Minerals

15 pages, 3279 KB

Open AccessArticle

Geochemical Characteristics, U-Pb Age, and Hf Isotope of Zircons from Muscovite Granite in Aotou Sn Deposit, Eastern Nanling Range, South China

by Wei Li, Na Guo, Jie Lu, Xinghai Lang, Dunmei Lian, Qiwen Yuan and Shuwen Chen

Minerals 2025, 15(12), 1331; https://doi.org/10.3390/min15121331 - 18 Dec 2025

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Abstract

The Jiulongnao W–Sn ore field in the eastern Nanling Range is characterized by large-scale early Yanshanian magmatic activity and W–Sn mineralization. In recent years, increasing attention has been given to the close relationship between Indosinian magmatic activity and Sn mineralization. The Aotou quartz [...] Read more.

The Jiulongnao W–Sn ore field in the eastern Nanling Range is characterized by large-scale early Yanshanian magmatic activity and W–Sn mineralization. In recent years, increasing attention has been given to the close relationship between Indosinian magmatic activity and Sn mineralization. The Aotou quartz vein-type Sn deposit is unique for only Sn mineralization without W during the Indosinian period. Seventeen thin-to-thick cassiterite–quartz veins are densely distributed in Ordovician metasandstone and slate, and these veins extend down to the top of the concealed granite. However, both the diagenetic age and the petrological characteristics of the concealed granite remain unclear. This contribution shows that the Aotou muscovite intrusion is a highly fractionated S-type pluton, characterized by a peraluminous, high-K composition, enrichment in LREEs, and depletion of Ba, Sr, Ti, and Eu. In this study, LA–ICP–MS zircon U–Pb dating of the concealed muscovite granite yields emplacement ages of 238.7 ± 1.0 Ma and 225.4 ± 0.9 Ma, indicating that at least two stages of magmatic intrusion occurred in the Triassic, with the diagenetic environment transitioning from a compressional setting to an extensional setting. The ε_Hf(t) values during the two stages are −0.98 to −0.95 and −0.98 to −0.96, and the T_DM2 values are 1.78–2.08 Ga and 1.78–2.06 Ga, indicating that two-stage magma was derived from the late Paleoproterozoic lower crustal materials. Comprehensive analysis reveals that the second stage of Indosinian magma intrusion (232–225 Ma) in the Jiulongnao ore field is closely related to Sn mineralization, and the northern Wenying pluton has good prospecting potential for quartz vein-type Sn(–W) deposits. Full article

(This article belongs to the Special Issue Mineralogy, Geochemistry and Geochronology of W-Sn Polymetallic Deposits, 2nd Edition)

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15 pages, 2527 KB

Open AccessArticle

Improving Marine Mineral Delineation with Planar Self-Potential Data and Bayesian Inversion

by Lijuan Zhang, Shengfeng Feng, Shengcai Xu, Dingyu Huang, Hewang Li, Ying Su and Jing Xie

Minerals 2025, 15(12), 1330; https://doi.org/10.3390/min15121330 - 18 Dec 2025

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Abstract

The exploration of marine minerals, essential for sustainable development, requires advanced techniques for accurate resource delineation. The self-potential (SP) method, sensitive to mineral polarization, has been increasingly deployed using autonomous underwater vehicles. This approach enables dense planar SP data acquisition, offering the potential [...] Read more.

The exploration of marine minerals, essential for sustainable development, requires advanced techniques for accurate resource delineation. The self-potential (SP) method, sensitive to mineral polarization, has been increasingly deployed using autonomous underwater vehicles. This approach enables dense planar SP data acquisition, offering the potential to reduce inversion uncertainties through enhanced data volume. This study investigates the benefits of inverting planar SP datasets for improving the spatial delineation of subsurface deposits. An analytical solution was derived to describe SP responses of spherical polarization models under a planar measurement grid. An adaptive Markov chain Monte Carlo algorithm within the Bayesian framework was employed to quantitatively assess the constraints imposed by the enriched dataset. The proposed methodology was validated through two synthetic cases, along with a laboratory-scale experiment that monitored the redox process of a spherical iron–copper model. The results showed that, compared to single-line data, the planar data reduced the average error in parameter means from 10.9% and 6.4% to 4.1% and 1.7% for synthetic and experimental cases, respectively. In addition, the 95% credible intervals of model parameters narrowed by nearly 50% and 40%, respectively. Full article

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

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35 pages, 4169 KB

Open AccessArticle

Rare Inclusions of Coexisting Silicate Glass and Cu-PGM Sulfides in Pt-Fe Nuggets, Northwest Ecuador: Fractionation, Decompression Exsolutions, and Partial Melting

by B. Jane Barron and Lawrence Barron

Minerals 2025, 15(12), 1329; https://doi.org/10.3390/min15121329 - 18 Dec 2025

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Abstract

Pt-Fe alloys with abundant inclusions are from the Camumbi River placer deposit, Ecuador. They are derived from unknown Alaskan–Uralian-type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Compositions of our previously documented chilled silicate glass inclusions are increasingly fractioned from hydrous ferrobasalt to [...] Read more.

Pt-Fe alloys with abundant inclusions are from the Camumbi River placer deposit, Ecuador. They are derived from unknown Alaskan–Uralian-type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Compositions of our previously documented chilled silicate glass inclusions are increasingly fractioned from hydrous ferrobasalt to rhyolite in terms of TAS (total alkalis vs. silica). Their liquid lines of descent change from tholeiitic to the calc-alkaline magma series. Here, we document seven rare composite inclusion parageneses of Cu–PGM (platinum-group mineral) sulfides, each coexisting with and exsolved from related fractionated silicate glass (melt). Differentiation is dominated by fractional crystallization in PGM bulk compositions from tholeiitic silicate melts at the highest T (temperature): ~1018 °C. Silicate glass inclusions following the lower T calc-alkaline trend coexist with sulfide PGM parageneses that were likely differentiated, in terms of Pt-Rh-Pd and BMs (base metals), by incongruent melting due to decompression and S-degassing at ~983–830 °C. S-saturated sulfide melts become S-undersaturated below 845 °C. The calculated temperatures are for silicate glass. Pt-rich braggite shows increasing fractionation towards Pd-rich vysotskite within one inclusion paragenesis. A late braggite–vysotskite fractionation trend shows decreasing minor base metals (BMs). Thiospinels are dominated by cuprorhodsite. Minor thiospinels indicate Fe and then strong Ni enrichment at the lowest T. Decompression exsolutions, deflation, and the partial melting of some sulfide inclusion parageneses support rapid ascent to higher crustal levels within a deep-sourced cumulate intrusion. Full article

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

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33 pages, 1690 KB

Open AccessArticle

Revisiting Albarracín Rock Art Through Multivariate pXRF Analysis of White, Black, and Red Pigments

by Pablo Martín-Ramos, José Antonio Cuchí-Oterino and Manuel Bea-Martínez

Minerals 2025, 15(12), 1328; https://doi.org/10.3390/min15121328 - 18 Dec 2025

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Abstract

Rock art in the Albarracín Cultural Park represents one of Spain’s most significant concentrations of post-Paleolithic paintings, yet comprehensive chemical characterization across multiple shelters remained lacking. This study analyzes 102 pigment samples (54 white, 31 black, 17 red) from 12 shelters using portable [...] Read more.

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

(This article belongs to the Special Issue Mineral Pigments: Properties Analysis and Applications)

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3 pages, 119 KB

Open AccessEditorial

Editorial for a New Section: Mineralogy Beyond Earth

by Leonid Dubrovinsky

Minerals 2025, 15(12), 1327; https://doi.org/10.3390/min15121327 - 18 Dec 2025

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Abstract

Mineralogy has traditionally developed within the context of Earth, the most accessible planetary body and our primary natural laboratory [...] Full article

21 pages, 23634 KB

Open AccessReview

The Role of OM in the Formation of Sandstone-Type Uranium Ore—A Review

by Zhiyang Nie, Shefeng Gu, Aihong Zhou, Changqi Guo, Hu Peng, Hongyu Wang, Lei Li, Qilin Wang, Yan Hao, Haozhan Liu and Chao Liu

Minerals 2025, 15(12), 1326; https://doi.org/10.3390/min15121326 - 18 Dec 2025

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Abstract

Sandstone-hosted uranium deposits represent one of the most critical global uranium resources suitable for in situ recovery, with their formation closely associated with organic matter (OM). We conducted a systematic literature review to synthesize over 100 published studies sourced from authoritative databases (Elsevier, [...] Read more.

