Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data were used to investigate structural features and hydrothermal alteration zones for mineral exploration in the Precambrian basement of the Bou Azzer–El Graara inlier, located in the Moroccan Central Anti-Atlas. This domain, recognized as a Pan-African suture zone, contains a complex accretionary mélange of arc-related terranes and dismembered supracrustal ophiolites hosting economically significant mineralizations such as Co, Au, and Cu. Its arid setting offers favorable conditions for satellite remote sensing to detect lineaments and alteration patterns indicative of potential metal resources.

To refine structural mapping of the study area, key lineaments were extracted from ASTER data and compared with existing geological interpretations. The identified NE–SW and E–W fault families are consistent with previous tectonic studies, confirming their strong control on the spatial distribution of mineralization. In addition, previously unmapped faults were revealed, requiring further field verification but providing valuable insights into the region’s complex geodynamic evolution. Many of these structures correspond to faults reactivated during the Pan-African, Variscan, and Alpine–Atlas tectonic events.

In the second part of this study, ASTER surface reflectance data were used to map hydrothermal alteration zones through targeted band ratios, enabling the identification of iron oxides, hydroxyl-bearing minerals, sulfates, and carbonates. When combined with available geochemical information, the results show that cobalt anomalies correlate with carbonate–chlorite–epidote alteration, gold anomalies with alunite–kaolinite–pyrophyllite and locally sericite–muscovite–illite–smectite assemblages, and chromium and nickel anomalies with both carbonate–chlorite–epidote and sericite–muscovite–illite–smectite alteration types.

Overall, this integrated approach improves structural and alteration mapping and provides valuable guidance for future mineral exploration in the Bou Azzer–El Graara inlier.

Grinding operations play a pivotal role in enabling the effective separation of minerals, as it directly dictates the degree of mineral liberation and a critical prerequisite for subsequent beneficiation processes. In this study, a combination of advanced analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), and the Advanced Mineral Identification and Characterization System (AMICS), was employed to systematically investigate four key aspects: (1) the mineral composition of the raw ore, (2) the grain size distribution of valuable minerals, (3) the degree of ionization, and (4) the intracrystalline relationships of titano-magnetite with other coexisting phases. The results indicated that titano-magnetite exhibits a strong associative relationship with gangue minerals (e.g., chlorite, pyroxene, and amphibole). This intimate association causes complete dissociation of titano-magnetite from gangue minerals to be challenging during grinding. Consequently, gangue minerals are prone to entrainment in the iron concentrate alongside titano-magnetite, which subsequently compromises the quality of the final iron concentrate. Based on the aforementioned mineralogical characteristics of titano-magnetite, the high-speed stirred mill was used to achieve the ultra-grinding of titano-magnetite and optimize operation parameters. The optimal grinding conditions were ultimately determined as follows: stirred speed of 2000 r/min, grinding concentration of 35%, feeding frequency of 5 Hz, and media filling ratio of 70%. Under these optimized conditions, an optimized magnetic separation process to improve the recovery of high-content iron concentrates from titano-magnetite was performed, eventually allowing the iron grade to reach 56.25%. This study provides crucial insights into addressing the issue of complex titano-magnetite, and the optimized grinding-magnetic separation process proposed herein offers theoretical and technical guidance for scaling up beneficiation operations in industrial settings, thereby facilitating the sustainable utilization of titano-magnetite resources.

