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Keywords = magnetite chemistry

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42 pages, 30007 KB  
Article
Fundamental Analysis of Sinter Solid Structure: Implications of Mineral Associations for Understanding Industrial Iron Ore Sinter Formation
by John M. F. Clout, Natalie A. Ware, James R. Manuel, Nathan A. S. Webster and Mark I. Pownceby
Minerals 2026, 16(2), 129; https://doi.org/10.3390/min16020129 - 25 Jan 2026
Abstract
The solid structure of industrial sinter comprises seven mineral associations (A, B, C, D, Ds, E, N) which have different relative abundances of key minerals, textures and spatial relationships to micro-macropores and hematite nuclei. Among the key characteristics of the mineral associations: (MA), [...] Read more.
The solid structure of industrial sinter comprises seven mineral associations (A, B, C, D, Ds, E, N) which have different relative abundances of key minerals, textures and spatial relationships to micro-macropores and hematite nuclei. Among the key characteristics of the mineral associations: (MA), MA-A comprises abundant SFCA-I microplates with hematite; MA-B consists of disseminated fine-grained magnetite in a network of SFCA-III microplates; MA-C is similar to MA-B but contains patches of dendritic SFCA-III with larnite and minor glass; MA-D comprises magnetite surrounded by coarse prisms of SFCA within glass; MA-Ds, a subtype of MA-D, includes SFCA with secondary skeletal hematite; MA-E consists of anhedral to skeletal magnetite or hematite in a matrix of glass; and MA-N comprises unmelted hematite nuclei from iron ore feedstock. SFCA-III and SFCA-I are dominant in MA-B and MA-A, respectively, whilst magnetite is the most common mineral in MA-C, MA-D/Ds and MA-E. Low-temperature sintering samples are largely of MA-A to MA-D (62 area %), which contain higher combined levels of SFCA-SFCA-III and lower levels of magnetite-dominant MA-E (12.6 area %), whereas high-temperature/magnetite sintering examples had high levels of magnetite-dominant MA-E (31.6 area %) and MA-D/Ds (52.1 area %) and low levels of MA-A to MA-C (8.9 area %). It is proposed that the formation of each MA is controlled by the peak sintering temperature attained, the dwell time at higher temperature which adversely allows fractional crystallisation to tie up more Fe in magnetite rather than forming SFCA phases during cooling, and especially a slower rate of cooling which promotes the formation of more SFCA family phases at lower temperatures. However, local variations in chemistry inherited from raw material granulation and assimilation during sintering of Si-rich gangue or ore nuclei are also important. Full article
(This article belongs to the Special Issue Mineralogy of Iron Ore Sinters, 3rd Edition)
23 pages, 27668 KB  
Article
Magmatic to Subsolidus Evolution of the Variscan Kastoria Pluton (NW Greece): Constraints from Mineral Chemistry and Textures
by Ioanna Gerontidou, Antonios Koroneos, Lambrini Papadopoulou, Alexandros Chatzipetros, Matteo Masotta and Stefanos Karampelas
Minerals 2026, 16(1), 83; https://doi.org/10.3390/min16010083 - 15 Jan 2026
Viewed by 159
Abstract
This study focuses on the mineralogy and mineral chemistry of the accessory minerals occurring in the Kastoria pluton situated in NW Greece, which intrudes the Pelagonian nappe having crystallized during the Late Paleozoic (~300 Ma). The pluton consists of porphyritic granite (GR) that [...] Read more.
This study focuses on the mineralogy and mineral chemistry of the accessory minerals occurring in the Kastoria pluton situated in NW Greece, which intrudes the Pelagonian nappe having crystallized during the Late Paleozoic (~300 Ma). The pluton consists of porphyritic granite (GR) that hosts mafic microgranular enclaves (MME) of monzonitic composition. Both lithologies contain quartz, microcline, plagioclase, biotite, secondary white mica, hornblende, and actinolite along with accessory minerals including titanite, epidote, allanite, apatite, zircon, and magnetite. Compared to the granite, the enclaves are richer in biotite, amphibole, and plagioclase but poorer in quartz and microcline. Mineral chemistry indicates a calc–alkaline affinity, consistent with the observed magmatic trends. Crystallization pressure, estimated at 3 kbar from Al in a hornblende barometer, suggests emplacement at mid-crustal levels. During the Alpine deformation, the pluton underwent low-grade greenschist to amphibolite-facies metamorphism, which partially overprinted the primary mineral assemblages. Magmatic titanite and allanite crystals are well preserved, showing only recrystallization features. Metamorphism produced tiny titanite needles and epidote replacing primary minerals (plagioclase, amphibole, and biotite). Later, hydrothermal alteration produced another generation of secondary epidote. Only a couple of epidote crystals preserve potential magmatic relict characteristics (euhedral habit, zircon inclusions, positive Eu anomaly, and sharp contact with primary minerals). These results provide insights into both the primary magmatic features and the subsequent metamorphic modification of the I-type Kastoria pluton within the Pelagonian domain. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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18 pages, 999 KB  
Article
Direct Liquid Phase Hydroxylation of Benzene to Phenol over Iron-Containing Mordenite Catalysts: Combined DLS–EPR Study and Thermodynamic–Stability Analysis
by E. H. Ismailov, L. Kh. Qasimova, S. N. Osmanova, A. I. Rustamova, L. V. Huseynova, S. A. Mammadkhanova and Sh. F. Tagiyeva
Catalysts 2026, 16(1), 89; https://doi.org/10.3390/catal16010089 - 13 Jan 2026
Viewed by 360
Abstract
Direct hydroxylation of benzene to phenol using hydrogen peroxide is a cornerstone of sustainable green chemistry. This paper presents the results of a stability study of an iron-containing mordenite catalyst in the liquid-phase hydroxylation of benzene to phenol with a 30% aqueous hydrogen [...] Read more.
