Permian–Triassic granitoids are widely distributed along the Jinshajiang suture belt, eastern Tibet, and are regarded as the result of the tectonic-magmatic activity associated with the evolution of Paleo-Tethys Ocean. This paper focuses on the high-K calc-alkaline I-type Rennong (~235 Ma) and Jiaduoling (~232 Ma) granitoid plutons, eastern Tibet, which are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs), but depleted in high field strength elements (HFSEs) with moderate-weak negative Eu anomalies (0.61–0.90). The Rennong granites are characterized by uniform zircon ε_Hf(t) values (-7.3 to -3.5) and negative ε_Nd(t) values (-7.6 to -5.7), with old two-stage Nd model ages (T_DM2 = 1.51–1.46 Ga) and were likely formed by partial melting of the basement rocks, whereas the Jiaduoling rock samples have variable zircon ε_Hf(t) values (-5.7 to +5.5) but negative ε_Nd(t) values (-7.6 to -7.7) and are proposed to be formed by hybridization of mantle-derived mafic magma, Rennong felsic magma and sediments. Mafic microgranular enclaves (MMEs) in the Jiaduoling granitic rocks, have similar zircon U-Pb ages (~237 Ma) and zircon ε_Hf(t) values (-4.4 to +6.3) to the host rocks, indicating that zircons in the MMEs were actually xenocrysts that formed at an early stage in the granitic magma chamber. These results reveal that the break-off of the Jinshajiang oceanic slab beneath Changdu (Qamdo)-Simao Block was in a post-collisional setting, resulted in the upwelling of asthenosphere in the Late Triassic, and then, generated the wide-spread intermediate-felsic magmatism along the Jinshajing belt, including the Rennong and Jiaduoling plutons.

The Irtysh tectonic belt lies on the southern margin of the Chinese Altai Orogen. Several secondary shear zones with NW-SE strikes have developed in this tectonic belt, and the deformation processes are of great significance to understanding the tectonic regime of the Altai Orogen in the Late Paleozoic. The Tuerhongshate ductile shear zone is located in the eastern Irtysh tectonic belt with obvious deformed structures. The felsic rocks are strongly mylonitized, exhibiting S-C fabrics, asymmetric rotational porphyroclasts, and bookshelf structures of the plagioclases, indicating a sinistral shear sense. The deformation mechanisms, lattice preferred orientations (LPOs) of quartz, and opening angles of quartz c-axis suggest that the deformation temperatures range from 400 to 500 ℃, consistent with higher-greenschist to lower-amphibolite facies conditions. The calculated kinematic vorticity values (W_k) of the studied samples range from 0.53 to 0.89 and indicate general shear to simple shear, based on rotational rigid porphyroclast method and oblique grain-shaped/quartz c-axis fabric method. The U-Pb ages of magmatic zircons in felsic mylonites indicate that the sinistral shear occurred after 296.7 ± 3.0 Ma (Early Permian) in the Tuerhongshate shear zone and persisted for approximately 13 Ma. Combined with the tectonic setting and the observed sinistral strike-slip shear indicators in the mylonite zone, these features demonstrate that the Irtysh tectonic belt was in a post-orogenic and strike-slip environment following the closure of the Irtysh Ocean.

The Ordovician-Silurian transition was marked by extensive volcanic activity globally. In South China, intensive volcanism was documented by abundant ash layers in strata, but the origins and tectonic settings of these ashes remain controversial. This study presents the stratigraphic distribution of volcanic ash layers, zircon trace element and Hf isotope data from the Wanhe Section in the southwestern Yangtze Shelf, providing insights into the tectonic setting and the origin of the parent magmas. The results suggest that volcanic ashes in the southwestern Yangtze Shelf primarily originated from arc magmatism in the Wuyi-Yunkai Orogen, with a mixed source from mantle and crust. The findings corroborate the hypothesis that the Late Ordovician–Silurian Wuyi-Yunkai Orogen in South China represents a collisional orogenic belt.

It has long been recognized that garnet has the capacity to preserve the trace element and isotopic signature of distinct metamorphic growth zones because of its high closure temperature. Combined with the large size of certain garnet porphyroblast, this allows investigating variations in metamorphic conditions such as pressure, temperature, deviatoric stress, and fluid composition, which occur during subduction-related metamorphism. Here, one garnet porphyroblast of 6 cm diameter was sampled from the Yardoi schists of Tibet, and the major-, trace-, and Li-Mg isotopic compositions of distinct growth zones were determined in situ. The δ⁷Li values range from +6.0‰ to +4.1‰ and follow 'S-shaped' patterns on both sides of the garnet's core, revealing a two-stage growth process corresponding to the fluid-assisted sequential recrystallization of chlorite and micas during prograde metamorphism. By contrast, once corrected for the overprinting by retrograde metamorphism, the δ²⁶Mg values vary monotonically from -1.73‰ in the core to -1.32‰ in the outer rim, reflecting a single-step process interpreted to result from increasing temperature and the solid-state recrystallization of chlorite-biotite during prograde metamorphism. This different behavior of Li and Mg isotopes is interpreted to result from the fact that Li is more fluid-mobile than the major element Mg.

