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Abstract: The formation of Lau Basin records an extreme event of plate tectonics, with the associated Tonga trench exhibiting the fastest retreat in the world (16 cm/yr). Yet paleogeographic reconstructions suggest that seafloor spreading in the Lau Basin only initiated around 6 Ma. This kinematics is difficult to reconcile with our present understanding of how subduction drives plate motions. Using numerical models, we propose that eastward migration of the Lau Ridge concurrent with trench retreat explains both the narrow width and thickened crust of the Lau Basin. To match the slab geometry and basin width along the Tonga‐Kermadec trench, our models suggest that fast trench retreat rate of 16 cm/yr might start ~15 Ma. Tonga slab rollback induced vigorous mantle flow underneath the South Fiji Basin which is driving the extension and thinning of the basin and contributing to its observed deeper bathymetry compared to neighboring basins.

The tectonic evolution and crustal accretion process of the North Qilian Orogenic Belt (NQOB) are still under debate because of a lack of integrated constraints, especially the identification of the tectonic transition from arc to initial collision. Here we present results from zircon U–Pb geochronology, whole-rock geochemistry, and Sr–Nd–Pb isotope geochemistry of the Beidaban granites to provide crucial information for geodynamic evolution of NQOB. Zircon U–Pb dating yields an age of 468 ± 10 Ma for the Beidaban granites and most of the Beidaban samples contain amphibole, are potassium-rich, and have A/CNK values ranging from 0.7 to 0.9, illustrating that the Middle Ordovician Beidaban granites are K-rich, metaluminous, calc-alkaline granitoid. The geochemical characteristics indicate that the Beidaban granites are transitional I/S-type granitoids that formed in an arc setting. The isotopic compositions of initial (87Sr/86Sr)i values ranging from 0.70545 to 0.71082 (0.70842 on average) and εNd(t) values ranging from − 10.9 to − 6.7 (− 8.8 on average) with two-stage Nd model ages (TDM2) of 1.74–2.08 Ga suggest that the Beidaban granites originated from Paleoproterozoic crustal materials. In addition, the initial Pb isotopic compositions (206Pb/204Pb = 19.14–20.26; 207Pb/204Pb = 15.71–15.77; 208Pb/204Pb = 37.70–38.26) and geochemical features, such as high Th/Ta (17.43–30.12) and Rb/Nb (6.01–15.49) values, suggest that the Beidaban granite magma source involved recycled crustal components with igneous rocks. Based on these results in combination with previously published geochronological and geochemical data from other early Paleozoic igneous rocks, we suggest that the timing of the tectonic transition from arc to the initial collision to the final closure of the North Qilian Ocean can be constrained to the Middle-Late Ordovician (ca. 468–450 Ma). [ABSTRACT FROM AUTHOR]

The analysis of the splitting signature of XKS phases is crucial for constraining seismic anisotropy patterns, especially in complex subduction settings such as outward-dipping double subduction. A natural example of this is found in the Central Mediterranean, where the Apennine and the Dinaride slabs subduct in opposite directions, with the Adriatic plate separating them. To assess the capability of XKS-splitting analysis in revealing anisotropic seismic properties, such as fast polarization directions and shear wave anisotropy (in per cent), we use three-dimensional numerical geodynamic models combined with texture evolution simulations. In these models, two identical outward-dipping oceanic plates are separated by a continental plate. Using the full elastic tensors – directly derived from the texture evolution simulations – we compute anisotropic seismic properties and synthetic teleseismic waveforms. From these waveforms synthetic observables are determined, including apparent splitting parameters (fast polarization directions and delay times) and splitting intensities. Based on these observables, we (1) derive models for a single anisotropic layer (one-layer model), (2) identify regions with significant depth-dependent anisotropic seismic properties, and (3) perform inversions at selected locations in terms of two anisotropic layers (two-layer model). We consider two geodynamic models: one with a strong (M1) and one with a weak (M2) continental plate. Model M1 exhibits significant retreat of the subducting plates with no horizontal stretching of the continental plate, whereas Model M2 shows less retreat, substantial horizontal stretching, and detachment of the subducting plates. These different subduction styles result in distinct flow and deformation patterns in the upper mantle, which are reflected in the anisotropic seismic properties. In Model M1, the fast polarization directions below the continental plate are predominantly trench-parallel, whereas in Model M2, they are mostly trench-normal. In most regions of both models, the one-layer models are sufficient to resolve the anisotropic seismic properties, as these properties are nearly constant with depth. However, for both models, we identify some isolated regions – primarily near the tips of the subducting plates and beneath the continental plate – where fast polarization directions exhibit significant variations with depth. Inverting the apparent splitting parameters in these regions yields multiple two-layer models at each location that excellently fit the observables. However, their anisotropic seismic properties can vary significantly, and not all these two-layer models adequately approximate the true depth variations. This ambiguity can be partially reduced by selecting two-layer models in which the summed shear wave anisotropy closely matches that of one of the one-layer models, as these models better capture the true variations. [ABSTRACT FROM AUTHOR]

The planform is a defining feature of mantle convection. It can be gleaned from the stratigraphic record by mapping the continent-scale distribution of hiatus and no hiatus surfaces serving as a proxy for high and low dynamic topography. We carry this out for all continents apart from Antarctica for eight geological series since the Upper Jurassic, showing that: (i) the planform as indicated by our maps contains wavelengths of the order of 1000 km, smaller than the convective scales implied by the geoid. (ii) The planform changes on timescales of geological series (10–20 Myrs), smaller than the mantle transit time. (iii) Flood basalt eruptions are frequently preceded by hiatus surfaces. (iv) Some hiatus surfaces are not linked to any known plume, potentially reflecting the lateral transport of material in the asthenosphere. Our results reveal the importance of mantle viscosity stratification in shaping the convective planform and the resulting dynamic topography. Geodynamic Earth models should aim to reproduce the global characteristics of our maps, as well as specific regional events identified in this work. Finally, we separate the effects of sea-level variation from regional changes in base level induced by dynamic topography by contrasting the stratigraphic evolution of different regions. [ABSTRACT FROM AUTHOR]

Intermediate-depth earthquakes, accommodating intraslab deformation, typically occur within subduction zone settings at depths between 60–300 km. These events are in a unique position to inform us about the geodynamics of the subducting slab, specifically the geometry of the slab and the stress state of the host material. Improvements in the density and quality of recorded seismic data enhance our ability to determine precise locations of intermediate-depth earthquakes, in order to establish connections between event nucleation and the tectonic setting. Depth phases (near-source surface reflections, e.g. pP and sP) are crucial for the accurate determination of earthquake source depth using global seismic data. However, they suffer from poor signal-to-noise ratios in the P wave coda. This reduces the ability to systematically measure differential traveltimes to the direct P arrival, particularly for the frequent lower magnitude seismicity which highlights considerable seismogenic regions of the subducted slabs. To address this limitation, we have developed an automated approach to group globally distributed stations at teleseismic distances into ad-hoc arrays with apertures of 2.5 |$^\circ$|⁠ , before optimizing and applying phase-weighted beamforming techniques to each array. Resultant vespagrams allow automated picking algorithms to determine differential arrival times between the depth phases and their corresponding direct P arrival. Using these differential times we can then determine the depths of earthquakes, which in turn can be used to create a catalogue of relocated events. This will allow new comparisons and insights into the governing controls on the distribution of earthquakes in subducted slabs. We demonstrate this method by relocating intermediate-depth events associated with northern Chile and the Peruvian flat slab regions of the subducting Nazca plate. The relocated Chilean catalogue contains comparable event depths to an established catalogue, calculated using a semi-automated global methodology, which serves to validate our fully automatic methodology. The new Peruvian catalogue we generate indicates three broad zones of seismicity approximately between latitudes 1–7 |$^\circ$| S, 7–13 |$^\circ$| S and 13–19 |$^\circ$| S. These align with flat to steep slab dip transitions and the previously identified Pucallpa Nest. We also find a regionally deeper slab top than indicated by recent slab models, with intraslab events concentrated at points where the slab bends, suggesting a link between slab flexure and intermediate-depth earthquake nucleation. [ABSTRACT FROM AUTHOR]

