Predicting mineral liberation during comminution remains a key factor in optimizing the processing of Critical Raw Materials (CRMs). This study presents a modeling system that couples a Roll crusher’s breakage Model B with Gaudin’s statistical liberation model to predict the liberation behavior of Cu, Zn and Pb sulfide ores. The main objective is to establish a predictive framework linking a roll crusher’s operating parameters to crushing modeling, enhancing our understanding of the relationship between comminution and liberation, with potential application to other types of materials.

The quartered Run-of-mine (ROM) material was characterized using Particle Size Distribution (PSD), X-ray diffraction (XRD), X-ray fluorescence (XRF), chemical analysis, and automated Mineral Liberation Analysis (MLA) to establish a quantitative mineralogical baseline. The ROM was split into two fractions: particles smaller and larger than 1250 μm. Liberation characteristics were evaluated for the undersize fraction, while the oversize material was subjected to comminution using a roll crusher. Comminution tests were conducted under controlled conditions, including compressive force, throughput, roll speed, and feed PSD. Models were calibrated with experimental data to simulate particle breakage using MATLAB® scripts, and MLA measurements of the crusher’s product were used to validate model predictions by quantifying the resulting mineral liberation.

The ROM material showed that 55% of chalcopyrite, 36% of sphalerite, and 40% of galena were liberated. Comminuted material showed a liberation degree of 42% of chalcopyrite, 33% of sphalerite, and 31% of galena. Through the model verification, the results prove the potential of the induced liberation by roll crusher, reducing the volume of material which requires further grinding in downstream comminution stages while maintaining comparable mineral liberation.

The proposed coupled modeling and validation framework could provide a foundation for predictive mineral processing techniques which target energy efficiency and improve the recovery of critical raw materials.

Understanding how quartz microfractures heal under hydrothermal conditions is crucial for constraining the evolution of permeability, fluid flow, and gold mineralisation in orogenic systems. Early experimental studies established that microfracture healing in quartz is a thermally activated, diffusion-controlled process governed by silica transport and influenced by temperature, fluid chemistry, and fracture geometry. Recent advances combining microstructural observations and phase-field modelling have revealed the cyclic nature of fracture-healing and its feedback on permeability. However, the quantitative relationships between temperature, fluid chemistry, and fracture geometry that control sealing rates remain poorly constrained. To address these issues, we conducted high-temperature (500–650 °C), high-pressure (1.5–3.6 kbar) hydrothermal experiments on quartz in sulphur-rich fluids, integrated with correlation analysis and reactive-transport modelling. The results show that healing time decreases markedly with increasing temperature and increases with fracture width, indicating that thermal activation accelerates silica mass transfer, while wider fractures heal more slowly. Mixed HS⁻–Cl⁻ fluids promote the fastest sealing, followed by sulphur- and chloride-rich systems, whereas CO₂-bearing fluids retard healing owing to lower silica reactivity. Numerical simulations using COMSOL Multiphysics reproduce these trends, showing that quartz precipitation under a pressure gradient causes porosity loss, permeability reduction, and localised fracture sealing. To complement these experiments, Gaussian Process Regression modelling was developed to predict gold solubility in H₂S-rich fluids as a function of temperature, pressure, and HS⁻ concentration, revealing solubility maxima above 600 °C at moderate HS⁻ levels (~0.1–0.2 mol kg⁻¹). Together, these results demonstrate that temperature and fluid composition jointly control quartz sealing and gold transport, emphasising the thermally and chemically driven nature of hydrothermal sealing and episodic mineralisation in orogenic systems.

