Search Results (429)

The southeastern Iberian Peninsula, particularly the Águilas Arc within the Neogene Volcanic Province (NVP), represents a promising geothermal domain with complex tectonics and geology. The Palomares Fault Zone (PFZ), a key shear structure initiated during the Late Miocene, acts as a conduit for fluid migration, promoting mineralization and potential anomalies of rare and critical metals through fluid–rock interaction. This study investigates such interactions in the southernmost Águilas Arc, focusing on the El Arteal fault segment within the eastern PFZ strand. Mineralogical, geochemical, and hydrogeological analyses were performed using XRD, SEM, and ICP-MS techniques. Results reveal six mineral assemblages (MA) within the fault segment where the fault gouge samples were characterized by cataclastic textures and the occurrence of authigenic minerals, including halite, kaolinite, illite, paragonite, goethite, hematite, gypsum, barite, celestine, and quartz. Geochemical data indicate enrichment signatures in large-ion lithophile elements (LILE) and minor chalcophile and light rare-earth elements (LREE). Two thermal hydrofacies with alkaline metals enrichment were identified in wells and mine shafts: (1) Na⁺SO₄²⁻ and (2) Na⁺Cl⁻, where the latter exhibits high Na⁺ and Cl⁻ concentrations toward deeper sectors. These findings suggest multiple stages of fluid–rock interaction controlled by temperature: an early phase dominated by epithermal mineralization, followed by late-stage circulation of hypersaline fluids. This evolution provides an abnormal geochemical signature that is unique in the Aguilas Arc Geothermal System. Full article

The Felbertal tungsten mineralisation in the Tauern Window (Eastern Alps) is hosted by the Early Paleozoic Habach Complex belonging to the Lower Schieferhülle. In predominantly mafic meta-volcanic rocks, mostly amphibolites, green amphibole crystallised in assemblages with plagioclase, epidote, chlorite, sphene and quartz. Microstructural features and preferential orientation of the amphiboles define planar-linear structures of finite strain and indicate that their crystallisation is coeval to the main deformation event. Amphibole crystals display core-to-rim zonations with increasing ^IVAl, ^VIAl, Na and Ti and decreasing Si, covering actinolite over magnesio-hornblende to tschermakite compositions. Amphibole zonations and assemblages are similar to metabasites in the classical Barrovian mineral zones in the Dalradian of Scotland and typical of a prograde metamorphism from the greenschist over epidote-amphibolite to the lower amphibolite facies. Amphibole endmember geothermobarometry defines an early P-T path segment from 400 °C/2 kbar to 540 °C/6 kbar, and a consecutive later P-T path segment from ~500–540 °C/6 kbar to maximal P-T conditions of ~620–640 °C/7–8 kbar. As Carboniferous granitoid intrusions within the Habach Complex underwent penetrative ductile deformation, an Alpine Tertiary age of the lower amphibolite facies metamorphism, as observed in other parts of the Lower Schieferhülle, appears suitable. Full article

Despite complex geological conditions and limited exploration activity, the South Yellow Sea Basin has not yet yielded a commercial hydrocarbon discovery. Recent studies indicate substantial hydrocarbon potential within the Upper Sinian–Lower Silurian strata; however, the mechanisms controlling hydrocarbon accumulation in these sequences remain poorly understood. In this study, outcrop, drilling, organic geochemical, and seismic data from the Yangtze Plate are integrated using a land–sea comparison approach to evaluate petroleum geological conditions, identify key controlling factors, and predict hydrocarbon accumulation in the Upper Sinian–Lower Silurian sequences of the Laoshan Uplift. The results indicate that the Upper Sinian–Lower Silurian strata possess favorable petroleum geological conditions, including two effective source–reservoir–seal assemblages. Key controls on deep hydrocarbon accumulation include high-quality Lower Cambrian source rocks, early development of the Laoshan paleo-uplift, structural stable zones, and Lower Silurian detachment layers. Three hydrocarbon accumulation evolution models are proposed: (1) early stage lateral hydrocarbon supply from adjacent depressions, (2) early stage lower-source–upper-reservoir charging, and (3) late-stage deep-burial cracking with structural adjustment. These findings provide important guidance for deep hydrocarbon exploration the Upper Sinian–Lower Silurian sequences of the Laoshan Uplift in the South Yellow Sea Basin. Full article