Sandstone-hosted uranium deposits represent one of the most critical global uranium resources suitable for in situ recovery, with their formation closely associated with organic matter (OM). We conducted a systematic literature review to synthesize over 100 published studies sourced from authoritative databases (Elsevier, Google Scholar, Web of Science, Scopus, CNKI, etc.). This study systematically summarizes the types and geological characteristics of OM in sandstone reservoirs and thoroughly analyzes the geochemical mechanisms by which OM regulates the transport and precipitation of aqueous uranium. By integrating case studies of representative sandstone uranium deposits globally, three major OM-related metallogenic models are proposed with distinct core characteristics: the humic-dominated model is driven by the complexation and direct reduction of uranium by humic substances/coal-derived OM; the roll-front model relies on reactions between oxidized uranium-bearing fluids and scattered OM, as well as microbially generated sulfides at the migration front; and the seepage-related model is fueled by upward-migrating deep hydrocarbon fluids (petroleum, methane) that act as both uranium carriers and reductants. Furthermore, this review explores the spatial coupling relationships between OM distribution and uranium mineralization in typical geological settings, evaluates the guiding significance of OM for uranium exploration, and outlines key unresolved scientific issues. The findings refine the genetic theoretical framework of sandstone-hosted uranium deposits and provide important technical support and theoretical guidance for future uranium exploration deployment and resource potential evaluation. Full article

(This article belongs to the Special Issue Selected Papers from the 7th National Youth Geological Congress)

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17 pages, 7865 KB

Open AccessArticle

Garnet Geochemistry of the Makeng-Yangshan Fe Skarn Belt, Southeast China: Implications for Contrasting Hydrothermal Systems and Metal Endowment

by Wanyi Feng, Shuting Lei, Bo Xing, Jing Xu and Haibo Yan

Minerals 2025, 15(12), 1325; https://doi.org/10.3390/min15121325 - 18 Dec 2025

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Abstract

The Southwestern Fujian Region is one of the important Fe polymetallic metallogenic belts in China. The Makeng-Yangshan Fe skarn sub-belt within it contains several deposits that share a similar geological setting, mineralization age, and genetic type, yet exhibit significant differences in metal endowment. [...] Read more.

The Southwestern Fujian Region is one of the important Fe polymetallic metallogenic belts in China. The Makeng-Yangshan Fe skarn sub-belt within it contains several deposits that share a similar geological setting, mineralization age, and genetic type, yet exhibit significant differences in metal endowment. To investigate the poorly constrained factors responsible for these differences, this paper focused on the mineral chemistry of garnets associated with magnetite from the Makeng, Luoyang, and Yangshan Fe deposits within the sub-belt, employing in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for trace element analysis. Our results reveal that garnet from all three deposits are andradite-dominated and features a chondrite-normalized REE fractionation pattern exhibiting enrichment in LREE relative to HREE, indicating crystallization from unified, mildly acidic fluids under high oxygen fugacity (f_O2) conditions. However, both the Makeng and Luoyang garnets showed a strong positive Eu anomaly, whereas the Yangshan garnets displayed the weakest Eu anomaly among the three deposits, which can likely be attributed to the highest f_O2 environment of the Yangshan deposit. Furthermore, garnet Y/Ho ratios and Y-ΣREE correlations demonstrate that the Makeng and Luoyang garnets crystallized in an open fluid system that were primarily of magmatic-hydrothermal origin with substantial external fluid (e.g., meteoric water) involvement, whereas the Yangshan garnet reflects a relatively closed fluid system that was predominantly of magmatic-hydrothermal origin with limited external fluid input. These geochemical differences have direct implications for exploration: the open-system Makeng deposit holds promise for Mo-W-Sn mineralization, as does the Luoyang deposit for W-Sn, whereas the closed-system Yangshan shows little potential for these metals. In addition, this study reveals that Pb and Zn concentrations in garnet are not reliable exploration indicators. Overall, these findings provide important mineralogical constraints on the factors controlling deposit scale and metal associations, thereby enhancing the understanding of regional metallogeny and guiding future mineral exploration. Full article

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

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23 pages, 6829 KB

Open AccessArticle

Pore Structure and the Multifractal Characteristics of Shale Before and After Extraction: A Case Study of the Triassic Yanchang Formation in the Ordos Basin

by Zhengwei Xu, Honggang Xin, Zhitao Wang, Shengbin Feng, Wenzhong Ma, Liwen Zhu, Huifei Tao, Lewei Hao and Xiaofeng Ma

Minerals 2025, 15(12), 1324; https://doi.org/10.3390/min15121324 - 18 Dec 2025

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Abstract

The shale oil reservoirs of Member 7 of the Triassic Yanchang Formation in the Longdong Area of the Ordos Basin have attracted widespread attention due to their unique geological characteristics and enormous development potential. As the core factor controlling reservoir storage capacity and [...] Read more.

The shale oil reservoirs of Member 7 of the Triassic Yanchang Formation in the Longdong Area of the Ordos Basin have attracted widespread attention due to their unique geological characteristics and enormous development potential. As the core factor controlling reservoir storage capacity and hydrocarbon flow efficiency, the precise characterization and quantitative analysis of pore structure are the prerequisite and key for reservoir evaluation and development plan optimization. All samples selected in this study were collected from the shale of Member 7 of the Triassic Yanchang Formation and were classified into two categories: medium-organic-rich shales (total organic carbon, TOC: 2–6%; TOC refers to the total organic carbon content in rocks, indicating organic matter abundance; unit: %) and high-organic-rich shales (TOC: >6%). The mineral composition and organic geochemical parameters of the shale were determined via X-ray diffraction (XRD) and Rock-Eval pyrolysis experiments, respectively. Meanwhile, pore structure characteristics were analyzed by combining low-temperature nitrogen adsorption–desorption experiments before and after extraction, and multifractal analysis was used to systematically investigate the differences in pore heterogeneity of shale and their influencing factors. The results show that the specific surface area (SSA) and total pore volume (TPV) of shale increased after extraction, while the change in average pore diameter (APD) varied. Multifractal analysis indicates that the micropores of shale both before and after extraction exhibit significant multifractal characteristics; after extraction, pore connectivity is improved, but the changes in pore heterogeneity are inconsistent. The pore connectivity of shale first increases and then decreases with the increase in TOC content and pyrolysis parameter S₂ content. The better the pore connectivity of shale, the lower the content of light-component saturated hydrocarbons and the relatively higher the content of heavy-component resins in the extractable organic matter (EOM). Brittle minerals can provide a rigid framework to inhibit compaction and are prone to forming natural microfractures under tectonic stress, thereby promoting pore connectivity. In contrast, clay minerals, due to their plasticity, are prone to deformation and filling pore throats during compaction, thus reducing pore connectivity. This study provides a theoretical basis for the evaluation and development of shale reservoirs in the Longdong Area. Full article

(This article belongs to the Special Issue Natural and Induced Diagenesis in Clastic Rock)

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19 pages, 8512 KB

Open AccessArticle

Geochronology and Geochemistry of Granitic Gneisses in the Dabie Orogen, Central China: Constraints on the Petrogenesis of Mid-Neoproterozoic Magmatic Rocks in the Northern Yangtze Block

by Qiao Bai, Yongsheng Wang, Liquan Ma, Xu Zhang and Shuai Zhang

Minerals 2025, 15(12), 1323; https://doi.org/10.3390/min15121323 - 17 Dec 2025

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Abstract

Mid-Neoproterozoic magmatism provides important constraints for revealing the break-up history of the Rodinia supercontinent. Large-sized mid-Neoproterozoic magmatic rocks are distributed within the Dabie Orogen located on the northern Yangtze Block. This study performed zircon LA-ICP-MS geochronology, whole-rock major and trace elements, and zircon [...] Read more.

