Minerals

45 pages, 22848 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Syn-Sedimentary Exhalative or Diagenetic Replacement? Multi-Proxy Evidence for Origin of Metamorphosed Stratiform Barite–Sulfide Deposits near Aberfeldy, Scottish Highlands

by Norman R. Moles, Adrian J. Boyce, Matthew R. Warke and Mark W. Claire

Minerals 2024, 14(9), 865; https://doi.org/10.3390/min14090865 - 25 Aug 2024

Cited by 1 | Viewed by 1604

Abstract

Bedded barite, Fe-Zn-Pb sulfides, carbonates, and cherts within Ediacaran (Dalradian Supergroup) graphitic metasediments near Aberfeldy in Scotland have previously been interpreted as chemical sediments precipitated from hydrothermal fluids episodically exhaled into marine basins filled with organic-rich mud, silt, and sand. Lithological variation and [...] Read more.

Bedded barite, Fe-Zn-Pb sulfides, carbonates, and cherts within Ediacaran (Dalradian Supergroup) graphitic metasediments near Aberfeldy in Scotland have previously been interpreted as chemical sediments precipitated from hydrothermal fluids episodically exhaled into marine basins filled with organic-rich mud, silt, and sand. Lithological variation and compositional diversity in pyrite and sphalerite reflect varied redox environments and proximity to hydrothermal discharges. Thick beds (>2 m) of barite have relatively uniform δ³⁴S of +36 ± 1.5‰, considered to represent contemporaneous seawater sulfate, as negative Δ¹⁷O indicates incorporation of atmospheric oxygen during precipitation in the water column. However, certain features suggest that diagenetic processes involving microbial sulfate reduction modified the mineralogy and isotopic composition of the mineralization. Barite bed margins show decimeter-scale variation in δ³⁴S (+32 to +41‰) and δ¹⁸O (+8 to +21‰), attributed to fluid-mediated transfer of dissolved barium and sulfate between originally porous barite and adjacent sediments, in which millimetric sulfate crystals grew across sedimentary lamination. Encapsulated micron-sized barium carbonates indicate early diagenetic barite dissolution with incorporation of sulfur into pyrite, elevating pyrite δ³⁴S. Subsequently, sulfidation reactions produced volumetrically minor secondary barite with δ³⁴S of +16 to +22‰. Overall, these processes affected small volumes of the mineralization, which originally formed on the seafloor as a classic SEDEX deposit. Full article

(This article belongs to the Special Issue Stratabound Barite Deposits: Mineralogy, Isotope Geochemistry and Geochronology)

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31 pages, 7774 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Monchegorsk Mafic–Ultramafic Layered PGE-Bearing Complex (2.5 Ga, Kola Region, Russia): On the Problem of Relationships between Magmatic Phases Based on the Study of Cr-Spinels

by Pavel Pripachkin, Tatiana Rundkvist, Artem Mokrushin and Aiya Bazai

Minerals 2024, 14(9), 856; https://doi.org/10.3390/min14090856 - 24 Aug 2024

Viewed by 824

Abstract

The composition of Cr-spinels from rocks of the Monchegorsk layered complex (2.5 Ga) basically corresponds to the evolutionary trend that is typical for layered mafic–ultramafic intrusions (late magmatic phases contain Cr-spinels enriched in Fe and depleted in Mg, Cr, and Al). Cr-spinels within [...] Read more.

The composition of Cr-spinels from rocks of the Monchegorsk layered complex (2.5 Ga) basically corresponds to the evolutionary trend that is typical for layered mafic–ultramafic intrusions (late magmatic phases contain Cr-spinels enriched in Fe and depleted in Mg, Cr, and Al). Cr-spinels within the Dunite Body of the Sopcha massif are almost identical to those within the Dunite Block rocks and are close to those from harzburgite of the NKT massif. Cr-spinels within the satellite bodies of the Ore Layer 330 are shown to have zonal structure, which confirms their origin from a new portion of melt, which may have been injected with several pulses. The composition of accessory Cr-spinels may indicate that the layered complex of rocks of the South Sopcha massif was formed from the most evolved portion of magmatic melt (linked with the Monchetundra intrusion), and its vein complex may be considered the one formed at the final stages of the magmatic system evolution. The composition of Cr-spinels from the Pentlandite Gorge mafic–ultramafic rocks may indicate that they are fragments of the NKT massif and not of the Monchetundra massif, as it was believed earlier. Full article

(This article belongs to the Section Mineral Deposits)

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39 pages, 3652 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Coal and Coal By-Products as Unconventional Lithium Sources: A Review of Occurrence Modes and Hydrometallurgical Strategies for Metal Recovery

by Ewa Rudnik

Minerals 2024, 14(8), 849; https://doi.org/10.3390/min14080849 - 22 Aug 2024

Cited by 5 | Viewed by 2237

Abstract

Lithium, a critical material for the global development of green energy sources, is anomalously enriched in some coal deposits and coal by-products to levels that may be considered economically viable. Recovering lithium from coal, particularly from coal gangue or coal ashes, offers a [...] Read more.

Lithium, a critical material for the global development of green energy sources, is anomalously enriched in some coal deposits and coal by-products to levels that may be considered economically viable. Recovering lithium from coal, particularly from coal gangue or coal ashes, offers a promising alternative for extracting this element. This process could potentially lead to economic gains and positive environmental impacts by more efficiently utilizing coal-based waste materials. This review focuses on lithium concentrations in coal and coal by-products, modes of lithium occurrence, methods used to identify lithium-enriched phases, and currently available hydrometallurgical recovery methods, correlated with pretreatment procedures that enable lithium release from inert aluminosilicate minerals. Leaching of raw coal appears inefficient, whereas coal gangue and fly ash are more feasible due to their simpler composition and higher lithium contents. Lithium extraction can achieve recovery rates of over 90%, but low lithium concentrations and high impurity levels in the leachates require advanced selective separation techniques. Bottom ash has not yet been evaluated for lithium recovery, despite its higher lithium content compared to feed coal. Full article

(This article belongs to the Special Issue Beneficiation and Extraction of Critical Metals from Ores and Secondary Resources)

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22 pages, 5061 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Protocol for Electron Probe Microanalysis (EPMA) of Monazite for Chemical Th-U-Pb Age Dating

by Bernhard Schulz, Joachim Krause and Wolfgang Dörr

Minerals 2024, 14(8), 817; https://doi.org/10.3390/min14080817 - 12 Aug 2024

Cited by 2 | Viewed by 1751

Abstract

A protocol for the monazite (LREE,Y,Th,U,Si,Ca)PO₄ in situ Th-U-Pb dating by electron probe microanalyser (EPMA) involves a suitable reference monazite. Ages of several potential reference monazites were determined by TIMS-U-Pb isotope analysis. The EPMA protocol is based on calibration with REE-orthophosphates and [...] Read more.

A protocol for the monazite (LREE,Y,Th,U,Si,Ca)PO₄ in situ Th-U-Pb dating by electron probe microanalyser (EPMA) involves a suitable reference monazite. Ages of several potential reference monazites were determined by TIMS-U-Pb isotope analysis. The EPMA protocol is based on calibration with REE-orthophosphates and a homogeneous Th-rich reference monazite at beam conditions of 20 kV, 50 nA, and 5 µm for best possible matrix matches and avoidance of dead time bias. EPMA measurement of samples and repeated analysis of the reference monazite are performed at beam conditions of 20 kV, 100 nA, and 5 µm. Analysis of Pb and U on a PETL crystal requires YLg-on-PbMa and ThMz-on-UMb interference corrections. Offline re-calibration of the Th calibration on the Th-rich reference monazite, to match its nominal age, is an essential part of the protocol. EPMA-Th-U-Pb data are checked in ThO₂*-PbO coordinates for matching isochrones along regressions forced through zero. Error calculations of monazite age populations are performed by weighted average routines. Depending on the number of analyses and spread in ThO₂*-PbO coordinates, minimum errors <10 Ma are possible and realistic for Paleozoic monazite ages. A test of the protocol was performed on two garnet metapelite samples from the Paleozoic metamorphic Zone of Erbendorf-Vohenstrauß (NE-Bavaria, western Bohemian Massif). Full article

(This article belongs to the Special Issue In-Situ Microanalytical Techniques in Geological and Geochronological Research)

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23 pages, 3689 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Gypsum on Mars: A Detailed View at Gale Crater

by David Vaniman, Steve Chipera, Elizabeth Rampe, Thomas Bristow, David Blake, Johannes Meusburger, Tanya Peretyazhko, William Rapin, Jeff Berger, Douglas Ming, Patricia Craig, Nicholas Castle, Robert T. Downs, Shaunna Morrison, Robert Hazen, Richard Morris, Aditi Pandey, Allan H. Treiman, Albert Yen, Cherie Achilles, Benjamin Tutolo, Elisabeth Hausrath, Sarah Simpson, Michael Thorpe, Valerie Tu, David J. Des Marais, John Grotzinger and Abigail Fraeman Show full author list Hide full author list

Minerals 2024, 14(8), 815; https://doi.org/10.3390/min14080815 - 12 Aug 2024

Cited by 2 | Viewed by 2317

Abstract

Gypsum is a common mineral at Gale crater on Mars, currently being explored by the Mars Science Laboratory (MSL) rover, Curiosity. In this paper, we summarize the associations of gypsum with other sulfate minerals (bassanite, anhydrite, jarosite, starkeyite, and kieserite) from the [...] Read more.

Gypsum is a common mineral at Gale crater on Mars, currently being explored by the Mars Science Laboratory (MSL) rover, Curiosity. In this paper, we summarize the associations of gypsum with other sulfate minerals (bassanite, anhydrite, jarosite, starkeyite, and kieserite) from the lowest levels of the crater’s northern moat zone (Aeolis Palus) up through ~0.8 km of the stratigraphic section in the lower slopes of the sedimentary mound developed around the central peak, Aeolis Mons (informally, Mount Sharp). The analysis is based on results from the CheMin X-ray diffraction instrument on Curiosity, supplemented with information from the rover’s versatile instrument suite. Gypsum does not occur with the same frequency as less hydrous Ca-sulfates, likely, in most cases, because of its dehydration to bassanite and possibly to anhydrite. All three of these Ca-sulfate phases often occur together and, along with other sulfates, in mixed assemblages that are evidence of limited equilibration on a cold, dry planet. In almost all samples, at least one of the Ca-sulfate minerals is present, except for a very limited interval where jarosite is the major sulfate mineral, with the implication of more acidic groundwater at a much later time in Gale crater’s history. Although observations from orbit reveal a sulfate-rich surface, currently active dark basaltic dunes at Gale crater have only small amounts of a single sulfate mineral, anhydrite. Gale crater has provided the most complete mineralogical analysis of a site on Mars so far, but the data in hand show that Gale crater mineralogy is not a blueprint with planet-wide application. The concurrent study of Jezero crater by the Mars 2020 mission and comparisons to what is believed to be the most extensive deposit of gypsum on Mars, in the dune fields at the north polar ice cap, show significant diversity. Unraveling the stories of gypsum and other sulfates on Mars is just beginning. Full article

(This article belongs to the Special Issue Gypsum Crystals: The Importance and the Role of Calcium Sulphate in Past and Modern Environments)

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25 pages, 3020 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Exploring Low-Grade Iron Ore Beneficiation Techniques: A Comprehensive Review

by Mompati Mpho Bulayani, Prasad Raghupatruni, Tirivaviri Mamvura and Gwiranai Danha

Minerals 2024, 14(8), 796; https://doi.org/10.3390/min14080796 - 2 Aug 2024

Cited by 6 | Viewed by 5162

Abstract

The beneficiation of low-grade iron ores is a key research and development topic in the mineral processing industry. The gradual exhaustion of high-grade iron ore reserves, and rising consumer iron and steel demand globally necessitate efficient low-quality iron ore beneficiation to meet steelmaking [...] Read more.

The beneficiation of low-grade iron ores is a key research and development topic in the mineral processing industry. The gradual exhaustion of high-grade iron ore reserves, and rising consumer iron and steel demand globally necessitate efficient low-quality iron ore beneficiation to meet steelmaking quality requirements. This comprehensive review explores various beneficiation techniques for low-quality iron ore, focusing on conventional methods including comminution, froth flotation and gravity separation. This article discusses the principles, processes, and equipment used in these techniques and highlights recent advancements and research efforts in the field. This review also emphasizes the importance of effective beneficiation processes in enhancing economic viability, sustainable resource management, and environmental conservation. Furthermore, it presents a case study of iron ore deposits in Botswana, highlighting the potential economic growth and sustainable development that can be achieved by maximizing resource utilization through reductive roasting, followed by magnetic separation of iron ore using semi-bituminous coal as a reductant. Overall, this review provides valuable insights into low-grade iron ore beneficiation techniques and their significance in meeting the growing demand for high-quality iron and steel products. Full article

(This article belongs to the Special Issue Recent Advances in Extractive Metallurgy)

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14 pages, 3452 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Pore Water Chemistry on Particle Association and Physical Properties of Lime-Treated Bentonite

by Enza Vitale, Dimitri Deneele and Giacomo Russo

Minerals 2024, 14(8), 795; https://doi.org/10.3390/min14080795 - 2 Aug 2024

Cited by 1 | Viewed by 851

Abstract

In the present work, an investigation on the influence of the chemical environment on the sedimentation behaviour of bentonite suspensions is performed with particular reference to the effect of lime addition on the clay particle arrangement. The role of lime content, cation valence [...] Read more.