The Hadamengou gold deposit, hosted in the Precambrian metamorphic basement, is a super-large gold deposit occurring along the northern margin of the North China Craton. Despite extensive investigation, the genesis of the gold mineralization is poorly understood and remains highly debated. This study integrates a comprehensive dataset, including fluid inclusion microthermometry and C-H-O-S-Pb isotopes, to better constrain the genesis and ore-forming mechanism of the deposit. Hydrothermal mineralization can be divided into pyrite–potassium feldspar–quartz (Stage I), quartz–gold–pyrite–molybdenite (Stage II), quartz–gold–polymetallic sulfide (Stage III), and quartz–carbonate stages (Stage IV). Four types of primary fluid inclusions are identified, including pure CO₂-type, composite CO₂-H₂O-type, aqueous-type, and solid-daughter mineral-bearing-type inclusions. Microthermometric and compositional data reveal that the fluids were mesothermal to hypothermal, H₂O-dominated, and CO₂-rich fluids containing significant N₂ and low-to-moderate salinity, indicative of a magmatic–hydrothermal origin. Fluid inclusion assemblages further imply that the ore-forming fluids underwent fluid immiscibility, causing CO₂ effusion and significant changes in physicochemical conditions that destabilized gold bisulfide complexes. The hydrogen–oxygen isotopic compositions, moreover, support a dominant magmatic water source, with increasing meteoric water input during later stages. The carbon–oxygen isotopes are also consistent with a magmatic carbon source. Sulfur and lead isotopes collectively imply that ore-forming materials were derived from a hybrid crust–mantle magmatic reservoir, with minor contribution from the country rocks. By synthesizing temporal–spatial relationships between magmatic activity and ore formation, and the regional tectonic evolution, we suggest that the Hadamengou is an intrusion-related magmatic–hydrothermal lode gold deposit. It is genetically associated with multi-stage magmatism induced by crust–mantle interaction, which developed within the extensional tectonic regimes. Full article

The peculiar high-pressure mineral assemblage omphacite, epidote, quartz, calcite, titanite, and opaque minerals, ±phengite, has been observed in the Riffelberg–Garten Unit (RGU), a heterogeneous metasedimentary rock assemblage of the Zermatt–Saas Zone. Microstructural analysis, mineral chemistry, and petrologic modelling allowed to refine the syn-D2 P-T peak conditions for the Alpine tectono-metamorphic evolution. In the upper Valtournenche, S2 foliation is the dominant fabric at the regional scale of the Zermatt–Saas Zone. Petrologic modelling of the syn-D2 mineral assemblage indicates climax conditions of P = 1.85–2.0 GPa and T = 500–525 °C. These estimates are in good agreement with those inferred in the RGU metasedimentary matrix and enclosed eclogite and metagabbro elements. During exhumation, RGU rocks re-equilibrated texturally and mineralogically under blueschist–/epidote–amphibolite (P = 0.4–1.3 GPa and T = 350–500 °C during D3) and greenschist (P ≤ 0.25 GPa and T ≤ 400 °C during) facies conditions. This study highlights the potential of petrologic modelling for constraining the environmental conditions of metamorphism even in anomalous mineral assemblages where conventional thermobarometry is not applicable. Full article

The northern part of the Naomugeng Sag in the Erlian Basin shows favorable sandstone-type uranium mineralization in the lower member of the Saihan Formation. The sandstone thickness ranges from 39.67 to 140.36 m, with an average sand content ratio of 76.33%, indicating broad prospecting potential. This study focuses on samples from uranium ore holes and uranium-mineralized holes in the area, conducting grain-size analysis of uranium-bearing sandstones, heavy mineral assemblage analysis, and detrital zircon U-Pb dating to systematically investigate provenance characteristics. The results indicate that the uranium-bearing sandstones in the lower member of the Saihan Formation were primarily transported by rolling and suspension, characteristic of braided river channel deposits. The heavy mineral assemblage is dominated by zircon + limonite + garnet + ilmenite, suggesting that the sedimentary provenance is mainly composed of intermediate-acid magmatic rocks with minor metamorphic components. Detrital zircon U-Pb ages are mainly concentrated in the ranges of 294–217 Ma (Early Permian to Late Triassic), 146–112 Ma (Middle Jurassic to Early Cretaceous), 434–304 Ma (Late Carboniferous to Early Permian), and 495–445 Ma (Middle–Late Ordovician to Early Silurian). Combined with comparisons of the ages of surrounding rock masses, the provenance of the uranium-bearing sandstones is mainly derived from intermediate-acid granites of the Early Permian–Late Triassic and Middle Jurassic–Early Cretaceous periods in the southern part of the Sonid Uplift, with minor contributions from metamorphic and volcanic rock fragments. The average zircon uranium content is 520.53 ppm, with a Th/U ratio of 0.73, indicating that the provenance not only supplied detrital materials but also provided uranium-rich rock bodies that contributed essential metallogenic materials for uranium mineralization. This study offers critical insights for regional prospecting and exploration deployment. Full article

