Search Results (696)

The Xiaoyinuogaigou (XYN) gold deposit is located in the central Erguna Metallogenic Belt, northeastern China, and represents a characteristic example of Mesozoic gold mineralization in the Mongol–Okhotsk orogenic province. Despite its economic significance, the timing of mineralization and the nature of the ore-forming fluid system have not been well constrained. To address these questions, a systematic investigation of fluid inclusions, isotopes, geochemistry, and geochronology was conducted. The study reveals that: (i) four types of fluid inclusions are identified in auriferous quartz veins, with co-existing aqueous liquid-vapor and NaCl daughter-mineral three-phase inclusions, indicating the involvement of at least two chemically distinct fluids; (ii) the ore-forming fluids are characterized by moderate temperatures (163.2–357.6 °C), low to moderate salinities (3.06–11.34 wt% NaCleqv.), and H–O isotope compositions (δD = −133.3 to −112.3‰; δ¹⁸O fluid (SMOW) = +1.74 to +4.06‰) consistent with a hydrothermal system incorporating a substantial non-magmatic water component; and (iii) REE geochemistry and sulfur isotopes (δ³⁴S = +4.47 to +11.75‰, mean +8.29‰, n = 4) indicate that ore-forming materials were derived at least in part from the ore-hosting granite porphyry. Zircon U–Pb geochronology constrains the granite porphyry crystallization to 180 ± 3 Ma, and hydrothermal monazite U–Pb dating yields an age of 162.3 ± 3.6 Ma (MSWD = 0.95), for a Middle Jurassic hydrothermal event. We therefore conclude that XYN is an epizonal orogenic gold deposit formed during the late compressional to post-collisional transition of the Mongol–Okhotsk orogeny. Full article

The object of this study is nephrite found on Mount Bikilyar, South Urals, Russia. The purpose of the study is to determine the mineral and chemical composition of the nephrite and host rocks and to develop a model of the nephrite’s formation. The mineral composition was studied using a scanning electron microscope with an energy-dispersive quantitative microanalysis system. We studied the chemical, trace element, and oxygen isotopic composition. The nephrite’s composition is dominated by tangled fibrous and downy aggregates, with large lamellar grains of actinolite. Magnesian hornblende and resorbed diopside grains, as well as chromite, titanite, apatite, chlorite, sulfides, and secondary minerals, are less common. The host rocks are metagabbro of diverse mineral compositions. The nephrite is characterized by a subchondritic trough-like distribution spectrum of REE with a negative Eu anomaly. The chondrite-normalized spectrum of the metagabbro is characterized by significantly higher REE content values. The δ¹⁸O isotopic composition of the nephrite is +5.53 to +5.80‰, indicating the deep origins of oxygen inherited from ultramafic rocks. The extremely heterogeneous and heavier composition of the metagabbro is +4.42 to +11.27‰, reflecting different contributions of the mantle and crustal sources to its formation. The nephrite was formed as a result of ultramafic xenoblock transformation under the influence of gabbro. Initially, serpentine was replaced by diopside, after which actinolite developed to form the nephrite. The Bikilyar nephrite differs in its mineral composition from the nephrite of other deposits. Despite the unique mineral composition, Bikilyar nephrite is a typical serpentinite in terms of paragenesis and chemical composition. The nephrite-specific mineral and chemical composition is explained by the small size of the ultramafic block that is in a significant volume of gabbro. Full article

Pyrite occurs in a wide range of ore-forming environments, and its trace element and rare earth element (REE) compositions are important geochemical indicators for determining its genetic origin, thereby providing valuable constraints for ore deposit research and mineral exploration. Machine learning, as a data-driven technique, offers new insights into the genesis types of pyrite by comprehensively analyzing data and uncovering underlying patterns. In this study, representative pyrite samples with diverse morphologies, including both sedimentary and hydrothermal types, were collected. Based on electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), a comprehensive analysis of pyrite genesis was conducted. Furthermore, an artificial neural network (ANN) machine learning algorithm was employed to establish a classification model, and the predictive performance of this trained model was compared against that of traditional discrimination methods. The results show that when only trace elements were used as input features, the training set yielded a classification accuracy of 64.3% for sedimentary pyrite and 93.9% for hydrothermal pyrite. In the testing set, sedimentary pyrite was classified with an accuracy of 100%; however, this result may reflect the limited sample size rather than the model’s true generalization ability and therefore should be interpreted with caution. Feature importance analysis identified Cu, Zn, Te, Bi, and Pb as the key variables of this model. When both trace and rare earth elements (REEs) were used, the detection accuracy for sedimentary pyrite and hydrothermal pyrite in the training set was 87.5% and 100%. However, the combined trace + rare earth elements model exhibited a clear overfitting tendency: its overall training accuracy reached 95.2%, but its validation accuracy (88.9%) was lower than that of the trace-only model (93.8%). Feature importance analysis indicated that Pb, Ho, Zn, Ag, and Ce contribute substantially to the model. The machine learning model proposed in this study is convenient and efficient, providing a novel basis for determining the genetic types of complex pyrite. Full article

