Minerals doi: 10.3390/min16050517

Authors: Masao Ban Fumito Otomo Motohiro Sato Takumi Imura

Debris avalanche deposits related to the edifice collapse of the summit area of Zao Volcano are reported for the first time at the volcano’s eastern foot. These deposits extend approximately 11–15 km from the summit. Based on their spatial distribution and clast petrology, the deposits are interpreted to have originated from the Umanose caldera. Deposit thickness ranges from 20 to 30 m in the western and northern parts to over 50 m in the eastern part, with an estimated volume of approximately 0.3–0.4 km3, comparable to that of the summit caldera depression. Matrix facies occur at most outcrops, whereas block facies are found at only three sites. The vertical drop-to-runout distance ratio (H/L) is ~0.09, which falls within the typical range for debris avalanches but still indicates relatively high mobility. Based on its volume and stratigraphic relationships, the collapse may have been associated with eruptive activity (e.g., phreatic processes) or alternatively with a non-eruptive large-scale failure of a hydrothermally altered zone beneath the summit area. The collapse is considered to mark the onset of the latest activity stage of Zao Volcano, although the precise temporal relationship remains uncertain. The petrological characteristics of the magma differ markedly from those of the preceding stage, but the relationship between collapse processes and magma evolution remains hypothetical and is not directly demonstrated in this study.

Minerals doi: 10.3390/min16050516

Authors: Tahir İnan Turan Yurdal Genç

Gold-enriched silica-listvenite rock from the Kaymaz Gold Deposit (KGD) was investigated to determine the effect of regional tectonism and Eocene granite intrusion on gold mineralization. The questions “is granite a heat–fluid source or a lithologic barrier?” and “how does regional tectonism affect gold mineralization?” remain unclear. This study aims to clarify these questions via field studies, core sample observations, petrography, ore microscopy, scanning electron microscopy (SEM), XRD, and fluid inclusion analyses; these methods were applied to samples collected from four different sites within the KGD (1—Damdamca, 2—Karakaya, 3—Mermerlik, and 4—Kızılağıl). The highest-grade gold mineralization is present in the listvenite rock in the fault-controlled contact zone between serpentinite and granite, whereas granite hosts minor gold and silver enrichments near the contact. The orientations of contacts are compatible with the NW-SE-trending Eskişehir fault zone in Karakaya and the NE-SW-trending tear faults in Damdamca. Listvenite is silica-rich and has high iron oxy-hydroxide content, while granite is argilized and silicified along the contact with listvenite. Native gold grains were found between the quartz minerals of listvenite and granite. The adsorption of gold by goethite ± lepidocrocite has been observed in the listvenite samples of Mermerlik. Chromite, Ni-sulfide minerals, pyrite, arsenopyrite, galena, native silver, acanthite, iodargyrite, and goethite ± lepidocrocite are the other detected ore minerals. Secondary Cr-Fe-Mn oxide minerals were detected in a granite sample via SEM analyses. The data indicates that listvenitization-causing fluid partially remobilized these metals along with Au and reprecipitated them in the granite during mineralization. The homogenization temperatures (Th) (°C) of fluid inclusions vary between 116 and 393 °C, and the Th (°C) distribution indicates multi-phase mineralization. The Th (°C) values of listvenite and silicified granite are quite similar, which indicates that the same hydrothermal fluid circulated in both lithologies. The low salinity values (1.2–5.4%) indicate that the hydrothermal fluid was derived predominantly from meteoric water. The liquid–vapor ratios of inclusions and quartz textures indicate non-boiling conditions. Gold enrichment in the KGD developed in relation to the circulation of hydrothermal fluids along the faults. The KGD shows typical fluid inclusions, alteration properties, and mineral paragenesis of low-sulfidation-type epithermal deposits. Our study data indicates that meteoric water-rich hydrothermal fluid circulated along the fault zones, dissolved Au and other related elements from the serpentinite, and reprecipitated in the listvenite-altered granite. Granite acts as an impermeable barrier, leading to the circulation of hydrothermal fluids through the contact. Supergene activities affect the mineralization in both Mermerlik and Kızılağıl. No evidence indicating the magmatic origin of gold mineralization was observed.

Minerals doi: 10.3390/min16050515

Authors: Xintao Zhang Qi Fu

Rhyolites serve as unconventional hydrocarbon-water reservoirs and also as high-quality volcanic reservoirs. Well BZ8-3S-B exhibits maximum productivity in vertical wells. Drilling results reveal significant mega-scale heterogeneity among different wells within the same rhyolitic volcanic edifice, as well as between different intervals within single wells. To clarify the mega-scale heterogeneity characteristics of rhyolitic reservoirs, this study investigates Block BZ8-3S in the Bozhong Depression, Bohai Bay Basin, China. Based on sidewall cores, logging data and seismic datasets, comprehensive research methods including petrographic/mineralogical analysis, image processing, porosity–permeability testing, mercury capillary pressure measurements, logging facies interpretation and seismic facies analyses were employed. The study establishes correlations between volcanic edifice architecture, stratigraphic boundaries, depositional units and their relationships with reservoir space composition/permeability characteristics, aiming to identify principal controlling factors of mega-scale heterogeneity through systematic stratigraphic architecture analysis. The key findings are summarized as follows: (i) The volcanic edifices in Block BZ8-3S exhibit massive-pseudostratified structural characteristics. (ii) Wells A and B belong to the same volcanic edifice system but occupy distinct facies belts. Well A is located in the crater-near crater belt, while Well B lies in the proximal belt. (iii) Eruptive interval unconformity boundaries (EIUBs) are identified at 1 and 4 depths in Wells A and B, respectively. The EIUBs control the vertical heterogeneity of depositional-unit reservoirs. Reservoir porosity exhibits inverse correlation with burial depth below EIUBs, indicating stratigraphic boundary control on reservoir development. Mega-scale heterogeneity of rhyolitic reservoirs is primarily controlled by the number of stratigraphic boundaries and depositional unit types. From an exploration perspective, lava dome deposited units within crater-near crater belt should be avoided, while priority should be given to proximal belt targets featuring thick sequences with high proportions of lava flow units. This study provides critical insights for optimizing exploration strategies and enhancing development efficiency of rhyolite volcanic edifices.

Minerals doi: 10.3390/min16050514

Authors: Medet Junussov Geroy Zh. Zholtayev Zamzagul T. Umarbekova Moldir A. Mashrapova Shattyk Miniskul Mohamed Abdelnaby Oraby Yerzhan Nurmakanov Maxat K. Kembayev

Clay minerals in coal play a key role in controlling mineralogical composition, geochemical signatures, and the industrial behavior of coal and its combustion residues. This study investigates the occurrence, provenance, and potential applications of clay minerals in Carboniferous ash-rich coals from the Bogatyr, Lenin, and Saradyr coal mines in northeastern Kazakhstan. A total of 60 coal samples were analyzed using XRD, SEM–EDS/BSE, XRF, and ICP-OES following acid leaching. Based on ash yield, 52 samples were classified as coal (<50% ash), while 8 samples were classified as carbonaceous shale or mudstone (>50% ash). Mineralogical assemblages show clear variability among the studied mines. Saradyr samples are strongly quartz-dominated with lower clay proportions, Bogatyr samples exhibit highly heterogeneous quartz–clay–mica assemblages, whereas Lenin samples are relatively more clay-rich and dominated by kaolinite and illite-group minerals. Across all samples, kaolinite is the dominant clay mineral (16.6–46 wt.%), occurring mainly as authigenic pore- and cell-filling aggregates. Minor phases include illite–muscovite (7.1–29.9 wt.%), illite–smectite (up to 7.6 wt.% in Bogatyr), and smectite–montmorillonite (0.4–0.7 wt.%). Clay minerals occur as discrete particles, coatings, and pore fillings, contributing to ash formation; however, their correlation with ash yield is weak (R = 0.03–0.05), reflecting heterogeneous mineral inputs and diagenetic overprinting. All geochemical data are reported on a high-temperature coal ash (HTA) basis (815 °C). Geochemical indices (CIA, CIW, CIX) and Al2O3/TiO2 ratios (1.8–17.4) indicate variable provenance and moderate to high weathering intensity, reflecting mixed mafic to intermediate source rocks. A total of 23 trace elements were identified. Au occurs at trace levels (up to 0.02 ppm), while selected rare earth elements (REE: Ce, Dy, Eu, La, Nd, Sm, Y, Yb) average 0.2–0.3 ppm, indicating negligible economic recovery potential. REEs show a strong positive correlation with clay minerals (r = 0.93), indicating adsorption and minor structural incorporation. In contrast, Au correlates with As, V, Zn, Cu, Ni, and Nb, suggesting sulfide association. HTA is enriched in SiO2–Al2O3 phases dominated by kaolinite and quartz, indicating strong potential for cement, geopolymer, ceramic, and zeolite applications.

Minerals doi: 10.3390/min16050513

Authors: Mahsa Pourmohammad Josep Oliva Hernan Anticoi Carlos Hoffmann Sampaio César Valderrama José Luis Cortina Mònica Reig

Waste printed circuit boards (WPCBs) account for approximately 3%–6% of electrical and electronic equipment (WEEE) and contain high concentrations of valuable metals such as copper, often at levels higher than those in natural ores. Consequently, WPCB recycling represents an important opportunity for resource recovery through urban mining and supports the transition toward a circular economy. This study investigates the application of a Falcon centrifugal concentrator for the gravity separation of metallic and non-metallic fractions from WPCBs, with a focus on fine particles below 300 μm. Despite its potential, this method has received little attention, particularly in research. Optimal operating conditions were identified as 80 Hz rotation frequency and 1 LPM water flow rate for particles −100 μm, and 30 Hz rotation frequency and 3 LPM water flow rate for particles in the −300 + 100 μm range. Under these conditions, copper recovery reached 98.25% with Cu content of 10.34% for the coarse fraction and 95.97% with Cu content of 4.47% for the fine fraction after a cleaner stage. The results demonstrate that Falcon gravity concentration is an efficient technique for recovering fine metallic particles and outperforms the multi-gravity separator (MGS). A sustainable beneficiation flowsheet is proposed to enhance metal recovery and reduce environmental impacts.

Minerals doi: 10.3390/min16050512

Authors: Muhammad Idrees Shahid Iqbal Abdul Bari Qanit Michael Wagreich Mehwish Bibi Mansoor Ahmad Bilal Wadood

The Middle Triassic Tredian Formation of the Salt Range, Pakistan, consists of sandstones with interbedded shale in the lower part and minor dolomite in the upper part. Conventional grain-size analysis has been widely used as a sedimentological tool to elucidate depositional environments and the mode of transportation of detrital sediments. This study presents the first integrated application of a Decision Tree Classifier (a machine learning model) with field and petrographic evidence to interpret grain-size statistics for the analysis of depositional environments of the Tredian Formation in the Salt Range, Pakistan. Stratigraphic sections of the Tredian Formation were measured and sampled in the Nammal Gorge and Zaluch Nala in the Salt Range for detailed sedimentological and grain-size analyses. The lower part of the Tredian Formation (Landa Member) consists of interbedded sandstone and shale (LF-1) characterized by large-scale slumps, parallel lamination, ripple marks, and cross-bedding. The LF-1 is overlain by the Katkhiara Member, which is dominated by thick sandstone (LF-2) with planar and trough cross-bedding and contains dolomite beds (LF-3) in the upper part. Grain-size statistics show that the sandstones are fine-to-medium-grained, well-to-very-well-sorted, near-symmetrical, and very platykurtic. Machine learning-based bivariate plots suggest that most of the samples are grouped, with some showing scattered trends. The Linear Discriminant Function (LDF) analysis indicates that the Tredian Formation was deposited in fluvial–deltaic to shallow marine environments with sand reworking and redistribution under aeolian/beach settings. The Decision Tree Classifier Model (DTCM) predicted fluvial to shallow marine depositional environments for the Tredian Formation and shows strong agreement with field-based lithofacies interpretation, demonstrating its reliability as a predictive tool. Thus, the present study demonstrates that integrating grain-size-based machine learning and statistical analysis with traditional sedimentology provides valuable insights into depositional settings and enhances the reliability of interpretations of ancient sedimentary environments.

Minerals doi: 10.3390/min16050511

Authors: Richard Diaz Alorro Hajime Kijitani Joel Hao Jorolan Jonah Gamutan Carlito Baltazar Tabelin Mayumi Ito Naoki Hiroyoshi

Repurposing mineral processing waste offers both environmental and economic benefits, reducing the disposal burden while enabling mineral resource recovery. A magnetic adsorbent, with an Fe3O4 content of 71.0%, collected from waste copper converter slag was utilized to recover gold (Au3+) from chloride solution. The adsorbent was separated from the slag samples by crushing, grinding to an average particle size of 30 μm, and magnetic separation. Batch adsorption experiments were performed to evaluate the effects of pH, contact time, chloride concentration, and initial gold concentration on gold uptake amount. The material recovered over 99% of gold from chloride solution under acidic conditions and in the near-neutral pH range. The gold sorption rate was also relatively fast and over 98% recovery was achieved after just 15 min of contact time. Increasing chloride concentration did not influence gold uptake. Parameter studies and spectrometric analyses suggest that chalcocite (Cu2S) and metallic copper present in magnetite slag reduced the gold chloride complex to metallic gold. These results suggest that converter magnetite slag is a potentially effective sorbent to recover gold from secondary sources due to its selectivity and low cost. Moreover, gold-loaded magnetite slag can be easily separated from the solution by magnetic separation and then recirculated to the smelting stage of copper processing to recover the deposited gold and other precious metals. Overall, this work highlights a pathway to transform waste into opportunity, reinforcing sustainability in mineral processing operations.

Minerals doi: 10.3390/min16050510

Authors: Jiacong Wu Dian Luo Yubin Li Duo Ji Hairui Yang Suiliang Dong Wei Li Khin Ei Thu

Early Cretaceous volcanic rocks are widely developed in the Longzi area, southern Tibet. Their petrogenesis and tectonic setting are important for understanding the initial breakup of eastern Gondwana and its deep geodynamic mechanisms. This study integrates field observations, petrography, zircon U-Pb geochronology and trace elements, whole-rock major and trace element geochemistry, and Sr-Nd-Pb isotopes to investigate the origin and tectonic significance of these rocks. The analyzed suite comprises diabase and rhyolite, with no intermediate compositions in the studied samples, thus defining a mafic–felsic volcanic association. Zircon U-Pb ages indicate Early Cretaceous magmatism at 132–138 Ma for the diabase and 132–134 Ma for the rhyolite. Geochemically, the mafic rocks are enriched in LREEs and HFSEs and display OIB-like trace-element characteristics, with εNd(t) values ranging from −0.2 to +4.4, indicating derivation from low-degree partial melting of a spinel–garnet lherzolite source modified by limited interaction with the lithospheric mantle. The felsic rocks show pronounced negative Eu anomalies, A-type granite affinities, and εNd(t) values ranging from −12.2 to −11.9, indicating derivation mainly from partial melting of upper-crustal materials. The marked geochemical and isotopic contrast between the mafic and felsic rocks argues against simple fractional crystallization from a common parental magma. Combined with regional geological data, these results indicate that the Longzi mafic–felsic volcanic association formed in an intraplate extensional setting related to Kerguelen-plume thermal input during the initial breakup of eastern Gondwana.

Minerals doi: 10.3390/min16050509

Authors: Anne M. Hofmeister

Heat transport properties of serpentine minerals are important to the thermal state of subduction zones, but available data contain systematic errors from contact losses, radiative gains, deformation with pressure (P), and/or modelling short-comings. Here, laser flash analysis (LFA) provides thermal diffusivity (D) within ±3% as a function of temperature (T) of perpendicularly oriented, nearly pure Mg3Si2O5(OH)4 polymorphs, Al-rich lizardite with minor brucite, three serpentinites, plus chrysotile and lizardite near Ni3Si2O5(OH)4. Visible spectra show that Fe is mostly ferric and Cr3+ occasionally occupies tetrahedral sites. The proposed coupled substitution of Al3+ + OH− replacing Si4+ + O2− accounts for extra OH− peaks in infrared spectra. Rietveld refinements and infrared spectra reveal that serpentine dehydration in LFA runs begins near 800 K. Thermal conductivity (K) vs. T is calculated within ~±5% from D, available heat capacity data, and ambient density. For antigorite, D and K are strongly anisotropic whereas chrysotile has extreme differences, but lizardite is nearly isotropic. A thermodynamic identity provides ∂(lnK)/∂P = 11 ± 1% Gpa−1 for soft serpentine, double that of hard olivine. Lizardite becomes more thermally conductive than olivine near the 1 bar decomposition temperature, which increases with P. Through feedback, and because released H2O vapor carries heat upwards, P,T conditions in serpentinized slabs follow the decomposition phase boundary during subduction.

Minerals doi: 10.3390/min16050508

Authors: Jun Zhong Juxing Tang Brant Wang Pan Tang Bin Lin Yixuan Li Mengdie Wang Jing Qi Zhichao Wang Shuhui Xu Yuke Xie

Jiama is a significant porphyry system in Tibet’s Gangdese Metallogenic Belt, characterized by a typical composite system with multicenter mineralization. The North Zegulang Ore Block, a recently identified mineralization center in the Jiama mining area, has remained understudied, particularly regarding its ore-forming fluid evolution. This study integrates microscopic identification, EPMA, and LA-ICP-MS to investigate the mineral chemistry of widely developed chlorite in the North Zegulang Ore Block, aiming to elucidate fluid evolution and its implications for identifying the mineralization center. Chlorite in the North Zegulang Ore Block is genetically classified into retrograde (Chl-1) and hydrothermal (Chl-2) types. Both are Fe-rich varieties, indicating formation under reducing conditions. Element substitution is dominated by Fe2+-Mg2+ exchange, accompanied by Tschermak and di-trioctahedral substitutions. The chlorite geothermometer yields formation temperatures of 260–400 °C and log fO2 values of −38 to −26 for Chl-1, while Chl-2 shows a wider temperature range of 220–400 °C and log fO2 values of −42 to −20, reflecting a medium-temperature, low-oxygen-fugacity environment. Outward from the granodiorite porphyry, fluid temperature decreases and Cu-Mo grades gradually decrease, confirming the intrusion as the mineralization center. With increasing distance from the mineralization center, chlorite Mg/Sr, Ti/Sr, and Ti/Pb ratios progressively decrease, whereas Th/U ratios and Sr, Th, U, and B contents increase. These systematic variations demonstrate that chlorite serves as an effective exploration tool in collisional-type porphyry systems.

Minerals doi: 10.3390/min16050507

Authors: Yankun Jian Haiying Hu Wenqing Sun Song Luo Pengfei Wang Liping Wang Jinlong Zhu Songbai Han Lidong Dai

Hydrogen (H) is the most abundant element in the solar system. In the Earth’s interior, it primarily exists in the form of hydrogen gas, water, atomic hydrogen, and hydroxyl groups. Hydrogen gas, as a clean energy source, is widely distributed within the Earth and is mainly generated through serpentinization, with minor contributions from water radiolysis, rock fracturing, biological activity, etc. Hydrogen sequestration occurs mainly through clay adsorption, entrapment under rock layers, dissolution in water, and fluid inclusions. Besides being present as pore water, hydrogen in the deep Earth predominantly resides in minerals as point defects related to hydrogen species (e.g., OH−, H+). During the Earth’s evolution, substantial hydrogen was stored in the deep Earth through accretion, and surface water has been transported into the Earth’s interior via subducting slabs; meanwhile, it can migrate upward through magmatic activity and mantle plumes. The inputs and outputs constitute the global hydrogen cycle. Hydrogen concentration and distribution are highly heterogeneous across the crust, mantle and core. The upper mantle is likely mostly dry, while the Earth’s core is potentially a large reservoir of hydrogen. Small amounts of hydrogen can profoundly influence the physicochemical properties of the Earth’s interior materials, as well as the dynamic processes within the Earth’s interior.

Minerals doi: 10.3390/min16050506

Authors: Jiuda Sun Xiaohu Li Zhuoyi Wang Kai Chen Zhongyuan Xu

Seamount basalts undergoing long-term seawater immersion and percolation are subject to varying degrees of low-temperature alteration, causing a release of substantial amounts of Sr-Nd-Pb-Hf into seawater and thereby providing a sustained, long-term, mantle-derived source for marine material cycling. Such a mantle input mixes with crustal weathering material settled to the ocean via rivers and aeolian dust, resulting in crust-mantle mixing, altogether constraining the Sr-Nd-Pb-Hf isotopic compositions of seawater and polymetallic crusts. Among these, the isotopic compositions of Sr and Pb more closely resemble those of terrigenous input materials, while Nd isotopes indicate a roughly averaged mixing mechanism. The Hf isotopic composition approaches that of enriched mantle-derived Ocean Island Basalts (OIBs). Low-temperature-altered minerals in basalt, such as montmorillonite and phillipsite, possess both permanently negative and variable charges. This causes the formation of an electrostatic field, resulting in an adsorptive potential that facilitates the initial growth of charged Fe and Mn colloidal particles on the surfaces of altered basalt. Simultaneously, Fe, Mn, Co, Ni, and Rare-Earth Elements (REEs) released during the low-temperature alteration process contribute essential material for the growth of a polymetallic crust.