Quaternary lavas (ankaramite, basalt, basaltic andesite, andesite, dacite) from the Kamchatka, Kurile, Ecuador and Cascade volcanic arcs contain Cl-bearing mineral microinclusions in rock-forming minerals and groundmass volcanic glass. They are represented by chlorargyrite (with a variable amount of native Ag), Cu, Ag, Sn, and Zn compounds with Cl and S, Sn- and Pb-Sb oxychlorides compositionally similar to abhurite and nadorite, as well as bismoclite and Cl-F-apatite. The Cl-bearing compounds with chalcophile metals are best approximated by mixtures of chlorargyrite with Cu sulfides, malachite, or azurite. Some Cl-bearing solid microinclusions in magmatic rock-forming minerals could have formed from Cl-rich melts exsolved from arc magmas during differentiation. Alternatively, specific magmatic microinclusions may record the decomposition of primary sulfides in the presence of Cl-bearing magmatic volatiles. Post-magmatic Cl microminerals found in fractures, pores, grain contacts, and groundmass glass are most probably precipitated from hydrothermal fluids accompanying their emplacement at the surface and post-eruption transformations in active fumarole fields. Assemblages of Cl-bearing microminerals with native metal, alloy, sulfide, oxide, and sulfate microinclusions in arc lavas potentially record late-magmatic to post-magmatic stages of formation of the epithermal and possibly porphyry mineralization beneath arc volcanoes. Full article

The first comprehensive study about of amber from the Lower Cretaceous of the Lusitanian Basin, in the Estremadura region of western Portugal, is here reported. The amber was recovered as isolated clasts in the Portela da Vila outcrop section, near the small villages of Ramalhal and Ameal, from sedimentary deposits belonging to the Lugar d’Além Formation considered to be of Hauterivian age. The chemical composition of amber clasts was examined in order to infer their botanical source via biomarker analysis. GC–MS and GC×GC–TOFMS showed a strong predominance of abietane-type diterpenoids, including compounds such as amberene, ferruginol (phenolic abietane), kaurane and the derivative of clerodane. The dominance of abietane diterpenoids along with these specific biomarkers is consistent with resin exudation by Araucariaceae/Cheirolepidiaceae conifers, as supported by previous chemotaxonomic studies of Cretaceous amber. Palynological studies of the same sedimentary rock samples highlighted a pollen–spore assemblage characterized by low diversity and number of specimens, and dominated by conifer pollen assigned to the genera Classopollis, Araucariacites and coniferous bisaccate pollen, with relative occurrences of fern spores. The combined geochemical and palynological studies strongly support a source related to conifer plants for the amber here reported. Full article

Ensuring the stability of underground structure engineering in deep coal mines is the key to the successful exploitation of deep geothermal resources in coal mines. Therefore, this paper carried out mechanical tests on rock–coal combinations under different rock properties and studied their stress–strain laws, energy and acoustic emission evolution laws, as well as deformation and failure laws. The main conclusions are as follows: (1) The strength of rock–coal assemblages mainly depends on the strength of coal samples far from the interface, and coal samples are the main bearing bodies in the process of uniaxial compression. (2) Because oil shale has a relatively low strength and large deformations, the rock property of relatively large deformations can improve the ability of the combinations to convert external energy into elastic energy. (3) The acoustic emission energy rate signals of rock–coal combinations can be divided into three stages: quiet, active, and sudden increase. The acoustic emission energy rate signals of limestone–coal and sandstone–coal assemblages are of the “lone-shock” type, while the acoustic emission energy rate signals of oil shale coal assemblages are of the “Multi-peak” type. (4) When oil shale with a relatively low strength and large deformations occurs, both the rock sample and coal sample of the combination appear to have deformation localization zones, and the deformation localization zones in the rock sample and coal sample run through the rock–coal interface, which eventually leads to the failure of both the rock sample and coal sample of the combination. These relevant research results help ensure the safe utilization of geothermal resources in deep coal mines and promote the global energy structure in accelerating the transformation to low-carbon and clean energy. Full article

