Significant advances have been made in geological reconstructions of circum-continental subduction zones and classification of continents. However, how continental area and subduction geometry jointly influence mantle convection remains largely unexplored. Here, we conducted spherical-shell numerical models with an idealized single-continent configuration to investigate how continental area, circum-continental subduction geometry (full- versus half-circular), and convective vigor control mantle convection wavelengths and subcontinental upwelling structures. The results demonstrate that as continental area increases, the dominant global convective wavelength transitions from a short-wavelength regime to a long-wavelength spherical harmonic degree‑1 pattern when the continental area reaches 8.5% or 10% of Earth's surface, depending on the full-circular or half-circular subduction geometry, respectively. These continental sizes are also critical for controlling the regional subcontinental mantle flows. Such sizes can begin to prevent surrounding subducting slabs from covering the subcontinental core–mantle boundary, thereby creating space in the underlying mantle for the growth of slim upwellings. When continental area further exceeds ~20%, the dominant convective wavelength starts shifting from degree-1 to degree-2 and stabilizes in a degree-2 pattern, indicating that a minimum supercontinent area of ~20% is required to reorganize global mantle convection. The whole mantle becomes degree-2 dominated when the continental size reaches ~30% of Earth’s surface. In addition, increasing Rayleigh number or internal heating promotes the transition from degree-1 to degree-2 convection. Compositionally anomalous dense (CAD) material at the core–mantle boundary has little influence on the dominant convective wavelength but strongly affects the location of mantle plume formation.
This study investigates the depth-dependent geodynamic architecture of Türkiye by applying spectral decomposition to the Virtual Deformation (VD) analysis of the gravity field. Using a high-resolution global geopotential model, we employed the Radially Averaged Power Spectrum (RAPS) to deconvolve the gravity signal into five discrete spectral bands representing key lithospheric interfaces: the Asthenosphere–Upper Mantle (n = 0–66), Lithosphere-Asthenosphere Boundary (n = 66–230), Regional Moho (n = 230–481), Crystalline Basement (n = 481–1274), and Near-Surface (n = 1274–2190). The resulting depth-slices reveal that the North Anatolian Fault Zone possesses a profound lithospheric root, appearing as a coherent ductile shear zone at the LAB that transitions into a fragmented brittle fault system in the upper crust. In the Western Anatolian Extensional Province, the analysis captures a vertically continuous zone of virtual dilatation, imaging the deep asthenospheric conduit associated with a Subduction-Transform Edge Propagator (STEP) fault. Beneath Central Anatolia, a distinctive "sandwich" architecture of extension bounded by compression provides gravimetric evidence for lithospheric delamination, while the adjacent Eastern Anatolia region exhibits a vertical polarity reversal—from deep compression to shallow dilatation—characteristic of active mantle dripping and slab detachment. Further analysis distinguishes the mechanically decoupled "rigid lid" of the Arabian Platform from the complex crustal imbrication along the Bitlis-Zagros Suture and the intact subducting slab beneath Cyprus, resolves the asymmetric crustal thinning of the Sea of Marmara, and defines the Dead Sea Transform Fault as a profound rheological boundary separating distinct lithospheric blocks.
The study presents an integrated assessment of depleted hydrocarbon reservoirs in an offshore field, Niger Delta Basin, to evaluate their suitability for long-term CO2 storage. Using wireline logs, production datasets, and 3D seismic data, interpreted with Petrel™, Techlog™, and CMG simulation platforms, the research used a process-based workflow to combine petrophysical characteristics, structural and stratigraphic frameworks, and geomechanical attributes to develop property and CO2 injection models. Stratigraphic interpretation reveals two high-quality sandstone reservoirs enclosed between a 29 m thick shale overburden and a 126 m shale underburden, forming a syn-depositional anticline influenced by mobile shale diapirism. Five major north–south trending faults were mapped, comprising normal and reverse faults that define horst–graben geometries and fault-dependent closures. The mapped structural closures are not intersected by major faults, and a competent, ductile marine shale caprock provides effective vertical containment. Petrophysical evaluation shows good to excellent reservoir quality across most of the field, with heterogeneity concentrated in the isolated northern zone. Geomechanical modeling based on calibrated elastic moduli, in-situ stresses, fracture gradients, and rock strength parameters indicates strong lithological contrasts, with overburden shales exhibiting higher stiffness and frictional resistance relative to the sandstone units. Dynamic simulation over a 48-year injection period indicates an initial pressure decline associated with prior hydrocarbon depletion, followed by gradual pressure build-up during CO2 injection from 3640 psi to approximately 4140 psi. CO2 plume migration is preferentially eastward toward the reservoir crest due to variations in net-to-gross ratio and permeability, with bypassed zones identified along the flanks. Relative permeability trends suggest high injectivity at low water saturations but reduced sweep efficiency at elevated saturations, supporting zonation-based injection.