The Kalasayi tungsten deposit is a medium-sized quartz-vein scheelite tungsten deposit in the Western Tianshan, Central Asia Orogenic Belt. The Kalatawu pluton yielded Late Carboniferous zircon U–Pb ages (313.99–310.32 Ma), and molybdenite Re–Os dating gives an isochron age of 302.3 ± 1.8 Ma for W mineralization, indicating an ~8–12 Myr magmatic-hydrothermal system. Whole-rock geochemistry classifies the pluton as aluminous A₂-type granite formed in a post-collisional extensional setting. Zircon Hf isotopes (εHf(t) = +2.8 to +8.3) suggest a mixed juvenile lower crust source with mantle input. In situ LA-ICP-MS scheelite trace element analysis and REE geochemistry distinguish two populations: proximal Group I (high Mo, low Sr, low ΣREE, right-inclined REE patterns) is precipitated from oxidizing magmatic fluid, and distal Group II (low Mo, high Sr, high ΣREE, flat REE patterns, strong positive Eu anomalies) records reduced, mixed fluid with intense fluid–rock interaction. Fluid inclusion data show decreasing temperature and salinity proximally to distally, confirming that mixing of magmatic and meteoric water led to cooling and pH increase that caused W precipitation. A four-stage metallogenic model is proposed for a post-collisional extensional setting, providing robust evidence for A-type granite-related, multi-stage W mineralization and establishing exploration indicators for the southwestern Central Asia Orogenic Belt. Full article

The Niukutoudong deposit, in the Qimantage metallogenic belt, western East Kunlun Orogenic Belt, is a recently discovered cobalt-rich polymetallic deposit. This study integrates zircon U-Pb geochronology and whole-rock geochemistry of the ore-hosting intrusions to constrain their emplacement ages, petrogenesis, and tectonic setting, thereby constraining the Early Devonian tectonic evolution of the East Kunlun area. The geochronological results for four samples demonstrate that the granite porphyry, granite, granodiorite, and gabbroic diorite at Niukutoudong were emplaced in the Early Devonian (403.7–406.3 Ma). Geochemically, the granite, granodiorite, and gabbroic diorite are high-K calc-alkaline, metaluminous to weakly peraluminous I-type granitoids, characterized by consistent enrichment in LREEs, negative Eu anomalies, enrichment in LILEs, and depletion in HFSEs. The granite porphyry, by contrast, is a peraluminous A-type granite distinguished by elevated total REE contents, pronounced negative Eu anomalies, and high HFSE abundances. The regional source characteristics of coeval intrusions, integrated with key incompatible element ratios (e.g., Nb/Ta, Ba/Nb), imply that the Early Devonian Niukutoudong intrusions were probably generated through crust–mantle interaction. Integrated evidence indicates that the Niukutoudong intrusive rocks formed in a post-collisional extensional environment following the closure of the Proto-Tethys Ocean. The mixed crust–mantle signature common to both regional and local Early Devonian intrusive rocks indicates that the East Kunlun Orogenic Belt had already transitioned from syn-collisional crustal thickening into a post-collisional extensional stage by the Early Devonian, marked by lithospheric thinning, asthenospheric upwelling, and crust–mantle interaction. This magmatism records the tectonic regime shift and likely has a genetic link with the Niukutoudong Co-polymetallic mineralization, offering critical insights into the Qimantage metallogenic framework. Full article

