Abstract:

Water quality assessment is crucial for the sustainable use and management of groundwater resources. This study was carried out in the irrigated plains of Vehari District, Punjab, Pakistan, to evaluate groundwater suitability for a managed aquifer recharge (MAR) project. Twenty-three groundwater samples were collected in June 2021 from an area of 1,522 km² and analyzed for major physicochemical parameters including electrical conductivity (EC), total dissolved solids (TDS), pH, turbidity, calcium (Ca), magnesium (Mg), chloride (Cl), alkalinity (Alk), bicarbonate (HCO₃⁻), hardness, potassium (K), sulphate (SO₄²⁻), sodium (Na), and nitrate (NO₃⁻). Water quality was assessed using WHO and PID standards, alongside derived hydrochemical indices such as sodium percentage (%Na), Kelley’s ratio (KR), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and the water quality index (WQI). The dataset was interpreted using geo-statistical, geospatial, multivariate, and correlation analyses. Cation and anion dominance followed the order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > SO₄²⁻ > Cl⁻ > NO₃⁻. WQI results showed that 35% of samples indicate “poor,” 50% “very poor,” and 15% “unsuitable” drinking-water quality. However, irrigation suitability indices confirmed that groundwater is generally acceptable for agricultural use, though unfit for drinking. The outcomes of this study provide essential insights for groundwater management in the region, where the Punjab Irrigation Department (PID) has initiated a MAR project. Considering that the irrigation sector is the major groundwater consumer in the area, the compatibility of groundwater and surface water quality supports the implementation of MAR to enhance agricultural sustainability.

Abstract: Detailed geochemical modelling of the potential groundwater impacts of CO2 geo-sequestration requires site-specific knowledge of how mobile elements are hosted within rocks. We present a simple sequential extraction procedure analogous to pH conditions produced by different partial pressures of carbon dioxide (CO2) in contact with water. The procedure consists of three sequential steps: Water at pH 7; acetic acid–ammonium acetate at pH 5 and then at pH 3, with the amounts of specific elements extracted by each step considered with respect to whole-rock total element abundance. Our purpose in developing this procedure is three-fold: 1) identify readily mobilised suites of elements for groundwater baseline and monitor bore studies; 2) provide insights regarding the mode/s of occurrence of easily extracted elements within rock samples; and 3) suggest possible mechanisms for the mobilisation of rock-sourced elements into groundwater under neutral to moderately acidic pH that can inform reactive transport modelling of carbon storage sites. In our case study, the second step extracted most of the main mobile elements of interest.

Abstract: Birnessite is a layered manganese oxide with strong oxidizing ability, but the electronic reason for this property is still unclear. In this work, eight birnessite samples with different interlayer cations and Mn(III)/Mn(IV) ratios were studied to explore how electron affinity (EA) affects oxidation behavior. The samples were examined by XRD, XPS, SEM and UPS, and oxidation tests were carried out with Fe(II) and phenol under controlled pH and temperature. The electron affinity values ranged from 5.52 to 5.93 eV, increasing from Na⁺- to K⁺-, Ca²⁺- and Mg²⁺-birnessite. Samples with higher EA showed faster oxidation, and the Fe(II) removal rate was about 2.1 times higher than that of low-EA samples. The relationship between EA and rate constant followed an exponential trend (R² = 0.96). Surface and spectral data showed that samples with higher EA had slower Mn(IV) loss and later surface passivation. These results show that electron affinity controls the oxidizing ability of birnessite and can be used to predict and improve the performance of manganese oxides in pollutant removal and catalytic oxidation.

