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.

This project investigates the recovery of residual platinum-group metals (PGMs) from mine tailings by diagnosing froth-flotation constraints and defining a rigorous optimization pathway. Tailings from the PGM mining operation were sampled across the dam; the material was air-dried, crushed to ≤2 mm, riffle-split, and characterized for particle-size distribution. Mineralogical studies were conducted by XRD, and chemical composition was assayed by ICP-OES to inform the reagent strategy. The feed is ultra-fine, with a particle size of 78.6 % passing 75 µm. Baseline rougher flotation employed a 42 % w/w pulp with isobutyl xanthate as collector, X3-DEP as depressant, sodium silicate as dispersant, copper sulphate as activator, and X2-froth as frother under controlled aeration. Product streams were filtered, weighed, and assayed for PGMs and Cr₂O₃ to compute mass pull, grade, and recovery. Results show pronounced sensitivity to feed characteristics and operating variability. Across tests, increasing mass pull increased recovery but diluted concentrate grade, evidencing gangue entrainment; conversely, higher grades were obtained at lower mass pull with associated recovery penalties. Monitoring of Cr₂O₃ in the concentrate constrained mass pull to meet smelter compliance. These inverse grade–recovery responses are consistent with ultra-fine feeds, surface oxidation of PGM minerals, and froth drainage constraints. Performance differences were attributed to reagent dosage and pH control, conditioning and residence time, and hydrodynamics. The recommended pathway is a constrained operating window centered on ~42 % solids, with reagent set points and control loops for pH and dosing, explored via designed experiments spanning collector/frother dosages, air rate, and conditioning time. Feed-grade variability should be dampened by blending to stabilize head grade and mineralogy. Where mineralogical analysis confirms locked PGMs or oxide coatings, targeted ultrafine grinding in inert media and/or tertiary scavenging circuits may be justified on a cost-normalized metal basis. Consequently, the study confirms technical feasibility but emphasizes process-control rigor to achieve predictable recovery from tailings and to manage the grade–recovery–mass-pull variables.

Silica nanoparticles (nano-SiO₂) are essential in applications such as environmental
remediation, agriculture, and catalysis. They are synthesised from high-grade quartz, tetraethyl
orthosilicate (TEOS), and other costly and non-renewable precursors. The high cost of these
conventional silica precursors limits the sustainability of their large-scale production. Therefore,
identifying alternative, low-cost, and abundant silica sources is crucial to improving the economic
feasibility of nano-SiO₂ synthesis. This study explored the utilisation of plagioclase minerals
contained in abundance in a South African Bushveld Igneous Complex (BIC) mine residue as an
alternative, low-cost silica source for the synthesis of high-purity nano-SiO₂. The sample
contained 65.4 wt.% plagioclase, 15.5 wt.% clinopyroxene, 10.4 wt.% orthopyroxene, 5.1 wt.%
clinochlore, and trace amounts of other minerals. Its major chemical components were SiO₂
(47.6 wt.%), Al₂O₃ (18.4 wt.%), Fe₂O₃ (12.3 wt.%), CaO (9.2 wt.%), MgO (3.9 wt.%), and Na₂O (3.3
wt.%).
A multi-stage synthesis route was developed. It consisted of a calcination pretreatment step
which was designed to convert soluble iron-bearing minerals into insoluble iron oxides, followed
by direct acid leaching, precipitation, and surfactant-assisted refinement. The resulting silica
nanoparticles were characterised using X-ray diffraction (XRD), scanning electron microscopy
(SEM), transmission electron microscopy (TEM), inductively coupled plasma optical emission
spectroscopy (ICP-OES), and Brunauer–Emmett–Teller (BET) surface area analysis. The
integrated calcination–leaching–precipitation process enabled the successful formation of high-purity
(99%), predominantly amorphous nano-SiO₂ with controlled spherical morphology, a
primary particle size below 50 nm, and a high specific surface area of 576 m²/g.
These results highlight the untapped potential of plagioclase in mine tailings and other mineral-related
solid waste as a strategic feedstock for high-purity silica nanoparticles. This offers a
sustainable alternative to conventional silica precursors used today.

Rare earth elements (REEs), which are found and produced in only a limited number of countries worldwide, are projected to be insufficient to meet the growing global demand in the near future. This situation has prompted increasing interest in alternative production routes from secondary geological sources with low uranium (U) and thorium (Th) contents. Among these, ionic clays, red mud, fly ash, bauxite, and related ores have emerged as promising potential sources. In particular, bauxite and its associated ores are considered significant secondary geological resources due to their relatively high REE concentrations.

In this study, the recoverability of REEs and aluminum (Al) from high-silica bauxite ore that cannot be processed by the Bayer method was investigated. The Kemiklitepe bauxite ore (Karaman, Türkiye), characterized by its high silica content and appreciable REE concentrations, was evaluated as a potential alternative source of these critical materials. A novel and sustainable process was developed for the simultaneous recovery of Al and REEs through an alkali roasting–acid leaching route. The finely ground ore was alkali-roasted with Na₂CO₃ at 800–1000 °C, followed by a two-step leaching procedure involving water and sulfuric acid (H₂SO₄). Acid leaching achieved a total REE recovery of approximately 87%. Subsequently, the selective extraction of REEs and Al from the pregnant acidic leach solution was investigated using the solvent extraction (SX) method. Key operational parameters including extractant (D2EHPA) concentration, reaction time, pH, and organic-to-aqueous phase ratio were optimized using the Taguchi design method. The results demonstrate that the proposed process enables efficient and environmentally sustainable recovery of both Al and REEs from high-silica bauxite, highlighting its potential for resource diversification and zero-waste processing.