Quantitative mineralogy plays a vital role in exploration geology by defining mineral assemblages, identifying metal-bearing phases, and providing clues to optimize ore processing. In peraluminous rare-metal granites such as those at Beauvoir (France), mineral quantification is challenging, especially in altered facies where partial replacement complicates the estimation of muscovite and feldspars. The present study applies micro-X-ray fluorescence (micro-XRF) to quantify mineral assemblages of the Beauvoir granite. Modal abundances were compared with normative proportions derived from whole-rock geochemistry. In fresh facies with Li contents between 4000 and 6000 ppm, albite and quartz dominate (~40% and 25%), respectively, while lepidolite averages 20%–25%. During alteration to greisen, feldspars and lepidolite are partly replaced by muscovite, reducing lepidolite by up to threefold and increasing muscovite to ~30%. The obtained results demonstrate that micro-XRF provides a fast and reliable method for quantifying mineral distributions in rare-metal granites. Combined with complementary microscale techniques, quantitative mineralogy offers a powerful approach to characterize Li-bearing granites, assess alteration intensity, and improve predictions of ore quality and processability. Full article

This study redefines the Nordestina Kimberlite Province (PKN), in the northeastern sector of the São Francisco Craton (SFC), as a composite kimberlitic–lamproitic system that hosts two genetically distinct magma types: (1) the primitive Braúna kimberlite and (2) hybridized phlogopite-rich lamproites belonging to the SFC lamproite variety. Braúna kimberlites represent an olivine-rich kimberlite sourced from a metasomatized lithospheric mantle, as reflected by its high MgO (15%–30.6%), Ni (up to 1172 ppm), and Cr (up to 2500 ppm). These geochemical signatures are consistent with a primitive melt capable of preserving diamond stability conditions. In contrast, the SFC lamproite variety exhibits strong crustal overprinting, marked by hydrothermal barite–carbonate–silica veining, cristobalite, elevated SiO₂ (up to 80 wt.%), and high LOI (up to 27.5%). These features indicate significant post-magmatic alteration, felsic crust assimilation, and melt hybridization. Textural and mineralogical features found in both magma types, including olivine-phlogopite aggregates, irregular zoning, and disequilibrium assemblages, suggest magma mingling between compositionally distinct melts and/or crystallization under polybaric conditions. These findings clarify long-standing classification controversies by demonstrating that PKN magmatism is not represented by a single rock type but instead spans a continuum spectrum from primitive kimberlite to strongly hybridized lamproite. Regionally, the data reveal that PKN magmatism reflects Paleoproterozoic mantle metasomatism reactivated during Neoproterozoic tectonism. This dual-stage evolution explains the contrasting degrees of primitiveness and hybridization melt signatures observed across the province. Full article

Phosphate is a crucial non-renewable mineral resource, mainly utilized in producing fertilizers that support global agriculture. As phosphorus is an indispensable nutrient for plant growth, phosphate holds a key position in ensuring food security. While deposits are distributed worldwide, the largest reserves are concentrated in Morocco. The Benguerir phosphate mining in Morocco generates heterogeneous waste (i.e., including overburden, tailings, and phosphogypsum) that complicates management and valorization, which is the beneficial reuse or value recovery from waste materials (e.g., use in cover systems, buffering, or other engineered applications). Therefore, it is essential to characterize their mineralogical properties to evaluate their environmental impact and possibilities for reuse or site revegetation. To do so, we integrate VNIR–SWIR reflectance spectroscopy with HandHeld X-ray fluorescence (HHXRF) to characterize phosphate waste rock and assess its reuse potential. For this purpose, field samples (n = 104) were collected, and their spectral reflectance was measured using an ASD FieldSpec 4 spectroradiometer (350–2500 nm) under standardized laboratory conditions. Spectra were processed (Savitzky–Golay smoothing, convex-hull continuum removal) and matched to ECOSTRESS library references; across the dataset, library matching achieved mean RMSE = 0.15 ± 0.053 (median 0.145; 0.085–0.350), median SAM = 0.134 rad, median SID = 0.029, and mean R² = 0.748 ± 0.170, with 84% of spectra yielding R² > 0.70. In parallel, HHXRF major and trace elements were measured on all samples to corroborate spectral interpretations. Together, these analyses resolve carbonate–clay–phosphate assemblages (dolomite commonly dominant, with illite/smectite–kaolinite, quartz, and residual carbonate-fluorapatite varying across samples). Elemental ratios (e.g., Mg/Ca distinguishing dolomite from calcite; K/Al indicating illite) reinforce spectral trends, and phosphate indicators delineate localized enrichment (P₂O₅ up to 23.86 wt % in apatite-rich samples). Overall, the combined workflow is rapid, low-impact, and reproducible, yielding coherent mineralogical patterns that align across spectroscopic and geochemical lines of evidence and providing actionable inputs for selective screening, targeted material reuse, and more sustainable mine reclamation planning. Full article

