jilin Province indicating potential for gold prospecting in the northwest-trending seam of the JHGB. Full article

(This article belongs to the Special Issue Genesis and Metallogeny of Non-ferrous and Precious Metal Deposits, 2nd Edition)

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25 pages, 4004 KiB

Open AccessArticle

Testing Pyrrhotite Trace Element Chemistry as a Vector Towards the Mineralization in the Sullivan Deposit, B.C

by Naci Sertug Senol, Daniel David Gregory, Indrani Mukherjee, Nelson Román, Roisin Kyne and Kaleb S. Boucher

Minerals 2025, 15(5), 534; https://doi.org/10.3390/min15050534 - 17 May 2025

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Abstract

Mineral exploration methods are expensive and time-consuming, especially in recent times, where many near-surface deposits have been found and exploited. To overcome these challenges, new strategies must be developed. Here, we test whether the trace element chemistry of pyrrhotite changes systematically with distance [...] Read more.

Mineral exploration methods are expensive and time-consuming, especially in recent times, where many near-surface deposits have been found and exploited. To overcome these challenges, new strategies must be developed. Here, we test whether the trace element chemistry of pyrrhotite changes systematically with distance from mineralization at the Sullivan deposit, British Columbia. If so, this could provide an additional tool to search for new ore bodies. Forty samples of the hanging wall, footwall, and mineralization hosting stratigraphy (host horizon) were collected from seven drill holes, both proximal and distal to the Sullivan deposit. These samples were analyzed using reflected light microscopy, an electron microprobe, and LA-ICPMS (laser ablation, inductively coupled plasma mass spectrometry). A total of three hundred and ninety LA-ICPMS analyses were used to build machine learning classifiers (cluster analysis and random forests) to determine whether an unknown pyrrhotite sample was from the mineralized horizon and, if so, whether it was proximal or distal to the mineralization. Our study found that the trace element abundance in pyrrhotite was higher in the footwall and hanging wall compared to the host horizon, and within the host horizon, was higher distal to the mineralization. Full article

(This article belongs to the Special Issue Mineral Chemistry: Tool for Vectoring towards Mineral Deposits)

42 pages, 2446 KiB

Open AccessReview

A Mineralogical Perspective on Rare Earth Elements (REEs) Extraction from Drill Cuttings: A Review

by Muhammad Hammad Rasool, Syahrir Ridha, Maqsood Ahmad, Raba’atun Adawiyah Bt Shamsuddun, Muhammad Khurram Zahoor and Azam Khan

Minerals 2025, 15(5), 533; https://doi.org/10.3390/min15050533 - 17 May 2025

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Abstract

The growing demand for rare earth elements (REEs) in high-tech and green energy sectors has prompted renewed exploration of unconventional sources. Drill cuttings, which are commonly discarded during subsurface drilling, are increasingly recognized as a potentially valuable, underutilized secondary REE reservoir. This review [...] Read more.

The growing demand for rare earth elements (REEs) in high-tech and green energy sectors has prompted renewed exploration of unconventional sources. Drill cuttings, which are commonly discarded during subsurface drilling, are increasingly recognized as a potentially valuable, underutilized secondary REE reservoir. This review adopts a mineral-first lens to assess REE occurrence, extractability, and recovery strategies from drill cuttings across various lithologies. Emphasis is placed on how REEs associate with specific mineral host phases ranging from ion-adsorbed clays and organically bound forms to structurally integrated phosphates, each dictating distinct leaching pathways. The impact of drilling fluids on REE surface chemistry and mineral integrity is critically examined, alongside an evaluation of analytical and extraction methods tailored to different host phases. A scenario-based qualitative techno-economic assessment and a novel decision-tree framework are introduced to align mineralogy with optimal recovery strategies. Limitations in prior studies, particularly in characterization workflows and mineralogical misalignment in leaching protocols, are highlighted. This review redefines drill cuttings from industrial waste to a strategic resource, advocating for mineralogically guided extraction approaches to enhance sustainability in the critical mineral supply chain. Full article

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

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27 pages, 15247 KiB

Open AccessArticle

Geochronological Evolution of the Safaga–Qena Transect, Northern Eastern Desert, Egypt: Implications of Zircon U-Pb Dating

by Sherif Mansour, Abdelghafar M. Abu-Elsaoud, Faouzi Haouala, Mohamed Zaki Khedr, Akihiro Tamura and Noriko Hasebe

Minerals 2025, 15(5), 532; https://doi.org/10.3390/min15050532 - 17 May 2025

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Abstract

The granitic rocks and the Dokhan Volcanics at the transect between Safaga and Qena, the Egyptian Northern Eastern Desert represent the northern termination of the Arabian–Nubian Shield (ANS), which, in turn, represents the northern part of the East African Orogeny (EAO). The geochronological [...] Read more.

The granitic rocks and the Dokhan Volcanics at the transect between Safaga and Qena, the Egyptian Northern Eastern Desert represent the northern termination of the Arabian–Nubian Shield (ANS), which, in turn, represents the northern part of the East African Orogeny (EAO). The geochronological development of the magmatic activities that constructed the ANS is critical in understanding these orogenies. The ANS was constructed through pre-collisional, syn-collisional, and post-collisional magmatic phases. The transition between these magmatic phases marks tectonic shifting from subduction to compressional and extensional tectonic settings, respectively. The chronological constraints of these tectonic–magmatic phases are still questionable. Our study aims to refine these chronological constraints through the dating of four calc-alkaline granitic rocks (722 ± 5 Ma–561 ± 4 Ma), five alkaline granitic rocks (758 ± 5 Ma–555 ± 4 Ma), and three Dokhan Volcanic rocks (618 ± 5 Ma–606 ± 5 Ma). Our results suggest the absence of any pre-collisional rocks. The syn-collisional magmatism extended here from 758 ± 5 Ma to 653 ± 7 Ma, demonstrating the chronological domination of the syn-orogenic compressional regime in the NED. The Dokhan Volcanic activity marked the shifting of the tectonic setting from a compressional to an extensional regime at 618 ± 5 Ma. Post-collisional plutonism dominated between 583 ± 5 Ma and 555 ± 4 Ma in the studied region, suggesting that ANS magmatic activity was extended to the Phanerozoic edge. These findings refute the classical interpretations of older magmatism as calc-alkaline granitoids and younger magmatism as alkaline granitoids. Pre-Neoproterozoic (pre-ANS) xenocrysts with ages of 1879 ± 22, 1401 ± 25, 1385 ± 12, 1232 ± 27, 1210 ± 18, and 1130 ± 15 Ma were yielded, which might support a local reworked ancient magmatic source. Full article