The origin and timing of the separation of the Kabul Block from Greater India remain debated. The western volcanic passive margin of the Indian Plate, shaped by lithospheric stretching and rift-basin development, experienced significant magmatism during successive continental break-up events. However, magmatism related to rifting between Greater India and the Kabul Block remains poorly constrained. The discovery of ca. 124 Ma ultramafic lamprophyres (UMLs) in the Kutch region represents one of the earliest recognized occurrences of alkaline magmatism along the western margin of India. This study investigates two UML dykes characterized by porphyritic textures and prominent phenocrysts of olivine, clinopyroxene, and phlogopite. Their trace-element characteristics, including La/Yb ratios of 66–76 and Dy/Yb values of ∼4, closely resemble those of global damtjernites and indicate derivation from the garnet stability field and an enriched deep lithospheric mantle source rather than a depleted mantle reservoir. Trace-element modelling further suggests that these melts were generated by very low degrees of partial melting (up to 2%) of a phlogopite-bearing garnet lherzolite source.Paleomagnetic investigations, carried out for the first time in this study, indicate emplacement between ca. 130 and 124 Ma, corroborating previous radiometric ages while also suggesting a substantial temporal offset between the two dykes. This phase of UML magmatism, together with emplacement of other Early Cretaceous alkaline complexes in western India, is interpreted to be related to the separation of the Kabul Block from Greater India, driven by slab pull-induced lithospheric thinning and rifting. Paleomagnetic data further suggest a shift in paleolatitude from ∼25°S to ∼22°S during emplacement of the two dykes, possibly reflecting counter clockwise rotation of the Indian Plate. The studied UMLs also preserve evidence for ∼8–10° tilting of the Indian Plate, interpreted as a consequence of Kerguelen plume impingement beneath the Indian subcontinent. However, a direct role of the Kerguelen mantle plume in the genesis of the Early Cretaceous UMLs of Kutch and associated alkaline magmatism in western India is not supported. Instead, the results emphasize the importance of major plate-tectonic processes, particularly rifting, and provide new insights into the tectono-magmatic evolution of the Indian Plate during ca. 130–110 Ma.
The Potiguar Basin (PB), located in northeastern Brazil, is one of the most important sedimentary basins in the country and has a complex evolution associated with West Gondwana. In this study, we present a model developed from the integration of geophysical and petrological data to evaluate the thermal, compositional, density, and seismic structures of the crust and upper mantle along the southwest–northeast profile (A–B) beneath the PB in the Brazilian Equatorial Margin (BEM). The model separates the crust and mantle into distinct bodies. Crustal bodies are constrained by geophysical observations, whereas mantle bodies are defined by their major element chemical composition. The crustal structure results of this contribution indicate that the continental basin section has a thick crust, about 32 km, which thins to about 20 km at the continent‑ocean transition (COT) zone. In the oceanic region, the crust is significantly thinner, with thicknesses ranging from ∼10–15 km. The results of the lithospheric structure indicate a notable lateral variation along the profile. The lithospheric thickening in the continental region reaches ∼150 km near the southwest end of the profile. However, the PB shows lithospheric thinning and a reduced ∼100 km thickness. The oceanic lithospheric thickness modeled is ∼130 km. Furthermore, the results of this study show a sub-lithospheric anomaly characterized by low density, high temperatures, and low P- and S-wave seismic velocities, suggesting the presence of a thermally anomalous mantle beneath the basin that maintains a thin lithosphere. We interpret this anomaly as a localized mantle hotspot, possibly related to the Fernando de Noronha hotspot or intraplate magmatic events that occurred in the Cenozoic.