Eastern Myanmar is the key position linking between SW Yunnan and northern Thailand for better understanding of Tethyan evolution. However, the actual location and evolution of the Tethyan suture zone are still unclear in eastern Myanmar. The present study focuses on the geochronological, geochemical and zircon Lu-Hf isotopic study on the plutonic rocks, including granite, diorite and gabbroic rocks, from the Tachileik area, eastern Myanmar. These plutonic rocks yielded zircon U-Pb weighted mean ages of ca. 353–355 Ma, suggesting the Early Carboniferous emplacement. The Tachileik granites are high-K calc-alkaline, weakly peraluminous and have low P₂O₅ contents, which are typical features of Ⅰ-type granites. They have positive zircon ε_Hf(t) values (+4.5– +7.4) with T_DM2 ages of 981–825 Ma, indicating a juvenile mafic lower crust source. The Tachileik gabbros and diorites show high Al₂O₃ contents and Mg^#, but low TiO₂ and K₂O contents, belonging to tholeiitic and calc-alkaline basalt series. They are characterized by enrichments in large ion lithophile elements (LILEs, e.g., Rb, Ba and Sr), depletions in high field strength elements (HFSEs) and distinctly negative Nb and Ta anomalies, similar to the volcanic arc basalt. The zircon Hf isotopic (+4.7– +7.1) and whole-rock geochemical data imply that the Tachileik gabros and diorites probably resulted from partial melting of lithospheric mantle in the spinel stability field within an arc-related setting. The magmatic rocks can be grouped to the Late Devonian–Early Carboniferous magmatic rock and pyroclastic rock zone from SW Yunnan to northern Thailand based on their age and geochemical characters. The zone was formed in the post-collisional extension-related tectonic setting of the Proto-Tethys. This study provides important evidences for the evolution of the Proto-Tethys in Southwest Yunnan and Southeast Asia.

Zircon U-Pb ages, major and trace elements and Sr-Nd-Hf isotope data of the diabase in the Zhangjiakou District were studied to investigate its derivation and tectonic implications. Zircon U-Pb ages indicate that the diabase was emplaced at ~130 Ma or younger, and captured zircons cluster at ~147, ~240, ~430 and ~465 Ma. The diabase is characterized by minor variations in SiO₂ (49.35 wt.%–52.10 wt.%), TiO₂ (1.65 wt.%–1.77 wt.%), Al₂O₃ (17.00 wt.%–18.26 wt.%), MgO (4.28 wt.%–4.93 wt.%), CaO (6.69 wt.%–7.90 wt.%) and Mg^# (48–54). It has no significant Eu anomaly and displays enrichment in large ion lithophile elements (Rb, Ba and Sr) and depletion in high field strength elements (Nb, Ta, P and Ti). The diabase exhibits homogeneous Sr ((⁸⁷Sr/⁸⁶Sr)_i = 0.706 06–0.707 01) and Nd (ε_Nd(t) = -13.6 to -13.2) isotopic compositions. These features suggest that the parental magma was derived from partial melting of the ancient lower crust, relating to mantle upwelling that was triggered by the stagnant slabs or lithospheric detachment associated with the westward subduction of the Paleo-Pacific Plate. The Early Paleozoic inherited igneous zircons in the diabase suggest that the northern margin of the North China Craton (NCC) likely underwent southward subduction of the Paleo-Asian Ocean.