Direct hydroxylation of benzene to phenol using hydrogen peroxide is a cornerstone of sustainable green chemistry. This paper presents the results of a stability study of an iron-containing mordenite catalyst in the liquid-phase hydroxylation of benzene to phenol with a 30% aqueous hydrogen peroxide solution. The study utilizes a combination of catalytic activity measurements, dynamic light scattering (DLS), and electron paramagnetic resonance (EPR) spectra. The system is initially shown to exhibit high phenol selectivity; however, over time, DLS measurements indicate aggregation of the catalyst particles with an increase in the average particle diameter from 1.8 to 2.6 μm and the formation of byproducts–dihydroxybenzenes. Iron is present predominantly as magnetite nanoparticles (Fe3O4) ~10 nm in diameter, stabilized on the outer surface of mordenite, with minor leaching (<10%) due to the formation of iron ion complexes with ascorbic acid as a result of the latter’s interaction with magnetite particles. Using a thermodynamic approach based on the Ulich formalism (first and second approximations), it is shown that the reaction of benzene hydroxylation H2O2 in the liquid phase is thermodynamically quite favorable (ΔG° = −(289–292) kJ·mol−1 in the range of 293–343 K, K = 1044–1052). It is shown that ascorbic acid acts as a redox mediator (reducing Fe3+ to Fe2+) and a regulator of the catalytic medium activity. The stability of the catalytic system is examined in terms of the Lyapunov criterion: it is shown that the total Gibbs free energy (including the surface contribution) can be considered as a Lyapunov functional describing the evolution of the system toward a steady state. Ultrasonic (US) treatment of the catalytic system is shown to redisperse aggregated particles and restore its activity. It is established that the catalytic activity is due to nanosized Fe3O4 particles, which react with H2O2 to form hydroxyl radicals responsible for the selective hydroxylation of benzene to phenol. Full article
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31 pages, 22151 KB  
Article
Calcium-Enriched Magnetic Core–Shell Mesoporous Nanoparticles for Potential Application in Bone Regeneration
by Despoina Kordonidou, Georgia K. Pouroutzidou, Nikoletta Florini, Ioannis Tsamesidis, Konstantina Kazeli, Dimitrios Gkiliopoulos, George Vourlias, Makis Angelakeris, Philomela Komninou, Panos Patsalas and Eleana Kontonasaki
Nanomaterials 2025, 15(24), 1904; https://doi.org/10.3390/nano15241904 - 18 Dec 2025
Viewed by 614
Abstract
Magnetite (Fe3O4) nanoparticles are biocompatible, non-toxic, and easily functionalized. Coating them with mesoporous silica (mSiO2) offers high surface area, pore volume, and tunable surface chemistry for drug loading. In this study, Fe3O4 magnetic nanoparticles [...] Read more.