In the present work, an investigation on the influence of the chemical environment on the sedimentation behaviour of bentonite suspensions is performed with particular reference to the effect of lime addition on the clay particle arrangement. The role of lime content, cation valence and source of calcium ions is considered in the experimental work. At the microscale, particle interaction is analysed by means of zeta potential measurements. Soil fabric formation during sedimentation and its physical properties are inferred from dynamic light scattering measurements, sedimentation tests and Atterberg limits. The addition of cations to pore water promotes the flocculation of montmorillonite particles favouring the formation of particle aggregates, whose dimension depends on ion valence and concentration. The final height of sediments reflects the combined effect of the mutual interactions among particles and the development of secondary phases due to pozzolanic reactions. The influence of clay mineralogy and its effects on the physical properties of lime-treated bentonite is highlighted by comparison with experimental evidence on lime-treated kaolin. Full article

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

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19 pages, 8127 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Key Technologies for Surface-Borehole Transient Electromagnetic Systems and Applications

by Qingming Guo, Yurong Mao, Liangjun Yan, Wenhui Chen, Jupeng Yang, Xingbing Xie, Lei Zhou and Haojin Li

Minerals 2024, 14(8), 793; https://doi.org/10.3390/min14080793 - 31 Jul 2024

Cited by 1 | Viewed by 1326

Abstract

The nonferrous metal mines in China are rapidly depleting due to years of mining, and it has become difficult to identify new mineral resources in the periphery of the old mining area. In order to deal with this situation, advanced technologies and equipment [...] Read more.

The nonferrous metal mines in China are rapidly depleting due to years of mining, and it has become difficult to identify new mineral resources in the periphery of the old mining area. In order to deal with this situation, advanced technologies and equipment must be deployed. The borehole transient electromagnetic method (TEM) has become a key technology due to its deep investigative capabilities within conductive geological structures. In the present study, in order to meet the exploration needs at depths of less than 3000 m, surface-borehole TEM exploration was used to analyze the characteristics of electromagnetic signals generated by a long wire source and a large loop source, providing essential data for the development of key technologies, such as sensor parameter design and signal gain optimization of the TEM system in the borehole. This study discussed in detail two key technical problems as follows: firstly, the efficient synchronization mechanism between the ground transmitter system and the borehole electromagnetic signal acquisition system ensured the accuracy and timeliness of data acquisition; and secondly, the realization of mass storage technology, which effectively solved the problem of mass storage and real-time transmission of data in a deep borehole environment. The effectiveness of the surface-borehole TEM systems with a long wire source and a large loop source was verified by tests in real mines. The surface-borehole electromagnetic signal acquisition system developed in this study effectively collected electromagnetic signals in the borehole, and the results accurately reflected the stratigraphic information of mineral resources in the study area. This study can pave a new technical path for the exploration of deep and peripheral areas of non-ferrous metal mines and provide valuable experience and insights for mineral resource exploration in similarly complex geological environments. Full article

(This article belongs to the Special Issue Geophysical Signatures of Mineral Deposits in Tropical and Subtropical Settings)

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39 pages, 3950 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Expanded Insights into Martian Mineralogy: Updated Analysis of Gale Crater’s Mineral Composition via CheMin Crystal Chemical Investigations

by Shaunna M. Morrison, David F. Blake, Thomas F. Bristow, Nicholas Castle, Steve J. Chipera, Patricia I. Craig, Robert T. Downs, Ahmed Eleish, Robert M. Hazen, Johannes M. Meusburger, Douglas W. Ming, Richard V. Morris, Aditi Pandey, Anirudh Prabhu, Elizabeth B. Rampe, Philippe C. Sarrazin, Sarah L. Simpson, Michael T. Thorpe, Allan H. Treiman, Valerie Tu, Benjamin M. Tutolo, David T. Vaniman, Ashwin R. Vasavada and Albert S. Yen Show full author list Hide full author list

Minerals 2024, 14(8), 773; https://doi.org/10.3390/min14080773 - 29 Jul 2024

Cited by 7 | Viewed by 2268

Abstract

This study presents mineral composition estimates of rock and sediment samples analyzed with the CheMin X-ray diffraction instrument on board the NASA Mars Science Laboratory rover, Curiosity, in Gale crater, Mars. Mineral composition is estimated using crystal-chemically derived algorithms applied to X-ray [...] Read more.

This study presents mineral composition estimates of rock and sediment samples analyzed with the CheMin X-ray diffraction instrument on board the NASA Mars Science Laboratory rover, Curiosity, in Gale crater, Mars. Mineral composition is estimated using crystal-chemically derived algorithms applied to X-ray diffraction data, specifically unit-cell parameters. The mineral groups characterized include those found in major abundance by the CheMin instrument (i.e., feldspar, olivine, pyroxene, and spinel oxide). In addition to estimating the composition of the major mineral phases observed in Gale crater, we place their compositions in a stratigraphic context and provide a comparison to that of martian meteorites. This work provides expanded insights into the mineralogy and chemistry of the martian surface. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Mars: Everything You Need to Know about the Red Planet)

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15 pages, 2881 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

In Search of Phytoremediation Candidates: Eu(III) Bioassociation and Root Exudation in Hydroponically Grown Plants

by Max Klotzsche, Viktor Dück, Björn Drobot, Manja Vogel, Johannes Raff, Thorsten Stumpf and Robin Steudtner

Minerals 2024, 14(8), 754; https://doi.org/10.3390/min14080754 - 26 Jul 2024

Viewed by 971

Abstract

Lanthanides and actinides are emerging contaminants, but little is known about their uptake and distribution by plants and their interactions in the rhizosphere. To better understand the fate of these metals in plants, the bioassociation of 2, 20 and 200 µM Eu(III) by [...] Read more.

Lanthanides and actinides are emerging contaminants, but little is known about their uptake and distribution by plants and their interactions in the rhizosphere. To better understand the fate of these metals in plants, the bioassociation of 2, 20 and 200 µM Eu(III) by five hydroponically grown crops endemic to Europe was assessed. The metal’s concentration and its speciation were monitored by inductively coupled plasma mass spectrometry and laser spectroscopy, whereas root exudation was investigated by chromatographic methods. It has been shown, that Eu(III) bioassociation is a two-stage process, involving rapid biosorption followed by accumulation in root tissue and distribution to the stem and leaves. Within 96 h of exposure time, the plant induces a change of Eu(III) speciation in the liquid medium, from a predominant Eu(III)aquo species, as calculated by thermodynamic modelling, to a species with longer luminescence lifetime. Root exudates such as citric, malic, and fumaric acid were identified in the cultivation medium and affect Eu(III) speciation in solution, as was shown by a change in the thermodynamic model. These results contribute to a comprehensive understanding of the fate of lanthanides in the biosphere and provide a basis for further investigations with the chemical analogues Cm(III) and Am(III). Full article

(This article belongs to the Special Issue Radionuclide Interactions with Natural and Synthetic Solids)

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14 pages, 4332 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impacts of Impurity Removal Chemical Pretreatment Procedures on the Composition and Adsorption Properties of Bentonites

by Tatiana Koroleva, Victoria Krupskaya, Ekaterina Tyupina, Ivan Morozov, Pavel Kozlov, Boris Pokidko, Sergey Zakusin and Tatiana Zaitseva

Minerals 2024, 14(8), 736; https://doi.org/10.3390/min14080736 - 23 Jul 2024

Cited by 1 | Viewed by 1260

Abstract

This work is based on a detailed study of samples from three industrial bentonite deposits in Russia (10th Khutor, Zyryanskoe) and Kazakhstan (Taganskoe). The samples of the listed bentonites were undergoing stage-by-stage purification from carbonates, organic matter, and non-clay iron-bearing phase procedures. The [...] Read more.

This work is based on a detailed study of samples from three industrial bentonite deposits in Russia (10th Khutor, Zyryanskoe) and Kazakhstan (Taganskoe). The samples of the listed bentonites were undergoing stage-by-stage purification from carbonates, organic matter, and non-clay iron-bearing phase procedures. The conducted research revealed changes in the composition of bentonites already at the first stage of purification, which, however, were not noted for all bentonites, as well as a change in the forms of Fe in smectite structure. The latter is probably associated with changes in cis- and trans-vacant positions. Sorption characteristics with respect to ¹³⁷Cs are determined using the localization and charges in the smectite layer and the slight changes during purification, along with the specific surface area indicators. Full article

(This article belongs to the Special Issue Adsorption Properties and Environmental Applications of Clay Minerals)

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13 pages, 4021 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Accuracy and Precision of the Geopyörä Breakage Test

by Marcos Bueno, Thiago Almeida, Leonardo Lara, Malcolm Powell and Homero Delboni

Minerals 2024, 14(8), 738; https://doi.org/10.3390/min14080738 - 23 Jul 2024

Viewed by 905

Abstract

The Geopyörä breakage test uses two counter-rotating wheels to nip and crush rock specimens with a tightly controlled gap between rollers. This paper presents the detailed measures conducted to evaluate the accuracy and precision of energy measurements across various ore types using the [...] Read more.

The Geopyörä breakage test uses two counter-rotating wheels to nip and crush rock specimens with a tightly controlled gap between rollers. This paper presents the detailed measures conducted to evaluate the accuracy and precision of energy measurements across various ore types using the Geopyörä. Force measurement was assessed just for its precision. The outputs were compared directly to the drop weight test (DWT) measures of fragmentation at the same energy and fitted A and b parameters. Test reproducibility was evaluated using a Round-Robin methodology, testing several samples in multiple laboratories. The results confirmed that the new test has sufficient accuracy to match DWT results and excellent precision to assure reproducibility. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation: 3rd Edition)

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27 pages, 380 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Uses of Ionic Liquids in the Recovery and Utilization of Rare Earth Elements

by Francisco Jose Alguacil, Jose Ignacio Robla and Olga Rodriguez Largo

Minerals 2024, 14(7), 734; https://doi.org/10.3390/min14070734 - 22 Jul 2024

Cited by 4 | Viewed by 2218

Abstract

The importance of rare earth elements as a basis for the development of new technologies or the improvement of existing ones makes their recovery from raw and waste materials necessary. In this recovery, hydrometallurgy and its derivative solvometallurgy play key roles due to [...] Read more.

The importance of rare earth elements as a basis for the development of new technologies or the improvement of existing ones makes their recovery from raw and waste materials necessary. In this recovery, hydrometallurgy and its derivative solvometallurgy play key roles due to their operational characteristics, which are emphasized with the use of ionic liquids. This manuscript reviews the most recent advances (2023 and 2024) in the use of ionic liquids in unit operations (leaching and separation technologies) aimed at the recovery of these valuable and strategic metals. Moreover, a comprehensive review is presented of the use of these chemicals in the development of advanced materials containing some of these rare earth elements. Full article

(This article belongs to the Special Issue Solvent Extraction of Rare-Earth Elements with Ionic Liquids and Deep Eutectic Solvents)

12 pages, 5585 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

FIB-SEM Study of Archaeological Human Petrous Bones: 3D Structures and Diagenesis

by Jamal Ibrahim, Eugenia Mintz, Lior Regev, Dalit Regev, Ilan Gronau, Steve Weiner and Elisabetta Boaretto

Minerals 2024, 14(7), 729; https://doi.org/10.3390/min14070729 - 21 Jul 2024

Viewed by 1340

Abstract

The petrous bone generally preserves ancient DNA better than other fossil bones. One reason for this is that the inner layer of the petrous bone of pigs and humans contains about three times as many osteocytes as other bones, and hence more DNA. [...] Read more.