Abstract: We have investigated the major- and trace-element composition of hydrothermal pyrite, magnetite, and titanomagnetite, and of the principal Cu-minerals chalcopy-rite and chalcocite, to constrain ore-forming processes in the northeastern Saveh district (central Urumieh–Dokhtar magmatic arc, Iran). Our data provide new con-straints on the magmatic–hydrothermal evolution and subsequent hydrothermal–supergene modification of the ore system. Titanomagnetites hosted in shallow monzo-dioritic intrusions are enriched in Ti–V–Al, plot below the magnetite–ulvöspinel join and record high crystallization temperatures (< ~500 °C) under rela-tively low oxygen fugacity. By contrast, magnetites from silica-rich hydrothermal veins are relatively Fe-rich, have very low TiO₂, formed at intermediate tempera-tures (~200–300 °C) under higher fO₂, and show pronounced depletion in Ti and V relative to monzo-dioritic oxides. Textures and oxide systematics (Al+Mn vs Ti+V; V/Ti–Fe) document repeated hydrothermal pulses, Fe²⁺ leaching and element redis-tribution during cooling and fluid–rock interaction. Geochemical trends indicate progressive evolution from a magmatic fluid to later meteoric water overprint, with decreasing As contents reflecting mixing with oxidizing meteoric waters. Vertical elemental zoning suggests that most samples represent mid- to deep-level sections of the epithermal system. Elevated Cu contents (up to 0.95 wt.%) highlight pyrite as a significant Cu host. Co/Ni ratios between 1 and 10 further corroborate a magmatic–hydrothermal origin. Chalcopyrite is the principal economic Cu carrier at Northeast Saveh. Replacement follows a temperature- and fluid-controlled pathway (chalco-pyrite → covellite → chalcocite/digenite). At lower temperatures (< ~200 °C) re-placement proceeds more slowly, producing chalcocite/digenite under prolonged reaction conditions. Chalcocite commonly occurs as thin replacement rims and fracture fills that concentrate remobilized copper. Collectively, the investigated oxide and sulfide proxies provide robust discriminants for separating magmatic versus hydrothermal domains and for vectoring toward higher-temperature feeders and zones of remobilized copper.

Abstract: The magmatic activity is crucial for identify the tectonic framework of ancient ocean. In this study, a systematically work including field survey, zircon LA-ICP-MS U-Pb dating, and whole-rock geochemical analysis is carried on to investigated the intrusive magmatic rocks of quartz diorite and granodiorite within the Meso-Tethyan Shiquanhe Ophiolitic Mélange (SQM), Tibet. Zircon U-Pb dating yields the weighted mean ages of 174.7±1.4 Ma (quartz diorite) and 178.9±1.2 Ma (granodiorite) respectively, indicating the Early Jurassic formation age. The quartz diorite is metaluminous (A/NKC = 0.77-0.95), while the granodiorite is weakly peraluminous (A/NKC = 0.95-1.21), and both of them exhibit tholeiitic–calc-alkaline geochemical characteristics and classified as I-type granites. The right-dipping rare earth element (REE) patterns, enrichment in large ion lithophile elements (LILEs: Rb, Ba, Th), and depletion in high field strength elements (HFSEs: Nb, Ta, Ti), as well as relatively high (La/Yb)N ratios represent the is-land arc TTG-like magmatism origin. Combine with the previous works, we suggest the Shiquanhe opiolitic mélange represent an island arc and back-arc assemblage rather than an independent ocean basin. Meanwhile, this Early Jurassic island arc magmatism initiated a new era of the Mesozoic mineralization in Shiquanhe area.

Abstract:

Understanding how processes of magma genesis and magma differentiation control and modify the chemical composition of erupted lavas from the geochemical measurements of the latter is an under-constrained inverse problem as there is only one known parameter – the measured composition of the erupted lava – but two unknown parameters – the chemical composition and lithology of the source before melting and how melting, crystallization, and melt-rock interactions act to alter the lava en route to the surface. In this invited contribution, we review nearly seven decades of scientific research that demonstrate the potential of U and Th decay series measurements for unraveling the complexities of oceanic magmatism. We review the underlying nuclear theory, geochemical principles, and application of the ²³⁸U, ²³⁵U, and ²³²Th decay series for (i) defining the timescales of magma genesis during decompression mantle melting, (ii) establishing the timescales of magma recharge and magma degassing, and (iii) determining the eruption ages of oceanic Quaternary volcanism.