Accurate characterization of capillary pressure and relative permeability is essential for understanding multiphase flow in low-permeability reservoirs, yet conventional empirical models often fail to capture the nonlinear behaviour associated with heterogeneous shale systems. This study develops a hybrid Group Method of Data Handling-Discrete Differential Evolution (GMDH-DDE) framework to predict the capillary pressure J-function and relative permeability using laboratory-derived mercury intrusion capillary pressure (MICP) and petrophysical measurements from the Wufeng-Longmaxi shale in the Jiaoshiba Gas Field. The model incorporates capillary pressure, permeability, porosity, average pore-throat radius, and sorting coefficient as predictor variables. The hybrid GMDH-DDE model demonstrates superior predictive capability compared to C-GMDH, particle swarm optmization artificial neural networks (PSO-ANN), and XGBoost models. For J-function estimation, the model attains R2 = 0.9992 (training) and R2 = 0.9999 (testing), with low errors (MAE = 0.082; RMSE = 0.0319). For relative permeability prediction, GMDH-DDE achieves R2 = 0.99972 (training) and R2 = 0.99889 (testing), with minimal error (MAE = 0.00237; RMSE = 0.00306). Independent validation confirms the hybrid GMDH-DDE model's robustness (R2 = 0.99961; RMSE = 0.00221; MAE = 0.00282), demonstrating excellent agreement with field-based measurements. These results establish GMDH-DDE as a reliable and generalizable tool for modelling capillarity-controlled flow behaviour in ultra-low-permeability shales. The enhanced predictive performance supports improved reservoir characterization, more accurate multiphase flow simulation, and optimized development planning for shale gas reservoirs.
The crust-mantle magmatism is crucial for understanding the Late Paleozoic subduction and closure history of the Paleo-Asian Ocean (PAO). The tectonic evolution of the eastern PAO remains controversial, which makes the study of magmatic assemblages at the northern margin of the North China craton (NCC) essential for deciphering the evolutionary history of this region. In this study, we present petrological, geochronological, geochemical, and in situ zircon Hf isotopic data from the Early Permian basic, intermediate, and acidic intrusive rocks in the Shangyi area. Zircon U-Pb dating yielded ages of 289 Ma for the monzonite, 289 Ma for the monzogranite, and 283 Ma for the diabase. The studied monzonite is characterized by low SiO2 (57.68-64.28 wt%) content, high Al2O3 (13.54-16.42 wt%) content, and the A/CNK value ranges from 0.78 to 0.95, exhibiting characteristics of Itype granite. Coupled with variable zircon epsilon Hf(t) values of -8.03 to -11.03, this suggests that the parental magma was derived from the partial melting of amphibolite/basalt in the lower crust. The monzogranite contains high SiO2 (73.68-75.36 wt%) and Al2O3 (11.93-12.39 wt%), with lower MgO content (0.21-0.63 wt%). The zircon epsilon Hf(t) value ranges from -7.64 to -9.78, indicating its affinity with highly fractionated I-type granites formed by partial melting of greywackes in the lower crust. They are all enriched in large ion lithophile elements and light rare earth elements, and depleted in high field strength elements and heavy rare earth elements, formed in an active continental margin tectonic environment. The geochemical characteristics of the mafic microgranular enclaves, monzogabbro, and diabase indicate that they are alkaline to peralkaline rocks, formed during the southward subduction of the PAO slab beneath the northern margin of the NCC in the Early Permian. The break-off of the subducted slab induced upwelling of asthenosphere, which originated from the partial melting of garnet-spinel lherzolite in the enriched mantle. Synthesized data from this and previous studies leads us to favor a bidirectional subduction model of the PAO in the Early Permian, with the PAO not closed before the Early Permian.