The petrous bone generally preserves ancient DNA better than other fossil bones. One reason for this is that the inner layer of the petrous bone of pigs and humans contains about three times as many osteocytes as other bones, and hence more DNA. A FIB-SEM study of modern pig petrous bones showed that the 3D structure of the thin inner layer is typical of woven bone that forms in the fetus, whereas the thicker outer layer has a lamellar structure. The lamellar structure is common in mammalian bones. Here we study human petrous bones that are about 2500 years old, obtained from three Phoenician sites in Sicily, Italy. A detailed FIB-SEM study of two of these bones, one well preserved and the other poorly preserved, shows that the 3D bone type structure of the human petrous inner layer is woven bone, and the outer layer is lamellar bone. These are the same bone type structures found in pig petrous bones. Furthermore, by comparing nine differently preserved petrous bones from the same archaeological region and age, we show that their collagen contents vary widely, implying that organic material can be significantly altered during diagenesis. The mineral crystals are better preserved and hence less crystalline in the inner layers compared to the outer layers. We therefore infer that the best-preserved DNA in fossil petrous bones should be found in the thin inner layers immediately adjacent to the otic cavity where much more DNA is initially present and the mineral phase tends to be better preserved. Full article

(This article belongs to the Section Biomineralization and Biominerals)

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20 pages, 4968 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Characterization of Incremental Markings in the Sagittal Otolith of the Pacific Sardine (Sardinops sagax) Using Different Imaging Modalities

by Kelsey C. James, Uwe Kierdorf, Victoria Cooley, Viktor Nikitin, Stuart R. Stock and Horst Kierdorf

Minerals 2024, 14(7), 705; https://doi.org/10.3390/min14070705 - 12 Jul 2024

Viewed by 4129

Abstract

Teleost fish possess calcium carbonate otoliths located in separate chambers (utriculus, sacculus, and lagena) of their membranous labyrinth. This study analyzed the surface topography of the sagittal otolith of the Pacific sardine (Sardinops sagax) and the daily and annual increments in [...] Read more.

Teleost fish possess calcium carbonate otoliths located in separate chambers (utriculus, sacculus, and lagena) of their membranous labyrinth. This study analyzed the surface topography of the sagittal otolith of the Pacific sardine (Sardinops sagax) and the daily and annual increments in these otoliths. The otolith surface, characterized by laser scanning confocal microscopy for the first time, consisted of a system of prominent ridges and valleys (grooves), but it is unclear whether these structures are functional or represent time-resolving markings reflecting growth periodicity. Within the first-year volume, daily increments, each consisting of an incremental (more mineralized) and a discontinuous (less mineralized) zone, were resolved by optical microscopy and backscattered electron (BSE) imaging in the scanning electron microscope (SEM). Daily growth increments could, however, not be resolved in volumes formed after the first year, presumably because otolith growth markedly slows down and spacing of incremental markings narrows in older fish. Throughout otolith growth, the crystalline network continues across the discontinuous zones. Fluorochrome labeling provides additional information on growth after the first year. Compared with optical and BSE imaging, synchrotron microComputed Tomography of intact otoliths (with 0.69 µm volume elements) was less able to resolve daily increments; X-ray phase contrast reconstructions provided more detail than reconstructions with absorption contrast. Future research directions are proposed. Full article

(This article belongs to the Special Issue Skeletal Tissues Mineralization)

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21 pages, 3649 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparing the Performance of Hydrocyclones and High-Frequency Screens in an Industrial Grinding Circuit: Part I—Size Separation Assessments

by Bruna Silveira Costa, Maurício Guimarães Bergerman and Homero Delboni Júnior

Minerals 2024, 14(7), 707; https://doi.org/10.3390/min14070707 - 12 Jul 2024

Cited by 1 | Viewed by 1243

Abstract

Industrial ball milling circuits usually include hydrocyclones in a closed configuration to achieve a specified grinding size. Although hydrocyclones are relatively simple to operate, their classification performance is generally low, leading to significant fines recirculation within the circuit, consequently overgrinding the product. Conversely, [...] Read more.

Industrial ball milling circuits usually include hydrocyclones in a closed configuration to achieve a specified grinding size. Although hydrocyclones are relatively simple to operate, their classification performance is generally low, leading to significant fines recirculation within the circuit, consequently overgrinding the product. Conversely, high-frequency screening potentially shows a relatively higher separation efficiency, as the entrainment of fines to the coarse product is significantly reduced. The present work compares the performance of hydrocyclones—HC and high-frequency screens—HFS based on four surveys conducted in Nexa’s Vazante Zinc ore industrial grinding circuit in Vazante, Brazil, which processes zinc silicate ore. The comparisons included the partition of solids, water split, and particle size distributions. Whiten’s partition curve model was adopted to obtain the selected performance parameters through mass balancing the experimental data. The industrial surveys comprised three different size separation configurations, i.e., HC-Only, HFS-Only, and a combined HC-HFS setup. In all cases, the assessments consistently indicated higher separation performances with HFS compared to the HC operation. The final product associated with the HC+HFS configuration showed a narrower size distribution around the grinding size. Full article

(This article belongs to the Special Issue Advances in Mineral Processing and Extractive Metallurgy of Base and Precious Metals)

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22 pages, 23827 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Role of Hydrocarbons in the Formation of Uranium Mineralization, Louzhuangzi District, Southern Junggar Basin (China)

by Zhong-Bo He, Bao-Qun Hu, Lin-Fei Qiu, Yun Wang, Hong Chen, Wei-Wei Jia, Yi-Fei Li, Hua-Li Ji and Man-Huai Zhu

Minerals 2024, 14(7), 709; https://doi.org/10.3390/min14070709 - 12 Jul 2024

Viewed by 1194

Abstract

In recent years, there have been important breakthroughs in the exploration for sandstone-hosted uranium (U) deposits in the Louzhuangzi district of the southern Junggar Basin. Between 2020 and 2023, a medium-sized sandstone-hosted uranium deposit production area was identified in the region. Only a [...] Read more.

In recent years, there have been important breakthroughs in the exploration for sandstone-hosted uranium (U) deposits in the Louzhuangzi district of the southern Junggar Basin. Between 2020 and 2023, a medium-sized sandstone-hosted uranium deposit production area was identified in the region. Only a few investigations have been conducted at the Louzhuangzi U deposit, including those analyzing its geological–tectonic evolution, basic geological features, hydrogeology, and ore-controlling factors. It is generally believed that uranium mineralization at the Louzhuangzi U deposit is controlled by a redox zone. Organic matter (referred to as OM hereafter) consisting of bitumen and carbonaceous debris is very common in the uranium ores (especially in high-grade ores) at the Louzhuangzi U deposit. However, the characteristics of the OM and its contribution to uranium’s mineralization have not been studied in detail. In this study, OM-rich U-ores, altered sandstone, and barren sandstone samples were collected for petrography, mineralogical, micro-spectroscopy, carbon, and sulfur isotope studies. The results of this study show that the distribution of U minerals and metal sulfides (pyrite, sphalerite, etc.) was strictly controlled by bitumen at the Louzhuangzi U deposit. The bitumen may have been formed by hydrocarbon-rich and U-rich ore-forming fluids, which were formed after hydrocarbon generation and expulsion in the underlying Jurassic coal-bearing source rocks. The fluids contained U, Zn, Fe, and other metal elements, which migrated together and then precipitated into the oxidized Toutunhe Formation sandstone through cracking and differentiation processes. Therefore, the results indicate that migrated hydrocarbons were involved in U mineralization, in addition to oxidation–reduction processes, in the Louzhuangzi district, south of the Junggar Basin (China). Full article

(This article belongs to the Special Issue Uranium: Geochemistry and Mineralogy)

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21 pages, 4452 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Crystallization Sequence of the Spodumene-Rich Alijó Pegmatite (Northern Portugal) and Related Metasomatism on Its Host Rock

by Idoia Garate-Olave, Encarnación Roda-Robles, Nora Santos-Loyola, Tania Martins, Alexandre Lima and Jon Errandonea-Martin

Minerals 2024, 14(7), 701; https://doi.org/10.3390/min14070701 - 9 Jul 2024

Cited by 1 | Viewed by 1889

Abstract

The Barroso–Alvão region is an excellent setting for studying Li mineralization associated with granitic pegmatites and developing Li exploration techniques. Among the distinguished pegmatite types in this pegmatite field, the spodumene-bearing dyke from Alijó is a representative example of an Iberian Li–Cs–Ta (LCT) [...] Read more.

The Barroso–Alvão region is an excellent setting for studying Li mineralization associated with granitic pegmatites and developing Li exploration techniques. Among the distinguished pegmatite types in this pegmatite field, the spodumene-bearing dyke from Alijó is a representative example of an Iberian Li–Cs–Ta (LCT) pegmatite currently under exploitation. In this work, we examine the internal evolution of the Alijó dyke and its external metasomatic effect on the surrounding metasediments, contributing to lithium exploration techniques. Electron microprobe analyses provided clues about the crystallization conditions and the degree of differentiation of the pegmatitic melt, whereas the external metasomatism induced by the spodumene-bearing pegmatite was studied through whole-rock geochemistry. The obtained results indicate that the primary crystallization of the studied dyke likely occurred at temperatures between 450–500 °C, with emplacement at shallow crustal levels of about 2–3 kbar. The high concentrations of trace elements such as Li, Cs, Rb, Be, Sn, Nb, Ta, Ge, U, and Tl in the pegmatitic melt suggests high availability of these elements, allowing their partitioning into an early exsolved fluid phase. The exsolution of this fluid phase, subtracting components such as F and B, from the pegmatitic melt would cause a significant undercooling of the melt. Moreover, the interaction of this expelled fluid with the country rock generated a metasomatic overprint in the surrounding metasedimentary host rocks. The metasomatic effect in Alijó is strongly influenced by the nature of the host metasediments, with a significantly higher grade of metasomatism observed in pelitic (mica-rich) samples compared to psammitic (mica-poor) samples collected at same distances from the dyke. The greisen developed close to the pegmatite contact reflects this metasomatic signature, characterized by the mobilization of at least B, F, Li, Rb, Cs, Sn, Be, Nb, Ta, and Tl. We cautiously suggest that whole rock Li concentrations greater than 300 ppm, combined with a minimum value of 1000 ppm for the sum of B, F, Li, Rb, Cs, and Sn in pelitic metasediments of Barroso–Alvão, may be indicative of a mineralized pegmatite in this region. Full article

(This article belongs to the Special Issue Rare Metal and Related Deposits: Geology, Geochemistry and Mineralization)

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16 pages, 7601 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver

by Kechen Liu, Michal Slaný, Alena Golian-Struhárová, Hailong Wang, Liyuan Zhang, Jiyou Fu, Gang Chen and Yingna Du

Minerals 2024, 14(7), 696; https://doi.org/10.3390/min14070696 - 8 Jul 2024

Viewed by 1414

Abstract

In view of the problem of poor flowability in the production and transportation of high-wax crude oil and high-viscosity crude oil, crude oil flow improvers are commonly used to reduce their viscosity and pour point. Although polymer-based crude oil flow improvers are highly [...] Read more.

In view of the problem of poor flowability in the production and transportation of high-wax crude oil and high-viscosity crude oil, crude oil flow improvers are commonly used to reduce their viscosity and pour point. Although polymer-based crude oil flow improvers are highly effective in improving crude oil flowability, there are still problems such as high cost and the need for a large amount of solvent dilution when used. In this work, highly dispersed organic modified nano-montmorillonite was prepared by using Na-based montmorillonite and quaternary ammonium salts, and the influencing factors on the viscosity of the crude oil were investigated. The most effective modified nano-montmorillonite (B@MMT) can reduce the viscosity by 96.7% (21 °C) and depress the pour point by 15 °C. Furthermore, it has shown a high improvement in flowability in the other four different sources of crude oil, with viscosity reduction rates of 52.2, 93.4, 79.1 and 67.4%, respectively. B@MMT was characterized by FTIR, SEM, zeta potential and contact angle. Based on DSC and wax crystal structure analysis, the mechanism of the influence of B@MMT on crude oil viscosity and pour point was explored. Finally, the cost of B@MMT was estimated, and the result shows that, compared with the crude oil flow improver in use, B@MMT has considerable commercial competitive advantages. Full article

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

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18 pages, 11734 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhancing Rare Earth Element Recovery from Coal Ash Using High-Voltage Electrical Pulses and Citric Acid Leaching

by Tlek Ketegenov, Kaster Kamunur, Lyazzat Mussapyrova, Aisulu Batkal and Rashid Nadirov

Minerals 2024, 14(7), 693; https://doi.org/10.3390/min14070693 - 3 Jul 2024

Cited by 1 | Viewed by 1644

Abstract

The study investigates the application of high-voltage electrical pulses (HVEP) as a pretreatment to enhance the leaching efficiency of rare earth elements (REE) from coal ash (CA) produced from the combustion of Ekibastuz Basin coal in Almaty, Kazakhstan. HVEP treatment was applied to [...] Read more.