To clarify the organic matter enrichment regularity of Permian shales in the Kaijiang–Liangping Trough, as well as the differential characteristics of their reservoir lithology, mineral assemblage, and nanopore structure—and thereby provide a geological basis for the exploration and development of Permian marine shales in the eastern Sichuan Basin—core samples from different depths of the Wujiaping Formation and Dalong Formation in Well DY-1H were analyzed using a series of micro–nano technical research methods, including whole-rock X-ray diffraction, major/trace element analysis, conventional porosity-permeability measurement, high-pressure mercury intrusion porosimetry, nitrogen adsorption, and field emission scanning electron microscopy. Research finds that the Dalong Formation shale contains Type I organic matter with high abundance, whereas the Wujiaping Formation shale is dominated by Type II₂ organic matter. The Wujiaping Formation experienced stronger terrigenous input and higher weathering intensity, while the Dalong Formation was deposited under persistently anoxic conditions, in contrast to the frequent oxic–anoxic alternations in the Wujiaping Formation. Paleoproductivity indicators suggest higher productivity in the Dalong Formation than in the Wujiaping Formation. Mo/TOC ratios below 4.5 indicate deposition in a strongly restricted water body. Enrichment factors of multiple elements further support the enhanced paleoproductivity of the Dalong Formation. The Dalong Formation shale has higher contents of quartz and carbonate minerals, while the Wujiaping Formation shale has a higher content of clay minerals. The Wujiaping Formation shale is more developed with inorganic micropores, whereas the Dalong Formation shale is characterized by more developed organic nanopores. During the sedimentary period of the Dalong Formation shale, the paleoproductivity was high, the sedimentary waterbody had high reducibility and restriction, and the reservoir was well-developed with nanopores. The Dalong Formation is a more favorable interval for Permian shale gas exploration and development in the Kaijiang–Liangping Trough. Full article

For the first time, the same fish species is recorded from Triassic rocks at both ends of the Tethys, namely, Thoracopterus wushaensis Tintori et al., 2012. First described from the southwestern China Xingyi Fauna (late Ladinian, Middle Triassic), it is now also known from a coeval site in the Dolomites in northern Italy. T. wushaensis is considered a flying fish, owing to its elongated pectoral and pelvic fins, tail with a ventral lobe much larger than the dorsal one, and peculiar enlarged neural spines in the caudal region. Taxonomical problems among Peltopleuriformes are also discussed on the basis of an improved comparison between eastern and western Tethys fish assemblages. This finding bolsters the marine vertebrate similarity between China and Europe during the Middle Triassic. Furthermore, because T. wushaensis from the Pelsa/Vazzoler is part of a very rich assemblage yielding several fishes, and also dozens of invertebrate taxa, it also supports the hypothesis of a global bioevent among marine fauna during the late Ladinian, well before the San Cassiano Fauna or the Carnian Pluvial Episode. Full article

The processes responsible for high-grade disseminated gold mineralization remain poorly constrained, hindering effective exploration. This study integrates petrography, BPMA, and LA-ICP-MS analysis of magnetite from marble- and granite-hosted ores with contrasting gold grades, to constrain wall-rock-induced changes in the thermodynamic environment. BPMA results show distinct mineral assemblages: granite-hosted ores are characterized by quartz (52.31%)-K-feldspar (19.65%)-sericite (9.56%)-pyrite (8.36%), whereas marble-hosted ores feature pyrrhotite (33.90%)-chlorite (27.50%)-pyrite (15.22%)-magnetite (1.94%). The closed intergrowths of magnetite with gold and sulfides, along with the magnetite Ga-V (Grant-Vaughan) discrimination diagram, indicate a hydrothermal origin for magnetite formed during the mineralization stage. Geochemical data show that marble-hosted magnetite has lower V and chalcophile element (Co, Ni, Sn, Zn) concentrations than granite-hosted magnetite. Considering the partitioning behavior of these elements in magnetite, these differences indicate magnetite crystallization under increasing oxygen fugacity (fO₂) and decreasing sulfur fugacity (fS₂). Thermodynamic modeling results demonstrate that these changes in fO₂ and fS₂ destabilized gold-sulfur complexes in the ore-forming fluid, significantly enhancing gold precipitation efficiency and ultimately leading to the formation of high-grade ores in marble. Full article