Abstract:

Pt-Fe alloys with abundant inclusions from the Camumbi River placer deposit, Ecuador, are derived from unknown Alaskan-Uralian type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Our previously documented silicate inclusions are increasingly fractionated from hydrous ferrobasalt to rhyolite in terms of TAS (total alkalis vs. silica). Liquid lines of descent change from tholeiitic to the calc-alkaline magma series. Here, we document seven exceptional composite inclusion parageneses of Cu–PGM (platinum-group mineral) sulfides, each exsolved from coexisting, fractionated silicate glass (melt). Differentiation is dominated by fractional crystallization in PGM bulk compositions from tholeiitic silicate melts at highest T ~1018 °C. Silicate inclusions following the lower T calc-alkaline trend coexist with sulfide PGMs likely differentiated (in terms of Pt-Rh-Pd and BMs, base metals) by incongruent melting due to decompression and S-degassing at ~983–830 °C. S-saturated sulfide melts become S-undersaturated below 845 °C. Calculated Ts are for silicate glass. Pt-rich braggite shows increasing fractionation towards Pd-rich vysotskite within one inclusion paragenesis. A late braggite–vysotskite trend is towards decreasing minor BMs. Thiospinels are dominated by cuprorhodsite. Minor thiospinels indicate Fe- then strong Ni-enrichment at lowest Ts. Decompression exsolutions, deflation and partial melting of some sulfide inclusion parageneses support rapid ascent to higher crustal levels within a deep-sourced cumulate intrusion.

Abstract: Synthesis of published and new data from Govorov and Kocebu guyots provides geochemical and chronostratigraphic constraints on hydrogenetic cobalt-rich Fe-Mn crusts from the Western Pacific Magellan Seamount Trail (MST). The history of the crusts began about 65–60 Myr ago, when the relict layer R was deposited in the Campanian–Maastrichtian and Late Paleocene along the shores of guyots. The growth of the old-generation crusts continued in the Late Paleocene–Early Eocene (Layer I-1) and in the Middle–Late Eocene (Layer I-2) in a shallow-water shelf environment. The younger layers of crusts formed in the Late Oligocene–Early Miocene (Layer I-2b), Miocene (Layer II), and Pliocene–Pleistocene (Layer III) at depths about the present sealevel. The precipitation of Fe and Mn oxyhydroxides from seawater was interrupted by several episodes of dissolution, the longest one between the old and young layers of Fe-Mn crusts (from 38 to 26.5 Ma). Fe and Mn oxyhydroxides in the crusts were affected by two global events of phosphogenesis in the Pacific: Late Eocene–Early Oligocene, from 43 to 39 Ma (Layers R, I-1, I-2) and Late Oligocene–Early Miocene, from 27 to 21 Ma (Layer I-2b). The trace element patterns in different layers of the Fe-Mn crusts are grouped using factor analysis of principal components (varimax raw) into four factors: (1) + (all REEs except Ce and La); (2) +(Ce, La, Ba, Mo, Sr, Pb); (3) +(Zr, Hf, Nb, Rb, As)/-Pb; (4) +(U, Th, Co, As, Sb, W)/-Y. The factor score diagrams highlight fields which are especially contrasting for Layers I-1, I-2 and II+III according to factors 2 and 4. Consistent REE and Y variations in Layers I-2b→II →III of the crust from Pallada Guyot correlate with gradual ocean deepening between the Late Oligocene–Early Miocene and Present when the MST guyots were submerging. Large variations in trace element contents across coeval layers may be due to hydrodynamics of currents on the guyot surfaces. Furthermore, the geochemistry of the crusts bears effects from repeated episodes of Cenozoic volcanism in the MST region of the Pacific Plate. Higher contents of Nb, Zr, As, Sb, and W in the younger layers II and III may result from large-scale volcanism, including Miocene eruptions of petit-spot volcanoes.