Magnetite (Fe3O4) nanoparticles are biocompatible, non-toxic, and easily functionalized. Coating them with mesoporous silica (mSiO2) offers high surface area, pore volume, and tunable surface chemistry for drug loading. In this study, Fe3O4 magnetic nanoparticles were synthesized and coated with mSiO2 shells enriched with calcium ions (Ca2+), aiming to enhance bioactivity for bone regeneration and tissue engineering. Different synthesis routes were tested to optimize shell formation Their characterization confirmed the presence of a crystalline Fe3O4 core with partial conversion to maghemite (Fe2O3) post-coating. The silica shell was mostly amorphous and the optimized samples exhibited mesoporous structure (type IVb). Calcium incorporation slightly altered the magnetic properties without significantly affecting core crystallinity or particle size (11.68–13.56 nm). VSM analysis displayed symmetric hysteresis loops and decreased saturation magnetization after coating and Ca2+ addition. TEM showed spherical morphology with some agglomeration. MTT assays confirmed overall non-toxicity, except for mild cytotoxicity at high concentrations in the Ca2+-enriched sample synthesized by a modified Stöber method. Their capacity to induce human periodontal ligament cell osteogenic differentiation, further supports the potential of Fe3O4/mSiO2/Ca2+ core–shell nanoparticles as promising candidates for bone-related biomedical applications due to their favorable magnetic, structural, and biological properties. Full article
(This article belongs to the Section Nanocomposite Materials)
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17 pages, 7865 KB  
Article
Garnet Geochemistry of the Makeng-Yangshan Fe Skarn Belt, Southeast China: Implications for Contrasting Hydrothermal Systems and Metal Endowment
by Wanyi Feng, Shuting Lei, Bo Xing, Jing Xu and Haibo Yan
Minerals 2025, 15(12), 1325; https://doi.org/10.3390/min15121325 - 18 Dec 2025
Viewed by 362
Abstract
The Southwestern Fujian Region is one of the important Fe polymetallic metallogenic belts in China. The Makeng-Yangshan Fe skarn sub-belt within it contains several deposits that share a similar geological setting, mineralization age, and genetic type, yet exhibit significant differences in metal endowment. [...] Read more.
The Southwestern Fujian Region is one of the important Fe polymetallic metallogenic belts in China. The Makeng-Yangshan Fe skarn sub-belt within it contains several deposits that share a similar geological setting, mineralization age, and genetic type, yet exhibit significant differences in metal endowment. To investigate the poorly constrained factors responsible for these differences, this paper focused on the mineral chemistry of garnets associated with magnetite from the Makeng, Luoyang, and Yangshan Fe deposits within the sub-belt, employing in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for trace element analysis. Our results reveal that garnet from all three deposits are andradite-dominated and features a chondrite-normalized REE fractionation pattern exhibiting enrichment in LREE relative to HREE, indicating crystallization from unified, mildly acidic fluids under high oxygen fugacity (fO2) conditions. However, both the Makeng and Luoyang garnets showed a strong positive Eu anomaly, whereas the Yangshan garnets displayed the weakest Eu anomaly among the three deposits, which can likely be attributed to the highest fO2 environment of the Yangshan deposit. Furthermore, garnet Y/Ho ratios and Y-ΣREE correlations demonstrate that the Makeng and Luoyang garnets crystallized in an open fluid system that were primarily of magmatic-hydrothermal origin with substantial external fluid (e.g., meteoric water) involvement, whereas the Yangshan garnet reflects a relatively closed fluid system that was predominantly of magmatic-hydrothermal origin with limited external fluid input. These geochemical differences have direct implications for exploration: the open-system Makeng deposit holds promise for Mo-W-Sn mineralization, as does the Luoyang deposit for W-Sn, whereas the closed-system Yangshan shows little potential for these metals. In addition, this study reveals that Pb and Zn concentrations in garnet are not reliable exploration indicators. Overall, these findings provide important mineralogical constraints on the factors controlling deposit scale and metal associations, thereby enhancing the understanding of regional metallogeny and guiding future mineral exploration. Full article
(This article belongs to the Special Issue Mineralization and Metallogeny of Iron Deposits)
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17 pages, 4535 KB  
Article
Petrophysical Characterisation and Suitability of Serpentinites from the Monteferrato Area (Tuscany, Italy) for Architectural Restoration
by Alba P. Santo, Carlo Alberto Garzonio, Elena Pecchioni and Teresa Salvatici
Minerals 2025, 15(11), 1105; https://doi.org/10.3390/min15111105 - 23 Oct 2025
Viewed by 472
Abstract
This study investigates the mineralogical and physical properties of serpentinite from the Monteferrato area (Tuscany, Italy) to evaluate its potential use in Tuscany architectural restoration. The research addresses the need to identify replacement materials compatible with historic stones while preserving their original features. [...] Read more.