Starting from observed variations of the length of day in the past 2.5 billion years, we calculate the corresponding gravity variation and evaluate the possible effects that such variation would have induced on the lithosphere and on mantle convection. The lithospheric stress induced by the observed gravity increase at the equator in 500 Ma is of the same order as the one associated with a convective cell. We model a gravity increase that would result in 1.3 × 10−2 µGal or 1.3 × 10−10 m s−2 over 10 years, a value that is not far from the detection thresholds of modern gravimeters. Gravity increase also affects mantle dynamics by improving convection efficiency. Our models demonstrate that gravity variations contribute to this phenomenon through faster and wider mixing. The results support a view where a convective system being subject to gravity changes responds through non-linear adjustments of its effective mixing at all scales. These findings contribute to a deeper understanding of how gravitational fluctuations may shape the behavior of Earth's dynamic systems over geological timescales. [ABSTRACT FROM AUTHOR]

The relationship between the lithosphere and the mantle during the supercontinent cycle is complex and poorly constrained. The processes which drive dispersal are often simplified to two end members: slab pull and plume push. We aim to explore how lithosphere thickness and viscosity during supercontinent assembly may affect the interaction of deep mantle structures throughout the supercontinent cycle. We consider supercontinental lithosphere structure as one of many potential processes which may affect the evolution of upwellings and downwellings and therefore systematically vary the properties of continental and cratonic lithosphere, respectively within our 3D spherical simulations. The viscosity and thickness of the lithosphere alters the dip and trajectory of downwelling material beneath the supercontinent as it assembles. Focusing on Pangea, we observe that plumes evolve and are swept beneath the center of the supercontinent by circum‐continental subduction. The proximity of these upwelling and downwelling structures beneath the supercontinent interior varies with lithosphere thickness and viscosity. Where slabs impinge on the top of an evolving plume head (when continental and cratonic lithosphere are thick and viscous in our simulations), the cold slabs can reduce the magnitude of an evolving plume. Conversely, when the continental lithosphere is thin and weak in our simulations, slab dips shallow in the upper mantle and descend adjacent to the evolving plume, sweeping it laterally near the core‐mantle boundary. These contrasting evolutions alter the magnitude of the thermal anomaly and the degree to which the plume can thin the lithosphere prior to breakup. Plain Language Summary: Tectonic plates have gone through many cycles throughout geological history with continents colliding to form supercontinents and then breaking apart to reassemble elsewhere. The way in which Earth's surface and interior work together to drive this process is not well understood. We consider the relationship between slabs, which sink toward the core‐mantle boundary (CMB) as a supercontinent assembles, and plumes, which rise from the CMB to the surface and may aid in supercontinent breakup. We find that the structure of Earth's surface layer can change the morphology of slabs as they descend. This is important as slabs may determine the location and magnitude of plumes in the deep Earth, depending on the way that slabs and plumes interact. These plumes may feed back toward supercontinent breakup as they thin the Earth's surface layer, the lithosphere, indicating that the dynamics at the surface during the formation of the supercontinent may affect the forces contributing to breakup. Key Points: The effects of varying lithosphere structure during supercontinent assembly can be observed in the mantle through the supercontinent cycleThick, viscous continents promote steeper slab dips which can impact the proximity of slabs and plumes beneath a supercontinent interiorProximity of slabs to upwellings in the mantle may impact the magnitude of the plume and the extent of lithosphere thinning near the surface [ABSTRACT FROM AUTHOR]

Subduction zones play a pivotal role in the mechanics of plate tectonics by providing the driving force through slab pull and weak megathrusts that facilitate the relative motion between tectonic plates. The initiation of subduction zones is intricately linked to the accumulation of slab pull and development of weakness at plate boundaries and, by consequence, the largest changes in the energetics of mantle convection. However, the transient nature of subduction initiation accompanied by intense subsequent tectonic activity, leaves critical evidence poorly preserved and making subduction initiation difficult to constrain. We overcome these limitations through a comprehensive analysis focused on Puysegur, a well-constrained extant example of subduction initiation offshore South Island, New Zealand. Through time-dependent, three-dimensional thermo-mechanical computations and quantitative comparison to new geophysical and geological observations, including topography, stratigraphy, and seismicity, we demonstrate that subduction initiation develops with a fast strain weakening described with a small characteristic displacement (Δs ≈ 4 to 8 km). Potential physical mechanisms contributing to the strain weakening are explored and we find that the observed fast weakening may arise through a combination of grain-size reduction within the lower lithosphere and fluid pressurization at shallower depths. With the shared commonality in the underlying physics of tectonic processes, the rapid strain weakening constrained at Puysegur offers insights into the formation of the first subduction during early Earth and the onset of plate tectonics. [ABSTRACT FROM AUTHOR]

Plate tectonics drives the compositional diversity of Earth's convecting mantle through subduction of lithosphere. In this context, the role of evolving global geodynamics and plate (re)organization on the spatial and temporal distribution of compositional heterogeneities in the convecting mantle is poorly understood. Here, using the geochemical compositions of intracontinental basalts formed over the past billion years, we show that intracontinental basalts with subchondritic initial neodymium-144/neodymium-143 values become common only after 300 million years, broadly coeval with the global appearance of kimberlites with geochemically enriched isotopic signatures. These step changes in the sources of intraplate magmatism stem from a rapid increase in the supply of deeply subducted lithosphere during the protracted formation of Pangea following the widespread onset of "modern" (cold and deep) subduction in the late Neoproterozoic. We argue that the delay (~300 million years) in the appearance of enriched intraplate magmas reflects the time required for the sinking and (re)incorporation of slabs into the sources of mantle-derived magmas. [ABSTRACT FROM AUTHOR]

Surface heat flow (SHF) serves as a vital parameter for assessing the heat transfer from deep Earth to the surface, which can provide crucial insights into internal geodynamic processes. As the "roof of the world," the Tibetan Plateau and its tectonic evolution are highly important in terms of global climate change and geodynamic study. However, a comprehensive understanding of the SHF distribution across most regions of the Tibetan Plateau is limited due to sparse measurement data. To surmount this limitation, a spatially intelligent approach has been developed: The geographically neural network weighted regression with enhanced interpretability (EI‐GNNWR). This method integrates spatial heterogeneity and nonlinear interactions between geophysical and geological factors to predict the SHF distribution across the Tibetan Plateau. In this study, the EI‐GNNWR model is used to accurately predict SHF across the entire region. After evaluating the effectiveness and interpretability of the EI‐GNNWR model, our results demonstrate that medium to high SHF values are predominantly concentrated in the southern, northeastern, and southeastern sectors of the Tibetan Plateau. These observations suggest that the formation of zones with high SHF values may be strongly influenced by the Moho depth, ridges, topography, and average curvature of satellite gravity gradients. Especially, higher SHF values may indicate more profound geodynamic activities such as collisional orogeny, shear deformation zones, or lithospheric extension. These findings offer novel insights into the spatial patterns of SHF and deepen our understanding of the geothermal formation mechanisms driven by underlying tectonic activities. Plain Language Summary: Surface heat flow (SHF) is a critical parameter that helps explain the internal forces driving Earth's activities, such as plate collision. However, geothermal data from the Tibetan Plateau are scarce due to the fragile ecological environment. To address this limitation, a spatially intelligent method that emphasizes interpretability within models is proposed to predict SHF values and scrutinize the factors influencing geothermal genesis. Our results reveal that the southern, northeastern, and southeastern parts of the Tibetan Plateau characteristically have medium to high SHF values, which are closely associated with high geothermal zones on the Eurasian plate surrounding the Tibetan Plateau. Furthermore, the interrelations of SHF values with geophysical and geological features are investigated. The collision and compression of the Eurasian and Indian Ocean plates have led to significant tectonic activity in the Tibetan Plateau, resulting in shallow Moho depths in the active plate regions and high heat flow regions within the influence of the lithosphere. This study provides valuable insights into the SHF distribution and the underlying geophysical and geological mechanisms across the Tibetan Plateau. Key Points: An interpretable data‐driven approach that fully considers geological structural information and geophysical data is proposedA surface heat flow map of the Tibetan Plateau is predicted using a data‐driven methodThe key features of high geothermal formations on the Tibetan Plateau and the influential mechanisms are revealed [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is one of the biggest accretionary orogens in the world. With the development of laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS), large data of detrital zircon U–Pb and Hf isotopes have been published for decades, which leads to better understanding of the tectonic evolution and geodynamics of the CAOB. We compiled the data about the information of articles, samples and their analytical methods and results, then checked and corrected. These data are available to support future research activities in the CAOB, northern China, for example, the provenance analysis, climate changes and paleogeographic reconstruction. [ABSTRACT FROM AUTHOR]

