Minerals

19 pages, 569 KiB

Open AccessArticle

Optimization in Mineral Processing: A Novel Matheuristic for a Variant of the Knapsack Problem

by Carlos Leiva, Hernán Lespay, Aldo Quelopana and Alessandro Navarra

Minerals 2025, 15(4), 427; https://doi.org/10.3390/min15040427 (registering DOI) - 19 Apr 2025

This study introduces a novel heuristic approach to optimize mineral processing in metallurgical plants, framed as a variant of the fractional knapsack problem. The optimization framework integrates plant operational modes, blending requirements, and processing constraints to maximize the recoverable value of mineral blocks [...] Read more.

This study introduces a novel heuristic approach to optimize mineral processing in metallurgical plants, framed as a variant of the fractional knapsack problem. The optimization framework integrates plant operational modes, blending requirements, and processing constraints to maximize the recoverable value of mineral blocks while adhering to plant capacity and feed limitations. Building on a previously established mixed-integer linear programming formulation, this study develops a heuristic algorithm employing a greedy strategy. This alternative approach significantly reduces computational time while achieving near-optimal solutions, making it suitable for practical implementation. Validation through a case study demonstrates the algorithm’s effectiveness in managing complex constraints and delivering actionable insights for real-world operations. These findings highlight the potential of this methodology to streamline the mineral processing stage of broader mine planning frameworks, complementing the initial optimization of block extraction with faster and more reliable processing calculations. Full article

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

24 pages, 12865 KiB

Open AccessArticle

Zircon U-Pb Geochronology and Geochemical Constraints of Tiancang Granites, Southern Beishan Orogenic Belt: Implications for Early Permian Magmatism and Tectonic Evolution

by Chao Teng, Meiling Dong, Xinjie Yang, Deng Xiao, Jie Shao, Jun Cao, Yalatu Su and Wendong Lu

Minerals 2025, 15(4), 426; https://doi.org/10.3390/min15040426 (registering DOI) - 19 Apr 2025

Abstract

The Beishan Orogenic Belt, situated along the southern margin of the Central Asian Orogenic Belt, represents a critical tectonic domain that archives the prolonged subduction–accretion processes and Paleo-Asian Ocean closure from the Early Paleozoic to the Mesozoic. Early Permian magmatism, exhibiting the most [...] Read more.

The Beishan Orogenic Belt, situated along the southern margin of the Central Asian Orogenic Belt, represents a critical tectonic domain that archives the prolonged subduction–accretion processes and Paleo-Asian Ocean closure from the Early Paleozoic to the Mesozoic. Early Permian magmatism, exhibiting the most extensive spatial-temporal distribution in this belt, remains controversial in its geodynamic context: whether it formed in a persistent subduction regime or was associated with mantle plume activity or post-collisional extension within a rift setting. This study presents an integrated analysis of petrology, zircon U-Pb geochronology, in situ Hf isotopes, and whole-rock geochemistry of Early Permian granites from the Tiancang area in the southern Beishan Orogenic Belt, complemented by regional comparative studies. Tiancang granites comprise biotite monzogranite, monzogranite, and syenogranite. Zircon U-Pb dating of four samples yields crystallization ages of 279.3–274.1 Ma. These granites are classified as high-K calc-alkaline to calc-alkaline, metaluminous to weakly peraluminous I-type granites. Geochemical signatures reveal the following: (1) low total rare earth element (REE) concentrations with light REE enrichment ((La/Yb)_N = 3.26–11.39); (2) pronounced negative Eu anomalies (Eu/Eu* = 0.47–0.71) and subordinate Ce anomalies; (3) enrichment in large-ion lithophile elements (LILEs: Rb, Th, U, K) coupled with depletion in high-field-strength elements (HFSEs: Nb, Ta, P, Zr, Ti); (4) zircon ε_Hf(t) values ranging from −10.5 to −0.1, corresponding to Hf crustal model ages (T_DMC) of 1.96–1.30 Ga. These features collectively indicate that the Tiancang granites originated predominantly from partial melting of Paleoproterozoic–Mesoproterozoic crustal sources with variable mantle contributions, followed by extensive fractional crystallization. Regional correlations demonstrate near-synchronous magmatic activity across the southern/northern Beishan and eastern Tianshan Orogenic belts. The widespread Permian granitoids, combined with post-collisional magmatic suites and rift-related stratigraphic sequences, provide compelling evidence for a continental rift setting in the southern Beishan during the Early Permian. This tectonic regime transition likely began with lithospheric delamination after the Late Carboniferous–Early Permian collisional orogeny, which triggered asthenospheric upwelling and crustal thinning. These processes ultimately led to the terminal closure of the Paleo-Asian Ocean’s southern branch, followed by intracontinental evolution. Full article

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

12 pages, 3059 KiB

Open AccessArticle

Application of Surface-Modified Natural Magnetite as a Magnetic Carrier for Microplastic Removal from Water

by Palot Srichonphaisarn, Natatsawas Soonthornwiphat, Pongsiri Julapong, Thanakornkan Limlertchareonwanit, Thidarat Meekoch, Ilhwan Park, Mylah Villacorte-Tabelin, Onchanok Juntarasakul, Somsak Saisinchai, Carlito Baltazar Tabelin and Theerayut Phengsaart

Minerals 2025, 15(4), 425; https://doi.org/10.3390/min15040425 (registering DOI) - 18 Apr 2025

Abstract

This study investigates the modification and application of natural, micro-scale magnetite (Fe₃O₄)—an iron oxide mineral and one of the most abundant iron ores in the world—as a magnetic carrier for removing six common types of microplastics (MPs) from water: [...] Read more.