The Chinese Altai, a key component of the Central Asian Orogenic Belt (CAOB), represents a significant Phanerozoic accretionary orogenic belt. The oceanic-continental subduction processes spanning the Cambrian to Carboniferous and subsequent intracontinental extension since the Triassic have been well documented in the Chinese Altai, the southwestern segment of the CAOB. Deciphering the petrogenetic evolution of this region during the Permian is thus crucial for advancing our understanding of its tectonic transitions. However, the Permian tectonic setting of the Chinese Altai remains contentious. To address this knowledge gap, this study presents new geochronological and geochemical data for the Jiangjunshan pluton in the southern Chinese Altai. Zircon U-Pb geochronology reveals that the gabbro and two-mica alkali feldspar granite—which collectively constitute the primary lithology of the Jiangjunshan pluton—were emplaced at ~272 ± 3.5 and ~272 ± 1.6 Ma, respectively. Geochemically, the gabbro exhibits pronounced light rare-earth element (LREE) depletion, low Nb/Yb (0.39–0.46) and Ti/V (23.7–25.3) ratios, and trace-element signatures akin to normal mid-ocean ridge basalts (N-MORB). However, its conspicuous Nb-Ta depletion parallels that of island arc basalts. Depleted Hf-Nd isotopic compositions (ε_Hf(t) = +0.60 to +4.63, ε_Nd(t) = +6.32 to +7.80) in the gabbro, coupled with negligible correlation between ε_Nd(t) and SiO₂ contents imply limited crustal assimilation during magma evolution. Petrological modeling, based on Sm/Yb and La concentrations, suggests the gabbroic melt derived from ~8%–20% spinel lherzolte mantle melting. Analogously depleted Hf-Nd isotopes (ε_Hf(t) = +6.81 to +9.10, ε_Nd(t) = +0.79 to +1.45) in the granite, together with petrographic evidence lacking mafic-ultramafic xenoliths, point to a juvenile lower-crustal source. Integrating the gabbro's N-MORB-like affinity with arc-specific features, regional ultrahigh-temperature metamorphism in southern Chinese Altai, and Permian tectonics, we propose a ridge-subduction regime as the likely petrogenetic setting for the Jiangjunshan magmas. During ridge subduction, upwelling of asthenospheric mantle beneath the ridge induced partial melting of the lithospheric mantle, giving rise to the parental magma of the Jiangjunshan gabbro. This mafic magma underplating subsequently heated the juvenile lower crust, triggering its partial melting and generating the parental magma of the two-mica alkali feldspar granite. Our model indicates that ridge-subduction-related magmatism persisted in the Chinese Altai until the Middle Permian, followed by a tectonic shift from oceanic-continental subduction to intracontinental extension.

Um Solimate emerald deposit is a unique example for the well-known beryl-related schist type. Where, the Be-mineralization is restricted to NNE-trending quartz veins/lenses and as disseminated emerald grains within the altered-metasomatic zones of phlogopite- and graphite-schists. The study of fluid inclusions for the mineralized quartz vein revealed three major groups: (ⅰ) aqueous (H₂O-NaCl), (ⅱ) aqueous-carbonic (H₂O-CO₂-[CH₄]-NaCl), and (ⅲ) aqueous-hydrocarbonic (H₂O-CH₄) FIs. They have been further classified into five types (namely: types 1, 2, 3, 4 and 5) according to number of phases at the room temperature (20 ℃) as well as microthermometric measurements. Based upon the study of fluid inclusions, the initial-ore forming fluid was supposed to be of magmatic nature, characterized by a relatively high temperature of homogenization (T_{h, tot}: 269–485 ℃) and higher salinity (8.4 wt.%–9.6 wt.% NaCl equiv.), followed by development of aqueous-carbonic inclusions at lower temperature (T_{h, tot}: 241–355 ℃) and lower salinity (3.3 wt.%–4.9 wt.% NaCl equiv.) through metamorphic dehydration/decarbonation. Methane-rich FIs were suggested to be formed as a result of local re-equilibration of graphite in reduced environment at the contact aureole of the felsic intrusion. The P-T conditions of ore formation were estimated as modal temperature between (330–370 ℃) and fluid pressures of about 200 MPa, corresponding to an estimated depth ranges from 7 to10 km. The formation of emerald is closely associated with multiple events through the ore evolution, the deposition is ascribed to destabilization process of continuous metasomatic interactions and elemental substitutions between felsic-derived Be-bearing fluids with the adjacent mafic-ultramafic rocks at the zone of mineralization.

The giant Pulang porphyry copper deposit, located in the southern Yidun arc segment of southeastern Tibetan Plateau, represents one of the region's largest mineral systems. This study employs numerical simulation to unravel its metallogenic processes. By integrating field-based geological observations with mineralogical and geochemical data, we developed a coupled model encompassing five key stages of ore formation. The simulation successfully reproduced thermal anomalies and accurately predicted the spatial distribution of mineralization zones at Pulang. Coupling dynamic modeling results with chalcopyrite precipitation rates and average Cu grades enabled quantitative estimation of deposit formation duration (0.99–1.22 Ma). Compared with conventional geochronological approaches, this process-constrained modeling framework provides unprecedented insights into the thermodynamic mechanisms controlling porphyry copper system evolution, offering valuable implications for regional exploration strategies.