Mid-Neoproterozoic magmatism provides important constraints for revealing the break-up history of the Rodinia supercontinent. Large-sized mid-Neoproterozoic magmatic rocks are distributed within the Dabie Orogen located on the northern Yangtze Block. This study performed zircon LA-ICP-MS geochronology, whole-rock major and trace elements, and zircon Lu-Hf isotope analyses on orthogneisses with a mid-Neoproterozoic protolith age of the northern Dabie Orogen. The analysis results show that the intrusion times of mid-Neoproterozoic granitoids and mafic rocks are all ~750 Ma, with ε_Hf(t) values ranging from −6.60 to −2.57 and a two-stage Hf model age of ~1.8 Ga. They are characterized by light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion. In the primitive mantle-normalized trace element diagram, these rocks are enriched in La, Ce, Th, K, Zr, Nd, and Sm and depleted in Nb, Ta, P, Ti, and Sr, with negative Eu anomaly or no significant Eu anomaly. Based on the discrimination diagrams, most of the samples are plotted into the A-type granite field, and which was formed in a post-orogenic extension setting. Comprehensive analysis shows that these mid-Neoproterozoic magmatic rocks were produced by melting of juvenile crust of the Paleoproterozoic and late Mesoproterozoic, having a heterogeneous distribution of δ¹⁸O, indicating that these rocks were developed mainly through high-temperature meteoric-hydrothermal alteration during syn-rift magmatic activity. Full article

(This article belongs to the Special Issue Tracing Precambrian Pathways: Neoproterozoic Rocks and Their Global Context)

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24 pages, 5004 KB

Open AccessArticle

Nb-Kaolinite and Nb-TiO₂-Kaolinite for Emerging Organic Pollutant Removal

by Larissa F. Bonfim, Lorrana V. Barbosa, Yan P. Vedovato, Suelen D. de Souza, Hugo F. M. dos Santos, Vinicius F. Lima, Marcus V. do Prado, Eduardo J. Nassar, Katia J. Ciuffi, Lucas A. Rocha, Liziane Marçal and Emerson H. de Faria

Minerals 2025, 15(12), 1322; https://doi.org/10.3390/min15121322 - 17 Dec 2025

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Abstract

This study presents the synthesis and characterization of novel kaolinite niobium and kaolinite titanium niobium nanocomposites and their application as heterogeneous photocatalysts. Utilizing a hydrolytic sol–gel route, we combined kaolinite with isopropyl alcohol, acetic acid, titanium (IV) isopropoxide, and ammonium niobium oxalate, followed [...] Read more.

This study presents the synthesis and characterization of novel kaolinite niobium and kaolinite titanium niobium nanocomposites and their application as heterogeneous photocatalysts. Utilizing a hydrolytic sol–gel route, we combined kaolinite with isopropyl alcohol, acetic acid, titanium (IV) isopropoxide, and ammonium niobium oxalate, followed by heat treatment at 400, 700, and 1000 °C. X-ray diffraction confirmed the retention of kaolinite’s characteristic reflections, with basal spacings indicating the presence of semiconductors on the external surfaces and edges. Heating treatment not allowing the crystallization of anatase until 1000 °C reveals that Nb⁵⁺ could inhibit the transition to titanium crystalline phases (anatase and rutile). The bandgap energies decreased with clay mineral support, averaging 2.50 eV, and absorbing up to 650 nm. The model reaction of terephthalic acid hydroxylation accomplished by photoluminescence spectroscopy demonstrated that KaolTiNb400 presented a higher rate of *OH production, achieving 591 mmol L⁻¹ min⁻¹ compared to pure KaolNb400 173 mmol L⁻¹ min⁻¹. Photodegradation studies revealed significant photocatalytic activity, with the KaolTiNb400 nanocomposite achieving the highest efficiency, demonstrating 90% removal of methylene blue (combining adsorption and degradation) after 24 h of UV light irradiation. These materials also exhibited promising results for the degradation of the antibiotics Triaxon^® (40%) and Loratadine (8%), highlighting their potential for organic pollutants’ removal. In both cases the presence of byproducts is detected. Full article

(This article belongs to the Special Issue Advances in Kaolinite Group Clay Minerals and Their Applications)

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13 pages, 3409 KB

Open AccessArticle

Genetic Features of Variety III Cuboid Diamonds from Placers of the Northeastern Siberian Platform

by Anton Pavlushin, Sargylana Ugapeva, Anastasia Biller and Oleg Oleinikov

Minerals 2025, 15(12), 1321; https://doi.org/10.3390/min15121321 - 17 Dec 2025

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Abstract

This paper presents the results of a comprehensive study of a cuboid diamond of variety III according to the mineralogical classification of Y.L. Orlov, which was first discovered in Carnian (Upper Triassic) deposits of the Bulkur anticline in the northeastern Siberian platform. It [...] Read more.

This paper presents the results of a comprehensive study of a cuboid diamond of variety III according to the mineralogical classification of Y.L. Orlov, which was first discovered in Carnian (Upper Triassic) deposits of the Bulkur anticline in the northeastern Siberian platform. It is established that the crystal has a cubic shape with signs of intense dissolution and is characterized by a zonal–sectorial fibrous internal structure. The central area of the diamond is saturated with microinclusions. The studied cuboid diamond belongs to the IaAB type according to IR spectroscopy data. An accumulation of minerals, which is represented by chamosite (Fe-rich chlorite), quartz, and pyrite, as well as rare native metals (Fe, Cu, and Ag) and intermetallides (chromferide), is present on the diamond surface. The chemical composition and morphology of chamosite indicate its low-temperature hydrothermal–diagenetic origin (50–150 °C, pressure < 1 kbar) in the marine or lagoon sedimentary environment of the rift basin of the Siberian platform during the Triassic. The discovery of a diamond of variety III, characteristic of large industrial kimberlite pipes (Mir, Udachnaya, and Aikhal), in placers of the Leno-Anabar diamond-bearing subprovince indicates a possible unknown primary kimberlite source. Full article

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

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2 pages, 122 KB

Open AccessEditorial

Editorial for Special Issue “Mineralogy, Geochemistry and Fluid Inclusion Study of Gold Deposits Endowed in Critical Metals”

by Grigorios Aarne Sakellaris, Vasilios Melfos, Panagiotis Voudouris and Ferenc Molnár

Minerals 2025, 15(12), 1320; https://doi.org/10.3390/min15121320 - 17 Dec 2025

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Abstract

The high global demand for critical elements required for continuously advancing technologies has intensified the research interest in gold deposits that are enriched in elements such as Te, Se, Bi, Sb, W, and Mo [...] Full article

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

23 pages, 5474 KB

Open AccessArticle

Phosphate Waste Rock Piles as a Secondary Resource: Insights into Composition and Strategic Element Potential

by Mohamed Haidouri, Yassine Ait-Khouia, Abdellatif Elghali, Mustapha El Ghorfi, Mostafa Benzaazoua and Yassine Taha

Minerals 2025, 15(12), 1319; https://doi.org/10.3390/min15121319 - 17 Dec 2025

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Abstract

The growing demand for critical elements vital to the energy transition highlights the need for sustainable secondary sources. Sedimentary phosphate mining generates waste rock known as spoil piles (SPs). These SPs retain valuable phosphate and other critical elements such as rare earth elements [...] Read more.