Minerals doi: 10.3390/min16050505

Authors: Marcella Di Bella Davide Romano Valentina Volpi Francesco Italiano Giuseppe De Rosa Alessandro Tripodo Valentina Esposito Teresa Romeo Giuseppe Sabatino

Shallow-water hydrothermal systems in active volcanic arcs serve as natural analogs for geothermal reservoir characterization and potential sources of Critical Raw Materials (CRMs). This study examines the Panarea hydrothermal system (Aeolian Islands, Tyrrhenian Sea, 37–207 m depth) to characterize its mineralogical facies and assess CRM enrichment patterns. Sixteen sediment samples collected during 2013–2015 research cruises were analyzed using SEM-EDS, XRPD with Rietveld refinement, and XRF. Four hydrothermal alteration facies were identified: (i) a low-temperature iron oxide facies dominated by nanocrystalline goethite with enrichments in As, V, and Mo; (ii) an argillic to propylitic facies containing smectite-group clays and high-temperature silica polymorphs, consistent with alteration at 200–350 °C; (iii) a phyllic to propylitic facies showing exceptional Ba enrichment (up to 46,976 ppm) and base-metal sulfide accumulations; and (iv) an advanced argillic facies including the first documented aluminophosphate–sulfate mineral at Panarea, a svanbergite–woodhouseite solid solution. Vanadium concentrations at Panarea exceed values reported across the Tyrrhenian–Aeolian domain, ranking this site among the highest-V shallow hydrothermal fields in the Mediterranean. These findings support a genetic model involving fault-controlled seawater circulation, magmatic CO2 input, and episodic redox fluctuations, providing baseline data for CRM cycling and geothermal evaluation in Mediterranean submarine volcanic systems.

Minerals doi: 10.3390/min16050504

Authors: Yu Huang Wen-Hao Tang Hui-Shou Ye Peng Wang Jian-Hua Ding Wei-Wei Chao Yan-Wen Tang Jun Liu Yu-Hong Zhang

The Niutougou ore area (~31 t Au) is located in the Xiong’ershan district at the southern margin of the North China Craton (NCC). From north to south, the Niutougou ore area is divided into three main parts, corresponding to the gold deposits in the Songligou altered rocks, the J25-J26 breccia, the Vein VII lode gold deposit, and the Shangzhuang altered rocks. The timing of gold mineralization and the formation age of the J26 breccia pipe have not been well constrained in this ore area. Hydrothermal xenotime and apatite are closely related to gold mineralization. The in situ xenotime U–Pb ages of the J26 breccia pipe and Vein VII show U‒Pb lower intercept ages of 151.2 ± 2.0 Ma and 155.9 ± 1.6 Ma, respectively. The in situ U‒Pb age of the Shangzhuang apatite shows a U‒Pb lower intercept ages of 153.4 ± 2.6 Ma. The U–Pb concordia ages and weighted mean ages of the cement zircons from the J26 breccia pipe are 155.8 ± 0.4 Ma, and 155.9 ± 0.8 Ma, respectively, determined via sensitive high-resolution ion microprobe (SHRIMP) analysis. The molybdenite veins in the J26 breccia pipe cut the cement and different types of breccia and have a Re–Os isochron age of 155.9 ± 2.9 Ma and weighted mean age of 155.9 ± 1.1 Ma. Thus, the formation age of the breccia pipe is Late Jurassic. The subduction of the paleo-Pacific Plate beneath the NCC and the back-arc extensional setting in the Late Jurassic might have caused gold mineralization in the southern margin of the NCC.

Minerals doi: 10.3390/min16050503

Authors: Jeffrey A. Steadman Ross R. Large Sebastien Meffre Paul Olin Ivan A. Belousov David Huston

The distribution and concentrations of gold and other trace elements in numerous pyrite-bearing ore samples from volcanic-hosted massive sulfide (VHMS) deposits were obtained using LA-ICPMS imaging techniques. Pyrite in VHMS deposits is characterized by low Co and Ni (generally less than 100 ppm Co and Ni, but rarely above 1000 ppm in either element). On the other hand, Cu, As, Ag, Au, Sb, Mn, Tl, and Pb are commonly elevated above background and appear to be deposited in multiple forms, including solid solution as well as nano- and micro-inclusions of other mineral phases. Gold is predominantly present in solid solution within the crystal lattice. Such trace element signatures in pyrite are indicative of moderate- to high-temperature hydrothermal fluids varying in pH from moderately to strongly acidic. Pyrite from VHMS-style mineralization is distinguishable from pyrite in other deposit types by its relatively low abundance of Co and Ni. For example, pyrite from IOCG-type mineralization is nearly always enriched in Co at or above the weight-percent level, with lower but still elevated concentrations of Ni. In addition, IOCG pyrites do not contain elements such as Sb, Tl, or Pb in solid solution. Pyrite from porphyry-style Cu-Au-Mo mineralization likewise contains higher average Co and Ni than VHMS pyrite and lacks solid solution deportment of Sb, Tl, Pb, and other associated elements. This study underscores the effectiveness of trace element imaging via LA-ICPMS for the discrimination of pyrite from different mineral systems and for detailed paragenetic information.

Minerals doi: 10.3390/min16050502

Authors: Huinan Yang Mingji Jin Bolong Wen Nana Luo Rui Yu

In order to evaluate the utilization potential and environmental risk of iron tailings in ameliorating soda saline–alkali soil, a leaching experiment of iron tailings was carried out by simulating the soil acid–base environment and the saline–alkali stress environment of soda saline–alkali, and the basic physicochemical properties and the content and leaching characteristics of metal elements of iron tailings were analyzed to evaluate the environmental risk. The results showed that the iron tailings sand had a large specific surface area (0.66~0.91 m2·g−1) and a rich pore structure (pore diameter 9.07~11.48 nm), which was conducive to the adsorption of salt-alkali by iron tailings sand. The main chemical composition of iron tailings is SiO2 (33.39%~57.32%) and Fe2O3 (8.47%~14.94%), the content of plant nutrient elements in iron tailings is abundant, and the content of risk elements is far below the national standard limit. The leaching experiment results indicated that under acid or alkali conditions, the leaching amounts of various metal elements from the iron tailings met the national water quality standards for farmland irrigation, with Cd, Hg, Mn, Al, Ca, and others being more readily leached under acidic conditions. Under the same pH conditions, Cd, Hg, As, Al, and others were more readily leached under the soda saline–alkali environment. Unlike in the soil acid–base environment, the correlations between the leaching amounts of different metals were weaker under the combined soda saline–alkali stress, with only As and Al showing a positive correlation with the pH of the leachate, though the correlation was not significant. This study confirms that the environmental risk of using iron tailings for the improvement of soda saline–alkali soil is relatively low, and long-term changes in the contents of heavy metals such as As and Al in the soil should be given focused attention in future work.

Minerals doi: 10.3390/min16050501

Authors: Zachary F. M. Burton Janice L. Bishop

The volcanic island of Fuerteventura (Canary Islands, Spain) offers the opportunity to investigate aqueous alteration in Mars-like environments. As on Mars, landscapes on Fuerteventura are typified by mafic volcanic landforms, minimal precipitation, strong winds, and minimal or absent vegetation. In this study, we perform reflectance spectral and geochemical analysis of near-surface basaltic materials from Fuerteventura’s Gairía caldera, as well as samples from a nearby arroyo. Tephra, outcrop rock, and soil-like material exhibit variations in color, spectral properties, mineralogy, and major oxides. Visible/near-infrared (VNIR) spectra of orange/light-brown materials have higher reflectance values and much stronger features attributed to phyllosilicates (including H2O and Al-OH bands near 1.41–1.45, 1.91–1.92, 2.21, and 2.76 µm characteristic of montmorillonite in caldera and arroyo samples, plus shoulder features near 1.38 and 2.17 µm and a band at 2.70 µm indicative of kaolinite/halloysite in arroyo samples) compared to black/brown materials. Additionally, several of the highly altered samples contain spectral bands due to calcite at 2.33, 2.53, 3.36, 3.47, and 3.97 µm. Major oxide data reveal similar distinctions between lighter orange/tan (altered) versus darker (unaltered) samples. Lighter and orange-colored samples show elevated Al2O3 and depleted Fe2O3T, MgO, CaO, and Na2O, as well as higher chemical index of alteration (CIA) values, overall characteristic of water-soluble cation release (and secondary clay formation) during incipient-to-intermediate chemical weathering of basalt. Gairía weathering trends inform phyllosilicate formation in arid volcanic settings broadly. Of particular interest is the chemical alteration of basalt to montmorillonite and kaolinite/halloysite taking place in warm but water-limited desert conditions, suggesting the potential for clay formation in analogous (warm but relatively dry) paleoenvironments on early Mars.

Minerals doi: 10.3390/min16050500

Authors: Jianyong Wu Bin Liu Jing Zou Ziqiang Long Songxin Ye Guodong Zheng Liang Qiu

The uranium metallogenic potential of the Dadongshan–Guidong granite belt in northern Guangdong, especially the Jiangwan area in the eastern Dadongshan pluton, remains unclear, which hinders the evaluation of exploration prospects in this area. In this study, we present new data on the mineralogy, U-Pb geochronology, trace element, and sulfur isotopic compositions of pitchblende and associated pyrite from the Jiangwan uranium deposit (JUD). The uranium ore is dominated by pitchblende, which commonly occurs as crustiform and fine veinlet-like aggregates. Part of the euhedral-to-subhedral pyrite grains are enclosed or partially replaced by pitchblende. LA-ICP-MS analyses of pitchblende yielded a Tera–Wasserburg lower intercept age of 60.2 ± 0.5 Ma (MSWD = 2.6, n = 16), indicating that uranium mineralization occurred during the Paleocene. Additionally, the pitchblende has ΣREE contents of 2489–4960 ppm and high U/Th ratios (>1000), indicating that the pitchblende has a hydrothermal origin, forming under moderate- to low-temperature conditions (T< 350 °C). HREE-enriched patterns suggest that carbonate complexing played an important role in uranium transport. Weak positive Ce anomalies in pitchblende, together with pervasive hematitization, indicate relatively oxidizing conditions for the ore-forming fluid. Pyrite has Co/Ni ratios of 1.03–4.53, indicating a hydrothermal origin. The δ34S values of pyrite, varying from −4.23‰ to −1.21‰, suggest that the sulfur source was unlikely to be derived solely from the granitic host rocks, but may have been influenced by mafic dike-related sulfur and hydrothermal fluid–rock interaction. Combined petrographic and geochemical evidence suggests that pyrite formed before pitchblende and likely acted as an important reductant during uranium precipitation. These results indicate that the JUD records a Paleocene hydrothermal uranium mineralization event, which corresponds to the age of the identified main mineralization period in the Xiazhuang ore field.

Minerals doi: 10.3390/min16050499

Authors: Haihui Bai Chaocheng Dai Lan Wang Long Xiang

The Chang 73 sub-member of the Yanchang Formation in Ordos Basin represents an important layer of uranium-rich source rocks. Exploring the genesis of phosphorus-bearing minerals and the mechanism of uranium enrichment are of great significance for deciphering basin evolution and uranium mineralization. The geochronology of phosphorus-bearing minerals and uranium enrichment mechanisms is investigated by using electron microscopy, laser ablation inductively coupled plasma mass spectrometry, U-Pb geochronology, and geochemical analysis. Results indicate the following: (1) The formation of phosphorus-bearing minerals can be divided into two independent stages. During the early sedimentary-diagenetic stage, influenced primarily by volcanic activity, volcanic ash tends to serve as the main source of both phosphorus and uranium. The coupling of high primary productivity and organic matter decomposition synergistically contributes to promoting apatite precipitation. During the Late Cretaceous hydrothermal diagenesis stage, the U-Pb isotopic systems of apatite were reset, yielding ages of 84 ± 2 Ma and 68 ± 1 Ma. This event also significantly modified the REE distribution patterns, resulting in flattened chondrite-normalized patterns and obvious LREE depletion. (2) Uranium enrichment in phosphorus-bearing minerals, which is closely associated with their formation, occurred through a two-stage process. During the sedimentary stage, U6+ was reduced to U4+ and incorporated into the mineral lattice via isomorphous substitution for Ca2+ or adsorbed onto mineral surfaces through complexation. Whereas the subsequent hydrothermal diagenesis stage led to further uranium enrichment as hydrothermal fluids introduced additional U6+, which was reduced to U4+ under anoxic conditions and incorporated into the apatite lattice via isomorphous substitution for Ca2+ or precipitated as discrete uranium minerals.

Minerals doi: 10.3390/min16050498

Authors: Zeynel Başıbüyük İlkay Kaydu Akbudak Meltem Gürbüz Hilal Dokuz Gökhan Ekincioğlu

Quartzites containing malachite–azurite mineralization identified in the Kırşehir region (Central Anatolia, Türkiye) are located within the Kırşehir Massif. This study aims to comprehensively characterize the mineralogical, petrographic, geochemical, and gemological properties of these quartzites and to evaluate their potential as ornamental and decorative stones. Due to their characteristic green and blue colors, malachite and azurite possess significant aesthetic value. Their occurrence within silica-rich and mechanically resistant quartzites enhances the visual appearance of the host rock while maintaining its structural integrity. Petrographic observations indicate that the quartzites exhibit a granoblastic texture composed of interlocking quartz crystals. Malachite–azurite mineralization is structurally controlled by NW–SE-trending fracture systems and occurs predominantly as fracture-filling and cavity-coating phases, indicating an epigenetic origin related to post-metamorphic fluid circulation. Geochemical analyses reveal that the samples are dominated by SiO2 (~95.33 wt.%), with CuO (~1.77 wt.%) and elevated Cu contents (3205 ppm) confirming the presence of copper carbonate mineralization. Although the high silica content contributes to overall mechanical strength, the relatively low Mohs hardness (3–4) and chemical sensitivity of malachite and azurite represent important limitations. Quantitative gemological measurements further indicate that quartz-rich domains exhibit high hardness values (up to ~907 HL), whereas malachite–azurite-bearing zones display significantly lower hardness (~735 HL) due to fracture-controlled heterogeneity and the presence of softer carbonate phases. Surface brightness measurements show moderate to high gloss values (~73–80 GU), with noticeable improvement following epoxy impregnation. These results demonstrate that while the material exhibits favorable optical properties, its mechanical performance is strongly influenced by mineralogical contrasts and structural discontinuities. Quartzites bearing malachite–azurite mineralization are therefore suitable primarily for decorative stones, ornamental objects, and small-scale jewelry applications rather than high-quality gemstones. The striking color contrast between azurite, malachite, and quartz enhances their visual appeal, and with appropriate stabilization techniques, their durability and economic value can be partially improved.

Minerals doi: 10.3390/min16050497

Authors: Yanwen Sun Guanyong Sun Zhisheng Shi Qunbo Yu Le Wang

Sulfate roasting is a critical pyrometallurgical pre-treatment for extracting Cu and Co from low-grade Cu–Co–Fe sulfide ores, yet conventional phase diagrams provide limited quantitative guidance for process control. To address this gap, a multicomponent/multiphase thermodynamic equilibrium model based on Gibbs free energy minimization was developed to systematically investigate the oxidative roasting behavior of single sulfides (Cu2S, CoS2, FeS2) and their ternary mixture, with respect to air supply, temperature, and total pressure. The model reveals that each sulfide follows distinct, temperature-dependent phase transformation pathways: Cu2S forms the acid-leachable product CuO·CuSO4 at temperatures ≤588 °C with a stoichiometric air supply of 11.9 mol, transitioning to oxides at ≥800 °C; CoS2 converts completely to CoSO4 below 727 °C and to CoO at higher temperatures; FeS2 yields sulfate phases at low temperatures and iron oxides above 654 °C. In the ternary Cu2S–CoS2–FeS2 system, competitive oxidation reactions produce refractory mixed oxides (CuO·Fe2O3, CoO·Fe2O3) whose formation is governed by temperature, air supply, and sulfide molar ratios. The results demonstrate that low-temperature roasting (≤641 °C) with precisely controlled air supply maximizes the formation of water-soluble sulfates, providing a quantitative thermodynamic basis for process optimization and enhanced recovery of Cu and Co from complex sulfide ores.

Minerals doi: 10.3390/min16050496

Authors: Sensen Guan Zhengwei He Jiaxian Wang Xin Chen Li He

The Liwu copper deposit, located on the western margin of the Yangtze Block, is a typical metamorphic-hosted polymetallic Cu deposit with significant deep exploration potential. To constrain its mineralization-forming processes and primary halo characteristics, this study focuses on the Heiniudong ore segment. Based on portable X-ray fluorescence (XRF) data obtained from drill cores and underground samples, a comprehensive geochemical analysis of 20 elements was conducted. Elemental background values and anomaly thresholds were determined using the iterative sigma (σ) elimination method. Pearson correlation analysis and hierarchical cluster analysis were applied to identify element associations, while the Grigorian zonation index method was employed to investigate axial zoning patterns of primary halos. The results demonstrate that Cu exhibits strong positive correlations with S, Fe, Ag, Cd, Sn, and Bi, indicating a medium- to high-temperature hydrothermal sulfide mineralization system. The primary halo displays well-defined vertical zonation, with Ba–Sr–Sb–As representing the front halo, Zn–Pb–Cu–Ag–Sn–Fe–Cd the near-ore halo, and Bi–Mo–W–Th the tail halo. A clear axial zonation sequence is established. The vertical variation in the geochemical ratio (As × Sr × Sb)/(Mo × Bi × W) exhibits a characteristic “low–high–low–high” pattern, reflecting the superposition of the front halo of a deeper concealed orebody with the tail halo of the upper known orebody under multistage hydrothermal remobilization and structural overprinting. Integrated with the coexistence of front halo and tail halo anomalies and strong alteration in drill hole WT03, the results indicate that the southwestern extension of WT03 along southwest-dipping ductile–brittle detachment structures represents the most promising deep exploration target.

Minerals doi: 10.3390/min16050495

Authors: Natalya S. Muravyeva Maria O. Anosova Tanya Furman

Mafic ultrapotassic volcanics (kamafugites, mafurites) are the youngest eruptives in the Bunyaruguru volcanic field, which is part of the Toro Ankole Province at the northernmost reach of the West Branch of the East African Rift Valley. We obtained new data using LA-ICP-MS on the trace element contents (rare earth, large ion lithophile, high field strength and compatible elements) in clinopyroxene phenocrysts from mafurite lava of the Bunyaruguru volcanic field. The clinopyroxenes are notable for their anomalously high zirconium contents (up to 800–1000 ppm), which is unusual in mafic silicate magmas but typical for clinopyroxenes from carbonatite lavas. This distinctive signature is not found in clinopyroxene in coeval mafic lavas from neighboring vents. Carbonate is also found in the Bunyaruguru volcanic rocks in the form of inclusions in high-Mg olivine phenocrysts, suggesting carbonated material exists in the source of kamafugite magmas. Carbonatites are widespread in the neighboring Fort Portal volcanic field, and we interpret the high-zirconium clinopyroxene as evidence for mixing of mafurite magmas with carbonatite melts.

Minerals doi: 10.3390/min16050494

Authors: Shuang Gao Jia-Hu Su Qianlin Wang Yong-Qin Ye Hao-Jie Cao Shuang Tan Sheng Wang Li Li Xiao-Yong Li Ping-Ning Ouyang

Granites associated with hydrothermal uranium deposits provide critical insights into the processes governing uranium enrichment and mobilization within the continental crust. The Yangjiaonao deposit, situated in the Lujing ore field within the Nanling Metallogenic Belt (South China), is a typical granite-related hydrothermal vein-type uranium deposit. This study presents integrated zircon U-Pb geochronology, whole-rock geochemistry, whole-rock Nd isotopes and zircon Hf isotopes for the medium-to-coarse-grained porphyritic biotite (MCB) and medium-to-fine-grained two-mica (MFM) granites from the Yangjiaonao (YJN) granitic pluton. Both units yielded Triassic ages (~235–233 Ma), indicating synchronous emplacement during the Early Mesozoic period. However, they exhibit distinct metallogenic fertilities rooted in their petrogenesis. MCB granite, derived from greywacke-dominated sources, shows typical S-type characteristics, whereas uranium remained mineralogically sequestered in refractory accessory phases (e.g., zircon, monazite) during differentiation, evidenced by high and stable Th/U ratios. Conversely, MFM granite represents L-type peraluminous systems originated from felsic, arkose-like protoliths. Advanced fractionation in the MFM system triggered significant Th-U decoupling, driving Th/U ratios down to ~0.5 and promoting uranium enrichment in the residual melt. This differentiation-driven concentration of ‘leachable’ uranium identifies MFM granite as the primary fertile source for the Yangjiaonao hydrothermal mineralization.

Minerals doi: 10.3390/min16050493

Authors: Jiao Li Yuanyuan Zhang Xincai You Wenjun He Yang Zou

The Lower Permian Fengcheng Formation (P1f) in the Mahu Sag, Junggar Basin, records an uncommon alkaline–lacustrine hybrid system where siliciclastic, volcaniclastic inputs, and endogenous carbonates jointly build strong reservoir heterogeneity. This study clarifies how depositional framework architecture and diagenetic evolution jointly control effective pore–throat connectivity and reservoir effectiveness. We examined 55 core samples from nine wells using X-ray diffraction (XRD), scanning electron microscopy (SEM), low-pressure N2 adsorption (LPNA), high-pressure mercury intrusion (HPMI), and nuclear magnetic resonance (NMR) T2 spectra, and identified five lithofacies: siliciclastic-dominated (SDF), volcaniclastic (VTF), mixed siliciclastic–carbonate (MSCF), carbonate-dominated (CDF), and alkaline mineral-rich (AMF). Reservoir quality is strongly lithofacies-dependent and cannot be inferred from pore volume alone. The SDF and CDF are both dominated by the >200 nm domain, but only the SDF preserves a coarse pore–throat framework that sustains effective flow; the MSCF is characterized by a stronger 10–50 nm contribution and a more tortuous network, and the VTF by enrichment of the 50–200 nm domain. In the SDF, quartz is preferentially associated with the >200 nm domain and dolomite with the 50–200 nm domain, consistent with coarse residual pores preserved by rigid grains and intercrystalline or dissolution-related pores, respectively. The AMF should be treated as two subtypes: the Na-borosilicate subtype shows high >200 nm volume but very high tortuosity, whereas the Na-carbonate subtype shows co-development of the 10–50 nm and >200 nm domains with lower threshold pressure and tortuosity, indicating better pore-body–throat matching and more favorable reservoir behavior. These findings provide a lithofacies-based framework for screening effective reservoir intervals in alkaline lacustrine hybrid systems.