Understanding the formation of lithium-rich pegmatites is critical for meeting global lithium demand. The 509 Daobanxi Li pegmatite deposit, located in the West Kunlun orogenic belt of northwestern China, represents a significant example of an LCT-type (Li-Cs-Ta) pegmatite system. This study investigates the paragenetic sequence of lithium (Li) minerals and the factors controlling their crystallization, providing new insights into the magmatic-hydrothermal evolution of rare-element pegmatites. Pegmatite dikes exhibit distinct zonation, comprising a wall rock zone, a border zone (aplitic layer), and a core zone (pegmatitic layer), with Li mineralization concentrated in the pegmatitic and aplitic layers. The primary Li minerals include spodumene (Spd), montebrasite (Mbs), eucryptite (Ecr), elbaite (Elb), and lepidolite (Lpd), which crystallize in the order of spodumene → montebrasite → elbaite → lepidolite. Spodumene, the dominant Li-bearing mineral, crystallizes from a Li-saturated melt during the magmatic stage. Montebrasite, a Li-phosphate mineral, forms in P-rich environments, coexisting with spodumene and columbite-group minerals (CGM). During the magmatic-hydrothermal transition, elbaite crystallizes from a B-rich melt, exhibiting skeletal and patchy zoning due to undercooling and disequilibrium crystallization. Hydrothermal alteration leads to the breakdown of spodumene and the formation of secondary minerals such as eucryptite and lepidolite, with lepidolite being the final Li-bearing phase, enriched in fluorine. The coupled dissolution-precipitation processes during the magmatic-hydrothermal transition play a critical role in the remobilization and enrichment of rare elements such as Li, Nb, Ta, and Sn. This deposit, characterized by spodumene crystallization in the Spd + Quartz stability field (≥300 MPa, ≤725 ℃) and subsequent alteration to Ecr + quartz assemblages (270 ℃, 160 MPa), exhibits broader temperature-pressure conditions exceeding typical global pegmatites like Tanco, with no petalite formation observed due to its persistent exclusion from petalite stability fields throughout mineralization. The shear zone controls the pegmatite emplacement and lithium enrichment in the 509 Daobanxi lithium deposit, and its deformation-fluid coupling mechanism provides new insights for the exploration of LCT pegmatite deposits. The present study highlights the importance of understanding both magmatic and hydrothermal processes in the formation of LCT-type pegmatites and provides valuable insights for the exploration of critical metal resources in similar geological settings.

Water-soluble organic acid anions (WSOAA) in subsurface water have been intensively studied during past several decades. They are used as natural gas precursor, tracer for the movement of underground fluid, indicator for porosity improvement, and detecter of deep subsurface life on the Earth. However, little is known about the distributions and origins of organic acids at deep-ultradeep depth underground. Herein, we collected twenty-nine source rock samples covering a wide maturity range from the Ordos, Qinshui, Junggar, Minhe, and Southern North China basins, as well as six subsurface water samples with depth between 6 544 and 8 396 m from industrial gas producing wells in the Tarim Basin, China. We carried out pyrolysis experiments at various temperatures (250–450 ℃) to investigate the role of water on the generation of organic acids. Results show that there are considerable amounts of WSOAA detected in both high-over mature source rocks and deep-ultradeep subsurface water. WSOAA mainly consists of monocarboxylates, predominately formate and acetate. High-TOC oil-generating source rock has low production rate of organic acids due to lack of hydrogen. Different source rocks have distinct ratios of formate to acetate concentration, expressed as c(formate)/c(acetate), which is due to significant differences in both initial molecular structure and metabolite. This indicates that c(formate)/c(acetate) can be used to distinguish types of organic matters (OMs). Concentrations of WSOAA show a "sharp decrease-slight increase-slow decrease" evolution trend with progressive maturity. Moreover, there are higher production rates of organic acids under hydrous pyrolysis experiments at ≥400 ℃. All geochemical signatures indicate that at both deep-ultradeep depth and high-over mature stages, the formation of organic acids is attributed to the thermochemical oxidation of organic components by mainly hydroxyl radicals, challenging the traditional model of organic acid evolution. This work suggests that petroleum exploration can be extended to great depths in sedimentary basins, when formation temperatures are not exceeding 230 ℃.

The 128.6-m-thick, shale-dominated Klimoli, Wulalike and Lashizhong formations exposed at the Hatuke Creek Section in the Zhuozishan area of Inner Monglia, North China, have been investigated for conodonts. Detailed stratigraphical collections of conodonts preserved on bedding planes from graptolitic shales, supplemented by additional discrete conodonts acid-leached from limestones, enable a refinement of the conodont biostratigraphic scheme at this section. Four successive conodont biozones, ranging in age from mid Darriwilian to late Sandbian (Stage slices Dw2–Sa2), are identified: the Dzikodus tablepointensis Biozone, the Eoplacognathus suecicus Biozone, the Pygodus serra Biozone, and the Pygodus anserinus Biozone, in ascending order. New sub-biozones, based on morphotypes of the biozonal index species, are proposed for the Pygodus serra and Pygodus anserinus biozones, providing alternatives when the traditional sub-biozones are unrecognizable. The biozonation is clearly correlated with the coeval Baltoscandian, South American and South China reference standard successions. The diverse preservation states of conodont bedding plane assemblages suggest that the alteration of conodonts in graptolitic shales represents a diagenetic process, challenging the prevailing hypothesis of pre-diagenetic dissolution. This study highlights the crucial role of previously overlooked conodont bedding plane assemblages in correlating Ordovician slope/basin facies shales, which holds great potential for marine shale gas exploration.