Abstract:

The origin of Mesozoic granites associated with the Dahutang W-Cu-Mo orefield in north Jiangxi, which host the world’s second largest tungsten deposit, remains a compelling subject despite extensive geochemical and geochronological studies. In this contribution we present new wolframite mineral and bulk-rock geochemistry and monazite U-Pb ages for the Mesozoic granites in aiming to enhance our understanding the petrogenesis of these granites and its coupling relationship with the mineralization. Two magmatic phases and four types of rocks in study area are identified, i.e., the early stage (152-147 Ma) biotite (G1) granite and the late stage (144-130 Ma) two-mica (G2)＋muscovite (G3)＋albite (G4) granite series. These two magmatic phases are temporally coincident with two mineralization stages (~150 Ma and 139-144 Ma). All the Mesozoic granites share the characteristics of high silica content, peraluminosity (A/CNK > 1.1), and low Zr+Nb+Ce+Y values (< 200 ppm), and they are derived from the partial melting of a Proterozoic crustal source. Specifically, the G1 granite, characterized by relatively high MgO (~0.5%), CaO (~1%), and low P₂O₅(0.13%-0.20%), is classified as an I-type granite. It formed via a relatively higher degree of partial melting at ~766°C (Zr saturation temperatures) driven by biotite breakdown reactions, with minor contributions from mantle-derived materials. In contrast, the G2–G4 granites series exhibits typical peraluminous S-type granite features, such as high Al₂O₃, Na₂O, and P₂O₅ (mostly >0.2%) contents, and low Sr and Ba contents. They are products of low-degree partial melting that occurred under conditions close to muscovite breakdown at ~735°C. Additionally, both granites show clear geochemical evidence of fluid interaction, as reflected by their elevated trace element and volatile contents: Sn>30 ppm, Cs >35 ppm, F >0.4%, Li >250 ppm, W 10–1000 ppm, Rb >500 ppm, K/Rb values <150, and Nb/Ta<5. The G1 granite represents a moderately fractionated melt relative to chondrites, as evidenced by its near-chondritic Zr/Hf (22.6-34.1) and Y/Ho (24.5-31.5) ratios, indicating a weaker influence of magmatic fluid-melt interaction. For the G2-G4 granites, however, intense crystal fractionation and late-stage fluid-melt interaction are well-documented by their highly variable and low ratios of Y/Ho (14.8-41.4), Nb/Ta (0.89-5.57), Zr/Hf (8.84-41.67), and K/Rb (13.96-128.29). In the long-lived, reduced, and volatile-rich aqueous environment of the G2–G4 magmas, fractional crystallization and albitization collectively enhanced the solubility and hydrothermal transport capacity of W, Sn, Li, Nb, and Ta by multiple orders of magnitude. In contrast, in the earlier, more oxidized G1 magma (which incorporated mantle materials), the exsolution and hydrothermal transport of Cu and Mo were associated with localized greisenization, but their capacity diminished with fractional crystallization. Historically, mineral exploration in the Dalutang mining area has focused primarily on W, Cu, and Mo. Based on this research, we conclude that there is significant mineral potential for rare metals (particularly Sn, Li, and Ta), and future surveys should prioritize areas adjacent to the evolved G2–G4 peraluminous leucogranites to search for new concealed mineral occurrences.

Abstract: Zibai Jade is a recently identified hydrogrossular-dominant jade originating from Shaanxi Province, China. It constitutes a polymineralic aggregate composed predominantly of hydrogrossular, with minor proportions of vesuvianite, diopside, chlorite, uvarovite, and calcite. A multi-method analytical approach was employed to characterize the jade, incorporating conventional gemological testing, polarizing microscopy, SEM, XRD, BSE, XRF, EPMA, as well as UV-Vis, infrared IR. These techniques enabled a detailed examination of its mineralogy, surface features, and color origin. The stone displays heterogeneous color distribution, featuring a base hue of light green to yellowish-green, accompanied by distinct occurrences of emerald-green spots, dark green spots, mossy green inclusions, white patches, white veinlets, and black dot with a green ring.Microanalytical results indicate that the emerald-green spots are principally composed of uvarovite. The dark green sports are dominated by hydrogrossular, diopside, and chlorite. Fibrous green inclusions consist mainly of chlorite and Cr-bearing grossular. White patches and veinlets are primarily composed of calcite. The black dot with a green ring are predominantly comprised of chromite and uvarovite.Coloration is attributed to the combined influence of Fe and Cr3+. The formation of the jade involved three mineralization stages: protolith accumulation, high-temperature metasomatism, and retrograde alteration. The interplay of these processes resulted in the development of Zibai Jade, which exhibits a dense texture and attractive coloration.

