Search Results (618)

Fresh flotation tailings represent an underutilized archive of mineralogical and geochemical information in which multiple strands of evidence for ore-forming processes and post-depositional modification can be preserved. Detailed characterization of tailings is also vital for assessment of their future potential as a secondary source of recoverable by-products. This study investigates residual mineral speciation and mineral distributions in size fractions of tailings from the Prominent Hill iron oxide–copper–gold (IOCG) deposit, South Australia, with emphasis on rare earth element (REE) minerals and associated phases containing uranium (U). Assemblages of REE minerals can be highly complex at the micron scale and include sequences of mineral replacement, notably monazite → florencite, and monazite → synchysite. Bastnäsite-(Ce) commonly appears paragenetically early and is frequently altered or replaced by synchysite and parisite, supporting episodes of REE remobilization and reconcentration over geological time. Uranium is closely associated with REEs, and U-mineral assemblages are similarly characterized by intricate replacement relationships between uraninite and secondary phases. Uraninite is variably replaced by coffinite and the U-carbonate wyartite, reflecting changes in redox state, silica activity, and fluid composition. Additional replacement pathways from uraninite to Cu–Fe sulphides, including bornite and chalcopyrite, are documented and indicate coupled dissolution–reprecipitation of sulphides and U-minerals during superimposed hydrothermal activity. Preservation of mineralogical relationships within tailings drawn from multiple parts of a large deposit highlights their value as an essentially untapped library of information to reconstruct deposit evolution, complementing traditional study of selected drill core samples. Systematic investigation of tailings from large deposits can improve genetic models for large copper deposits, including but not restricted to IOCGs, and provide essential insights into REE behaviour, uranium remobilization, and critical metal potential. These findings emphasize the scientific and economic value of tailings-based studies for improved resource characterization, refining metallogenic interpretations, guiding future exploration strategies, and assessing opportunities for reprocessing and metal recovery in large ore systems worldwide across diverse geological settings. Full article

Early stage mineral exploration requires the reliable identification of anomalous gold zones from drillhole geochemistry in data-limited environments. This study applies a machine learning (ML) classification framework to detect anomalous gold zones (Au ≥ 0.68 ppm; 90th percentile) from bulk XRF multielement drillhole geochemistry in a Paleoproterozoic Birimian greenstone belt sulphide-hosted orogenic gold system, West African Craton. A total of 53,126 one-metre diamond core samples from 301 drillholes were preprocessed within a compositional data analysis (CoDA) framework, with Au being explicitly excluded from the centred log-ratio (CLR) transformation to eliminate target–predictor circularity. After Minimum Covariance Determinant (MCD) outlier filtering, 40,385 samples were retained to construct a 19-feature matrix of 10 CLR-transformed elements, 1 rock-type feature, and 8 sulphide–lithology interaction features. Drillhole-based block cross-validation (DH-block CV), validated by an experimental along-hole variogram (practical autocorrelation range ≈ 20 m), ensured spatially honest performance estimates. Four nonlinear classifiers—Random Forest (RF), XGBoost, LightGBM, and Multi-Layer Perceptron (MLP)—were benchmarked against a Logistic Regression (LR) linear baseline. All nonlinear classifiers achieved validation AUC of 0.936–0.938, outperforming LR (AUC = 0.931) with F1-score improvements of +0.09 to +0.11 and precision gains of up to +35 percentage points—directly reducing wasted drill holes in applied exploration. MLP recorded the highest F1-score (0.666) and precision (0.765), and XGBoost the highest recall (0.787). Permutation importance identified S-Ti (ΔAUC = 0.028), S-Fe (0.021), and S-Al (0.013) as the top-ranked features, confirming that sulphide enrichment relative to lithological background is the primary discriminating signal. Partial dependence analysis revealed a threshold-driven non-monotonic Fe dependence at CLR(Fe) ≈ 3, marking the transition from lithological dilutant to sulphide co-indicator—a nonlinear pattern inaccessible to linear classifiers. Full article