The Western Ghats, India, a seaward-facing topographic escarpment whose origin remains debated, is well developed over hundreds of kilometres in southwestern India and exposes diverse structures, tectonic fabrics, and rock formations. Detailed analyses and modelling of newly recorded precise aeromagnetic data, supplemented by results from magnetotelluric studies and several boreholes drilled through Deccan basalt and granitic basement rocks in the reservoir-triggered earthquake region of Koyna-Warna across the Western Ghats, resolve basalt thickness and basement morphology. The undulations in the Precambrian granitic-gneiss basement surface are relatively small, varying in the range 100-200 m, compared to the relief of the Western Ghats (800-1400 m). The average depth of basalt-granite/gneiss basement interface lies similar to 300 m below the present-day mean sea level (m.s.l.), indicating subsidence at the time of basalt emplacement (considering the absence of pillow basalt in drill core) and 100-150 m higher m.s.l. at the time of volcanism (similar to 65 Ma). Granite-gneiss terrain, similar to that found below Deccan basalt, is exposed at similar to 800-1000 m elevation above m.s.l. to the south of the basaltic region of Western Ghats, and magnetostratigraphic information shows normal polarity zones above similar to 600 m elevation, consistent with preserved stratigraphy. Combined geophysical constraints demonstrate that uplift (similar to 1000 m) and denudation since the Cretaceous, rather than pre-existing basement relief, largely shaped the escarpment. The absence of intertrappean sediments in boreholes supports rapid basalt emplacement and subsequent epeirogenic uplift. These results offer new constraints on uplift mechanisms at volcanic passive margins and highlight the role of post-volcanic vertical motions in sculpting the Western Ghats topography.
Crustal stress field inferred from focal mechanism solutions is a key parameter for understanding active tectonics and assessing the occurrence of large earthquakes. In this study, we investigate the present-day stress field in northwestern Iran and its tectonic regime. As an active tectonic region, northwestern Iran is situated within the central part of the Arabia-Eurasia collision zone, an area that has experienced destructive historical and instrumental earthquakes. We compiled 216 focal mechanism data collected from the seismological centers and published literature. Also, we determined the focal mechanisms of 48 small earthquakes with magnitudes 3.8 <= M-w <= 4.8. We grouped the 264 focal mechanisms in 11 distinct zones based on their geographical proximity, kinematic homogeneity, tectonic setting, relatively similar earthquake focal mechanisms, and geodetic data. For each zone, focal mechanism solutions were analyzed using the STRESSINVERSE and Win-Tensor packages to establish the present-day stress field and characterize the active tectonics. Both methods show approximately similar results for horizontal stress axes orientations and the tectonic regimes. Stress inversion provides a first-order stress field with an NNW-SSE (N162 degrees) maximum horizontal compressive stress (SHmax) direction corresponding to a general strike-slip tectonic regime related to the Arabia-Eurasia convergence. This stress field is responsible for the accommodation of shortening and strike-slip movement along the NW-trending and NE-trending strike-slip faults. Underthrusting rigid South Caspian Block, block rotation, escape tectonics, and strain partitioning occurred due to second and third-order stress fields. Our result provides more details of the stress field for a better understanding of the mechanisms of seismic activity and crustal deformation in northwestern Iran and the nearby regions.
Monitoring co-seismic gravity changes through continuous gravity observations is of considerable scientific importance for understanding the surface and underground mass redistribution associated to the earthquake processes. In this study, we analyze continuous gravity data from six stations of the Chinese Continuous Gravity Network in Fujian Province to investigate the co-seismic gravity change characteristics associated with the Hualien Ms 7.3 earthquake. To enhance signal extraction, we apply the short-time Fourier transform (STFT) to the gravity records and compare its performance with that of exponential and step-function fitting methods. The results indicate that the STFT approach yields substantially more accurate co-seismic change signals. When evaluated against a viscoelastic layered half-space model and the spherical dislocation theory, the STFT method improves accuracy by more than 20% relative to the other two fitting methods. Further analysis shows that regional geological conditions, manifested through background noise levels, significantly affect the retrieval of co-seismic signals; however, the application of the STFT method effectively suppresses such regional geological influences, thereby enabling more reliable extraction of the earthquake-induced gravity changes. Overall, our findings demonstrate that gPhone gravimeters provide high precision and stability in the low-frequency range, and that the STFT technique offers a robust tool for precise extraction of co-seismic gravity signals, thereby reinforcing the foundations for optimizing earthquake early warning systems and advancing studies of earthquake source mechanisms.