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

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27 pages, 21759 KiB

Open AccessArticle

Origin and Tectonic Implication of Cenozoic Alkali-Rich Porphyry in the Beiya Au-Polymetallic Deposit, Western Yunnan, China

by Yun Zhong, Yajuan Yuan, Ye Lu and Bin Xia

Minerals 2025, 15(5), 531; https://doi.org/10.3390/min15050531 - 16 May 2025

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Abstract

Cenozoic alkali-rich porphyries are widely distributed in the junction zone between the Sanjiang Orogenic belt and the Yangtze Plate. They are of great significance for understanding the regional geodynamics, tectonic evolution, and metallogenesis. However, the origin of these porphyries remains controversial. In this [...] Read more.

Cenozoic alkali-rich porphyries are widely distributed in the junction zone between the Sanjiang Orogenic belt and the Yangtze Plate. They are of great significance for understanding the regional geodynamics, tectonic evolution, and metallogenesis. However, the origin of these porphyries remains controversial. In this study, new petrological, geochemical, and geochronological data are presented for Cenozoic syenite porphyry from the Beiya porphyry Au-polymetallic deposit in western Yunnan. Zircon U-Pb dating results show that the Beiya syenite porphyries formed around 36.3–35.0 Ma, coinciding with the magmatic peak in the Jinshajiang-Red River (JSJ-RR) alkali-rich porphyry belt. Geochemical analyses indicate that the Beiya porphyries have potassic characteristics and an arc-like geochemical affinity, with C-type adakite affinity, suggesting a post-collisional setting. The JSJ-RR fault zone is unlikely to be the primary mechanism responsible for the formation of this alkali-rich porphyry magmatism. Instead, the development of the Beiya alkali-rich porphyries is likely associated with the convective removal of the lower part of the overthickened lithospheric mantle and asthenospheric upwelling during the Eocene–Oligocene. Their magmas probably originated from the partial melting of Paleo–Mesoproterozoic garnet amphibolite facies rocks in the thickened lower continental crust, with the addition of shoshonitic mafic magmas produced by the partial melting of metasomatized lithospheric mantle triggered by asthenospheric upwelling. This study provides additional reliable evidence to further constrain the origin of Cenozoic alkali-rich porphyries in the JSJ-RR belt. Full article

(This article belongs to the Special Issue Advances in Mantle–Crust Interactions for Petrogenesis and Ore-Forming Processes)

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32 pages, 18951 KiB

Open AccessArticle

Mineralogy and Geochemistry of Early Triassic Granite in South China: Insights into Source Region Characteristics and REE Mineralization

by Liya Yang, Yongfeng Cai, Jieting Ouyang, Fang Xu, Yankun Chen and Yun Zhou

Minerals 2025, 15(5), 530; https://doi.org/10.3390/min15050530 - 16 May 2025

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Abstract

Regolith-hosted rare-earth element (REE) deposits are some of the most important types of REE deposits. The relationship between Late Paleozoic and Early Mesozoic granite and regolith-hosted REE deposits is still poorly studied. Detailed geochronology, geochemistry, and rare-earth mineralogy analyses of Early Triassic granite [...] Read more.

Regolith-hosted rare-earth element (REE) deposits are some of the most important types of REE deposits. The relationship between Late Paleozoic and Early Mesozoic granite and regolith-hosted REE deposits is still poorly studied. Detailed geochronology, geochemistry, and rare-earth mineralogy analyses of Early Triassic granite in the South China Block were conducted. The geochronological results showed that four representative granite samples yielded formation ages of 245 ± 1 Ma, 244 ± 1 Ma, 244 ± 1 Ma, and 244 ± 2 Ma, respectively. The granites show geochemical affinity to A-type granite. They are characterized by enrichment in Rb, Th, and U, are depleted in Ba, Sr, P, and Ti, and show obvious negative Nb and Ta anomalies. They have high light rare-earth element (LREE) and low heavy rare-earth element (HREE) contents, with obvious negative Eu anomalies. They were derived from the partial melting of a sediment source and underwent intense fractional crystallization during the magma evolution process. They contain a certain number of rare-earth-element-bearing minerals, such as monazite, xenotime, apatite, and zircon. Their REE compositions and mineral associations are similar to those of the parent rocks from typical regolith-hosted REE deposits in South China. The highly weathered horizon at the ridge of the granite weathering crust profile has the highest REE content. A comprehensive analysis indicated that the degree of magma evolution, geomorphology, and weathering are important factors controlling the formation of regolith-hosted REE deposits in the area. Full article

(This article belongs to the Special Issue Advances in Mantle–Crust Interactions for Petrogenesis and Ore-Forming Processes)

23 pages, 12331 KiB

Open AccessArticle

Optimization of Magnetization Roasting and Magnetic Separation for the Recovery of Iron from Low-Grade Iron Plant Tailings

by Anele Shamase and Willie Nheta

Minerals 2025, 15(5), 529; https://doi.org/10.3390/min15050529 - 16 May 2025

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Abstract

This study employs response surface methodology (RSM) with a custom optimal design to develop and optimize iron (Fe) grade and recovery through magnetization roasting followed by induced dry-roll magnetic separation. The relationships between the independent and dependent variables are investigated. The effect of [...] Read more.

