The East Kunlun Orogen (EKO) is a compound orogenic belt and a Proto-Tethyan tectonic collage. Its constituent blocks document long-term accretionary and collision processes, with episodic, arc-related magmatism and dispersal of several eclogite-hosting units along the orogenic strike. To shed new light on the controversial Early Paleozoic accretion of the EKO to adjoining Gondwana-derived terranes to the south, we present the first investigation of eclogite blocks in banded orthogneisses from the upper Hatu Valley, southern EKO. The Hatu eclogites exhibit varying modal abundances of green amphibole, garnet, omphacite, phengite pseudomorphs, plagioclase, and quartz. Most omphacite and all phengite in the matrix have been replaced by calcic clinopyroxene–plagioclase and biotite–plagioclase symplectites, respectively. The inferred peak assemblage is garnet + omphacite (with 20–28 mol% jadeite) + calcic amphibole + phengite. Pseudosection modeling and conventional thermobarometry reveal a clockwise, four-stage P-T path with peak conditions of 620–700 °C and 14–16 kbar, typical of warm continental subduction. The protoliths of the Hatu eclogites were derived from metasomatized mantle, most likely in a rifted continental-margin setting rather than a mid-ocean ridge environment. Differences in mineralogy, whole-rock geochemistry, and P-T paths during exhumation between the Hatu eclogites and their central EKO equivalents may reflect two distinct tectonic regimes within the Proto-Tethyan subduction system. The concordant, ∼1.10-Ga U–Pb ages of magmatic zircon cores in orthogneisses link the eclogite–gneiss association to the Bayanhar terrane that rifted away from the Gondwana supercontinent. The ∼450-Ma U–Pb ages of high-pressure metamorphic overgrowths on zircon from eclogites and the host granitic gneisses suggest an in situ eclogite origin, supporting the Ordovician collision between the Proto- and Paleo-Tethyan terranes. This is consistent with the first occurrence of A-type granites in the southern EKO at ∼440 Ma, which typically form in post-orogenic extensional settings.
Acid mine drainage (AMD), a serious global environmental problem that degrades water quality, causes severe ecological damage, and poses significant health hazards. In this study, AMD water samples from a high sulphur coalmine area were assessed and evaluated for human health and toxicological risks associated with contamination by potential heavy metals (HMs). The integrated study using correlation, principal component, and cluster analyses indicated that anthropogenic activities such as mining along with natural weathering processes, are the primary sources of HMs in the AMD water. Heavy metal toxicity load (HMTL) indicated significant removal ofheavy metalsfrom AMD mine water and discharge water, achieving compliance with potable water standards. The non-carcinogenic health hazard assessment indicates, adults are more vulnerable compared to children, with both carcinogenic and non-carcinogenic risks potentially present due to exposure to heavy metals. Cytotoxicity and in vitro assays using normal fibroblast L929 cells demonstrated nuclear morphological alterations and elevated intracellular reactive oxygen species (ROS) levels, indicating oxidative stress and cellular damage. The result highlights the urgent need for effective remediation strategies and continuous monitoring of AMD-impacted areas associated with high-sulfur coal mining, to protect both environmental and public health.