Sixteen morphometric relief parameters have been identified whose positive anomalies correspond with seismic areas in the Greater Caucasus. An analysis of four parameters which were considered to provide the most information using the γ-operator in fuzzy logic has enabled us to develop a scheme for an index of neotectonic activity that was used along with the results of computerized geodynamic simulation to identify zones of possible earthquake sources. The new approach does not require detailed information on present-day and paleo seismicity, hence can be used to deal with an analogous problem for territories whose seismotectonics is poorly known. We have demonstrated an interrelationship between recent deformations and regional seismicity, and the possibilities offered by the method of lineament analysis due to Yu.V. Nechaev (2010) for identification of active faults. [ABSTRACT FROM AUTHOR]

Studying the patterns and characteristics of seismic activity and crustal deformation in Africa is vital for understanding the geodynamics and predicting seismic hazards in the region. By understanding the deformation characteristics, scientists can help mitigate the risk of earthquake-related disasters in Africa. However, assessing deformations has been difficult because of scarce historical and instrumental seismic records and geodetic data. In this study, the finite element analysis was used to determine the crustal deformations in the form of strains in the EARS from the tectonic model gravitational potential as a stress driver. The strain patterns in various regions were then assessed where reliable, independent studies could be validated. Finally, the inferences of crustal strains to crustal deformations in various parts of the continent were drawn. The simulation results showed us that the strain of the 2 × 10 - 8 / yr was observed in the Main Ethiopian rift, and it decreased in the EARS toward Mozambique. The strain in the convergent margins of North Africa was also in the order of ~ 2 × 10 - 8 / yr . However, the principal strains in the stable central and West African countries could reach ~ 4 × 10 - 9 / yr . Thus, the results were consistent with those from geodetic strains. In addition, a high degree of relationship existed between the seismic studies and model strains. [ABSTRACT FROM AUTHOR]

Many super‐Earths are on very short orbits around their host star and, therefore, more likely to be tidally locked. Because this locking can lead to a strong contrast between the dayside and nightside surface temperatures, these super‐Earths could exhibit mantle convection patterns and tectonics that could differ significantly from those observed in the present‐day solar system. The presence of an atmosphere, however, would allow transport of heat from the dayside toward the nightside and thereby reduce the surface temperature contrast between the two hemispheres. On rocky planets, atmospheric and geodynamic regimes are closely linked, which directly connects the question of atmospheric thickness to the potential interior dynamics of the planet. Here, we study the interior dynamics of super‐Earth GJ 486b (R=1.34 $R=1.34$R⊕ ${R}_{\oplus }$, M=3.0 $M=3.0$M⊕ ${M}_{\oplus }$, Teq≈700 ${\mathrm{T}}_{\text{eq}}\approx 700$ K), which is one of the most suitable M‐dwarf super‐Earth candidates for retaining an atmosphere produced by degassing from the mantle and magma ocean. We investigate how the geodynamic regime of GJ 486b is influenced by different surface temperature contrasts by varying possible atmospheric circulation regimes. We also investigate how the strength of the lithosphere affects the convection pattern. We find that hemispheric tectonics, the surface expression of degree‐1 convection with downwellings forming on one hemisphere and upwelling material rising on the opposite hemisphere, is a consequence of the strong lithosphere rather than surface temperature contrast. Anchored hemispheric tectonics, where downwellings und upwellings have a preferred (day/night) hemisphere, is favored for strong temperature contrasts between the dayside and nightside and higher surface temperatures. Plain Language Summary: The tectonic processes occurring on super‐Earths, which are rocky exoplanets with masses exceeding that of Earth, may differ significantly from those observed on the terrestrial planets in our solar system. Many super‐Earths are also expected to be tidally locked to their host star, so that always the same hemisphere faces the star. Tidal locking can lead to a strong temperature contrast between the dayside and nightside surface. Here, we investigate the influence of such strong surface temperature contrasts on the interior dynamics and tectonic behavior of super‐Earth GJ 486b, which is one of the best characterized Earth‐mass planets to date. We determined the surface temperature contrast between the dayside and nightside by assuming different efficiencies of atmospheric heat transport and ran global climate models for a set of different atmospheric compositions. Our 2D mantle convection simulations reveal that hemispheric tectonics, where cold material sinks on one hemisphere and hot material rises on the other side, emerges regardless of the surface temperature contrast if the planet has a strong lithosphere. However, a significant surface temperature contrast and an overall higher surface temperature tend to anchor the sinking cold material and rising hot material to the dayside and nightside respectively. Key Points: The mantle dynamics of super‐Earth GJ 486b are governed by the strength of the lithosphere and the day‐night surface temperature contrastDegree‐1 convection is a consequence of the strong lithosphere, rather than the temperature contrast between the dayside and nightsideA strong surface temperature contrast between the dayside and nightside can anchor downwellings to one hemisphere [ABSTRACT FROM AUTHOR]

New and previously published isotope-geochemical material on the Upper Cretaceous-Lower Paleogene volcanic complexes of the Ozernovsky-Valaginsky segment of the Achaivayam-Valaginsky paleoarc are presented. It is found that composition of rocks composing separate volcanic fields within the Achayvayam-Valagin paleoarc (terrane) is different. On Karaginsky Island, volcanics of the moderate-potassium calc-alkaline and shoshonite series are widespread. On Ozernaya Peninsula, low-potassium basalts of the tholeiitic series are predominantly developed. The rocks of the Kumroch Ridge include low-potassium basalt-basaltic andesite, medium-potassium calc-alkaline and high-potassium shoshonitic. Volcanic rocks of the Tumrok Ridge are represented by low-potassium picrites and high-potassium trachybasalt-trachyandesites. In the Valaginsky Ridge, low-potassium tholeiitic, moderate-potassium calc-alkaline and shoshonite-latite series, as well as picrites and lamproitoids are distinguished. Isotopic (Sr, Nd and Pb) and geochemical composition of the rocks indicate their formation from a depleted mantle source within an ensimatic volcanic arc. It is shown that in the absence of significant differences in the material composition of rocks, regional differences are manifested. It is suggested that large-ion lithophile elements enrichment of volcanics may relate to fluids introduced into the melts during the melting of the supra-subduction mantle wedge. Issues of geodynamics of the region are considered.

The Earth's mantle transition zone has significant control on material flux between upper and lower mantle, thus constraining its properties is imperative to understand dynamic processes and circulation patterns. Global seismic data sets to study the transition zone typically display highly uneven spatial distribution. Therefore, complementary geometries are essential to improve knowledge of physical structures, thermochemistry, and impact on convection. Here, we present a new automated approach utilizing machine learning to analyze large seismic data sets, and derive high‐resolution maps of transition zone discontinuity properties. Seismic measurements from ScSScS precursors are integrated with mineralogical modeling to constrain thermochemistry of the western Pacific subduction zone. Our models map recent subduction patterns through the transition zone, indicating stagnation of slabs and accumulation of basalt at its base, and interaction between stagnant slabs and plumes. These results suggest that the thermochemical properties of upper mantle discontinuities can provide high‐resolution images of mantle circulation patterns. Plain Language Summary: Earth's upper mantle displays several discontinuous jumps in its physical properties, which result from changes in its mineral structure as pressure and temperature increase with depth. The major transitions near to 410 and 660 km depth are associated with physical changes that have significant influence on the flow of hot upwelling plumes and cold downgoing slabs. The depth and strength of the discontinuities depend on the local temperature and composition, and therefore constraining these properties can help to track mantle circulation patterns and better understand convection behavior. Global seismic data sets are highly uneven in spatial coverage, and therefore must be supplemented by data sets with different spatial sensitivity. Here, we present an automated approach based on machine learning to analyze seismic phases with such complementary geometry, and apply these techniques to investigate subduction zones beneath the western Pacific. We incorporate high‐resolution observations of the discontinuities with modeling from mineral physics, producing new models of temperature and composition in this region. The models track recent convection patterns through the transition zone, indicating ponding of slabs and plumes. These results suggest that the temperature and composition of the transition zone can be used to provide detailed maps of mantle circulation. Key Points: New data sets of ScSScS precursors beneath the western Pacific subduction zones are compiled and analyzed with machine learning methodsHigh‐resolution measurements of transition zone discontinuities and mineralogical modeling provide detailed maps of thermochemistryThermochemical models track recent mantle circulation patterns, indicating slab stagnation, basalt accumulation, and interaction with plumes [ABSTRACT FROM AUTHOR]