Minerals doi: 10.3390/min16050492

Authors: Sergey V. Krivovichev Victor N. Yakovenchuk Olga F. Goychuk Anatoly V. Kasatkin Yakov A. Pakhomovsky Atali A. Agakhanov Alexey V. Chernyavsky

The Lovozero and Khibiny alkaline massifs (Kola Peninsula, Russian Arctic) are the prominent sources of REE minerals, with the Lovozero loparite deposit being the only currently active REE mine in Russia. A new ashcroftine-related mineral phase KA with the idealized chemical formula K6(Na4Ca)(Y8Ca3Mn)[Si28O68(OH)2](CO3)8F2·9H2O was found in the Khibiny alkaline massif. Its empirical formula determined by electron microprobe analysis is Na4.14K6.11Ca3.89Mn0.59Y6.10Ce0.08 Gd0.32Tb0.15Dy0.78Ho0.19Er0.35Tm0.15Yb0.12Lu0.06Si28C8O93.02F2.08·9H2O. The crystal structure was determined and refined by means of single-crystal X-ray diffraction analysis. The KA phase is tetragonal, I4/mmm, a = 24.1661(3), c = 17.5914(4) Å, V = 10,273.4(3) Å3. The crystal structure contains two Y sites. The Y1 site is [8]-coordinated and hosts more heavy REEs, whereas the Y2 site is predominantly [7]-coordinated and accumulates lighter REEs and Mn. The crystal structure is based upon the [Si28X70] nanotubes (X = O,OH) elongated along the c-axis and composed of corner-sharing SiX4 tetrahedra. The external diameter of the tubules is equal to ~19.54 Å, i.e., slightly less than 2 nm. The silicate nanotubes are running parallel to the c-axis and centered along the (00z) and (½½z) directions. The tubules are linked by walls of YOn polyhedra that also involve triangular CO3 groups. The K+, Na+, and Ca2+ cations, as well as H2O molecules, are located either inside or outside the tubules. The crystal-chemical formula of the KA phase can be written as {K6.14Na4.30Ca0.81}[Y5.88Ca3.12Dy0.88Mn2+0.60Gd0.32 Ho0.24Er0.24Tb0.16Tm0.16Er0.12Yb0.12Ce0.08Lu0.08](Mn3+0.09) [Si28O68.36(OH)1.65](CO3)8F2·8.97H2O, which agrees well with the idealized formula. According to the information-based complexity analysis, the KA phase has a very complex structure and belongs to less than 3.5% of the very complex minerals known today. The presence of silicate tubules is the key reason for the exceptional structural complexity of the phase. It is impossible to establish exact relations between the KA phase and ashcroftine-(Y) on the basis of the currently available data, since the last chemical analysis of the latter mineral was done in 1924. Therefore, the mineralogical identity of ashcroftine-(Y) is currently an unresolved problem. The silicate tubule in the KA phase is topologically related to the Linde zeolite A (the LTA zeolite framework) and can be produced from the latter by a series of topological operations. The KA phase forms a homological row with caysichite-(Y) and miyawakiite-(Y), along which the Si content is increasing, and silicate chains in caysichite-(Y) transform into silicate tubules in miyawakiite-(Y) and into silicate nanotubules in the KA phase. Indeed, the M:Si:C ratio (where M = Y, REEs, Ca, Mn, Fe) changes from 1:1:0.75 for caysichite-(Y) through 0.75:1:0.5 for miyawakiite-(Y) to 0.43:1:0.29 for ashcroftine-(Y) (and KA). The increasing role of silica along the row results in the formation of zeolite-derived porous one-dimensional units. The KA phase possesses two important crystal chemical properties that distinguish it from other minerals known to date: it hosts a variety of REEs and is based upon nanoscale zeolite-like silicate units. The KA phase, ashcroftine-(Y), caysichite-(Y), and miyawakiite-(Y) have never been prepared under laboratory conditions. The mineralogical occurrence of the KA phase in the Khibiny massif points out to its secondary origin, i.e., its formation under relatively soft, low-temperature hydrothermal conditions. Thus, the discovery of the KA phase in nature may provide important hints toward its synthesis in the laboratory by means of a soft-chemistry approach.

Minerals doi: 10.3390/min16050491

Authors: Peng Li Yang Sun Wenwen Meng Zhe Hu Zhengcan Li Qilin Liu Yushuang Li

Flotation tailings, the primary solid waste generated during gold extraction, may pose issues such as land occupation, environmental pollution, and geological hazards in open-pit mining areas. This study systematically investigated the environmental characteristics, long-term pollutant release patterns, and migration risks associated with flotation tailings by taking a specific backfill project as a case study and employing short-term leaching tests, long-term column leaching experiments, and multi-model numerical simulations. Short-term leaching tests indicated that tailings leachate exhibited weak alkalinity (pH 8.21−8.45) with low pollutant leaching concentrations, meeting the fundamental requirements for open-pit backfilling. Notably, leaching characteristics varied significantly among tailings from different sources, and an extended storage duration enhanced chemical stability. Long-term leaching tests identified nine characteristic pollutants, including fluoride and sulfate, with their release patterns categorized into three types: continuous slow release, initial rapid leaching, and delayed/complex release. Furthermore, simulation results from the HYDRUS and MODFLOW/MT3DMS models indicated that the maximum predicted concentrations of characteristic pollutants in the surrounding soil and groundwater will remain at low levels for 50 years post-backfilling. The site’s “micro-to-weakly permeable” strata exhibited significant pollutant retention capabilities. Based on these experimental and simulation results, a three-tier risk management system—”source control, process monitoring, and end-point surveillance”, was developed to provide technical support for the long-term environmental safety of the flotation tailings backfill project. This study revealed the environmental risk characteristics associated with the storage of flotation tailings, including land occupation, environmental pollution, and the potential for geological hazards in open pits. Furthermore, the leaching characteristics, long-term release patterns, and migration mechanisms of tailings used to backfill open pits have been elucidated, providing theoretical references and practical guidance for similar solid waste resource recovery and backfilling projects.

Minerals doi: 10.3390/min16050490

Authors: Chao Yu Chuan Zhang Tian Han Xingjian Cao Yingjia Zhao Yongtai Pan

Efficient calibration of discrete element meso-parameters is essential for reliable rock fragmentation modeling. This study focuses on green sandstone, combining uniaxial compression tests with PFC3D simulations to establish an XGBoost–stepwise regression framework for macro–meso-parameter calibration of the parallel bond model. XGBoost was used to identify the dominant meso-parameters governing peak strength, elastic modulus, and Poisson’s ratio, and stepwise regression was applied to construct explicit nonlinear mapping equations. Peak strength is mainly controlled by shear strength τcp and normal strength σcp, while elastic modulus and Poisson’s ratio are primarily influenced by bond modulus Ecp and stiffness ratio kp*. Introducing quadratic and interaction terms improved model fit, with adjusted R2 increasing by 27.5% and 11.2%, respectively. The calibrated parameters reproduced laboratory mechanical indices with errors of 0.09%–3.745% and showed good agreement with the observed shear–brittle failure pattern. Based on the calibrated model, a representative impact-fragmentation simulation further revealed staged conversion of input energy into fracture-related energy during crack initiation, propagation, and through-failure. The proposed framework improves the efficiency and interpretability of PBM parameter calibration and supports DEM-based analysis of rock fragmentation and energy evolution.

Minerals doi: 10.3390/min16050489

Authors: Yunlou Qian Jing Wang Xiaolong Huang Chunsheng Lan Zhen Wang Yongde Zhang

To solve the problem of mechanical entrainment and slime coating of fine sericite and chlorite hindering the flotation separation of gold-bearing pyrite in low-grade gold ores, ethylenediamine-N,N’-disuccinic acid (EDDS) was innovatively used as a selective and eco-friendly depressant. A systematic set of tests, including micro-flotation, artificial mixed mineral flotation, zeta potential measurement, adsorption capacity test, solution chemistry analysis and X-ray photoelectron spectroscopy (XPS) characterization, was conducted to explore its flotation performance and action mechanism. The results showed that pH 8 and 200 mg/L EDDS were the optimal conditions under which EDDS reduced the recoveries of sericite and chlorite to ~20% and ~15%, respectively, while restoring pyrite recovery to ~80% with a notable upgrade in concentrate grade. EDDS exhibited strong chemical adsorption on sericite and chlorite via chelating their active Al/Mg sites, significantly enhancing their hydrophilicity. In contrast, it only undergoes weak physical adsorption on pyrite, with negligible observed influence on its hydrophobicity and the adsorption of (sodium butyl xanthate) SBX. At pH 8, EDDS mainly existed as HEDDS3− (~90%), whose triple negative charge strengthened electrostatic interaction with positively charged gangue surfaces, boosting selective adsorption. This study confirms EDDS as a highly efficient depressant for pyrite–sericite/chlorite flotation under pure mineral and artificial mixed mineral conditions. Since the present study is based on pure minerals and artificial mixtures, further validation using real ore samples is still required before practical industrial application. This research expands the application of EDDS in mineral processing and provides a novel eco-friendly technical approach for the laboratory-scale separation of fine gold-bearing pyrite from low-grade gold ores with high clay gangue content.

Minerals doi: 10.3390/min16050488

Authors: Yan Huo Feng Ding Yuzhu Luo Yuhang Fan Junyi Yao

The Shizhushan super-large wollastonite deposit, situated in the western segment of the Pingle Depression within the Qin–Hang metallogenic belt, represents the largest known wollastonite deposit in the world. The deposit formed mainly through contact metamorphism, followed by contact metasomatism. The ore bodies are hosted in the carbonate rocks of the Middle Permian Maokou Formation. The deposit consists of 12 ore bodies, which are controlled by the strata and occur as layered and lenticular bodies. The mineralization process is divided into an early contact metamorphism period (wollastonite–calcite and wollastonite–calcite–quartz stages) and later hydrothermal metasomatism period (wollastonite–garnet stage). This study examined the fluid inclusions in the contact metamorphic wollastonite ore bodies in this deposit. The results show that the types of inclusions are mainly liquid-rich two-phase inclusions, pure liquid-phase inclusions, and pure vapor-phase inclusions, with a small number of CO2-H2O three-phase inclusions. The homogenization temperature ranges of the different stages are 409.50~260.10 °C for the wollastonite–calcite stage and 283.60~132.40 °C for the wollastonite–calcite–quartz stage. The temperature and salinity of ore-forming fluids show an evolution from medium–high temperature and medium–low salinity to low temperature and low salinity. The minimum ore-forming depth of the deposit is 0.79~4.74 km, indicating a shallow, low-pressure environment. Based on the macrogeological characteristics, the tectonic fractures formed during the contact metamorphic period triggered decompression boiling of the ore-forming fluids, which led to the precipitation of mineralization materials and the subsequent mineralization. Based on a comprehensive analysis of the metallogenic geological setting, material sources, metallogenic process, and structural control factors, a trinity metallogenic model of the “carbonate rock + pluton + semi-open structural system” is established for the Shizhushan wollastonite deposit.

Minerals doi: 10.3390/min16050487

Authors: Jimin Cai Jiahui Li Wenbin Cheng Wenli Xu Bo Li Xinghai Lang Cuihua Chen Yiwei Peng Lei Peng

The Sichuan–Yunnan–Guizhou (SYG) metallogenic belt hosts numerous carbonate-hosted Pb-Zn deposits, yet the genesis of lead-dominated deposits remains poorly understood. This study investigates the Wuyi Pb deposit, a representative lead-dominated deposit in the SYG belt, through an integrated approach including field geology, fluid inclusion microthermometry, and C-H-O-S-Pb isotope geochemistry. The ore bodies occur as stratoid and lenticular lenses within the dolomitic limestone of the Ordovician Dajing Formation, controlled by both lithology and the Wuyi composite fold structure. Mineralization is divided into two stages: (I) pyrite–sphalerite–dolomite–calcite, and (II) galena–calcite–quartz–anhydrite. Fluid inclusion studies reveal that the ore-forming fluids are of the NaCl-H2O system, characterized by moderate-low temperatures (Stage II, average 201 °C) and moderate-low salinities (Stage II, average 5.35 wt% NaCl eq.). Hydrogen and oxygen isotopes (δD = −100.97 to −76.33‰; δ18Ofluid = 7.09 to 12.10‰) indicate that the ore-forming fluids were predominantly meteoric in origin. Carbon isotopes (δ13C = −4.45 to 0.75‰) suggest that carbon was derived mainly from dissolution of the host carbonate rocks. Sulfur isotopes show a significant shift from Stage I (δ34S = −12.40 to −3.00‰) to Stage II (δ34S = −8.20 to −0.10‰ for sulfides; 25.00–29.40‰ for sulfates), indicating a transition from bacterial sulfate reduction (BSR) to thermochemical sulfate reduction (TSR) as the dominant sulfur reduction mechanism, with sulfur derived from Ordovician seawater sulfate. Lead isotopes (206Pb/204Pb = 18.10–25.37, 207Pb/204Pb = 15.50–21.72, 208Pb/204Pb = 38.29–53.90; μ = 9.30–21.05) demonstrate that metals were sourced predominantly from the Proterozoic basement rocks (Kunyang and Huili groups). Integration of geological, geochemical, and isotopic evidence indicates that the Wuyi Pb deposit formed during the Indosinian post-collisional intracontinental orogeny (ca. 230–200 Ma), when topography-driven meteoric water circulation extracted metals from the Precambrian basement and sulfur from Ordovician strata. Metal precipitation under the reduced sulfur model is caused by decreases in temperature and pressure and the water–rock reaction. This study establishes the Wuyi deposit as an MVT Pb deposit and provides a genetic model for lead-dominated mineralization in the SYG belt.

Minerals doi: 10.3390/min16050486

Authors: Stavros Savvas Triantafyllidis

Volcanogenic Massive Sulfides (VMS) are considered major base (Cu-Zn±Pb) and precious metal (Au and Ag) sources with paramount contribution in the development and evolution of mankind through the ages. They are characterized by variable ore mineralogy and geochemistry, largely attributed to the variety in the geotectonic regime of formation (both divergent and convergent margins) and the variability in the host lithologies. Several VMS types are distinguished depending on the type of volcanism and host-rock lithology. The lens-shaped-to-stratiform bodies composed of fine-grained sulfides, usually accounting for more than 60% of the rock mass, have been exploited since prehistoric times. Recent studies reveal that VMS continue to be formed in deep marine settings and along plate margins on the ocean floor. Besides base and precious metals, nowadays, VMS are considered significant sources of critical and strategic metals, such as Co, Ni, Ga, Ge, In, Bi, As, Sb, Se, Mo, Cd, Sn, Hg, Tl and Bi, particularly after extensive research of the ocean floors in the years following World War II (WWII). Since the late 1970s, the potential of VMS has been further enhanced after the successful deep-sea mining (DSM) pilot tests, with the pipeline-lift mining system considered the most suitable for seabed massive sulfide (SMS) recovery.

Minerals doi: 10.3390/min16050485

Authors: Jin-Shuai Zhang Hao-Cheng Yu Guo-Long Yan Ming Ma Tao Cui Ya-Peng Li Lian-Yuan Qin Chun-Ting Xu

Whether the genesis of gold deposits in the Northeastern Jiaolai Basin is consistent with that in the Northwestern Jiaodong area remains controversial. This study presents in situ Rb-Sr dating of sericite, along with in situ trace element and sulfur isotope analyses of pyrite in the Longkou gold deposit. The sericite Rb-Sr inverse isochron yields an age of 120.9 ± 2.4 Ma, indicating that gold mineralization occurred in the Early Cretaceous. Two generations of pyrite, Py1 and Py2, were identified. Py1 is anhedral and hosted in relatively low-grade, weakly altered marble wall rock. Py2 is euhedral to subhedral and hosted in relatively high-grade, strongly altered marble ore. The δ34S value of Py1 is 7.38‰, whereas that of Py2 is 6.79‰. The decrease in δ34S values from Py1 to Py2 reflects an increase in the oxygen fugacity of the ore-forming system. These features suggest that fluid–rock interaction led to an increase in oxygen fugacity, thereby triggering gold precipitation. The mineralization age and precipitation mechanism of the Longkou gold deposit are consistent with those of the Northwestern Jiaodong area. The Longkou gold deposit is best classified as a Jiaodong-type gold deposit.

Minerals doi: 10.3390/min16050484

Authors: Ling Zhao Zhenkai Huang Xin Sui Xianda Sun Chengwu Xu Hongyu Wang Yuanjing Huang Jie Zhou Ge Yang

Differential enrichment of shale oil hydrocarbon fractions exerts a fundamental control on the spatial distribution of “sweet spots” and the efficiency of unconventional resource recovery. This study investigates the continental shales of the Upper Es4 Member in the Dongying Sag, Bohai Bay Basin, through an integrated analytical framework combining Laser Scanning Confocal Microscopy (LSCM), Scanning Electron Microscopy (SEM), and high-pressure mercury intrusion. By moving beyond qualitative observations, we characterize the micro-scale partitioning of light and heavy fractions and establish a deterministic hierarchy of controlling factors. Our results indicate the following. (1) Mineral composition functions as a “primary geochemical filter,” where carbonate minerals exhibit a preferential adsorption affinity for light fractions (≤ C18), while clay minerals facilitate the selective retention of heavy components (> C18). (2) Pore–throat architecture acts as a “secondary mobility modulator.” A statistically significant linear correlation (R2 = 0.72, p < 0.05) was identified between mean pore diameter and the light-to-heavy fluorescence ratio, suggesting that interconnected macropores in carbonate laminae provide low-resistance conduits for light oil accumulation, whereas isolated mesopores in argillaceous matrices promote heavy-component sequestration. (3) Thermal maturity (Ro) drives a progressive shift in the light-to-heavy ratio, enhancing oil fluidity and regulating the transition from adsorption-dominated to migration-dominated enrichment. This study clarifies the lithofacies-dependent coupling mechanisms between mineral diagenesis and pore-scale fractionation, providing a semi-quantitative conceptual model for shale oil sweet-spot prediction in complex lacustrine basins.

Minerals doi: 10.3390/min16050483

Authors: Bruna Karine Correa Nogueira Jean-Michel Lafon João Marinho Milhomem Neto Fábio dos Santos Pereira Regina Celia dos Santos Silva Elton Luiz Dantas

The Arco Verde Complex, exposed in the Serra do Inajá region of the Rio Maria Domain (Carajás Province, Amazonian Craton), represents one of the oldest TTG granitoid association of the province (3.00–2.92 Ga). While TTG magmatism is well constrained in the northern domain, its southern sector lacks precise geochronological data. This study integrates petrographic, geochemical, U–Pb zircon geochronology, and Nd–Hf isotopes to constrain the age, source, and crustal significance of these granitoids. Uranium–Pb zircon dating of two granodiorites yielded ages of 2979 ± 8 and 2979 ± 11 Ma, extending the 2.98 Ga TTG magmatic episode to the southern sector of the Rio Maria Domain. Geochemical data indicate dominant tonalites formed by partial melting of a similar mafic source at different crustal depths, whereas subordinate granodioritic and monzogranitic rocks show transitional TTG affinities. These features indicate coeval mafic and felsic crust rapidly reworked after formation. Hf and Nd model ages of 3.0–3.2 Ga, with positive εHf–Nd at 2.98 Ga, reinforce the Early Mesoarchean as the main crustal growth period in the province. In addition, we propose that the differentiation of the depleted mantle (DM) beneath the Carajás Province may have initiated around 3.8 Ga.

Minerals doi: 10.3390/min16050482

Authors: Walid Ahmed Makled Ali Ismail Al-Juboury Asmaa Kamel Ali Ismail Elshorbagy Mohamed Mahmoud El El Garhy Nagham Omar Thomas Gentzis Nasir Alarifi Fathy Abdalla

The Paleozoic rocks of Egypt’s Western Desert remain under limited exploration. The complex subsurface structures create stratigraphic challenges that hinder petroleum exploration. This study evaluates the application of organic microfacies as a stratigraphic tool to address their exploration challenges and enhance our understanding of environmental changes. The Faghur-1X well penetrated the Devonian Zeitoun Formation, yielding numerous successful core recoveries. Seven of these cores were analyzed to delineate the lithological and stratigraphical variations. Three distinct organic microfacies types were identified within the studied section. These organic microfacies reveal significant paleoenvironmental shifts that represent key correlative events within the Devonian. These include liptinite-dominated–medium-organic-density distal facies (A) (cores 19-A, 18-B, and 17-A); vitrinite-dominated–high-organic-density proximal facies (B) (cores 14-A and 20-A/Band 20-C); and ironstone-rich and low-organic-density condensed section/distal facies (cores 18-A, 16-A, 15-A, and 15-B). These organic facies exhibit unique characteristics resulting from the interaction of organic matter with the rock matrix and environmental processes. These unique characteristics facilitate intra-basinal stratigraphic correlation. While commonly applied to hydrocarbon source rock evaluation, this study investigates the stratigraphic significance of organic microfacies for resolving subsurface geological problems.