Terrestrial carbonates provide important archives for reconstructing paleoenvironmental, paleoclimatic and hydrogeological conditions in semi-arid to arid continental basins. This study investigates the origin, mineralogical characteristics and geochemical properties of calcrete and dolocrete occurrences developed along the Konya Fault Zone within the Konya Closed Basin (Central Türkiye). Field observations, petrography, XRD, SEM–EDS, major and trace element geochemistry, REE analyses, stable isotopes (δ¹³C–δ¹⁸O), geostatistical methods and ESR dating were employed. The results reveal two distinct terrestrial carbonate systems. Dolocretes occur within Quaternary alluvial fan deposits developed on ultramafic–ophiolitic rocks, whereas calcretes developed pedogenically within Quaternary alluvial fan deposits overlying carbonate bedrock. Calcite, dolomite, quartz, palygorskite and smectitic clay minerals constitute the principal mineral phases. Rhizoliths, tubular structures, nodules, microbial filaments and laminated carbonate horizons indicate pedogenic carbonate accumulation. The association of palygorskite with dolomite and smectitic clay minerals suggests alkaline, Mg-rich pore waters under semi-arid conditions. Elevated Sr concentrations indicate prolonged groundwater–carbonate interaction, whereas high Ni and Co contents in the dolocretes reflect the influence of ultramafic source rocks. REE distributions are characterized by LREE enrichment, weak Eu anomalies and locally developed negative Ce anomalies, indicating pedogenic fractionation under oxidizing meteoric conditions. Stable isotope data indicate precipitation from meteoric waters influenced by soil-derived CO₂ under semi-arid climatic conditions dominated by C3 vegetation. ESR ages ranging from approximately 390–217 ka indicate carbonate formation during the Middle Pleistocene (MIS 11–MIS 7). Integrated mineralogical, geochemical, isotopic and chronological evidence indicates that the Konya terrestrial carbonates formed predominantly through pedogenic processes within meteoric vadose-zone conditions controlled by bedrock lithology (carbonate and ultramafic rocks), groundwater circulation and Quaternary climatic variability. These deposits represent important archives of Middle Pleistocene paleoenvironmental and paleohydrological evolution in Central Anatolia. Full article

This article describes the mineralogical and geochemical features of the Marsyaty Mn–Fe sedimentary deposit in the Northern Urals (Russia). Oolitic ironstones of the deposit are localized in the Cenomanian coastal sandstones. Manganese ores (carbonate and carbonate–oxide types) lies within the Lower Paleocene siliciclastic sediments and are separated from the oolitic ironstone (iron oxide and iron carbonate types) by a polymictic gravelite bed. Authigenic Fe³⁺ oxyhydroxides (goethite and ferrihydrite), chamosite/berthierine and late siderite predominate in the ironstones; kaolinite, apatite, perhamite, calcite and dolomite are minor constituents. Rhodochrosite and rancieite are the major minerals of the manganese ore; Mn-dominated phyllosilicates (parsettensite? and caryopilite?) are rare. Both ore types contain authigenic glauconite, montmorillonite, sulfides (sphalerite/wurtzite, galena, and pyrite), gibbsite/boehmite and REE phosphates. Both ore types contain detrital quartz, ilmenite, zircon, monazite, epidote, titanite, muscovite and feldspars. The δ¹³C_carb value (VPDB) varies from −18.5 to −23.3 in both ironstone types and from −10.0 to −41.0 ‰ in the manganese ore. The negative C isotopic composition and numerous organic remains indicate the involvement of microbial processes in the formation of both types of carbonate ores. The Fe and Mn ores belong to one transgression–regression sedimentation cycle and formed consecutively during the evolution of the West Siberian basin. A unique feature of the Marsyaty deposit includes two ore formation stages within a limited area and over a relatively short geological period: the accumulation of (i) oolitic ironstones enriched in Mn first and then (ii) manganese ores only. Full article

In the Afşin–Elbistan coal seam in Türkiye, this study investigates the vertical distribution, enrichment features, and mineralogical controls of trace elements and rare earth elements (REEs). Thirty coal samples were collected vertically from the Kışlaköy open-pit mine. Major oxide concentrations were determined by XRF for 29 samples, whereas trace element concentrations were determined by ICP–MS for all 30 samples. Mineralogical and textural characteristics were investigated in 15 selected samples by XRD and SEM–EDS. The coal is abundant in quartz, pyrite, and gypsum, along with trace amounts of calcite, clay minerals, and feldspars, which demonstrate the combined effects of detrital input, reducing depositional conditions, and post-depositional alteration. The major oxide composition is dominated by SiO₂, CaO, Al₂O₃, and Fe₂O₃, showing notable contributions from carbonate, aluminosilicate, and Fe-bearing mineral phases. Most trace elements occur at levels close to the world coal average, whereas V, Ni, and U are significantly enriched, and Cr and Co are slightly enriched. Total REE contents range from 21 to 125 ppm, averaging 51 ppm, and display light REE enrichment over heavy REEs. Weak negative Ce anomalies and slight positive Eu anomalies indicate variable redox conditions and the influence of terrigenous mineral input. Vertical distribution patterns indicate that during peat accumulation and early diagenesis, variations in detrital input, mineral matter abundance, and depositional redox conditions regulated trace element and REE distributions. REEs are mainly associated with aluminosilicate and locally phosphate-bearing phases, whereas V, Ni, and U are linked to organic matter and/or sulfide-rich intervals. These results show that the main factors influencing trace-element and REE behaviour in the Afşin–Elbistan coal seam are the mineralogical composition and redox evolution. Full article