Tungsten (W) and tin (Sn) deposits associated with highly fractionated granites are commonly separated in both space and time. Although magmatic differentiation and hydrothermal fluid evolution have long been invoked to explain this decoupling, the coupled chemical behavior of W and Sn in magmatic-hydrothermal systems, and its role in governing the segregation of wolframite and cassiterite, remains poorly constrained. Here, we synthesize whole-rock geochemical data for W-Sn-related granites from major global metallogenic belts and apply t-distributed stochastic neighbor embedding (t-SNE)-based unsupervised machine learning to identify a robust association between iron (Fe) content and barren, Sn-related, and W-related granites. This data-driven pattern suggests that granite-related W-Sn mineralization is fundamentally governed by Fe abundance. We further use total Fe content as an input to a Rayleigh distillation model simulating Fe behavior in the multiphase equilibrium system FeWO4–SnO2–NaCl–HCl–H2O–CO2. Our results show that, in addition to Fe availability, the thermodynamic properties of W and Sn exert a first-order control on the decoupling of wolframite and cassiterite during hydrothermal mineralization. At 200–300 °C, wolframite precipitation is favored, whereas cassiterite predominates at 340–400 °C. Low-Fe conditions (0.080–0.214 mol/kg) promote wolframite as the dominant phase but are insufficient for economically significant cassiterite formation. In contrast, higher Fe contents (0.226–0.420 mol/kg) substantially enhance cassiterite precipitation relative to wolframite, facilitating W-Sn co-enrichment. Economically significant cassiterite-dominated deposits require both elevated Fe contents (0.226–0.420 mol/kg) and higher initial Sn concentrations (W = 0.013 mol/kg, Sn = 0.020 mol/kg). Pressure exerts contrasting effects on W and Sn solubility: W solubility increases with pressure, whereas Sn solubility decreases with pressure below 300 °C, producing asynchronous responses that amplify their differential precipitation. CO2 modifies mineral solubility by regulating fluid pH; increased CO2 enhances the solubility of both wolframite and cassiterite, with the magnitude of this effect depending on the initial pH of the hydrothermal fluid. Oxygen fugacity (fO2) controls mineral solubility through its influence on the Fe3+/Fe2+ ratio: increasing fO2 lowers cassiterite solubility, whereas wolframite remains comparatively insensitive. Across all modeled conditions, Fe variations have a greater effect on wolframite solubility than on cassiterite. Collectively, these results clarify the geochemical controls on W-Sn mineralization and establish Fe as a key parameter governing the formation and decoupling of wolframite- and cassiterite-bearing systems in highly evolved granitic environments.
The role of post-diagenetic hydrothermal processes in cobalt (Co) enrichment in sediment-hosted stratiform Cu-Co (SSC) deposits remains controversial, particularly regarding whether high-grade Co mineralization is primarily diagenetic or requires later tectonic overprinting. The Shizishan deposit, SW China, exhibits a well-defined vertical Co zoning and coexisting disseminated and veinlet sulfide assemblages, making it an ideal example to address this issue. Here we integrate in-situ sulfide trace element geochemistry, Fe–S isotopes, and rutile U–Pb dating to distinguish two mineralization events. Early disseminated chalcopyrite, cobaltite, and pyrite formed during diagenesis, with Co distribution controlled by organic matter in the host rocks. The later post-diagenetic stage formed veinlet chalcopyrite, bornite, cobaltite and cobaltian pyrite cross-cutting early-stage mineralization. Veinlet chalcopyrite shows systematic depletion of Co, Ni and As relative to disseminated chalcopyrite, while cobaltite and pyrite show opposite trends, indicating remobilization and recrystallization of pre-existing sulfides. Chalcopyrite from Co-rich layers exhibits lower δ56Fe values (−0.53‰ to −0.17‰) than Co-depleted layers (−0.31‰ to −0.02‰), suggesting more reduced fluids. Hydrothermal rutile associated with veinlet ores yields a U–Pb lower intercept age of 1449 ± 33 Ma, defining a post-diagenetic tectonic-hydrothermal event. This overprinting event significantly upgraded Co grades, particularly in dolostone enriched in organic matter. Our results demonstrate that while the diagenetic stage provided primary metals and traps, it is the later orogenic-related hydrothermal modification that was essential for the formation of economic Co concentrations, and a reduced setting is a key factor controlling Co precipitation.
At the scale of the European peri–Tethyan basins, the Paris Basin is one of the largest intracratonic sedimentary repositories within the collapsing post-Variscan continental crust. However, the limited availability of petrochronological constraints on its late Carboniferous detritus has hindered the development of an accurate model for the timing and tectonic evolution of the Paris Basin’s early subsidence stages. We present a new set of U–Pb ages and trace-element data for ∼1000 detrital zircons and apatites from four late Carboniferous and early Permian sedimentary units collected in two sub–basins of the Saxo–Thuringian and Armorican zones of the Paris Basin. The new U–Pb and geochemical datasets provide evidence for the diachronous nature of subsidence throughout the base of the Paris Basin from ∼320–315 Ma in the Saint–Die sub–basin (Saxo–Thuringia Zone), to ∼300 Ma in the Brecy sub–basin (central Armorican Zone / Moldanubian Zone). The detritus of the Saint–Die sub–basin yields petrochronological signals typical of the Saxo–Thuringian zone and shows a stable provenance record through the late Carboniferous and early Permian. By contrast, the detritus of the Brecy sub–basin shows an up–sequence increase in complexity. The early Permian sandstone of the Brecy basin yields evidence of a large influx of high– and low–grade metamorphic grains, together with a mixed mafic–felsic igneous detritus, which is consistent with a large–scale unroofing and reworking of the northern Armorican and Central French Massif at ∼310–300 Ma, and seems to correspond to the petrochronological record of the collapse of the Variscan belt. Hence, we argue that the previously postulated intracratonic nature of the Paris Basin does not fully describe the tectonic events that led to its formation. In this contribution we have observed that a geological model describing the onset of the Paris Basin as controlled by late Carboniferous Variscan lithospheric instability in French Variscides is in broader agreement with the new petrochronological data.