Minerals doi: 10.3390/min16050481

Authors: Mei Zang Qianru Xiao Xin Li Yujun Shi Ling Xing Pengbing Li Peisong Fang Pingping Zhu Tedi Fu Jingnan Ye Yongming Guo Zulihar Balatibak

Baixintan is a magmatic Ni–Cu sulfide deposit discovered in the central Tuwu–Yandong porphyry Cu belt of the Eastern Tianshan Orogen (ETO) of NW China in 2016. It is in close proximity (~5 km) to the Tuwu Cu deposit, the largest Carboniferous porphyry Cu deposit (~336 Ma) in Xinjiang. The Baixintan Ni–Cu ore is characterized by a high Cu/Ni ratio, but the reason for it remains unclear. To resolve this question, we present petrographic, geochronological, whole-rock geochemical, and S, Pb, Cu, and Lu–Hf isotopic data. Ore-related hornblende olivine websterite (HOW) and hornblende olivine gabbro (HOG) were emplaced at 296.6 ± 1.1 Ma and 289.7 ± 1.2 Ma, respectively, which were formed in an Early Permian post-collisional extensional setting. Whole-rock Pb and zircon Lu–Hf isotopes suggest that the parental magmas were predominantly mantle-derived. The Baixintan HOW and HOG contain abundant hornblende and are enriched in LILEs and LREEs but depleted in HFSEs, suggesting subduction-related metasomatism in their magma source. The sulfide (chalcopyrite, pyrrhotite, and pentlandite) δ34S values cluster around 0‰ (–0.13 to 0.11, n = 11), and the chalcopyrite has uniformly negative but variable δ65Cu values (–0.96 to –0.13, n = 6), which suggest that the ore-forming materials were mainly derived from the subduction-metasomatized mantle. Olivine Ni contents are significantly lower than those crystallized under sulfide-unsaturated conditions, implying that olivine fractional crystallization was an important trigger for sulfide melt segregation at Baixintan. Baixintan is the only known magmatic Ni–Cu sulfide deposit in the ETO that shares a Cu-preconcentrated, metasomatized mantle source with a giant porphyry Cu system. Copper pre-enrichment in the magma source may be the main factor for the relatively high Cu/Ni ratio observed in the Baixintan deposit.

Minerals doi: 10.3390/min16050480

Authors: Unzile Yenial-Arslan Elizaveta Forbes

The induced polarisation (IP) technique is a geophysical method used to measure chargeability and resistivity, providing crucial insights into subsurface geological structures. Traditionally, IP measurements have been instrumental in exploring disseminated sulphide deposits, leveraging the strong polarisation response of metallic particles. It provides valuable insights about rock mineralisation, matrix composition, and formation polarizability by analysing electrical parameters. However, their potential to predict metallurgical performance remains largely unexplored. This study evaluates whether IP parameters—chargeability and resistivity—can serve as geometallurgical indicators for copper sulphide ores. The evaluation integrates IP measurements with mineralogical and flotation data. Artificial pyrite–sand mixtures and five real ore samples from Mount Isa were analysed using the sample core IP tester and mineral liberation analysis, followed by collectorless flotation tests. Statistical analysis demonstrated a strong correlation between resistivity and chalcopyrite recovery (R2 = 0.90, p = 0.99), as well as a moderate correlation between chargeability and chalcopyrite selectivity (R2 = 0.72, p = 0.93). These findings demonstrate that IP captures key textural and electrochemical features governing flotation behaviour, including pyrite abundance, mineral liberation, and galvanic interactions. The results highlight IP as a promising rapid-assessment tool for identifying ore variability and forecasting flotation response, with potential integration into geometallurgical models and mine-to-mill optimisation. Further validation across broader ore domains is recommended to refine the predictive capability of IP-based indicators.

Minerals doi: 10.3390/min16050477

Authors: Ángel Brime Barrios Alberto Alcolea Ana Méndez Roberto Rodríguez-Pacheco

Mining and metallurgical residues represent one of the largest untapped secondary raw-material resources in Europe; however, their critical raw material (CRM) potential remains insufficiently quantified. This study applies a comprehensive mineralogical, geochemical, and geostatistical framework to evaluate nine distinct waste types from the Cartagena–La Unión Mining District (SE Spain), a historically exploited polymetallic system. A total of 79 samples were analysed using X-ray diffraction, wavelength-dispersive X-ray fluorescence, and advanced multivariate statistical techniques (correlation analysis, principal component analysis and hierarchical clustering) to identify geochemical associations controlling CRM distribution. The results reveal strong geochemical heterogeneity, with systematic enrichment in Co, Ni, Cu, Ga, Nb, and rare-earth proxies. Three dominant geochemical controls were identified: (i) a lithogenic silicate association governing Al–Si–Ti–Nb patterns, (ii) a sulphide-derived metalliferous association characterized by Cu–As–Sb, and (iii) an oxidation–adsorption association responsible for Ga–Y affinity. Several CRM concentrations approach or exceed typical global ore grades for secondary resources, particularly in flotation-derived and oxidation-rich residues. Geostatistical modelling confirms spatially coherent CRM hotspots, with base-metal enrichment linked to sulphide relics and Ga–Nb–Y controlled by Fe–Mn oxyhydroxides. Environmental assessment indicates potential metal mobility under acidic conditions, while also highlighting significant remediation benefits associated with residue reprocessing. Taken together, this study provides a robust and reproducible methodology for CRM assessment in legacy mining wastes and identifies priority residue types within the district with the highest strategic recovery potential.

Minerals doi: 10.3390/min16050479

Authors: Vinicius Sales Graciela Racolte Lais Souza Alysson Aires Julia Lorenz Reginaldo Silva Luiza da Silva Rafael Dias Diego Mariani Ademir Marques Daniel Zanotta Delano Ibanez Luiz Gonzaga Mauricio Veronez

Accurate quantification of mineralogical composition in carbonate rocks is essential for reservoir characterization in the oil industry, directly influencing petrophysical properties such as porosity and permeability. However, traditional methods such as X-ray diffraction (XRD) are destructive and provide limited spatial sampling. The aim of this study was to develop and validate a workflow for the continuous quantification of calcite and dolomite in drill cores from the Brazilian pre-salt oil province by integrating short-wave infrared (SWIR) hyperspectral imaging (HSI) and Machine-Learning algorithms. A total of 80 m of cores were evaluated using 170 XRD-validated samples to calibrate linear, nonlinear, and ensemble models. The results showed that the combination of Multiplicative Scatter Correction (MSC) preprocessing with Multilayer Perceptron (MLP) and Support Vector Regression (SVR) achieved the best performance, reaching an R2 of 0.84. Explainable Artificial Intelligence (SHAP) confirmed the relevance of diagnostic bands between 2330 and 2360 nm, improving geological interpretability of the predictions. The proposed methodology provides a non-destructive and high-resolution alternative for mineralogical profiling, supporting the evaluation of complex reservoirs and decision-making in the oil and gas industry. Although the workflow was validated using a specific pre-salt dataset, future studies should assess its transferability to other carbonate reservoirs and broader geological settings.

Minerals doi: 10.3390/min16050478

Authors: Qi Zhang Huanhuan Yang She Li Qin Wang Yujie Dong Hongwei Li Chao Yang Changyun Gan Rongkun Zhang Xuelian Fu Xinjuan Liang

The Duolong porphyry copper–gold district, located in the northwestern segment of the Bangongco–Nujiang metallogenic belt on the southern margin of the South Qiangtang terrane (Tibet), hosts typical porphyry-style Cu-Au mineralization with well-defined alteration zoning from potassic through chlorite–sericite to propylitic assemblages. Based on integrated in situ major/trace element and sulfur isotope analyses of pyrite and chalcopyrite from different alteration zones, we identify two discrete episodes of magmatic-hydrothermal activity that exerted distinct controls on metal endowment. Sulfur isotope signatures define a systematic evolution from the earliest, high-temperature potassic stage (δ³⁴S: Py-Ⅰ –3.70 to –1.16‰, mean –2.14‰; Cp-Ⅰ –4.92 to –0.90‰, mean –2.54‰) through propylitic alteration (Py-Ⅱ: 1.20–5.16‰, mean 3.06‰) to the later chlorite–sericite stage (Py-Ⅲ: –2.00 to 1.86‰, mean 0.06‰; Cp-Ⅱ: –2.50 to 0.58‰, mean –0.77‰), tracking progressive fluid cooling and changing fluid sources. Trace element systematics further discriminate these episodes: sulfides from potassic and chlorite–sericite zones are enriched in trace elements, whereas propylitic pyrite is depleted, with potassic pyrite recording the highest Cu concentrations (559–7256 ppm, mean 2302 ppm) and chlorite–sericite pyrite containing the lowest Au contents (0.01–0.59 ppm, mean 0.10 ppm). Gold mineralization occurs as native gold exsolved from chalcopyrite, and the markedly low Au concentrations in chlorite–sericite pyrite (0.01–0.59 ppm, mean 0.10 ppm) demonstrate that gold exsolution was largely completed during the first, high-temperature magmatic-hydrothermal stage. Collectively, these results establish a detailed geochemical framework linking sulfide composition to specific hydrothermal stages, providing new constraints on the processes of porphyry copper–gold mineralization in a collisional setting.

Minerals doi: 10.3390/min16050476

Authors: Jacopo Seccatore Alex Contreras Tatiane Marin

Comminution is the most energy-intensive stage in mineral processing and a major source of indirect greenhouse gas (GHG) emissions in mining. This study evaluates the impact of Ultra-High-Intensity Blasting (UHIB) on downstream comminution energy demand and associated GHG emissions under conditions representative of large-scale Chilean mining. Fragmentation from conventional blasting and UHIB was simulated using JKSimBlast, and the resulting particle size distributions were used as input for four comminution circuit configurations modeled in JKSimMet. Two ore hardness scenarios were analyzed: hard ore (Bond Work Index, BWI = 19 kWh/t) and soft ore (BWI = 11 kWh/t). Power draw of crushers and mills was used to estimate specific energy consumption and GHG emissions based on the Chilean electrical system emission factor. Results show that UHIB enables significant reductions in comminution energy demand, reaching approximately 18% for hard ore and over 30% for soft ore. These reductions are primarily associated with circuit simplification, including the removal of energy-intensive stages such as primary crushing and SAG milling. The results demonstrate that improved fragmentation can reduce downstream energy demand and carbon intensity, highlighting UHIB as an effective mine-to-mill strategy for energy efficiency and emission reduction.

Minerals doi: 10.3390/min16050475

Authors: Rowfi Khan Randy Vander Wal

The scalable and sustainable production of graphene remains a significant challenge due to the high cost, complex processing, and environmental impact associated with fossil-derived graphite precursors. In this work, we report a biorenewable pathway for producing graphitic carbon from industrial hemp biomass, yielding a plant-derived material called CleanGraphene. This approach provides a renewable and potentially scalable alternative to petroleum- and coal-based graphene production while maintaining competitive structural and electrical performance. CleanGraphene samples are systematically characterized using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) to evaluate crystallographic order, layer stacking, defect density, surface chemistry, and thermal stability. The results show that optimized CleanGraphene materials consist of multilayer graphene-like platelets with compact interlayer spacing (d(002) ≈ 3.36–3.37 Å), extended crystallite coherence lengths (Lc up to ~75 nm), large in-plane sp2 domains (La exceeding ~200 nm), and relatively low defect densities, indicating well-developed graphitic ordering. Electrical conductivity measurements using a binder-free pelletization method and four-point probe analysis demonstrate that the highest quality CleanGraphene samples achieve conductivities of (8.4–8.6) × 104 S m−1, surpassing leading commercial graphene benchmarks measured under identical conditions. Structure–property correlations confirm that electrical performance is governed primarily by crystallite coherence, defect density, and interlayer stacking order, while surface oxygen content plays a secondary role within an ordered graphitic framework. All CleanGraphene samples exhibit excellent thermal stability, retaining more than 95% mass up to ~800–900 °C under an inert atmosphere. Collectively, these findings establish quantitative quality benchmarks for hemp-derived graphene and demonstrate that biomass-based graphene can achieve electrical and thermal performance comparable to, and in some cases exceeding, conventional commercial products. This work highlights industrial hemp as a promising renewable precursor for the scalable production of high-performance graphitic nanomaterials for electrically and thermally conductive composite applications.

Minerals doi: 10.3390/min16050474

Authors: Jiajie Liu Zong Guo Chaozhen Zheng Sanping Liu Haibei Wang

To address the difficulty of efficiently removing calcium impurities from the manganese sulfate stripping solution obtained during the recycling of spent lithium batteries, this work proposed a binary synergistic extraction system. Quantum chemical calculations were used to screen the optimal combination (2A + 2B). The binding energy indicated the molecules combined with calcium are relatively more stable. Experimental optimization determined the optimal conditions as follows: 50 vol% of A, 25 vol% of B, saponification rate 60%, phase ratio (O/A) 2.5:1, and pH 6.0. In continuous extraction tank experiments, the calcium concentration decreased from 681 mg/L to 5 mg/L after a seven-stage counter-current extraction, with an extraction efficiency of about 99.3%. Infrared spectroscopy confirmed that the P=O double bond was the key functional group. This study provides an efficient and feasible technological pathway for the preparation of battery-grade manganese sulfate.

Minerals doi: 10.3390/min16050472

Authors: Theophilus Amos-Judge Giang Nguyen George Abaka-Wood Richmond Asamoah

The flotation performance of a low-grade, polymetallic copper ore, dominated by chalcocite and transitional copper phases, was investigated to assess the interplay between collector chemistry, gangue mineralogy, and entrainment. QEMSCAN analysis identified chalcocite as the main copper host (62%), with minor covellite and bornite, and gangue, predominantly quartz (94%), with variable muscovite (up to 50%). Chalcocite was moderately liberated (100–200 µm), while secondary copper phases showed low exposure and strong gangue association, challenging selective recovery. Baseline flotation with potassium amyl xanthate (PAX) and sodium isobutyl xanthate (SIBX) across pH and dosage ranges showed that PAX yielded higher copper recovery but lower grade, indicating unselective gangue entrainment; SIBX offered lower recovery but higher grade, reflecting superior selectivity. Controlled muscovite doping experiments (10–50 wt.%) were employed to decouple gangue-driven selectivity loss from collector-specific interactions. Results indicate a collector-dependent sensitivity to gangue loading: PAX exhibited a pronounced decline in both copper recovery (82%–67%) and grade under increasing muscovite content, with water recovery rising by approximately 32%, whereas SIBX showed more gradual performance degradation and lower entrainment (15% increase in water recovery), highlighting its resilience in gangue-rich systems. UV-Vis and zeta potential (electrokinetic) measurements confirmed stronger PAX adsorption, consistent with its longer hydrocarbon chain, while flotation trends demonstrated a shift from true flotation-dominated recovery to entrainment-dominated regimes at high muscovite levels, particularly for PAX. This framework links mineralogy, collector chemistry, and gangue entrainment, guiding optimization of circuits for ores like Mt. Gunson while enhancing critical metal recovery, including cobalt.

Minerals doi: 10.3390/min16050473

Authors: Luís Marcelo Tavares Gabriel K. P. Barrios Luciana P. Alves Elias F. de Castro José N. S. Silva

The identification of ore types that share similar geological characteristics and metallurgical performance in a deposit is of great relevance in mine planning. In the case of a low-grade iron ore from Brazil, called itabirite, ore types are usually classified as compact and friable, in addition to canga. As itabirites become more widely exploited, friable itabirites have become scarcer, leaving more competent ores to be processed. The work investigates the response of 19 iron ore samples from the Serra do Sapo deposit (Minas Gerais, Brazil), through a variety of bench-scale comminution tests. In the context of crushing (>25 mm), one subtype of compact itabirite, called supercompact, presented substantially higher resistance to fragmentation than those of compact itabirite and canga. In the context of grinding (<19 mm), an inversion occurs, with canga presenting the highest resistance to comminution, followed by the itabirites (friable, compact, and supercompact), nearly indistinctively. This demonstrates that the relative competence of iron ores to withstand comminution in the studied mineral deposits varies significantly as a function of particle size and, therefore, size reduction stage. Finally, grouping of the samples using cluster analysis demonstrated the relevance of discrimination between compact and supercompact itabirites, besides canga, with supercompact itabirite having a greater affinity to canga than with its compact counterpart. This shows the importance of further discriminating itabirites, particularly in the context of comminution at coarser sizes.

Minerals doi: 10.3390/min16050471

Authors: Wenyi Wu Mingsen Fan Pei Ni Junyi Pan Yihan Lin Zhe Chi Junying Ding

Sandstone-type uranium deposits represent one of the most significant uranium deposit types in China, predominantly hosted in Meso-Cenozoic sedimentary basins in the northern part of the country. Due to characteristics such as deep burial of orebodies, fine grain size of ores, and strong heterogeneity, traditional geological logging methods have limitations in rapidly and accurately identifying alteration minerals and mineralization indicator information. Core spectral technology (wavelength range approximately 400–2500 nm), particularly short-wave infrared spectroscopy (SWIR, 1300–2500 nm), enables rapid, non-destructive, and quantitative extraction of alteration mineral information from drill cores. This provides robust technical support for reconstructing metallogenic environments, delineating oxidation–reduction zones, and prospecting and prediction in sandstone-type uranium deposits. This review systematically examines the spectral absorption characteristics and geological significance of key alteration minerals (e.g., clay minerals, carbonate minerals, iron oxides, and hydrocarbon substances) in sandstone-type uranium deposits. It elaborates on the current application status of core spectral technology in sandstone-type uranium exploration within typical basins in northern China, such as the Ordos, Songliao, Erlian, and Qaidam Basins. These applications include alteration mineral mapping, oxidation–reduction zone delineation, and metallogenic fluid tracing. Due to the unique characteristics of host rock lithology, alteration mineral assemblages, and fluid properties in sandstone-type uranium deposits, the application of this technology also faces certain challenges, such as difficulties in spectral interpretation and insufficient accuracy in quantitative inversion. Integrating this technique with multiple methods, including petrography and X-ray diffraction (XRD), will facilitate more effective applications in both metallogenic research and prospecting practices for sandstone-type uranium deposits in northern China.

Minerals doi: 10.3390/min16050470

Authors: Wang Yang Jiang Wang Yang Zhang Hu Li Pan Wang Peng Zhu

The Linhe Formation of the Paleogene in the Linhua Well area of the Hetao Basin is a key target interval for hydrocarbon exploration, but strong heterogeneity caused by depositional and diagenetic modification complicates reservoir prediction. This study integrates core observations, thin-section petrography, SEM, clay mineral XRD, vitrinite reflectance (Ro), routine petrophysical data, and conventional well logs to characterize sedimentary microfacies and diagenesis, constrain the diagenetic stage and paragenetic sequence, establish a well-log-based diagenetic facies recognition model, and reveal the spatial distribution of diagenetic facies. The reservoirs are dominated by lithic arkoses and feldspathic litharenites with moderate compositional and textural maturity. Sedimentary microfacies mainly include a subaqueous distributary channel, front sheet sand, and interdistributary bay. The reservoirs are presently overall in mesodiagenetic stage A. Compaction and cementation are the principal destructive processes, whereas dissolution is the main constructive process. Quantitative evaluation shows that COPL ranges from 14.3% to 31.6% (average 25.2%), CEPL from 5.3% to 18.7% (average 12.7%), and ICOMPACT from 0.47 to 0.80 (average 0.66), indicating that compaction contributed more to porosity loss than cementation. Four diagenetic facies were identified: strongly compacted–weakly cemented, moderately compacted–strongly cemented, moderately dissolved–moderately cemented, and weakly compacted–weakly cemented. Fisher’s linear discriminant model based on GR, AC, DEN, and CNL logs achieved an overall recognition accuracy of 80.0%. Spatially, high-quality reservoirs are mainly developed in the central–southern subaqueous distributary channel belts dominated by the weakly compacted–weakly cemented facies and flanked by moderately dissolved–moderately cemented facies. High-quality reservoir development is controlled by the coupled effects of depositional microfacies, differential compaction–cementation, and local dissolution.

Minerals doi: 10.3390/min16050469

Authors: Chengbao Geng Mingxin Duan Zhande Hou Yanchao Cao Zeyou Xuan Hongqiang Zhao Haicheng Zhang Yongmei Zhang

The Ailinwudui gold deposit is located in central Jilin Province and represents a newly discovered typical vein-type gold deposit hosted in a Paleozoic metamorphic rock series in recent years. At present, the metallogenic epoch and regional metallogenic tectonic setting of the deposit remain poorly constrained, which seriously restricts the understanding of gold metallogenic regularities and subsequent mineral exploration deployment in central Jilin. Previous studies indicate that the Ailinwudui gold deposit is a structurally controlled vein-type gold deposit. In this study, zircon U-Pb and muscovite 40Ar/39Ar geo-chronology were employed to precisely constrain the metallogenic timing of the gold mineralization. Zircon U-Pb dating yields an emplacement age of 174.7 ± 0.85 Ma for the granodiorite and a formation age of 209.5 ± 1.40 Ma for the rhyolite porphyry. Muscovite 40Ar/39Ar dating yields a plateau age of 180.39 ± 1.83 Ma, which confines the gold mineralization to the Early–Middle Jurassic. Whole-rock geochemical results reveal that the granitoids in the study area are enriched in large-ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in high-field-strength elements (HFSEs), showing typical arc-related magmatic affinities. The formation of this gold deposit is related to the subduction of the Paleo-Pacific Plate during the Early–Middle Jurassic. The research results can provide important geochronological and geochemical evidence for the study of gold metallogenic mechanisms and mineral exploration in central Jilin Province.