Abstract: The He 1 Member of the Xiashihezi Formation (Upper Paleozoic) in the Ordos Basin represents typical tight sandstones. However, against the extensive tight sandstone background of the He 1 Member in the southern basin, conventional reservoirs (Φ>12%, K>1 mD) occur locally. Elucidating the genetic mechanism of these conventional reservoirs is critical for evaluating gas reservoirs in this region. Based on core descriptions and systematic sampling from cored wells, reservoir types are classified according to pore types and porosity in sandstones. Depositional microfacies, petrology, and diagenesis of each reservoir type are then investigated to ultimately elucidate the genetic mechanism of conventional reservoirs. Results demonstrate that intense compaction and quartz overgrowths are the primary controls on the development of the He 1 Member tight sandstones. Alteration of volcanic lithic fragments and volcanic ash matrix generated abundant intragranular dissolution pores and micropores within matrix, while simultaneously producing substantial illite-smectite mixed-layer clays and chlorite clays. Additionally, this process supplied silica for quartz overgrowths. Moderate amounts of chlorite coatings can inhibit quartz overgrowths, thereby preserving residual intergranular porosity. Conventional reservoirs exhibit low lithic fragment content and coexisting intergranular and intragranular dissolution porosity. Their formation requires weak compaction, intense dissolution, and weak quartz overgrowths. These reservoirs develop within high-energy transverse bars that are sealed by overlying and underlying mudstones. Such transverse bars constitute closed intrastratial-diagenetic systems with restricted mass transfer during burial. This study provides a compelling example of diagenetic heterogeneity induced by variations in sandstone architecture within fluvial successions.

Abstract: This study presents the application of Mycelial_Net, a biologically inspired deep learning architecture, to the analysis and classification of mineral images in thin section under optical microscopy. The model, inspired by the adaptive connectivity of fungal mycelium networks, was trained on a test mineral image database to extract structural features and to classify various minerals. The performance of Mycelial_Net was evaluated in terms of accuracy, robustness, and adaptability, and compared against conventional convolutional neural networks. The results demonstrate that Mycelial_Net, properly integrated with Residual Networks (ResNets), offers superior analysis capabilities, interpretability, and resilience to noise and artifacts in petrographic images. This approach holds promise for advancing automated mineral identification and geological analysis through adaptive AI systems.

Abstract: Marine deposits in Western Europe provide insight into the interplay between the warm Tethys and cooler Boreal domains, offering a climatic context for the radiation of Early Jurassic species. Reconstructions of temperature for the Hettangian and Sinemurian periods are scarce, with inferred marine temperatures of 15–20°C based on δ18O values, which are lower than those of subsequent Jurassic stages. This emphasises the necessity for supplementary data in order to enhance our comprehension of the climatic dynamics that characterised the Early Jurassic period. This study analyses 75 invertebrate samples, including 53 specimens of Gryphaea arcuata, from Early Sinemurian marine sediments in the Fresville quarry, Normandy, France. The present study employs a multi-proxy approach, utilising δ13C and δ18O values in conjunction with Sr and Mg contents, to assess the processes of fossil diagenesis, marine productivity and seawater temperatures. Significant post-depositional alteration was observed in the geochemical compositions of 22 bivalve shells assigned to the genera Pseudolimea, Plagiostoma and Chlamys, which were originally composed of aragonite. However, the low-Mg calcite shells of Gryphaea arcuata, which are renowned for their diagenetic resistance, retained the majority of their isotopic integrity. The results of the statistical analyses indicate that there was minimal late pervasive diagenesis involving meteoric waters at Fresville. This is in accordance with the typical decrease in δ13C, δ18O values and Sr and Mg contents that such processes would otherwise cause. Published isotopic data from Sinemurian marine fossils (plesiosaur and shark teeth) were used to estimate seawater δ18O (~ -1‰ VSMOW or -1.27‰ VPDB) and surface temperatures (~24°C). The calculated benthic temperatures of Gryphaea (17°C) correspond to habitats at depths of about 50 m. These findings suggest a positive hydrological balance, euhaline conditions, and elevated marine productivity in a humid tropical climate context.