Djerfisherite (K(Na,Cu)₆(Fe,Cu,Ni)₂₄S₂₆Cl) is a potassium-bearing sulfide mineral that occurs in a variety of reducing, alkaline geological settings, including enstatite chondrites, kimberlites, and alkaline–ultramafic complexes. Its complex chemistry, marked by extensive isomorphic substitution among Fe, Cu, and Ni, as well as solid-solution relationships with related minerals like bartonite (KFe₃S₄), renders it a valuable petrogenetic indicator. However, the genetic mechanisms of djerfisherite—whether formed during high-temperature magmatic processes or via lower-temperature fluid-mediated reactions—remain uncertain. To address this, we conducted high-pressure experiments to simulate djerfisherite formation during mantle metasomatism. Using a gas bomb apparatus, we reacted a sulfide mixture (pyrite/chalcopyrite/pentlandite in 5:1:2 ratio) with K–Cl–rich aqueous fluids at 5 kbar and 600°C for 7 days. Two fluid compositions were tested, differing in KCl:K₂CO₃ ratios (1:1 and 1:2). In the 1:1 series, products included potassium carbonates, sulfate glass, iron oxide, residual KCl, and minor, non-stoichiometric sulfides with bartonite-like compositions (KFe₃S₄). Two generations of pyrite were observed, with later grains enriched in Cu and K. In contrast, the 1:2 series yielded potassium sulfides with compositions intermediate between bartonite and djerfisherite, forming a continuous solid-solution series and containing 1–3 wt.% Ni—evidence of substantial elemental substitution. This shift correlates with higher carbonate activity, which promotes djerfisherite stabilization. Our results demonstrate that djerfisherite can crystallize during late-stage, fluid-driven mantle metasomatism through interaction between primary mantle sulfides and K–Cl–CO₃–rich fluids. Critically, the KCl:K₂CO₃ ratio governs sulfide phase stability: carbonate-rich fluids favor djerfisherite, while chloride-dominated fluids stabilize bartonite-like phases. These findings support a fluid-mediated origin for djerfisherite in kimberlites and underscore the role of fluid composition in controlling sulfide mineral assemblages in the Earth’s mantle.

Funding: Supported by state contracts of the Institute of Experimental Mineralogy RAS (FMUF-2022-0001) and the Institute of Geochemistry and Analytical Chemistry RAS (FMMZ-2024-0056/0030).

The Ity gold deposit (Ivory Coast) records two successive mineralising events: an early skarn-related hypogene stage, overprinted by supergene alteration under tropical weathering conditions ~2 Ga later. Gold at Ity occurs within skarns developed at contacts between carbonate-rich Birimian volcano-sedimentary rocks and felsic intrusions, whereas at the nearby Dahapleu prospect, mineralisation is structurally controlled within shear zones. Gold is present as native gold in pyrite and as Bi–Te–Au–Ag tellurides.

The hypogene Ity system reflects a long-lived thermal anomaly driving fluid circulation and metal deposition through successive favourable events—crustal exhumation, granite intrusion and skarn formation, followed by shear deformation and hydrothermal activity. Fluid inclusion data indicate thus that Ity was formed through a hybrid system: a mesothermal orogenic gold event (>350 °C, CO₂–CH₄ fluids) overprinting an earlier saline skarn stage. At Dahapleu, volatile-rich inclusions (CO₂, CO₂–CH₄, CO₂–N₂) reflect metamorphic fluids circulating through fault-controlled, convective systems. The Ity–Dahapleu system thus exhibits fluid characteristics typical of mesothermal orogenic deposits, albeit at higher temperatures than most Birimian gold systems, but the lower temperature stages yield to the Au-Bi-Te assemblage.

Subsequent tropical weathering and karst development during the Cenozoic generated residual gold enrichment within saprolite and laterite, forming the supergene ore blanket currently mined. Contrasting supergene behaviours between skarn- and diorite-derived ores result from marble dissolution, sulphide oxidation, and collapse brecciation. Kaolinite–goethite assemblages dominate lateritic zones, while smectite typifies saprolitic and marble-derived domains. Gold enrichment is accompanied by Cu, Bi, Mo, and W anomalies, highlighting selective metal mobility during supergene alteration.

Iron (hematite) ore bodies that are enclosed within protore banded iron formations (BIFs) can form through supergene, hypogene, or combined supergene—hypogene processes. In the Soudan mine, located in the Lake Vermilion-Soudan Underground Mine State Park, high-grade hematite ores (>60 wt% Fe) occur as hard ore bodies in folded and faulted Neoarchean Algoma-type BIF within the Soudan Iron Formation member of the Ely Greenstone Formation. Upgrading of the BIF by hydrothermal fluids led to the genesis of the replacement-style iron ores, and hypogene alteration is coeval with distant Paleoproterozoic orogenic events (Mazatzal and Yavapai orogenies). Examples of other, globally significant, high-grade and hypogene hematite ore bodies include the ones within the Carajás Mineral Province, Brazil, and the Mount Tom Price of the Hamersley Province in Pilbara, Australia.

This study utilizes iron stable isotopes (δ⁵⁶Fe) to distinguish Fe sources necessary for the upgrade process. Hematite, magnetite, and coexisting silicates from surface and subsurface samples were analyzed to fingerprint Fe provenance and hydrothermal system(s). Samples include variably altered BIFs, hematite ore with different textures, and adjacent altered wall rocks. Results show δ⁵⁶Fe values ranging from approximately –0.4‰ to +1.3‰. Our results show that Fe in hematite is systematically lighter as a function of alteration; hematite in least altered BIF is heaviest and hematite formed as replacement in iron ore is lightest. Therefore, replacement hematite likely formed from fluid-derived Fe as opposed to residual Fe from BIF. We interpret hydrothermal fluid origin with heavy Fe sourced from BIF and light Fe sourced from deep-seated crustal hydrothermal fluids. We further explore whether a single hydrothermal system operated, or overprinting events produced composite ores by proposing a hydrothermal genetic model associated with iron ore formation at our research locality.