Minerals doi: 10.3390/min16050468

Authors: Orlando Yepsen Lorena Cornejo-Ponce Rodrigo Yepsen

This research investigates the fundamental impact of the photochemical effect of sunlight on the oxidative dissolution of chalcopyrite (CuFeS2) in sulfate-oxidizing media under mild conditions and circumneutral pH. Beyond its traditional role as a thermal or electrical energy source, this study explores solar light (UV-Vis-NIR) as a photochemical reagent capable of driving the in situ generation of reactive sulfur species to assist the conventional oxidative dissolution pathway. The interaction at the mineral–solution interface under UV-Vis radiation was investigated using a laboratory-scale solar-assisted PS/TiO2/UV-Vis-NIR system, employing persulfate (S2O82−) as a radical precursor and TiO2 (Aeroxide® TiO2 P25) as a photocatalyst. The findings demonstrate that solar exposure increases the system’s electrochemical potential and induces pH changes, which are critical for overcoming the inherent refractoriness of CuFeS2 at near-neutral pH. This study demonstrates that integrating UV-Vis-NIR radiation serves as a synergistic catalyst in oxidative hydrometallurgical processes, enhancing Cu extraction yields to 14%–19% within 5 h of exposure at the laboratory scale. The use of natural light could offer a synergistic pathway to augment the efficiency of cleaner leaching technologies. These findings suggest that solar radiation could serve as a promising assistant to address kinetic limitations during the oxidative dissolution of complex sulfide ores under ambient conditions.

Minerals doi: 10.3390/min16050467

Authors: Louis R. G. Penfound-Marks Ben J. Williamson Julian F. Menuge

The critical metal lithium (Li) is increasingly sourced from spodumene and petalite pegmatite deposits due to their relatively high grades, lower mining environmental impacts and widespread global distribution. However, there are numerous gaps in our understanding of their genesis and the formation of unzoned or poorly zoned Li pegmatites is particularly difficult to explain. To investigate this, both spodumene-bearing and non-mineralized pegmatites and aplites are studied in the Moylisha segment of the Leinster pegmatite belt of SE Ireland, which were emplaced within the East Carlow Deformation Zone (ECDZ). Trace element modeling suggests that granite melts can achieve Li concentrations high enough (~5000 ppm) to crystallize spodumene. However, once crystallization begins, Li levels will drop rapidly below this threshold. While Li could be replenished by incoming melts, there is no supporting textural evidence for this, such as internal magmatic contacts, crosscutting relationships, or mingling. We test the hypothesis that low viscosity, Li-rich fluids from underlying reservoirs, most likely almost fully crystallized granite magmas or mush, continuously migrate through the heterogeneously crystallizing pegmatite-forming melts by percolative reactive flow, refertilizing interstitial melt by diffusion under favorable geochemical gradients. The flow of fluids is likely maintained due to their low relative density and periodic shearing within the ECDZ. Fluids with >10,000 ppm Li, derived by >95% crystallization (Rayleigh fractionation) of a granite magma, are shown to be capable of refertilizing a pegmatitic crystal mush after its emplacement. Supporting evidence includes macro- and micro-textures indicative of paragenetically late spodumene crystallization along apparent fluid flow pathways in mineralized pegmatites and aplites. Similar features are common in spodumene pegmatites worldwide and suggest that Li upgrading by fluid flow through crystallizing spodumene pegmatites may be a key process in enhancing Li grades and in some cases in producing economically favored low-Fe spodumene.

Minerals doi: 10.3390/min16050466

Authors: André Renan Costa-Silva Débora Ayumi Ishida Ingred Nóbrega Teixeira Yves Lucas Adolpho José Melfi Célia Regina Montes

In the saline–alkaline lake (SAL) systems of the Nhecolândia region, Brazilian Pantanal, soils exhibit complex mineralogical assemblages controlled by sediment inheritance, pedogenesis, and hydrogeochemical gradients. This study investigates the distribution and transformation of 2:1 phyllosilicates along representative SAL toposequences. Soil samples were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), supported by granulometry and adjustment of the FTIR spectra. Mineralogical data were integrated with geochemical (Al, K, Mg, Ca, Na) and pH data and examined using principal component analysis (PCA). Greenish loamy horizons act as key morphological controls on hydrogeochemistry, regulating solute retention along mid- to downslope transitions. Illite is more strongly associated with upslope positions, whereas downslope alkaline environments are associated with smectitic phases (e.g., montmorillonite and Mg-rich varieties such as saponite) and mixed-layer minerals structures (e.g., illite–smectite and montmorillonite–vermiculite structures). These assemblages are consistent with non-linear transformation pathways, with illite as a possible transitional phase between micas and expandable structures. The PCA results suggest a primary mineral distribution structured by fine-material content and depth, while pH and alkalinity emerge as key geochemical controls that differentiate mineral stability fields and reinforce the hydrogeochemical compartmentalization of the profiles. Geochemical data show strong associations of Al, Mg, and K with fine-fraction accumulation. The integration of these approaches highlights that a 2:1 phyllosilicate assemblage results from multiple superimposed pedogenetic pathways, offering a conceptual framework for studying complex soil–lake systems.

Minerals doi: 10.3390/min16050465

Authors: Kefeng Du Yonghong He Yunjin Ge Xuan Tang Jing Xu Huifang Bai Xiaoxiao Wei Congsheng Bian Jin Dong Ziheng Guan

The Ordos Basin hosts abundant lacustrine shale oil resources. Adequately retained hydrocarbons in source rocks, together with favorable mobility, are prerequisites for large-scale shale oil exploitation. Therefore, the quantitative characterization of retained hydrocarbon content and mobility is a core research focus in shale oil exploration and development. This study investigates Chang 7 shale with varying lithofacies and geochemical characteristics. Stepwise pyrolysis and pyrolysis gas chromatography–mass spectrometry (GC–MS) were applied to analyze retained hydrocarbons in different occurrence states, their compositions, and biomarkers. In addition, nuclear magnetic resonance (NMR) combined with CO2 flooding experiments was conducted, and the collected products under different displacement pressures were analyzed using GC–MS. The aim was to quantitatively examine the variations in expelled oil volume, compositional differences during migration, and occurrence features of shale oil within reservoir micro-pores. The results show the following: (1) Organic-rich shale is characterized by higher proportions of light and medium hydrocarbons, lower heavy fractions, and elevated aromatic hydrocarbon content. In contrast, low-organic-carbon mudstone or siltstone contains more medium and heavy hydrocarbons, with lower light and aromatic fractions. The C13−/C14+ ratio increases with total organic carbon (TOC). (2) In black shale, oil displacement is mainly contributed by mesopores. At low pressures, oil expulsion is difficult and dominated by heavy hydrocarbons. When pressure reaches a threshold, the capillary-bound oil in micropores is released, increasing production and improving oil quality. Muddy siltstone shows higher displacement efficiency than black shale, with contributions from pores of all sizes. At low pressures, its expelled oil volume is larger and lighter than that of black shale. With increasing pressure, the oil yield rises significantly, and medium–large pores produce heavier fractions compared with micropores, likely because light hydrocarbons preferentially enter micropores and are less prone to dissipation. (3) The main controlling factors for shale oil enrichment include retained hydrocarbon content, mobile hydrocarbon fraction, fluidity, and engineering-related parameters. Thick shale layers with high organic matter abundance, high proportions of light–medium hydrocarbons, and favorable porosity–permeability conditions, as well as interbedded siltstone, are enriched in mobile hydrocarbons.

Minerals doi: 10.3390/min16050464

Authors: Carlos Guillermo Perea Solano Tony Tang Chaoran He Aissa Polenio Jacques Eksteen

The increasing demand for platinum group metals (PGMs) and critical base metals (BMs) underscores the critical roles these metals play in renewable energy and advanced technologies, enabling more efficient, environmentally sustainable operations. A hydrometallurgical approach to Au, Pd, and Pt tailings, derived from the glycine leaching of low-grade nickel and iron sulfide flotation concentrates, is investigated. The proposed process evaluates two glycine-based systems: glycine combined with KMnO4 and catalyzed by cyanide under starvation conditions. Leaching with glycine in the presence of KMnO4 (72 h, 25% solids, 60 °C, pH 11, dissolved oxygen 10 ppm, 126.7 kg/t glycine, and 7 kg/t KMnO4) achieved extraction efficiencies of up to 66.7% Au, 89.1% Pd, and 95.8% Pt. In comparison, the cyanide-starved glycine system (72 h, 30% solids, 60 °C, pH 11, dissolved oxygen 20 ppm, 98.5 kg/t glycine, and 3.3 kg/t cyanide) resulted in up to 80.8% Au, 78.3% Pd, and 14.3% Pt. Activated carbon and Amberlite resin demonstrated selective adsorption of Au and PGMs. For activated carbon, Au adsorption exhibited a non-linear dependence on carbon dosage, reaching a maximum of 77.61% at 20 g/L, then decreasing to 50.85% at 25 g/L, and finally increasing to 65.04% at 30 g/L, indicating variable adsorption behavior. In contrast, Amberlite resin exhibited more consistent, progressive adsorption with increasing dosage. Au adsorption remained high across all conditions, increasing from 88.06% at 10 g/L to 99.67% at 30 g/L. Similarly, Pd and Pt adsorption improved significantly with resin dosage, reaching maximum values of 81.32% and 83.36% at 25 g/L, respectively, followed by a slight decline at 30 g/L. Implementing a two-stage process using carbon + resin (30 g/L) increased PGM recovery, achieving 99.89% Au, 81.8% Pd, and 92.4% Pt. Elution tests showed that Au (61.97%) and Pd (60.55%) were desorbed efficiently using thiourea (2% w/v) and HCl (0.5 M), whereas Pt elution proved difficult and required alternative strategies. The findings confirm glycine-based technologies as a promising, environmentally friendly alternative to conventional methods and provide a basis for further process development and optimization.

Minerals doi: 10.3390/min16050463

Authors: Aidarkhan Kaltayev Zhomart Ualiev Asylkhan Bibossinov

Efficient uranium recovery from productive leaching solutions requires accurate prediction of hydrodynamic and mass-transfer processes in ion-exchange sorption columns. In this study, a coupled multidimensional hydrodynamic and mass-transfer model is developed to investigate uranium sorption in a packed ion-exchange column equipped with a conical flow distributor. Fluid flow in the porous resin bed is described using the Forchheimer filtration law combined with the mass conservation equation, while transport of dissolved uranium species is modeled using a convective–dispersion equation coupled with a linear driving force kinetic model. The numerical solution is obtained using the fictitious domain method, which enables accurate representation of complex column geometries. The results reveal pronounced radial flow non-uniformity, incomplete flow equalization, and the formation of a ring-shaped sorption zone, indicating uneven utilization of the sorbent bed. It is shown that under practical operating conditions, mass-transfer dynamics are governed primarily by hydrodynamics rather than intrinsic sorption kinetics. The proposed model provides a practical tool for analysis and optimization of industrial uranium recovery columns.

Minerals doi: 10.3390/min16050462

Authors: Cihan Yalçın Mehmet Altunbey

The Akseki–Kuyucak bauxite deposits, located in the Western Taurus Belt in southwestern Türkiye, represent karst-type bauxite mineralization derived from carbonate platform phases. This work integrates field observations, X-ray diffraction (XRD) analysis, and extensive geochemical data, including major, trace, and rare earth elements (REEs), to clarify the mineralogical characteristics, geochemical processes, and genetic implications of the deposits. Field and petrographic investigations indicate that the bauxite deposits occur as irregular fills and lens-shaped formations on paleokarstic surfaces of carbonate substrates. The XRD examination reveals that the major minerals in the bauxite samples are boehmite, hematite, and anatase, with some samples exhibiting a predominance of calcite, indicating a strong genetic relationship between the ore bodies and the carbonate host rocks. Major oxide analysis reveals a distinct compositional disparity between bauxitic and carbonate-dominated materials: bauxitic samples exhibit elevated Al2O3 and Fe2O3 levels, with reduced SiO2 and CaO concentrations. In contrast, carbonate-rich samples show higher CaO and loss-on-ignition values. Ternary discrimination diagrams categorize most bauxitic samples into the ferritic bauxite and robust lateritization domains, indicating substantial weathering and residual enrichment processes. The trace element and REE studies reveal ΣLREE values ranging from 22.3 to 240.2 ppm, with a right-skewed distribution indicating heterogeneous enrichment. Correlation studies indicate that ΣLREE has a positive correlation with SiO2 and K2O, suggesting that the enrichment of REEs is more closely associated with silicate/clay minerals than with iron oxide phases. Furthermore, spider diagrams and the study of immobile components emphasize the significance of residual concentration processes in bauxitization. In contrast, modest TiO2 levels indicate a composite source derived from both insoluble carbonate remnants and detrital siliciclastic materials. In summary, the Akseki–Kuyucak deposits are categorized as intricate karst bauxite systems, characterized by significant lateritization, regulated accumulation governed by paleokarst characteristics, and a complex geochemical evolution. The results demonstrate that integrating mineralogical, geochemical, and statistical methods provides a thorough framework for evaluating REE behaviors and the effects of source-related factors in karst bauxite deposits.

Minerals doi: 10.3390/min16050461

Authors: Zhibin Zheng Mengmeng Zhang Siyi Zhao Bo Xu Shiqi Wang Mengxi Zhao Qi Wang

Gem-quality garnets exhibit significant potential for U-Pb geochronological applications due to their advantageous characteristics, including high closure temperatures (750–850 °C), optical transparency, chemical homogeneity, and low inclusion content. This study focuses on the gem-quality yellow-green grossular garnet variety (commonly termed Mali garnet), a unique gemstone exclusively occurring in contact metamorphic deposits of Western Africa’s Republic of Mali. Despite its mineralogical significance, fundamental aspects, including precise age determination and chromophore mechanisms of Mali garnet, remain poorly constrained. Here, we conducted standard gemological characterization, spectroscopic analyses (UV–Vis, FTIR, and Raman), electron probe microanalysis (EPMA), micro-X-ray fluorescence (μ-XRF) elemental mapping, and in situ trace element and laser ablation U-Pb geochronological analysis on Mali garnets. The spectral data and chemical composition studies reveal that the coloration of Malian garnets is primarily attributed to the presence of iron and chromium. Our U-Pb geochronological results yield a crystallization age of 197 ± 3 Ma for the Mali garnet samples. The robustness of garnet U-Pb systems in preserving crystallization ages through multiple thermal events supports their application to Precambrian polymetamorphic terranes, where zircon systems are frequently reset.

Minerals doi: 10.3390/min16050460

Authors: Amina Wafik Mohamed Ben Massoude Youssef Atif Atman Ait Lamqadem Reza Rooki Aref Shirazi Adel Shirazy Amin Beiranvand Pour

Serpentinites and associated chromitites of the Neoproterozoic Bou Azzer ophiolite (Central Anti-Atlas, Morocco) provide key constraints on mantle depletion, melt–rock interaction, and the tectono-metamorphic evolution of a supra-subduction zone (SSZ) system. This study integrates field observations, petrography, Raman spectroscopy, and whole-rock/mineral chemistry to decipher the history of this highly dismembered ultramafic suite. The mantle sequence is dominated by antigorite-bearing serpentinites derived primarily from refractory harzburgitic and dunitic protoliths. Whole-rock geochemistry and highly depleted chromite compositions (Cr# = 0.50–0.68; Mg# = 0.43–0.77; TiO2 ≤ 0.18 wt.%) demonstrate that these peridotites represent refractory residues formed after high degrees of partial melting (~15–25%). The data delineate a clear evolutionary trend from abyssal to fore-arc and back-arc environments, where infiltrating boninitic melts drove localized podiform chromitite formation through intense melt–rock interaction. Crucially, thermodynamic and mineral–chemical constraints challenge previous models of simple greenschist-facies obduction. Equilibration temperatures exceeding 600 °C and chromite stability within the lower amphibolite to near-granulite facies indicate that the oceanic lithosphere underwent deep subduction prior to its exhumation. This high-temperature, high-pressure metamorphism was followed by multistage retrogressive serpentinization and intense CO2-rich metasomatism (talc-magnesite alteration) during Pan-African transpressional tectonics. Ultimately, the Bou Azzer ophiolite represents a mature SSZ mantle wedge, recording a complete geodynamic cycle from deep subduction-zone metamorphism to final tectonic emplacement along the northern margin of the West African Craton.

Minerals doi: 10.3390/min16050459

Authors: Frederico C. M. Santos João A. M. S. Pratas Victor A. S. Vicente Luís E. N. Conde Paulo J. C. Favas Marina Cabral Pinto

This study presents the first stream-sediment geochemical survey conducted in the western Oecusse enclave (Timor-Leste), aiming to identify geochemical anomalies associated with potential metallic mineralization in a region where mineral occurrences remain poorly documented. A total of 27 stream-sediment samples were collected from first- and second-order drainage systems and analysed for a multi-element suite using ICP-MS and INAA. Robust statistical approaches, including univariate analysis, median absolute deviation (MAD), Tukey boxplot thresholds, and compositional data analysis combined with principal component analysis (CLR–PCA), were applied to identify anomalous geochemical associations. To improve statistical robustness, PCA was performed on reduced and process-oriented variable sets. The results reveal significant geochemical variability, with maximum concentrations reaching 214 mg/kg for As, 142 mg/kg for Co, 27,220 mg/kg for Cr, 437 mg/kg for Cu, 1520 mg/kg for Ni, 67 mg/kg for Pb and 267 mg/kg for Zn. Multivariate analysis distinguishes two main geochemical signatures. The first association (Co–Cr–Ni–Mg–Fe) reflects a strong ultramafic geochemical signal consistent with contributions from mafic to ultramafic lithologies documented in the region. The second association (As–Bi–Cu–Pb–S–Sb–Se–Tl–Zn) indicates polymetallic enrichment commonly observed in sulphide-related geochemical systems. The spatial distribution of these geochemical signals highlights localized drainage basins exhibiting relative enrichment patterns. These results demonstrate the effectiveness of stream-sediment geochemistry as a first-pass exploration tool and provide new geochemical constraints for geological interpretation and future mineral exploration in Timor-Leste. The approach demonstrates the value of integrated geochemical and statistical methods for mineral exploration in data-poor regions.

Minerals doi: 10.3390/min16050458

Authors: María de Lourdes Pérez Lamorú Iván Salazar Hugo Javier Angulo-Palma Yoalbys Retirado-Mediaceja Yunior Correa-Cala Yosvany Díaz Cárdenas Juan Alberto Ribalta-Quesada Roger Samuel Almenares Reyes Manuel Saldana Felipe M. Galleguillos Madrid Norman Toro

Replacing clinker with mixtures of calcined clay and limestone is one of the most sustainable strategies for decarbonizing the cement industry. However, the kinetic patterns governing the grinding behavior of these materials are not yet fully understood. This study developed a kinetic model based on particle population balance to simulate this process. Experiments were conducted using a standard Bond ball mill, and the samples were characterized by X-ray diffraction. The results show that the grinding of calcined clay and its mixtures with limestone follows first-order kinetics. The proposed model simulates the process with a high degree of accuracy, with residual errors below 1.5% and a coefficient of determination exceeding 99%.

Minerals doi: 10.3390/min16050457

Authors: Lining Yu Huibin Zhang Junfeng Kong Anyang Tang Huazhen Cao Guoqu Zheng

The recovery of tin from high-barium copper anode slime by Kaldor furnace smelting remains challenging because barium sulfate hinders the conversion of tin (Sn) from SnO2 into acid-soluble phases. In this study, the smelting behavior of high-barium copper anode slime in a Kaldor furnace was simulated under optimal smelting conditions: SnO2 was effectively converted into BaSnO3, while SiO2 was transformed into Na2Ba6Si4O15, achieving a high Sn conversion efficiency of 92.18%. Phase and microstructure analyses indicated that the preferential reaction of SiO2 with Na2CO3 and BaSO4 governs the early-stage phase reconstruction, whereas the subsequent reaction between SnO2 and BaCO3 promotes the formation of BaSnO3. Kinetic analysis showed that the Sn conversion process was well described by the Avrami–Erofeev model, with an apparent activation energy of 43.75 kJ/mol and an Avrami index of 1.13, suggesting mixed control by diffusion and chemical reaction. Thermodynamic analysis further confirmed that stannates and silicates are the dominant equilibrium phases under the optimized conditions. This work provides a promising route for the efficient recovery of tin from high-barium, tin-bearing smelting slag.

Minerals doi: 10.3390/min16050456

Authors: Ryskul Azhigulova Kaster Kamunur Lyazzat Mussapyrova Aisulu Batkal Aisulu Zhussupova Rashid Nadirov

Knowledge of the heterogeneous composition of mineral substances and technogenic materials is vital in the development of technological designs and in environmental impact assessments. However, the simultaneous application of analytical methods often reveals discrepancies between different methods that cannot be explained by the commonly used scalar agreement metrics. The current study suggests the possibility of evaluating inter-methodical agreement in the compositional data of heterogeneous substances using the example of lead smelting slag compositional data. The compositional data of 96 samples of lead smelting slag were analyzed using independent methods of XRF, ICP-OES and AAS. The agreement between the obtained results was evaluated at three levels of hierarchy: element-wise bias and dispersion, structured variability between methods and preservation of covariance structure; PCA was used as the tool for the evaluation. High agreement between the ICP-OES and AAS methods was found for the transition metals (r ≈ 0.97–0.99), with negligible bias. The presence of increased dispersion and deviations in the inter-methodical agreement was found in the case of the methods compared with the XRF method, especially for the matrix components such as Si (r ≈ 0.92). Coefficients of variation for metallic elements stay between 12 and 15%, but XRF has shown consistently higher variability for certain elements. PCA results show that despite local differences, the main covariance structure was kept across methods, with the first two components explaining about 40–45% of total variance. These results clearly indicate that high correlation does not necessarily ensure methodological interchangeability. The hierarchical framework proposed here will provide a reproducible basis for cross-method validation and support reliable data integration in complex mineral systems.