This study investigates the mineralogical and physical properties of serpentinite from the Monteferrato area (Tuscany, Italy) to evaluate its potential use in Tuscany architectural restoration. The research addresses the need to identify replacement materials compatible with historic stones while preserving their original features. Representative specimens from the Bagnolo quarry were analysed through physical testing and a wide range of mineralogical and geochemical techniques, including polarised light microscopy, X-ray diffraction, electron probe micro-analysis, whole-rock chemistry, and fibre quantification. The results show a mineralogical composition dominated by serpentine-group minerals and magnetite, with physical properties generally consistent across samples. Measured capillary water absorption ranges from 3.27 to 5.27 g/m2·s0.5, open porosity from 5.25% to 8.93%, apparent densities range from 2.49 to 2.56 g/cm3, and imbibition coefficient from 2.16% to 3.71%. Comparative analysis with serpentinite from historic sources (Figline di Prato quarry, Tuscany) and from monuments (Baptistery of San Giovanni, Florence) demonstrates close compositional and textural affinities, supporting the suitability of the rock from the studied quarry for restoration purposes in Tuscany monuments. However, chrysotile concentrations up to 14,153 mg/kg, exceeding Italian regulatory thresholds, represent a critical limitation. This not only requires the implementation of strict safety measures but also raises serious concerns regarding the practical feasibility of using this stone in conservation projects. More broadly, the presence of asbestiform minerals in serpentinites highlights a significant and often underestimated health risk associated with their extraction, processing, and use. Despite its importance, detailed fibre count data are rarely published or made publicly accessible, hindering both transparent risk assessment and informed decision-making. By integrating petrographic, mineralogical, and physical–mechanical characterisation with fibre quantification, this study not only assesses the technical suitability of Monteferrato serpentinites for restoration of Tuscan monuments but also contributes to a more responsible and evidence-based approach to their use, emphasising the urgent need for transparency and health protection in conservation practices. Full article
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33 pages, 77489 KB  
Article
Chemistry and Fe Isotopes of Magnetites in the Orbicular Bodies in the Tanling Diorite and Implications for the Skarn Iron Mineralization in the North China Craton
by Ruipeng Li, Shangguo Su and Peng Wang
Minerals 2025, 15(10), 1061; https://doi.org/10.3390/min15101061 - 9 Oct 2025
Viewed by 587
Abstract
Skarn-type iron ore is economically significant, and numerous skarn ore deposits have been identified in the North China Craton. The newly discovered orbicular diorite in this region is distinguished from other analogous rocks due to the accumulation of large magnetite particles, which may [...] Read more.
Skarn-type iron ore is economically significant, and numerous skarn ore deposits have been identified in the North China Craton. The newly discovered orbicular diorite in this region is distinguished from other analogous rocks due to the accumulation of large magnetite particles, which may shed new light on the genesis of this ore type. The magnetite in different parts of the orbicular structure exhibits distinct compositional differences. For example, magnetite at the edge has a small particle size (200 μm) and is associated with the minerals plagioclase and hornblende, indicating that it crystallized from normal diorite magma. By contrast, magnetite in the core has a relatively large particle size (>1000 μm), is associated with apatite and actinolite, and contains apatite inclusions as well as numerous pores. The size of magnetite in the mantle falls between that of the edge and the core. The syngenetic minerals of magnetite in the mantle include epidote and plagioclase. The magnetites in the cores of orbicules have a higher content of Ti, Al, Ni, Cr, Sc, Zn, Co, Ga, and Nb than those in the rim. The δ56Fe value of the core magnetite (0.46‰–0.78‰) is much higher than that of the mantle and rim magnetite in orbicules. Moreover, the δ56Fe value of magnetite increases as the V content of magnetite gradually decreases. This large iron isotope fractionation is likely driven by liquid immiscibility that forms iron-rich melts under high oxygen fugacity. The reaction between magma and carbonate xenoliths (Ca, Mg)CO3 during magma migration generates abundant CO2, which significantly increases the oxygen fugacity of the magmatic system. Under the action of CO2 and other volatile components, liquid immiscibility occurs in the magma chamber, and Fe-rich oxide melts are formed by the melting of carbonate xenoliths. Iron oxides (Fe3O4/Fe2O3) will crystallize close to the liquidus due to high oxygen fugacity. These characteristics of magnetite in the Tanling orbicular diorite (Wuan, China) indicate that diorite magma reacts with carbonate xenoliths to form “Fe-rich melts”, and skarn iron deposits are probably formed by the reaction of intermediate-basic magma with carbonate rocks that generate such “Fe-rich melts”. A possible reaction is as follows: diorite magma + carbonate → (magnetite-actinolite-apatite) + garnet + epidote + feldspar + hornblende + CO2↑. Full article
(This article belongs to the Special Issue Using Mineral Chemistry to Characterize Ore-Forming Processes)
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20 pages, 4643 KB  
Article
Paleoproterozoic Mafic and Ultramafic Rocks from the Mako Belt, Senegal: Implications for Back-Arc Basin Origin
by Ibrahima Dia, Tanya Furman, Kaan Sayit, Shelby Bowden, Mamadou Gueye, Cheikh Ibrahima Faye and Olivier Vanderhaeghe
Minerals 2025, 15(10), 1057; https://doi.org/10.3390/min15101057 - 5 Oct 2025
Viewed by 893
Abstract
The Mako Belt in the Kédougou-Kéniéba Inlier (eastern Senegal) preserves Paleoproterozoic (2.3–1.9 Ga) mafic and ultramafic rocks that record early crustal growth processes within the southern West African Craton (WAC). Basalt bulk rock compositions preserve primary melt signatures, whereas the associated ultramafic cumulates [...] Read more.