The study investigates the application of high-voltage electrical pulses (HVEP) as a pretreatment to enhance the leaching efficiency of rare earth elements (REE) from coal ash (CA) produced from the combustion of Ekibastuz Basin coal in Almaty, Kazakhstan. HVEP treatment was applied to the finest (<40 µm) non-magnetic fraction of CA under controlled conditions, optimizing discharge current, voltage, and treatment duration. Leaching experiments with 1 M citric acid at various solid-to-liquid ratios, temperatures, and durations were conducted on both treated and untreated samples. Results indicated that HVEP-treated CA significantly improved REE recovery rates compared to untreated samples, with optimal conditions achieving 74% cerium, 79% yttrium, and 77% lanthanum recovery. The leaching of untreated CA under the specified conditions allowed no more than 28% REE to be extracted into the solution. The leaching process was found to follow first-order kinetics, with the chemical reaction of metal dissolution being the rate-limiting step. Full article

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

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28 pages, 16832 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Tepsi Ultrabasic Intrusion, the Northern Part of the Lapland–Belomorian Belt, Kola Peninsula, Russia

by Andrei Y. Barkov, Andrey A. Nikiforov, Robert F. Martin, Sergey A. Silyanov and Boris M. Lobastov

Minerals 2024, 14(7), 685; https://doi.org/10.3390/min14070685 - 29 Jun 2024

Cited by 2 | Viewed by 1069

Abstract

The Tepsi ultrabasic body is located in the northeastern Fennoscandian Shield close to the junction of the Serpentinite Belt–Tulppio Belt (SB–TB) with suites of the Lapland–Belomorian Belt (LBB) of Paleoproterozoic age. The body is a deformed laccolith that has tectonic contacts with Archean [...] Read more.

The Tepsi ultrabasic body is located in the northeastern Fennoscandian Shield close to the junction of the Serpentinite Belt–Tulppio Belt (SB–TB) with suites of the Lapland–Belomorian Belt (LBB) of Paleoproterozoic age. The body is a deformed laccolith that has tectonic contacts with Archean rocks. Its primary textures and magmatic parageneses are widely preserved. Fine-grained olivine varies continuously from Fo_90.5 to Fo_65.4. The whole-rock variations in MgO, Fe₂O₃, SiO₂, and other geochemical data are also indicative of a significant extent of differentiation. Compositional variations were examined in the grains of calcic and Mg-Fe amphiboles, clinochlore, micas, plagioclase, members of the chromite–magnetite series, ilmenite, apatite, pentlandite, and a number of other minor mineral species. Low-sulfide disseminated Ni-Cu-Co mineralization occurred sporadically, with the presence of species enriched in As or Bi, submicrometric grains rich in Pt and Ir, or diffuse zones in pentlandite enriched in (Pd + Bi). We recognize two series: the pentlandite series (up to 2.5–3 wt.% Co) and the cobaltpentlandite series (~1 to ~8 apfu Co). The latter accompanied serpentinization. The two series display differences in their substitutions: Ni ↔ Fe and Co → (Ni + Fe), respectively. Relative enrichments in H₂O, Cl, and F, observed in grains of apatite (plus high contents of Cl in hibbingite or parahibbingite), point to the abundance of volatiles accumulated during differentiation. We provide the first documentation of scheelite grains in ultrabasic rocks, found in evolved olivine-rich rocks (Fo_77–72). We also describe unusual occurrences of hypermagnesian clinopyroxene associated with tremolite and serpentine. Abundant clusters of crystallites of diopside display a microspinifex texture. They likely predated serpentinization and formed owning to rapid crystallization in a differentiated portion of a supercooled oxidized melt or, less likely, fluid, after bulk crystallization of the olivine. We infer that the laccolithic Tepsi body crystallized rapidly, in a shallow setting, and could thus not form megacycles in a layered series or produce a well-organized structure. Our findings point to the existence of elevated PGE-Au-Ag potential in numerous ultrabasic–basic complexes of the SB–TB–LBB megastructure. Full article

(This article belongs to the Special Issue From Mantle to Market: Platinum Group Elements and Minerals and Their Geological Significance)

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15 pages, 3423 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Preparation of Humic Acid from Weathered Coal by Mechanical Energy Activation and Its Properties

by Xiujuan Feng, Rilong Xiao, Sékou Mohamed Condé, Chengliang Dong, Yanping Xun, Dalong Guo, Hui Liu, Kunpeng Liu and Mingzhi Liang

Minerals 2024, 14(7), 648; https://doi.org/10.3390/min14070648 - 25 Jun 2024

Cited by 1 | Viewed by 2091

Abstract

Humic acid (HA) is rich in functional groups with high activity, which can effectively improve the soil environment. The large reserves of weathered coal in China provide sufficient raw material guarantee for HA extraction and utilization. At present, the activation side of weathered [...] Read more.

Humic acid (HA) is rich in functional groups with high activity, which can effectively improve the soil environment. The large reserves of weathered coal in China provide sufficient raw material guarantee for HA extraction and utilization. At present, the activation side of weathered coal is still the main technical difficulty that restricts HA extraction. In this study, the weathered coal from Inner Mongolia was used as the raw material, and the mechanical energy was used to activate the weathered coal through a planetary ball mill, which improved the extraction rate of HA and optimized the molecular structure and composition of HA. The effects of four parameters, namely, ball material ratio, ball milling time, ball milling speed, and ball size, on the free HA content of weathered coal were investigated, the HA was extracted by alkaline extraction method, and the activated weathered coal and the extracted HA were characterized. The results showed that a ball material ratio of 9:1, a ball milling speed of 200 r/min, a ball milling time of 200 min, a milling ball size of Ф5:Ф10:Ф15 = 48:42:45 and 56:42:37 are the optimal parameters for the mechanical energy activation, and the HA extraction rate of activated weathered coal under these conditions reached 82.3%, which was 15% higher than that of the unactivated one. Moreover, the aroma of the ball-milled weathered coal increased, the content of oxygenated functional groups increased, and the molecular weight and aroma of HA increased. This provides scientific theoretical guidance for the preparation of HA with high aromaticity and large molecular weight from weathered coal. Full article

(This article belongs to the Special Issue Waste Minerals, Sediments and Their Environmental Mineralogy)

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20 pages, 9384 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Petrogenetic Implications of the Lithium-Rich Tongtianmiao Granite Pluton, South China: Evidence from Geochemistry and Geochronology

by Xinhui Yu, Yongzhang Zhou, Wei Cao, Hanyu Wang, Can Zhang, Lifeng Zhong, Wu Wei, Zhiqiang Wang, Jianying Yao, Zhiqiang Chen and Qinghe Xu

Minerals 2024, 14(7), 637; https://doi.org/10.3390/min14070637 - 21 Jun 2024

Viewed by 1405

Abstract

The South China Block, a region renowned for its extensive granite distribution and rich metal deposits, serves as a natural laboratory for the study of granite-related mineralization. This research focuses on the Tongtianmiao granite pluton, which is located at the intersection of the [...] Read more.

The South China Block, a region renowned for its extensive granite distribution and rich metal deposits, serves as a natural laboratory for the study of granite-related mineralization. This research focuses on the Tongtianmiao granite pluton, which is located at the intersection of the Qin-Hang and Nanling metallogenic belts and has been confirmed as a significant lithium mineral resource. Despite its discovery and ongoing development, the lithium-rich Tongtianmiao pluton has been understudied, particularly concerning its petrogenesis, which has only recently come to the forefront of scientific inquiry. By integrating an array of petrogeochemical data with geochronological studies derived from zircon and monazite dating, this study provides insights into the magmatic processes related to lithium enrichment in the Tongtianmiao granites. The Tongtianmiao granites are classified as A-type granites characterized by high SiO₂ contents (69.18–78.20 wt.%, average = 74.08 wt.%), K₂O + Na₂O contents (4.59–8.34 wt.%, average = 6.86 wt.%), A/CNK > 1.2, and low concentrations of Ca, Mg, and Fe. These granites are enriched in alkali metals such as Li, Rb, and Cs but are significantly depleted in Ba, Sr, and Eu. They show no significant fractionation of light or heavy rare-earth elements but present characteristic tetrad effects. A finding of this study is the identification of multiple ages from in situ zircon U–Pb dating, which implies a prolonged history of magmatic activity. However, given the high uranium content in zircons, which could render U–Pb ages unreliable, emphasis is placed on the monazite U–Pb ages. These ages cluster at approximately 172.1 ± 1.1 Ma and 167.9 ± 1.6 Ma, indicating a Middle Jurassic period of granite formation. This timing correlates with the retreat of the Pacific subduction plate and the associated NE-trending extensional fault activity, which likely provided favorable conditions for lithium enrichment. The study concluded that the Tongtianmiao granites were formed through partial melting of crustal materials and subsequent underplating by mantle-derived materials, and were contaminated by strata materials. This process resulted in the formation of highly differentiated granite through magmatic differentiation and external forces. These findings have significant implications for understanding the petrogenesis of lithium-rich granites and are expected to inform future exploration endeavors in the Tongtianmiao pluton. Full article

(This article belongs to the Special Issue In-Situ Microanalytical Techniques in Geological and Geochronological Research)

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25 pages, 3064 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Catalytic Potential of Modified Clays: A Review

by Altantuya Ochirkhuyag and Jadambaa Temuujin

Minerals 2024, 14(6), 629; https://doi.org/10.3390/min14060629 - 20 Jun 2024

Cited by 5 | Viewed by 3332

Abstract

The need for innovative catalysts and catalytic support materials is continually growing due to demanding requirements, stricter environmental demands, and the ongoing development of new chemical processes. Since about 80% of all industrial processes involve catalysts, there is a continuing need to develop [...] Read more.

The need for innovative catalysts and catalytic support materials is continually growing due to demanding requirements, stricter environmental demands, and the ongoing development of new chemical processes. Since about 80% of all industrial processes involve catalysts, there is a continuing need to develop new catalyst materials and supports with suitable qualities to meet ongoing industrial demands. Not only must new catalysts have tailored properties, but they must also be suitable for large-scale production through environmentally friendly and cost-effective processes. Clay minerals, with their rich history in medicine and ceramics, are now emerging as potential catalysts. Their transformative potential is exemplified in applications such as hydrogenating the greenhouse gas CO₂ into carbohydrate fuel, a crucial step in meeting the rising electrical demand. Moreover, advanced materials derived from clay minerals are proving their mettle in diverse photocatalytic reactions, from organic dye removal to pharmaceutical pollutant elimination and photocatalytic energy conversion through water splitting. Clay minerals in their natural state show a low catalytic activity, so to increase their reactivity, they must be activated. Depending on the requirements of a particular application, selecting an appropriate activation method for modifying a natural clay mineral is a critical consideration. Traditional clay mineral processing methods such as acid or alkaline treatment are used. Still, these have drawbacks such as high costs, long processing times, and the formation of hazardous by-products. Other activation processes, such as ultrasonication and mechanical activation routes, have been proposed to reduce the production of hazardous by-products. The main advantage of ultrasonication and microwave-assisted procedures is that they save time, whereas mechanochemical processing is simple and efficient. This short review focuses on modifying clay minerals using various new methods to create sophisticated and innovative new materials. Recent advances in catalytic reactions are specifically covered, including organic biogeochemical processes, photocatalytic processes, carbon nanotube synthesis, and energy conversion processes such as CO₂ hydrogenation and dry reforming of methane. Full article

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

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12 pages, 4631 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Surface Wettability Analysis from Adsorption Energy and Surface Electrical Charge

by Chen Zhang, Xuming Wang, Lixia Li, Jan D. Miller and Jiaqi Jin

Minerals 2024, 14(6), 628; https://doi.org/10.3390/min14060628 - 20 Jun 2024

Cited by 2 | Viewed by 1733

Abstract

Surface wettability is determined by the attraction of a liquid phase to a solid surface. It is typically quantified by using contact angle measurements at mineral surfaces in the case of the flotation of mineral particles. Contact angle research to describe wettability has [...] Read more.

Surface wettability is determined by the attraction of a liquid phase to a solid surface. It is typically quantified by using contact angle measurements at mineral surfaces in the case of the flotation of mineral particles. Contact angle research to describe wettability has been investigated at different scales by sessile drop measurements, molecular dynamic simulation, and atomic force microscopy. In this study, the density functional theory (DFT) was employed for predicting the surface free energy and contact angles of a well-known hydrophobic phyllosilicate mineral talc and a well-known hydrophilic phyllosilicate mineral muscovite based on the calculated interfacial energy and surface charge. The results revealed that the predicted contact angle at the atomic scale was larger than the experimental value, and identified two interactions: electrostatic interaction and hydrogen bonding, between the hydrophilic muscovite surface and the water layer, while a water-exclusion zone of 3.346 Å was found between the hydrophobic talc surface and the first water layer. This investigation gives a new perspective for wettability determination at the atomic scale. Full article

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

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20 pages, 2190 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Quantification of Feldspar and Quartz Nucleation Delay in a Hydrous Peraluminous Granitic Melt

by Maude Bilodeau and Don R. Baker

Minerals 2024, 14(6), 611; https://doi.org/10.3390/min14060611 - 15 Jun 2024

Viewed by 1158

Abstract

A modified model based on classical nucleation theory was applied to a natural hydrous peraluminous pegmatite composition and tested against crystallization experiments in order to further investigate the quantification of nucleation delay in felsic melts. Crystallization experiments were performed in a piston-cylinder apparatus [...] Read more.