This study investigates the modification and application of natural, micro-scale magnetite (Fe₃O₄)—an iron oxide mineral and one of the most abundant iron ores in the world—as a magnetic carrier for removing six common types of microplastics (MPs) from water: polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Hexadecyltrimethoxysilane (HDTMS) was employed as a surfactant to modify the naturally hydrophilic magnetite, transforming it into a hydrophobic material. The characterization of magnetite treated with HDTMS for 0, 6, 12, 24, and 48 h was performed using a scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR). The results showed HDTMS sorption on the surface of natural magnetite, confirming successful surface modification. Carrier magnetic separation was then performed to remove PP, PE, ABS, PS, PET, and PVC using surface-modified, natural magnetite in two size fractions: +38–75 µm (fine-sized) and +75–150 µm (coarse-sized). Improved performance was observed with longer HDTMS treatment of magnetite, while greater than 90% MP removal was achieved using fine-sized, surface-modified, natural magnetite. These results suggest that surface modification enhanced the heterogenous interactions between magnetite and MPs via hydrophobic-hydrophobic interactions, leading to efficient MP removal via carrier magnetic separation. Full article

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

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22 pages, 10843 KiB

Open AccessArticle

Rapid Updating of Multivariate Resource Models Based on New Information Using EnKF-MDA and Multi-Gaussian Transformation

by łSultan Abulkhair, Peter Dowd, Chaoshui Xu and Penny Stewart

Minerals 2025, 15(4), 424; https://doi.org/10.3390/min15040424 - 18 Apr 2025

Abstract

Rapid-resource model updating with real-time data is important for making timely decisions in resource management and mining operations. This requires optimal merging of models and observations, which can be achieved through data assimilation, and the ensemble Kalman filter (EnKF) has become a popular [...] Read more.

Rapid-resource model updating with real-time data is important for making timely decisions in resource management and mining operations. This requires optimal merging of models and observations, which can be achieved through data assimilation, and the ensemble Kalman filter (EnKF) has become a popular method for this task. However, the modeled resources in mining usually consist of multiple variables of interest with multivariate relationships of varying complexity. EnKF is not a multivariate approach, and even for univariate cases, there may be slight deviations between its outcomes and observations. This study presents a methodology for rapidly updating multivariate resource models using the EnKF with multiple data assimilations (EnKF-MDA) combined with rotation-based iterative Gaussianization (RBIG). EnKF-MDA improves the updating by assimilating the same data multiple times with an inflated measurement error, while RBIG quickly transforms the data into multi-Gaussian factors. The application of the proposed algorithm is validated by a real case study with nine cross-correlated variables. The combination of EnKF-MDA and RBIG successfully improves the accuracy of resource model updates, minimizes uncertainty, and preserves the multivariate relationships. Full article

(This article belongs to the Special Issue Application of Big Data Mining, Machine Learning and Artificial Intelligence in Geoscience, 2nd Edition)

36 pages, 12249 KiB

Open AccessArticle

Fluid and Solid Inclusions from Accessory Host Minerals of Permian Pegmatites of the Eastern Alps (Austria)—Tracing Permian Fluid, Its Entrapment Process and Its Role During Crustal Anatexis

by Kurt Krenn and Martina Husar

Minerals 2025, 15(4), 423; https://doi.org/10.3390/min15040423 - 18 Apr 2025

Abstract

To understand the fluid evolution of Permian pegmatites, three pegmatite fields of the Austroalpine basement units located in the Rappold Complex at St. Radegund, the Millstatt Complex, and the Polinik Complex were investigated. To achieve this goal, fluid inclusions trapped in the magmatic [...] Read more.