This study represents the pioneering application of calcite U-Pb dating to directly date multiple deformation events in the eastern Sichuan Basin, China. This approach is crucial for advancing our understanding of the Meso-Cenozoic tectonic evolution of the Yangtze Block and the Tibetan Plateau. We present calcite U-Pb dating results from three reverse/strike-slip faults, which allow us to constrain four distinct deformation events. The data reveal that the first deformation event along the approximately west-east-striking reverse fault occurred at the end of the Middle Jurassic (similar to 164 Ma). This event is associated with northward subduction of the Bangong-Nujiang Ocean. Subsequent deformation event along the northeast-striking Qiyueshan Fault Zone occurred during the Early Cretaceous (similar to 135 Ma) and is interpreted as resulting from far-field oblique flat-slab subduction of the Paleo-Pacific Plate. Reactivation of the Qiyueshan Fault Zone during the Eocene (similar to 48 Ma) was driven by NW-SE compression associated with the thrusting of the Longmenshan fold-thrust belt, marking the first documented instance of this deformation event in the eastern Sichuan Basin. The youngest age, dating to the Oligocene (similar to 28 Ma), is linked to a near north-south-striking strike-slip fault. This final deformation event is attributed to the eastern expansion of the Tibetan Plateau and the subsequent counterclockwise rotation of the Sichuan Basin.
The eastern and northeastern (NE) Tibet serves as a natural laboratory for unraveling the evolutionary history, uplift mechanisms, and outward growth of the Tibetan Plateau. In this study, we employed ambient noise tomography to construct a 3-D crustal SH-wave velocity (VSH) model extending to 60 km depth beneath eastern and NE Tibet, based on fundamental-mode Love-wave dispersion measurements (5-40 s) from seismic data recorded at 165 stations. We derived the radial anisotropy structure across the study region by integrating our VSH model with existing 3-D SV-wave (VSV) model. Through the combined analysis of VSH and radial anisotropy structures, we delineated the possible extent of mid-lower crustal ductile flow beneath NE Tibet. Cross-validation with previous magnetotelluric imaging results helped to exclude confounding effects from non-flow mechanisms (e.g., mineral lattice-preferred orientation) on the identification of ductile flow boundaries, thereby confirming the robustness of our delineation. Notably, our model reveals an isolated low-VSH anomaly beneath the Qilian orogen, which we interpret as resulting from the upwelling of mantle-derived material induced by the southward underthrusting of the Alxa block. To illustrate this, we propose a conceptual model to explain the genesis of this isolated low-VSH anomaly. These findings shed new light on the deep dynamic processes in eastern and NE Tibet.
The studied part of the Central Western Carpathians represents a pile of thick-and thin-skinned thrust sheets of the Tatric, Fatric and the uppermost Hronic nappe systems, appearing today in the form of an arc. From the two lower units Mesozoic paleomagnetic results of limited number were published from the western and central segments of the nappe stack, while the eastern segment was well represented. Due to the distribution of the clockwise and counterclockwise rotated paleo-declinations the oroclinal bending was considered as a possible model to account for the shape of the Central Western Carpathians. The uppermost Hronic Unit, however, exhibits only clockwise rotations. The primary aim of this study was to collect new data from the western and central segments of the lower units to decide if they were bended before the emplacement of the Hronic Unit between 90 and 84 Ma. The new results come from 26 localities of Middle Triassic to Lower Cretaceous (mid-Eocene) formations. In the western sector and the outer zones of the central sector post-Middle Eocene remagnetizations related to long-lasting contractional deformation were recognized. They are interpreted as reflecting Miocene similar to 50 degrees counterclockwise rotation of the ALCAPA. Locally occurring counterclockwise rotated paleodeclinations elsewhere (earlier published data) may be related to pre-Late Cretaceous tectonic movements. With the addition of data from the present study, mainly from the central segment of the Central Western Carpathians, there are now 46 locality-mean paleomagnetic directions which must have acquired the magnetic signal during the Cretaceous Normal Polarity interval. They do not indicate significant difference in the general rotation between the central and eastern segments of the Tatric and Fatric units. These results constrain a post-84 Ma similar to 70 degrees clockwise rotation of the Central Western Carpathian nappe stack, taken into account the similar to 50 degrees counterclockwise regional Miocene rotation, which may indicate closing of the South Penninic-Vahic ocean.