Abstract: This study investigates the Terrigenous-carbonate Sakar-type Triassic (TCSTT) and Sakar-type Triassic (STT) metasedimentary successions in the Sakar Unit, SE Bulgaria. Both share lithological similarities (alternation of carbonate-silicate schists, mica schists, marbles, and impure marbles) and are affected by post-Triassic metamorphism, but exhibit differences in metamorphic grade and provenance. The STT displays a higher metamorphic grade (low amphibolite facies) compared to the TCSTT (low greenschist facies). Petrographic observations and geochemical analyses indicate protoliths composed of arkosic sandstones, shales, and limestones, derived from a quartz-dominated source with minor contributions from intermediate magmatic sources. U-Pb geochronology of detrital zircons reveals a dominant Carboniferous age, supplemented by early Ordovician ages, consistent with the presence of Carboniferous-Permian magmatic rocks in the basement. The presence of Early Paleozoic and Cambrian-Neoproterozoic zircons in the detrital zircon populations suggests that older rocks in the basement of the Sakar Unit and Srednogorie zone are also sources of the sedimentary material. Based on immobile trace elements contents and discrimination diagrams, the siliciclastic component comes from rocks formed in a continental arc tectonic setting. REE patterns exhibit a negative Eu anomaly, inherited from the granitic source rocks.

Abstract: Underground hydrogen storage (UHS) in carbonate and siliceous formations presents a promising solution for managing intermittent renewable energy. However, experimental data on hydrogen-rock interactions under representative subsurface conditions remains limited. This study systematically investigates mineralogical and petrophysical altera-tions in dolomite, calcite-rich limestone, and quartz-dominant siliceous cores subjected to high-pressure hydrogen (100 bar, 70°C, 100 days). Distinct from prior research focused on diffraction peak shifts, our analysis prioritizes quantitative changes in mineral concentra-tion (%) as a direct metric of reactivity and structural integrity, offering more robust in-sights into long-term storage viability. Hydrogen exposure induced significant dolomite dissolution, evidenced by reduced crys-talline content (from 12.20% to 10.53%) and accessory phase loss, indicative of partial de-carbonation and ankerite-like formation via cation exchange. Conversely, limestone ex-hibited more pronounced carbonate reduction (vaterite from 6.05% to 4.82% and calcite from 2.35% to 0%), signaling high reactivity, mineral instability, and potential pore clog-ging from secondary precipitation. In contrast, quartz-rich cores demonstrated exceptional chemical inertness, maintaining consistent mineral concentrations. Furthermore, BET and BJH analyses revealed enhanced porosity and permeability in do-lomite (pore volume increased >10x), while calcite showed declining properties and quartz negligible changes. SEM-EDS supported these trends, detailing Fe migration and textural evolution in dolomite, microfissuring in calcite, and structural preservation in quartz. This research establishes a unique experimental framework for understanding hydrogen–rock interactions under reservoir-relevant conditions. It provides crucial insights into mineralogical compatibility and structural resilience for UHS, identifying dolomite as a highly promising host and highlighting calcitic rocks limitations for long-term hydrogen containment.