Abstract

Determining the horizontal position of magnetic anomalies is essential for interpreting subsurface geological structures in geophysical exploration. Although numerous edge-detection techniques exist for outlining anomaly boundaries, many still struggle with issues such as false edge generation, poor resolution, and high noise sensitivity. This study introduces a new high-resolution approach that combines the Skewed-Sigmoid (Skewed-Sig) function with the Total Horizontal Gradient (THG) to overcome these limitations. The Skewed-Sig function resembles the commonly used arctangent operator found in many edge-detection filters, while the THG is a standard technique that often lacks sufficient edge-resolution when used alone. By integrating these two components, we develop a hybrid filter—referred to as SSF—that enhances the detection of mineralized targets. To evaluate the performance of the proposed SSF filter, we compare it with widely used methods, including the analytical signal (AS), THG, tilt angle (TA), theta map (TM), and total horizontal gradient of the tilt angle (TAHG), using a synthetic magnetic model with a complex subsurface structure. To create synthetic conditions that were close to the real world, noise was added to the model data, and the quality of the output maps was checked. The filter was then applied to magnetic data from the Shavaz iron deposit in Yazd Province, Iran. The study area lies within the Central Iran Block, a region that is known for its significant potential for iron mineralization, particularly hematite and magnetite. Our results demonstrate that SSF delineates the mine location with greater accuracy than traditional methods and shows strong agreement with existing geological information and previous investigations in the Shavaz region. Consequently, the SSF technique offers a reliable tool for detecting mineral deposits and other subsurface magnetic sources.

This study aims to optimize the comminution process in light of the characteristics of fine embedded size and easy sliming of valuable minerals in complex rare-earth ores to achieve efficient grinding of the complex rare-earth ore. Firstly, taking a rare-earth ore from China as the research sample, the process mineralogy and crushing working index tests were conducted to explore the properties of the ore. Subsequently, crushing tests were conducted respectively using jaw crushers, double-roll crushers and high-pressure grinding rolls, and grinding tests were conducted using ball mills and rod mills. The particle size distribution, the liberation degree of gangue minerals and the microscopic morphology of different products were compared and analyzed. Finally, magnetic separation test was carried out, and the magnetic separation performance and energy consumption of different grinding products were compared and analyzed. The results show that HPGRs have higher crushing efficiency and produce more suitable particle size distribution of the product. Rod mills have the selective grinding effect on coarse-grained particles and the selective protection effect on fine-grained particles, which can effectively reduce mineral sliming formation and increase the recovery of the magnetic separation process under the similar concentrate grade. This research has certain guiding significance for solving the crushing and grinding problems of complex rare-earth ores, and can provide a reference for the efficient development and utilization of this ore type.

Phosphate mining activities generate enormous quantities of calcite-rich residues whose management poses both environmental and economic challenges, largely due to their low reactivity and limited industrial value. In this work, a sustainable valorization route is proposed to transform this carbonate waste into feed-grade calcium phosphates while simultaneously capturing carbon dioxide in a stable mineral form. The process is based on a two-step chemical pathway integrating alkaline conversion and phosphate synthesis.

In the first stage, the calcite-dominant residue was subjected to alkaline activation using sodium hydroxide (NaOH), leading to the in situ generation of calcium hydroxide [Ca(OH)₂] and sodium carbonate (Na₂CO₃). The reaction parameters were systematically optimized through a statistical design of experiments combining Plackett–Burman screening with a central composite design. Among the tested factors, NaOH concentration, solid-to-liquid ratio, and reaction time were identified as the most influential variables. The optimized conditions (7.95 mol L⁻¹ NaOH, 75 °C, S/L = 4.28 g per 50 mL, and 26 min) resulted in a conversion yield of 88%, confirming the spontaneous and exothermic character of the process (ΔG ≈ −58 kJ mol⁻¹; ΔH ≈ −59 kJ mol⁻¹). Sodium carbonate was recovered by crystallization from both the filtrate and washing effluents, achieving an average recovery of 86%, equivalent to the sequestration of approximately 0.33 t of CO₂ per ton of calcite treated.

The second step involved the neutralization of the Ca(OH)₂-rich product with phosphoric acid, enabling the controlled precipitation of monocalcium phosphate (MCP) or dicalcium phosphate (DCP) depending on the targeted Ca/P molar ratio. X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS) confirmed the formation of well-crystallized, pure calcium phosphates exhibiting high solubility in 2% citric acid (>90%), in accordance with international feed additive standards.