The growing demand for critical elements vital to the energy transition highlights the need for sustainable secondary sources. Sedimentary phosphate mining generates waste rock known as spoil piles (SPs). These SPs retain valuable phosphate and other critical elements such as rare earth elements (REEs). This study examines the potential of recovering these elements from SPs. A comprehensive sampling strategy was implemented, and a 3D topographic model was generated using drone imagery data. The model revealed that these SPs cover an area estimated at 48,633,000 m², with a total volume of approximately 419,612,367 m³. Chemical analyses using X-ray fluorescence and inductively coupled plasma mass spectrometry techniques indicated valuable phosphate content, with an overall concentration of 12.6% P₂O₅ and up to 20.7% P₂O₅ in the fine fraction (<1 mm). The concentrations of critical and strategic elements in the SPs were as follows: magnesium [1%–8%], REEs [67–267 ppm], uranium [48–173.5 ppm], strontium [312–1090 ppm], and vanadium [80–150 ppm]. Enrichment factors showed that these elements are highly concentrated in fine fractions, with values exceeding 60 for Y, 40 for Sr, and 780 for U in the +125/−160 µm fraction. A positive correlation was observed between these elements and phosphorus, except for magnesium. Automated mineralogy confirmed that the fine fraction (<1 mm) contains more than 50% carbonate-fluorapatite (CFA), alongside major gangue minerals such as carbonates and silicates. These findings demonstrate the potential for sustainable recovery of phosphate, magnesium, REEs, strontium, vanadium, and uranium from phosphate mining waste rock. Full article

(This article belongs to the Special Issue Critical Minerals for Energy Transition: Advancing Energy Security and Sustainable Manufacturing)

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16 pages, 3492 KB

Open AccessArticle

The Migration Phenomenon of Metal Cations in Vein Quartz at Elevated Temperatures

by Zhenxuan Wang, Hongjuan Sun, Bo Liu, Yehao Huang and Tongjiang Peng

Minerals 2025, 15(12), 1318; https://doi.org/10.3390/min15121318 - 17 Dec 2025

Viewed by 250

Abstract

With the rapid development of the photovoltaic (PV) and semiconductor fields, the reserves of traditional high-purity quartz raw materials can no longer meet the demands of various industries, creating an urgent need to develop new types of high-purity quartz feedstock. In this study, [...] Read more.

With the rapid development of the photovoltaic (PV) and semiconductor fields, the reserves of traditional high-purity quartz raw materials can no longer meet the demands of various industries, creating an urgent need to develop new types of high-purity quartz feedstock. In this study, three groups of vein quartz samples from different mining areas were subjected to calcination at 950 °C for 2 h. The impurity states of the vein quartz before and after calcination were characterized using XRD, ICP, Raman and XRF. The migration behavior of metal cations in vein quartz under high-temperature conditions was systematically investigated, and the structural changes in the vein quartz before and after calcination were discussed from the perspectives of impurity element distribution and phase transformation. The results demonstrate that impurity cations in vein quartz migrate from the interior to the surface of the material under high-temperature environments. Quantitative ICP analysis of the inner and outer layers of the quartz samples before and after calcination revealed that, among the three groups, the surface impurity cation content of the sample with the most pronounced migration effect reached four times that of its internal structure. Combined with other characterization techniques, it was confirmed that after the cation migration process, the vein quartz samples exhibited a layered structure from the surface to the interior: a hematite mineralized layer, a high lattice impurity layer, and a low lattice impurity layer. This indicates that high-purity vein quartz with low lattice impurity content can be obtained by subjecting quartz to high-temperature calcination and subsequently removing the mineralized layer and the surface high lattice impurity layer. Consequently, vein quartz of ordinary quality can also be converted into high-purity quartz raw material of 4N grade or higher through the processes of cation migration and tailing removal. Full article

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

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23 pages, 6609 KB

Open AccessArticle

Study on Efficient Separation of Amorphous Silica from High-Alumina Coal Gangue

by Jingnan Hong, Weibing Ma, Hongwei Zhang and Naihe Yi

Minerals 2025, 15(12), 1317; https://doi.org/10.3390/min15121317 - 16 Dec 2025

Viewed by 218

Abstract

Coal gangue, a major industrial solid waste from coal mining and processing, requires efficient alumina and silica separation for high-value utilization. This study focused on mineral reaction mechanisms and characteristics of coal gangue during calcination and alkaline leaching. Results showed calcination at 900–1200 [...] Read more.

Coal gangue, a major industrial solid waste from coal mining and processing, requires efficient alumina and silica separation for high-value utilization. This study focused on mineral reaction mechanisms and characteristics of coal gangue during calcination and alkaline leaching. Results showed calcination at 900–1200 °C altered its phase composition, affecting silica separation efficiency, with the optimal calcination range being 960–1120 °C. Poorly crystallized mullite and Al₂O₃ in calcined gangue were insoluble under low-alkaline and low-temperature conditions. On the contrary, amorphous silica is soluble and forms a sodium silicate solution in the proper alkaline conditions. This characteristic facilitates the efficient separation of alumina and silica. It was determined that the suitable conditions for silica removal from coal gangue are as follows: 1080 °C calcination for 90 min, leaching at 75 °C with 200 g/L NaOH (solid–liquid ratio of 1:4) for 4 h. Under these selected conditions, the silica leaching efficiency was 77.31%, the alumina leaching efficiency was 12.21%, the Na₂O content in the leached residue was 1.94%, and the mass ratio of alumina to silica (A/S) in the leached residue increased from 0.88 to 3.42. A potential desilication mechanism was also analyzed. Full article

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

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18 pages, 2550 KB

Open AccessArticle

A Raman Measurement and Pre-Processing Method for the Fast In Situ Identification of Minerals

by Dhiraj Gokuladas, Julia Sohr, Andreas Siegfried Braeuer and Daniela Freyer

Minerals 2025, 15(12), 1316; https://doi.org/10.3390/min15121316 - 16 Dec 2025

Viewed by 257

Abstract

Through this work, an experimental setup and pre-processing method for obtaining fluorescence and quasi-noise-free Raman spectra of minerals for in situ mineral identification in an underground environment is proposed. It uses a combination of methodologies like dual excitation wavelengths, Shifted Excitation Raman Difference [...] Read more.

Through this work, an experimental setup and pre-processing method for obtaining fluorescence and quasi-noise-free Raman spectra of minerals for in situ mineral identification in an underground environment is proposed. It uses a combination of methodologies like dual excitation wavelengths, Shifted Excitation Raman Difference Spectroscopy (SERDS), and deep learning-based U-Net model for background and noise correction. The dual excitation wavelengths technique employs a near-infrared SERDS laser for the fingerprint and a red laser for the large Raman shift region. The SERDS laser operates at two excitation wavelengths and is tuneable in the vicinity of 785 nm. The red laser uses 671 nm excitation wavelength. The obtained fingerprint and large Raman shift Raman spectra are then fed to a pre-processing method containing the trained U-Net model for obtaining a background-corrected and quasi-noise-free Raman spectrum. The proposed method addresses issues of existing handheld Raman systems in terms of spectrometer sensitivity, spectrum acquisition speed, pre-processing time, fluorescence effects, and other interferences due to surrounding light or vibration. The obtained final processed Raman spectrum is then deconstructed into pseudo-Voigt peaks. The identification of the minerals can be based on the number and the positions of the pseudo-Voigt peaks. Samples of gypsum (CaSO₄·2H₂O) and anhydrite (CaSO₄) were used for evaluating the performance of the proposed method. The influence of measurement time on the reproducibility and precision of the peak identification and, thus, mineral identification is also analyzed. Full article

(This article belongs to the Special Issue Mineralogical and Geochemical Characterization of Geological Materials, 2nd Edition)

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22 pages, 17264 KB

Open AccessArticle

Comparative Study on Pore Characteristics and Methane Adsorption Capacity of Shales with Different Levels of Tectonic Deformation: A Case Study of Longmaxi Shales in Fuling Field

by Xiaoming Zhang, Changcheng Han, Lanpu Chen, Qinhong Hu, Zhiguo Shu, Di Wang, Xidong Wang, Qian Feng and Yuzuo Liu

Minerals 2025, 15(12), 1315; https://doi.org/10.3390/min15121315 - 16 Dec 2025

Viewed by 254

Abstract

Tectonic deformation can substantially change the pore characteristics and the resulting methane adsorption capacity of shales; thus, it strongly influences shale gas exploration and development in structurally complex areas of southern China. Two sets of shales with identical lithofacies that were derived from [...] Read more.