Late Quaternary crustal uplift is well recognized in northeast Sicily, southern Italy, a region also prone to damaging earthquakes such as the 1908 "Messina" earthquake (Mw 7.1), the deadliest seismic event reported within the Italian Earthquake Catalogue. Yet it is still understudied if, within the Milazzo Peninsula, crustal uplift rates are varying spatially and temporally and whether they may be either influenced by (i) local upper‐plate faulting activity or (ii) deep geodynamic processes. To investigate the long‐term crustal vertical movements in northeast Sicily, we have mapped a flight of Middle‐Late Pleistocene marine terraces within the Milazzo Peninsula and in its southern area and refined their chronology, using a synchronous correlation approach driven by published age controls. This has allowed a new calculation of the associated crustal uplift rates, along a north–south oriented coastal‐parallel transect within the investigated area. Our results show a decreasing uplift rate from south to north across the Milazzo Peninsula and beyond, and that the associated rates of uplift have been constant through the Late Quaternary. This spatially varying yet temporally constant vertical deformation helps to constrain the amount of uplift, allowing us to explore which is the driving mechanism(s), proposing a few related scenarios. We discuss our results in terms of tectonic implications and emphasize the importance of using appropriate approaches, as such applying a synchronous correlation method, to refine chronologies of undated palaeoshorelines when used for tectonic investigations. [ABSTRACT FROM AUTHOR]

The outcrop and microscale structural constraints on metamorphosed fragments of Carpathian-Balkan exotic north Gondwanan continental crust show sequential recurrent peripheral subduction processes which produced a series of collisional orogens: (i) Variscan suturing of ‘Median Dacides’ (western Danubian/Moesian realm), and (ii) post-dating polystage Alpine overprinting. The ‘Median Dacides’ comprise the two gneiss-bearing amphibolite-facies, Serbo-Macedonian and Getic/Kučaj basements, embedded into Southern Carpathians (Romania) and Carpathian-Balkans (Serbia, North Macedonia, Bulgaria). To unravel polyphase deformation processes, we have incorporated the data available on Neoproterozoic-Lower Palaeozoic protoliths and tectonometamorphic events, coupling these with new extensive structural field-based analysis. The deformation patterns expose polystage deformation history (D1-2), fashioned by the youngest Alpine overprinting (D3-4). The structural data and protolith analyses suggest a Lower Palaeozoic Cadomian-to-Cenerian geodynamic linkage between the two gneissic basements. Notably, the pre-Variscan anatexis, migmatitization, metamorphism (D1-1), and the formation of Cenerian (axial planar) foliation (D1-2) are precursors of the tight isocline Variscan folds (D2-1). Progressive deformation of the initial Variscan structural fabric (metre-scale folds) produced complete transposition (D2-2) with scarcely preserved metre-scale folds. The successor Alpine shortening (D3) (re)activated the existing remnants of Variscan axial plane cleavages (or overlapped foliation-to-cleavage planes), further producing schistosity and folding pattern preserved due to the partial transposition. [ABSTRACT FROM AUTHOR]

This study identifies the reasons for geodynamics variability of the coastal system within two cliff-shore sections of the southern Baltic Sea (SBS). The comparative analysis included distinct moraines and their foregrounds near the open sea (S1) and within the Gulf of Gdańsk (S2). Short-term trends indicate a direct link between landslide occurrence and increased cliff retreat. Long-term (total) values were obtained by developing the 4F MODEL for large-scale applications, based on the analysis of remote sensing and hydroacoustic data (to determine the extent of shore platforms), the modelling of higher-order polynomial functions describing their extent, followed by the integral calculus of the indicated functions within the open-source Desmos environment. The retreat dynamics for individual landslides (S1) was an order of magnitude higher (m/yr) than the average for the whole cliff section (0.17 ± 0.008 m/yr), which correlates well with medium- and long-term development tendencies and recession dynamics, revealed by the numerical modelling method, since approximately 8 ka b2k, years before 2000 CE (at S1 = 0.17 ± 0.020 m/yr, at S2 = 0.11 ± 0.005 m/yr). While the approach described in this paper can reveal, project, and simulate the dynamics of past and future trends within other cliffed coasts shaped in tideless conditions, it also proves stable moraine erosional responses to sea-level rise since the Mid-Holocene. [ABSTRACT FROM AUTHOR]

The Ecuadorian arc is composed of an unusually high number of volcanoes, organized as along-arc alignments and across-arc clusters, in a relatively small area. Although several geochronological studies have been carried out in the last three decades, the eruptive history of the central zone of the arc remains poorly documented, preventing analysis of the initiation of volcanism of the whole arc. In this study, we present new K–Ar ages obtained from this central area, referred to as the Quito segment. These results were then incorporated into an updated comprehensive geochronological database of about 250 ages, allowing us to describe, at the arc scale, the spatial and temporal evolution of Quaternary volcanism in Ecuador. About eighty Quaternary volcanoes have been identified in the Ecuadorian Andes, 45 of which have been radioisotopically dated and/or identified as active or potentially active. The volcanic arc developed in three stages, characterized by an increase in the total number of active volcanoes. During the oldest Plio-Early Pleistocene stage, documented volcanic activity was mostly concentrated in the Eastern Cordillera of the Quito segment, with minor effusive eruptions in the southern Back-Arc. Since ~ 1.4 Ma, activity has spread to the surroundings of the Quito segment, and new edifices also appeared in the Western Cordillera and the Inter-Andean Valley. Towards the end of this intermediate stage (i.e., ~ 800 ka), volcanism occurred in isolated areas north and south of the Inter-Andean Valley. Finally, the late and current has been characterized by a remarkable increase in volcanic activity since ~ 600 ka. About 50 volcanoes were active during this stage. The spatial distribution of the Ecuadorian arc volcanism seems to be guided by deep mechanisms (i.e., slab geometry and age, amount and composition (fluids and melts) of slab input, mantle heterogeneities) and old crustal tectonic structures of the Western Cordillera, while neotectonics seems to influence the development of stratovolcanoes. In addition, we note that the spatial and temporal evolution of volcanism highlights the influence of the Carnegie Ridge and the young Nazca crust on the thermal regime of the subduction system, which in turn increases of volcanic activity in Ecuador. [ABSTRACT FROM AUTHOR]

The morphology of the seafloor of the Madagascar Basin from Mauritius Island to the Southwest Indian Ridge (SWIR) is represented by a ridge-echeloned relief of the spreading basement. The azimuth of the relief differs by ~90° for the basin north of the SWIR and its wedge-shaped sublatitudinal rift system, separated by an abyssal escarpment. A genetic definition of this seafloor relief shape is given. This shape is formed when the ancient basement breaks up and accretion of the crust orthogonal to the azimuth, which existed before the rupture, begins. The formation of a wedge in the eastern part of the SWIR began about 41 Ma ago and is manifested by higher (±1100 m) amplitudes of relief variations than at the basement before the rupture (±250 m). The change in morphology is also associated with the change in the spreading azimuth of the lithospheric block by about 24° north of the SWIR, which opened up a new space for accretion. The morphology of the relief in the wedge and beyond shows the relationship of its parameters with slowdown in the spreading rate by almost three times when the kinematics of the plates have changed. The high-amplitude ridge-echeloned relief in the ultraslow segment of the SWIR with signs of nontransform displacement is combined with the maxima and minima of Bouguer anomalies. According to the published data, serpentized peridotites and basalts are obtained in the localization of the anomalies. These rocks indicate the presence of detachments with the exposure of ultramafic rocks and minimal magmatic output. Bouguer anomalies along the regional profile perfectly reflect deep density inhomogeneties. For intraplate volcanic edifices, they have a much greater deconsolidation in the upper mantle than near the active interplate boundary of the SWIR. According to the seismic tomography data, the absence of a deep upwelling under the newly formed SWIR segment and the presence of a "cold" gap in the "hot" lenses of the mantle indicates the action of tangential forces in the lithosphere that are not associated with general mantle convection. The formation of the new orthogonal rift system with ultraslow rates is an adaptation to variations in the kinematics parameters of the adjacent lithospheric plates. [ABSTRACT FROM AUTHOR]