A modified model based on classical nucleation theory was applied to a natural hydrous peraluminous pegmatite composition and tested against crystallization experiments in order to further investigate the quantification of nucleation delay in felsic melts. Crystallization experiments were performed in a piston-cylinder apparatus at 630 MPa and temperatures between 650 and 1000 °C for durations ranging from 0.3 to 211 h. Experimental run products were investigated by scanning electron microscopy paired with energy dispersive spectroscopy analyses of both crystalline and quenched liquid phases, the results of which were compared to an established theoretical nucleation delay model from the literature. The experiments showed good agreement (within a factor of 5) with the model for quartz, while it showed moderate agreement (within a factor of 10) with the model for sodic feldspar. Other crystals also nucleated, demonstrating abundant features of disequilibrium. Our research further demonstrates the potential of the model to predict nucleation delay, showing promising results for the quantification of the nucleation delay of quartz and feldspar in natural felsic melts, thus adding to previously published studies on hydrous, metaluminous, felsic melts and dry basaltic melts. Full article

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

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27 pages, 2235 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Clay Minerals and Biopolymers in Film Design: Overview of Properties and Applications

by Pollyana Trigueiro, Juliane P. de L. Pereira, Mirelly G. Ferreira, Lucas B. Silva, Luan Neves and Ramón R. Peña-Garcia

Minerals 2024, 14(6), 613; https://doi.org/10.3390/min14060613 - 15 Jun 2024

Cited by 3 | Viewed by 2045

Abstract

Research to replace petroleum-based plastics has been quite challenging. Currently, there is a lot of interest in biopolymers as an alternative. However, biopolymers do not have suitable mechanical properties when in film form, which limits their applications. To resolve this issue, clay minerals [...] Read more.

Research to replace petroleum-based plastics has been quite challenging. Currently, there is a lot of interest in biopolymers as an alternative. However, biopolymers do not have suitable mechanical properties when in film form, which limits their applications. To resolve this issue, clay minerals are being incorporated as a strategy. Clay minerals offer the films good barrier, thermal, rheological, optical, and mechanical properties. They can also work with other additives to promote antioxidant and antimicrobial activity. This brief review focuses on incorporating clay minerals with other nanofillers and bioactives to improve their physical, chemical, and functional characteristics. The synergy of these materials gives the films exceptional properties and makes them suitable for applications such as food coatings, packaging materials, dressings, and bandages for treating skin wounds. Full article

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

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20 pages, 4455 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Bulk and Surface Characterization of Distinct Hematite Morphology: Implications for Wettability and Flotation Response

by Lívia Marques Faustino, Belinda McFadzean, José Tadeu Gouvêa Junior and Laurindo de Salles Leal Filho

Minerals 2024, 14(6), 609; https://doi.org/10.3390/min14060609 - 14 Jun 2024

Cited by 1 | Viewed by 1933

Abstract

To understand why hematite of different genesis behave diversely in flotation systems, this study assesses the flotation response at pH 5 of bulk (morphology, texture, Crystal Preferential Orientation (CPO)) plus interfacial (surface area, zeta potential, immersion enthalpy, contact angle, induction time) characteristics of [...] Read more.

To understand why hematite of different genesis behave diversely in flotation systems, this study assesses the flotation response at pH 5 of bulk (morphology, texture, Crystal Preferential Orientation (CPO)) plus interfacial (surface area, zeta potential, immersion enthalpy, contact angle, induction time) characteristics of species formed under distinct metamorphic conditions: low-strain deformation (Hematite-1) versus high-strain deformation (Hematite-2). Hematite-2 (predominantly composed of specular and lamellar morphologies) shows (001) CPO and exhibits fewer Fe sites on its surface that undergo doubly coordinated Fe-OH when exposed to moisture. This results in a less reactive surface associated with a less ordered adsorbed water layer than Hematite-1, which is predominantly composed of granular and sinuous hematite. Those characteristics lead to a naturally hydrophobic behavior characterized by the exothermic energy below the Critical Immersion Enthalpy (

- {∆ H}_{i m m}

< 200 mJ/m²), lower values of zeta potential due to attenuated dissociation of Fe-OH_(surf), lower induction time (47 ms vs. 128 ms), higher contact angle (39° vs. 13°), and higher flotation recovery (21% vs. 12%) than Hematite-1. Full article

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

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16 pages, 12704 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Provenance Studies of Natural Stones Used in Historical Buildings of the Peninsula de Barbanza, Galicia, Spain (North-Western Iberia)

by Ana C. Hernández, Jorge Sanjurjo-Sánchez, Carlos Alves and Carlos A. M. Figueiredo

Minerals 2024, 14(6), 595; https://doi.org/10.3390/min14060595 - 5 Jun 2024

Viewed by 1138

Abstract

Traditionally, the building stones used in the architectural heritage of Galicia (Spain) during the past were mainly extracted from quarries located in the surrounding areas of the historical buildings. Thus, a great variety of monuments were built with the same type of granite [...] Read more.

Traditionally, the building stones used in the architectural heritage of Galicia (Spain) during the past were mainly extracted from quarries located in the surrounding areas of the historical buildings. Thus, a great variety of monuments were built with the same type of granite but with different degrees of weathering depending on local conditions, geological context (facies), and period of construction. The main purpose of this work is to evaluate the probable origin of the construction materials of six historical buildings on the Barbanza Peninsula, Galicia (Spain), based on the degree of weathering and petrographic-mineralogical characteristics. The evaluation was performed on six different samples of granite according to the geological context in outcrops of places where there are old quarries. We used X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), and petrographic microscopy (PM) to attempt to address whether the origin is really local to the Barbanza Peninsula or whether the stone was brought from more distant places, based on our knowledge of the geological context of the study area. Based on the chemical, textural, and mineralogical analyses obtained, the material used for construction has a local origin and comes from small quarries spread over a wide area within the Peninsula itself. Barbanza-type granite is the most abundant within the geological context of the area and also the most used as a construction material. Other types of granites identified are the Confurco Granite and other granitoids of the Noya complex. The Chemical Alteration Index (CIA) shows low to moderate weathering in the granites, fitting petrographic observations. In monuments, samples show higher concentrations of Na and K due to salt crystallization. They show microcracks due to extraction, cutting, and finishing processes and common alteration processes of the main minerals, such as sericitization of plagioclase and chloritization of biotite. This work consists of a multidisciplinary study focused on the geological perspective for the identification and preservation of historic quarries. Knowledge of the original material also presents a unique opportunity for the restoration and/or reconstruction of monuments, which allows for the maintenance of their conceptual and constructive homogeneity. Full article

(This article belongs to the Special Issue Natural and Artificial Building Stones: Insights from Petrophysical Properties and Consolidation Procedures)

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34 pages, 8938 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Phosphates on Mars and Their Importance as Igneous, Aqueous, and Astrobiological Indicators

by E. M. Hausrath, C. T. Adcock, J. A. Berger, L. M. Cycil, T. V. Kizovski, F. M. McCubbin, M. E. Schmidt, V. M. Tu, S. J. VanBommel, A. H. Treiman and B. C. Clark

Minerals 2024, 14(6), 591; https://doi.org/10.3390/min14060591 - 4 Jun 2024

Cited by 2 | Viewed by 3027

Abstract

This paper reviews the phosphate phases in meteorites and those measured by landed spacecraft, what they reveal about past igneous and aqueous conditions on Mars, and important implications for potential prebiotic chemistry, past habitability, and potential biosignatures that could be detected in samples [...] Read more.

This paper reviews the phosphate phases in meteorites and those measured by landed spacecraft, what they reveal about past igneous and aqueous conditions on Mars, and important implications for potential prebiotic chemistry, past habitability, and potential biosignatures that could be detected in samples returned from Mars. A review of the 378 martian meteorites as of 2023 indicate that of the two most common phosphate minerals in Mars meteorites, merrillite and apatites, the apatite composition is largely F- and Cl-rich, with shergottites containing more OH. The phosphate concentrations examined across multiple missions show a relatively narrow range of phosphate, with higher concentrations observed in the Mount Sharp Group in Gale crater and Wishstone at Gusev crater and lower concentrations observed at Jezero crater floor and Jezero fan. Possible secondary phosphates detected on Mars, including Fe phosphates at Jezero crater and Gusev crater and Ca- and Al-bearing secondary phosphates, temperatures of formation of secondary phases and their dissolution rates and solubilities are reviewed and summarized. Despite this wealth of information about phosphates on Mars, due to their fine scale and relatively low concentrations, Mars Sample Return is needed to better understand phosphate and its implications for the igneous, aqueous, and astrobiological history of Mars. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Mars: Everything You Need to Know about the Red Planet)

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10 pages, 2223 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Hydroclimate and Paleoenvironmental Variability from the Tonle Sap Lake Basin during the Angkor Period

by Xinnan Zhao, Jian Wang, Wei Zhao and Hai Cheng

Minerals 2024, 14(6), 581; https://doi.org/10.3390/min14060581 - 31 May 2024

Viewed by 945

Abstract

The profound impact of the Khmer Empire on Southeast Asia renders the Angkor Period particularly significant in guiding contemporary societies to advocate and promote policies that respond to climate change. We present a new continuous multi-proxy speleothem dataset from Tonle Sap Lake Basin, [...] Read more.

The profound impact of the Khmer Empire on Southeast Asia renders the Angkor Period particularly significant in guiding contemporary societies to advocate and promote policies that respond to climate change. We present a new continuous multi-proxy speleothem dataset from Tonle Sap Lake Basin, investigating hydroclimate variability and the paleoenvironment of Cambodia during the Angkor Period from the 9th to 15th centuries. In addition, two important climatic events on a decadal scale are clearly reconstructed. The first is the reduction of precipitation between 800 and 1000 AD and the relatively significant drought that the regional environment may have experienced from 950 to 1000 AD. The second is the anomalous wet period between 1000 and 1200 AD, during which the Southern Oscillation Index also reached its negative peak after a thousand years. The wet and dry conditions are highly consistent with the El Niño-dominated and northward Intertropical Convergence Zone. Full article

(This article belongs to the Special Issue Stalagmite Geochemistry and Its Paleoenvironmental Implication)

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28 pages, 4087 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advanced Processing Techniques and Impurity Management for High-Purity Quartz in Diverse Industrial Applications

by Hailin Long, Deqing Zhu, Jian Pan, Siwei Li, Congcong Yang and Zhengqi Guo

Minerals 2024, 14(6), 571; https://doi.org/10.3390/min14060571 - 30 May 2024

Cited by 10 | Viewed by 6466

Abstract

While numerous studies have explored the mineralogical characteristics and purification techniques of high-purity quartz (HPQ), discussions on impurity control during various purification processes and their applications in photovoltaics, electronics, and optics remain limited. This review delves into the adverse effects of impurities such [...] Read more.

While numerous studies have explored the mineralogical characteristics and purification techniques of high-purity quartz (HPQ), discussions on impurity control during various purification processes and their applications in photovoltaics, electronics, and optics remain limited. This review delves into the adverse effects of impurities such as aluminum, iron, and sodium in the manufacturing processes of these industries, emphasizing their critical role as these impurities can degrade material performance. This paper focuses on analyzing the types of impurities found in quartz and evaluates existing purification technologies such as acid washing, ultrasonic acid washing, chlorination roasting, and calcination quenching. It highlights the limitations of current technologies in processing quartz ore and discusses the advantages of different impurity types under various technological treatments. Moreover, it explores the environmental and economic impacts of these high-purity processes, underlining the necessity for more environmentally friendly and cost-effective purification techniques. The purpose of this review is to provide a comprehensive technical and strategic framework for the use of high-purity quartz in high-tech applications, supporting future research and industrial applications in this critical material field. Full article

(This article belongs to the Special Issue Advances in Mineral Processing and Extractive Metallurgy of Base and Precious Metals)

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44 pages, 21329 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Chemistry and Mineralogy (CheMin) X-ray Diffractometer on the MSL Curiosity Rover: A Decade of Mineralogy from Gale Crater, Mars

by David Blake, Valerie Tu, Thomas Bristow, Elizabeth Rampe, David Vaniman, Steve Chipera, Philippe Sarrazin, Richard Morris, Shaunna Morrison, Albert Yen, Robert Downs, Robert Hazen, Allan Treiman, Douglas Ming, Gordon Downs, Cherie Achilles, Nicholas Castle, Tanya Peretyazhko, David De Marais, Patricia Craig, Barbara Lafuente, Benjamin Tutolo, Elisabeth Hausrath, Sarah Simpson, Richard Walroth, Michael Thorpe, Johannes Meusburger, Aditi Pandey, Marc Gailhanou, Przemyslaw Dera, Jeffrey Berger, Lucy Thompson, Ralf Gellert, Amy McAdam, Catherine O’Connell-Cooper, Brad Sutter, John Michael Morookian, Abigail Fraeman, John Grotzinger, Kirsten Siebach, Soren Madsen and Ashwin Vasavada Show full author list Hide full author list

Minerals 2024, 14(6), 568; https://doi.org/10.3390/min14060568 - 29 May 2024

Cited by 6 | Viewed by 3666

Abstract

For more than a decade, the CheMin X-ray diffraction instrument on the Mars Science Laboratory rover, Curiosity, has been returning definitive and quantitative mineralogical and mineral–chemistry data from ~3.5-billion-year-old (Ga) sediments in Gale crater, Mars. To date, 40 drilled rock samples and [...] Read more.