Abstract: The Tuztaşı low-sulfidation epithermal Au–Ag deposit (Biga Peninsula, Türkiye) records a multi-stage hydrothermal history that can be decoded through the trace- and rare-earth-element (REE) chemistry of quartz. High-precision LA-ICP-MS analysis of five representative quartz samples (23 ablation spots; 10 analytically robust) reveal two fluid stages. Early fluids were cold, dilute meteoric waters (δ¹⁸O₍H₂O₎ ≈ –6.8 to +0.7 ‰), whereas later fluids circulated deeper, interacted with felsic basement rocks, and evolved chemically. Mineralized quartz displays marked enrichment in As (raw mean = 2 854 ± 6 821 ppm; filtered mean = 70 ± 93 ppm; one spot 16 775 ppm), K (498 ± 179 ppm), and Sb (57.8 ± 113 ppm), coupled with low Ti/Al (&lt; 0.005) and elevated Ge/Si (0.14–0.65 µmol mol⁻¹). Chondrite-normalized REE patterns show pronounced but heterogeneous LREE enrichment ((La/Yb)ₙ ≤ 45.3; ΣLREE/ΣHREE up to 10.8) and strongly positive Eu anomalies (δEu ≤ 9.3) with slightly negative Ce anomalies (δCe ≈ 0.29); negligible Ce–Eu covariance (r² ≈ 0.05) indicates discrete redox pulses. These signatures pinpoint chemically evolved, reducing fluids conducive to Au–Ag deposition. By contrast, barren quartz is characterized by lower pathfinder-element contents, flatter REE profiles, higher Ti/Al, and subdued Eu anomalies. A composite exploration toolkit emerges: As &gt; 700 ppm, As/Sb &gt; 25, Ti/Al &lt; 0.005, Ge/Si &gt; 0.15 µmol mol⁻¹, and δEu ≫ 1 reliably demarcate ore-bearing zones when integrated with δ¹⁸O data, fluid-inclusion microthermometry, and structural mapping. The study provides one of the first systematic applications of integrated trace-element and REE analysis of quartz to a Turkish low-sulfidation epithermal system, offering a transferable template for vectoring mineralization in analogous settings worldwide

Abstract: Understanding mineral–fluid interactions in shale under supercritical CO₂ (scCO₂) conditions is relevant for assessing long-term geochemical containment. This study characterizes mineralogical transformations and elemental redistribution in five Caney Shale samples serving as proxies for reservoir (R1, R2, R3) and caprock (D1, D2) facies, subjected to 30-day static exposure to pure scCO₂ at 60 °C and 100 bars (2500 psi), with no brine or impurities introduced. SEM-EDS analyses were conducted before and after exposure, with mineral phases classified into silicates, carbonates, sulfides, and organic matter. Initial compositions were dominated by quartz (38–47 wt%), illite (16–23 wt%), carbonates (12–18 wt%), and organic matter (8–11 wt%). Post-exposure, carbonate loss ranged from 15–40% in reservoir samples and up to 20% in caprock samples. Illite and K-feldspar showed depletion of Fe²⁺, Mg²⁺, and K⁺ at grain edges and cleavages, while pyrite underwent oxidation with Fe redistribution. Organic matter exhibited scCO₂-induced surface alteration and apparent sorption effects, most pronounced in R2 and R3. Elemental mapping revealed Ca²⁺, Mg²⁺, Fe²⁺, and Si⁴⁺ mobilization near reactive interfaces, though no secondary mineral precipitates formed. Reservoir samples developed localized porosity, whereas caprock samples retained more structural clay integrity. Results advance understanding of mineral reactivity and elemental fluxes in shale-based CO₂ sequestration.