This study employs response surface methodology (RSM) with a custom optimal design to develop and optimize iron (Fe) grade and recovery through magnetization roasting followed by induced dry-roll magnetic separation. The relationships between the independent and dependent variables are investigated. The effect of roasting temperature, magnetization roasting time, magnetic field intensity, rotor speed, and product splitter position for the induced dry-roll magnetic separator on Fe grade and recovery are studied. Suitable models are generated to predict the optimum operating conditions. An analysis of Variance (ANOVA) is employed to validate the developed regression models’ adequacy and assess the main and interaction-related effects on Fe grade and recovery. During magnetization roasting, a satisfactory Fe grade of 66.8% with a recovery of 16.7% was obtained under optimal conditions of 1050 °C for 97 min. Conversely, after the induced dry-roll magnetic separator optimization, an Fe grade of 66.1% with a recovery of 60.2% was achieved under optimum conditions of 0.105 T for magnetic field intensity, 70 Hz for rotor speed, and an 11 mm product splitter position. This study effectively illustrates how RSM can model the processes of magnetization roasting and induced dry-roll magnetic separation, particularly concerning the operating parameters used for treating iron ore plant tailings. Furthermore, it highlights the efficiency of this methodology in generating substantial insights in a short timeframe while minimizing the number of experiments conducted. Full article

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

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37 pages, 16597 KiB

Open AccessArticle

Geochemistry, Isotope Characteristics, and Evolution of the Kesikköprü Iron Deposit (Türkiye)

by Erkan Yılmazer and Mustafa Haydar Terzi

Minerals 2025, 15(5), 528; https://doi.org/10.3390/min15050528 - 15 May 2025

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Abstract

The Kesikköprü iron deposit, located in the Central Anatolian Crystalline Complex, occurs in the triple contact of Kesikköprü granitoid, mafic–ultramafic rocks, and marble. The causative Kesikköprü granitoid, consisting of diorite, granodiorite, and granite, is classified as sub-alkaline, calc-alkaline, and shoshonitic, displaying metaluminous to [...] Read more.

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

(This article belongs to the Section Mineral Deposits)

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12 pages, 4511 KiB

Open AccessArticle

Assessment of Feldspars from Central Portugal Pegmatites for Sustainable Ceramic Applications

by Carla Candeias, Adga Gomes and Fernando Rocha

Minerals 2025, 15(5), 527; https://doi.org/10.3390/min15050527 - 15 May 2025

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Abstract

This study investigates the mineralogical, chemical, and fusibility characteristics of feldspar samples collected from eight pegmatitic bodies in central Portugal. The primary aim was to evaluate their suitability for use in ceramic applications, driven by the need to valorize local georesources, reduce dependence [...] Read more.

This study investigates the mineralogical, chemical, and fusibility characteristics of feldspar samples collected from eight pegmatitic bodies in central Portugal. The primary aim was to evaluate their suitability for use in ceramic applications, driven by the need to valorize local georesources, reduce dependence on imported raw materials, and contribute to the sustainability and competitiveness of the Portuguese ceramic sector. Samples were analyzed by X-Ray Diffraction (XRD), X-ray Fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Firing tests were performed to assess fusibility, whiteness, and visible impurity behavior. Results indicate that seven of the eight samples were dominated by a combination of microcline and albite, with minor amounts of quartz and muscovite. Crystallinity indices varied across samples, reflecting differences in mineral order and thermal reactivity. Chemical compositions showed acceptable levels of SiO₂ and Al₂O₃, and total alkali contents (Na₂O + K₂O) between 10% and 16%, aligning with industrial standards for ceramic raw materials. The Fe₂O₃ contents were below 0.3% in most samples, suggesting favorable conditions for whiteness upon firing. Loss on ignition (LOI) values were generally low, except for one sample rich in muscovite. Fusibility behavior varied significantly between samples, with albite-rich samples showing lower melting points and better flow characteristics, while microcline-dominant samples required higher temperatures for vitrification but contributed to structural stability. The K₂O/Na₂O ratio presented values favoring earlier softening and fluxing. Whiteness revealed that samples with low Fe₂O₃ and TiO₂ content, particularly those with low mica content, achieved the best aesthetic outcomes post-firing. Full article

(This article belongs to the Collection Clays and Other Industrial Mineral Materials)

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19 pages, 7249 KiB

Open AccessArticle

Effect of Calcium Chloride on the Reinforcement of Uranium Tailings with Sodium Hydroxide–Sodium Silicate–Metakaolin

by Qianjin Niu and Xiujuan Feng

Minerals 2025, 15(5), 526; https://doi.org/10.3390/min15050526 - 15 May 2025

Viewed by 60

Abstract

The uranium tailings mineral body is large and loose, and this could lead to radioactive contamination. Nuclides and heavy metals released from uranium tailings can be reduced through reinforcement treatment. The current study investigated the effect of CaCl₂ solutions with the same [...] Read more.

The uranium tailings mineral body is large and loose, and this could lead to radioactive contamination. Nuclides and heavy metals released from uranium tailings can be reduced through reinforcement treatment. The current study investigated the effect of CaCl₂ solutions with the same volume and different mass fractions on uranium tailing reinforcement under the premise of fixing the dosage of metakaolin, sodium hydroxide, sodium silicate, and the water reducer. It was found that, when 20.0% CaCl₂ was injected, the hydration reaction occurred more efficiently, and a more uniform gel polymer was produced. The degree of polymerization was higher, as well as the degree of aggregation near macropores. A large number of closed mesopores formed on the solidified surface. The pore structure of the solidified body was significantly improved; uranium ore particles had smaller gaps between them; the solidified body was better compacted; the leaching rates of uranium and its heavy metal ions were significantly reduced; and the compressive strength of the solidified body improved. In the triaxial test, the solidified body had a strength increase of 4.7 times. In addition to SEM, XPS, and XRD, the solidified samples were analyzed. In uranium slag solidified bodies, C-S-H and C-A-H gels and C-A-S-H and N-A-S-H polymers were formed. The gel polymers were wrapped around the uranium tailing particles, resulting in an 82.6% reduction in uranium leaching and a 57.2% reduction in radon exhalation. Full article

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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18 pages, 4982 KiB

Open AccessArticle

Precipitating Rare Earth by NH₄HCO₃ from a Concentrated Rare Earth and Magnesium Sulfate Solution

by Qiang Wang, Tao Qi, Hongdong Yu, Limin Zhang, Dongjiang Sun, Yinliang Liu, Tongxiang Liang and Lue Huang

Minerals 2025, 15(5), 525; https://doi.org/10.3390/min15050525 - 15 May 2025

Viewed by 78

Abstract

The ammonium bicarbonate precipitation method has become one of the main ways to extract rare earths from rare earth leaching solutions due to its advantages of simple operation, mature technology, and low cost. Therefore, the objective of this study was to explore the [...] Read more.