For more than a decade, the CheMin X-ray diffraction instrument on the Mars Science Laboratory rover, Curiosity, has been returning definitive and quantitative mineralogical and mineral–chemistry data from ~3.5-billion-year-old (Ga) sediments in Gale crater, Mars. To date, 40 drilled rock samples and three scooped soil samples have been analyzed during the rover’s 30+ km transit. These samples document the mineralogy of over 800 m of flat-lying fluvial, lacustrine, and aeolian sedimentary rocks that comprise the lower strata of the central mound of Gale crater (Aeolis Mons, informally known as Mt. Sharp) and the surrounding plains (Aeolis Palus, informally known as the Bradbury Rise). The principal mineralogy of the sedimentary rocks is of basaltic composition, with evidence of post-depositional diagenetic overprinting. The rocks in many cases preserve much of their primary mineralogy and sedimentary features, suggesting that they were never strongly heated or deformed. Using aeolian soil composition as a proxy for the composition of the deposited and lithified sediment, it appears that, in many cases, the diagenetic changes observed are principally isochemical. Exceptions to this trend include secondary nodules, calcium sulfate veining, and rare Si-rich alteration halos. A surprising and yet poorly understood observation is that nearly all of the ~3.5 Ga sedimentary rocks analyzed to date contain 15–70 wt.% of X-ray amorphous material. Overall, this >800 m section of sedimentary rock explored in lower Mt. Sharp documents a perennial shallow lake environment grading upward into alternating lacustrine/fluvial and aeolian environments, many of which would have been habitable to microbial life. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Mars: Everything You Need to Know about the Red Planet)

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25 pages, 6966 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Further on the Choice of Space Group for Scapolite Group Members and Genetic Considerations about the Si-Al Ordering in Their Framework Construction

by Vladislav Kostov-Kytin, Milen Kadiyski and Rositsa Nikolova

Minerals 2024, 14(6), 556; https://doi.org/10.3390/min14060556 - 28 May 2024

Cited by 2 | Viewed by 1548

Abstract

This paper poses a major question regarding the choice of space group for scapolite mineral group members. An artificial boundary is typically drawn between space groups I4/m and P4₂/n when solving the structures of scapolites within the [...] Read more.

This paper poses a major question regarding the choice of space group for scapolite mineral group members. An artificial boundary is typically drawn between space groups I4/m and P4₂/n when solving the structures of scapolites within the marialite–meionite series. The authors debate if solving the crystal structure in lower symmetries is justified. The choice of space group here is attributed to Si-Al ordering of the framework, and it is shown that the interstitial framework cations and anions have an accompanying role in that decision. Some answers on the ranges and limits of distribution of space groups of scapolite members in the marialite–meionite series, and the manifestations of violation of the Lowenstein rule or the so-called aluminum avoidance rule are presented. Modern physical methods (SEM-EDS and SXDA) are employed in the study to properly analyze the solid solution series in detail. New crystal–chemical data are reported for scapolite samples from different localities. An analysis was made for the types of possible Al-O-Al bonds that can occur in the structures at different Al:Si ratios and their influence on Al-Si ordering. Finally, genetic considerations about Al-Si ordering in the framework construction during the mineral formation processes are proposed. Full article

(This article belongs to the Special Issue Crystal Structure, Mineralogy, and Geochemistry of Scapolite)

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19 pages, 2575 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Recycling Feldspar Mining Waste as Buffering Agent for Acid Mine Drainage Mitigation

by Giovanni Grieco, Giuseppe Cocomazzi, Stefano Naitza, Micol Bussolesi, Matteo Luca Deidda, Elena Silvia Ferrari and Enrico Destefanis

Minerals 2024, 14(6), 552; https://doi.org/10.3390/min14060552 - 27 May 2024

Cited by 1 | Viewed by 1068

Abstract

Acid mine drainage (AMD) prevention or remediation is a major issue of the environmental management of sulfide-bearing active and abandoned mining sites, the main sources of acidic waters being wastes and tailings. The present work intends to check a circular economy approach to [...] Read more.

Acid mine drainage (AMD) prevention or remediation is a major issue of the environmental management of sulfide-bearing active and abandoned mining sites, the main sources of acidic waters being wastes and tailings. The present work intends to check a circular economy approach to such issues in the mining region of Sardinia, where environmental pollution, due to AMD, is a major concern. Tests were conducted on basic drainage-producing feldspar mining wastes that could be recycled as buffering agents of sulfide-bearing tailings. Among the sulfide-bearing abandoned mining sites investigated, Furtei epithermal gold deposit tailings are the most polluting and those that can better test the buffering agent efficacy. Buffering test results show that buffering to near-neutral conditions can be attained following steps similar to those of pure calcite buffer. The buffering potential of the recycled waste is due to both the buffer calcite content, which provides short-term buffering, enhanced by feldspar content that can provide long-term buffering. Buffered waters show a dramatic decrease in the concentration of most of the metals present in the leachate, down to conditions that meet the requirements for the discharge of industrial waters according to Italian legislation. Full article

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

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18 pages, 6244 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Relationship between the Metallogenic System of Metallic Mineral Deposits and Lithospheric Electrical Structure: Insight from Magnetotelluric Imaging

by Sheng Jin, Yue Sheng, Chenggong Liu, Wenbo Wei, Gaofeng Ye, Jianen Jing, Letian Zhang, Hao Dong, Yaotian Yin and Chengliang Xie

Minerals 2024, 14(6), 541; https://doi.org/10.3390/min14060541 - 24 May 2024

Cited by 1 | Viewed by 1749

Abstract

In development over 70 years, magnetotelluric (MT) sounding, a high-resolution technique for subsurface electrical resistivity imaging, has been widely applied in resource exploration in the Earth. The key factors of the metallogenic system of metallic mineral deposits can be closely correlated to the [...] Read more.

In development over 70 years, magnetotelluric (MT) sounding, a high-resolution technique for subsurface electrical resistivity imaging, has been widely applied in resource exploration in the Earth. The key factors of the metallogenic system of metallic mineral deposits can be closely correlated to the electrical anomalies of the lithosphere. In this paper, we review the relationship between the electrical resistivity model of the lithosphere and the metallogenic system. At the beginning, we indicate why the electrical parameters relate to the metallogenic system in all geophysical parameters. The advantage of MT sounding in sketching an electrical resistivity model of the lithosphere is subsequently discussed, and some methods of data processing, analysis and inversion are also introduced. Furthermore, we summarize how to bridge the relationship between the electrical resistivity model of the lithosphere and metallogenic system, and analyze the influence of the rheological variation estimated from conductivity in the lithosphere on mineralization. In the end, we list some typical cases of the application of MT sounding in mineral exploration, and also give some suggestions for future work. This study is aimed at providing guidance in discussing the metallogenic system using an electrical resistivity model. Full article

(This article belongs to the Special Issue Geoelectricity and Electrical Methods in Mineral Exploration)

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26 pages, 7119 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Genesis of the Sartohay Podiform Chromitite Based on Microinclusions in Chromite

by Xingying Wen and Yongfeng Zhu

Minerals 2024, 14(6), 530; https://doi.org/10.3390/min14060530 - 21 May 2024

Cited by 1 | Viewed by 1245

Abstract

Here, we present a petrographic and microanalytical study of microinclusions in chromite from podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwestern China, to investigate the parental magma evolution and chromitite genesis. These silicate inclusions comprise olivine, enstatite, diopside, amphibole, [...] Read more.

Here, we present a petrographic and microanalytical study of microinclusions in chromite from podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwestern China, to investigate the parental magma evolution and chromitite genesis. These silicate inclusions comprise olivine, enstatite, diopside, amphibole, and Na-phlogopite. Their morphological characteristics suggest that most inclusions crystallized directly from the captured melt, with a few anhydrous inclusions (olivines and pyroxenes) as solid silicates trapped during the chromite crystallization. Equilibrium pressure–temperature conditions of coexisting enstatite–diopside inclusions are 8.0–21.6 kbar, and 874–1048 °C. The high Na₂O and TiO₂ contents of hydrous minerals indicate that the parental magma of chromitites was hydrous and enriched in Mg, Na, Ca, and Ti. The calculated Al₂O₃ content and FeO/MgO ratio of the parental melts in equilibrium with chromite showed MORB affinity. However, the TiO₂ values of parental melts, TiO₂ contents of chromite, and estimated fO₂ values for chromitites (1.3–2.0 log units above the FMQ buffer) evoked parental MORB-like tholeiitic melts. The composition of olivine inclusion was determined, and it was revealed that the primary melts of the Sartohay podiform chromitites had MgO contents of ~22.7 wt %. This aligns with the observed high magnesian signature in mineral inclusions (Fo = 96–98 in olivine, Mg^# = 0.91–0.97 in diopside, and Mg^# = 0.92–0.97 in enstatite). We propose that Sartohay podiform chromitites initially formed through the mixing/mingling of primary hydrous Mg-rich melt and the evolved MORB-like melt derived from the melt–peridotite reaction in the upper mantle. In this process, the continuous crystallization of chromite captured micro-silicate mineral inclusions, finally leading to the formation of the Sartohay podiform chromitites. Full article

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

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14 pages, 3682 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Selective Recovery of Gold from E-Waste Recycling Plants’ Waste Fractions: Waste-to-Resource Transition

by Svetlana Zueva, Nicolò Maria Ippolito, Marco Passadoro, Pietro Romano, Francesco Ferella and Francesco Vegliò

Minerals 2024, 14(5), 518; https://doi.org/10.3390/min14050518 - 16 May 2024

Viewed by 3273

Abstract

Electronic waste grows globally at a rate of 5% annually, which makes electronic waste recycling (WEEE recycling) an urgent task aimed at achieving (i) environmental protection and (ii) the preservation of mineral resources through the re-introduction of strategic metals into the market. As [...] Read more.

Electronic waste grows globally at a rate of 5% annually, which makes electronic waste recycling (WEEE recycling) an urgent task aimed at achieving (i) environmental protection and (ii) the preservation of mineral resources through the re-introduction of strategic metals into the market. As it turns out, WEEE recycling produces further waste, called WEEE secondary waste, which still contains valuable metals such as gold, silver, and copper. This study assessed the economic viability of recovering these metals and identified the most promising targets and approaches. WEEE secondary waste produced at a plant in southern Europe was sampled and examined for this purpose. The study methods included an ANOVA (analysis of variance) and an OCCP (orthogonal central composition plan). Over 90% gold, silver, and copper extraction was achieved with hydrochloric acid leaching in sodium hypochlorite with sodium chlorite as an oxidizing agent at 60 °C. The significance of the variation in the response for each factor, calculated using the Yates algorithm, demonstrates that by excluding sodium chloride and optimizing the doses of hydrochloric acid and sodium hypochlorite, gold can be selectively recovered through the leaching process. The scenario of HCl (2.5M)/NaClO (5%) leaching results in the maximum extraction effect of Au (91.6%) at the lowest concentrations of Ag and Cu (37–44%). Full article

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

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16 pages, 3817 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Preparation and Properties of Expansive Backfill Material Based on Municipal Solid Waste Incineration Fly Ash and Coal Gangue

by Zhen Wang, Honglin Liu, Yuanxin Zhang, Zhiwen Chen, Rumeng Zhao, Yongyong Jia, Mingchao Yong and Guodong Li

Minerals 2024, 14(5), 513; https://doi.org/10.3390/min14050513 - 14 May 2024

Cited by 1 | Viewed by 1376

Abstract

To realize the large-scale utilization of municipal solid waste incineration (MSWI) fly ash in the field of building materials and to reduce the cost of coal mine backfill mining, the effects of the mixing ratio of cementitious materials, the particle size distribution of [...] Read more.