Long-term seismic activity along the Main Himalayan Thrust (MHT) raises significant concern for the Kumaun Himalaya. Using the most updated high-resolution integrated velocity field based on InSAR and GPS observations, the present study aims to provide spatial distribution of interseismic slip rates and fault geometry of MHT in the Kumaun region. Results through the Bayesian inversion framework reveal several key features of fault behavior: dip angles range between 28.2 degrees and 34.2 degrees, with locking depths of approximately 6.7 +/- 0.7 km to 9.9 +/- 0.2 km, and fault depths around 12.9 +/- 0.4 km. The transition zone from locked to creeping portion displays slip rates of 1.7 +/- 0.6 mm/yr to 1.9 +/- 0.9 mm/yr. Estimated long-term slip rate of the MHT is 19.7 +/- 0.2 mm/yr, with a slip deficit rate of 18.0 mm/yr. The estimated moment deficit rate is approximately 5.40 x 1018 Nm/yr, which suggests the potential for a great earthquake of magnitude Mw 8.3, assuming a seismic cycle of similar to 500 years. Thus, the estimated slip deficit from the integrated velocity field highlights significant seismic hazards in the locked segments of the MHT. Overall, the findings provide crucial inputs for seismic risk assessment and mitigation efforts in the Kumaun Himalaya.
This study focuses on the eastern part of the Khazar Fault Zone, situated in N-NE Iran between the South Caspian Basin, Kopeh Dagh, and the Alborz Mountains, with the Gorgan Plain within it, as part of the seismically and tectonically active Alpine-Himalayan Mountain Belt. Additionally, widespread land subsidence is occurring in the Gorgan Plain, making the investigation of this region crucial. The aim of this research is to monitor surface deformation in the study area, assess its relationship with tectonic activity to minimize and mitigate potential hazards, and provide insights into the tectonic model of the region. We processed LiCSAR interferograms with LiCSBAS using Sentinel-1A images from January 2015 to March 2023 (descending track) and December 2023 (ascending track), calculating mean line-of-sight (LOS), vertical, and lateral velocities for the study area. Aqqala town and the eastern Gorgan region, situated on the footwall of the Khazar Fault Zone, experience the highest vertical deformation rates, reaching approximately -118.81 mm/yr and -146.20 mm/yr, respectively, over an 8-year period. Moreover, the left-lateral movement rates along the eastern section of the Khazar Fault Zone range from a mean of 3.79 mm/yr to a maximum of 8.46 mm/yr, with displacement decreasing from east to west. The results show that the eastern part of the Khazar Fault Zone is active with a left lateral component and indicate the presence of a likely NE-SW trending, north-dipping reverse/thrust fault beneath the Gorgan Plain, which is identified as the Aqqala Fault. It seems that the Aqqala Fault identified beneath the Gorgan Plain may be the source of significant seismic activity, as indicated by the earthquakes with magnitudes >= 5 Mw that occurred on October 7, 2004, and January 10, 2005. Our findings clearly show that the deformation in the region is controlled not only by anthropogenic factors, as mentioned in previous studies but also by tectonic activity. These findings demonstrate that the study area is highly active and poses a significant earthquake hazard, highlighting the urgent need for appropriate measures to be taken to address this concern.
Large Igneous Provinces (LIPs) are characterized by vast volumes of mafic lava flows and a complex network of intrusive rocks, including dike swarms, sill complexes, and layered intrusions that, together, compose the magmatic plumbing system. These magmatic events typically occur over short durations (1-5 Myr) and provide critical insights into magmatic processes and their interactions with surrounding rocks. Recent geological mapping in the Southern Brazilian Coastal region reveals a connected network of sills and dikes that represent the exposed plumbing system of high-Ti Urubici (Khumib) magma type of the Parana Etendeka Magmatic Province (PEMP). To better constrain the extent of the intrusive bodies and investigate their link to the lava flows, we integrated field, petrographic, airborne magnetic, and whole-rock geochemical data. Magnetic field products corroborated with the field-observed interconnected intrusive bodies and highlighted the concentration of deep and shallow, large magma chambers within the area, as well as the connectivity between these reservoirs and vertical conduits. Geochemical analysis indicated that sills, dikes, and lava flows share a common origin linked to the high-Ti Urubici (Khumib) magma type that evolved through fractionation in shallow level magma chambers and partially assimilate melts from country rocks in the conduits. The results of our holistic geophysical and geological approach demonstrated that contamination and melting processes are intricately linked to the dynamics of the transcrustal high-Ti Urubici plumbing system and highlights the shallow emplacement of large volumes of mafic sills and the melting of the country rocks as a cause-effect relation.