To understand the fluid evolution of Permian pegmatites, three pegmatite fields of the Austroalpine basement units located in the Rappold Complex at St. Radegund, the Millstatt Complex, and the Polinik Complex were investigated. To achieve this goal, fluid inclusions trapped in the magmatic accessories of garnet, tourmaline, spodumene, and beryl were studied using host mineral chemistry combined with fluid inclusion microthermometry and Raman spectrometry. Taking into account the previous work by the authors on pegmatite fields in the Koralpe and Texel Mountains, Permian fluid was determined to have evolved from two stages: Stage 1 is characterized by the homogeneous entrapment of two cogenetic immiscible fluid assemblages, a CO₂-N₂±CH₄-rich and a low-saline H₂O-rich fluid. Both fluids are restricted to inclusions in the early-magmatic-garnet-core domains of the Koralpe Mountains. Stage 2 is linked with the CO₂-N₂-CH₄-H₂O-NaCl-CaCl₂±MgCl₂ fluid preserved as an inclusion in all the pegmatite accessories of the KWNS. It represents the mechanical mixture of the stage 1 fluid caused by compositional changes along the solvus, which is typical for a hydrothermal vein environment process. Increasing X_CH4±N2 proportions from the eastern toward the western pegmatite fields of the KWNS results in a tectonic model that includes magmatic redox-controlled fluid flow along deep crustal normal faults during the anatexis of metasediments in Permian asymmetric graben structures. Because of a high number of solids within the inclusions as well as their irregular shapes, post-entrapment modifications have caused density changes that have to be considered with caution. However, the conditions in the range of 6–8 kbar at >670 °C for stage 1 and ca. 4 kbar at <670 °C for stage 2 represent the best approximations to explain the uprise of a two-stage Permian fluid associated with accessory mineral crystallization in close relation to fractionating melt. Full article

(This article belongs to the Special Issue Pegmatites as Hosts of Critical Metals: From Petrogenesis to Mineral Exploration)

18 pages, 3813 KiB

Open AccessArticle

Optimizing Dense Medium Separation Pre-Concentration by Comparative Evaluation of High-Pressure Grinding Rolls vs. Conventional Crushing

by Tebogo Mokgomola, Getrude Marape and Rabelani Mariba

Minerals 2025, 15(4), 422; https://doi.org/10.3390/min15040422 - 18 Apr 2025

Abstract

This paper investigated pre-concentration of a low-grade Upper Group 2 (UG2) ore to assess the possibility of rejecting waste at a typical discard Platinum Group Metals (PGMs) grade of <0.4 g/t at mass rejection to floats greater than 16% by comparing feed prepared [...] Read more.

This paper investigated pre-concentration of a low-grade Upper Group 2 (UG2) ore to assess the possibility of rejecting waste at a typical discard Platinum Group Metals (PGMs) grade of <0.4 g/t at mass rejection to floats greater than 16% by comparing feed prepared by High pressure grinding rolls (HPGR) to Conventional crushers (Cone crushers). Heavy Liquid Separation (HLS) was conducted as a benchmark test to Dense Medium Separation (DMS) to determine the expected grade, recovery, and mass yield for various size classes and crusher. The comparison between fine size classes −9.5 + 1.18 mm and −6.7 + 1.18 mm crushed by HPGR and conventional crushing showed that, under the conditions tested, the conventional crusher outperformed HPGR in terms of high sinks grade and a higher percentage of material exposed to pre-concentration. Looking at coarser size fractions (+12 mm), HLS results showed that under the conditions tested, size fraction −20 + 1.18 mm crushed by a conventional crusher at an optimum density of 3.4 g/cm³ is an optimized size fraction to run the DMS plant. The pilot DMS cyclone testwork showed that 61.1% by mass could be rejected to the floats stream based on Run of Mine (ROM) feed at 1.12% Cr₂O₃ and 0.42 g/t Total PGMs + Au grade, a typical discardable PGMs grade. Full article

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

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13 pages, 15917 KiB

Open AccessArticle

Alternative SEM-BEX Imaging of Rock Mini-Cores (Carbonate and Siliciclastic): Manual and Semi-Automated Acquisition

by Jim Buckman, Zaid Jangda, Helen Lewis and Kamaljit Singh

Minerals 2025, 15(4), 421; https://doi.org/10.3390/min15040421 - 17 Apr 2025

Abstract

An understanding of the textures (grain size, grain shape, porosity, etc.), composition (mineralogy), and distribution of constituent components of geological materials such as carbonate and siliciclastic sedimentary rocks is essential in their classification, interpretation, and significance in terms of their geomechanical strength and [...] Read more.

An understanding of the textures (grain size, grain shape, porosity, etc.), composition (mineralogy), and distribution of constituent components of geological materials such as carbonate and siliciclastic sedimentary rocks is essential in their classification, interpretation, and significance in terms of their geomechanical strength and liquid/gas storage potential. In terms of scanning electron microscopy (SEM), this is limited to relatively flat areas of selected rough surfaces, or the analysis of polished thin sections. Here, we illustrate a new technique that can image large areas of the external surface of mini-cores (approximately 10 mm or smaller in diameter) drilled from carbonate and siliciclastic rock samples. The technique utilises a specially developed horizontal rotation stage within an SEM and allows the collection of high-resolution images that can be reconstructed into realistic surface representations of the mini-core surfaces. Elemental data (representative of mineralogy) can also be added using a combined backscattered electron and X-ray (BEX) detector. Currently, these reconstructions can be used as a useful tool for the analysis of both carbonate and siliciclastic geological materials. Further work may allow such reconstructions to aid in the improvement of resolution in micro-CT scans and the direct identification of mineral phases within such scans. Full article

(This article belongs to the Section Clays and Engineered Mineral Materials)