To realize the large-scale utilization of municipal solid waste incineration (MSWI) fly ash in the field of building materials and to reduce the cost of coal mine backfill mining, the effects of the mixing ratio of cementitious materials, the particle size distribution of aggregates, and the amount and mass concentration of cementitious materials on the properties of backfill materials were experimentally investigated, and the microstructure of the hydration products was analyzed. The results showed that as the mass ratio of MSWI fly ash to bottom ash increased, the rate of expansion of the cementitious system continued to increase, and the compressive strength of the cementitious system continued to decrease. The Al (aluminum) and AlN (aluminum nitride) in the fly ash reacted with water to generate gas, causing the expansion of the cementitious materials; NaOH increased the alkalinity of the solution, which promoted the formation of more bubbles, thereby improving the expansion performance of the cementitious material. When the content of NaOH was 0.9%, the sample rate of expansion could reach 15.9%. The addition of CaCl₂ promoted the early hydration reaction of the cementitious material, forming a dense microstructure, thus improving the early strength and rate of expansion of the cementitious material. The compressive strength of the backfill body increased as the fractal dimension of the aggregate particles increased, and the particle grading scheme of group S1 was optimal. The 1-day, 3-day, and 28-day strengths of the backfill body of group S1 reached 0.72 MPa, 1.43 MPa, and 3.26 MPa, respectively. It is recommended to choose a backfill paste concentration ranging between 78.5% and 80% and a reasonable amount of cementitious material between 20% and 25%. After the MSWI fly ash was prepared as a backfill material, the leaching of potentially harmful elements in the fly ash was greatly reduced, and the concentration of dioxin was reduced to 13 ng TEQ/kg. This was attributed to the dilution of the cement, the physical encapsulation of gel products, and the isomorphous replacement of Ca²⁺ in calcium aluminate chloride hydrate. Full article

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

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15 pages, 7670 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Controls on Soft Tissue and Cellular Preservation in Late Eocene and Oligocene Vertebrate Fossils from the White River and Arikaree Groups of Nebraska, South Dakota, and Wyoming

by John E. Gallucci, Grace Woolslayer, Kelsey Barker, Brian Kibelstis, Allison R. Tumarkin-Deratzian, Paul V. Ullmann, David E. Grandstaff and Dennis O. Terry, Jr.

Minerals 2024, 14(5), 497; https://doi.org/10.3390/min14050497 - 8 May 2024

Viewed by 2509

Abstract

Previous studies on microtaphonomy have identified multiple types of organic microstructures in fossil vertebrates from a variety of time periods and past environmental settings. This study investigates potential taphonomic, paleoenvironmental, and paleoclimatic controls on soft tissue and cellular preservation in fossil bone. To [...] Read more.

Previous studies on microtaphonomy have identified multiple types of organic microstructures in fossil vertebrates from a variety of time periods and past environmental settings. This study investigates potential taphonomic, paleoenvironmental, and paleoclimatic controls on soft tissue and cellular preservation in fossil bone. To this end, fifteen vertebrate fossils were studied: eight fossils collected from the Oligocene Sharps Formation of the Arikaree Group in Badlands National Park, South Dakota, and seven fossils from formations in the underlying White River Group, including the Oligocene Brule Formation of Badlands National Park, and the Eocene Chadron Formation of Flagstaff Rim, Wyoming; Toadstool Geologic Park, Nebraska; and Badlands National Park, South Dakota. A portion of each fossil was demineralized to identify any organic microstructures preserved within the fossils. We investigated several factors which may have influenced cellular/soft tissue decay and/or preservation pathways, including taxonomic identity, paleoclimatic conditions, depositional environment, and general diagenetic history (as interpreted through thin section analysis). Soft tissue microstructures were preserved in all fossil samples, and cellular structures morphologically consistent with osteocytes were recovered from 11 of the 15 fossil specimens. Preservation of these microstructures was found to be independent of taxonomy, paleoclimate regime, apatite crystallinity, depositional environment, and general diagenetic history, indicating that biogeochemical reactions operating within microenvironments within skeletal tissues, such as within individual osteocyte lacunae or Haversian canals, may exert stronger controls on soft tissue and biomolecular decay or stabilization than external environmental (or climatic) conditions. Full article

(This article belongs to the Special Issue Recent Advances in Bone Diagenesis)

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20 pages, 2798 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Are Clay Minerals Systematically the Products of Aqueous Alteration in Cosmic Bodies?

by Abderrazak El Albani, Ibtissam Chraiki, Hasnaa Chennaoui Aoudjehane, Mohamed Ghnahalla, Fatima Abdelfadel, Ahmed Abd Elmola, Olabode Bankole, Julie Ngwal’ghoubou Ikouanga, Anna El Khoury, Claude Fontaine, El Hafid Bouougri, France Westall and Alain Meunier

Minerals 2024, 14(5), 486; https://doi.org/10.3390/min14050486 - 3 May 2024

Viewed by 1979

Abstract

The formation of chondrite materials represents one of the earliest mineralogical processes in the solar system. Phyllosilicates are encountered at various stages of the chondrule formation, from the initial stages (IDP agglomerates) to the final steps (chondrule internal alteration). While typically linked to [...] Read more.

The formation of chondrite materials represents one of the earliest mineralogical processes in the solar system. Phyllosilicates are encountered at various stages of the chondrule formation, from the initial stages (IDP agglomerates) to the final steps (chondrule internal alteration). While typically linked to aqueous alteration, recent studies reveal that phyllosilicates could precipitate directly from residual fluids in post-magmatic or deuteric conditions and under a wide range of temperatures, pressures, water/rock ratios, and H₂/H₂O ratio conditions. This study re-examined the formation of hydrated phyllosilicates in chondrules and associated fine-grained rims (FGRs) using published petrographical, mineralogical, and chemical data on carbonaceous chondrites. Given that chondrules originate from the melting of interplanetary dust particles, the water liberated by the devolatilization of primary phyllosilicates, including clay minerals or ice melting, reduces the melting temperature and leads to water dissolution into the silicate melt. Anhydrous minerals (e.g., olivine and diopside) form first, while volatile and incompatible components are concentrated in the residual liquid, diffusing into the matrix and forming less porous FGRs. Serpentine and cronstedtite are the products of thermal metamorphic-like mineral reactions. The mesostasis in some lobated chondrules is composed of anhydrous and hydrous minerals, i.e., diopside and serpentine. The latter is probably not the alteration product of a glassy precursor but rather a symplectite component (concomitant crystallization of diopside and serpentine). If so, the symplectite has been formed at the end of the cooling process (eutectic-like petrographical features). Water trapped inside chondrule porosity can lead to the local replacement of olivine by serpentine without external water input (auto-alteration). In the absence of water, hydrated phyllosilicates do not crystallize, forming a different mineral assemblage. Full article

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

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22 pages, 15317 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A New Insight into the Genesis of Graphite Deposits in Madagascar Using U–Pb Zircon Dating and Electron Microprobe Analysis

by Ming-Jian Yang, Yong-Jun Di, Da Zhang, Da-Tian Wu, Ye Fang and Xin-Ming Zhang

Minerals 2024, 14(5), 484; https://doi.org/10.3390/min14050484 - 2 May 2024

Cited by 2 | Viewed by 2227

Abstract

Madagascar is globally recognized as an important producer of high-quality flaky graphite. However, current research on graphite deposits in Madagascar remains insufficient. Previous studies have linked the genesis of Madagascan graphite deposits to the metamorphism of sedimentary organic matter. Here, we provide a [...] Read more.

Madagascar is globally recognized as an important producer of high-quality flaky graphite. However, current research on graphite deposits in Madagascar remains insufficient. Previous studies have linked the genesis of Madagascan graphite deposits to the metamorphism of sedimentary organic matter. Here, we provide a case study of graphite deposits in Madagascar, combining new data from the Ambahita graphite deposit (AMG) in southern Madagascar with data from the Antanisoa graphite deposit (ANG) in central Madagascar and the Vohitasara graphite deposit (VOG) on the east coast of Madagascar. We note that the mineral assemblages of graphite-bearing rocks in the AMG, ANG, and VOG are not typical of metamorphic mineral assemblages but rather the results of filling and metasomatism by mantle-derived fluids that occurred after peak metamorphism. Electron microprobe analysis indicates that the graphite of the AMG, VOG, and ANG is usually associated with phlogopite or Mg-biotite; the phlogopite shares a common genesis with other widespread phlogopite deposits across Madagascar. We reveal that the distribution of graphite deposits in Madagascar is primarily controlled by ductile shear zones between blocks. Ductile shear zones that extend deep into the mantle can provide an ideal migration channel and architecture for the emplacement of mantle-derived fluids. The graphite mineralization formed no earlier than the peak metamorphism (490 Ma) and no later than the intrusion of pegmatite veins (389 ± 5 Ma). The distribution of graphite deposits, graphite orebody morphologies, mineral associations, and geochemical data suggest that the genesis of graphite deposits in Madagascar is linked to mantle-derived fluid filling rather than the metamorphism of sediments, as previously suggested. These findings have important implications for similar deposits in Madagascar and potentially globally. Full article

(This article belongs to the Special Issue Microbeam Analysis Characterization in Petrogenesis and Ore Deposit)

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17 pages, 1764 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Fractionation Columns on the Elution of Rare Earth Elements Recovered from Acid Mine Drainage

by Gabriela Cordeiro Silva, Clauson Souza, Pedro Augusto Possa Vicente Sacramento Ferreira, Liliani Pacheco Tavares Nazareth and Ana Claudia Queiroz Ladeira

Minerals 2024, 14(5), 451; https://doi.org/10.3390/min14050451 - 25 Apr 2024

Viewed by 1468

Abstract

Rare earth elements (REE) can be found in expressive contents in different secondary sources, such as acid mine drainage (AMD). This work evaluated separation of light and heavy rare earth elements (REE) from an acid mine drainage (AMD) generated in a former uranium [...] Read more.

Rare earth elements (REE) can be found in expressive contents in different secondary sources, such as acid mine drainage (AMD). This work evaluated separation of light and heavy rare earth elements (REE) from an acid mine drainage (AMD) generated in a former uranium mine in Brazil by using ion exchange. This AMD presents pH 3.50, total REE content of 97 mg L⁻¹ and 1.3 g L⁻¹ of sulfate and was used in the REE loading experiments. Loading experiments were carried out in columns using a commercial strong acid cation (SAC) exchange resin. Elution was performed with 0.01 mol L⁻¹ NH₄EDTA in systems with one, two and three columns. Regarding the loading step, the resin presented a total loading capacity of 0.58 mmol g⁻¹. The resin proved to be more selective for light REE with adsorption efficiency of 78% and 48% for heavy REE. Regarding elution, high efficiencies between 90 and 100% were achieved for REE. The final REE solution is approximately 10 times more concentrated in the liquor related to the acid mine water. Better fractionation results were achieved for the system with three columns. Although the complete separation of the REE into pure elements was not possible, two distinct fractions of heavy and light REE could be obtained, and La was completely separated from the other REE. In order to improve fractionation and separate the REE into individual ones, the concentrated fractions can proceed to subsequent ion exchange systems. Full article

(This article belongs to the Special Issue Characterization and Management of Mine Waters)

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34 pages, 9922 KiB

Open AccessFeature PaperEditor’s ChoiceSystematic Review

Sensor Technologies for Safety Monitoring in Mine Tailings Storage Facilities: Solutions in the Industry 4.0 Era

by Carlos Cacciuttolo, Valentina Guzmán, Patricio Catriñir and Edison Atencio

Minerals 2024, 14(5), 446; https://doi.org/10.3390/min14050446 - 24 Apr 2024

Cited by 6 | Viewed by 5525

Abstract

The recent tailings storage facility (TSF) dam failures recorded around the world have concerned society in general, forcing the mining industry to improve its operating standards, invest greater economic resources, and implement the best available technologies (BATs) to control TSFs for safety purposes [...] Read more.