The subduction–collision tectonic setting of the Tibetan Plateau (TP) favors the formation of boron (B) deposits in salt lakes. Da Qaidam Salt Lake (DQL) in the northern TP is well known for giant brine–solid B resources. However, massive boron accumulation in the DQL cannot be balanced by the modern surface recharge system, and large boron isotopic offset (∼28 ‰) between source waters and brines indicates complex boron source–sink processes, which remain poorly constrained. Here, we present hydrochemical parameters, B concentrations and isotopes of river waters, groundwaters, geothermal springs, lake brines and intercrystalline brines from the DQL. The recharge waters are characterized by high B concentrations (0.1–44.8 mg/L) and large B isotopic variations (−11.94 ‰ to +16.46 ‰). Similarly, brines in the DQL also present varying B concentrations (234.1–1847.5 mg/L) and isotopes (−6.05 ‰ to +10.10 ‰). By integrating these results with previous studies on regional tectonic evolution, watershed geomorphology, hydrological reorganization and salt-forming periods in the DQL, the source–sink process and enrichment mechanisms of B in the DQL are discussed. Key conclusions are as follows. Besides the supply of hot springs and rivers in the modern drainage area, neighboring Tataleng and Yuka rivers provide ample B to match the giant resources in the DQL through cross–basin groundwater flow regimes. The high B concentrations of rivers in the DQL are from weathering of boron-rich bedrock, recharge of hot springs and mud volcanoes, and leaching of early small intermontane B deposits and sediments. The subduction–collision tectonic setting in the northern Qaidam Basin facilitates the formation of various B-rich rocks and fluids surrounding the DQL. Various B sources and transportation–enrichment processes promote B isotopic discrepancy in recharge waters and lake brines. Furthermore, diversion of the Yuka and Tataleng rivers since ∼23 ka has sharply decreased water budget of the DQL, inducing rapid salt deposition and B enrichment under arid climate. Conclusively, the formation of large B deposits in the DQL is the collaboration of endogenic and supergene processes. The research findings in this study offer insights for understanding the formation of numerous B deposits in salt lakes on the TP.
Due to increasing habitat fragmentation and persistent land-cover dynamics, assessing resilience in coastal vegetation ecosystems poses substantial challenges. To address these issues, this study quantifies the spatiotemporal dynamics and driving mechanisms of vegetation carbon storage to evaluate ecosystem resilience in complex coastal habitats. By integrating long-term Landsat time-series data on the Google Earth Engine (GEE) platform with the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, we developed an integrated framework for assessing coastal vegetation resilience. Taking the coastal zone of Jiangsu Province as the study area, the results indicate the following: (1) By integrating critical factors such as phenological variability, tidal inundation, and land–water interactions, the proposed model significantly improves the accuracy of vegetation information extraction and the reliability of long-term carbon storage monitoring in complex coastal environments; (2) From 1985 to 2024, the total vegetation carbon storage in Jiangsu Province exhibited a fluctuating upward trend, rising from 1258.08 Tg to 1514.41 Tg, marking a net gain of 256.33 Tg (20.38 %). This suggests that coastal vegetation maintains robust long-term carbon sequestration capacity amid cultivated land dominance and enhanced forest carbon sinks; (3) Spatially, the evolution of vegetation carbon storage revealed a distinct pattern of “North–South differentiation and Land–Sea coupling.” Specifically, the northern plains and coastal zones showed continuous growth and steadily strengthened carbon sink functions, whereas the highly urbanized southern region experienced greater constraints and more pronounced fluctuations. Resilience assessments indicated stronger recovery elasticity and maintenance capacity in the north, relatively weaker resilience and higher sensitivity to disturbances in the south, and a transitional coastal type characterized by high recovery potential but weak stability; (4) The provincial-scale increase in vegetation carbon storage was primarily driven by the structural upgrading of vegetation coverage classes. Specifically, the significant expansion of dense-cover vegetation, replacing high-cover classes, elevated carbon density per unit area, resulting in cumulative carbon growth despite a slight contraction in total vegetation area. These findings provide a scientific basis for assessing vegetation ecosystem resilience, optimizing carbon-sink enhancement pathways, and implementing targeted ecological management strategies.