Minerals doi: 10.3390/min16050455

Authors: Yiliang Liu Guihua Yang Shihao Zhang Dongwei Cao Guangtian Zhang Zongjie Li Cheng Zhang

The complexity of physicochemical properties in iron ore tailings has led to extensive and varied study avenues. Moreover, changes in these features resulting from source discrepancies have complicated the identification of consistent patterns in study findings, thereby hindering the standardization and advancement of resource exploitation technologies. This paper provides a comprehensive analysis of the utilization pathways for iron tailings. It identifies the mainstream recovery processes for rare earth minerals, a relatively less-researched direction. It also describes research progress on the use of iron tailings for the preparation of fertilizers and soil conditioners, as well as their application as cementitious materials or aggregates in building materials and mine backfilling engineering. It incorporates various activation methods for the preparation of cementitious materials from iron tailings into a unified comparative framework and quantifies the key performance indicators of different activation pathways through a summary table. It also summarizes studies on the ecological reclamation of tailings ponds based on bioremediation techniques. The essential physicochemical properties of iron deposits are meticulously analyzed, and this is followed by a specialized overview of the principal treatment techniques, critical performance indicators, and their foundational mechanisms. The current application of various technical approaches is examined to identify key problems, and future development opportunities are outlined.

Minerals doi: 10.3390/min16050454

Authors: Wei Li Linglin Zhong Suiliang Dong Xianglong Yu Yubin Li Jiacong Wu Khin Ei Thu Xin Sun

The Oligocene–Miocene magmatic rocks extensively developed in the Gangdese magmatic belt are key records of the post-collisional tectono-magmatic evolution of the Tibetan Plateau. In this study, petrological, zircon U-Pb geochronological, zircon Hf isotopic and whole-rock geochemical investigations were carried out on two granitic porphyry stocks exposed in the Chunzhe area of the middle Gangdese belt. LA-ICPMS zircon U-Pb dating, cathodoluminescence (CL) images and trace element characteristics indicate that the granitic porphyries were emplaced at 11.8 ± 0.2 Ma (MSWD = 1.1) and 11.5 ± 0.1 Ma (MSWD = 1.2), with a small number of zircon grains yielding 206Pb/238U ages of 51.1~59.5 Ma, 29.8 Ma and 19.4~12.2 Ma, which are interpreted as inherited or captured zircon components. The analyzed samples are monzogranite porphyries composed mainly of quartz, plagioclase and alkali feldspar, with variable secondary white mica/sericite. In whole-rock composition, they display high-K calc-alkaline and weakly peraluminous characteristics. These rocks are enriched in large-ion lithophile elements (LILEs) such as Ba, Sr and Rb, and relatively depleted in Nb-Ta-Ti as well as Cr and Ni. They show light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion, with distinctly high chondrite-normalized La/Yb ratios (31.05~71.25) and Sr/Y ratios (35.90~49.07), and a positive correlation between the LREE/HREE ratio and La content, indicating robust adakite-like trace element characteristics. Zircon εHf(t) values of the Miocene magmatic rocks range from −4.44 to 2.41, corresponding to two-stage Hf model ages of 1380~944 Ma, suggesting that the magmas were mainly derived from juvenile continental crust materials with the addition of a small amount of ancient continental crust materials. Combined with the regional geological setting, the Chunzhe Miocene granitic porphyries were most likely generated by partial melting of the thickened lower crust in the Gangdese belt during the late stage of Oligocene–Miocene post-collisional magmatism; local lower-crustal delamination may also have contributed, although this is not uniquely constrained by the present dataset.

Minerals doi: 10.3390/min16050453

Authors: Ming Xu Yingying Zhang Xinyu Wu Wenyu Wu Wenkai Liu

The interpretation of geophysical multi-attribute surveys is often subjective and complicated by large datasets, prompting the need for automated fusion methods that preserve structures and enhance anomalies. This study introduces an image fusion approach that combines the non-subsampled contourlet transform (NSCT) with the New Metric Parameter (NMP) rule to integrate multi-source polarizability and resistivity data for copper–nickel exploration. Using NSCT, source images are decomposed into multi-scale, multi-directional low- and high-frequency sub-bands. Low-frequency components are fused through dynamic weighting, while high-frequency components are merged using the NMP rule. The sensitivity to key parameters—such as low-frequency weight, grid size, and grid angle—was assessed using field data. Results indicate that NSCT + NMP fusion enhances spatial resolution and boundary definition of anomalies, effectively merging low resistivity with high polarizability signals. Quantitative field validation shows that 82.43% of the gabbroic mineralization zone has a judging coefficient below 0.45, confirming the fusion accuracy. Optimal parameter choices include dynamically adjusted low-frequency weights, a grid size that balances detail and noise suppression, and a 45° square grid for directional neutrality. This method offers a practical strategy for joint multi-physical data analysis and improved spatial recognition of mineralized bodies in exploration.

Minerals doi: 10.3390/min16050452

Authors: Marianna Cangemi Fabio Sposito Valentina Censi Tiziana Cannata Alessandro Montemagno Lorenzo Brusca Ygor Oliveri

This study investigates the geochemical behavior and transport mechanisms of Rare Earth Elements (REEs), Yttrium (Y), Zirconium (Zr), and Hafnium (Hf) in three natural water systems under reducing conditions: the Santa Barbara and Occhio dell’Abisso mud volcanoes and a sulphureous spring at Villafranca Sicula. A comprehensive fractionation approach was applied to isolate the truly dissolved fraction (TDF < 10 kDa), the colloidal fraction (10 kDa < CF < 450 nm), the suspended particulate matter (SPM > 450 nm), and the associated bottom sediments. Analytical results reveal that REE distribution is significantly influenced by redox conditions and solid–liquid interface processes. The absence of negative Cerium (Ce) anomalies and the presence of pronounced positive Europium (Eu) anomalies in the Santa Barbara and Occhio dell’Abisso waters suggest strongly reducing environments where Eu2+ stability is enhanced. Shale-normalized patterns indicate that, while SPM and sediment fractions often exhibit Middle REE (MREE) enrichment, linked to Mn-bearing and Fe-oxyhydroxide phases, the dissolved phase reflects dissolution processes governed by a non-CHARAC (CHarge-and-RAdius-Controlled) behavior. Furthermore, the study highlights a significant decoupling in the Zr/Hf and Y/Ho pairs. While these pairs remain coherent during magmatic processes, they undergo mutual fractionation in aqueous systems due to differential reactivity toward colloidal surfaces and organic ligands. Specifically, Zr/Hf ratios in the colloidal and dissolved fractions deviate from chondritic values, driven by the preferential scavenging of Hf onto mineral surfaces. These findings underscore the utility of REE and Zr-Hf systematics as high-resolution tracers for reconstructing water–rock interaction processes and elemental cycling in complex hydrological environments.

Minerals doi: 10.3390/min16050451

Authors: Joseph Ndago Amoldago Emmanuel Daanoba Sunkari

Hydrogeochemistry is a practical and low-impact tool for mineral exploration that relies primarily on groundwater as sampling media. It is particularly valuable for blind or deeply buried deposits where surface geochemical methods are ineffective, as groundwater acts as a natural integrator of geochemical signals from depth. This study presents a PRISMA 2020-compliant systematic review of hydrogeochemical exploration practices published between 1946 and 2025, synthesizing 118 empirically screened case studies from diverse geological and climatic settings. The review evaluates the geochemical processes governing aqueous dispersion halos, including sulphide oxidation, water–rock interaction, redox controls, and physicochemical speciation, and assesses how these processes influence pathfinder behaviour and anomaly expression. Quantitative synthesis highlights consistent patterns in hydrogeochemical footprints across major mineral systems and demonstrates the effectiveness of thermodynamically informed and multivariate interpretation strategies over simple concentration-based approaches. Emerging trends identified include the growing application of non-traditional stable isotope fractionation, nanoparticle geochemistry using single-particle ICP-MS, and integration of hydrogeochemical datasets with GIS, geophysics, and machine learning-based prospectivity modelling. Unlike recent narrative reviews, this study provides a fully reproducible, structured evaluation of the global evidence base and formalizes a standardized end-to-end workflow.

Minerals doi: 10.3390/min16050450

Authors: Mingjing Fan Keyan Xiao Li Sun Yang Xu Shuai Zhang

With the development of geological data analysis and big data technology, intelligent mineral prospectivity mapping (MPM) has become a key direction in the integration of geoscience and artificial intelligence, showing promising applications in the identification and evaluation of strategic mineral resources such as gold. To address the limitations of conventional methods—including insufficient training samples, complex model structures, and weak capability in recognizing anomalous zones—this study proposes an improved convolutional neural network (CNN) approach for mineral prediction. A lightweight, modular CNN structure with repeatable stacking is designed to reduce computational cost while enhancing model robustness and generalization. In addition, a dynamic learning rate scheduling strategy is adopted to optimize the training process, significantly improving convergence speed and training stability. Furthermore, high-probability prediction samples and low-probability background samples are combined to form a new training dataset for regional prospectivity evaluation, yielding a high area under the curve (AUC) score. The method is applied and validated in the Xiong’ershan region, and the predicted high-potential zones account for 30% of the study area and contain 81.4% of the known gold deposits. These results demonstrate the method’s effectiveness in mineral information extraction and blind-area targeting, offering a new approach for mineral prospectivity mapping.

Minerals doi: 10.3390/min16050449

Authors: Matías Jeldres Eder Piceros Luis A. Cisternas Ricardo I. Jeldres

This study investigates sodium polyacrylate (NaPA) as a rheology modifier and selective depressant in the flotation of Cu2+-activated kaolin–chalcopyrite under industrial water (IW) and seawater (SW) conditions. The work addresses a critical gap in saline systems: how an anionic polymer simultaneously influences clay activation, sulfide floatability, aggregate dispersion, and pulp rheology by varying the medium’s ionic composition. Microflotation, zeta potential, adsorption, yield strength, and Focused Beam Reflectance Measurement (FBRM) assays were used to establish structure–property–response relationships. In IW, Cu2+ strongly promoted NaPA adsorption onto both minerals, shifting them toward more negative potentials and significantly reducing selectivity: kaolin recovery decreased from 86.5% to 40.0% at 50 ppm NaPA. In comparison, chalcopyrite recovery fell below 30% at 100 ppm NaPA. In SW, NaPA maintained its depressant effect on kaolin without affecting chalcopyrite flotation, which remained above 90%. This behavior is consistent with reduced polymer adsorption at high ionic strength, where ionic shielding and coiling limit its interaction with chalcopyrite but allow sufficient adsorption onto kaolin to inhibit the collector’s action. Rheological and FBRM results support this interpretation, showing a decrease in yield strength and aggregate size after NaPA addition, with a more pronounced effect in IW than in SW.

Minerals doi: 10.3390/min16050447

Authors: Boris Vakanjac Marko Simić Siniša Drobnjak Rastko Petrović Radoje Banković Saša Bakrač Miodrag Kostić

Uranium exploration in southeastern Mongolia remains constrained by fragmented Soviet-era datasets and limited modern synthesis. This study addresses the problem of integrating historical geological records with contemporary exploration methods to evaluate uranium mineralization potential. A comprehensive GIS-based database was compiled from Soviet reports legally acquired from the Mineral Resources Authority of Mongolia and expanded with geological, geophysical, and drilling data collected between 2006 and 2011. Methodological advances included remote sensing detection of anomalous radioactivity in arid environments, stratigraphic modeling, and hydrogeochemical surveys. The dataset encompasses more than 1100 radioactive anomalies and approximately 300 mineralized zones, with emphasis on the Han Bogd granite massif, Ail Bayan coal deposit, Suujin Tal structural system, Zuunbayan depression, and Naarst structural complex. Results indicate that most anomalous zones are sub-economic, commonly associated with organic-rich facies such as coal seams, while the continuity of mineralized bodies remains uncertain. Nevertheless, the dual consideration of granitic source terrains and coal-bearing sedimentary traps provides new insights into uranium mobility and deposition. The significance of this work lies in its systematic integration of historical and modern data, offering a refined geological framework and highlighting key areas for future investigation, thereby contributing to ongoing discussions on sedimentary uranium resources in Mongolia. Results indicate that most anomalous zones are sub-economic, commonly associated with organic-rich facies such as coal seams, while the continuity of mineralized bodies remains uncertain. Importantly, the study highlights granitic intrusions and volcanic complexes as the primary uranium sources, with coal-bearing and sedimentary basins acting as secondary depositional environments. The dual consideration of source terrains and depositional traps provides new insights into uranium mobility and deposition.

Minerals doi: 10.3390/min16050448

Authors: Gui Wang Hu-Jun Zhang Hao-Hao Zhang Yang-Quan Jiao

The interlayer oxidation zone-type Mengqiguer uranium deposit in the southern Yili Basin is a typical sandstone-hosted uranium deposit in northwest China, and the lower member of the Jurassic Xishanyao Formation is its main ore-hosting stratum. However, mineralogical and geochemical responses to redox evolution in the deposit have not been systematically constrained. In this study, we carried out detailed petrographic observation, X-ray diffraction analysis, electron probe microanalysis, and whole-rock geochemical analyses on samples from the interlayer oxidation zone in the lower member of the Xishanyao Formation. Kaolinite and illite are the dominant clay minerals in the deposit, with higher contents in oxidation zones than in transition and unaltered zones, while the illite–smectite mixed-layer content shows the opposite trend. The main uranium minerals are uranium oxides and coffinite. U, S and organic carbon are enriched in the transition zone, while the Fe3+/Fe2+ ratio increases with the oxidation degree. Comprehensive analysis on clay minerals shows that the ore-forming fluids evolved from acidic oxidized meteoric fluids to weakly alkaline reduced fluids; the uranium was mainly derived from the leaching of uraniferous sandstone. The formation of the deposit is controlled by sedimentary facies, tectonic uplift, organic–inorganic fluid interaction and redox reaction. This study provides detailed mineralogical and geochemical evidence for the metallogenic mechanism of interlayer oxidation zone-type uranium deposits, and has important guiding significance for uranium prospecting in the Yili Basin.

Minerals doi: 10.3390/min16050446

Authors: Yi-Han Lin Ming-Sen Fan Pei Ni Jun-Yi Pan Jun-Ying Ding Wen-Yi Wu Chen Zhang Zhe Chi Bin Guo Yi-Fan Gao

Sandstone-hosted uranium deposits in the western Qaidam Basin are spatially associated with hydrocarbon-bearing structures, yet the specific roles of different sulfur sources in uranium mineralization remain poorly constrained. This study aims to distinguish the contributions of bacterial sulfate reduction and hydrocarbon-associated sulfate reduction to uranium precipitation by integrating detailed petrography, in situ trace element analyses, and sulfur isotope measurements of chalcopyrite from the Yuejin II deposit. Chalcopyrite is restricted to high-grade uranium ores and occurs intergrown with uranium minerals, pyrite, baryte, and carbonate cements. Trace element patterns indicate that oxidizing brines acted as the main transport medium for both uranium and copper, as evidenced by positive correlations between U and brine-related elements (Ba, Sr, Na, K). Positive U-Th correlations with relatively constant Th/U ratios (0.027–0.225) reflect a combination of source composition, fluid transport capacity, and limited thorium remobilization in this near-source, hydrocarbon-rich environment. Correlations between U and high field strength elements (Sn, W) point to a highly evolved granitic origin, with Altyn granitoids likely supplying the copper. Sulfur isotopes show a clear bimodal distribution: one group exhibits heavy δ34S values (+6.9‰ to +18.5‰), while the other shows extremely light values (–36.0‰ to –44.6‰). The light group reflects bacterial sulfate reduction in shallow strata, supported by framboidal pyrite textures, whereas the heavy group corresponds to surface-derived sulfate reduced at hydrocarbon-associated redox fronts, rather than direct incorporation of deep H2S. The lack of intermediate δ34S values indicates that two discrete sulfur reduction mechanisms coexisted within the same deposit, refining genetic models for uranium mineralization in petroliferous basins and challenging frameworks that invoke a single dominant sulfur source.

Minerals doi: 10.3390/min16050444

Authors: Mehmet Ali Ertürk

The hornblende gabbro investigated in this study crops out in northwestern Elazığ, eastern Türkiye, within the Southeastern Anatolian Orogenic Belt (SAOB), where Late Cretaceous ophiolitic, volcanic, plutonic, and metamorphic units are widely exposed. This study examines the petrology, whole-rock geochemistry, Sr–Nd isotopic composition, mineral chemistry, and crystallisation conditions of these gabbroic bodies to constrain their petrogenesis and tectonomagmatic significance. Field observations show that the rock occurs as rounded to sub-rounded blocks with fresh inner cores and altered outer rims. Petrographic and XRD data indicate that the fresh gabbro mainly consists of plagioclase and amphibole, whereas the altered outer rims contain quartz and minor secondary phases. Whole-rock geochemical data classify the samples as low- to medium-K, tholeiitic, and predominantly metaluminous gabbro. Primitive mantle-normalised trace-element patterns display enrichment in large-ion lithophile elements and depletion in high-field-strength elements, whereas chondrite-normalised REE patterns show slight LREE enrichment, relatively flat HREE patterns, and weak Eu anomalies. Sr–Nd isotopic compositions are characterised by positive εNd(T) values (+4.4 to +5.3) and moderately radiogenic initial 87Sr/86Sr ratios (0.704792–0.705344), indicating a predominantly mantle-derived magma source affected by subduction-related modification, with limited crustal contribution. Mineral chemistry data show that amphiboles belong to the calcic amphibole group and plot in the magnesio-hornblende field. Amphibole thermobarometric calculations yielded temperatures of 873–991 °C and pressures of 1.49–3.26 kbar, corresponding to crystallisation depths of 5.1–15.3 km. Overall, the results indicate that the hornblende gabbro was derived from a mafic magma generated from a spinel lherzolite mantle source and crystallised in a subduction-related tectonomagmatic setting.

Minerals doi: 10.3390/min16050445

Authors: Carolina N. Keim André Rossi Marcos Farina

Floating rafts are thin, flat mineral layers that precipitate at still air–water interfaces. They are composed of calcite, aragonite, vaterite, gypsum, trona, carnallite, and/or halite. Floating rafts present a flat surface at the top in contact with air, and a rough surface at the bottom, which develops as they grow into the water. In this work, we describe floating rafts from hypersaline environments using imaging and analytical microscopy techniques. The four rafts studied consist of interconnected polycrystalline grains. Scanning electron microscopy (SEM) showed that the top surfaces were flat, whereas in the bottom surfaces, the grains protrude into the water. High magnification revealed nanoparticles arranged in stacks, suggesting growth through the organized agglutination of nanocrystals. Electron diffraction of two of the rafts indicates that they consist of aragonite. Accordingly, electron energy-loss spectroscopy (EELS) shows the C K-edges characteristic of carbonates, along with O and Ca edges. Energy-dispersive spectroscopy (EDS) in the SEM also revealed a few Ca sulfate crystals on the bottom surface. In addition, the presence of cubic shapes indicates the presence of halite. We hypothesize that the genesis of these rafts is driven by evaporation of still water, which increases supersaturation at the very surface, leading to mineral nucleation at the air–water interface, where the activation energy is lower.

Minerals doi: 10.3390/min16050443

Authors: Yajing Chen Hongying Yang Linlin Tong Guomin Chen Jianing Xu

Mechanically activated pyrite plays an important role in gold extraction and coal utilization, but its reactivity may change markedly during storage. This study investigates how air deactivation during storage affects the crystal structure and subsequent thermal decomposition behavior of mechanically activated pyrite. Pyrite was mechanically activated and then stored in air for 0, 7 and 180 days. X-ray diffraction (XRD) combined with Rietveld refinement was used to characterize variations in lattice parameters and unit-cell-related structural features, while non-isothermal thermogravimetric–differential scanning calorimetry (TG-DSC) under an argon atmosphere, together with the Flynn–Wall–Ozawa (FWO) method, was applied to evaluate the decomposition kinetics. Air deactivation induced a non-monotonic evolution of lattice parameters and unit-cell volume, which is attributed to combined effects of residual stress relaxation and air-induced surface-related modification during storage. All samples exhibited two mass-loss stages during heating, reflecting stepwise thermal decomposition, and their decomposition behavior varied systematically with deactivation time. The apparent activation energy depended on both conversion fraction and deactivation degree, and nucleation-and-growth-type mechanisms were found to dominate the decomposition process, with their relative contributions evolving with storage time. These results clarify how prior air-deactivation history influences the structural evolution and subsequent thermal decomposition behavior of mechanically activated pyrite and provide useful insight for its storage and utilization in related processes.

Minerals doi: 10.3390/min16050442

Authors: Yang Zhao Qian Wang Yongbing Li Yonghui Li Shanqi Liu

Chlorine (Cl) and sulfur (S) are two crucial mineralizing agents in silicate melts, and are closely related to the genesis of metallic mineral deposits. Magmatic ore deposits usually form in mafic–ultramafic silicate melts by the separation (liquation) of a cooling, sulfur-rich magma into two immiscible liquids. It is not easy to identify the complexation between gold (Au), cooper (Cu) and Cl, S using the current experiment methods, and the coordination of Au and Cu with Cl and S is still unclear in mafic–ultramafic silicate melts. In this study, by using first-principles molecular dynamics technique, we investigated the structure of Au, Cu, Cl and S in the (a) anhydrous and (b) hydrous peridotite melt to reveal their coordination geochemistry. Our results show that Si4+–Cl−, Cu+–O2−, Au+–O2−, Cu+–Cl−, Au+–Cl−, Au+–S2−, and Cu+–S2− cannot form stable ion pairs in silicate melts; therefore, Au+ and Cu+ cannot form stable complexes with S2−, O2− or Cl− in the melts. But the diffusion coefficients of Au+, Cu+, S2− and Cl−, their RDF values and the bonding time ratio of the silicate melt systems show that, although they cannot form stable complexes, within the range of effective chemical bond lengths, they have a high probability of approaching and interacting with each other, which enables them to form crystal embryos or liquid-phase molecules during magma evolution.