The issues in geodynamic research in Northern Eurasia over the past three decades with emphasis on the use of space technologies in geodesy and geodynamics are presented. The main focus is on the GNSS system as the most widespread and effective tool for geodynamic research due to the compactness and relative ease of installation of ground-based tracking equipment, as well as the possibility of its autonomous operation. The importance of precise GNSS positioning for monitoring small-scale geodynamic displacements of the Earth's surface, which requires millimeter-scale measurement accuracy, is emphasized. The issues of development of a precise reference frame for geodynamics and maintaining its long-term consistency based on the International Terrestrial Reference Frame (ITRF) are considered, as well as the problems and prospects of precise satellite geodetic measurements and geodynamic research in the context of the current reduction in interaction with international geodetic data centers. To solve the problems that have arisen, ways are proposed based on arranging a subcontinental-scale system for equalization of raw GNSS measurements. The capabilities of the GNSS network used for solving problems of geodesy and geodynamics are demonstrated by the example of the analysis of the tectonic rigidity of cratons of Northern Eurasia and the impact of motion of adjacent tectonic plates and variations of these motions in the past geological eras on the contemporary geodynamic setting of these cratons. [ABSTRACT FROM AUTHOR]

The Pannonian-Carpathian-Alpine Seismic Experiment (PACASE) is a collaborative project based on a large, passive seismic network comprising 214 temporary stations. Among the primary aims are the imaging of the Earth's crustal, lithospheric and upper mantle structure, including joint inversions; monitoring and mapping of seismic activity; and interpretation of the data from seismotectonic and geodynamic perspectives. The base of the cooperation is a high-quality, broadband seismic network covering the very centre of Europe: the Eastern Alpine and Western Carpathian Mountain ranges, the Bohemian Massif, and the sedimentary Molasse and Pannonian Basins. In this overview, we focus on the implementation and achieved field goals of PACASE, such as seismic station configuration, general network organization, data availability and access to the dataset. With selected seismological examples, we demonstrate the good usability of the records of earthquake detection, and a first publication attests to the structural imaging capability of the PACASE data. We assess the background noise level at various stations and its variations in time and space. Our aim is to collect all practical information relevant to serve as a long-term reference for the PACASE. [ABSTRACT FROM AUTHOR]

The spatiotemporal interaction of large‐ and regional‐scale upper mantle forces can prevail in collisional settings. To better understand the role of these forces on post‐subduction tectonics, we focus on mantle dynamics in the East Anatolian Plateau, a well‐documented segment of the Arabian‐Eurasian continental collision zone. Specifically, we analyze multiple forces in the upper mantle, which have not been considered in previous studies in this region. To this end, we use a state‐of‐the‐art 3D instantaneous geodynamic model to quantify the dynamics of thermally defined upper mantle structures derived from seismic tomography data. Results reveal a prominent SW‐NE‐oriented mantle flow from the Arabian foreland to the Greater Caucasus–a plumelet–through a lithospheric channel under the East Anatolian Plateau. This plumelet induces localized dynamic topography (∼500 m) around the extensional Lake Van province, favoring NE‐directed compression and westward escape of the Anatolian plate. We suggest that the Lake Van region is an active magma‐rich intraplate rift in the Africa‐Arabia‐Anatolian plume‐rift system. The rift zone was probably initiated by Neotethyan subduction‐related forces and has been reactivated and/or sustained by the plumelet‐induced convective support. Our findings are consistent with numerous observations, including the recent low‐ultralow seismic velocities with a SW‐NE splitting anisotropy pattern, geochemical and petrological studies, and local kinematics showing upper mantle‐induced extensional tectonics in the collisional region. Plain Language Summary: Our goal is to better understand the active deformations of post‐subduction tectonics. To this end, we ran a 3D thermomechanical model of the East Anatolian Plateau, one of the most intriguing segments of the Arabian‐Eurasian continental collision zone. The model integrates seismically defined upper mantle structures and uses an open‐source code (ASPECT). Results reveal the significant role of large‐ and regional‐scale upper mantle forces in the study region. At long wavelengths, we find SW‐NE‐oriented mantle flow and associated dynamic topography. We interpret that such flow—a plumelet (regional upper‐mantle plume migration with neither a significant tail extending to the lower mantle nor a mushroom head reaching the hot spots on the surface)—is linked to the large‐scale mantle flow from the Arabian plate to the Greater Caucasus. At short wavelengths, we find localized dynamic topography and high stress and strain anomalies in the Lake Van zone. We argue that the plumelet, which became more forceful after the removal of the subducted Neotethyan slab, may have generated mantle tractions that contribute to magma‐rich‐intraplate rifting in the Lake Van region. Our results are in good agreement with local kinematics, low‐speed seismic velocities with SW‐NE anisotropy patterns, and geochemical‐petrological studies. Key Points: We present the 3D numerical model and observations related to the Africa‐Arabia‐Anatolian plume‐rift systemOur thermomechanical model provides new insight into the magma‐rich intraplate active rifting in collisional settingsIntegrated analyses from the 3D geodynamic model and observations reveal a SW‐NE‐oriented plumelet and its regional implications [ABSTRACT FROM AUTHOR]

Megathrusts at convergent plate boundaries generate the largest and some of the most hazardous earthquakes on Earth. However, their physical properties, including those influencing fault slip accumulation and release and earthquake‐related surface displacements, are still poorly constrained at critical depths. Here, we combine seismic imaging and geodetic modeling to investigate the structure and mechanical behavior of the Main Himalayan Thrust fault (MHT) in the center of the 2015 Mw 7.8 Gorkha rupture in Nepal. Our results from two independent observations consistently suggest the presence of a channel associated with the MHT with high compliance (shear modulus as low as ∼4 GPa) and strain anisotropy (stiffer in the vertical orientation than in the horizontal), likely arising from a weak subducting layer with north‐dipping foliation. Such mechanical heterogeneity significantly influences the quantification of short‐term fault kinematics and associated earthquake potential, with implications on across‐scale dynamics of plate boundaries in Himalaya and elsewhere. Plain Language Summary: The Main Himalayan Thrust fault marks the boundary where the Indian continent slides beneath the Eurasian plate, causing earthquakes like the 2015 magnitude 7.8 event in Nepal. Subsurface images constructed using seismic waves suggest a weak layer surrounding the fault. However, we show that the seismic signature of this layer changes depending on the direction in which the seismic waves travel through it. We compare this information on the subsurface structure to insights from static surface motions during the earthquake. We find that the fit to the motion is poor when we assume the subsurface rock around the fault has the same strength in both horizontal and vertical orientations. The fit improves when we assume the near‐fault rock is stronger under vertical compression than under horizontal compression. This assumption also helps explain the images constructed using seismic waves. We suggest that a strong oriented rock fabric develops in a channel around the plate boundary. The presence of this fabric may have influenced our estimates of fault slip before, during and after great earthquakes. Accurately describing this behavior is crucial for understanding the earthquake potential of plate boundary faults. Key Points: Seismic imaging suggests a Main Himalayan Thrust‐associated low‐velocity channel with north‐dipping anisotropic foliationModeling of InSAR and GNSS data together suggests a weak channel with anisotropic rigidity whose orientation matches seismic constraintsThe weak anisotropic plate boundary may be related to S‐C fabrics and influence the margin geodynamics on different time scales [ABSTRACT FROM AUTHOR]