The Xiarihamu Ni-Co sulfide deposit in northern Tibet is the world’s largest orogen-related magmatic sulfide system. Sulfide mineralization is hosted in two spatially juxtaposed but geochemically distinct units (orthopyroxenite and harzburgite), implying contrasting magmatic and ore-forming processes, yet their relationship and detailed magma evolution history in controlling deposit formation remain debated. This study integrates new field observations with zoned orthopyroxene geochemistry, O-Sr-Nd isotopes, and numerical modeling to assess the roles of magma recharge and magma-crust interaction in deposit genesis. Isotopic mixing calculations indicate that both units were derived from a mantle source metasomatized by sediment melts and slab fluids. A sharp contact between two units demonstrates that they originated from discrete magmatic pulses. The parental magma of the pyroxenite assimilated ∼ 10% siliceous crustal material, whereas harzburgite experienced limited contamination, accounting for their isotopic differences. Orthopyroxene oscillatory zoning in Cr-Ca-Fe and δ18O variations record magma recharges, with a critical recharge of primitive influx introducing abundant Ni and Co into shallow magma chamber. Numerical modeling demonstrates that sulfide saturation in both units was triggered by selective assimilation of external sulfur from Precambrian metamorphic basement. Variable magma/sulfide mass ratios explain both the shift of sulfur isotope toward mantle values and the contrasting Ni enrichment in the two units. We propose a refined two-stage sulfide mineralization model for the Xiarihamu deposit, in which distinct magma pulses with independent sulfide saturation and enrichment histories operated within a dynamic conduit system. This model provides new insights into the genesis of orogenic magmatic sulfide systems and exploration targets.
The study explores the Ghaggar-Saraswati-Drishadvati river basin, located between the Sutlej and Yamuna rivers in the Punjab-Haryana plains, a region renowned for its rich archaeological legacy. Here, attempt has been made to examine how tectonic, geomorphological, and hydrological factors shape the evolution of the ancient river system once occupying the study area. This basin has witnessed significant hydrological and geomorphological shifts over the millennia. Ancient Indian scriptures such as the Vedas and Mahabharata refer to the Saraswati River, but its direct textual documentation with the Sutlej or Yamuna is lacking. The research delineates paleochannels and traces the ancient river systems that display complex interplay of tectonic, hydrological, and historical factors shaping the river systems of Northwest India. So, tectonics dominate on multi‑millennial timescales, hydrology/climate (monsoon strength and glacial melt) dominate on millennial timescales, and historical impacts dominate on decadal–centennial timescales. While many rivers in the basin are now seasonal, sedimentological analyses and satellite imagery suggest paleochannels like the Ghaggar-Hakra represent former courses of the Sutlej River linking Himalayan glaciers with the Saraswati system. These findings offer valuable insights into the region’s hydrological evolution and archaeological significance.Thermoluminescence (TL) dating and bore-hole data have revealed evidence of a substantial paleo-channel, approximately 1.5 km wide and over 40–50 m deep, with sediment ages estimated at 5.3 ± 0.6 ka. But the modern Sutlej channel in the region seldom exceeds 150 m width. These findings align with the fluvial chronology of the Sutlej-Ghaghar-Saraswati- Drishadvati system, suggesting the existence of a significant perennial river during the mid-Holocene, likely connected Northwest India to the Yamuna River near present-day Delhi. The large paleo-channel identified near Nigambodh Ghat, Delhi corresponds to the ancient eastward flow of the Ghaggar or Sutlej paleochannel, underscoring its historical hydrological significance.