Carbonates present complex pore systems that strongly influence the physical properties and their interrelationships. This study proposes a new approach to establish pore-type mixing-based permeability transforms by integrating well-log and core data. We investigate the influence of pore-structure heterogeneity on permeability and velocity through the rock-frame flexibility factors (γ and γ_µ), derivable using standard sonic and density logs. We derive permeability transforms, with correlation coefficients, R of 0.8 to 0.9, from core measurements and pore-structure variations-dependent physical parameters, namely the porosity exponent (m), Poisson's ratio (σ), velocity deviation log (VDL), and velocity ratio (VR). Through extrapolation using log-data, the m- and VDL-based correlations provide significantly better permeability estimates, with the highest accuracy attained with the m-based correlation, whereas the VR- and σ-based correlations lead to permeability overestimation for high porosities. We plotted log-derived porosity vs. permeability, obtained applying the m-based correlation, to generate consistent porosity-permeability relationships, which account for pore-structure heterogeneity, by sorting the scattering points into distinct groups/trends by considering the variations of pore-structure types and abundance of a specific porosity. For the studied oilfield, three porosity-permeability relationships are identified, with correlation coefficients approaching 0.9, thus validating the approach and supporting its application in petrophysically similar reservoirs.

Fracture-cave reservoirs are widely developed in carbonate formations and account for over 55% of global petroleum reserves. The productivity, formation mechanisms, and in-situ stress states of these reservoirs, characterized by fault-fracture-cave systems, are inherently interconnected. However, solely relying on geometric characterizations of natural fractures and cavities fails to meet the demands of modern petroleum exploration and development, particularly due to their complex structures, significant spatial heterogeneity, and strong geomechanical anisotropy. A critical challenge remains: how to safely and efficiently drill high-yield wells through highly fractured and cavernous zones while mitigating drilling risks. Consequently, establishing geomechanical models for fracture-cave reservoirs and predicting 3D stress fields are imperative for well trajectory optimization and reservoir reconstruction. This study integrates seismic interpretations of strike-slip faults with multi-attribute inversions of fracture-cave reservoirs. Using ANSYS 21.0 software, a homogeneous geomechanical model was constructed based on finely characterized geometries of fracture-cave systems. Rock mechanics parameters, interpreted from conventional logging data and seismic attributes, were inverted to generate 3D distributions. These parameters were subsequently incorporated into the homogeneous model to develop a heterogeneous geomechanical framework. In-situ stress orientations were calibrated using drilling-induced fracture data, enabling predictions of the contemporary stress field in complex fracture-cave reservoirs. The methodology was validated in the Yueman Block of the Tarim Basin's deep carbonate reservoir. Results revealed stress distribution patterns and key controlling factors, which were applied to evaluate wellbore stability, fracture reactivation risks, and optimize well trajectories. This approach provides a technical foundation for safe and efficient exploration-development of fracture-cave reservoirs worldwide.

The Changxing Formation of the Upper Permian in the Sichuan Basin remains a focal area for natural gas exploration. Previous research on this formation has predominantly focused on platform-margin reefs in northeastern Sichuan Basin, while reservoirs within the platform have received limited attention. This study addresses this gap by systematically analyzing bioclastic shoal reservoirs in the Zhongjiang-Moxi region of central Sichuan Basin, using integrated methods including core observations, petrographic analysis, well log interpretation, and 3D seismic data. Results reveal that the study area primarily hosts porous bioclastic limestone reservoirs, characterized by storage spaces dominated by intragranular and interparticle dissolution pores. These reservoirs exhibit distinct facies-controlled attributes. Key controlling factors include: (1) syn- to penecontemporaneous karstification, (2) sea-level fluctuations governing reservoir thickness and stacking patterns, (3) micro-paleogeomorphic variations influencing early exposure dissolution, and (4) dolomitization enhancing reservoir quality. Based on these findings, two depositional evolution models for intraplatform reservoirs of the Changxing Formation are proposed.

Co-seismic landslides are a critical secondary hazard of earthquakes in mountainous regions and are driven by a combination of seismic, geological, and geomorphic properties of both the earthquake source and the affected hill slopes. On Sept. 5, 2022, an M_s 6.8 earthquake hit Luding County, Sichuan Province, China, inducing numerous co-seismic landslides. The epicenter was situated in the Xianshuihe fault zone, one of the most active intracontinental faults in the world. Although the Newmark displacement model is a widely-used and straightforward approach for assessing the hazard of co-seismic landslides, it does not account for other factors such as slope aspect, elevation, slope curvature, distance to rivers, and seismic intensity. To address this limitation, we integrated the Newmark displacement model with the analytical hierarchy process, developing a more comprehensive model for assessing the co-seismic landslide hazard in the Luding Earthquake-hit area, where the terrain and clouds prevent the timely collection of co-seismic landslide data. The proposed model considers the physical mechanisms and seismic, geological, and geomorphic factors underlying landslides, making it a more comprehensive tool for conducting rapid co-seismic landslide hazard assessment. The proposed model is expected to facilitate the reduction of co- seismic landslide disasters and the development of preventative measures in steep and complex mountainous regions.