The Mako Belt in the Kédougou-Kéniéba Inlier (eastern Senegal) preserves Paleoproterozoic (2.3–1.9 Ga) mafic and ultramafic rocks that record early crustal growth processes within the southern West African Craton (WAC). Basalt bulk rock compositions preserve primary melt signatures, whereas the associated ultramafic cumulates are variably serpentinized and are better assessed through mineral chemistry. Basalts occur as massive and pillow lavas, with MgO contents of 5.9–9.1 wt.% and flat to slightly LREE-depleted patterns (La/Smₙ = 0.73–0.88). Primitive mantle-normalized diagrams show subduction-related signatures, including enrichment in Ba, Pb, and Rb and depletion in Nb and Ta. Most basalts and all ultramafic rocks display (Nb/La)PM > 1, consistent with enriched mantle melting in a back-arc setting. Harzburgites and lherzolites have cumulate textures, high Cr and Ni contents, and spinel with chromian cores (Cr# > 0.6) zoned sharply to Cr-rich magnetite rims that overlap basalt spinel compositions. Integration of the petrographic, mineralogical, and whole-rock geochemical data indicates the presence of mafic melts derived from a subduction-modified mantle wedge and likely formed in a back-arc basin above a subducting slab, rather than from a plume or mid-ocean ridge setting. Regional comparisons with other greenstone belts across the WAC suggest that the Mako Belt was part of a broader arc–back-arc system accreted during the Eburnean orogeny (~2.20–2.00 Ga). This study supports the view that modern-style plate tectonics—including subduction and back-arc magmatism—was already active by the Paleoproterozoic, and highlights the Mako Belt as a key archive of early lithospheric evolution in the WAC. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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17 pages, 5669 KB  
Article
Mineralogical Characterization and Provenance of Black Sand in the Xiahenan Area, Tarim Large Igneous Province
by Songqiu Zhang, Renyu Zeng, Shigang Duan, Jiayong Pan, Dong Liang, Jie Yan, Jianjun Wan, Qing Liu and You Zhang
Minerals 2025, 15(8), 884; https://doi.org/10.3390/min15080884 - 21 Aug 2025
Viewed by 645
Abstract
The Tarim Large Igneous Province (TLIP) in NW China hosts abundant Fe–Ti–V oxide deposits associated with mafic–ultramafic intrusions. In the Xiahenan area, on the western margin of the TLIP, a distinct magnetic anomaly is linked to widespread surface accumulations of black sand. However, [...] Read more.
The Tarim Large Igneous Province (TLIP) in NW China hosts abundant Fe–Ti–V oxide deposits associated with mafic–ultramafic intrusions. In the Xiahenan area, on the western margin of the TLIP, a distinct magnetic anomaly is linked to widespread surface accumulations of black sand. However, the genesis and origin of these black sand grains remain unclear. Based on mineral assemblages, this study classifies the grains of the black sand into three types: (i) plagioclase (An10–90)–ilmenite–olivine–magnetite assemblage (Sand I), (ii) plagioclase (An0–10)-fine-grained magnetite assemblage (Sand II), and (iii) hornblende–magnetite highly complex assemblage (Sand III). Mineral geochemical studies demonstrate that magnetite in Sand I and Sand II is of magmatic origin, with protolith being basaltic magma. Magnetite in Sand III was eroded from veins formed by hydrothermal processes at 300–500 °C. Ilmenite in Sand I contains a high FeTiO3 component, representing basaltic ilmenite. Olivine in Sand I has a low Fo content (43.86–47.27), belonging to hortonolite olivine. Research indicates that Sand I and Sand II share similar mineral assemblages and mineral geochemical characteristics with basalts in the Xiahenan area, suggesting they are weathering products of Xiahenan basalts or their cognate magmas. In contrast, the veined magnetite of Sand III formed during post-magmatic hydrothermal events. Full article
(This article belongs to the Special Issue Mineralization and Metallogeny of Iron Deposits)
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33 pages, 8120 KB  
Article
Origin of the World-Class Eagle, Eagle East, and Tamarack Ni-Cu-PGE Deposits
by Robert Nowak, Chad Deering and Espree Essig
Minerals 2025, 15(8), 871; https://doi.org/10.3390/min15080871 - 18 Aug 2025
Viewed by 1621
Abstract
The 1.1 Ga Mesoproterozoic Midcontinent rift hosts the Eagle, Eagle East, and Tamarack Ni-Cu-PGE deposits and Embayment Prospect. These deposits are hosted by ultramafic igneous rocks and have some of the highest Ni-Cu grades on Earth. We use new bulk-rock data and published [...] Read more.