Understanding the external and internal geodynamical processes shaping the Earth is challenging. Physical, chemical, and biological processes form the ground surface over time. Erosion, weathering, transporting, and sedimentation are the natural processes that shape landscapes. However, the continuous interactions of external geodynamic drivers, such as water, wind, and biota, play vital roles in shaping the Earth's surface. These complex and interconnected processes impact the landscape and environment, making it essential to comprehend them to predict evolution, variability, and changes. This Topical Collection (TC) is a comprehensive set of over 54 articles (to date, it has over 16,500 accesses and 119 citations) focused on Earth's processes and environment in a changing world. It was grounded in paying tribute to the legacy of the outstanding Spanish geomorphologist, geographer, and honorific Professor Augusto Pérez-Alberti, whose thoughtful contributions have significantly advanced the understanding of earth processes, particularly glacial and periglacial processes, sedimentary dynamics, hydromorphology, and coastal geomorphology. Understanding the geodynamics of the processes that shape Earth systems is critical to protecting and preserving ecosystems, landscapes, natural resources, and communities' well-being. [ABSTRACT FROM AUTHOR]

The study examines the specific features of the structure and composition of strata of the Tyushevskaya basin of Eastern Kamchatka, which formed at the site of the Vetlovsky basin, which is marginal marine in nature. This structure probably began to form in the Late Eocene–Oligocene. A scheme for its evolution is proposed. In the modern structure, sediments of the Tyushevskaya basin overlie the material complexes and structures of various terranes and participate in the accretionary structure of the region. Sedimentary formations are predominantly facies-variable coarse coastal-marine and/or deltaic sediments, which change upsection to deeper-water flysch formations. Oil-bearing manifestations are associated with these complexes. [ABSTRACT FROM AUTHOR]

The doubly vergent orogen in Taiwan is a relatively young and active arc-continent collision caused by the convergence of Eurasian and Philippine Sea Plates occurring along a complicated seismogenic plate boundary. This study aims to investigate the evolutionary and tectonic features of the retro-wedge, a region contributing to the uplifting and shortening of the Taiwan orogen. Through the utilization of seismic tomographic image and relocated seismicity, we identify three potential seismogenic structures along the convergent plate boundary: the Longitudinal Valley Fault, the Ludao–Lanyu Fault, and the Central Range Fault. A significant discovery in our investigation is a west-dipping backthrust of the Central Range Fault, extending from the north Hualien city to the southeastern offshore at a distance of 300 km. The fault is responsible for the formation of a crustal-scale pop-up structure, contributing to the development of a double vergent orogenic wedge in the retro-wedge. The genesis of the basement-involved backthrust is attributed to the indentation of the exhumed forearc mantle wedge and remnant forearc crust into the Backbone Range during collision. Consequently, the plate boundary exhibits two opposite vergent thrust systems of the Longitudinal Valley Fault–Ludao–Lanyu Fault and Central Range Fault, which evolved during different stages of collision-incipient and mature following the closure of the forearc basin of the North Luzon Trough and Longitudinal Valley, respectively. These findings contribute novel insights into the tectonic framework of the convergent zone and provide valuable constraints for geodynamic models of arc-continent collision. [ABSTRACT FROM AUTHOR]

The St. Leonhard granulite massif in Lower Austria, dominantly formed by kyanite-bearing felsic granulite, encloses countless up to 5 cm sized mantle xenoliths of garnet clinopyroxenite and peridotite. The mineralogical, textural and chemical consequences of a mutual metasomatic interaction at the contact between these xenoliths and the host orthopyroxene-bearing felsic granulite are described. Movement of Mg, Al and, especially, Ca from the garnet clinopyroxenite to the granulite and migration of K and Na in the opposite direction, caused the breakdown of clinopyroxene and formation of orthopyroxene–plagioclase symplectite coronae at the expense of the garnet clinopyroxenite xenoliths. Around the peridotite xenoliths, monomineralic orthopyroxene coronae have developed due to the supply of Si from the host granulite. The P–T conditions of this interaction were established to 900°C to 1000°C and 1.0 to 1.2 GPa by thermodynamic modelling. The duration of coronae growth was constrained to 13 to 532 ka based on modelling of Fe–Mg interdiffusion underlying secondary compositional zoning of garnet from the garnet clinopyroxenite xenolith extending to the coronae. The most significant change in the host granulite was caused by the supply of Ca from the garnet clinopyroxenite xenolith, which led to the breakdown of the Al2SiO5 phase—probably kyanite—and stabilization of orthopyroxene. K-feldspar-poor haloes surrounding mantle xenoliths formed due to the depletion of K in the granulite adjacent to the garnet clinopyroxenite. The observed origin of felsic–intermediate orthopyroxene-bearing granulite by transformation of felsic kyanite-bearing granulite through the metasomatic interaction with mantle xenoliths implies that the deep crustal chemical exchange between mantle- and crust-derived lithologies may have an important consequences on composition, thermal structure and geodynamic evolution of orogenic lower crust especially in hot collisional orogens, such as the European Variscides. [ABSTRACT FROM AUTHOR]

The Lengjimanda plate is situated in the middle section of the Da Hinggan mountains, in the eastern section of the Tianshan Xingmeng orogenic belt. To determine the formation age of the volcanic rocks in the Longjiang formation in this area, to explore their origin and tectonic background, and to reconstruct the geodynamic evolution of the region, this study conducted petrological, zircon U–Pb geochronological, geochemical, and isotopic analyses of the volcanic rocks in the Longjiang formation. The Longjiang formation's volcanic rocks are primarily composed of trachyandesite, trachyte trachydacite, and andesite, which are intermediate basic volcanic rocks. They are enriched in large-ion lithophile elements, are depleted in high-field-strength elements, are significantly fractionated between light and heavy rare earth elements, and exhibit a moderate negative Eu anomaly in most samples. The results of the LA–ICP–MS zircon U–Pb dating indicate that the volcanic rocks in this group were formed in the Early Cretaceous period at 129.1 ± 0.82 Ma. The zircon εHf(t) ranges from +1.13 to +43.77, the tDM2 ranges from +655 to +1427 Ma, the initial Sr ratio (87Sr/86Sr)i ranges from 0.7030 to 0.7036, and the εNd(t) ranges from +2.1 to +6.6. Based on the geochemical compositions and isotopic characteristics of the rocks, the initial magma of the volcanic rocks in the Longjiang formation originated from the partial melting of basaltic crustal materials, with a source material inferred to be depleted mantle-derived young crustal. These rocks were formed in a superimposed post-collisional and continental arc environment, possibly associated with the Mongol-Okhotsk Ocean closure and the oblique subduction of the Pacific plate. This study addresses a research gap regarding the volcanic rocks of the Longjiang formation in this area. Its findings can be applied to exploration and prospecting in the region. [ABSTRACT FROM AUTHOR]

The accretion of future allochthonous terranes (e.g., microcontinents or oceanic plateaus) onto the southern margin of Asia occurred repeatedly during the evolution and closure of the Tethyan oceanic realm, but the specific geodynamic processes of this protracted convergence, successive accretion, and subduction zone initiation remain largely unknown. Here, we use numerical models to better understand the dynamics that govern multiple terrane accretions and the polarity of new subduction zone initiation. Our results show that the sediments surrounding the future terranes and the structural complexity of the overriding plate are important factors that affect accretion of multiple plates and guide subduction polarity. Wide (=400 km) and buoyant terranes with sediments behind them and fast continental plate motions are favorable for multiple unidirectional subduction zone jumps, which are also referred to as subduction zone transference, and successive terrane-accretion events. The jumping times (~3-20 + m.y.) are mainly determined by the convergence rates and rheology of the overriding complex plate with preceding terrane collisions, which increase with slower convergence rates and/or a greater number of preceding terrane collisions. Our work provides new insights into the key geodynamic conditions governing multiple subduction zone jumps induced by successive accretion and discusses Tethyan evolution at a macro level. More than 50 m.y. after India-Asia collision, subduction has yet to initiate along the southern Indian plate, which may be the joint result of slower plate convergence and partitioned deformation across southern Asia. [ABSTRACT FROM AUTHOR]