The reservoir landslide is typically characterized by high-speed movement of a particle-fluid mixture, and its flow and deposit mechanisms are complex. This paper presents the mechanism of submerged granular column collapse under different densities ambient fluids based on coupled computational fluid dynamics and discrete element method (CFD-DEM) analysis. Important fluid-particle interaction forces, such as the drag force and the buoyancy, are considered by exchanging interaction forces between the CFD and DEM computations. We focus on the flow and deposit characteristics of submerged granular column collapse, namely the runout distance, the tail end height, the particle velocity, the energy, and deposit morphology, which are analyzed qualitatively and quantitatively. The change in fluid field caused by submerged granular column collapse and the formation of eddies are also discussed. A relatively dense fluid can significantly hinder the motion of granular flow, but can improve the conversion efficiency of kinetic energy from the vertical to the horizontal direction. Moreover, the eddies caused by fluid turbulence erode the surface of the granular pile, which is especially marked in a high-density fluid. The findings can provide vital theoretical support for the flow and deposit characteristics of granular flow under fluid and offer insights for the study of reservoir landslides.

Altered rock, often encountered in major engineering projects, can seriously affect the stability of rocks and slopes surrounding deeply buried tunnels. This study addressed the alteration mechanism, alteration degree classification, and mechanical parameters of altered rock in engineering project areas using field testing, thin slice identification, X-ray diffraction, and major element testing. Results showed that the altered rock types in the areas of the Pingjiang Pumped Storage Power Station, Hunan Province, and a diversion tunnel in northern Xinjiang Uygur Autonomous Region include biotite granodiorite, biotite monzogranite, and cataclastic granite, and that the main alteration mechanisms are chloritization of biotite and clayization of feldspar minerals. The altered rocks were classified as slightly, moderately, or strongly altered according to their apparent characteristics, rebound value, longitudinal wave velocity, metamorphic mineral content, and porosity. The bulk density, elastic modulus, cohesion, and internal friction angle (Poisson's ratio) of the altered rocks decreased (increased) with increase in the degree of alteration. Numerical simulations showed that in altered rock slope areas, the zone of strong rock alteration and the moderate-strong alteration contact zone exhibit locally large deformations that represent a certain hazard to engineering projects. These results provide valuable guidance and support for major projects in altered rock areas.

Dissolved organic matter (DOM) represents the largest pool of reactive carbon on the Earth and plays a crucial role in various biogeochemical processes and ecosystem functions. However, it is understudied for a global understanding of DOM molecular properties such as molecular weight, stoichiometry, and oxidation state, and the linkages among them across Earth systems. Here, a meta-analysis of 2 707 sites in 204 literatures was conducted by synthesizing four representative molecular properties of DOM, i.e., mass, double bond equivalent (DBE), modified aromaticity index (AI_mod), and nominal oxidation state of carbon (NOSC). By exploring H/C and O/C ratios, we examined the relationships among these DOM properties across waters and land systems, and their geographical patterns and environmental drivers. We found that, compared to land system, the mass, DBE, and AI_mod were all significantly higher in water systems, with river sediments exhibiting the highest values. The DOM oxidation state indicated by NOSC was greater on average in wastewater (NOSC = 0.226 ± 0.06) and marine water (NOSC = 0.133 ± 0.06) than in other habitats. Compared to waters, the mass in land system showed more strongly positive correlations with oxidation states such as NOSC and O/C, and the NOSC showed stronger relations to bioavailability properties such as DBE, AI_mod, and H/C. Among all the properties, H/C and AI_mod contributed to the most variations in global DOM properties. In waters, NOSC monotonically increased towards high latitudes, while DBE and AI_mod showed significant hump-shaped patterns indicating peaked unsaturation and aromaticity at mid-latitudes of approximately absolute 30°–50°. The variations in DOM properties were significantly correlated with environmental factors such as annual mean temperature and pH. Collectively, we revealed the spatial distribution and environmental drivers of DOM molecular properties across Earth ecosystems, which could shed light on our comprehensive understanding of DOM characteristics and its dynamics.