Tectonic deformation can substantially change the pore characteristics and the resulting methane adsorption capacity of shales; thus, it strongly influences shale gas exploration and development in structurally complex areas of southern China. Two sets of shales with identical lithofacies that were derived from either structurally stable or deformed regions were collected at Fuling Field to evaluate the response of their pore properties and methane adsorption behavior to tectonic deformation through field emission scanning electron microscopy (FE-SEM), low-pressure gas (CO₂/N₂) adsorption, and high-pressure methane adsorption experiments. Three primary shale lithofacies were identified in each set of shales: organic-lean (OL) siliceous-rich argillaceous (CM-1) shale lithofacies, organic-moderate (OM) argillaceous/siliceous mixed (M-2) shale lithofacies, and organic-rich (OR) argillaceous-rich siliceous (S-3) shale lithofacies. In the stable region, organic matter (OM) pores dominated the pore types of OR S-3 shales, whereas the primary pore types of OL CM-1 shales were clay cleavage micro-fractures. OM M-2 shales exhibited a composite type of OM pores and clay cleavage micro-fractures. Compared with structurally stable shales, the original OM-hosted and clay-related pores in structurally deformed shales were extensively compacted or even closed due to tectonic compression during structural deformation. Despite pore collapse, two new types of tectonic micro-fractures were generated and found to be well developed in deformed shales through the rupture of brittle minerals in OR S-3 shales and the deformation of clay minerals in OL CM-1 shales. Simultaneously, organic matter–clay aggregates that formed during tectonic compression constituted a distinctive structure in deformed OM M-2 shales. As a result, the deformed shales displayed a decrease in their micropore and mesopore volumes, as well as a decrease in their pore surface areas, because of strong tectonic compression accompanied by an increase in the macropore volume due to the development of tectonic micro-fractures. Furthermore, the large pore surface areas in structurally stable shales could supply abundant adsorption sites and facilitate the enrichment of adsorbed gas. The expanded macropore volumes in structurally deformed shales could provide more storage spaces that are favorable for the accumulation of free gas. Full article

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

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34 pages, 11631 KB

Open AccessArticle

Differential Karst Control of Carbonate Reservoirs: A Case Study of the Fourth Member of Sinian Dengying Formation in Gaoshiti-Moxi, Sichuan Basin, SW China

by Guoquan Nie, Dengfa He, Qingyu Zhang, Xiaopan Li, Shaocong Ji, Guochen Mo and Meng Zhang

Minerals 2025, 15(12), 1314; https://doi.org/10.3390/min15121314 - 16 Dec 2025

Viewed by 219

Abstract

The dolomite of the fourth member of Dengying Formation in Gaoshiti-Moxi area of central Sichuan Basin is rich in hydrocarbon resources. It has experienced superimposition-reformation of multistage karstification, and is the key target for studying deep ancient carbonate reservoirs. Exploration and development practices [...] Read more.

The dolomite of the fourth member of Dengying Formation in Gaoshiti-Moxi area of central Sichuan Basin is rich in hydrocarbon resources. It has experienced superimposition-reformation of multistage karstification, and is the key target for studying deep ancient carbonate reservoirs. Exploration and development practices show that there are great differences in the development of karst reservoirs of the fourth member of Dengying Formation between the platform margin and intraplatform in Gaoshiti-Moxi area. However, the differences in the genetic mechanism of karst reservoirs between these two zones are unclear. Therefore, based on an integrated analysis of core, thin section, drilling, logging, and geochemical test data, this study clarifies the differences in karstification between the platform margin and intraplatform and conducts a comparative analysis of the controlling factors for the differences in karst reservoirs. Results show that the fourth member of Dengying Formation experienced superimposition-reformation of four types of paleokarstification, including eogenetic meteoric water karst, supergene karst, coastal mixed water karst, and burial karst. Large-scale dissolved fractures and caves are mainly controlled by meteoric water karstification, primarily developing three types of reservoir space: vug type, fracture-vug type, and cave type. Dolomite and quartz fillings are mainly formed in the medium-deep burial period. Four types of paleokarstification are developed in the platform margin, while the coastal mixed water karst is not developed in the intraplatform. Eogenetic meteoric water karst and supergene karst in the platform margin are stronger than those in the intraplatform, while burial karst shows no notable difference between the two zones. The thickness of soluble rock (mound-shoal complex), karst paleogeomorphology, and different types of paleokarstification are the main controlling factors for the difference in karst reservoirs between the platform margin and the intraplatform. Full article

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

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28 pages, 11338 KB

Open AccessArticle

Quantitative Prediction and Assessment of Copper Deposits in Northwestern Hubei Based on the Fuzzy Weight-of-Evidence Model

by Hongtao Shi, Shuyun Xie, Hong Luo and Xiang Wan

Minerals 2025, 15(12), 1313; https://doi.org/10.3390/min15121313 - 16 Dec 2025

Viewed by 330

Abstract

The northwestern Hubei region, primarily encompassing Shiyan City and Yunxi County in Hubei Province, constitutes a crucial component of the South Qinling Tectonic Belt. The Neoproterozoic Wudang Group in the study area exhibits Cu element enrichment, with ore deposit formation closely associated with [...] Read more.

The northwestern Hubei region, primarily encompassing Shiyan City and Yunxi County in Hubei Province, constitutes a crucial component of the South Qinling Tectonic Belt. The Neoproterozoic Wudang Group in the study area exhibits Cu element enrichment, with ore deposit formation closely associated with stratigraphic and structural features. This study evaluates copper mineral resource distribution and metallogenic potential in northwestern Hubei by employing factor analysis, concentration-area fractal modeling, and the fuzzy weights-of-evidence method based on stream sediment data, aiming to construct a metallogenic potential model. Factor analysis was applied to process 2002 stream sediment samples of 32 elements to identify principal factors related to copper mineralization. Inverse distance interpolation was used to generate element distribution maps of principal factors, which were integrated with geological and structural data to establish a model using the fuzzy weights of evidence method. Prediction results indicate that most known copper deposits are located within posterior favourability ranges of 0.0027–0.272, constrained by stratigraphic and fault controls. The central northwestern Hubei region is identified as a priority target for future copper exploration. This research provides methodological references for conducting mineral resource potential assessments in north-western Hubei using innovative evaluation approaches. Full article

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

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16 pages, 2782 KB

Open AccessArticle

Apatite Geochemistry of the Slyudyanka Deposit, Siberia: Trace Element Composition, Y/Ho Anomaly, and Multivariate Statistical Analysis for Genetic Classification

by Artem S. Maltsev, Alena N. Zhilicheva, Leonid Z. Reznitskii and Alexei V. Ivanov

Minerals 2025, 15(12), 1312; https://doi.org/10.3390/min15121312 - 16 Dec 2025

Viewed by 261

Abstract

Apatite is a key indicator mineral whose chemical signature can reveal the genesis and evolution of ore-forming systems. However, correctly interpreting these signatures requires a robust discrimination between apatite types formed by different geological processes, such as metamorphism and hydrothermal activity. This study [...] Read more.