The Dugald River Zn-Pb-Ag, Mary Kathleen U-REE, and Tick Hill Au deposits are distributed in the Mary Kathleen Domain (MKD), Mount Isa Inlier, Australia. Investigating the magmatic-hydrothermal processes in this region is a key step toward a better understanding of how these deposits formed. Previous studies have established the zircon ages and distribution of magmatic rocks in this region (Spence et al., 2022; Cocker et al., 2025). However, the timing of skarn formation has received limited attention, despite its critical role as an indicator for mineral deposits.

Most of the intrusions in MKD have been grouped into several igneous provinces, which include the Kalkadoon–Leichhardt (ca. 1870-1850 Ma), Argylla (ca. 1780-1775 Ma), Wonga (ca. 1760-1730 Ma), Burstall (ca. 1750-1710 Ma), and Williams (ca. 1550-1500 Ma). We collected skarn samples of the Burstall and Wonga granites (19°45'35" S, 147°08'46" E). The garnet crystals within the calcite matrix commonly exhibit distinct diopside rims in these skarns. QC-04 garnet was used as the primary reference material (130 Ma; Deng et al., 2017), and data reduction was performed on the Isoclock software (Liu et al., 2023) to calculate the garnet U-Pb age. The garnet dating (n = 14) yielded a weighted mean age of 1754.2 ± 13.9 Ma (MSWD = 1.2) and a concordant age of 1758.2±13.5 Ma (MSWD = 0.39). Therefore, we interpret that the formation of the sampled skarns is primarily related to the Wonga or Burstall magmatic event (Page, 1983). Based on the degree of discordance observed in zircon (Spence et al., 2022), we propose that the chronological constraints on regional geological processes can be further refined by conducting geochronology of U-rich minerals such as garnet in regional skarns.

The modification of mineral surface properties during comminution plays an important role in determining subsequent flotation behavior. This study compares the surface characteristics and flotation performance of hematite ore products obtained from two comminution circuits: semi-autogenous grinding plus ball milling (SAG + BM) and high-pressure grinding rolls plus tower milling (HPGR + TM). SAG products with a P95 of 1 mm were collected from an operating concentrator and further ground in a laboratory ball mill, while run-of-mine ore was processed by HPGR to the same P95 and subsequently milled in a tower mill to an equivalent final fineness. Particle size distribution, microcrack development, and surface morphology were characterized using laser particle sizing, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. Surface roughness and specific surface area were quantified by root mean square (RMS) roughness Rq, power spectral density (PSD), and Brunauer–Emmett–Teller (BET) analyses.
Results indicate that HPGR + TM products exhibit a higher density of intra- and intergranular microcracks, increased surface roughness, and larger BET surface areas compared with SAG + BM products. Flotation tests show that the HPGR + TM circuit produced a concentrate with 64.62% TFe at a recovery of 85.06%, while the SAG + BM circuit achieved 61.71% TFe at 86.10% recovery. These correspond to a measurable improvement in concentrate grade of approximately 2.9 percentage points under the investigated conditions. The observed difference is associated with comminution-induced surface modification, which may improve particle hydrophobicity and bubble–particle attachment behavior.
Overall, the study highlights the coupling between comminution-induced surface characteristics and flotation response, emphasizing the importance of considering interactions between interconnected processes at the flowsheet level. Further statistical validation is required to fully quantify the observed performance difference and to support process-scale optimization.

The present study aims to study the communition characteristics of two difficult grindable low-grade iron ores of Sandur, Karnataka, South India. The two iron ore samples (Ore 1, Ore 2) were collected from different mines of the Sandur region of South India. The vast availability of low-grade ores and rising global consumption of iron and steel create the demand to process the low-grade ores of this area to meet the margins of steel industries, which in turn increases the attention on comminution studies as they are difficult to grind due to their fine liberation size and high energy consumption rate. Thus, it is important to optimize the grinding circuit with accurate models; predicting industrial mill performance models requires experimentally determined breakage parameters, with these values being established by laboratory tests.