To establish the relationship between the composition of wine and its regional origin, the most stable chemical parameters are selected because their variation is easiest to trace. Together with “classical” micro- and macroelements, rare earth elements (REEs) can be used for such purposes. However, the relationship between REE content in wine and its regional origin has not been systematically studied. This study examines the migration of REEs in the “soil-grape-wine” system to identify the relationship along the entire chain and establish the geographical origin of grapes and wine. The research was carried out on grapes and wines from the Chardonnay and Cabernet Sauvignon varieties, as well as soil samples selected from different vineyards. The concentrations of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in the studied samples were determined using ICP-MS. It was established that the studied soil samples are characterized by relatively low REE concentrations. Low transfer of REEs from soil to grapes was observed because the soils are rich in clay minerals that firmly retain these elements. Statistically significant differences in the REE content of grapes from different regions were detected (p < 0.05). Multidimensional analysis methods allowed us to group grape samples into clusters based on varietal and regional origin. Discriminant analysis showed the possibility of using the concentration of REEs as markers of the geographical origin of grapes. Of all the REEs, only La and Ce are reliably established in all wines. When determining the geographical origin of wine, the use of REE content is limited due to their very low concentrations in wine. In this regard, it has been proposed to use them in combination with macro- and microelements, which improves the classification performance of the model. Full article

Rare earth elements (REEs) flotation from carbonatitic ores remains challenging due to the complex association between REE-bearing minerals and carbonate-rich gangue phases. Although previous studies have reported REE beneficiation from the Fen Deposit, the influence of depressant type, sodium silicate dosage, EDTA addition, and collector selection on flotation selectivity remains poorly understood. Therefore, this study presents a preliminary assessment of different reagent schemes for the flotation of REE-bearing minerals from the Fen Deposit. Chemical and mineralogical characterization confirmed the predominance of light REEs, mainly Ce and La, associated with monazite and fluorocarbonate minerals of the bastnäsite–parisite–synchysite group. Flotation screening tests revealed limited gangue rejection, particularly for Ca- and Ba-bearing minerals, indicating that mineralogical complexity strongly influences flotation selectivity. Among the depressants evaluated, sodium silicate and citric acid exhibited the most promising performance, while EDTA enhanced the total rare earth oxides (TREO) grade at higher sodium silicate dosages. Collector tests resulted in moderate REE enrichment in the overflow products, with NaOL yielding the highest recovery (~62%). However, TREO grades remained relatively low (~2.3–2.7%), suggesting that reagent selection alone is insufficient to overcome the flotation limitations imposed by the ore from the Fen Deposit. The results provide an exploratory evaluation of reagent schemes for Fen carbonatite ore and identify key challenges and opportunities for future process optimization. Full article

Multispectral satellite imagery is a very useful technique to identify altered wall rocks around orogenic gold systems. In this study in the Akzhal–Vasilyevskoye district, Kazakhstan, we show that a geology-based ASTER band-ratio workflow is a useful technique to trace metasomatic footprints of mineralization. In the West Kalba camp, beresite and listvenite both produce usable ASTER SWIR signals, while pyrite and arsenopyrite are largely featureless at multispectral resolution. Five ratios on AST_07XT surface-reflectance data, screened with upper-tail anomaly masks, have enabled identification of sericitic cores, chloritic and carbonate halos, ferric caps, and zones containing mixtures of ferrous phyllosilicates. We show that district-scale Al–OH sericitic anomalies occur within Mg–OH and carbonate shells. At Vasilyevskoye the pattern is due to beresite nuclei within listvenite rims, while at Tokum the sericitic centres remain compact within wider Mg–OH and carbonate halos. Mean polygon spectra differ between the two footprints across Bands B4–B6 and across the SWIR tail (B7–B9). SEM–EDS at Vasilyevskoye links the mapped anomalies to chlorite, sericite, and carbonate gangue assemblages with sulfide-bearing volumes. The data also allow identification of subordinate REE, phosphate, and Ti enrichment within carbonaceous and polymineralic host lithologies. Full article