The ammonium bicarbonate precipitation method has become one of the main ways to extract rare earths from rare earth leaching solutions due to its advantages of simple operation, mature technology, and low cost. Therefore, the objective of this study was to explore the precipitation of rare earth carbonate (REC) from a concentrated rare earth and magnesium sulfate solution by ammonium bicarbonate. The terminal pH to precipitate rare earth was determined. The effects of factors including the feeding rate, temperature, ammonium bicarbonate concentration, seed dosage, and stirring rate on the rare earth precipitation efficiency, the Mg and SO₄²⁻ amounts in the obtained REC, and the median particle sizes of the REC were investigated. The effects of these factors on the Mg and SO₄²⁻ amounts in the REC and the median particle sizes of the REC were compared by one-way analysis of variance (ANOVA). The results showed that at a terminal pH of 6.8, a feeding rate of 0.5 mL/min, a temperature of 25 °C, an ammonium bicarbonate concentration of 0.6 mol/L, a crystal seed dosage of 7.5%, and a stirring speed of 300 r/min, without aging, the contents of rare earth oxide (REO), MgO, and SO₄²⁻ in the REC were 57.69%, 0.23%, and 1.68%, respectively, superior to the requirements of the current Chinese national standard (GB/T 16479-2020) for REC. The rare earth precipitation efficiency was 99.78%. Among the investigated factors, the pH was the main factor affecting the rare earth precipitation efficiency. The seed dosage significantly changed the median particle sizes of the REC and the Mg content of the REC. For SO₄²⁻, its content was fluctuant and could be controlled at a relatively low value by the seed dosage and specific stirring rate. Full article

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

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3 pages, 136 KiB

Open AccessEditorial

Editorial for Special Issue “Research on Ikaite—Natural Occurrences and Synthetic Mineral Precipitation”

by Gabrielle J. Stockmann and Juan Diego Rodríguez-Blanco

Minerals 2025, 15(5), 524; https://doi.org/10.3390/min15050524 - 15 May 2025

Viewed by 57

Abstract

This Special Issue consists of five articles published in the period of 2022–2025, with a special focus on the metastable calcium carbonate mineral ikaite (CaCO₃·6H₂O) and the pseudomorph type known as glendonite [...] Full article

(This article belongs to the Special Issue Research on Ikaite—Natural Occurrences and Synthetic Mineral Precipitation)

12 pages, 5901 KiB

Open AccessArticle

Characteristics of Mineralization of Refractory Gold and Its Influence on Cyanide Gold Leaching Rates: A Case Study in Pituca II, Zamora Chinchipe, Ecuador

by Santiago Jose Navas Jaramillo and Renato Efren Gonzalez Zuñiga

Minerals 2025, 15(5), 523; https://doi.org/10.3390/min15050523 - 15 May 2025

Viewed by 77

Abstract

The recovery of gold in metallurgical processes is significantly influenced by the presence of refractory minerals. This study investigates the mineralogical characteristics of refractory gold in the Pituca II ore deposit, with a focus on identifying the sulfide minerals that encapsulate gold particles [...] Read more.

The recovery of gold in metallurgical processes is significantly influenced by the presence of refractory minerals. This study investigates the mineralogical characteristics of refractory gold in the Pituca II ore deposit, with a focus on identifying the sulfide minerals that encapsulate gold particles and understanding their impact on gold recovery rates via cyanidation leaching. To establish a theoretical basis for optimizing gold recovery, a comprehensive suite of analytical techniques including electron microprobe analysis, petrographic analysis, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and X-ray diffraction was employed to characterize the ore’s composition and mineralogical properties. The primary ore minerals identified were pyrite, galena, chalcopyrite, and sphalerite, with hessite occurring as an accessory phase. Gold was observed as fine-grained particles (<40 µm), predominantly enclosed within pyrite and galena, contributing to its refractory nature. Cyanidation tests revealed a strong correlation between particle size and leaching efficiency: material ground to D₈₀ = 170 mesh (90 μm) achieved a recovery rate of 81.2%, compared to 72.2% for material at D₈₀ = 100 mesh (150 μm). These findings elucidate the mineralogical constraints on gold recovery and underscore the necessity of appropriate particle size reduction to enhance leaching performance. The study provides practical insights and targeted recommendations for pretreatment strategies, thereby contributing to more efficient exploitation of refractory gold ores in similar geological settings. Full article

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

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24 pages, 38314 KiB

Open AccessArticle

Multi-Analytical Characterization of Serpentinite Rocks Employed as Stone Material: An Example from Andalusia (Southern Spain), Basilicata, and Calabria (Southern Italy)

by Roberto Visalli, Rafael Navarro, Roberto Buccione, Valeria Indelicato, Giovanna Rizzo, Rosolino Cirrincione and Rosalda Punturo

Minerals 2025, 15(5), 522; https://doi.org/10.3390/min15050522 - 14 May 2025

Viewed by 141

Abstract

Serpentinites are metamorphic rocks constituted primarily by serpentine-group minerals (antigorite, chrysotile, lizardite) resulting from the transformation and low-temperature hydration of previous olivine-rich ultramafic rocks, such as dunite, lherzolite, wehrlite, and harzburgite. The peculiar features of the serpentinites such as the greenish color and [...] Read more.

Serpentinites are metamorphic rocks constituted primarily by serpentine-group minerals (antigorite, chrysotile, lizardite) resulting from the transformation and low-temperature hydration of previous olivine-rich ultramafic rocks, such as dunite, lherzolite, wehrlite, and harzburgite. The peculiar features of the serpentinites such as the greenish color and the intricate vein and mesh-like texture, as well as their role in CO₂ sequestration when carbonated, have hugely increased interest in studying these rocks over recent decades. Moreover, since antiquity, serpentinites have long been exploited, traded, and exported worldwide as daily tools, as well as in buildings and decorative stones in both internal and external architectural elements, because of their aesthetic appeal, attractiveness, and durability. In this work, we analyzed and compared petrographic features, geochemical signatures, and physical–mechanical properties of serpentinites from historical quarries from Andalusia (southern Spain), Basilicata, and Calabria (southern Italy) where they have been used as dimension stones in religious and civil buildings and as construction materials. We aim to evaluate and assess differences in petrographic, carbonation, uniaxial compressive strength, and seismic behavior, that could affect the efficiency when these serpentinites are used as either building and construction materials or for preservation/renovation purposes in cultural heritage. Results obtained from petrophysical investigations of serpentinites from these regions highlight that these materials are suitable for use in construction to various extents and are considered a valuable georesource, behind a detailed characterization carried out before their implementation in construction or conservation/restoration of architectural heritage. Full article

(This article belongs to the Special Issue Mineralogy, Chemistry, Weathering and Application of Serpentinite)

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26 pages, 5048 KiB

Open AccessArticle

Estimation of Copper Grade, Acid Consumption, and Moisture Content in Heap Leaching Using Extended and Unscented Kalman Filters

by Lisbel Bárzaga-Martell, Simón Diaz-Quezada, Humberto Estay and Javier Ruiz-del-Solar

Minerals 2025, 15(5), 521; https://doi.org/10.3390/min15050521 - 14 May 2025

Viewed by 128

Abstract

The leaching process is essential in the mining industry, because it efficiently extracts valuable minerals, such as copper. However, monitoring and controlling the leaching process presents significant challenges due to material variability, uneven distribution of the leaching solution, and the effects of environmental [...] Read more.