Estimation and attribution of evapotranspiration (ET) and its components under changing environment is still a challenge but is essential for understanding the mechanisms of water and energy transfer for regional water resources management. In this study, an improved hydrological model is developed to estimate evapotranspiration and its components, i.e., evaporation (E) and transpiration (T) by integrated the advantages of hydrological modeling constrained by water balance and the water-carbon close relationships. Results show that the improved hydrological model could captures ET and its components well in the study region. During the past years, annual ET and E increase obviously about 2.40 and 1.42 mm/a, particularly in spring and summer accounting for 90%. T shows less increasement and mainly increases in spring while it decreases in summer. Precipitation is the dominant factor and contributes 74.1% and 90.0% increases of annual ET and E, while the attribution of T changes is more complex by coupling of the positive effects of precipitation, rising temperature and interactive influences, the negative effects of solar diming and elevated CO₂. In the future, ET and its components tend to increase under most of the Shared Socioeconomic Pathways (SSP) scenarios except for T decreases under the very high emissions scenario (SSP5-8.5) based on the projections. From seasonal perspective, the changes of ET and the components are mainly in spring and summer accounting for 75%, while more slight changes are found in autumn and winter. This study highlights the effectiveness of estimating ET and its components by improving hydrological models within water-carbon coupling relationships, and more complex mechanisms of transpiration changes than evapotranspiration and evaporation changes under the interactive effects of climate variability and vegetation dynamics. Besides, decision makers should pay attention to the more increases in the undesirable E than desirable T.

The groundwater (GW) in the floodplain riparian area frequently interacts intensely with surface water (SW). Heat as a tracer is one of the hot research fields in investigating GW-SW interactions, and analytical approaches have been proposed for the calculation of exchange flow velocity. However, few studies have considered the effects of very dynamic flow conditions and monitoring instrumentation on the calculation with field measured data. Herein, taking the middle reaches of the Heihe River as the study area, different types of monitoring wells were constructed under the riverbed and near the river, and multiple methods (Darcy's law, heat tracing, and isotopic mixing methods) were employed to trace the exchanges between the river and groundwater. The results indicate that different methods demonstrate diverse information with obvious unevenly distributed flux along the vertical direction. And the combination of multiple methods has an important role in studying the interaction between GW and SW. Fully screened wells produce intraborehole flow and disturb the heat transport, which is relevant to flow velocity, and further affects the temperature distribution, impacting the temperature-based flow velocity calculation. Dynamic flow conditions aggravate riverbed sediment disturbances, e.g., scour and deposition, and additionally affect the interaction and monitoring data.

Ice cores play an important role in the reconstruction of historical atmospheric information. The glacier of the Tibetan Plateau is influenced by the Indian monsoon and westerly winds, which divide the Tibetan Plateau into monsoon- and westly influenced regions. These atmospheric circulations bring distinct microbial communities to glaciers, with the microbial dispersal process being also influenced by atmospheric factors. However, the potential influence of between bacterial abundance and atmospheric factors is not well known. To reveal potential mechanisms controlling bacterial abundance between two regions, we obtained bacterial abundance and atmospheric records for the past 46 years from two ice cores located within these regions. Statistical regression models were constructed to fit the relationship between bacterial abundance and atmospheric factors. Generalized additive model (GAM) was superior in modeling bacterial abundance compared with linear models and showed that the key factors affecting bacterial abundance were different in the monsoon- and westerly-dominated regions. Specifically, atmospheric dust and black carbon were the key factors for the monsoon-dominated region, and westerly index was the key factor for the westerly-dominated region. The model outputs confirm that atmospheric black carbon plays an important role in affecting bacterial abundance for the glacier located within the monsoon-dominated region, particularly in recent decades. The model also predicted that bacterial abundance will increase by 27% with a doubled black carbon deposition. We quantify and model for the first time that relationship between bacterial abundance and atmospheric black carbon in Tibetan glaciers change over time based on GAM models.

The sediments of crater lakes are one of the ideal archives for high-resolution paleoenvironmental reconstruction. This paper presents sedimentary records of 21 crater lakes in monsoonal China and systematically discusses the geographical distribution and formation ages of these crater lakes. Sediment provenance of the crater lakes and its influencing factors were analyzed, and paleoenvironmental sequences and human activities records on different timescales reconstructed by crater lake sediments in monsoonal China were reviewed. The following points are highlighted: (1) Crater lakes in monsoonal China have been shown to preserve continuous long-time sediments that can exceed even 400 ka, although the chronology of some sediments in the southern part is debated and there were currently fewer long time records from the northern part; (2) the sediment provenance of crater lakes in northern China (e.g., aeolian inputs) was different from that in the south (e.g., the volcanic-lake rim), due to the different location and deposition conditions of crater lakes; (3) crater lake sediments have been used to reconstruct the history of climate changes on different timescales, but reconstruction studies of glacial-interglacial and decadal-annual scale records and studies of spatial comparisons of records on different timescales still need to be strengthened; (4) the anthropogenic signals, which include cultivation, logging, and industrial activity, are well documented in crater lake sediments from different areas and can therefore provide key evidence for the study of the Anthropocene.