Reconstructing the thermo-chemical evolution of Earth's mantle and its diverse surface manifestations is a widely recognised grand challenge for the geosciences. It requires the creation of a digital twin: a digital representation of Earth's mantle across space and time that is compatible with available observational constraints on the mantle's structure, dynamics and evolution. This has led geodynamicists to explore adjoint-based approaches that reformulate mantle convection modelling as an inverse problem, in which unknown model parameters can be optimised to fit available observational data. Whilst there has been a notable increase in the use of adjoint-based methods in geodynamics, the theoretical and practical challenges of deriving, implementing and validating adjoint systems for large-scale, non-linear, time-dependent problems, such as global mantle flow, has hindered their broader use. Here, we present the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT), an advanced computational modelling framework that overcomes these challenges for coupled, non-linear, time-dependent systems by integrating three main components: (i) Firedrake, an automated system for the solution of partial differential equations using the finite-element method; (ii) Dolfin-Adjoint, which automatically generates discrete adjoint models in a form compatible with Firedrake; and (iii) the Rapid Optimisation Library, ROL, an efficient large-scale optimisation toolkit; G-ADOPT enables the application of adjoint methods across geophysical continua, showcased herein for geodynamics. Through two sets of synthetic experiments, we demonstrate the application of this framework to the initial condition problem of mantle convection, in both square and annular geometries, for both isoviscous and non-linear rheologies. We confirm the validity of the gradient computations underpinning the adjoint approach, for all cases, through second-order Taylor remainder convergence tests and subsequently demonstrate excellent recovery of the unknown initial conditions. Moreover, we show that the framework achieves theoretical computational efficiency. Taken together, this confirms the suitability of G-ADOPT for reconstructing the evolution of Earth's mantle in space and time. The framework overcomes the significant theoretical and practical challenges of generating adjoint models and will allow the community to move from idealised forward models to data-driven simulations that rigorously account for observational constraints and their uncertainties using an inverse approach. [ABSTRACT FROM AUTHOR]

This study investigates the variations in stress, strain, and deformation of the Earth's crust in Iran arising from tectonic movements and seismic activities. We employed the Kostrov and Molnar methods to quantify these parameters, focusing on the influence of different zoning techniques on the estimations. Analyzing data from 637 earthquakes (moment magnitudes > 5.5) spanning 1909 to 2016, we determined the directions of maximum pressure, tension, and seismic strain through two primary approaches: comprehensive zoning and individual earthquake analysis. Additionally, we assess horizontal shortening and vertical crustal adjustments. Our methodology involves three distinct strategies: individual earthquake analysis, 1° x 1° zoning, and tectonic zoning. The findings demonstrate that the choice of zoning method significantly affects the direction and magnitude of seismic strain estimations. Although both methods identified significant deformations in the Dasht Bayaz and Qaen regions of Eastern Iran, differences between the Kostrov and Molnar methods in estimating seismic strain are observed. The high Zagros region shows signs of crustal thickening, whereas the Zagros foreland exhibits crustal thinning. Intriguingly, Eastern Alborz indicates uplift, and Western Alborz suggests subsidence, offering an alternative view to the conventional tectonic understanding of the Alborz range. These results highlight the critical role of zoning in stress analyses and the disparities between widely used estimation techniques. They underscore the necessity of careful method selection and interpretation in geodynamic studies, particularly in seismically active regions like Iran. [ABSTRACT FROM AUTHOR]

The effect of mantle plumes is secondary to that of subducting slabs for modern plate tectonics when considering plate driving forces. However, the impact of plumes on tectonics and planetary surface evolution may nonetheless have been significant. We use numerical mantle convection models in a 3‐D spherical chunk geometry with damage rheology to study some of the dynamics of plume‐slab interactions. Substantiating our earlier 2‐D results, we observe a range of interaction scenarios, and that the plume‐driven subduction terminations we had identified earlier persist in more realistic convective flow. We analyze the dynamics of plume affected subduction, including in terms of their geometry, frequency, and the overall effect of plumes on surface dynamics as a function of the fraction of internal to bottom heating. Some versions of such plume‐slab interplay may be relevant for geologic events, for example, for the inferred ∼183 Ma Karoo large igneous province formation and associated slab disruption. More recent examples may include the impingement of the Afar plume underneath Africa leading to disruption of the Hellenic slab, and the current complex structure imaged for the subduction of the Nazca plate under South America. Our results imply that plumes may play a significant role not just in kick‐starting plate tectonics, but also in major modifications of slab‐driven plate motions, including for the present‐day mantle. Plain Language Summary: Subduction of cold, strong lithospheric slabs is the main plate driving force within mantle convection. However, hot upwellings, mantle plumes, may have a greater role in modulating plate motions and slab trajectories than previously thought. We use 3‐D numerical convection models that account for the weakening of rocks due to the accumulation of deformation to understand the effect that mantle plumes can have on subduction zones. We show that plumes can terminate subduction in a range of circumstances. We also test the effect of the amount of internal heating compared to heat from the core which is the major convective control on the importance of plumes. We discuss cases where these plume‐slab terminations may have occurred on Earth, in the geological past, and for the present day through plate reconstructions and consideration of seismic tomography. Key Points: Mantle plumes can terminate subduction in 3‐D, damage rheology convectionPlumes can modulate subducting slabs and plate tectonic regimesPlume‐slab interactions are plausible contributions to the Karoo‐Gondwana event [ABSTRACT FROM AUTHOR]

Abstract The relationship between the lithosphere and the mantle during the supercontinent cycle is complex and poorly constrained. The processes which drive dispersal are often simplified to two end members: slab pull and plume push. We aim to explore how lithosphere thickness and viscosity during supercontinent assembly may affect the interaction of deep mantle structures throughout the supercontinent cycle. We consider supercontinental lithosphere structure as one of many potential processes which may affect the evolution of upwellings and downwellings and therefore systematically vary the properties of continental and cratonic lithosphere, respectively within our 3D spherical simulations. The viscosity and thickness of the lithosphere alters the dip and trajectory of downwelling material beneath the supercontinent as it assembles. Focusing on Pangea, we observe that plumes evolve and are swept beneath the center of the supercontinent by circum‐continental subduction. The proximity of these upwelling and downwelling structures beneath the supercontinent interior varies with lithosphere thickness and viscosity. Where slabs impinge on the top of an evolving plume head (when continental and cratonic lithosphere are thick and viscous in our simulations), the cold slabs can reduce the magnitude of an evolving plume. Conversely, when the continental lithosphere is thin and weak in our simulations, slab dips shallow in the upper mantle and descend adjacent to the evolving plume, sweeping it laterally near the core‐mantle boundary. These contrasting evolutions alter the magnitude of the thermal anomaly and the degree to which the plume can thin the lithosphere prior to breakup.

The lithologic-facial, mineralogical, petrographic, and lithogeochemical studies of Visean terrigenous sediments in the borehole section at the Bashkirian arch were carried out to clarify the sources of matter and sedimentation conditions. Terrigenous rocks of the Radayevsky and Bobrikovsky horizons are characterized by predominantly good sorting and pelletization of clastic material. A significant distance from the source of drifting is assumed. Terrigenous rocks of these horizons are sediments of the first and second sedimentation cycles. The rocks of the Tula horizon are characterized by average sorting and pelletization, which indicates the proximity of the drift source to the sedimentation basin. They are rocks of the first sedimentation cycle. The source of clastic material for the Radayevsky and Tula horizons was found to be rocks of acidic composition. For the beaver horizon, the acidic and the main source of drift was established. It is assumed that sedimentation of rocks occurred in coastal-marine conditions on the passive continental margin, with the inflow of clastic material from the inner parts of the East European Platform, due to overwashing of the early accumulated terrigenous rocks of the Devonian and Proterozoic, as well as destruction of the basement ledges, which were activated in the Early Visean time during the manifestation of folding. The presence of basic rocks in the Bobrikovsky horizon may indicate that the material came from the orogen.