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28 pages, 17232 KiB

Open AccessArticle

Mafic VMS Mineralization in the Mesozoic Metavolcanic Rocks of the Evros Ophiolite, Xylagani Area, Greece

by Vasilios Melfos, Panagiotis Voudouris, Grigorios-Aarne Sakellaris, Christos L. Stergiou, Margarita Melfou, Eftychia Peristeridou, Lambrini Papadopoulou, Jaroslav Pršek and Anestis Filippidis

Minerals 2025, 15(4), 420; https://doi.org/10.3390/min15040420 - 17 Apr 2025

Abstract

The sulfide mineralization at Xylagani is hosted in metamorphosed mafic massive and pillow lava. It has an Early–Middle Jurassic age and belongs to the Makri unit, which represents the upper crustal section of the Evros ophiolite in the Circum Rhodope Belt, Northern Greece. [...] Read more.

The sulfide mineralization at Xylagani is hosted in metamorphosed mafic massive and pillow lava. It has an Early–Middle Jurassic age and belongs to the Makri unit, which represents the upper crustal section of the Evros ophiolite in the Circum Rhodope Belt, Northern Greece. The protolith of the host rock is basalt that has a boninitic-to-low-Ti tholeiitic composition and was formed in an intra-oceanic supra-subduction zone within a juvenile forearc-to-volcanic arc setting. The volcanic rocks were subjected to ocean-floor metamorphism at very low-grade prehnite–pumpellyite facies and low-grade greenschist facies at temperatures of up to 360 °C and pressures between 1 and 4 kbar. The mineralization shows typical features of a stratabound–stratiform deposit and occurs as silicified lenses and layers with disseminated and massive sulfides and gold. Based on host rock composition, geotectonic setting, and base metal content, the mineralization at Xylagani is classified as a Cu-rich mafic volcanic-associated deposit, i.e., Cyprus-type VMS (volcanogenic massive sulfide). The mineralization consists of pyrite, chalcopyrite, gold, pyrrhotite, sphalerite, galena, and tennantite-(Zn). It was formed at a subseafloor setting where hydrothermal fluids circulated through the host volcanic rocks, resulting in a pervasive alteration (silicification and chloritization) and the development of a replacement VMS deposit. The very low-to-low-grade orogenic metamorphism and related deformation during the Alpine collision in the Middle Jurassic to Early Cretaceous periods remobilized the mineralization and formed milky quartz veins with rare sulfides, crosscutting the metavolcanic rocks. Full article

(This article belongs to the Special Issue Ore Deposits Related to Metamorphism)

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28 pages, 16395 KiB

Open AccessArticle

Dolomitization Facilitated by Clay Minerals on Mixed Siliciclastic-Carbonate Shoals of Carboniferous Age in the Tarim Basin, China: Constraints on Element Mobility and Isotope Geochemistry

by Xuan Liu, Meiyan Fu, Jon Gluyas, Rongcai Song, Haoxiang Lan, Yunjie Fan and Dong Wu

Minerals 2025, 15(4), 419; https://doi.org/10.3390/min15040419 - 17 Apr 2025

Abstract

In the western Tarim Basin, Carboniferous granular dolostones deposited on a carbonate platform contain a small amount of terrigenous materials of sand-size fraction, agglomerated clay minerals, or similar phases. However, the role of terrigenous materials on dolomitization is still unclear. The aim of [...] Read more.

In the western Tarim Basin, Carboniferous granular dolostones deposited on a carbonate platform contain a small amount of terrigenous materials of sand-size fraction, agglomerated clay minerals, or similar phases. However, the role of terrigenous materials on dolomitization is still unclear. The aim of this study was to reveal the dolomitization mechanism. The granular dolomites have small crystal size, earthy yellow color, and fabric-retentive texture, with relatively good order. These features indicate dolomites precipitated during early diagenesis. The ratio of rare earth elements (RREs) abundance of the stable isotopes ⁸⁷Sr/⁸⁶Sr relative to Post-Archean Australian Shale (PAAS) normalized patterns was used to study the source of the dolomitizing fluids. The composition of REEs is characterized by heavy rare earth (HREE) enrichment (average Nd_SN/Yb_SN = 0.83). There is a positive (La/La*)_SN anomaly and slightly positive (Gd/Gd*)_SN and (Y/Y*)_SN anomaly; δ¹⁸O of seawater in fractionation equilibrium with granular dolostones was from −2.8‰ to 1.7‰ PDB, implying the dolomitizing fluid was contemporary, slightly evaporated seawater. The granular dolostones on the relatively thick shoals were subject to subaerial exposure before pervasive dolomitization, with evidence that the input of detrital kaolinite predated the formation of dolomites. Higher ⁸⁷Sr/⁸⁶Sr values and ∑REE in granular dolostones than the values in equivalent limestones indicate that dolomitization was related to terrigenous materials. Within the terrigenous materials, the negative-charged clay minerals may have catalyzed the dolomitization, resulting in dramatically decreased induction time for precipitation of proto-dolomites. A greater amount of terrigenous materials occurred on the shoals at the sea level fall, resulting from enhanced river entrenchment and downcutting. As a result, after subaerial exposure, the penesaline water flow through the limy allochems sediments lead to dolomitization, with the catalysis of illite on relatively thick shoals. Full article