A comprehensive understanding of the hydrological cycle is essential for Earth system science and climate change research. The Water Cycle Intensity (WCI) is defined as the sum of precipitation and actual evapotranspiration within a landscape unit. It is a widely used metric to quantify the impact of climate change on the global distribution of water resources. The WCI in the Pamir Plateau, located at the heart of Asian Water Towers, has received little attention. Understanding this aspect is crucial for assessing the impact of climate change on the hydrological cycle and devising strategies to adapt to these changes. Our study assessed the spatiotemporal variation in WCI on the Pamir Plateau from 1980 to 2019 using the WCI framework. Additionally, we explored the teleconnection mechanisms linking the WCI with the Indian Ocean Dipole Mode Index (DMI), canonical El Niño-Southern Oscillation (ENSO), and El Niño Modoki (EMI) using the wavelet analysis method. The findings showed that the WCI of the Pamir Plateau experienced a statistically insignificant increase from 1980 to 2019, particularly after 2003. Spatially, the eastern Pamir Plateau WCI increased significantly, whereas the western region showed a non-significant downward trend. This study found that the WCI in the Pamir Plateau is significantly influenced by atmospheric circulation patterns, and the variation in the WCI in the Pamir Plateau is mainly affected by the canonical ENSO, as well as by the coupling effect of canonical ENSO, and EMI. In addition, based on the characteristics of the regional hydrological cycle, we developed water resource management policies targeting flood risks in the northern Pamir Plateau and drought trends in the southwestern region. These insights not only deepen our understanding of changes in terrestrial hydrological cycles and their underlying mechanisms under climate change but also provide important references for water resource management in the mountainous regions of Central Asia.

The Himalayan-Tibetan Orogen holds numerous glaciers crucial for the Asian Water Tower, thus influencing the surface energy balance and climate feedback. Understanding glacier fluctuations is essential for improving our knowledge of current and future glacial evolution, but limited by short modern glacial observations. Proglacial lakes provide valuable opportunities to obtain high-resolution and continuous glacial changes, but detailed investigations remain scarce. For example, there is still controversy over whether lake sediments reflect melting or ablation. Therefore, we selected a modern glacial lake in the Himalayan region, formed due to glacial retreat in the 1960s, and compared its sedimentary records with modern observations. This provides a case study for future reconstruction of glacial changes using lake sediments. Our results indicate that the sediments of the proglacial lake are primarily influenced by glacial meltwater. Stronger meltwater fluxes transport more debris, magnetic minerals, and terrestrially derived organic matter to the lake. In terms of grain size distribution, the fine silt component (2–8 μm) can serve as an indicator of glacial meltwater intensity. Additionally, this study reveals an opposite trend between glacial meltwater variations and air temperature trends over the past few decades. This suggests that evaporation may offset the increase in glacial meltwater, though the multi-century (> 100-year) trend requires validation with longer records.

Compound extreme climate events may profoundly affect human activity in the Yangtze River Basin. This study analyzed the long-term spatiotemporal distribution characteristics of compound heatwave-drought and heatwave-waterlogging events in the Yangtze River Basin using multi-period historical observation data and future scenario climate model data. It also examined the changes in population exposure to compound extreme climate events in the basin and their driving factors by combining population statistics and forecast data. The results show that the occurrence days of compound heatwave-drought and heatwave-waterlogging events in the Yangtze River Basin have shown a significant upward trend both in historical periods and future scenarios, accompanied by a marked expansion in the affected areas. Compared to historical periods, population exposure in the Yangtze River Basin under future scenarios is expected to increase by 1.5–2 times, primarily concentrated in the key urban areas of the basin. The main factors driving the changes in population exposure are the increased frequency of extreme climate events and population decline in future scenarios. These findings provide scientific evidence for early mitigation of meteorological disasters in the Yangtze River Basin.

The crystallinity has the potential to distinguish the primary and secondary calcite in Chinese loess, which then provides insights into illuviation depth and variations of the East Asian Summer Monsoon. However, this aspect has been rarely investigated. In this study, we defined the crystallinity of calcite as the height/area (H/A) ratio of the diffracted peak at crystal face (1 0 4). The H/A ratio inversely correlates with the average width of the diffracted peak, where a higher H/A ratio indicates higher crystallinity of calcite. Through the mixing and synthetic experiments, we found that the H/A ratio is minimally affected by factors such as calcite content, deposition temperature or rate but significantly influenced by the ionic impurity and the mixing proportion of different calcites. Subsequently, we examined desert samples of loess sources and loess carbonate nodules. Desert samples predominantly consist of primary calcite which inherits characteristics from cryptocrystalline limestone with high levels of ionic impurities resulting in low H/A ratio of 4.30 ± 0.51. In contrast, loess carbonate nodules contain abundant secondary calcite precipitated within soil interstices with low levels of ionic impurities leading to a significantly higher H/A ratio of 7.76 ± 0.82. Consequently, higher H/A ratios during interglacial periods compared to glacial periods are attributed to variations in relative proportions between primary and secondary calcite in loess sequences. The thickness, between the glacial-interglacial boundary and the depth where the H/A ratio starts to increase from the bottom to the top in the loess layer, can be used to indicate the illuviation depth of upper-soil carbonates and the intensity of the East Asian Summer Monsoon. This proxy can be further applied in long-term loess sequences to uncover the summer monsoon evolution.