The 1.1 Ga Mesoproterozoic Midcontinent rift hosts the Eagle, Eagle East, and Tamarack Ni-Cu-PGE deposits and Embayment Prospect. These deposits are hosted by ultramafic igneous rocks and have some of the highest Ni-Cu grades on Earth. We use new bulk-rock data and published datasets (bulk-rock, mineral chemistry, and isotopic analyses) to examine major, minor, and trace element trends of both Midcontinent rift-related alkaline and tholeiitic intrusions. In addition, we compare the geochemical data to local kimberlite-hosted lower-crustal xenoliths and local igneous (Archean) and sedimentary (Paleoproterozoic) country rocks. We found the peridotite magma compositions dominantly consist of primitive mantle compositions with varying abundances of subduction-related components, alkaline-transitional melts, and local country rock contaminates (e.g., Baraga and Animikie Basin sediments). The subduction-related components are interpreted to be derived from previous Archean and Paleoproterozoic subduction events and likely hosted within the sub-continental lithospheric mantle. Importantly, these subduction-related components are also interpreted to have acted as oxidizing agents within the melt, stabilizing sulfate (+2 FMQ (fayalite–magnetite–quartz) to FMQ) while inhibiting sulfide crystallization as the magma ascended through ~50 km of the Superior craton. This study largely corroborates the previous findings with respect to the contribution of local country rock contamination to the Eagle–Tamarack peridotite host rocks, which is estimated to be minimal (<5%). However, the incorporation of <5% reductive pelitic siltstone contamination results in strong shifts in the oxygen fugacity of the peridotite melt, from +2 FMQ to slightly below FMQ, as determined from spinel Fe3+/∑Fe ratios. This shift in oxygen fugacity resulted in the transition from total sulfate (+2 FMQ) to sulfate + sulfide (<+2 FMQ to FMQ) to total sulfide (<FMQ). This shift in oxygen fugacity is a key contributor to the formation of Ni-Cu-PGE-rich massive sulfides within the Eagle peridotite. This study presents an expanded geochemical interpretation for the exploration of Midcontinent rift-related Ni-Cu-PGE deposits to include peridotites with subduction-like signatures and contaminated via <5% reductive sedimentary country rocks. Full article
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23 pages, 1658 KB  
Article
Valorization of a Lanthanum-Modified Natural Feedstock for Phosphorus Recovery from Aqueous Solutions: Static and Dynamic Investigations
by Hamed Al-Nadabi, Salah Jellali, Wissem Hamdi, Ahmed Al-Raeesi, Fatma Al-Muqaimi, Afrah Al-Tamimi, Ahmed Al-Sidairi, Ahlam Al-Hanai, Waleed Al-Busaidi, Khalifa Al-Zeidi, Malik Al-Wardy and Mejdi Jeguirim
Materials 2025, 18(14), 3383; https://doi.org/10.3390/ma18143383 - 18 Jul 2025
Viewed by 776
Abstract
This work investigates, for the first time, the application of a modified natural magnetite material with 35% of lanthanum for phosphorus (P) recovery from synthetic and actual wastewater under both static (batch) and dynamic (continuous stirred tank reactor (CSTR)) conditions. The characterization results [...] Read more.
This work investigates, for the first time, the application of a modified natural magnetite material with 35% of lanthanum for phosphorus (P) recovery from synthetic and actual wastewater under both static (batch) and dynamic (continuous stirred tank reactor (CSTR)) conditions. The characterization results showed that the natural feedstock mainly comprises magnetite and kaolinite. Moreover, the lanthanum-modified magnetite (La-MM) exhibited more enhanced textural, structural, and surface chemistry properties than the natural feedstock. In particular, its surface area (82.7 m2 g−1) and total pore volume (0.160 cm3 g−1) were higher by 86.6% and 255.5%, respectively. The La-MM efficiently recovered P in batch mode under diverse experimental settings with an adsorption capacity of 50.7 mg g−1, which is significantly greater than that of various engineered materials. It also maintained high efficiency even when used for the treatment of actual wastewater, with an adsorption capacity of 47.3 mg g−1. In CSTR mode, the amount of P recovered from synthetic solutions and real wastewater decreased to 33.8 and 10.2 mg g−1, respectively, due to the limited contact time. The phosphorus recovery process involves mainly electrostatic attraction over a wide pH interval, complexation, and precipitation as lanthanum phosphates. This investigation indicates that lanthanum-modified natural feedstocks from magnetite deposits can be regarded as promising materials for P recovery from aqueous solutions. Full article
(This article belongs to the Special Issue Adsorption Materials and Their Applications (2nd Edition))
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27 pages, 4704 KB  
Article
Chemical Composition and Corrosion—Contributions to a Sustainable Use of Geothermal Water
by Ioana Maior, Gabriela Elena Badea, Oana Delia Stănășel, Mioara Sebeșan, Anca Cojocaru, Anda Ioana Graţiela Petrehele, Petru Creț and Cristian Felix Blidar
Energies 2025, 18(14), 3634; https://doi.org/10.3390/en18143634 - 9 Jul 2025
Cited by 1 | Viewed by 1003
Abstract
The utilization of geothermal resources as renewable energy is a subject of interest for the regions that possess these resources. The exploitation of geothermal energy must consider local geological conditions and an integrated approach, which should include practical studies on the chemistry of [...] Read more.