Titanite-filled microtubular structures associated with carbonaceous material occur within stromatolites of the 2.72 Ga Tumbiana Formation, Pilbara Craton. Petrographic, crystallographic, nanoscale structural and compositional characterization, and geochemical analyses suggest a genetic relationship between microtubular structures, organic matter, Ti enrichment, and titanite mineralization. These microtubular structures are interpreted as mineralized ambient inclusion trails formed through localized dissolution associated with carbonaceous material and pyrite during burial rather than microbial tunnels or dendritic titanite growth. Elemental mapping using TEM and Atom Probe shows that Ti enrichment is spatially associated with carbon-rich stromatolitic laminae, and nanoscale TiO2 (anatase) particles occur within titanite-bearing domains, suggesting localized Ti concentration within organic-rich microenvironments, potentially mediated by microbial biomass and extracellular polymeric substances. Titanite likely formed during burial and low-grade metamorphism through reactions potentially involving TiO2, quartz, calcite, and methane-bearing fluids, preserving microtubular textures and associated carbonaceous material. These results indicate that Ti-bearing mineral phases associated with stromatolitic environments may represent previously underrecognized archives of microbe–mineral interactions in Archean rocks. The occurrence of TiO2 nanoparticles within organic-rich stromatolitic domains indicates localized Ti concentration prior to titanite formation and raises the possibility that the UV-absorbing properties of TiO2 may have been relevant in Archean surface environments subjected to intense ultraviolet radiation.
The Eastern Ghats Belt (India) is centrally located within a string of multi-continent Cambrian peri-orogens formed during the terminal assembly of East Gondwanaland. However, the timing of the accretion, Tonian versus early Cambrian, between the Eastern Ghats Belt and the Indian landmass remains contentious. We address the issue by combining field geology/microstructures, whole-rock geochemistry and U-Pb-Hf (zircon) isotope systematics in the Western Charnockite Zone (WCZ), which is wedged between the Eastern Ghats Province (EGP) to the east and the Bastar Craton to the west. The WCZ crustal domain, comprising differentiated syn-collisional magmatic charnockites, was derived by partial melting of 3.76‒3.66 Ga mafic precursors. The WCZ emplaced at ∼ 2.61 Ga and deformed at granulite-facies conditions at ∼ 2.53 Ga, later experienced amphibolite-facies syn-shearing metamorphism at ∼ 2.47 Ga.In the EGP, multiply deformed high-Mg-Al granulites, characterised by high-T metamorphism at ∼ 2.53 Ga and ∼ 0.93 Ga, were intruded by ∼ 0.93 Ga blastoporphyritic granitoids; however, Cambrian dates are lacking. However, adjacent to the WCZ, the EGP blastoporphyritic granitoids were deformed at high-T conditions (∼0.5 Ga). In contact with EGP, ∼2.45 Ga cratonic granitoids intrusive into 3.51‒3.45 Ga basement gneisses exhibit ∼ 0.5 Ga syn-shearing anatexis.The ∼ 2.6 Ga WCZ, derived from Meso/Eoarchean protoliths, led to eastward growth of the Bastar Craton. The Tonian-aged EGP accreted with the Archean WCZ/Bastar Craton composite along a ∼ 0.5 Ga accretion zone characterized by prograde high-T metamorphism manifested by hornblende decomposition to two-pyroxene + plagioclase symplectites. The accretion of the WCZ/Bastar Craton with the EGP, in relation to the Indo-Antarctic Cambrian accretion, occurred as part of the global-scale terminal assembly of Gondwanaland.
The southern East Kunlun Orogen (EKO) along the northern Tibet superimposed two periods of tectonics linked to the Proto-Tethys and Paleo-Tethys oceans, respectively. However, the tectonic process of the Proto-Tethys Ocean along the southern EKO during the Silurian period remains highly controversial, with two competing viewpoints of closure versus ongoing subduction advocated. Here, the petrogenesis of S-type granites and metamorphism of the migmatized paragneiss within the Kuhai Complex in the accretionary belt of southern EKO were first investigated using in-situ zircon and monazite geochronology, whole-rock and mineral chemistry, thermobarometry, and phase equilibria modelling to address this controversy. The obtained ages indicate that formation of S-type granites and metamorphism of migmatized paragneiss occurred coevally, during the Silurian period (440–430 Ma). Two types of S-type granites with distinct geochemical characteristics were identified, and they were derived by dehydration and H2O-fluxed melting of paragneiss of the Kuhai Complex, respectively. The migmatized paragneiss recorded near-peak pressure–temperature (P-T) conditions of ∼6.0 kbar and ∼685 °C, corresponding to an apparent geothermal gradient of 35 ℃/km, which indicates a thermal anomaly in the accretionary belt of southern EKO during the Silurian. Also, this geothermal gradient is in significant contrast with low thermobaric (T/P) ratio metamorphism documented by the Silurian continental eclogites exposed to the north, which are indicative of collision orogeny after closure of the northern branch of the Proto-Tethys Ocean. Given such a high thermal regime, along with a pulse of the Silurian adakitic magmas derived from the subducted oceanic slab, the Proto-Tethys Ocean in the southern EKO remained open and actively subducted during the Silurian. We tentatively propose a new model of local slab tearing underneath the accretionary belt of the southern EKO to interpret coupled occurrence of Silurian high-T/P ratio metamorphism and adakitic magmatism. This new finding provides a new insight into the Silurian paleogeographic position of East Asian continents (i.e., North China, Tarim, and Qaidam). By integrating our new results, paleomagnetic and biogeographic evidence, North China, Tarim, and Qaidam were isolated from East Gondwana by an open Proto-Tethys Ocean branch by the Silurian.