Titanite is a widespread accessory mineral in magmatic, metamorphic, and hydrothermal systems and can incorporate trace elements that are sensitive to ore-forming processes. Although titanite trace-element chemistry has been widely applied to individual ore systems and deposit comparisons, its potential for supervised machine-learning-based discrimination across multiple ore deposit types remains less systematically explored. In this study, we compiled a literature-based LA-ICP-MS titanite trace-element dataset comprising 1679 analyses from five major ore deposit types: porphyry, skarn, iron oxide–apatite (IOA), iron oxide copper–gold (IOCG), and orogenic Au deposits. A common feature set of 21 trace elements, including REE, Y, Zr, Hf, Nb, Ta, Th, and U, was used to evaluate six supervised machine-learning algorithms: K-nearest neighbors, support vector machine, random forest, XGBoost, TabMap, and TabPFN. Two-dimensional element and element-ratio diagrams showed substantial overlap among deposit types, whereas machine-learning models better captured deposit-type-related multielement patterns in the compiled dataset. TabPFN achieved the highest stratified 5-fold cross-validation performance, with an accuracy of 0.957 ± 0.011 and a macro-F1 score of 0.944 ± 0.012, followed by TabMap and XGBoost. SHAP and TabMap-SHAP interpretations suggest that deposit classification is mainly associated with coupled variations in REE-Y, Eu, HFSE, and Th-U systematics rather than with a single diagnostic element. These results indicate that titanite trace-element compositions may provide a useful quantitative and interpretable approach for deposit-type discrimination within compiled geochemical datasets, while broader application requires expanded standardized datasets and independent validation samples. Full article

In this study, we examined the mineralogy, geochemistry and origin of Fe–Mn mineralization occurring as lenses within siliceous mudstones of the Middle Eocene Maden Complex (Durmuştepe, Elazığ, Türkiye) using multivariate statistical methods and Compositional Data Analysis (CoDA). Major-oxide, trace-element and REE analyses were performed on 21 samples (n = 21), comprising 11 ore and 10 host-rock samples. Ore microscopy, discrimination diagrams, PAAS-normalized REE patterns, Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), factor analysis, Kendall correlation and CLR-transformed CoDA-PCA were applied. The ore consists of pyrolusite, braunite, manganite, magnetite and hematite. Massive and felty textures indicate rapid precipitation linked to abrupt physicochemical changes near the vents. Fe/Mn ≈ 1.62 and Co/Ni = 0.03–0.04 support an exhalative origin; Ce/Ce* = 0.10–0.15 (mean 0.11) records a pronounced negative Ce anomaly; and Eu/Eu* = 1.06–1.18 suggests vent-fluid temperatures below ~250 °C. CoDA-PCA shows that Ce is decoupled from the other lanthanides; HCA separates ore from host-rock populations; and factor analysis indicates that Ti–Al–K detrital input diluted ore accumulation. Integrating these results, we interpret Durmuştepe as a proximal volcano-sedimentary hydrothermal-exhalative Fe–Mn system that formed during magmatism in the Maden marginal basin under oxic seawater mixing and contemporaneous detrital sedimentation. The multivariate workflow also provides a reproducible approach for source characterization in similar mixed-origin deposits. Full article

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

Sedimentary manganese deposits are an important mineral resource and also play a significant role in restoring the ancient marine environment. The redox environment of the ocean during the Mesoproterozoic era has long been a subject of controversy. This paper takes a large-scale sedimentary manganese deposit in northwest China as the research object, attempting to analyze the changes in the marine environment during the Mesoproterozoic era and their impact on the Mn mineralization processes. In recent years, an exploration breakthrough has been made in the manganese deposits in the Annanba region on the southern margin of the Dunhuang block, NW China. The Qingshagou Mn deposit is the largest and most representative in the region. Geochemical characteristics show that the ores have low average ratios of Fe/Mn (<0.19), V/Cr (<1.20), V/(V + Ni) (<0.54), and Al/(Al + Fe + Mn) (<0.30) but high average ratios of U/Th (~0.95), and Y/Ho (~28). The Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) patterns exhibit that middle rare earth elements are slightly enriched with weak positive anomalies for both Y (0.93~1.01) and Ce (0.97~1.15) and weak negative anomalies for Eu (0.87~0.99). The δ¹³C_PDB value of the ore ranges from −13.4‰ to −23.3‰, which is consistent with the δ¹³C_PDB value range of organic matter. Synthesizing these findings, it is concluded that the Qingshagou Mn deposit formed in a suboxic to oxic environment, the ore-forming materials were primarily derived from a submarine hydrothermal system, and the changes in redox conditions promoted the Mn precipitation. Full article