Studying the Glacial Isostatic Adjustment (GIA) and land uplift modeling can be carried out utilizing geodetic observations (GNSS and precise leveling measurements), and geophysical methods. The Gravity Recovery and Climate Experiment (GRACE) satellite missions' data has not been formally used in this context in Fennoscandia. If there is insufficient coverage of offshore or onshore data, existing estimates of GIA might be partially biased (by means of spatial pattern and magnitude), particularly over the Gulf of Bothnia where the land uplift rate reaches its maximum. To inspect this issue, we incorporated the GRACE data in estimates of the land uplift rate due to GIA. Despite satellite gravitational information having a low resolution (similar to 300 km) it can be used for this purpose because the GIA in Fennoscandia has a large-scale regional pattern. Our findings confirmed a bias in existing estimates. According to our results, the maximum land uplift rates reach 9.1 mm/year in the northern part of the Gulf of Bothnia, while previous estimates indicate that the maximum value is shifted westward towards land. Since GRACE data also comprises hydrological signals, we assessed its effect on the satellite gravitational information by applying different hydrological models. Our results ascertained that land uplift estimates in Fennoscandia were not significantly affected by long-term hydrological mass variations. According to our estimates over the period between 2003 and 2017, the hydrological loading effect was approximately 0.1 mm/ year or less (in terms of the RMS differences when compared to the reference land uplift model). Hydrological signal variations (over the investigated period of two decades) were, therefore, dominated mainly by seasonal variations without the presence of secular trends. The results show that the land uplift model from GRACE has some discrepancies compared to existing models, so the main idea of this article is to combine land and satellite data. Therefore, we studied a combined land uplift model using GRACE and the latest land uplift model in Fennoscandia.
Magmatic activity during the Triassic-Jurassic transition coincided with the breakup of Pangea, marking a pivotal period in Western European tectonic evolution. However, this activity remains poorly documented in the External Western Alps. Dating the emplacement and alteration of Triassic magmatic rocks such as the spilites in the Alps has long been challenging due to the complex alteration history and the scarcity of suitable mineral phases. This study employs in situ U-Pb dating of carbonate to constrain the timing of hydrothermal alteration of spilites from the Pelvoux massif (France), offering a new temporal framework for these processes. Dolomite and calcite filling vesicles and veins in the spilites yield ages of 201 +/- 15 Ma and 202 +/- 47 Ma, respectively, consistent with the stratigraphic emplacement interval of these lavas during the Upper Triassic. Notably, the U-Pb system in dolomite has preserved hydrothermal conditions related to magmatic emplacement, without resetting during two subsequent geological events at temperatures approaching 300 degrees C, emphasizing its reliability as a chronometer in this context. The obtained ages overlap with the temporal framework of the Central Atlantic Magmatic Province (CAMP) and geochemical signatures of the spilites correspond to medium/high-Ti transitional to alkaline basalts, comparable to continental basalts such as those of the CAMP. This suggests a shared tectono-magmatic context with mantle-derived magmatism. Furthermore, the spatial proximity of the studied spilites to lower crustal CAMP-related magmatism in the Internal Alps supports a potential genetic relationship, with magma ascent likely facilitated by inherited tectonic structures during the Upper Triassic extension and the opening of the Alpine Tethys. Hydrothermal alteration, marked by spilitization and carbonate precipitation, occurred under low- to moderate-temperature conditions (70-360 degrees C), possibly driven by marine or continental-derived fluids. By providing the first absolute geochronological constraints on spilites in the External Western Alps, this study expands the recognized extent of CAMP. It underscores the utility of carbonates as reliable archives for unraveling hydrothermal and magmatic histories.