Earthquake vulnerability assessment of buildings within geographical information systems (GIS) remains a complex and fragmented process, often requiring the integration of multiple analytical methods and heavy reliance on expert interpretation. Despite advances in geospatial technologies, existing workflows for vulnerability assessment and reporting are still labor-intensive, loosely connected, and difficult to automate. Recent developments in Artificial Intelligence (AI), particularly large language models (LLMs) such as Chat Generative Pre-trained Transformer (GPT) and generative frameworks like AutoGPT, offer new opportunities to streamline and automate complex geospatial processes through semantic reasoning and adaptive task execution. The objective of this work is to introduce a framework and implementation of the Geospatial Infrastructure Management Ecosystem (GeoIME), powered by the geospatial GPT. The proposed GeoIME-GPT approach integrates AI-driven reasoning with GIS-based analysis to assist building inspectors and decision-makers in automating map generation, performing vulnerability and risk assessments, and generating rehabilitation recommendations in accordance with Federal Emergency Management Agency (FEMA) 154 guidelines and geospatial data analytics. Among these, an incorporated LLM understands natural language questions, breaks them down into geospatial subtasks, and eventually calls the necessary GeoIME tools for spatial analysis and building evaluation in sequence. The framework ’learns’ as it progresses and, depending on the context, becomes more or less precise, leading to an intuitive language-based interaction with geospatial data. From an evaluation of 87 buildings through field observations, structural data extraction, and GIS-based risk mapping, together with 50 geospatial task queries, more efficient, accurate, and interpretable assistance for building inspectors was demonstrated compared to Rapid Visual Screening (RVS). By employing two LLMs (GPT-4 (80%) and GPT-5 (94%), the system achieves high accuracy, and by optimizing spatially, a further increase in analysis accuracy (+12%) is obtained. Despite some data privacy and algorithm optimization issues, these results demonstrate GeoIME-GPT’s promising capability in automated seismic risk estimation and building vulnerability assessment, in accordance with FEMA-154 (i.e., Building Seismic Safety Council) standards, as well as for sustainable buildings.
Retrogressive thaw slumps (RTS) are a thermokarst landform increasingly found on the Qinghai–Tibet Plateau, characterized by progressive headwall retreat and exceptional sensitivity to thermal change. However, static assessments fail to spatially interpret their driving mechanisms. This study examines current and future susceptibility and shifts in driving factors. A multi-model ensemble with area under the receiver operating characteristic curve values above 0.96 was developed from an inventory of 3693 RTSs, and Shapley additive explanations together with GeoShapley were used to attribute model predictions to environmental drivers and their spatially varying effects. The models indicate that by mid-century (2041–2060), the high-susceptibility area will increase from 5.76% to 10.80% to 6.01%–9.76% under SSP1-2.6, 8.01%–11.64% under SSP3-7.0, and 8.41%–10.34% under SSP5-8.5, with the northeastern plateau a primary zone of heightened risk. According to the GeoShapley framework, thawing degree days will increase in influence along the southeastern margins, freezing degree days will intensify their stabilizing effect in the northwest, and the influence of precipitation will stabilize or decrease across most of the plateau. These findings provide mechanistic insights and support targeted risk management strategies.