Arsenic represents a ubiquitous element in the environment, characterized by high mobility, complex chemical speciation and a strong sensitivity to redox conditions and biological activity, with microbial processes play a central role in its biogeochemical cycling. The present review provides a comprehensive and integrative synthesis of arsenic biogeochemical cycling across terrestrial, freshwater and marine environments, in which chemical speciation is explicitly treated as the central unifying concept controlling arsenic mobility, transformation and bioavailability, linking geological, chemical and biological processes across environmental compartments. Natural processes regulating arsenic distribution are examined from mineralogical sources and soil–water interactions to biologically mediated transformations in aquatic and marine biotic compartments, largely driven by microbial activity, highlighting the contrast between inorganic arsenic dominance in abiotic reservoirs and the prevalence of organoarsenicals in tissues of living organisms. The review further explores arsenic behaviour under natural environmental alterations and in extreme or unconventional ecosystems, where redox constraints, sulphide chemistry or intense fluid–sediment exchanges lead to deviations from the baseline speciation patterns. Against this framework, anthropogenic perturbations are discussed through several documented case studies, illustrating how industrial releases, the long-term effects of mining activities, agricultural practices and the use of synthetic arsenical compounds may change arsenic pathways primarily by altering geochemical and biological controls rather than through a generalized increase in total arsenic content. Overall, the topics covered provide an integrated framework for interpreting arsenic dynamics across environmental systems, emphasizing the complex biogeochemical processes governing arsenic cycling. Full article

This study investigates the effect of composite sulphur-containing collectors on the efficiency of floating hard-to-beneficiate sulphide polymetallic ores from the Tishinsky deposit (Kazakhstan). Specifically, this study examines a sulphur-containing collector comprising a sulphur-containing product and refined oil, as well as mixtures of these with sodium butyl dithiophosphate and sodium butyl xanthate in various mass ratios. This approach allows us to assess the role of oil-containing phases as carriers of hydrophobicity in colloidal–chemical interactions between flotation reagents and the mineral surface. The results of single-mineral flotation indicated that using a composite collector ([CO2SR]:[BX]:[BTP] = 1:1:1) provides higher flotation activity compared with conventional butyl xanthate. The most significant increase in recovery was observed for chalcopyrite and galena, indicating the selective nature of the reagent’s action. During the flotation of polymetallic ores, it was established that using the developed reagent system causes the lead content to increase by 4.35% (from 7.09% to 11.44%), whilst recovery rises by 5.67% (from 87.53% to 93.20%). For zinc, the increase in content reaches 5.13% (from 49.82% to 54.95%), whilst recovery increases by 12.9% (from 64.19% to 77.18%). Full article

The Djurkovo and Govedarnika deposits represent hydrothermal Pb-Zn systems spatially associated with the Eocene–Oligocene tectono-magmatic evolution of the Rhodope Metamorphic Complex. This study presents new mineralogical and geochemical data for galena, sphalerite, pyrite, and chalcopyrite obtained by electron probe microanalysis (EPMA) and LA-ICP-MS in order to evaluate the compositional variations of sulphides among the vein and metasomatic mineralization types and between the two deposits. The analysed sulphides exhibit distinct compositional signatures reflecting the different mineralization stages and hydrothermal environments. Sphalerite from the Govedarnika metasomatic ores is enriched in Mn (up to 5200 ppm), Fe (up to 5.13 wt.%) and Co due to interaction with Mn-rich skarn assemblages, whereas Djurkovo sphalerite shows elevated Cd (up to 3000 ppm), In and Hg concentrations. Trace-element systematics indicate coupled Fe-Mn incorporation, competitive Cd-Fe substitution and local re-equilibration processes associated with “chalcopyrite disease” textures. Late pyrite from the quartz-carbonate stage is enriched in As (up to 3.87 wt.%), Au (up to 78 ppm), Ag, Se, Sb and Tl, with positive Au-As and Au-Ag correlations suggesting invisible gold and possible submicroscopic precious-metal inclusions. The obtained data demonstrate prolonged hydrothermal evolution and highlight the potential role of the studied sulphides as concentrators of economically important elements. Full article