The recent tailings storage facility (TSF) dam failures recorded around the world have concerned society in general, forcing the mining industry to improve its operating standards, invest greater economic resources, and implement the best available technologies (BATs) to control TSFs for safety purposes and avoid spills, accidents, and collapses. In this context, and as the era of digitalization and Industry 4.0 continues, monitoring technologies based on sensors have become increasingly common in the mining industry. This article studies the state of the art of implementing sensor technologies to monitor structural health and safety management issues in TSFs, highlighting advances and experiences through a review of the scientific literature on the topic. The methodology applied in this article adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and utilizes scientific maps for data visualization. To do so, three steps were implemented: (i) a quantitative bibliometric analysis, (ii) a qualitative systematic review of the literature, and (iii) a mixed review to integrate the findings from (i) and (ii). As a result, this article presents the main advances, gaps, and future trends regarding the main characteristics of the sensor technologies applied to monitor TSF structural health and safety management in the era of digitalization. According to the results, the existing research predominantly investigates certain TSF sensor technologies, such as wireless real-time monitoring, remote sensors (RS), unmanned aerial vehicles (UAVs), unmanned survey vessels (USVs), artificial intelligence (AI), cloud computing (CC), and Internet of Things (IoT) approaches, among others. These technologies stand out for their potential to improve the safety management monitoring of mine tailings, which is particularly significant in the context of climate change-related hazards, and to reduce the risk of TSF failures. They are recognized as emerging smart mining solutions with reliable, simple, scalable, secure, and competitive characteristics. Full article

(This article belongs to the Special Issue Tailings Dams: Design, Characterization, Monitoring, and Risk Assessment, 2nd Edition)

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18 pages, 3115 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Influences of O₂ Availability on the Microbial Activities and Fe Transformations in the Iron Formation Caves of the Southern Espinhaço Range, Brazil

by Melissa K. Mulford, Anela Mukherjee, Augusto S. Auler, Hazel A. Barton and John M. Senko

Minerals 2024, 14(4), 425; https://doi.org/10.3390/min14040425 - 20 Apr 2024

Viewed by 1481

Abstract

Over 3000 iron formation caves (IFCs) have formed in erosion-resistant Fe(III)-rich rocks throughout Brazil. Microbial Fe(III) reduction occurs in IFCs, where a microbe-rich, Fe(III)-depleted paste (sub muros) is found behind an Fe(III)-(hydr)oxide crust in the ceiling/walls. Microbial Fe(III) reduction in sub [...] Read more.

Over 3000 iron formation caves (IFCs) have formed in erosion-resistant Fe(III)-rich rocks throughout Brazil. Microbial Fe(III) reduction occurs in IFCs, where a microbe-rich, Fe(III)-depleted paste (sub muros) is found behind an Fe(III)-(hydr)oxide crust in the ceiling/walls. Microbial Fe(III) reduction in sub muros appears to be responsible for the transformation of Fe(III) to more soluble Fe(II), which is removed, leading to cave formation. This process of biospeleogenesis is likely controlled by O₂ availability, which is linked to seasonal changes. Here, we studied the effects of alternating anoxia/oxia on the microbial community and on Fe solubility in banded iron formation (BIF), a rock type consisting of layered Fe(III)-oxide and silicate. Incubations of synthetic pore water, pulverized BIF, and sub muros were prepared and incubated under anoxia, during which BIF-Fe(III) reduction proceeded. During the Fe(III) reduction period, Firmicutes and/or Alphaproteobacteria were enriched, and genes involved in Fe(III) and sulfate reduction were detected in the metagenomes. Fe(II) oxidation genes, which were detected in the fresh sub muros, were not found. Upon the addition of atmospheric O₂, Fe(III) reduction was arrested, and incomplete Fe(II) oxidation occurred. Betaproteobacteria, Gammaproteobacteria, and Chloroflexi increased in relative abundance following aeration, and Fe(III) reduction genes were still identified. Our results demonstrate that the sub muros microbial community retains the ability to reduce Fe(III) and drive speleogenesis despite fluctuations in O₂ levels. Full article

(This article belongs to the Section Biomineralization and Biominerals)

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17 pages, 3673 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Application of Stacking Ensemble Learning in Predicting Copper’s Flotation Concentrate Grade

by Chengzhe Yin and Leming Ou

Minerals 2024, 14(4), 424; https://doi.org/10.3390/min14040424 - 19 Apr 2024

Cited by 1 | Viewed by 1205

Abstract

Addressing issues such as a low operational condition recognition efficiency, strong subjectivity, and significant fluctuations in Outotec X fluorescence analysis data in copper flotation production, a copper concentrate grade classification model is constructed based on image processing technology and the Stacking ensemble learning [...] Read more.

Addressing issues such as a low operational condition recognition efficiency, strong subjectivity, and significant fluctuations in Outotec X fluorescence analysis data in copper flotation production, a copper concentrate grade classification model is constructed based on image processing technology and the Stacking ensemble learning algorithm. Firstly, a feature extraction model for copper concentration flotation foam images is established, extracting color, texture, and size statistical features to build a feature dataset. Secondly, to avoid redundancy in the feature data, which could reduce model accuracy, a combined correlation feature selection is employed for dimensionality reduction, with the filtered feature subset being used as the model input. Finally, to fully leverage the strengths of each model, a Stacking ensemble learning copper concentrate grade classification model is constructed with support vector machine (SVM), random forest (RF), and adaptive boosting (AdaBoost) as base models and logistic regression (LR) as the meta-model. The experimental results show that this ensemble model achieves good recognition for different grade categories, with a precision, recall, and F1 score of 90.01%, 89.85%, and 89.93%, respectively. The accuracy of this Stacking ensemble model, with a 7% improvement over Outotec X fluorescence analysis, demonstrates a potential to meet the daily production needs of beneficiation plants. Full article

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

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19 pages, 39343 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Conditions and Mechanism of Crystallization of Hydrous W-Fe Oxides with a Pyrochlore-Type of Structure (Elsmoreite Group) in the Oxidation Zone of Ore Deposits

by Mihail Tarassov and Eugenia Tarassova

Minerals 2024, 14(4), 422; https://doi.org/10.3390/min14040422 - 19 Apr 2024

Cited by 1 | Viewed by 1667

Abstract

The purpose of the article is to elucidate the conditions and mechanism of crystallization of W-Fe oxide minerals with a pyrochlore-type structure (formerly ferritungstite, now elsmoreite group minerals) based on (1) a study of representative samples of secondary tungsten minerals from the oxidation [...] Read more.

The purpose of the article is to elucidate the conditions and mechanism of crystallization of W-Fe oxide minerals with a pyrochlore-type structure (formerly ferritungstite, now elsmoreite group minerals) based on (1) a study of representative samples of secondary tungsten minerals from the oxidation zone of the Grantcharitsa tungsten deposit (Bulgaria) and (2) laboratory experiments under conditions suggested by the study of natural samples. It has been shown that crystallization of W-Fe pyrochlores occurs easily and effectively when treating WO₃·xFe₂O₃·nH₂O compounds (meymacite and tungstite) with W-Fe-containing solutions with pH 2.5–6.5 (70 °C); at the same time, direct crystallization (direct low-temperature hydrothermal synthesis) of these phases from aqueous solutions is unlikely. The crystallization of W-Fe pyrochlores under natural and laboratory conditions occurs through the oriented attachment of their nanocrystals to the {111} faces of growing crystals. The nucleation of such nanocrystals occurs in the bulk of the solution as a result of the interaction of the W-Fe solution with the W-(Fe) oxide hydrate precursor. The Fe/W ratio in the resulting W-Fe pyrochlore phase depends on the Fe/W ratio in the solution and precursor, as well as on the pH of the solution. Full article

(This article belongs to the Special Issue Mineral Evolution and Mineralization during Weathering)

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15 pages, 1713 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Stability of CO₂ Fluid in Eclogitic Mantle Lithosphere: Thermodynamic Calculations

by Yulia G. Vinogradova and Anton Shatskiy

Minerals 2024, 14(4), 403; https://doi.org/10.3390/min14040403 - 15 Apr 2024

Viewed by 1243

Abstract

Findings of solid and liquefied CO₂ in diamonds from kimberlites and placers have indicated its presence in the form of a fluid phase in the Earth’s mantle at depths of 150–250 km. However, this is inconsistent with the results of experiments and [...] Read more.

Findings of solid and liquefied CO₂ in diamonds from kimberlites and placers have indicated its presence in the form of a fluid phase in the Earth’s mantle at depths of 150–250 km. However, this is inconsistent with the results of experiments and existing thermodynamic calculations. To clarify this, we carried out thermodynamic modeling of garnet–CO₂ and bimineral eclogite–CO₂ systems using the Perple_X v. 7.1.3 software package, which establishes the most thermodynamically favorable assemblages for a given bulk composition of the system, unlike previous calculations, for which the phase relationships were simply assumed. The key difference between our results and previously known data is the presence of a region of partial carbonation. In this region, the garnet and clinopyroxene of the new compositions, CO₂ fluid, carbonates, kyanite, and coesite are in equilibrium. The calculations revealed that unlike endmember systems (pyrope–CO₂ and diopside–CO₂) in the eclogite–CO₂ system, the carbonation and decarbonation lines do not coincide, and the Grt+Cpx+CO₂ and Carb+Ky+Coe+Cpx fields are separated by the Grt+Cpx+CO₂+Carb+Ky+Coe region, which extends to pressures exceeding 4.3–6.0 GPa at 1050–1200 °C. This should extend the CO₂ stability field in the eclogitic mantle to lower temperatures. Yet, owing to the short CO₂ supply in the real mantle, the CO₂ fluid should be completely spent on the carbonation of eclogite just below the eclogite + CO₂ field. Thus, according to the obtained results, the CO₂ fluid is stable in the eclogitic mantle in the diamond stability field at temperatures exceeding 1250 °C and pressures of 5–6 GPa. Full article

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

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21 pages, 3280 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Rare-Earth Element Phase Associations in Four West Virginia Coal Samples

by Rachel Yesenchak, Shikha Sharma, Christina Lopano and Scott Montross

Minerals 2024, 14(4), 362; https://doi.org/10.3390/min14040362 - 29 Mar 2024

Cited by 2 | Viewed by 1934

Abstract

Rare-earth elements are critical components of technologies used in renewable energy, communication, transportation, and national defense. Securing supply chains by developing domestic rare-earth resources, including coal and coal byproducts, has become a national priority. With some of the largest coal reserves in the [...] Read more.

Rare-earth elements are critical components of technologies used in renewable energy, communication, transportation, and national defense. Securing supply chains by developing domestic rare-earth resources, including coal and coal byproducts, has become a national priority. With some of the largest coal reserves in the country, states within the Appalachian Basin can play a key role in supplying these elements. Understanding rare-earth element phase associations and the processes that lead to enrichment in these coals will inform resource prospecting and recovery techniques. This study used sequential leaching in addition to scanning electron microscopy and energy-dispersive X-ray spectroscopy to identify rare-earth element modes of occurrence in WV coals. The results indicate that heavier elements have a stronger association with organic matter and that phosphate minerals are primary sources of both heavy and light rare-earth elements. However, these phases are shielded by a resistant aluminosilicate matrix that can impede the recovery of rare-earth elements using traditional methods. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: "Critical and Strategic Minerals")

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48 pages, 8568 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Global Occurrence, Geology and Characteristics of Hydrothermal-Origin Kaolin Deposits

by Ömer Işık Ece and Hatice Ünal Ercan

Minerals 2024, 14(4), 353; https://doi.org/10.3390/min14040353 - 28 Mar 2024

Cited by 4 | Viewed by 4403

Abstract

Kaolin-group minerals occur in nature as the result of high-sulfidation acid sulfate, sulfur-poor HCl-, HF- and H₂CO₃-rich acidic fluid-related hydrothermal alterations and in situ geochemical weathering. These minerals possess different crystallographic and chemical properties that determine their application areas, [...] Read more.

Kaolin-group minerals occur in nature as the result of high-sulfidation acid sulfate, sulfur-poor HCl-, HF- and H₂CO₃-rich acidic fluid-related hydrothermal alterations and in situ geochemical weathering. These minerals possess different crystallographic and chemical properties that determine their application areas, mainly in the ceramic and paper industries, and as nanocomposite materials. The physicochemical properties of hydrothermal kaolin deposits are the result of the type of parent rock, the effect of the regional tectonism-associated magmatism, and the chemical features of hydrothermal fluids that interact with the deep basement rocks. However, understanding these geothermal systems is one of the most challenging issues due to the rich mineralogical assemblages, complex geochemistry and isotopic data of hydrothermal alteration zones. This study evaluates the formation of hydrothermal-origin kaolin-group minerals by considering their characteristics of hydrothermal alteration, isotopic compositions and differences in characteristic properties of low- and high-sulfidation occurrences; this paper also addresses mineralogical and structural differences between hypogene and supergene kaolin formations, and kaolin–alunite–pyrophyllite association, and it provides examples of worldwide occurrences. The study of the mineralogical assemblages, geochemistry and isotopic data of the hydrothermal alteration zones is one of the most challenging subjects in terms of gaining a detailed understanding of the geothermal systems. Silicification processes are subsequent to late-stage alteration after the completion of kaolinization processes, erasing existing hydrothermal mineralogical and geochemical traces and making interpretation difficult. In the early stages involving magmatic–hydrothermal-origin acidic geothermal fluids, the latter comes from the disproportionation of SO₂ (+H₂O) and H₂S oxidation to H₂SO₄ in hydrothermal environments. In the later stages, due to spatial and temporal changes over time in the chemistry of geothermal fluids, the system comes to have a more alkali–chloride composition, with neutral pH waters frequently saturated with amorphous silica which characteristically precipitate as siliceous sinter deposits containing large amounts of opal-A. Full article

(This article belongs to the Section Mineral Deposits)

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