(This article belongs to the Section Clays and Engineered Mineral Materials)

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22 pages, 17789 KiB

Open AccessArticle

Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex

by Camila Pineda, Gloria Arancibia, Valentina Mura, Diego Morata, Santiago Maza and John Browning

Minerals 2025, 15(4), 418; https://doi.org/10.3390/min15040418 - 17 Apr 2025

Abstract

The Nevados de Chillán Volcanic Complex is one of the most active of the Southern Volcanic Zone. It is formed by NW-SE-aligned eruptive centers divided into two subcomplexes, namely Cerro Blanco (basaltic andesitic) and Las Termas (dacitic), and two satellite cones (to the [...] Read more.

The Nevados de Chillán Volcanic Complex is one of the most active of the Southern Volcanic Zone. It is formed by NW-SE-aligned eruptive centers divided into two subcomplexes, namely Cerro Blanco (basaltic andesitic) and Las Termas (dacitic), and two satellite cones (to the SW and NE of the main alignment). Our study of the Shangri-La volcano, which is located between the two subcomplexes, in alignment with the satellite cones, and which produced dacitic lavas with basaltic andesitic enclaves, sheds light on the compositional and structural diversity of the volcanic complex. Detailed petrography along with mineral chemistry allows us to suggest partial hybridization between the enclaves and the host lavas and that mixing processes are related to the generation of the Shangri-La volcano and to other volcanic products generated in the complex. This is supported by mixing trends between the enclaves and the most differentiated units from Las Termas. We argue the presence of two main magma storage areas genetically related to crustal structures. A dacitic reservoir (~950 °C) is fed along NW-SE structures, whereas a deeper mafic reservoir (>1100 °C) utilizes predominantly NE-SW structures. We suggest that the intersection between these sets of structures facilitates magma ascent and controls the Nevados de Chillán plumbing system dynamics. Full article

(This article belongs to the Special Issue Magmatic Evolution through Time of Volcanic Zones: Evidence from Isotopic, Geochemical and Geochronological Data of Eruption Products)

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22 pages, 6467 KiB

Open AccessArticle

Integrated Geophysical Signatures of the Jiaodong Region in China and Their Implications for Deep Architecture and Gold Metallogenic Systems

by Haiyang Kuang, Jiayong Yan, Kun Zhang, Wenlong Tang, Chao Fu, Jiangang Liang, Guoli Zhang and Yuexin You

Minerals 2025, 15(4), 417; https://doi.org/10.3390/min15040417 - 17 Apr 2025

Abstract

The Jiaodong region ranks as the world’s third-largest gold metallogenic province, where Late Mesozoic gold mineralization exhibits close genetic connections with cratonic destruction and multi-stage plate tectonic interactions. This study systematically deciphers the deep-seated architecture and metallogenic controls through integrated analysis of gravity, [...] Read more.

The Jiaodong region ranks as the world’s third-largest gold metallogenic province, where Late Mesozoic gold mineralization exhibits close genetic connections with cratonic destruction and multi-stage plate tectonic interactions. This study systematically deciphers the deep-seated architecture and metallogenic controls through integrated analysis of gravity, aeromagnetic, and magnetotelluric datasets. The key findings demonstrate the following: (1) Bouguer gravity anomalies reveal a “two uplifts flanking a central depression” tectonic framework, reflecting superimposed effects from Yangtze Plate subduction and Pacific Plate rollback; (2) zoned aeromagnetic anomalies suggest that the Sanshandao–Jiaojia–Zhaoyuan–Pingdu Metallogenic Belt extends seaward with significant exploration potential; (3) magnetotelluric inversion identifies three lithosphere penetrating conductive zones, confirming the Jiaojia and Zhaoyuan–Pingdu faults as crust mantle fluid conduits, while the Taocun–Jimo fault marks the North China–Sulu Block boundary; and (4) metallogenic materials derive from hybrid sources of deep Yangtze Plate subduction and mantle upwelling, with gold enrichment controlled by intersections of NE-trending faults and EW-oriented basement folds. Integrated geophysical signatures indicate that the northwestern Jiaodong offshore area (north of Sanshandao) holds supergiant gold deposit potential. This research provides critical constraints for the craton destruction type gold mineralization model. Full article

(This article belongs to the Special Issue Gravity, Magnetic, and Electromagnetic (GME) Geophysical Data Interpretation for Mineral Exploration and Crustal Structure Investigation)

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14 pages, 4682 KiB

Open AccessArticle

The Burela Kaolin Deposit (NW Spain): Genesis, Composition and Micro- and Nanotexture

by Blanca Bauluz, Alfonso Yuste, Sergio Alvira and Andrea García-Vicente

Minerals 2025, 15(4), 416; https://doi.org/10.3390/min15040416 - 17 Apr 2025

Abstract

A set of samples from the Monte Castelo kaolin deposits (Burela, NW Spain), corresponding to igneous acidic rocks affected by chemical weathering with variable intensity have been investigated in order to establish the mineralogical and chemical changes with weathering, and the micro- and [...] Read more.