High-resolution aeromagnetic data are analysed using data transformation and enhancement techniques, including Reduction to the Pole (RTP), First Vertical Derivative (FVD), Tilt Derivative (TDR), and Total Horizontal Derivative (THDR) and Upward Continuation (UC), along with spectral, 2D and 3D modelling. This approach aims to characterise the subsurface architecture of the Shear Zone associated with breccia near Machanur in the Dharwar Craton, Southern India. Qualitative analysis indicates that an ENE-WSW-trending magnetic low, measuring 300 nT and 7 km by 0.7 km, is identified in this zone and exhibits magnetic remanence. It is associated with NW-SE-, NE-SW-, E-W-, NNE-SSW-, and ENE-WSW-trending magnetic lineations. The Spectral, 2D and 3D modelling reveals that the average depth extension of the breccia zone is ~400 m. Therefore, it is possible that a distinct magnetic marker zone is present, extending down to an average depth of 400 m in the breccia zone, and it is structurally controlled. In conjunction with previous geological, petrological, and borehole information, with present analysis, mineralisation is noted at a depth greater than 350 m, particularly in the form of sulphide veins associated with chalcopyrite, pyrite, covellite, chalcocite, cuprite, bornite, and influenced by hydrothermal activity. Full article

Porphyry copper deposits are one of the main sources of copper in the world and are usually associated with intrusive complexes of calc-alkaline composition formed in subduction-related geodynamic settings. Eastern Kazakhstan is characterized by the presence of a number of large porphyry copper-molybdenum deposits, but the metallogenic potential of many intrusive complexes in the region remains insufficiently studied. This paper presents new geological, mineralogical, and geochemical data on the Bala-Urpek deposit, located within the Sarykol intrusive complex (Eastern Kazakhstan), aimed at identifying diagnostic criteria for porphyry copper mineralization. The present study is based on field geological observations, petrographic analysis, and whole-rock geochemical data obtained by XRF and ICP-MS. Intrusive ore-bearing rocks are mainly represented by granitoids of the calc-alkaline series with I-type geochemical characteristics. Mineralogical studies have revealed veinlet-disseminated sulphide mineralisation, represented mainly by chalcopyrite and pyrite, as well as the development of hydrothermal alteration associations typical of porphyry systems. The geochemical characteristics of the rocks, including enrichment with large-ion lithophile elements and depletion with high-charge elements, indicate the subduction nature of magmatism. The combination of the data obtained allows us to identify geological, mineralogical and geochemical criteria characteristic of copper-porphyry systems and indicates the potential of the Bala-Urpek deposit area and the associated apophyses of the Sarykol complex for further exploration and prospecting. Full article

Agronomic biofortification offers an environmentally friendly way to improve crop nutrition. The biofortification of vegetables with iodine has attracted increasing attention due to its significance for human health. Hydrogen sulphide (H₂S) is a gaseous signalling molecule that affects many physiological and biochemical processes in plants. Lettuce (Lactuca sativa L.) plants were cultivated under controlled greenhouse conditions. Foliar applications of potassium iodate (KIO₃) and hydrogen sulphide (H₂S, supplied by sodium hydrosulphide (NaHS)) were applied separately and together (H₂S + KIO₃). Evaluations included growth parameters, photosynthetic pigments, biochemical metabolites, antioxidant enzyme activities, plant hormone levels, and mineral nutrient contents. All treatments resulted in significant changes in plant growth and physiological traits compared to the control. The combined application resulted in greater responses across several parameters; however, these observations do not demonstrate a causal or mechanistic interaction between the treatments. The combined application increased plant fresh weight by ~42% and leaf area by ~35% compared to the control. Total chlorophyll content approximately doubled (≈100% increase), while SOD, POD, and CAT activities increased by up to ~160%, ~13%, and ~40%, respectively. Proline and sucrose contents increased by approximately 100% and 85%. Hormonal changes included increases in indole-3-acetic acid (~44%) and cytokinins (~55%), and a decrease in abscisic acid (~20%). In addition, several macro- and micronutrients in leaves and roots were affected by the treatments. The combined application of KIO₃ and H₂S was associated with greater responses across several measured parameters than either compound alone; however, these observations do not demonstrate a causal or mechanistic interaction between the two compounds. Furthermore, as the experiment was conducted under non-stress greenhouse conditions, the observed physiological responses should be interpreted as changes in metabolic and regulatory processes rather than direct evidence of enhanced stress tolerance. Overall, the results indicate that foliar application of KIO₃ and H₂S can influence growth and physiological traits of lettuce under controlled conditions. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