Minerals doi: 10.3390/min16050441

Authors: Debasis Golui Md. Raza Siba Datta Brahma Dwivedi Mahesh Meena Prasenjit Ray

The chemical equilibria of metal ions between soil solution and solid phases govern the solubility of metals in soil. However, the identity of these controlling phases remains poorly understood in historically polluted environments. This study aimed to identify the dominant mineral phases regulating the activities of Zn2+, Cd2+, Pb2+, and Ni2+ in soils subjected to long-term contamination from sewage sludge, municipal solid waste, river water, and industrial effluents across India. The soil samples were collected from various locations historically polluted by sewage sludge, municipal solid waste, polluted river water and industrial effluents. The free ion activities of Zn2+ (pZn2+), Cd2+ (pCd2+), Pb2+ (pPb2+) and Ni2+ (pNi2+) in soil pore water were estimated using the geochemical speciation model WHAM-VII. The metal ion activities were higher in industrial effluents and solid waste-treated soils as compared to other contaminated soils. The solubility of Zn and Cd in soils contaminated with Zn-smelter effluents was controlled by franklinite (ZnFe2O4) in equilibrium with goethite (α-FeOOH) and otavite (CdCO3), respectively. Identification of minerals further reveals that nickel ferrite (NiFe2O4) in equilibrium with lepidocrocite (γ-FeOOH) governs the activity of Ni2+ in cycle factory effluent-irrigated soils of Sonepat, Haryana. At the municipal solid waste-contaminated site, the Pb2+ activity was controlled by exchangeable Pb in soils, whereas Zn2+ activity was governed by willemite (Zn2SiO4) in equilibrium with quartz (SiO2). These findings provide new insights into mineralogical controls on heavy metal solubility under diverse contamination scenarios. Formation of highly soluble minerals like otavite, willemite, and nickel ferrite suggested the potential ecological risk of Cd, Zn, and Ni, respectively, in polluted soils.

Minerals doi: 10.3390/min16050440

Authors: Fatih Kaya

Industrial zinc borate is commonly produced through a hydrothermal process using boric acid and zinc oxide as raw materials. In this study, zinc borate was synthesized by replacing boric acid with borax ore and fresh water with borax plant wastewater in order to improve resource efficiency and water sustainability within an industrial symbiosis framework. Due to side reactions originating from borax, the reaction medium exhibited high ionic strength, and the synthesis was completed at 90 °C in approximately 5 h, slightly longer than conventional industrial processes. An additional washing step was applied to reduce impurities, resulting in a final impurity level of 2966 mg/kg, comparable to that of commercial zinc borate. The use of borax plant wastewater significantly reduced fresh water consumption. However, the formation of a by-product stream containing approximately 16% Na2SO4 may limit direct industrial applicability. If this sodium sulfate stream is valorized within an industrial symbiosis framework, zinc borate production from borax and wastewater could represent a cost-effective and sustainable alternative to conventional processes.

Minerals doi: 10.3390/min16050439

Authors: ElSayed A. Saber H. M. Hamouda A. S. Hamid Ahmed A. El-Sheikh

Arsenopyrite (FeAsS) is an important sulfide that holds gold in orogenic systems. Its arsenic content is often used as a proxy for gold fertility. However, arsenopyrite from the Um Rus gold deposit in Egypt’s Central Eastern Desert shows a complicated gold distribution that makes simple Au-As correlations hard to make. Integrated electron microprobe analysis (EMPA), laser ablation ICP-MS, and principal component analysis (PCA) reveal three unique textural and geochemical domains. Fine-grained arsenopyrite inclusions within pyrite aggregates (28–31 at% As) are devoid of detectable gold; PCA elucidates 84% of their variance through Fe–S versus Co-As substitution (PC1: 61.8%) and Pb-decoupled variability (PC2: 22.2%), suggesting crystallization from a Co-rich, Au-poor fluid. On the other hand, coarse oscillatory-zoned arsenopyrite can hold up to 6154 ppm of invisible gold. This is because of a moderate Au-As substitution (R = 0.41063, p = 0.08074) that was overprinted by a separate Au-Ag-Sb-Te hydrothermal pulse (Au–Ag: R = 0.97762; Au–Sb: R = 0.97608). PCA finds four parts (72.8% variance): Ag-Cu-As associations (PC1: 25.1%), Te versus Bi-Au signatures (PC2: 17.8%), Fe–S stoichiometry (PC3: 17.1%), and an Au versus Pb-decoupled event (PC4: 12.9%). This shows that minerals formed in more than one stage. Irregular As-rich overgrowths, containing ≤950 ppm gold and lacking significant Au–As correlation (R = −0.14011, p = 0.56726), show PCA (74.3% variance) that highlights S-As contrasts (PC1: 25.2%), Co-Ni enrichment (PC2: 18.8%), Cu-Fe-Ni associations (PC3: 16.2%), and a late Au-decoupled event (PC4: 14.2%), indicating barren recrystallization. These results show that just adding arsenic is not a good way to tell if gold is fertile. The highest amounts of invisible gold, on the other hand, are found in oscillatory-zoned domains with Ag-Sb-Te signatures. This research highlights the importance of combining PCA, geochemistry, and microtextures to differentiate auriferous from barren arsenopyrite, thereby enhancing exploration methodologies for structurally intricate orogenic gold systems.

Minerals doi: 10.3390/min16050437

Authors: Nicholas Machado Lima Rogério Guitarrari Azzone Lucas Martins Lino Anderson Costa dos Santos Thais Mothé Maia Leandro Arrais Bevilaqua Sergio de Castro Valente Gabriel Medeiros Marins Vincenza Guarino

The Abrolhos Magmatic Province (AMP), situated along the southeastern Brazilian passive margin, comprises a Paleocene–Eocene transitional basalt series of alkaline affinity. Despite the lack of mineral chemistry and thermobarometric estimates, it has long been linked to a classical deep-mantle plume model. This study integrates mineral chemistry, calculations of intensive parameters (P, T, H2O), geochronology, and geochemical modeling to evaluate an alternative explanation for AMP magmatism. Whole-rock and clinopyroxene compositions from different AMP localities are consistent with parental magmas derived from fertile, pyroxenite-enriched mantle sources that melted under ambient mantle potential temperatures (~1300–1400 °C). Inverse petrological modeling using alphaMELTS and MeltPT, together with trace-element systematics, suggests low degrees of partial melting within asthenospheric domains. These results indicate that shallow (upper-mantle) processes and high mantle fertility were important controls on melt generation. New 40Ar/39Ar ages of 24.3–28.4 Ma for southern AMP rocks are also difficult to reconcile with a simple age-progressive evolution of the previously proposed plume model. Taken together, the data support ambient-temperature melting of a fertile mantle as a plausible explanation for Abrolhos magmatism and reduce the need to invoke a classical high-temperature mantle plume as the sole model. Here, we favor a tectonically controlled model, involving localized shallow mantle processes such as edge-driven convection and/or lithospheric delamination as triggers for intraplate magmatism along the South Atlantic margins.

Minerals doi: 10.3390/min16050438

Authors: Aolin Pan Aimin Du Tiebing Liu Changhao Li

The West Junggar region in Xinjiang, NW China, hosts more than 100 gold deposits, most of which are shallow and nearing depletion. To assess deep mineralization potential, we integrated in situ sulfur isotope geochemistry with audio-frequency magnetotelluric (AMT) surveys at three representative deposits (Hatu, Baogutu, and Baogutu XI). Sulfide δ34S values (0.46–4.16‰) indicate a deep magmatic–hydrothermal source. Petrophysical measurements reveal systematic resistivity contrasts that correlate with sulfide content. AMT surveys effectively delineate low-resistivity anomalies corresponding to mineralized zones, with persistent anomalies extending beneath known orebodies and along fault belts. These anomalies display two distinct geometric patterns: steeply dipping faults with en echelon fractures (Hatu) and S-shaped dip-transition zones (Baogutu and Baogutu XI), both reflecting structural controls on mineralization. The identified anomalies define probable mineralized zones at depth, suggesting significant undiscovered potential. This integrated geochemical and geophysical evidence provides compelling targets for deep exploration in the West Junggar region.

Minerals doi: 10.3390/min16050436

Authors: Zhentang Wang Peng He Chuangang Zhong Baojun Yang Rui Liao Yang Liu Jun Wang Guanzhou Qiu

Aiming at the significant variation in clay content within the orebody of the Letpadaung copper mine in Monywa, Myanmar, this study conducted comprehensive research on ore classification based on clay content and its impact on bio-heap leaching performance. Pressure filtration tests confirmed that clay content is a critical factor affecting ore permeability and copper leaching efficiency. Accordingly, a classification standard centered on clay content was established based on the ore properties of the Letpadaung Copper Mine, categorizing the ore into four types: low-clay ore (<3%), medium-clay ore Type 1 (3%–10%), medium-clay ore Type 2 (10%–25%), and high-clay ore (>25%). Corresponding differentiated stacking strategies were proposed and applied for the first time in industrial operations at a scale of several hundred thousand tons. Industrial practice results demonstrated that, compared with the unclassified mixed ore with a leaching efficiency of 45.92%, the implementation of classified heap leaching increased the copper leaching rates of low-clay ore and medium-to-high-clay ore to 68.07% and 63.41%, respectively. Moreover, multi-layer heap leaching within the same leaching unit showed consistent leaching efficiency across different layers after ore classification. These results further validate that ore classification based on clay content combined with differentiated heap leaching processes serves as a vital technical approach for ensuring efficient and stable heap leaching operations at the Letpadaung copper mine.

Minerals doi: 10.3390/min16050435

Authors: Lichun Fu Guihu Chen He Yuan Yingzheng Pei Qiang Wei Fangyue Wang Ahmed S. Moftah

The Dongwujiiazi deposit is a structurally controlled orogenic gold deposit situated in the eastern part of the Chifeng–Chaoyang gold belt along the northern boundary of the North China Craton. This study establishes a comprehensive metallogenic model for the Dongwujiiazi gold deposit by integrating whole-rock geochemistry (major and trace elements), in situ trace elements and REEs in zircon, multi-isotope systems (H, O, S, Pb), and precise zircon U–Pb geochronology. Five types of intrusive and associated rocks are identified within the main biotite-pyroxene gneiss host of the Dongwujiiazi gold deposit: mylonitized granitic pegmatite, mylonitized porphyritic monzogranite, propylitized fine-grained quartz monzodiorite, quartz monzonite, and porphyritic dolerite. The gold-bearing polymetallic sulfide ores are composed of pyrite, chalcopyrite, sphalerite, galena, digenite, and native gold. Zircon grains in the Dongwujiiazi gold ore (2502 ± 15 to 2539 ± 18 Ma) are inherited from surrounding Neoarchean gneiss, recording older crustal sources rather than forming contemporaneously with the gold mineralization. H–O isotopes indicate that the ore-forming fluids were mixed in origin, involving both magmatic and metamorphic components. S and Pb isotopes suggest that the mineralizing sulfur was mainly derived from a magmatic source, while lead originated predominantly from lower crustal materials associated with the surrounding high-grade metamorphic rocks. In this study, we present a new metallogenic model for the Dongwujiiazi gold deposit, in which slab-derived and lower-crustal metamorphic fluids interacted with ascending magmas, resulting in fluid mixing and gold precipitation within structurally controlled zones of gneissic host rocks. Combined geochemical and isotopic evidence (H–O, S, Pb) indicates contributions from both magmatic and metamorphic sources, supporting formation as an intracontinental orogenic gold system in an active continental margin.

Minerals doi: 10.3390/min16050434

Authors: Nazym Akhmadiyeva Yerkezhan Abikak Raigul Ramazanova Nurzhan Orakbay Rinat Abdulvaliyev Nurila Burabayeva Tangsholpan Sagyntayeva Valeriy Pozmogov

The efficient processing of nepheline ores and red mud requires mineralogical preconditioning strategies that enhance aluminum recovery while controlling the potassium behavior in alkaline systems. In this study, carbonate–hydrothermal activation of a nepheline ore–red mud mixture (1:1 mass ratio) was investigated as a targeted approach for phase redistribution prior to alkaline leaching. Thermochemical activation in NaHCO3 solution at 260 °C resulted in the partial destabilization of primary aluminosilicate phases and the formation of secondary carbonate-bearing and hydroxide phases. Quantitative phase analysis revealed the formation of cancrinite (~19 wt.%) and boehmite (~2.8 wt.%), indicating dissolution–reprecipitation processes accompanied by aluminum redistribution and carbonate incorporation. A two-stage alkaline leaching process with controlled calcium addition was applied to evaluate the effect of phase transformation on the extraction performance. The activated material exhibited enhanced reactivity, resulting in an alumina recovery of 92%–94% and selective potassium removal of 82%–87%. The results demonstrate that carbonate–hydrothermal activation acts as an effective mineralogical preconditioning strategy, transforming structurally stable aluminosilicates into more reactive phases. The proposed approach provides a basis for improving the efficiency and selectivity of integrated alumina recovery from complex aluminosilicate raw materials and industrial waste.

Minerals doi: 10.3390/min16050433

Authors: Yulong Cen Feng Zhang Xianghong Jiang Zhuowei Lei Zichun Chen

Pelletizing is an effective way of converting abundant phosphate ore fines into usable feedstocks for yellow-phosphorus production. In this work, the oxidation-roasting behavior of siliceous–calcareous phosphate ore pellets and siliceous phosphate ore pellets was evaluated in a laboratory tube furnace. The consolidation mechanisms were revealed using optical microscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results indicate that siliceous phosphate ore pellets exhibit superior oxidation-roasting performance relative to siliceous–calcareous phosphate ore pellets. After roasting, oxidized siliceous–calcareous phosphate ore pellets show a loose and porous framework with large pores, thin walls, and occasional surface cracking. The consolidation of siliceous–calcareous phosphate ore pellets is mainly governed by the recrystallization bonding of silicon–magnesium-bearing fluorapatite. In contrast, oxidized siliceous phosphate ore pellets display a denser microstructure and stronger intergranular bonding. The dominant bonding forms are the recrystallization bonding of silicon-bearing fluorapatite and solid-state bonding between silicon-bearing fluorapatite particles and quartz particles. Furthermore, carbonate gangue minerals are detrimental to strength development because CO2 release during roasting promotes the development of interconnected porosity and defects, thereby reducing the compressive strength of oxidized phosphate ore pellets.

Minerals doi: 10.3390/min16050431

Authors: Maryam Osali Farid Ahani Mohammad Reza Aboutalebi Mandana Adeli Javad Moghaddam Saeid Karimi Janaka Jayamini Wijenayake Lana Alagha

Limonitic laterites typically contain low Ni and Co contents and significant impurities, making the development of technical and economically feasible processes challenging. To address this challenge, this study investigates and evaluates an integrated hydrometallurgical process comprising sulfation roasting, water leaching, and solvent extraction (SX) for the selective recovery of Ni and Co from limonite-type laterite. Response Surface Methodology coupled with a Central Composite Design (RSM-CCD) was employed as a statistical experimental design tool to efficiently optimize the sulfation roasting conditions. Under the optimal sulfation roasting conditions (temperature 703 °C), selective leaching efficiencies of 87.2% for Ni and 96.6% for Co were achieved, with only 3.8% Fe co-leaching. A multi-stage SX scheme was subsequently applied to purify the pregnant leach solution (PLS) of water leaching. In the first SX step, D2EHPA at pH 2.8 selectively removed more than 95% of the impurities, including Mn, Zn, Al, Ca, and Fe. In the second SX step, Cyanex 272 at pH 5.8 enabled the extraction of more than 99.9% of Co and 86.0% of Mg into the organic phase, and Ni remained in the raffinate. Subsequent stripping with H2SO4 enabled the recovery of 99.9% of both Co and Mg from the loaded organic phase. Finally, selective carbonate precipitation is proposed as a potential downstream recovery method for Ni after enrichment. This approach is considered relatively less energy-intensive than sulfate crystallization. The process developed in this study was benchmarked against similar processes reported in the literature, and a conceptual flowsheet for the selective extraction and separation of Ni and Co from limonitic laterite was proposed. Findings demonstrated the feasibility of the integrated sulfation roasting-water leaching, solvent extraction process for treating impurity-rich laterite leach solutions.

Minerals doi: 10.3390/min16050432

Authors: Yizhe Hu Teng Deng Lin Cai Huirao Sun Hongmei Tang Xin Wei Longyue Zhou Weizheng Su Lingdong Xu Miao Zheng

The Xiangshan ore field is characterized by extensive alkali metasomatism, which represents the early-stage hydrothermal event before the acidic metasomatism during major U mineralization. However, the mineralogical and geochemical characteristics of alkali metasomatism, as well as its association with uranium mineralization, remain poorly understood. This study evaluates these scientific problems by conducting petrographic and geochemical analyses on feldspar, together with thermodynamic modeling. Hydrothermal feldspars are present as veinlets, differing from the magmatic ones with granular and subhedral structures. Hydrothermal albites have lower Na but higher K content than magmatic ones, while hydrothermal K-feldspars have lower K but higher Na content than magmatic ones. In addition, hydrothermal feldspars are significantly depleted in Ca and Sr, likely associated with the consumption of Ca in fluids by fluorite and calcite precipitation. Furthermore, alkali metasomatism is accompanied by intense hematitization, indicating the oxidized properties of ore fluids that are favorable for uranium transport. Thermodynamic modeling further demonstrates that continuous K+ consumption during fluid–rock interaction leads to a pH increase in the fluid, which is buffered by quartz–muscovite–K-feldspar (QMF). Given that quartz solubility is positively correlated with pH, this process induces extensive quartz dissolution in the host rocks. Such dissolution significantly enhances the porosity and permeability of the host rocks, creating ideal physical traps for the subsequent accumulation of uranium-bearing fluids. Consequently, alkali-metasomatized rocks associated with quartz dissolution and hematitization serve as critical indicators for regional uranium exploration.

Minerals doi: 10.3390/min16040430

Authors: Kuan Lu Jiakai Hou Zhenkai Huang Guangyou Zhu Jianyong Liu Jiangna Fu Heting Gao

The Mahu Sag, a hydrocarbon-rich depression within the Junggar Basin, hosts significant petroleum resources. Here, the Permian Fengcheng Formation shale oil reservoirs have emerged as a primary exploration target. This study investigates fracture development within these alkaline lacustrine shales, a critical factor governing hydrocarbon migration and accumulation. Through integrated petrographic and geochemical analyses, we elucidate a multifactorial fracture formation mechanism driven by the interplay of alkaline minerals, stress, and fluids. Two distinct fracture types were identified: bedding-complex fracture veins (BCFVs) and Y-shaped high-angle fracture veins (Y-HFVs). Both fracture types result from alkaline fluid–rock interactions, which induce fracture opening along specific orientations, alter fracture angles, and control aperture width and final morphology. Alkaline mineral assemblages further influence fracture evolution via dissolution–precipitation cycles. Concurrently, these assemblages preserve hydrocarbons by inhibiting the thermal maturation of organic matter, as evidenced by variations in fluid inclusion fluorescence. The fracture networks act as crucial migration pathways, with the BCFV containing higher-maturity hydrocarbons (indicated by blue-green fluorescence) and the Y-HFV retaining less mature fluids (indicated by yellow-green fluorescence). This study presents the first systematic characterization of the multifactorial controls on fractures in alkaline lake environments, proposing a cooperative “alkaline minerals–stress–fluids” mechanism. These findings provide a new framework for understanding fracture development in alkaline lacustrine shales and offer valuable insights for shale oil exploration in analogous depositional settings.

Minerals doi: 10.3390/min16040429

Authors: Yanlin Zhang Wenyi Liang Yunzuo Lei Zhen Zhou Jun Zhou Zhen Yao Qifan Zhong Fuzhong Wu

Leaching carbon residue (LCR) is a carbonaceous solid waste generated during the hydrometallurgical recycling of spent lithium-ion batteries. Although its high graphite content offers substantial potential for resource recovery, the residual heavy metals and fluorides present in LCR pose considerable environmental risks. Currently, LCR has not garnered sufficient attention within the industry, and the lack of recycling technologies suitable for large-scale disposal results in resource wastage and environmental pollution. To address these challenges, this study proposes an innovative strategy based on the concept of multi-field synergistic enhancement. The proposed approach involves recovering and regenerating graphite (RG) from LCR via low-temperature molten salt roasting assisted by high-pressure and mechanical activation. A combination of advanced characterization techniques was employed to compare the physicochemical properties of RG and commercial graphite (CG) and to systematically evaluate the technical feasibility of using regenerated graphite as an anode material for lithium-ion batteries. The results demonstrate that, under optimized molten salt roasting and aqueous leaching conditions, the carbon content of RG reaches 99.94 wt%, indicating the efficient removal of non-carbon impurities from the graphite matrix. Compared to CG, RG retains a typical layered structure; however, a lower carbon content (99.94 wt%) and poorer structural order (ID/IG = 0.30) are observed. In terms of electrochemical performance, RG delivers a discharge specific capacity of 394.64 mAh/g during the first cycle and exhibits excellent cycling stability, with a capacity retention of 86.50% after 100 cycles. This electrochemical performance is comparable to that of commercial graphite. The proposed multi-field-assisted low-temperature molten salt roasting technique enables the efficient recovery of high-value graphite resources from LCR, establishing a full-lifecycle recycling strategy tailored for lithium-ion battery applications.