A set of samples from the Monte Castelo kaolin deposits (Burela, NW Spain), corresponding to igneous acidic rocks affected by chemical weathering with variable intensity have been investigated in order to establish the mineralogical and chemical changes with weathering, and the micro- and nano-scale textures developed. For the study, XRD, FESEM, HRTEM and chemical analyses have been used. The more intense the weathering, the more the dissolution of aluminosilicates (albite, K feldspars and K micas) and the crystallization of kaolinite is favored. Kaolinite grows, forming booklets and generating a fine-grained matrix and, along the cleavages of muscovite, forming mica–kaolinite intergrowths. Bidimensional crystallographic continuity between mica and kaolinite has been observed and no intermediate phases have been identified as a consequence of the high W/R ratio. Kaolin mainly contains kaolinite with high crystallinity; however, when there are quartz impurities, they interfere with the ‘optimal’ reflections for the calculation of the Hinckley index. In this case, the use of the AGFI index almost eliminates the effect that the relative intensities of the quartz and feldspar impurities may have on those of kaolinite. With weathering, there is a progressive decrease in the contents of most chemical elements, except Al, TiO₂, HREEs, Ta, Hf, Th, U, V, Cr, S, Zr, Mo and Sn. Full article

(This article belongs to the Special Issue Clay Minerals: From Paleoclimatic and Paleoenvironmental Indicators to Industrial Raw Materials)

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24 pages, 16059 KiB

Open AccessArticle

Bauxite Exploration in Fold–Thrust Belts: Insights from the Posušje Region, Bosnia and Herzegovina

by Giulio Casini, Eduard Saura, Ivica Pavičić, Ida Pavlin, Šime Bilić, Irena Peytcheva and Franjo Šumanovac

Minerals 2025, 15(4), 415; https://doi.org/10.3390/min15040415 - 14 Apr 2025

Abstract

In the Posušje region of the External Dinarides (Bosnia and Herzegovina), bauxite deposits are hosted along a Late Cretaceous–Paleogene forebulge unconformity that records an extended emersion phase of the Adriatic Carbonate Platform. Historically, open-pit mining has targeted surface and shallow subsurface bauxite bodies, [...] Read more.

In the Posušje region of the External Dinarides (Bosnia and Herzegovina), bauxite deposits are hosted along a Late Cretaceous–Paleogene forebulge unconformity that records an extended emersion phase of the Adriatic Carbonate Platform. Historically, open-pit mining has targeted surface and shallow subsurface bauxite bodies, but ongoing exploration must now focus on deeper structurally preserved deposits. To address this challenge, we integrate remote sensing, geological mapping, borehole data, and 3D structural modeling to assess the distribution and structural controls of bauxite deposits. Balanced and restored cross-sections reveal a complex interplay between inverted normal faults, fold structures, and foredeep burial, which collectively influenced bauxite accumulation and preservation. Statistical analyses of deposit size, shape, and orientation indicate that larger bauxite bodies are concentrated in the footwalls of inverted normal faults, where prolonged or repeated exposure enhanced karst development and bauxite accumulation. Additionally, the predominant NW–SE elongation of bauxite bodies suggests that pre-existing structural lineaments played a key role in paleokarst morphology, supporting the influence of syn-depositional extensional faulting on bauxite distribution. These findings demonstrate that bauxite exploration in fold–thrust belts requires an integrated structural approach, where 3D geological modeling can delineate prospective areas prior to costly geophysical surveys and drilling campaigns. Insights from the Posušje region can refine mineral exploration strategies in other orogenic settings, highlighting the importance of structural inheritance in karst bauxite accumulation and preservation. Full article

(This article belongs to the Special Issue Mineral Prospectivity Mapping (MPM) Using Multi-Source Datasets, Geo-Statistical Algorithms and Machine Learning Techniques)

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15 pages, 4486 KiB

Open AccessArticle

Extraction and Separation of Ytterbium and Nickel from Heavy Metal Solutions Containing Manganese and Calcium Impurities

by Bo Zhang, Yan Huang and Gang Zhao

Minerals 2025, 15(4), 414; https://doi.org/10.3390/min15040414 - 14 Apr 2025

Abstract

This study systematically investigated the extraction and separation of ytterbium (Yb) and nickel (Ni) from manganese (Mn)- and calcium (Ca)-containing heavy metal solutions using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (HEHEHP) in nitric acid media. Results demonstrated that the logarithms of distribution ratios for [...] Read more.