Brannberget is found close to the world-famous Løkken volcanogenic massive sulfide deposit (VMS), within the Løkken Ophiolites, Central Norwegian Caledonides (Grenne, 1989). Based on the Norwegian Geological Survey database, the study area represents a minor sulfide-quartz-bearing mineralization. Despite the historical mining activity at this location, no modern studies have been reported.

Field observations, petrographic investigations, mineral chemistry, and preliminary whole-rock geochemistry analyses were performed to characterize this mineralization. A network of ~3-5 cm thick quartz veins with Fe-oxyhydroxide and clay mineral-bearing alteration halo forms stockwork mineralization in the metabasaltic–doleritic greenstone. This rock is altered to albite, sericite, chlorite, and quartz. The quartz veins also contain iron-rich clay minerals, K-feldspar, disseminated pyrite, and chalcopyrite. The geochemical data revealed elevated concentrations of Cu (~ 7270 ppm), Zn (~236 ppm), and Bi (~ 74 ppm) in the quartz vein-bearing rock, compared to the host greenstone.

The observed mineral assemblage reveals high-temperature albitization, followed by intensive chloritization and lower-temperature silicification and sericitization as the fluid cooled owing to water–rock interaction. This multi-stage hydrothermal evolution, the appearing sulfides, and the observed geochemical data are typical of VMS stockwork feeder zones. Therefore, our study provides insights into the deep stockwork zones of this Ordovician VMS system. Further study is suggested to better understand the critical raw material potential of the locality, as our results prove that this stockwork zone might contain promising Cu amounts.

Acknowledgement

Sabina Strmić-Palinkaš, Máté Biró, and Tibor Németh are thanked for fruitful fieldwork conversations, SEM-EDS, and XRD analysis support, respectively. The ELTE Talent Fund supported the fieldwork.

Reference

Grenne, T. (1989): Econ Geol, 84/8: 2173-295

Compression of particles to a fixed final gap is the mode of application of stresses in many crushing devices. Understanding and modeling this particle fracture process is indispensable for comminution operations. The present work is based on detailed compression tests conducted with five different ores to which different deformation ratios are applied to characterize their size-dependent fracture energy distribution and progeny size distribution. An energy-based model is proposed to describe single-particle breakage by compression based on three modes, which define whether the particle is classified for breakage (classification function), the likelihood that the classified particle is sufficiently nipped to break (breakage probability), and the extent of breakage the particle will undergo (breakage distribution). Expressions that allow the calculation of the energy absorbed by the particle in both primary and secondary breakage are proposed by explicitly accounting for particle thickness, stiffness, and the fixed applied final gap. Model verification is demonstrated, with the model predicting the breakage response and energy consumption for single-particle compression experiments performed on a bench-scale with all materials investigated. The validation of the model is shown by accurately predicting, without any fitting, the progeny size distribution and overall energy consumption of compression using fixed gaps and breakage in a double roll crusher.

Fehrite (MgCu₄(SO₄)₂(OH)₆·6H₂O) from the Casualidad mine (Sierra de Alhamilla, Almería, Spain) was described in 2021 as a new member of the ktenasite group. This secondary sulphate had been previously found in the Les Ferreres mine (Rocabruna, Ripollès, Catalonia, Spain) in 2012 and was reported by amateur collectors as a potential new mineral. The available samples, however, still lack a formal characterization. The aim of the present work is to investigate the fehrite from Les Farreres, which contains light green to bluish-green aggregates of very elongated tabular crystals of the mineral, typically forming parallel to radial acicular clusters. It occurs in association with brochantite, devilline, gypsum, and minor connellite, among others. SEM–EDS, Raman spectroscopy, and X-ray diffraction (XRD) data confirm that these crystals correspond to fehrite with the empirical formula Mg₀.₇₇Cu₃.₃₉Zn₀.₆₁S₂.₀₈O₈(OH)₆·nH₂O on the basis of 20 O atoms per formula unit, consistent with Mg dominance at one of the cation sites, Cu at the two other sites, and Zn in substitution of both Mg and Cu cations. The refined monoclinic unit-cell parameters (s.g. P2₁/c) are a = 5.626 Å, b = 6.137 Å, c = 23.861 Å, β = 95.21°, and V = 820.5 ų, which closely match the published data for the type material. The paragenesis of fehrite from Les Ferreres is also discussed and compared to that of the type locality.