Abstract: Determining carbon sources and sinks is crucial for understanding the global carbon cycle; however, the enigma of the 'missing' sinks remains unresolved. Recent studies have proposed carbonate weathering as a potential carbon sink, underscoring the need to clarify its mechanisms. Previous investigations of carbonate weathering largely relied on soil profiles, which were limited by the rarity of incipient weathering layers. Therefore, we have little knowledge about carbonate incipient weathering processes. To address this gap, spheroidal-weathered dolostones were collected from Neoproterozoic Liangjiehe Formation (Nanhua System) in Guizhou, China. The pristine dolostone exhibits δ¹³C values ranging from -5.26 to -3.35‰ and δ¹⁸O values from -13.79 to -12.83‰. These isotopic signatures suggest that the dolostone formed under the high-latitude, cold climatic conditions that were prevalent during the Nanhua Period. Comprehensive petrographic and geochemical analyses of the spheroidal-weathered dolostones revealed two distinct stages of incipient weathering. In Stage I, nickel (Ni) and cobalt (Co) contents decrease. The δ¹³C values fluctuate between -7.61 and -2.52‰, while δ¹⁸O values range from -12.22 to -8.06‰. These observations indicate a weakly acidic microenvironment. In Stage II, there is an enrichment of manganese (Mn), with δ¹³C values extending from -16.56 to -12.43‰ and δ¹⁸O values from -8.46 to -7.03‰. These clues suggest a transition to a neutral microenvironment, with the isotopic compositions of carbon and oxygen in the dolomite influenced by atmospheric carbon dioxide (CO₂) and atmospheric precipitation. This study presents a pioneering investigation into the mineralogical and geochemical variations associated with carbonate incipient weathering processes. The variation in C-O isotopes during carbonate incipient weathering may indicate the re-precipitation of HCO₃^⁻, suggesting that the carbon-sink contribution of carbonate weathering to the global carbon cycle could be overestimated.

Abstract: Cochin backwater region in Southern India is one of the most dynamic estuaries, strongly influenced by seasonal river runoff and seawater intrusion. This study explores the rela-tionship between monsoonal rains, salinity, and stable isotopic composition (δ¹⁸O and δ¹³C) to estimate the contribution of freshwater fluxes at different seasonal intervals for the Cochin Backwater (CBW) estuary. Seasonal variations in oxygen isotopes and salinity re-vealed distinct trends indicative of freshwater-seawater mixing dynamics. The compari-son of Local and Global Meteoric Water Lines highlighted enriched isotope values during the pre-monsoon season, showing significant evaporation effects. Carbon (C) isotopic analysis in dissolved inorganic matter (δ¹³CDIC) at 17 stations during the pre-monsoon season revealed spatially distinct carbon dynamics zones, influenced by various sources. These characteristic zones were Zone 1, dominated by seawater, exhibited heavier δ¹³CDIC values; Zone 2 showing significant contributions of lighter terrestrial δ¹³C; while Zone 3 reflected inputs from regional and local paddy fields with a distinct C3 isotopic signature (-25‰), modified by estuarine productivity. In addition, different advanced machine learning techniques were tested to improve analysis and prediction of seasonal variations in isotopic composition and salinity. The combination of these advanced machine learn-ing models not only improved the predictive accuracy of seasonal freshwater fluxes but also provided a robust framework for understanding the estuarine ecosystem and would pave way for better management and conservation strategies.

Abstract: Despite the shale revolution triggering global shale oil and gas exploration, our understanding of the sedimentary environments of deep-water organic-matter-rich shale remains unclear. Hence, we analyzed the sedimentary environment and facies of some siliceous shales at the bottom of the Longmaxi Formation in the Weiyuan area of the Sichuan Basin, China. Nano-resolution petrological characterization and genesis analysis of the siliceous shales were conducted using the nano-resolution petrologic image datasets. We identified these siliceous shales as the microbial mats formed by the deep-water traction current sedimentation. The microbial mat's formation and burial diagenesis processes were divided into seven stages. The silt-grade bioclastic beach deposits initially, colonizing the mud-grade siliceous microbes and forming the siliceous microbial mat. Subsequently, the carbohydrate-rich microbes thrive in sediment voids, forming the carbohydrate-rich microbial mat. Additionally, SOM undergoes the four stage of burial diagenesis process, progressing from the kerogens to the pre-oil bitumen generation and ultimately transforming into the porous pyrobitumen and the nonporous pyrobitumen. The study deepens the understanding of the deep-water traction current sedimentation and has implications for guiding shale gas exploration and development.