This study systematically investigated the extraction and separation of ytterbium (Yb) and nickel (Ni) from manganese (Mn)- and calcium (Ca)-containing heavy metal solutions using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (HEHEHP) in nitric acid media. Results demonstrated that the logarithms of distribution ratios for Yb, Ni, Mn, and Ca exhibited positive correlations with both solution pH and the logarithm of extractant concentration, consistent with theoretical models. Elevated initial metal concentrations reduced distribution ratios for all elements, indicating extraction inhibition. Ytterbium back-extraction efficiency increased proportionally with hydrochloric acid concentration and the number of back-extraction stages. Optimization of key extraction parameters established predictive equilibrium relationships: Yb/Ni and Mn/Ca separation coefficients increased with decreasing acidity and extractant concentration, whereas Mn/Ni and Ca/Ni coefficients rose under higher acidity and extractant conditions. Infrared spectroscopy confirmed HEHEHP-Yb complexation mechanisms, with extractant stability retained through multiple reuse cycles. Optimized cascade processing parameters (3 extraction stages, 3 washing stages, 4 back-extraction stages) achieved >99.9% purity for both Yb and Ni. This validated methodology provides a robust technical framework for heavy metal waste treatment and high-value element recovery. Full article

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

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10 pages, 2336 KiB

Open AccessArticle

Effect of the Occurrence State of Dodecylamine on the Adsorption Behavior of Calcium Sulfate Dihydrate and Silica

by Xu Li, Renjie Chen and Lan Xiang

Minerals 2025, 15(4), 413; https://doi.org/10.3390/min15040413 - 14 Apr 2025

Abstract

In this work, the effects of dodecylamine storage state on the adsorption behavior of calcium sulfate dihydrate and silica were systematically investigated by using Raman detection, solution equilibrium calculation, and calculation based on density functional theory. The results show that the selective adsorption [...] Read more.

In this work, the effects of dodecylamine storage state on the adsorption behavior of calcium sulfate dihydrate and silica were systematically investigated by using Raman detection, solution equilibrium calculation, and calculation based on density functional theory. The results show that the selective adsorption behavior of dodecylamine with calcium sulfate dihydrate and silica is closely related to its occurrence state. The adsorption of dodecylamine in the ionic state with calcium sulfate dihydrate and silica is dominated by the strong electrostatic adsorption between the H-O atoms under acidic conditions, while that of dodecylamine in the molecular state is dominated by the weak electrostatic adsorption between the Ca-N or Si-N atoms under alkaline conditions. Finally, by comparing the distribution coefficients and adsorption energies of the ionic/molecular states of dodecylamine with the change in pH, the reason why dodecylamine adsorbs calcium sulfate dihydrate more readily under acidic conditions was explained at the atomic level. Full article

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

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16 pages, 8149 KiB

Open AccessArticle

Determining the Mechanical Properties of Shale Constituent Minerals Using Nanoindentation and a TESCAN Integrated Mineral Analyzer (TIMA)

by Yongjun Xiao, Qi Cheng, Jiren Tang and Shengyao Cai

Minerals 2025, 15(4), 412; https://doi.org/10.3390/min15040412 - 14 Apr 2025

Abstract

Understanding the mechanical properties of the constituent minerals of shales is of significance for gaining insight into the macroscopic mechanical behavior of shales. In this paper, a method combining nanoindentation with a TESCAN Integrated Mineral Analyzer (TIMA) was used to determine the mechanical [...] Read more.

Understanding the mechanical properties of the constituent minerals of shales is of significance for gaining insight into the macroscopic mechanical behavior of shales. In this paper, a method combining nanoindentation with a TESCAN Integrated Mineral Analyzer (TIMA) was used to determine the mechanical properties of shale constituent minerals. The hardness and elastic modulus of five independent mineral phases and a mixed phase were detected. The order of the hardness of these five independent mineral phases is dolomite (4.90 ± 2.33 GPa) > wollastonite (4.84 ± 0.54 GPa) > ankerite (4.17 ± 1.37 GPa) > quartz (3.98 ± 0.67 GPa) > calcite (2.03 ± 0.29 GPa), and the order of the elastic modulus is dolomite (104.89 ± 11.25 GPa) > ankerite (103.70 ± 19.62 GPa) > wollastonite (100.78 ± 6.66 GPa) > quartz (88.04 ± 14.58 GPa) > calcite (78.20 ± 3.85 GPa). The mechanical properties of the shale mineral grain junctions are weaker than those inside the grains. When shale is subjected to an external load, it is more prone to intergranular failure. The proposed method in this study can rapidly and accurately probe the in situ mechanical properties of shale minerals. The results of this study enrich the database of in situ mechanical properties of shale minerals and provide a new insight into the macroscopy failure mode of shale. Full article

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

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27 pages, 9532 KiB

Open AccessArticle

Unsupervised Anomaly Detection for Mineral Prospectivity Mapping Using Isolation Forest and Extended Isolation Forest Algorithms

by Mobin Saremi, Ardeshir Hezarkhani, Seyyed Ataollah Agha Seyyed Mirzabozorg, Ramin DehghanNiri, Adel Shirazy and Aref Shirazi

Minerals 2025, 15(4), 411; https://doi.org/10.3390/min15040411 - 13 Apr 2025

Abstract

Unsupervised anomaly detection algorithms have gained significant attention in the field of mineral prospectivity mapping (MPM) due to their ability to reveal hidden mineralization zones by effectively modeling complex, nonlinear relationships between exploration data and mineral deposits. This study utilizes two tree-based anomaly [...] Read more.