The leaching process is essential in the mining industry, because it efficiently extracts valuable minerals, such as copper. However, monitoring and controlling the leaching process presents significant challenges due to material variability, uneven distribution of the leaching solution, and the effects of environmental factors like temperature and moisture content. One of the main technological challenges is measuring variables within the leaching heap. Implementing state observers or estimators (i.e., virtual sensors) offers a promising solution, allowing for a cost-effective estimation of non-measurable process variables. To validate this approach, this paper proposes and analyzes the use of two estimation methods, the Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF), to estimate the moisture content, copper in the ore, and acid consumption based on measurements of acid and copper concentrations in the heap leaching process. The results obtained from simulations demonstrate accurate estimations from both state observers. The variable best estimated with EKF was the moisture content, achieving a 0.041% Integral Absolute Error (IAE) and a 0.069% Integral Square Error (ISE) in one of the analyzed scenarios. Utilizing these state estimators improves the understanding of the internal dynamics of heap leaching, often limited by the lack of field-level instrumentation, such as sensors and transmitters. This approach can enhance the operational efficiency of heap leaching plants by enabling the real-time estimation of unmeasurable variables, ultimately improving metal recovery and reducing acid consumption. Full article

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

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12 pages, 4591 KiB

Open AccessArticle

Characterization of Mineralogical Species in a Copper Concentrate After Acid Pretreatment

by Geraldine Villagrán Santana, Víctor Quezada, Oriol Rius-Ayra, Alisiya Biserova-Tahchieva and Nuria Llorca-Isern

Minerals 2025, 15(5), 520; https://doi.org/10.3390/min15050520 - 14 May 2025

Viewed by 164

Abstract

In Chile, copper concentrate production through mineral flotation is increasing while production through hydrometallurgical processes is decreasing due to the depletion of oxidized ores. Using the idle capacity of hydrometallurgy plants for acid pretreatment of sulfate ores before the leaching stage is an [...] Read more.

In Chile, copper concentrate production through mineral flotation is increasing while production through hydrometallurgical processes is decreasing due to the depletion of oxidized ores. Using the idle capacity of hydrometallurgy plants for acid pretreatment of sulfate ores before the leaching stage is an attractive alternative; however, a deeper understanding of the process and the products of such treatment is required. In this study, the mineral species formed during acid pretreatment are characterized to identify new mineralogical species. Pretreatment was conducted at 50 °C with 210 kg/t H₂SO₄ over 15 days on a copper concentrate mainly composed of enargite (35.93%). The characterization techniques used were X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and X-ray Photoelectron Spectroscopy (XPS). XRD identified copper sulfate (CuSO₄) formation and the disappearance of chalcocite/digenite (Cu₂S) and bornite (Cu₅FeS₄), indicating their transformation into sulfates. FESEM showed that enargite particles were oxidized, suggesting they did not form copper sulfates. The XPS results confirmed the presence of copper in species such as sulfides and sulfates. The results indicate that chalcocite and bornite transformed into copper sulfates, while chalcopyrite and enargite were only superficially oxidized. The combination of techniques allowed for a detailed identification of mineral transformations during pretreatment. Full article

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

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23 pages, 24961 KiB

Open AccessArticle

Characteristics of Ore-Bearing Tectono-Stratigraphic Zones of the Shyngys-Tarbagatai Folded System at the Current Stage of Study

by Eleonora Y. Seitmuratova, Yalkunzhan K. Arshamov, Diyas O. Dautbekov, Moldir A. Mashrapova, Nurgali S. Shadiyev, Ansagan Dauletuly, Saltanat Bakdauletkyzy and Tauassar K. Karimbekov

Minerals 2025, 15(5), 519; https://doi.org/10.3390/min15050519 - 14 May 2025

Viewed by 168

Abstract

This study analyzes the ore potential of the tectono-stratigraphic zones in the Shyngys-Tarbagatai folded system using metallogenic diagrams. These diagrams condense extensive geological and metallogenic data, illustrating stratified and intrusive formations, formation types, depositional environments, and ore loads in chronological sequence. The analysis [...] Read more.

This study analyzes the ore potential of the tectono-stratigraphic zones in the Shyngys-Tarbagatai folded system using metallogenic diagrams. These diagrams condense extensive geological and metallogenic data, illustrating stratified and intrusive formations, formation types, depositional environments, and ore loads in chronological sequence. The analysis highlights variations in ore mineralization intensity across the zones, identifying both highly and less ore-bearing areas. Most zones show polymetallic mineralization with 2 to 12 types of minerals; gold and copper are present in all zones. Temporal analysis identified key productive levels in the Late Ordovician, Early Silurian, and Early Devonian, corresponding to active stages of island arcs, forearc and backarc basins, and the Devonian volcanic–plutonic belt. The structures of the Shyngys-Tarbagatai folded system are classified as island-arc structures of active continental margins. Comparing the ore potential of its tectono-stratigraphic zones with similar modern structures shows that, except for the Maikain zone, all others have significantly lower ore potential. The obtained data is most likely a result of the region’s poor exploration coverage. As such, future efforts should prioritize further investigation of the identified mineralization zones. This is evident from the dominance of small, medium, and large deposits, and ore occurrences in all tectono-stratigraphic zones when assessing their ore potential. Preliminary analysis of the ore potential in the tectono-stratigraphic zones of the Shyngys-Tarbagatai folded system, based on metallogenic diagrams, clearly supports the need for regional and exploration studies. These should focus on poorly explored stratigraphic levels, ore-bearing geological formations, and geodynamic settings that are favorable for deposit formation. This will provide a more accurate assessment of the potential in these zones. Full article

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

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22 pages, 4895 KiB

Open AccessArticle

Ore Genesis of the Huanggang Iron-Tin-Polymetallic Deposit, Inner Mongolia: Constraints from Fluid Inclusions, H–O–C Isotopes, and U-Pb Dating of Garnet and Zircon

by Hanwen Xue, Keyong Wang, Qingfei Sun, Junchi Chen, Xue Wang and Haoming Li

Minerals 2025, 15(5), 518; https://doi.org/10.3390/min15050518 - 14 May 2025

Viewed by 183

Abstract

The Huanggang iron-tin deposit, located in the southern Greater Khingan Range, is one of the largest Fe-Sn deposits in Northern China (NE China). Iron-tin mineralization occurs mainly in the contact zone between granitoid intrusions and the marble of the Huanggang and Dashizhai formations. [...] Read more.