Apatite is a key indicator mineral whose chemical signature can reveal the genesis and evolution of ore-forming systems. However, correctly interpreting these signatures requires a robust discrimination between apatite types formed by different geological processes, such as metamorphism and hydrothermal activity. This study aims to chemically characterize and genetically classify apatite samples from the Slyudyanka deposit (Siberia, Russia) to establish discriminative geochemical fingerprints for metamorphic and hydrothermal apatite types. We analyzed 80 samples of apatite using total reflection X-ray fluorescence (TXRF) and inductively coupled plasma mass spectrometry (ICP-MS). The geochemical data were processed using principal component analysis (PCA) and k-means cluster analysis to objectively discriminate the apatite types. Our analysis reveals three distinct geochemical groups. Metamorphic veinlet apatite is defined by high U and Pb, low REE, Sr, and Th, and suprachondritic Y/Ho ratios. Massive metamorphic apatite from silicate–carbonate rocks shows extreme REE enrichment and chondritic Y/Ho ratios. Hydrothermal–metasomatic apatite features high Sr, Th, and As, with intermediate REE concentrations and chondritic Y/Ho ratios. Furthermore, we validated the critical and anomalous Y concentrations in the metamorphic veinlet apatite by cross-referencing TXRF and ICP-MS data, confirming the reliability of our measurements for this monoisotopic element. We successfully established diagnostic geochemical fingerprints that distinguish apatite formed in different geological environments at Slyudyanka. The anomalous Y/Ho ratio in metamorphic veinlet apatite serves as a key discriminant and provides insight into specific fractionation processes that occurred during the formation of phosphorites in oceanic environments, which later transformed to apatites during high-grade metamorphism without a change in the Y/Ho ratio. This work underscores the importance of multi-method analytical validation for accurate geochemical classification. Full article

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

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9 pages, 576 KB

Open AccessCommunication

Measurement and Modeling of Residence Time Distribution in a G-06 Imhoflot^TM Cell

by Ahmad Hassanzadeh, Mustafa Guner, Ekin Gungor, Doruk Drunesil and Asghar Azizi

Minerals 2025, 15(12), 1311; https://doi.org/10.3390/min15121311 - 16 Dec 2025

Viewed by 197

Abstract

Although intensified flotation cells have been introduced as fast-kinetic and plug-flow-type flotation machines, there is limited empirical verification and information about their fluid flow patterns and dispersion regimes. The present communication paper investigates this for an Imhoflot^TM G-06 cell operated in an [...] Read more.

Although intensified flotation cells have been introduced as fast-kinetic and plug-flow-type flotation machines, there is limited empirical verification and information about their fluid flow patterns and dispersion regimes. The present communication paper investigates this for an Imhoflot^TM G-06 cell operated in an open-circuit mode using an impulse method to measure and model the residence time of a liquid–gas system. For experimental measurements, a concentrated KCl solution was employed, and water conductivity was monitored for 20 min. By fitting several relevant models, such as large and small tanks in series (LSTS), Weller, N-Mixer, and perfect mixer, to the experimental data, it was revealed that the N-Mixer represented the dispersion pattern the best (N = 1.3–1.6). Further, the obtained practical mean retention time (MRT) of 4.11 ± 0.16 min was somewhat aligned with the theoretical value, i.e., 5.0 min per pass, indicating a back-calculated gas hold-up magnitude of 18%–22% in the separator. These results provide an in-depth perception of scale-up procedures and requirements for cell modification. Full article

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

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3 pages, 135 KB

Open AccessCorrection

Correction: Wang et al. Age, Genesis, and Tectonic Setting of the Serbian Čukaru Peki Copper Deposit in Timok Ore Cluster Area, Eastern Europe: Constraints from Zircon U-Pb Dating, Pyrite Re-Os Dating, and Geochemical Data. Minerals 2025, 15, 1178

by Zhuo Wang, Haixin Yue, Datian Wu, Dongping Rao, Fengming Xu, Wei Sun, Wensong Lang, Zhengze Yu, Yongheng Zhou, Weishan Huang, Yunchou Xu, Zhenjun Sun and Xin Jin

Minerals 2025, 15(12), 1310; https://doi.org/10.3390/min15121310 - 16 Dec 2025

Viewed by 139

Abstract

The title in the original publication [...] 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)

25 pages, 4815 KB

Open AccessArticle

Performance Evaluation of an Activated Greek Palygorskite in High-Salinity and High-Hardness Water-Based Drilling Fluids

by Dimitrios Papadimitriou, Ernestos Nikolas Sarris and Nikolaos Kantiranis

Minerals 2025, 15(12), 1309; https://doi.org/10.3390/min15121309 - 15 Dec 2025

Viewed by 167

Abstract

The performance of conventional bentonite-based drilling fluids is severely compromised in high-salinity and high-hardness brines, creating a need for salt-tolerant viscosifiers. This work provides a comprehensive performance evaluation of an activated palygorskite sourced from the Ventzia basin in Greece to be used as [...] Read more.

The performance of conventional bentonite-based drilling fluids is severely compromised in high-salinity and high-hardness brines, creating a need for salt-tolerant viscosifiers. This work provides a comprehensive performance evaluation of an activated palygorskite sourced from the Ventzia basin in Greece to be used as a high-performance additive for water-based drilling fluids. Six raw clay samples were mechanically processed and activated via extrusion and chemically treated with 2.25% MgO. Their rheological behavior and filtration properties were systematically investigated in three aqueous environments, (i) deionized water, (ii) API-standard salt water, and (iii) API-standard high-hardness salt water. The performance was benchmarked against that of commercial palygorskite products. The results demonstrated that the selected activated Greek samples exhibited excellent rheological properties, including higher viscosity, yield point, and thixotropic gel strength, comparable to those of the commercial benchmark. While the fluid’s rheology was suppressed by increasing salinity due to the flocculation of co-existing smectite, the best-performing Greek clays maintained a significant advantage, developing exceptionally robust gel structures critical for solid suspension in harsh conditions. Crucially, the same smectite flocculation mechanism proved highly beneficial for filtration control, leading to a significant reduction in fluid loss and the formation of a thin filter cake, particularly with the high-hardness brine. The findings confirm that activated Greek palygorskite is a technically viable, high-performance alternative to imported commercial materials, offering a sustainable solution for formulating resilient drilling fluids for challenging environments. Full article

(This article belongs to the Special Issue Alkali Activation of Clay-Based Materials)

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19 pages, 1146 KB

Open AccessReview

Radionuclide Removal in Rare Earth Mineral Processing: A Review of Existing Methods and Emerging Biochemical Approaches Using Siderophores

by Emmanuel Atta Mends and Pengbo Chu

Minerals 2025, 15(12), 1308; https://doi.org/10.3390/min15121308 - 15 Dec 2025

Viewed by 283

Abstract

The extraction of rare earth elements is becoming increasingly essential due to their many applications in current and emerging advanced material technologies. However, in many rare earth deposits, rare earth minerals are associated with radionuclides; specifically, thorium and uranium. The radioactive nature of [...] Read more.

The extraction of rare earth elements is becoming increasingly essential due to their many applications in current and emerging advanced material technologies. However, in many rare earth deposits, rare earth minerals are associated with radionuclides; specifically, thorium and uranium. The radioactive nature of these elements is a major concern during processing. Techniques such as solvent extraction and precipitation have been employed in this regard to minimize the radioactivity levels and address any related processing or environmental concerns. However, they face various challenges such as high chemical reagent consumption, secondary waste generation, and limited selectivity, which hinder either their scalability or sustainability. The current study provides a literature review about these technologies to provide critical insights on their applications and discuss the challenges hampering their extensive use in the mining industry. Biotechnology is also evaluated and highlighted as a promising, cost-effective, and low-environmental-impact option for the selective recovery of radionuclides from rare earth elements. Specifically, pyoverdine siderophores were discussed due to their catecholates and hydroxamate moieties which have high affinity for radionuclides to enhance selective recovery during rare earth processing. Conversely, integration of this approach into existing mineral processing flowsheets is a constraint. Hence, future studies should focus on optimizing the kinetics of siderophore synthesis and explore a hybrid approach to combine the biotechnological and conventional techniques. Full article

(This article belongs to the Special Issue Radionuclides and Radiation Exposure in Minerals Extraction, Processing and Applications)

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11 pages, 1614 KB

Open AccessArticle

Study on the Crystal Structure and Electronic Properties of Tennantite and Enargite

by Dong Yang, Yuqiong Li, Faqi Qu, Meiguang Jiang, Ciren Quni, Wenjie Zhang, Jianhua Chen and Yuxin Guo

Minerals 2025, 15(12), 1307; https://doi.org/10.3390/min15121307 - 15 Dec 2025

Viewed by 211

Abstract

Tennantite (Cu₁₂As₄S₁₃) and enargite (Cu₃AsS₄) are two important minerals that simultaneously contain copper and arsenic. Detailed studies of their structure and properties are crucial for understanding their oxidation, flotation, and leaching. This study [...] Read more.