The utilization of geothermal resources as renewable energy is a subject of interest for the regions that possess these resources. The exploitation of geothermal energy must consider local geological conditions and an integrated approach, which should include practical studies on the chemistry of geothermal waters and their effect on thermal installations. Geothermal waters from Bihor County, Romania, have a variable composition, depending on the crossed geological layers, but also on pressure and temperature. Obviously, water transport and heat transfer are involved in all applications of geothermal waters. This article aims to characterize certain geothermal waters from the point of view of composition and corrosion if used as a thermal agent. Atomic absorption spectroscopy (AAS) and UV–Vis spectroscopy were employed to analyze water specimens. Chemical composition includes calcite (CaCO3), chalcedony (SiO2), goethite (FeO(OH)), and magnetite (Fe3O4), which confirms the corrosion and scale potential of these waters. Corrosion resistance of mild carbon steel, commonly used as pipe material, was studied by the gravimetric method and through electrochemical methodologies, including chronoamperometry, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization method, and open circuit potential measurement (OCP). Statistical analysis shows that the medium corrosion rate of S235 steel, expressed as penetration rate, is between 0.136 mm/year to 0.615 mm/year. The OCP, EIS, and chronoamperometry experiments explain corrosion resistance through the formation of a passive layer on the surface of the metal. This study proposes an innovative methodology and a systematic algorithm for analyzing chemical processes and corrosion phenomena in geothermal installations, emphasizing the necessity of individualized assessments for each aquifer to optimize operational parameters and ensure sustainable resource utilization. Full article
(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)
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26 pages, 9198 KB  
Article
The Exotic Igneous Clasts Attributed to the Cuman Cordillera: Insights into the Makeup of a Cadomian/Pan-African Basement Covered by the Moldavides of the Eastern Carpathians, Romania
by Sarolta Lőrincz, Marian Munteanu, Ştefan Marincea, Relu Dumitru Roban, Valentina Maria Cetean, George Dincă and Mihaela Melinte-Dobrinescu
Geosciences 2025, 15(7), 256; https://doi.org/10.3390/geosciences15070256 - 3 Jul 2025
Cited by 1 | Viewed by 1057
Abstract
The Eastern Carpathians are thrust to the east and north over their Eastern European foreland, tectonically covering it over an area several hundred kilometers across. Information about the nature of the underthrust part of the Carpathian foreland can be obtained from the rock [...] Read more.
The Eastern Carpathians are thrust to the east and north over their Eastern European foreland, tectonically covering it over an area several hundred kilometers across. Information about the nature of the underthrust part of the Carpathian foreland can be obtained from the rock fragments preserved in the sedimentary successions of the Carpathian fold and thrust belt, specifically in the Outer Dacides and the Moldavides. Fragments of felsic rocks occurring within the sedimentary units of the Upper Cretaceous successions of the Moldavides have long been attributed to the Cuman Cordillera—an intrabasinal ridge in the Eastern Outer Carpathians. This work is the first complex geochemical and geochronological study on the exotic igneous clasts of the Cuman Cordillera. Igneous clasts from the southern part of the Moldavides (Variegated clay nappe/formation) are investigated here. They include mainly granites and rhyolites. Phaneritic rocks are composed of cumulus plagioclase, albite, amphibole and biotite, and intercumulus quartz and potassium feldspar, with apatite, magnetite, sphene, and zircon as main accessories, while the porphyritic rocks have a mineral assemblage similar to that mentioned above, displayed in a porphyritic texture with a usually crystallized groundmass. SHRIMP U-Pb zircon dating indicated the 583–597 Ma age interval for magma crystallization. Based on calcareous nannofossils, the depositional age of the investigated igneous clasts is Cenomanian to Maastrichtian, implying that the Cuman Cordillera was an emerged piece of land, herein an active source of sediments in the flysch basin for at least 40 Ma, from the Early Cretaceous (Aptian) to the Late Cretaceous (Maastrichtian). The intrusive and subvolcanic rocks show similar trends for trace and major elements, evincing their comagmatic nature. The enrichment in LILE and LREE relative to HFSE and HREE, as well as the element anomalies (e.g., negative Nb, Ta, and Eu and positive Rb, Ba, K, and Pb) suggest a convergent continental plate margin tectonic setting. Mineral chemistry suggests magma crystallization in relatively oxic conditions (magnetite series), during ascent within a depth of 15 km to 5 km. The igneous rocks attributed to the Cuman ridge display compositional and geochronological features similar to Brno and Thaya batholiths in the Brunovistulian terrane, which could be a piece of the Carpathian foreland not covered by the Tertiary thrusts. Our data confirm the non-Carpathian origin of the igneous clasts, revealing a Neoproterozoic history of the Carpathian foreland units, which include a Cadomian/Pan-African continental arc, exposed mainly during the Late Cretaceous as an intrabasinal island of the Alpine Tethys, traditionally known as the Cuman Cordillera. Full article
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26 pages, 6169 KB  
Article
Petrogenesis of Mafic–Ultramafic Cumulates in the Mayudia Ophiolite Complex, NE Himalaya: Evidence of an Island Arc Root in Eastern Neo-Tethys
by Sapneswar Sahoo, Alik S. Majumdar, Rajagopal Anand, Dwijesh Ray and José M. Fuenlabrada
Minerals 2025, 15(6), 572; https://doi.org/10.3390/min15060572 - 27 May 2025
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Abstract
Amphibole-rich cumulates provide crucial information pertaining to the petrogenetic history of suprasubduction zone ophiolites and are, therefore, helpful in constraining the evolution and closure of the Neo-Tethys during the late Cretaceous to the early Tertiary period. Following this, the present contribution examines the [...] Read more.