The Huanggang iron-tin deposit, located in the southern Greater Khingan Range, is one of the largest Fe-Sn deposits in Northern China (NE China). Iron-tin mineralization occurs mainly in the contact zone between granitoid intrusions and the marble of the Huanggang and Dashizhai formations. Six mineralization stages are identified: (I) anhydrous skarn, (II) hydrous skarn, (III) cassiterite-quartz-calcite, (IV) pyrite-arsenopyrite-quartz-fluorite, (V) polymetallic sulfides-quartz, and (VI) carbonate ones. Fluid inclusions (FIs) analysis reveals that Stage I garnet and Stage II–III quartz host liquid-rich (VL-type), vapor-rich two-phase (LV-type), and halite-bearing three-phase (SL-type) inclusions. Stage IV quartz and fluorite, along with Stage V quartz, are dominated by VL- and LV-type inclusions, while Stage VI calcite contains exclusively VL-type inclusions. The FIs in Stages I to VI homogenized at 392–513, 317–429, 272–418, 224–347, 201–281, and 163–213 °C, with corresponding salinities of 3.05–56.44, 2.56–47.77, 2.89–45.85, 1.39–12.42, 0.87–10.62, and 4.48–8.54 wt% NaCl equiv., respectively. The H–O–C isotopes data imply that fluids of the anhydrous skarn stage (δD = −101.2 to −91.4‰, δ¹⁸O_H2O = 5.0 to 6.0‰) were of magmatic origin, the fluids of hydrous skarn and oxide stages (δD = −106.3 to −104.7‰, δ¹⁸O_H2O = 4.3 to 4.9‰) were characterized by fluid mixing with minor meteoric water, while the fluids of sulfide stages (δD = −117.4 to −108.6‰, δ¹⁸O_H2O = −3.4 to 0.3‰, δ¹³C_V-PDB= −12.2 to −10.9‰, and δ¹⁸O_V-SMOW = −2.2 to −0.7‰) were characterized by mixing of significant amount of meteoric water. The ore-forming fluids evolved from a high-temperature, high-salinity NaCl−H₂O boiling system to a low-temperature, low-salinity NaCl−H₂O mixing system. The garnet U-Pb dating constrains the formation of skarn to 132.1 ± 4.7 Ma (MSWD = 0.64), which aligns, within analytical uncertainty, with the weighted-mean U−Pb age of zircon grains in ore-related K-feldspar granite (132.6 ± 0.9 Ma; MSWD = 1.5). On the basis of these findings, the Huanggang deposit, formed in the Early Cretaceous, is a typical skarn-type system, in which ore precipitation was principally controlled by fluid boiling and mixing. Full article

(This article belongs to the Special Issue Metallogenic Regularity and Metallographic Prediction of Strategic Deposits)

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22 pages, 18204 KiB

Open AccessArticle

Late Paleozoic–Mesozoic Tectonic Evolution of the Mudanjiang Ocean: Constraints from the Zircon U-Pb and Ar-Ar Chronology of the Heilongjiang Complex, NE China

by Jianxin Xu, Peiyuan Hu, Wendong Wang, Hongyu Guo and Xin Zhang

Minerals 2025, 15(5), 517; https://doi.org/10.3390/min15050517 - 14 May 2025

Viewed by 167

Abstract

The Heilongjiang Complex provides a crucial geological record of the evolutionary history of the Mudanjiang Ocean, making it significant for understanding the accretion process between the Jiamusi Block and the Songliao Block. In this study, we analyzed samples from the Heilongjiang Complex in [...] Read more.

The Heilongjiang Complex provides a crucial geological record of the evolutionary history of the Mudanjiang Ocean, making it significant for understanding the accretion process between the Jiamusi Block and the Songliao Block. In this study, we analyzed samples from the Heilongjiang Complex in the Huanan region using zircon U-Pb and ⁴⁰Ar/³⁹Ar isotopic dating. The LA-ICP-MS U-Pb dating results show that the deposition time of the mica quartz schist is Late Triassic (237–207 Ma), while the protolith age of the amphibolite is Middle Triassic (245.5 ± 1.2 Ma). Detrital zircon ages from the mica quartz schist reveal four groups: 155–229 Ma, 237–296 Ma, 485–556 Ma, and 585–2238 Ma. The provenances are related to the magmatic and metamorphic activities at the junction of the Jiamusi Block and Songliao Block. ⁴⁰Ar/³⁹Ar isotopic dating yielded a plateau age of 183.40 ± 1.83 Ma for phengite in the mica quartz schist, with the metamorphic ages obtained from zircon U-Pb dating. We identify three major metamorphic events in the Heilongjiang Complex: (1) ~229 Ma, marking the earliest tectonic thermal disturbance in the complex; (2) 207–202 Ma, corresponding to the metamorphic event related to the collision between the Jiamusi Block and Songliao Block; and (3) ~183 Ma, indicating the closure of the Mudanjiang Ocean. Integrating these new findings with the results of previous research on magmatism and metamorphism, we reconstruct the tectonic evolution of the Mudanjiang Ocean from the Late Paleozoic to the Mesozoic. During the Early Permian, the Mudanjiang Ocean had already opened. Between the Middle Permian and Middle Triassic, bidirectional subduction occurred. In the Late Triassic, the Mudanjiang Ocean entered a subduction dormancy period. By the Early to Middle Jurassic, the Mudanjiang Ocean closed due to continental collision, leading to the final positioning of the Heilongjiang Complex. Full article

(This article belongs to the Special Issue Geochronological Methods Applied to the Exploration of Tectonic and Geological Processes)

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24 pages, 4894 KiB

Open AccessArticle

Microstructural Characterization of Expansive Soil Stabilized with Coconut Husk Ash: A Multi-Technique Investigation into Mineralogy, Pore Architecture, and Surface Interactions

by Ankur Abhishek, Anasua GuhaRay, Toshiro Hata and Hossam Abuel-Naga

Minerals 2025, 15(5), 516; https://doi.org/10.3390/min15050516 - 14 May 2025

Viewed by 196

Abstract

Black cotton soil (BCS) is unsuitable for construction due to its high plasticity, low shear strength, and significant volume changes upon wetting and drying. The present study investigates the effectiveness of an alkali-activated coconut husk ash (CHA) binder in improving the geotechnical properties [...] Read more.