Soil moisture regulates land–atmosphere coupling, agricultural productivity, hydrological processes, and ecosystem functions; however, accurately estimating it over heterogeneous semi-arid regions remains challenging. Here, we present a multi-sensor approach that integrates radar backscatter from Sentinel-1 and Sentinel-2, optical reflectance from Landsat-8, and ancillary products from the Soil Moisture Active Passive (SMAP) mission to estimate surface soil moisture. The analysis focuses on the Thamirabarani river basin for the period 2015–2025, and SMAP products were used as the independent reference data for evaluation. A multiple linear regression formulation yields robust performance, with a Nash-Sutcliffe efficiency of 0.78, a root-mean-square error of 0.040 m3/m3, and a mean absolute error of 0.032 m3/m3. Overall, accuracy decreases during the pre-monsoon period and improves in the post-monsoon season because increased precipitation raises soil moisture and alters vegetation structure. High soil moisture (0.41–0.48 m3/m3) was primarily found in the basin’s northeastern and western regions, where dense forest cover enhances water retention. Sensitivity diagnostics indicate that radar-vegetation interaction and preceding precipitation account for most of the variability in the retrieval. Comparative evaluation against alternative machine learning algorithms yields similar predictive accuracy while preserving physical interpretability. Uncertainty mainly arises from SMAP products and from spatial-scale discrepancies between coarse satellite grids and sub-grid heterogeneity. The present results demonstrate that an interpretable, multi-sensor integration approach can resolve regional-scale soil moisture dynamics in semi-arid environments and support land and water resource management in areas with sparse in situ observations.
The redox state of the Archean mantle was a critical control on early Earth’s degassing and atmospheric oxygen evolution. Yet, the timing, extent, and mechanisms of its oxidation remain poorly constrained. To address this, we investigated the oxygen fugacity (fO2) of 2.58–2.49 Ga metamorphosed mafic rocks from the Zanhuang Complex, North China Craton. These rocks exhibit geochemical and isotopic signatures (whole-rock and zircon) indicative of late Neoarchean metasomatism by fluids/melts derived from 2.7 Ga and 2.9 Ga oceanic/continental crust. Mantle source fO2, calculated from primitive samples using V-Sc and V-Ti systems, averages ΔFMQ −0.88 ± 0.48—significantly more oxidized than the middle Neoarchean upper mantle (ΔFMQ −2.14 ± 0.09). This oxidation is attributed to a hydrous melt generated by eclogite-facies metamorphosed subducted oceanic crust and overlying terrigenous sediments. Key evidence includes positive correlations between ΔFMQ and fluid-mobile indices (LOI and Ba/La), and negative correlations between zircon εHf(t) and ΔFMQ and between whole-rock V/Sc and εNd(t), which point to source enrichment. The oxidation process was facilitated by residual, ferrous iron-rich garnet in the source, as indicated by the positive correlation between ΔFMQ and δ56Fe, as well as between ΔFMQ and the Dy/Yb ratio in whole-rock and zircon analyses. Phase equilibrium modeling of a hybrid source (80% MORB and 20% late Archean metapelite) at 700–850 °C and 12–16 kbar predicts ∼30 wt.% melt yielded with, ∼15 wt.% H2O, ΔFMQ of ∼−0.3, and Dy/Yb of ∼2.0. These properties closely match those inferred for the metasomatizing agent. Thus, late Neoarchean subduction and melting of oceanic crust coupled with sedimentary material not only oxidized the mantle wedge but also likely contributed to the environmental preconditioning for the Great Oxidation Event in the early Paleoproterozoic.
The periodic characteristics of seismic activity and their modulation mechanisms are fundamental to understanding stress accumulation and release within tectonic plates and regional tectonic evolution. In this study, singularity analysis and wavelet analysis are jointly applied to systematically characterize the periodic features of earthquake frequency and mean energy along the two subduction zones flanking the Sunda Plate—the eastward Philippine Sea Plate–Sunda Plate subduction zone and the westward Indo–Australian Plate–Sunda Plate subduction zone. The results indicate that earthquake frequency in the eastern subduction zone exhibits two primary periodicities of ∼ 5 years and ∼ 8 years, whereas the western subduction zone predominantly exhibits a periodicity of ∼ 8 years. In contrast, energy variations in both subduction systems display low-frequency oscillatory behavior within the 3–5 years band. Further analysis indicates that the ∼ 8-year periodicity may be statistically associated with potential long-period external modulations, whereas the ∼ 5-year periodicity is more likely associated with localized interplate interactions. Overall, this study provides a quantitative analytical framework for understanding earthquake periodicity under plate-dynamical control and the coupling relationships between adjacent subduction systems, and it offers new insights into the evolutionary characteristics of regional seismic activity.