An attempt is made to study the comminution characteristics of two ores by evaluating the energy consumption using the Standard Bonds Work index test followed by comparative studies of the jaw and roll crusher performance. The results revealed that the experimental and predicted values aligned well overall, suggesting the CEP model used for predicting crushing efficiency is reasonably accurate. Also, an attempt is made to Develop T-family curves using a single-particle breakage test with the standard Drop Weight Test to evaluate the relationship between the impact energy and particle size distribution.

The findings provide valuable insights for optimizing crushing and grinding operations across different ore types.

The Roc Blanc polymetallic vein deposit is located in the NW of Marrakech, in the Variscan Central Jebilet massif, and is closely associated with the contact metamorphic aureoles produced by S- and I-type calc-alkaline granitic intrusions (ca. 330–295 Ma) along the Marrakech Shear Zone. The mineralized veins are hosted by Carboniferous black shales and metavolcaniclastic formations metamorphosed from greenschist to amphibolite facies. Ore assemblages are dominated by Pb-Zn-Ag sulfides and sulfosalts, with late gold occurring as electrum intimately intergrown with multiple sulfide generations. Hydrothermal alteration is characterized by silicification, sericitization, chloritization, and carbonatization. Chlorite and arsenopyrite geothermometry yield temperatures of ~350-364 °C, consistent with a metamorphic origin of the mineralizing fluids. Oxygen, lead, and strontium isotopic signatures further indicate that ore-forming metals and sulfur were largely sourced from the enclosing metamorphic host rocks during granite emplacement and devolatilization of carbonaceous sediments.

Two major stages of ore deposition are distinguished. The pre-ore stage (Stage I) includes two quartz-rich vein generations carrying Fe-As-Zn-Cu sulfides. The main ore stage (Stage II) is enriched in Ag-Au-Pb-Zn-Cu-Sb and is hosted within carbonaceous veins and late quartz generations. Fluid-inclusion studies identify three fluid types: (i) liquid-rich H₂O-N₂-CH₄±CO₂, (ii) vapor-rich H₂O-CO₂-CH₄-N₂, and (iii) aqueous H₂O-salt inclusions. These data reflect the mixing of deep metamorphic fluids with surface to subsurface aqueous fluids, locally trapped under boiling conditions. Stage I mineralization formed at 350 ± 20 °C with salinity around 13.7 wt% NaCl eq., whereas the economically significant argentiferous stage precipitated at ~150 °C with salinity of 12.1 wt% NaCl eq. All ore deposition occurred at relatively low pressure (<1–1.1 kbar). Overall, cooling and dilution of the hybrid fluid system represent the key mechanisms driving Ag-rich polymetallic mineralization at Roc Blanc.

The NE Estonian Precambrian basement, comprising the Tallinn, Alutaguse, and Jõhvi zones, is part of the eastern Fennoscandian Shield. It comprises Paleoproterozoic back-arc basins with juvenile metal-rich volcanic–sedimentary sequences intruded by Svecofennian granitoids, forming an amphibolite- to granulite-facies basement whose lithological and metallogenic traits resemble those of the Swedish Bergslagen region and the Finnish Orijärvi district.

This study re-examines over 500 historical drill cores and related geophysical data to reassess the mineral potential of the NE Estonian basement. Cu–Zn–Pb and Au–Ag–As–Sb anomalies are linked with magnetite-rich and sulphide–graphite gneisses, while automated MSCL-XYZ scanning of archived drill cores uncovers multiple critical-metal associations, including Ni–Co–Cr, Mo–W–Bi, Sn–Zn–Cd, Cu–Ni, Nb–Y–P, and Au–Ag–As–Sb–Bi–W–Se–Sn. These patterns reveal previously unrecognised prospective intervals across the Tallinn, Alutaguse, and Jõhvi zones.

A compositional geostatistical workflow was applied to legacy geochemical data. Exploratory tools—such as box plots, concentration maps, and Q–Q plots—were used on raw data, while centred log-ratio (clr) transformation improved signal coherence and interpretative clarity. Clr-based maps, PCA, and heat maps help reduce artefacts caused by heterogeneous sampling, analytical variability, and mismatched neighbouring map sheets, enabling more reliable spatial interpretation.

Lithologies from historical drill cores, often unclassified or inconsistently documented, were re-evaluated using major-element data, with trace-element data reassigned based on the Tallinn–Alutaguse–Jõhvi basement-domain architecture. Combining these geochemical reclassifications with gravity and magnetic data refines the petrotectonic framework of NE Estonia and strengthens links to South Svecofennian and Bergslagen mineral systems.

Collectively, these geochemical, geostatistical, and geophysical findings offer an updated metallogenic model and highlight new targets for critical raw materials within the Horizon Europe DEXPLORE program.