Tennantite (Cu₁₂As₄S₁₃) and enargite (Cu₃AsS₄) are two important minerals that simultaneously contain copper and arsenic. Detailed studies of their structure and properties are crucial for understanding their oxidation, flotation, and leaching. This study investigates the crystal structures, electronic properties, and reactivity of these two copper-arsenic minerals from the perspectives of atomic bonding, charge, density of states, and d-orbital splitting. The results indicate that tennantite is a crystal with mixed Cu valence states of +2 and +1 (predominantly +1), while the Cu in enargite is in the +1 state. The valence state of As in tennantite (+3) is lower than that in enargite (+5). Orbital energy level calculations show that the energy gaps between the copper d-orbitals are small in both minerals, indicating strong electron delocalization and, consequently, strong covalent character in the crystals, which is also confirmed by Mulliken bond population calculations. The presence of arsenic is the reason for the enhanced covalency. It is noteworthy that tennantite exhibits stronger covalency. The Cu 3d and As 4p electrons in tennantite are more electronically active than those in enargite. In tennantite, the strong d-electron delocalization caused by d-p hybridization between Cu and S leads to similar 3d electronic properties between 3-coordinated and 4-coordinated Cu. The energies of the five d-orbitals of the 4-coordinated Cu in enargite are lower than those of the 4-coordinated Cu in tennantite, which may affect the ability of Cu 3d electrons to enter the empty orbitals of S atoms in sulfur-containing collectors to form π back-bonding, thereby reducing the collecting ability of enargite. On the other hand, the splitting energy of the 4-coordinated Cu 3d orbitals in enargite is significantly smaller than that in tennantite, making the structure less stable and, thus, potentially more prone to dissolution. Full article

(This article belongs to the Special Issue Harnessing Surface Chemistry for Enhanced Mineral Recovery)

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20 pages, 23508 KB

Open AccessArticle

Petrogenesis of Himalayan Leucogranites: A Perspective from Zircon Trace Elements

by Weirui Lu, Zeming Zhang, Jia Yuan, Yang Zhang, Qiang Li, Yu An and Di Zhan

Minerals 2025, 15(12), 1306; https://doi.org/10.3390/min15121306 - 15 Dec 2025

Viewed by 278

Abstract

Magmatic zircon trace element compositions and their variation trends provide valuable insights into the nature and evolutionary processes of magmatic rocks. The Himalayan orogen contains widespread leucogranites. Despite extensive studies on these granites, the features and petrogenetic implications of trace element composition of [...] Read more.

Magmatic zircon trace element compositions and their variation trends provide valuable insights into the nature and evolutionary processes of magmatic rocks. The Himalayan orogen contains widespread leucogranites. Despite extensive studies on these granites, the features and petrogenetic implications of trace element composition of zircons from the leucogranites remain poorly constrained. In this study, we present a comprehensive dataset comprising new cathodoluminescence (CL) images, U-Pb ages, and trace element compositions of zircons from the Himalayan leucogranites, and compare them to the previously reported trace element data of zircon from I-type granites. Our results show that zircons from the Himalayan leucogranites have high Hf, U, Y, P, Th, Sc, and heavy rare earth element contents (HREE), and low Nb, Ta, Ti, and light rare earth element contents (LREE), and can be divided into two types. Type I (low-U) zircons exhibit well-developed oscillatory zoning, and the U concentrations are mostly <5000 ppm. Type II (high-U) zircons display mottled or spongy textures and possess elevated U contents that are mostly >5000 ppm. Zircons from the Himalayan leucogranites have higher contents of U, Hf, Nb, Ta, and elevated U/Yb ratios, but lower Th/U, Eu/Eu*, Ce/Ce*, LREE/HREE, and Ce/U values than those from I-type granitic zircons. Furthermore, zircons in the Himalayan leucogranites have gradually decreasing Th, Ti, Th/U, Eu/Eu*, and Ce/Ce*, and increasing U, Nb, Ta, and (Yb/Gd)_N with increasing Hf. These geochemical features suggest the magmas involved in the genesis of leucogranites originated from the partial melting of metasedimentary sources under relatively reduced conditions, and underwent a high degree of magmatic fractionation. Full article

(This article belongs to the Special Issue Tracing Precambrian Pathways: Neoproterozoic Rocks and Their Global Context)

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16 pages, 7787 KB

Open AccessArticle

Advanced 3D Inversion of Airborne EM and Magnetic Data with IP Effects and Remanent Magnetization Modeling: Application to the Mpatasie Gold Belt, Ghana

by Michael S. Zhdanov, Leif H. Cox, Michael Jorgensen and Douglas H. Pitcher

Minerals 2025, 15(12), 1305; https://doi.org/10.3390/min15121305 - 15 Dec 2025

Viewed by 398

Abstract

We present an integrated methodology for three-dimensional inversion of large-scale airborne electromagnetic (AEM) and magnetic survey data that simultaneously recovers electrical conductivity, chargeability, and both induced and remanent magnetizations. A central feature of the AEM component is the explicit incorporation of induced polarization [...] Read more.

We present an integrated methodology for three-dimensional inversion of large-scale airborne electromagnetic (AEM) and magnetic survey data that simultaneously recovers electrical conductivity, chargeability, and both induced and remanent magnetizations. A central feature of the AEM component is the explicit incorporation of induced polarization (IP) effects. Neglecting IP responses can lead to biased conductivity models, particularly in mineralized systems where disseminated sulfides contribute strongly to chargeability. Using the Generalized Effective-Medium Theory of Induced Polarization (GEMTIP), the inversion produces physically consistent 3D distributions of conductivity and chargeability. To enhance magnetic interpretation, we also implement a vector magnetic inversion that resolves both induced and remanent magnetization from Total Magnetic Intensity (TMI) data, enabling geologically realistic magnetization models in terranes with significant remanence. This integrated workflow was applied to airborne AEM and TMI datasets collected over the Asankrangwa Gold Belt in central Ghana. The inversion results delineate a key exploration target defined by coincident magnetic low and elevated chargeability, interpreted as sulfide-rich gold mineralization and subsequently confirmed by drilling. These results demonstrate that jointly accounting for IP and remanent magnetization in 3D inversion substantially improves subsurface characterization and provides a powerful tool for mineral exploration in structurally and lithologically complex environments. Full article

(This article belongs to the Special Issue Feature Papers in Mineral Exploration Methods and Applications 2025)

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22 pages, 7963 KB

Open AccessArticle

Thermal, Structural, and Phase Evolution of the Y₂(SO₄)₃*8H₂O–Eu₂(SO₄)₃*8H₂O System via Dehydration and Volatilization to Y₂(SO₄)₃–Eu₂(SO₄)₃ and Y₂O₂(SO₄)–Eu₂O₂(SO₄) and Its Thermal Expansion

by Andrey P. Shablinskii, Olga Y. Shorets, Rimma S. Bubnova, Maria G. Krzhizhanovskaya, Margarita S. Avdontceva and Stanislav K. Filatov

Minerals 2025, 15(12), 1304; https://doi.org/10.3390/min15121304 - 14 Dec 2025

Viewed by 276

Abstract

The synthesis, crystal structure, phase transformations, and thermal expansion of (Y_1−xEu_x)₂(SO₄)₃*8H₂O (where x = 0, 0.17, 0.33, 0.50, 0.66, 0.83, and 1) are presented. (Y_1−xEu_x) [...] Read more.