The Tamdroust copper deposit, located in the Bou Azzer–El Graara inlier (central Anti-Atlas, Morocco), is hosted in Lower Cambrian carbonate–siliciclastic formations. Copper mineralization is structurally controlled by an N110°–N150° fault system and occurs mainly within greenish siltstones and dolostones deposited in a shallow marine platform setting influenced by terrigenous deposits. Two mineralization styles are recognized: disseminated sulfides in host rocks and vein–veinlet stockworks along fracture corridors. Three paragenetic ore stages are distinguished: (1) early disseminated and veinlet-type bornite–chalcopyrite–pyrite associated with quartz–calcite; (2) hydrothermal enrichment along fault zones marked by the replacement of bornite by chalcocite, together with digenite and covellite; and (3) supergene weathering producing native copper and secondary carbonates (malachite, azurite, tenorite). Sulfur isotope data (δ³⁴S ≈ +10.2‰) indicate a dominant contribution from thermochemical reduction of evaporitic sulfates. Carbon and oxygen isotopes in calcite (δ¹³C = –3.6 to –2.6‰ VPDB; δ¹⁸O = –15.8 to –15.2‰ VPDB) suggest hydrothermal fluids at moderate temperatures (~150–160°C) derived from mixed meteoric–basinal brines. The spatial distribution of mineralization reflects redox-controlled precipitation at the interface between oxidized hematite-rich red beds and reducing green siltstones and carbonates. These results support a model of epigenetic, stratabound copper mineralization formed during Hercynian tectonic reactivation of Cambrian carbonate–evaporite sequences. The Tamdroust deposit shares strong similarities with Jbel N’Zourk and Jbel Laassal, providing a predictive analog for regional exploration targeting redox interfaces and structurally focused brine pathways.

We studied the specific effects of NaCl, KCl, MgCl₂ and CaCl₂ on the ability of sodium dodecyl sulfate (SDS) to inhibit the coalescence of the bubbles in water and to make foam. We related our observations with the thermodynamic data about the activities of the salts and water using the model of Pitzer for each particular salt. Moreover, we measured the surface tension of each particular foaming solution, which allowed us to calculate the adsoprtion parameters of SDS in the presence of the different salts. All these allowed us to look at our main experimental data from different perspectives. As we have expected, the addition of each one of the salts to the aqueous solution of SDS significantly decreased its critical coalescence concentration (CCC). Yet their effects on the ability of SDS to make foam were various. For example, NaCl significantly increases the foaming ability of SDS, while KCl acts as foam suppressor. MgCl₂ boosts the ability of SDS to make foam, while CaCl₂ appears to be foam suppressor. Sodium (Na) and Potassium (K) belong to the 1A group of the Mendeleev’s periodic table, while magnesium (Mg) and calcium (Ca) belong to the 2A group. Sodium (Na) is a foam booster, while potassium (K) is a foam suppressor. Magnesium (Mg) is a foam booster while calcium (Ca) is a foam suppressor. The two pairs of chemical elements have identical electronic configurations in their last electronic layers. The only difference between them is in the radii of their atoms. This difference draws difference in their ionization potentials, polarizabilities, hydration numbers and all related thermodynamic parameters. We developed a detailed analysis, thus drawing the conclusion that the larger counter-ions act as flocculants of the surfactants, thus becoming foam suppressors, while the smaller ions act as foam boosters.