Unsupervised anomaly detection algorithms have gained significant attention in the field of mineral prospectivity mapping (MPM) due to their ability to reveal hidden mineralization zones by effectively modeling complex, nonlinear relationships between exploration data and mineral deposits. This study utilizes two tree-based anomaly detection algorithms, namely, isolation forest (IF) and extended isolation forest (EIF), to enhance MPM and exploration targeting. According to the conceptual model of porphyry copper deposits, several evidence layers were generated, including fault density, multi-element geochemical signatures, proximity to various alteration types (phyllic, argillic, propylitic, and iron oxide), and proximity to intrusive rocks. These layers were integrated using IF and EIF algorithms, and their results were subsequently compared with a geological map of the study area. The comparison revealed a high degree of overlap between the identified anomalous zones and geological features, such as andesitic rocks, tuffs, rhyolites, pyroclastics, and intrusions. Additionally, quantitative assessments through prediction-area plots validated the efficacy of both models in generating prospective targets. The results highlight the significant influence of hyperparameter tuning on the accuracy of prospectivity models. Furthermore, the study demonstrates that hyperparameter tuning is more intuitive and straightforward in IF, as it provides a clear and distinct tuning pattern, whereas EIF lacks such clarity, complicating the optimization process. Full article

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

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24 pages, 12903 KiB

Open AccessArticle

Advances in Glendonite Understanding and Its Potential for Carbon Capture

by Bo Pagh Schultz and Jennifer Huggett

Minerals 2025, 15(4), 410; https://doi.org/10.3390/min15040410 - 13 Apr 2025

Abstract

This article reviews recent advances made by the authors through evaluation of samples in museum collections, in the context of our recent advances in novel observations, of cleavage in a recrystallising ikaite crystal, that may guide future research in understanding the morphology of [...] Read more.

This article reviews recent advances made by the authors through evaluation of samples in museum collections, in the context of our recent advances in novel observations, of cleavage in a recrystallising ikaite crystal, that may guide future research in understanding the morphology of ikaite, which traditional crystallography has so far not achieved, as traditional crystallography cannot be applied to the morphology of ikaite. Having reviewed over 1100 samples in museum collections, using a combination of morphology and petrology, we are able to define how samples can be classified as glendonite. The topics covered include: (1) a historical review of ikaite and glendonite; (2) evidence supporting ikaite as the precursor mineral of glendonite; (3) the discovery of mega-sized Danish glendonites; and (4) Holocene glendonite coastal sites. Our reassessment of existing knowledge of ikaite shows that when ikaite forms in marine settings, it forms in specific zones before other carbonate phases, and that in sedimentary environments, pressure and pH are not the primary factors controlling its precipitation. Instead, the availability of magnesium (Mg²⁺) and phosphate (PO₄³⁻) ions appear to play a more significant role. Furthermore, the conditions required for ikaite precipitation in laboratory experiments differ from those observed in natural ikaite or glendonite formation. Ikaite’s ability to capture carbon at low temperatures and its rapid recrystallisation into its more stable calcite pseudomorph, glendonite, suggest a potential application in carbon capture strategies. Full article

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

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18 pages, 1941 KiB

Open AccessArticle

Extraction of Copper from Printed Circuit Boards in an Alkaline Solution Using EDTA

by Alan Oliveira Goulart, Tácia Costa Veloso, Hugo Marcelo Veit and Tatiane Benvenuti

Minerals 2025, 15(4), 409; https://doi.org/10.3390/min15040409 - 13 Apr 2025

Abstract

With the rapid technological development in the 21st century, the increasing consumption of electronic devices has led to a rise in the generation of waste electrical and electronic equipment (WEEE) due to the disposal of equipment considered obsolete. A significant portion of these [...] Read more.

With the rapid technological development in the 21st century, the increasing consumption of electronic devices has led to a rise in the generation of waste electrical and electronic equipment (WEEE) due to the disposal of equipment considered obsolete. A significant portion of these wastes contain printed circuit boards (PCBs), which serve as substrates for the connection of microchips, resistors, capacitors, and other components. These boards are composed of various materials, primarily metals such as copper. Thus, this study investigated the recovery of copper from PCB waste (WPCBs) from computers through alkaline leaching, using EDTA and hydrogen peroxide at temperatures of 40 °C, 60 °C, and 80 °C, with a concentration of 0.6 mol/L and varying particle sizes. Using a UV-VIS spectrophotometer, it was observed that the copper extraction process with EDTA at 0.6 mol/L and a temperature of 60 °C achieved a recovery rate of 78.6% for particles smaller than 0.177 mm after 180 min, following the Avrami kinetic model. The results highlight the potential of EDTA as a complexing agent in copper extraction, positioning it as a promising technique to reduce environmental contamination and recover strategic resources through urban mining through the recovery of metals from WEEE. Full article

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

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