Black cotton soil (BCS) is unsuitable for construction due to its high plasticity, low shear strength, and significant volume changes upon wetting and drying. The present study investigates the effectiveness of an alkali-activated coconut husk ash (CHA) binder in improving the geotechnical properties of BCS. CHA is derived from coconut husk and serves as a sustainable binder. Microstructural characterization of untreated and CHA-treated BCS was carried out using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The specific surface area (SSA) and porosity were evaluated using nitrogen gas adsorption methods based on the Brunauer–Emmett–Teller (BET) and Langmuir techniques. The Barrett–Joyner–Halenda (BJH) method demonstrated a decrease in mean pore diameter from 6.7 nm to 6.2 nm following CHA treatment. The SSA diminished from 40.94 m²/g to 25.59 m²/g, signifying the development of calcium silicate hydrate (C-S-H) gels that occupied the pore spaces. The formation of pozzolanic reaction products enhanced the microstructural integrity of the treated soil. Unconfined compressive strength (UCS) test results at 24 h and 28 days of curing for CHA-treated soil have been incorporated to analyze the optimum binder content. The UCS values enhanced significantly from 182 kPa to 305 kPa and 1030 kPa, respectively, at 9% binder content after 24 h and 28 days of curing. The microstructural and mechanical strength test analysis results indicated that CHA is a feasible and environmentally sustainable substitute for BCS stabilization. CHA-based AAB will be an eco-friendly alternative to cement and lime, reducing CO₂ emissions and construction costs. Full article

(This article belongs to the Special Issue Role of Clay Mineralogy in Geotechnical Engineering Behavior of Clay Soils)

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22 pages, 16632 KiB

Open AccessArticle

Multiscale Characterization of Pore Structure and Heterogeneity in Deep Marine Qiongzhusi Shales from Southern Basin, China

by Majia Zheng, Yana Chen, Tingke Tang, Ya Wu, Ying Chen, Junyu Chen, Shixuan Peng and Jizhen Zhang

Minerals 2025, 15(5), 515; https://doi.org/10.3390/min15050515 - 14 May 2025

Viewed by 168

Abstract

The pore structure of shale is a critical factor influencing the occurrence and flow of shale gas. Characterizing the pore structure and studying its heterogeneity are of paramount importance for a deeper understanding of the laws governing hydrocarbon occurrence, as well as for [...] Read more.

The pore structure of shale is a critical factor influencing the occurrence and flow of shale gas. Characterizing the pore structure and studying its heterogeneity are of paramount importance for a deeper understanding of the laws governing hydrocarbon occurrence, as well as for enhancing the efficiency of exploration and development. This work addresses the complex characteristics of multiscale coupling in the pore systems of shale reservoirs, focusing on the ultra-deep Qiongzhusi Formation shale in the southern region. Through the integrated application of cross-scale observation techniques and physicochemical analysis methods, a refined analysis of the pore structure is achieved. Utilizing field emission scanning electron microscopy imaging technology, the types and morphological characteristics of pores are identified. Additionally, a fluid–solid coupling analysis method employing high-pressure mercury intrusion and low-temperature gas adsorption (CO₂/N₂) is utilized to elucidate the characteristics of pore structure and heterogeneity while also analyzing the influence of matrix components on these features. The results indicate that the shale of the Qiongzhusi Formation is rich in feldspar minerals, facilitating the development of numerous dissolution pores, with the pore system predominantly consisting of inorganic mineral pores. The full pore size curve of the shale generally exhibits a bimodal characteristic, with a high proportion of mesopores. A strong positive linear relationship is observed between pore volume and specific surface area, whereby larger pore spaces reduce pore heterogeneity, with mesopore volume playing a decisive role. This study provides scientific support for the evaluation and strategic deployment of exploration and development in ultra-deep shale reservoirs of the Qiongzhusi Formation. Full article

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

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26 pages, 7883 KiB

Open AccessArticle

Technosol Micromorphology Reveals the Early Pedogenesis of Abandoned Rare Earth Element Mining Sites Undergoing Reclamation in South China

by Françoise Watteau, Jean Louis Morel, Chang Liu, Yetao Tang and Hermine Huot

Minerals 2025, 15(5), 514; https://doi.org/10.3390/min15050514 - 14 May 2025

Viewed by 157

Abstract

The process of anthropogenic pedogenesis has necessarily become an important aspect of the study of today’s soils. The sustainable reclamation or remediation of soils degraded by industrial or mining activities is currently of great interest worldwide. In this field, the study of thin [...] Read more.

The process of anthropogenic pedogenesis has necessarily become an important aspect of the study of today’s soils. The sustainable reclamation or remediation of soils degraded by industrial or mining activities is currently of great interest worldwide. In this field, the study of thin soil sections can provide relevant answers, particularly to questions concerning the evolution of these soils under the impact of reclamation practices. Here, we describe an experiment to reclaim former rare earth element mining sites in China using organic soil amendments and plantations of a local fiber plant, Boehmeria nivea. Two years after the start of the experiment, a study of soil structure, considered as an indicator of soil biofunctioning, was carried out on the different plots, supplemented by monitoring of physico-chemical properties. Morphological (light microscopy) and analytical (SEM-EDX, µ-XRF) characterization of thin sections allowed us to pinpoint some pedological processes as aggregation with particular reference to the contribution of biological factors and mineral species, highlighting the impact of the practices implemented. Using a soil micromorphology approach enabled us to track the rapid evolution of the early stages of pedogenesis of these Technosols and to provide insight into the potential for reclamation of these mined sites in the future. Full article

(This article belongs to the Special Issue Thin Sections: The Past Serving The Future)

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15 pages, 4107 KiB

Open AccessArticle

Characteristics of Heat-Depleted Thermal Water Re-Injection-Induced Water–Rock Interactions in a Sandstone Reservoir Containing Carbonate and Silicate Minerals (Szentes, Hungary)

by Eszter Sendula, Richárd Albrecht, Catarina Conceição de Castro, Eszter Keresztény-Borbás, Zsuzsanna Szabó-Krausz and János Kovács

Minerals 2025, 15(5), 513; https://doi.org/10.3390/min15050513 - 13 May 2025

Viewed by 187

Abstract

A thorough understanding of the chemistry involved in reinjecting heat-depleted geothermal water into poorly consolidated sandstone is vital for the effective design of treatments targeting subsurface rock formations. The intricate chemical interactions occurring within sandstone systems can result in the dissolution of certain [...] Read more.