Illyrian helmets represent a key element of Iron Age martial culture in the western Balkans, reflecting technological knowledge, workshop traditions, and long-distance cultural exchange. Based on the currently available archaeological record, Illyrian helmets are first attested in contexts dating to the 8th–7th centuries BC, with finds concentrated in Greece and the central and western Balkans, including Macedonia, Albania, Dalmatia, and the wider interior. Over time, the form developed into several variants (Types I–IIIB). This study presents the elemental characterization of the total set of 27 Illyrian helmets excavated in Albania and currently preserved in local museum collections, a region where the later types are particularly well attested. As the helmets are intact and exhibited in museums, portable in situ XRF analysis was employed. The main research questions addressed how the alloy composition, including minor and trace elements, reflects local metallurgical practices and distinguishes Illyrian helmets from similar helmets in neighboring regions. The results indicate the consistent use of bronze alloys dominated by copper (89–95%) with low- to medium-tin contents (3.5–9.9%), consistent with established alloying practices for durable protective equipment. Minor and trace elements, including iron (up to 1.5%), lead (up to 0.76%), arsenic (up to 0.09%), zinc (up to 1.17%), and antimony (up to 2.36%), likely reflect metallurgical choices, recycling practices, or impurities linked to regional copper deposits. Principal Component Analysis of four retained components, collectively accounting for 88.5% of the total variance, confirms a broadly standardized bronze tradition, with compositional outliers suggesting locally variable ore sources or recycling rather than systematic typological change. These elemental signatures, particularly the association of arsenic, antimony, zinc, and iron, suggest regional metallurgical characteristics consistent with Albanian sulphide ore deposits, while the overall compositional homogeneity supports the hypothesis of centralized production at workshops such as Epidamnus and Apollonia. Full article

In bioleaching processes, the use of microbial consortia establishes a favourable environment that supports the growth and activity of multiple microorganisms, thereby enhancing their synergistic interactions during leaching. Mineral dissolution efficiency is consistently higher in consortia than in monocultures. Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans exhibit metabolic complementarity and synchrony, including interactions with thermophilic microorganisms. Bioleaching is typically conducted under highly acidic conditions (pH 1–2), where microorganisms utilize essential resources such as nutrients and oxygen, while tolerating elevated concentrations of heavy metals. This review aims to examine the characteristics and current applications of microbial consortia, with particular emphasis on their interactions with heavy metals, the behaviour of their exopolysaccharides (EPS) under toxic conditions, their role in bioremediation across diverse environmental systems, and their potential for industrial implementation. Microbial consortia represent a high-value biotechnological tool in both mining and environmental remediation. Their synergistic interactions enable enhanced efficiency in the bioleaching of sulphide minerals, promoting the mobilization of both economically valuable and contaminant metals, and significantly outperforming individual cultures. Consequently, microbial consortia constitute a versatile, resilient, and eco-efficient platform for metal recovery and the mitigation of environmental liabilities. This review focuses on the applications of bacterial consortia in bioleaching processes and highlights their potential for emerging and future use. Full article