Minerals doi: 10.3390/min16040428

Authors: Martin Köhler Percy Clark Jiří Zachariáš Andreas Knobloch

Fuzzy logic-based mineral potential mapping was applied to the Tisová–Klingenthal Cu–Co VMS deposit (Erzgebirge) in the Czech–German border region. The study area is characterized by heterogeneous geological and geochemical datasets derived from differing national surveys and historical mining. Using the Exploration Information System (EIS) toolkit, a knowledge-driven fuzzy logic approach integrated key spatial datasets, including copper and zinc soil and stream sediment anomalies and metabasalt lithology, relevant to Besshi-type VMS deposits. Three prospective anomalies were identified: the historic Tisová mine and two additional targets aligned along the same stratigraphic horizon. Artificial Neural Network (ANN) modelling was limited by insufficient training data, resulting in overfitting and reduced predictive reliability. Follow-up soil geochemical surveys conducted over the largest anomaly returned locally elevated copper values but did not conclusively confirm mineralisation. The results demonstrate that fuzzy logic provides a flexible and interpretable framework for mineral potential mapping in complex, data-scarce environments and highlight the need for iterative modelling and targeted exploration.

Minerals doi: 10.3390/min16040427

Authors: Anja Ilenič Petra Vrhovnik Sonja Lojen Matej Dolenec

Revitalisation of contaminated brownfield sites is essential for sustainable development, particularly near sensitive ecological areas like Natura 2000 sites. The lagoon in Slovenia’s Regional Park Šturmovci, an artificial wastewater convergence point created during hydroelectric construction, is a highly relevant example. This study integrates geochemical, mineralogical and isotopic analyses to identify sources and controlling mechanisms of contaminant distribution in lagoon sediments and assess their transfer to nearby agricultural soils during flooding events. Results indicate anaerobic conditions, with depth-related shifts in phosphorus, sulphur and redox-sensitive elements, such as rare earth elements (REE), arsenic (As), barium (Ba), cobalt (Co), chromium (Cr), lead (Pb) and vanadium (V), as well as fluctuations in pyrite-rich laminated layers, suggesting potential flood-driven remobilisation of trace elements. Lagoon sediments are highly contaminated with As (73 mg kg−1), Ba (247 mg kg−1), Pb (97 mg kg−1) and Zn (1118 mg kg−1), with elevated concentrations also observed in agricultural soil, all exceeding respective limit values of 20, 160, 85 and 200 mg kg−1. Pollutant concentrations were highest near wastewater inflows and decreased with distance, with nitrogen isotopic patterns indicating partial nitrification and surface ammonium accumulation, reflecting intensive agricultural inputs in the area. High enrichment factor (EF > 20) and geoaccumulation index (Igeo > 3) values, in particular for As, Cd and Zn, indicated severe contamination and highlighted the urgent need for effective remediation strategies, including immobilisation using biochar or cement-based binders, as well as phytoremediation approaches.

Minerals doi: 10.3390/min16040426

Authors: Kent Benedict Aleonar Salisid Raul Lucero Reymarvelos Oros Mylah Villacorte-Tabelin Theerayut Phengsaart Shengguo Xue Jiaqing Zeng Ivy Corazon A. Mangaya-ay Takahiko Arima Ilhwan Park Mayumi Ito Sanghee Jeon Carlito Baltazar Tabelin

The conservation of tuff- and coral rock-built architectural heritage structures (AHS) is challenging because access to original tuff and coral rock has become difficult and severely limited due to urbanization, land reclamation, the depletion of stone quarries, anti-mining and anti-quarrying legislation. An emerging approach to address this issue is to create compatible “replacement” rocks via geopolymerization, a process that is more sustainable and greener than the use of conventional cement and concrete. To explore the potential of geopolymers for AHS conservation strategies, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented; 103 eligible articles were identified and classified into geopolymers for AHS (34 articles), tuff-built AHS (60 articles), and coral rock-built AHS (9 articles). Tuff substrates in AHSs appear in a variety of colors (yellowish-brown, grayish-cream, reddish-brown, pale greenish-gray and pink hues), densities (1.0–2.5 g/m3), and compressive strengths (3–100 MPa). Meanwhile, coral rock substrates in AHSs appear in whitish-cream color and are coarse-pored (1–5 MPa), fine-grained (8–15 MPa), and calcarenite (50–60 MPa). In terms of geopolymer formulation, metakaolin was reported as the most popular main precursor or admixture, while NaOH and Na2SiO3 were used simultaneously as alkaline activators. Aggregates used in geopolymer formulations depended on local availability, including quartz sand, river sand, crushed stones, carbonate stones, volcanic rock, volcanic sand, tuff, brick, ceramic tiles, and waste materials. Aesthetics, chemical composition, physical attributes, and mechanical properties have been identified as key criteria to ensure geopolymer compatibility for AHS conservation application. To date, geopolymers have been applied for AHS conservation as repair mortars, consolidants (i.e., grout and adhesives), and masonry strengthening (i.e., fiber-reinforced mortar). Finally, geopolymers formulated for AHS conservation have similar durability as the original substrate based on accelerated aging tests (i.e., salt mist, wet-dry, and freeze–thaw) and long-term outdoor exposure experiments.

Minerals doi: 10.3390/min16040425

Authors: Keting Fan Gang Gao Xiaobing Jiao Xinsong Wu Miao Yu Zhehui Jin Jilun Kang Youjin Zhang Xiongfei Xu Qiang Ma

A climatic transition from arid to humid conditions occurred during the deposition of the Permian Pingdiquan Formation in the Shishugou Sag, Junggar Basin, Northwest China. This study reconstructs the paleoenvironmental evolution and organic matter (OM) enrichment mechanisms recorded in six stratigraphic intervals, with emphasis on the two oil shale units formed during the transgressive system tracts (TST1 and TST2). Geochemical, elemental, and biomarker data reveal that climate, salinity, and redox conditions fluctuated significantly and jointly governed OM enrichment, with paleoclimate acting as the primary background control by regulating lake hydrology, salinity, and preservation. During the early stage (SQ1), an arid climate prevailed, the TST1 oil shale formed during a transient freshening event in a deep stratified lake. Dominant algal productivity and minimal terrigenous input favored excellent preservation, yielding the highest TOC and superior hydrocarbon potential. In contrast, during the humid stage (SQ2), the TST2 oil shale was deposited in a moderately deep, weakly reducing, and slightly saline lake. Although preservation was less efficient, enhanced primary productivity under humid conditions compensated for OM loss, producing abundant but slightly lower quality OM. These results establish two depositional models, an arid freshening model (TST1) and a humid salinization model (TST2). Both transient freshening under arid conditions and salinization during humid periods facilitated the accumulation of organic-rich source rocks through different balances between productivity and preservation. This highlights the complex response of lacustrine source rock development to climatic variability. The occurrence of similar organic-rich source rocks can be anticipated under comparable paleoenvironmental transitions, particularly in saline lakes characterized by frequent fluctuations in water salinity and paleoclimate.

Minerals doi: 10.3390/min16040424

Authors: Run Cao Fuwei Xie Ming Jia Yang Cao Lutong Gao

The peripheries of rare-metal metallogenic systems frequently host skarn-type or hydrothermal vein-type Pb-Zn deposits, though their genetic connections with parental systems remain debated. The newly identified Gariatong W-Mo polymetallic metallogenic system in the Lhasa Terrane displays well-defined Nb-Ta-Rb, Mo-W, W-Mo, W-Bi, and Pb-Zn-Ag metallogenic zoning, establishing it as an exemplary site for investigating genetic relationships between Pb-Zn and rare-metal mineralization. This investigation targets skarn-type Pb-Zn deposits spatially associated with rare-metal orebodies at Gariatong, utilizing integrated analytical approaches, including in situ LA-ICP-MS trace-element analysis of sulfides, sulfur isotope geochemistry, and LA-ICP-MS elemental mapping of sphalerite, to constrain metal sources, characterize fluid evolution, and establish genetic correlations with the rare-metal system. Key findings include the following: (1) sphalerite shows enrichment in Fe, Mn, Co, and Cd, while pyrite contains elevated As, Pb, Co, Cu, and Mn. Fe, Cd, and Mn primarily occur as solid solutions or nanoparticles, whereas As and Pb exist as micro-inclusions. (2) Sphalerite Zn/Cd ratios (73.6–184) and Co-Ni-As ternary diagrams confirm a magmatic–hydrothermal skarn origin. (3) Mineralization occurred under moderate-temperature, mildly oxidized conditions, as constrained by sphalerite Fe contents and mineral assemblages. Sulfur isotope compositions (δ34S = −1.0‰ to 3.2‰; mean: 1.9‰) indicate a magmatic sulfur source. This study reveals that the Nb-Ta-Rb mineralization, quartz-vein- and greisen-type W-Mo deposits, and skarn-type Pb-Zn orebodies—all genetically associated with highly fractionated granites—constitute an integrated magmatic–hydrothermal system with vertical (depth-related) zoning relative to the granitic intrusion. These results provide critical constraints for understanding rare-metal–Pb-Zn genetic associations and suggest that Pb-Zn mineralization may serve as a key exploration indicator for rare metals in the Lhasa Terrane.

Minerals doi: 10.3390/min16040423

Authors: Sheng Lu Tao Liu Tiesheng Li Hongpeng Chen Qingyuan Song Zhengbo Zang Wenlong Li

The northern part of the Great Xing’an Range in China hosts a prominent Au mineralization belt, where Mesozoic clastic rock-hosted Au deposits represent the mineralization type. A study of the Baoxinggou Au deposit in this region might provide new perspectives on the mineralization mechanisms of these Mesozoic clastic-rock-hosted Au deposits. This study investigated the age of mineralization, origins and evolution of the ore-forming fluids, and sources of the ore-forming materials in this deposit. Rubidium–Sr dating of sulfides yielded a mineralization age of 119 ± 2 Ma. Fluid inclusion analyses revealed that the ore precipitated from fluids with temperatures of 105–415 °C and salinities of 4.3–8.8 wt.% NaCl equivalent. Hydrogen and O isotopic data show that the ore-forming fluids were of magmatic origin and, during mineralization, the proportion of meteoric waters increased gradually and eventually dominated the late mineralization stage. Fluid mixing was the primary ore-forming mechanism. Sulfur isotopic data for pyrite and chalcopyrite (δ34SV–CDT = −4.35‰ to −0.91‰) and Pb isotopic ratios (206Pb/204Pb = 18.429–18.477; 207Pb/204Pb = 15.581–15.591) indicate the ore-forming materials were magmatic in origin, with a similar source as an Early Cretaceous diorite and mixed crust–mantle materials. The results indicate the Baoxinggou Au deposit is a magmatic–hydrothermal deposit.

Minerals doi: 10.3390/min16040422

Authors: Zhuo Chen Jiajia Yang

The performance of remote sensing-based mineral alteration extraction is significantly restricted in the vegetation area. Spectral unmixing is one of the effective methods to address the vegetation problem during mineral alteration extraction. However, the spectral curves of different tree species vary a lot; if multiple tree species are regarded as a whole during the spectral unmixing stage, the proportions of vegetation would be estimated with more errors. The purpose of this study was to verify the effects of dominant tree species classification on spectral unmixing and reconstruction, and to apply the proposed method to the mineral alteration extraction practice. To accomplish this, the Shabaosi gold deposit region in Mohe City, China, with an area of 650 km2, was selected as the study area. Firstly, reference spectral curves, GaoFen-1/6 (GF-1/6) satellite imageries, ZiYuan-1F (ZY-1F) satellite imageries, Sentinel-1B satellite synthetic aperture radar (SAR) data, the ALOS digital elevation model (DEM), and sub-compartment dominant tree species data were collected; subsequently, simulated mixed-pixel reflectance images of ZY-1F, reflectance images of GF-1/6, ZY-1F, backscattering data of Sentinel-1B, slope, aspect, and 5484 tree species samples were derived from the collected data. Secondly, to verify the effect of dominant tree species classification on mineral alteration extraction, the reference spectra of pine, oak, goethite, and kaolinite were used to construct a simulated ZY-1F mixed-pixel image, and spectral unmixing and reconstruction experiments were conducted. Thirdly, fourteen independent variables were selected from the derived data, five dominant tree species classification models were trained and tested using tree species samples via the ResNet50 algorithm, and the pine- and birch-dominated parts were segmented from the ZY-1F images. Fourthly, minimum noise fraction (MNF), pixel purity index (PPI), n-dimensional visualizer auto-clustering, and spectral angle mapper (SAM) methods were separately applied to the pine- and birch-dominated parts of ZY-1F images to extract and identify endmembers; subsequently, the fully constrained least squares (FCLS) and linear spectral unmixing (LSU) methods were separately applied to the pine- and birch-dominated parts to estimate endmember proportions and generate spectrally reconstructed ZY-1F images. Fifthly, the pine- and birch-dominated parts of spectrally reconstructed ZY-1F images were mosaiced, and the SAM was utilized to extract mineral alteration in the study area. The result showed that in the spectral unmixing and reconstruction experiment, the spectral reconstruction error declined from 0.0594 (simulated ZY-1F image without segmentation) to 0.0292 and 0.0388 (simulated ZY-1F image that was segmented by pine- and oak-dominated parts), suggesting that dominant tree species classification could improve the accuracy of spectral unmixing and reconstruction and help obtain a more reliable mineral alteration extraction result. In the study area, the tested overall accuracies (OA) and Kappa coefficients of the five dominant tree species classification models were 0.75 ± 0.03 and 0.50 ± 0.05, respectively, suggesting that conducting dominant tree species classification was feasible in dense vegetation areas and could facilitate mineral alteration extraction. After segmenting the ZY-1F image by pine- and birch-dominated parts and spectral reconstruction, eight main types of alteration, including kaolinite, vesuvianite, montmorillonite, rutile, limonite, mica, sphalerite, and quartz, were identified, and nine mineral alteration areas (MA) were delineated accordingly.

Minerals doi: 10.3390/min16040420

Authors: Yin Liu He Zhang Shengtang Zhang Lingran Min Hao Fang Hongru Rui Hao Li

In order to explore the outstanding problems, such as poor mechanical performance, of recycled aggregate from construction waste in the application of backfills, this study innovatively used accelerated carbonation treatment technology to pretreat the recycled aggregates, and systematically investigated the evolution of mechanical properties in carbonated recycled aggregate-based cemented paste backfill (CPB). By carbonizing the waste recycled concrete aggregate (RCA), carbonation recycled concrete aggregates (CRCA) were obtained, and coal gangue was replaced as the filling aggregate at 50% and 100% for mine paste filling. The mechanical properties of the CPB were measured, and the mechanism was analyzed in combination with the changes in the microstructure. The results showed that the physical properties of RCA were significantly improved by carbonation treatment compared with untreated raw RCA: the apparent density of C60d-RCA increased by 2.88% relative to non-carbonated RCA, while its crushing value decreased by 51.45%, resulting in a more stable aggregate structure. In terms of mechanical properties, the compressive strengths of the 28day carbonated backfills with 50% and 100% CRCA contents (denoted as C28d-RCA-50 and C28d-RCA-100) reached 6.38 MPa and 5.32 MPa, representing increases of 61.52% and 46.33%, respectively, compared to the control group. Microstructure and phase composition analysis showed that the carbonation reaction not only produced calcium carbonate (CaCO3) crystals to effectively fill the internal pores and reduce the total porosity of the matrix, but also promoted the generation of monocarboaluminate and provided abundant nucleation sites for calcium silicate hydrate (C-S-H) gel hydration, which significantly optimized the structure of the interfacial transition zone (ITZ) and improved its microhardness. Among all test groups, the CRCA-50 group showed the most optimized microstructure and the best mechanical properties. This study provides a theoretical reference for the resource utilization of this type of 30-year service life RCA in mine filling.

Minerals doi: 10.3390/min16040421

Authors: Zaijia Zhang Xiaogang Guo Peiqing Hu Bo Mai Zhuang Wu

The Huoyanshan Cu-Zn volcanogenic massive sulfide (VMS) deposit, located in the North Qilian Orogenic Belt, China, is of significant economic importance. This study provides new constraints on the ore-forming processes through high-resolution in situ trace element and sulfur isotope analyses of pyrite and sphalerite using LA-(MC)-ICP-MS. Petrographic and geochemical investigations identified three distinct generations of pyrite (Py l to Py III). Early-stage Py I and Py II are characterized by high trace element contents (Au, As, Bi, Cu, Pb), elevated Co/Ni ratios (>1–10), and enriched δ34S values (+4.98‰ to +7.47‰). These signatures indicate precipitation from high-temperature, reduced magmatic–hydrothermal fluids influenced by thermochemical sulfate reduction (TSR). Late-stage Py IIl exhibits markedly lower Co/Ni ratios (<0.1) and lighter δ34S values (+3.72‰ to 3.89‰). This geochemical shift reflects a transition toward a cooler, more oxidized environment driven by the incursion and mixing of ambient seawater as the hydrothermal system waned. Trace element geochemistry of sphalerite reveals an average crystallization temperature of 265.8 °C (derived from the “GGIMFis” geothermometer), consistent with fluid inclusion data and representing a thermal “snapshot” of the waning hydrothermal stage. Systematic discriminant analysis using Ga/In, Ge/In, and Co-Ni-As systematics further confirms a strong magmatic–hydrothermal affiliation.

Minerals doi: 10.3390/min16040419

Authors: Hao Jiang Rui Jiang Yanling Xu Xin Teng Yanhong Wang

The concentration of inevitable ionic species in regenerated water significantly alters the flotation characteristics of rare earth minerals, thereby hindering the effective extraction of bastnaesite. Therefore, it is of great significance to study the influence and mechanism of inevitable ions on the flotation of bastnaesite. This paper systematically investigated the effects of Ca2+, Mg2+, and Fe3+ on the flotation behavior of bastnaesite using a BHA/OHA combined collector system and studied the mechanism of action using contact angle testing, Raman spectroscopy, and Visual MINTEQ solution chemistry calculations. The results showed that the BHA/OHA combined collector had good collecting performance for bastnaesite, while Ca2+, Mg2+, and Fe3+ all had varying degrees of inhibitory effects on its flotation, with the order of influence being Fe3+ > Mg2+ > Ca2+. Contact angle tests showed that the presence of inevitable ions weakened the effect of the combined collector on improving the hydrophobicity of the bastnaesite surface. Raman spectroscopy results indicated that inevitable ions interfered with the adsorption of the combined collector on the mineral surface, with Fe3+ having the most significant effect. Solution chemistry analysis further demonstrated that Ca2+ and Mg2+ have been the primary ions influencing flotation because of their interactions with the mineral surface and collector molecules, but not Fe3+, which is mainly adsorbed on the mineral surface in the form of hydrolyzed species, thereby inhibiting the reagent adsorption and enhancing the surface hydrophilicity. Based on this, this paper revealed the differentiated interference mechanisms of different inevitable ions on the flotation of bastnaesite, and applied the relevant insights to guide the recovery of rare earth resources in molybdenum tailings, providing a theoretical basis and new research ideas for the flotation control of bastnaesite and the efficient utilization of rare earth resources under complex backwater conditions.

Minerals doi: 10.3390/min16040418

Authors: Luigi Jovane Carina Ulsen Douglas Galante Simone Bernardini Natascha Menezes Bergo Elisabete de Santis Braga Frederico P. Brandini Ronaldo Carrion David Lopes de Castro Renata R. Constantino Muhammad Bin Hassan Valdecir de Assis Janasi Izabel King Jeck Luciano de Oliveira Junior Marco Antonio Couto Junior Fabiola A. Lima Simone Marques Gustavo M. Massola Nelia C. C. Mestre Webster Mohriak Eduardo F. Monlevade Carina Costa de Oliveira Vivian Helena Pellizari Marcelo Cecconi Portes Adriane G. P. Praxedes Fabio Rodrigues Lucas C. V. Rodrigues Francisco Javier González Sanz Ilson C. A. da Silveira Jules M. R. Soto Pedro Walfir Souza-Neto Paulo Y. G. Sumida Gabriel T. Tagliaro Solange Teles da Silva Alexander Turra Roberto Ventura Santos Marcio Yamamoto Sidney L. M. Mello

The Rio Grande Rise (RGR) is the largest oceanic plateau in the South Atlantic and represents a key natural laboratory for understanding oceanic plateau formation, deep-sea circulation, ecosystem functioning, and ferromanganese crust development. This study presents a critical synthesis of current scientific knowledge on the RGR, integrating geological, geophysical, oceanographic, biological, and geochemical evidence published over the last two decades. Geophysical data reveal a complex tectono-magmatic evolution involving Late Cretaceous plume-related volcanism, crustal thickening, rifting, and subsequent subsidence. The structural framework of the plateau is dominated by the Cruzeiro do Sul Rift, which plays a central role in controlling sedimentation, magmatism, and seawater circulation. Oceanographic studies demonstrate that the interaction between the southern branch of the South Equatorial Current and the complex topography of the RGR generates intense internal tides and bottom currents, strongly influencing sediment transport and benthic habitats. Biological investigations indicate that the RGR hosts diverse deep-sea communities, including sponge grounds, cold-water corals, and associated fauna, whose distribution is tightly linked to geomorphology and hydrodynamics. Ferromanganese crusts occurring on the plateau preserve valuable geochemical records of oceanographic and redox conditions, although their spatial distribution, thickness, and metal budgets remain incompletely constrained. Despite major advances, significant knowledge gaps persist regarding crustal structure, sedimentary evolution, ecosystem functioning, and mineral formation processes. This review highlights these uncertainties and outlines research priorities necessary to improve understanding of oceanic plateaus and deep-sea systems in the South Atlantic.