Subduction initiation (SI) remains one of the most fundamental unresolved problems in solid Earth geodynamics. Building on the hypothesis of Niu et al. (2003) that SI requires lateral compositional buoyancy contrasts within the lithosphere, we develop here the first fully quantitative C3–SI (Compositional-Contrast-Controlled Subduction Initiation) framework based on transparent Newtonian mechanics. The framework integrates two components: (1) the Subduction Initiation Index (SII), which quantifies lithospheric rupture driven by compositional buoyancy contrast, and (2) the Fault-Block Sequential Sinking (FBSS) mechanism, which explains the transition from rupture to self-sustaining subduction. We show that ocean-continental (O–C) and ocean-oceanic plateau (O–P) boundaries generate lateral horizontal buoyancy compressive stresses (σO-C ∼ 120 MPa andσO-P ∼ 60 MPa, respectively), far exceeding ridge push (σRP≈ 22 MPa). This stress-equivalent term represents the horizontal compressive stress generated by the lateral gravitational potential energy (GPE) gradient, analogous to ridge push. These stresses are strongly localized within ∼50 km of the boundary and decay rapidly toward plate interiors, explaining why SI is spatially restricted. The SII successfully predicts where rupture occurs, but rupture alone cannot produce subduction. Lithosphere-scale bending is mechanically implausible because required stresses (∼1–3 GPa) exceed available tectonic stresses by an order of magnitude. The FBSS resolves this by treating the oceanic lithosphere as a fault-segmented system, where inherited abyssal-hill faults enable sequential block sinking. As a 100-km-wide slab segment sinks to ∼50–60 km into the asthenosphere, slab-pull reaches a threshold of ∼3 × 1018 N, driving acceleration to >50 mm/yr and enabling self-sustaining subduction. The predicted spatial localization, force balance, and timescales (1–3 Myr) are consistent with global observations. The C3–SI framework provides the first fully Newtonian and transparent mechanical description of SI, resolving the long-standing problem of how lithospheric rupture occurs and how rupture evolves into subduction, without invoking ad hoc weakening mechanisms in opaque numerical models.A global survey of ∼30 subduction zones (50 segments) confirms that most SI events occur at O–C or O–P boundaries. Even the so-called intra-oceanic systems (e.g., Mariana and Tonga) are underlain by compositionally highly depleted, physically buoyant forearc lithospheric mantle, consistent with the original hypothesis of Niu et al. (2003).
High-precision flood susceptibility mapping is crucial for regional disaster risk management and sustainable development. However, data-driven machine learning models are heavily constrained by the scarcity and high acquisition costs of high-quality training samples in data-scarce regions. To address this challenge, in this study, a novel coupled framework combining a knowledge-driven method (analytic hierarchy process) with data-driven machine learning algorithms was developed to generate reliable training samples and achieve high-precision flood susceptibility assessment. This framework was applied and validated in Dingyuan County, Anhui Province. The results indicated that all four coupled models demonstrated excellent performance when trained on both the training and validation sets, with accuracies and AUCs exceeding 89.64% and 0.965, respectively, for the former and exceeding 89.17% and 0.963, respectively, for the latter. Among these models, the AHP–RF model performed the best on the training set, whereas the AHP–LR model performed the best on the validation set. The four flood susceptibility maps produced in this study were consistent: areas with higher flood risk were concentrated across numerous regions in the southern, central, eastern, and western parts, particularly along riverbanks and in areas receiving higher rainfall. SHAP analysis indicated that the slope was the most significant factor across all four models. This study provides a novel approach for regional flood susceptibility mapping, addressing the challenges associated with scarcity of training data in certain areas while improving the reliability and applicability of spatial flood susceptibility predictions.
Despite the global urgency to decouple economic growth from energy intensity, the interactive role of regulatory frameworks and technological progress in energy efficiency transitions remains inadequately understood. Hence, this study investigates the standalone and synergistic impacts of environmental taxation (ET) and environmentally related technology innovation (ERTI) on energy intensity (EI) across 20 OECD countries from 1995 to 2021. Utilizing a robust Method of Moments Quantile Regression (MMQR) framework with fixed effects, we transcend mean-based estimations to address distributional heterogeneity across various energy intensity quantiles. Our empirical findings unveil a significant joint effect: while environmental taxation and eco-innovation independently curb energy intensity, their interaction serves as a significant moderating catalyst. Specifically, fiscal instruments enhance the capacity of green technologies to lower energy intensity, with the most pronounced effects observed in higher quantiles. These results suggest that market-based instruments are not merely revenue-generating tools but are conducive to guiding sustainable technological development toward global energy efficiency goals. By providing a strategic roadmap for policy integration, this research offers critical insights for navigating the complex socio-technical dynamics of energy transitions within planetary boundaries.