Amphibole-rich cumulates provide crucial information pertaining to the petrogenetic history of suprasubduction zone ophiolites and are, therefore, helpful in constraining the evolution and closure of the Neo-Tethys during the late Cretaceous to the early Tertiary period. Following this, the present contribution examines the meta-hornblendite and meta-hornblende-gabbro lithologies in the Mayudia ophiolite complex (MdOC), NE Himalaya, based on their field and petrographic relations, constituent mineral compositions, whole rock major and trace element chemistry and bulk strontium (Sr)—neodymium (Nd) isotope systematics. MdOC cumulates potentially represent the fossilized record of an island arc root, where amphibole + titanite + magnetite was fractionally crystallized from a super hydrous magma (10.56–13.61 wt.% melt water content) prior to plagioclase in a stable physico-chemical condition (T: 865–940 °C, P: 0.8–1.4 GPa, logfO2: −8.59–−11.19 unit) at lower crustal depths (30–38 km). Such extreme hydrous nature in the parental magma was generated by the flux melting of the sub-arc mantle wedge with aqueous inputs from the dehydrating slab. A super hydrous magmatic reservoir was, therefore, extant at sub-arc mantle depths in the eastern Neo-Tethys, which has likely modulated the composition of the oceanic crust during intraoceanic subduction. Full article
(This article belongs to the Special Issue Tectonic Evolution of the Tethys Ocean in the Qinghai–Tibet Plateau)
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26 pages, 6627 KB  
Article
Synthesis of Lanthanum-Modified Natural Magnetite: Characterization and Valorization for Phosphorus Recovery from Aqueous Solutions
by Hamed Al-Nadabi, Salah Jellali, Wissem Hamdi, Afrah Al-Tamimi, Ahmed Al-Raeesi, Ahmed Al-Sidairi, Waleed Al-Busaidi, Ahlam Al-Hanai, Khalifa Al-Zeidi, Malik Al-Wardy and Mejdi Jeguirim
Materials 2025, 18(10), 2283; https://doi.org/10.3390/ma18102283 - 14 May 2025
Cited by 1 | Viewed by 974
Abstract
In this research work, a natural sample from an Omani magnetite (MG) deposit was used for the synthesis of a magnetite decorated with ferrihydrite (MG-Fh), and two lanthanum (La)-modified materials at mass percentages of 5% (MG-Fh-La-5) and 15% (MG-Fh-La-15). These materials were first [...] Read more.
In this research work, a natural sample from an Omani magnetite (MG) deposit was used for the synthesis of a magnetite decorated with ferrihydrite (MG-Fh), and two lanthanum (La)-modified materials at mass percentages of 5% (MG-Fh-La-5) and 15% (MG-Fh-La-15). These materials were first characterized using various analytical techniques. Then, their phosphorus (P) recovery efficacy from aqueous solutions was studied in batch mode under a wide range of experimental conditions. The characterization results show that compared to the raw feedstock, MG-Fh, MG-Fh-La-5, and especially MG-Fh-La-15 have improved structural, textural, and surface chemistry properties. Adsorption tests indicate that due to the deposition of high contents of lanthanum oxides on its surface, the MG-La-15 exhibited a large P uptake capacity (34.5 mg g−1), which is significantly superior to those determined for MG-La-5 (24.3 mg g−1), MG-Fh (12.4 mg g−1), and various engineered materials published in the literature. Moreover, these materials retain an interesting ability to recover P from real wastewater with a highest adsorbed mass of 27.3 mg g−1, observed for MG-La-15. The P recovery seems to involve both physical and chemical mechanisms, including electrostatic interactions and complexation. This research work shows that La-modified magnetite can be considered a promising and eco-friendly material for P recovery from liquid effluents. Full article
(This article belongs to the Special Issue Adsorption Materials and Their Applications (2nd Edition))
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