A thorough understanding of the chemistry involved in reinjecting heat-depleted geothermal water into poorly consolidated sandstone is vital for the effective design of treatments targeting subsurface rock formations. The intricate chemical interactions occurring within sandstone systems can result in the dissolution of certain minerals and the subsequent precipitation of others, which may significantly contribute to damage within the formation. This process can alter the physical properties of the rock, potentially leading to reduced permeability and other challenges in resource extraction. Thus, it is imperative to monitor not only the concentration of various chemical species present in the geothermal water and sandstone, but also the spatial distribution of these geochemical reactions. By doing so, we can better predict and mitigate their potential adverse effects on rock formations, ensuring the long-term success and efficiency of geothermal energy extraction and other subsurface activities. In this study, we conducted laboratory experiments using both model and natural formation waters, as well as rock samples, to investigate water–rock interactions in a sandstone reservoir in the Szentes area of Hungary. Geochemical models were run with two different thermodynamic databases to simulate laboratory experiments, predict the effects of heat-depleted geothermal water reinjection into the reservoir, and assess predictions of different geochemical databases. Our study shows that calcite dissolves while quartz, kaolinite, and dolomite form. Other mineral reactions, however, remain less certain. The PHREEQC database indicates chlorite dissolution along with the formation of small amounts of feldspars and hematite, whereas the Thermoddem database predicts montmorillonite dissolution and chlorite precipitation. The reservoir porosity and permeability are expected to change over time as a result of mineral reactions. Modeling results, however, indicate negligible porosity changes as the reservoir reaches equilibrium state. The general concept proposed here, which focuses on the geochemical properties of the reinjected water and reservoir, provides a framework for detailed analysis of the geothermal system—a critical step for ensuring sustainable geothermal operations. Full article

(This article belongs to the Special Issue Petrological and Geochemical Characteristics of Reservoirs)

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39 pages, 14613 KiB

Open AccessReview

Direct Lithium Extraction from Seawater Brine: An Assessment of Technology and Existing Commercial Systems

by Mosaab Alghamdi, Thomas Altmann and Ratul Das

Minerals 2025, 15(5), 512; https://doi.org/10.3390/min15050512 - 13 May 2025

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Abstract

Traditional lithium extraction methods are time-consuming and energy-intensive, often leaving a large environmental footprint due to significant freshwater consumption. However, direct lithium extraction (DLE) technologies offer a more efficient and sustainable alternative. DLE can reduce the production time and energy consumption of the [...] Read more.

Traditional lithium extraction methods are time-consuming and energy-intensive, often leaving a large environmental footprint due to significant freshwater consumption. However, direct lithium extraction (DLE) technologies offer a more efficient and sustainable alternative. DLE can reduce the production time and energy consumption of the overall system, leading to lower costs. This technology is especially promising for extracting lithium from low-concentration brine such as seawater, which contains 8000 times more lithium than land sources. With global demand for lithium expected to reach a third of commercially available land-brine reserves by 2050, DLE’s potential to tap into the vast ocean reserves is crucial. Numerous organizations and developers are working to develop and refine new DLE systems to meet the growing demand for lithium, while others are working on integrating various DLE technologies to create more advanced and efficient systems to enhance extraction efficiency, product quality, and cost-effectiveness. In this review, we assess DLE’s commercial potential, providing an overview of the technology and examining current commercially deployed systems. Full article

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

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25 pages, 9413 KiB

Open AccessArticle

Barian Micas and Exotic Ba-Cr and Ba-V Micas Associated with Metamorphosed Sedimentary Exhalative Baryte Deposits near Aberfeldy, Scotland, UK

by Norman R. Moles

Minerals 2025, 15(5), 511; https://doi.org/10.3390/min15050511 - 13 May 2025

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Abstract

Regionally metamorphosed, Neoproterozoic stratiform baryte deposits near Aberfeldy in the Grampian Highlands of Scotland, UK, contain barium-poor and barium-rich micas in the host rocks and mineralized strata, respectively. The barium-rich micas include muscovite, biotite, phlogopite, and chromium-bearing muscovite. They occur in schistose metasediments [...] Read more.

Regionally metamorphosed, Neoproterozoic stratiform baryte deposits near Aberfeldy in the Grampian Highlands of Scotland, UK, contain barium-poor and barium-rich micas in the host rocks and mineralized strata, respectively. The barium-rich micas include muscovite, biotite, phlogopite, and chromium-bearing muscovite. They occur in schistose metasediments and metabasites, in barium-feldspar rocks, and in small amounts in baryte rock. An extensive study of micas in a range of lithologies using electron-probe micro-analysis found up to 10.86 wt% BaO in muscovite, 5.46 wt% in biotite, and 15.70 wt% in Ba-Cr muscovite, the latter containing up to 9.27 wt% Cr₂O₃. Compositions are comparable with Ba- and Ba-Cr-micas in other metamorphosed Sedimentary Exhalative deposits and barium-rich metasediments worldwide. In one baryte rock sample, disseminated crystals of an exotic Ba-V-Cr mica contain up to 12.33 wt% BaO and 10.82 wt% V₂O₃, compositionally similar to Ba-V micas in the Hemlo lode gold deposit, Ontario. Ba²⁺ incorporation is mainly by coupled substitution with Al³⁺ for K⁺ + Si⁴⁺ in the tetrahedral site. The extent of phengitic (Tschermakitic) substitution is typical of micas in amphibolite-facies metasediments. Similar Fe:Mg ratios in coexisting muscovite and biotite reflect partitioning of iron into sulphides and metamorphic equilibration, with rare exceptions in fine-grained rocks that exhibit millimetre-scale disequilibrium. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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Minerals, Volume 15, Issue 5 (May 2025) – 108 articles

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