The synthesis, crystal structure, phase transformations, and thermal expansion of (Y_1−xEu_x)₂(SO₄)₃*8H₂O (where x = 0, 0.17, 0.33, 0.50, 0.66, 0.83, and 1) are presented. (Y_1−xEu_x)₂(SO₄)₃*8H₂O solid solutions were synthesized via crystallization from an aqueous solution. (Y_1−xEu_x)₂(SO₄)₃*8H₂O (C2/c) ↔ (Y_1−xEu_x)₂(SO₄)₃ (Pbcn) → (Y_1−xEu_x)₂O₂SO₄ (C2/c) and Eu₂(SO₄)₃*8H₂O (C2/c) ↔ Eu₂(SO₄)₃ (C2/c) → Eu₂O₂SO₄ (C2/c) phase transformations for all samples were investigated by high-temperature powder X-ray diffraction, differential scanning calorimetry and thermogravimetry in the temperature ranges of 25–750 and 25–1350 °C, respectively. The aim of this work is to identify the structural heredity of the phases formed during thermal transformations of (Y_1−xEu_x)₂(SO₄)₃*8H₂O solid solutions, and to study the mechanisms of the thermal deformations of the crystal structure. Structural relations between these phases were found. The crystal structures of YEu(SO₄)₃*8H₂O and (Y_0.83Eu_0.17)₂(SO₄)₃*8H₂O were refined at −173, −123, −73, −23, 27, and 77 °C. Thermal expansion coefficients for (Y_1−xEu_x)₂(SO₄)₃*8H₂O, Eu₂(SO₄)₃, (Y_1−xEu_x)₂O₂SO₄ (where x = 0, 0.17, 0.33, 0.50, 0.66, 0.83, and 1) compounds and solid solutions were calculated for the first time. The thermal expansion of Eu₂(SO₄)₃ was highest in the direction approximately coinciding with the c-axis, because the Eu–O chains extended in this direction. As temperature increased, the crystal structure of (Y_1−xEu_x)₂(SO₄)₃*8H₂O expanded significantly in the ac plane along directions close to the a and c axes, while thermal expansion along the b axis was relatively low. The distance between layers in the (Y_1−xEu_x)₂(SO₄)₃*8H₂O crystal structure increased with increasing temperature, and corrugated layers (parallel to (101) direction) straightened out due to the rotation of the S₂O₄ tetrahedra. At high temperature, thermal expansion of Y₂O₂SO₄ was highest along the longer diagonal of the ac parallelogram perpendicular to the plane of the oxo-centered

\frac{2}{\infty}

[YO] layers. Full article

(This article belongs to the Special Issue Crystal Chemistry of Sulfate Minerals and Synthetic Compounds)

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22 pages, 6432 KB

Open AccessArticle

Minerals as Windows into Habitability on Lava Tube Basalts: A Biogeochemical Study at Lava Beds National Monument, CA

by Dina M. Bower, Amy C. McAdam, Clayton S. C. Yang, Feng Jin, Maeva Millan, Clara Christiann, Mathilde Mussetta, Christine Knudson, Jamielyn Jarvis, Sarah Johnson, Zachariah John, Catherine Maggiori, Patrick Whelley and Jacob Richardson

Minerals 2025, 15(12), 1303; https://doi.org/10.3390/min15121303 - 14 Dec 2025

Viewed by 338

Abstract

Lava tubes on Earth provide unique hydrogeological niches for life to proliferate. Orbital observations of the Martian surface indicate the presence of lava tubes, which could hold the potential for extant life or the preservation of past life within a subsurface environment protected [...] Read more.

Lava tubes on Earth provide unique hydrogeological niches for life to proliferate. Orbital observations of the Martian surface indicate the presence of lava tubes, which could hold the potential for extant life or the preservation of past life within a subsurface environment protected from harsh conditions or weathering at the surface. Secondary minerals in lava tubes form as a combination of abiotic and biotic processes. Microbes colonize the surfaces rich in these secondary minerals, and their actions induce further alteration of the mineral deposits and host basalts. We conducted a biogeochemical investigation of basaltic lava tubes in the Medicine Lake region of northern California by characterizing the compositional variations in secondary minerals, organic compounds, microbial communities, and the host rocks to better understand how their biogeochemical signatures could indicate habitability. We used methods applicable to landed Mars missions, including Raman spectroscopy, X-ray diffraction (XRD), Laser-Induced Breakdown Spectroscopy (LIBS), and gas chromatography–mass spectrometry (GC-MS), along with scanning electron microscopy (SEM) and metagenomic DNA/RNA sequencing. The main secondary minerals, amorphous silicates, and calcite, formed abiotically from the cave waters. Two types of gypsum, large euhedral grains with halites, and cryptocrystalline masses near microbial material, were observed in our samples, indicating different formation pathways. The cryptocrystalline gypsum, along with clay minerals, was associated with microbial materials and biomolecular signatures among weathered primary basalt minerals, suggesting that their formation was related to biologic processes. Some of the genes and pathways observed indicated a mix of metabolisms, including those involved in sulfur and nitrogen cycling. The spatial relationships of microbial material, Cu-enriched hematite in the host basalts, and genetic signatures indicative of metal cycling also pointed to localized Fe oxidation and mobilization of Cu by the microbial communities. Collectively these results affirm the availability of bio-essential elements supporting diverse microbial populations on lava tube basalts. Further work exploring these relationships in lava tubes is needed to unravel the intertwined nature of abiotic and biotic interactions and how that affects habitability in these environments on Earth and the potential for life on Mars. Full article

(This article belongs to the Special Issue Exploring Novel Interactions Between Microbes and Minerals)

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Open AccessArticle

Mineralogical and Geochemical Insights into Formation of the Muji Carbonic Springs, NW China

by Li Zhang, Yuxin Guo, Guodong Zheng, Yuanyuan Shao, Alireza K. Somarin, Vasilii Lavrushin and Xiangxian Ma

Minerals 2025, 15(12), 1302; https://doi.org/10.3390/min15121302 - 13 Dec 2025

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Abstract

The Muji carbonic springs on the northeastern margin of the Pamir Plateau provide a natural window into tectonically controlled CO₂ degassing within a continental collision zone. Through mineralogical and geochemical analyses, this study constrains the formation mechanisms and regional geological significance of [...] Read more.

The Muji carbonic springs on the northeastern margin of the Pamir Plateau provide a natural window into tectonically controlled CO₂ degassing within a continental collision zone. Through mineralogical and geochemical analyses, this study constrains the formation mechanisms and regional geological significance of carbonic spring systems. The formed deposits are dominated by calcite and aragonite, with minor dolomite, quartz, and gypsum. The compositions of major elements are consistent with the observed mineral assemblages, reflecting that the carbonate deposition was mainly governed by CO₂ degassing intensity and associated kinetic effects under cold-spring conditions. Carbon isotopes of the deposits are consistently enriched in heavy carbon with δ¹³C values of +3.5‰ to +9.1‰, indicating a persistent contribution of deep-sourced CO₂, most likely derived from metamorphic decarbonation of the crustal carbonates. Calcite exhibits moderate δ¹³C values due to rapid precipitation limiting isotope enrichment, whereas aragonite records higher δ¹³C signatures under subdued degassing and stable hydrodynamic regimes. The narrow δ¹⁸O range (−10.7‰ to −12.6‰), closely matching that of the spring waters, indicates that the tufas record the δ¹⁸O of the spring waters through DIC-water oxygen exchange. Trace element distributions (Sr–Ba–U) reveal systematic enrichment in deep-sourced fluids and progressive downstream geochemical alteration driven by spring–river mixing. The HD springs show high Sr and δ¹³C values, indicating minimal dilution of ascending CO₂-rich fluids, while MJX and MJXSP groups record variable degrees of shallow mixing. Collectively, the Muji system exemplifies a coupled process of “deep fluid input–shallow mixing–precipitation kinetics.” Its persistent heavy δ¹³C and trace-element enrichments demonstrate persistent metamorphic CO₂ release through fault conduits under ongoing compression. These findings establish the Muji springs as a key non-volcanic analogue for deep CO₂ degassing in continental collision zones and provides new insights into crustal carbon recycling and tectonic–hydrochemical coupling at plateau margins. Full article

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

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Minerals, Volume 15, Issue 12 (December 2025) – 104 articles

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