The article describes the geological structure of the Sokolovsk and Krasnokamensk massifs located in the central part of the Western subzone of the ChelyabinskAdamovka zone of the Southern Urals. They are of Lower Carboniferous age and break through the volcanogenicsedimentary deposits of the Krasnokamensk (D3kr) and Bulatovo (S1-D1bl) strata. It was found that these intrusions belong to the gabbro-syenite complex and are composed of gabbroids (phase I) and syenites, quartz monzonites, less often monzodiorites (phase II). The rocks of the second phase predominate (90–95%). Gabbros belong to the normal alkaline series of the sodium series and are close to tholeiitic mafic rocks, the formation of which is associated with riftogenic structures; syenites correspond to moderately alkaline series with K-Na type of alkalinity. It has been proved that in terms of their petrographic, petrochemical, geochemical, and metallogenic features (content of TiO2 , K2 O, Na2 O, Rb, Sr, distribution of REE, the presence of skarn-magnetic mineralization), the rocks of the massifs under consideration undoubtedly belong to the gabbro-granite formation. Crystallization of the Sokolovsk and Krasnokamensk intrusions occurred at a temperature of 880–930 °С in the mesoabyssal zone at a depth of about 7–8 km (P = 2.2–2.4 kbar). At the postmagmatic stage, the transformation parameters of the initially igneous rocks were, respectively, T = 730–770 °C, P = 4.0–4.2 kbar. The fact that these massifs belong to the gabbro-granite formation makes it possible to include them, together with Bolshakovsk, Klyuchevsky, Kurtmaksky and Kambulatovo, into the Chelyabinsk-Adamovka segment of the South Ural Early Carboniferous rift system.

The Larino granite-gneiss dome is located on the border of the Aramil-Sukhtelya and Magnitogorsk megazones and is a two-headed anticlinal structure, the nuclear parts of which are composed of granitoids of the Pervomai and Larino massifs, and their framing – apovolcanic amphibolites, garnetmica-tins, garnet-amphislans siliceous-carbonaceous schists of the Bulatovo Series (S1 –D1 bl). A series of concentric highgradient zones of metamorphism are observed from granitoids to shales. Mineral parageneses of the amphibolite facies at a distance of several kilometers are replaced by associations of epidote-amphibolite and greenschist facies.It has been proven that granitoids belong to the granitemigmatite formation, are close to trondhjemites of the inner parts of the continents (granites, leucogranites) and continental margins (gneisized, migmatized granitoids) and were formed in intraplate and collisional geodynamic settings.Crystallization of granites took place at temperatures of 780–840°С and a pressure of 2.1–3.7 kbar, plagiogranites – 880–940°С and 2.9–3.3 kbar, which corresponds to the abyssal depth zone (7–11 km). For granitoids formed in the process of metasomatic granitization (gneissized and migmatized rocks), formation temperatures are noticeably lower – 650– 680°С, and the pressure is higher – 6.6–7.0 kbar (almandine amphibolite facies).

It has recently been suggested that deformed crustal plateaus on Venus may be composed of felsic (silica-rich) rocks, possibly supporting the idea of an ancient ocean there. However, these plateaus have a tendency to collapse owing to flow of the viscous lower crust. Felsic minerals, especially water-bearing ones, are much weaker and thus lead to more rapid collapse, than more mafic minerals. We model plateau topographic evolution using a non-Newtonian viscous relaxation code. Despite uncertainties in the likely crustal thickness and surface heat flux, we find that quartz-dominated rheologies relax too rapidly to be plausible plateau-forming material. For plateaus dominated by a dry anorthite rheology, survival is possible only if the background crustal thickness is less than 29 km, unless the heat flux on Venus is less than the radiogenic lower bound of 34 [Formula: see text]. Future spacecraft determinations of plateau crustal thickness and mineralogy will place firmer constraints on Venus's heat flux.

Central Afar is shaped by the interaction between the Red Sea (RS) and Gulf of Aden (GoA) rifts. While there have been several studies conducted in the region, we know surprisingly little about the mechanism of connection between these two rift branches. Here we use high‐resolution 3D lithospheric scale geodynamic modeling to capture the evolution of linkage between the RS and GoA rifts in central Afar. Our results demonstrate that the two rifts initially overlap and interact across a broad zone of faulting and vertical axis block rotation. However, through time, rift overlap is abandoned in favor of direct linkage which generates a series of localized en‐echelon basins. The present‐day direct linkage between the two rifts is supported by geodetic observations. Our study reconciles previously proposed models for the RS and GoA rift connection by considering spatial and temporal evolution of the rifts. Plain Language Summary: Rifts are places where tectonic plates move away from each other. They normally start as short, isolated features, and then grow and connect together to eventually form oceans. Central Afar in East Africa is a great location to study how these rifts form and grow by connecting with other rifts. In this area, the Red Sea (RS) and Gulf of Aden (GoA) rifts interact, but it is not clear how this happened through time. Some studies suggest that the two rifts form an overlap zone where blocks within the overlap rotate, while others argue that the two rifts directly link and form a continuous rift zone. To resolve this debate, we conducted a high‐resolution computer simulation of the evolution of the RS and GoA rifts in central Afar. We compared our model results with earthquake positions and satellite data that constrain the present‐day motion of the plates. Our results demonstrate that the RS and GoA rifts first overlapped for a few millions of years, and then formed a direct linkage. Our study suggests that both conceptual models can be reconciled when we consider the temporal evolution of the two rifts through geological times. Key Points: Analyzing the spatiotemporal evolution of rifts can address the controversial issue on the connection between propagating riftsWe present results from InSAR and geodynamic models to describe the connection between Red Sea (RS) and Gulf of Aden (GoA) rifts in central AfarThe connection between the two rifts evolves from rift overlap to direct linkage elucidating the observed deformation in the region [ABSTRACT FROM AUTHOR]

The Palaeo- to Neoarchaean Bundelkhand Craton (BkC) in central India has received attention due to its felsic crust evolution. There are two linear patches of relict greenstone belts in the BkC, and the central greenstone belt has been the focus of extensive research for the past two decades. In contrast, the southern greenstone belt has received inadequate attention. At the southern BkC, the E-W Madawara Greenstone Belt is represented by patches of remnant mantle serpentinites and metasedimentary rocks that are tectonically juxtaposed with Archaean basement TTG gneisses and Proterozoic Bijawar Group of rocks. This study highlights key findings from fields, geological maps, petrography, and a large number of whole rock chemical analyses of serpentinites and spinel chemistry to unravel the tectonic evolution story. We identified two serpentinites with contrasting petrological and geochemical properties: spinel peridotite (SP) and talc-tremolite schist (TTS). SP is primarily dunite to harzburgite with relatively high MgO (33 wt%), enriched Yb, and shows strong re-fertilization. TTS, on the other hand, is lherzolitic and less refractory (MgO = 25 wt%). Chemically, these two serpentinites were mantle wedge and subducted peridotites, respectively. The unaltered cores of the chromium spinels represent a fore-arc setting. These findings, in conjunction with prior research, paint a compelling picture of a Neoarchaean (~2.5 Ga) subduction system once present in the southern Bundelkhand Craton. The serpentinites represent relict ophiolites – from a northerly dipping trench. It also explains a Mesoarchaean rift basin system between the two cratonic nuclei of southern Bundelkhand, which amalgamated during the Kenorland Supercontinent formation. [ABSTRACT FROM AUTHOR]

On 28 December 2020, the area of the city of Petrinja was hit by two strong earthquakes of magnitudes 5.0 and 4.7 on the Richter scale, and the following day, 29 December 2020, the same area was hit by an even stronger earthquake of magnitude 6.2. It was one of the two strongest instrumentally recorded earthquakes that hit the territory of the Republic of Croatia in the last hundred years, and the strongest earthquake in the Banovina area after the great earthquake in 1909. Increased seismic activity in this area is caused by two vertical strike–slip faults, Pokupski and Petrinjski. This article aims to determine the displacements of the Earth's crust caused by seismic activity in this area using GNSS measurements and InSAR techniques and comparing their results. Our study showed that horizontal coseismic displacements of 20 cm and more were limited to a radius of 20 km from the epicenter, with a maximum displacement of around half a meter. Considering the original plate tectonic movements of the region and the time elapsed since the previous earthquake of similar magnitude, the geodynamic movements of the Dinarides area are in substantial part sudden displacements associated with earthquakes. [ABSTRACT FROM AUTHOR]

[Display omitted] The Altai orogen is a typical intracontinental orogen in Central Asia that experienced far-field deformation associated with Indian-Eurasian plate convergence. This region is characterized by uplift comparable to that of the Tianshan Mountains but has a distinct strain rate. Half of the Indo-Asia strain is accommodated by the Tianshan Mountains, whereas the Altai Mountains accommodates only 10%. To elucidate how the Altai Mountains produced such a large amount of uplift with only one-fifth of the strain rate of the Tianshan Mountains, we constructed a detailed crustal image of the Altai Mountains based on a new 166.8-km deep seismic reflection profile. The prestack migration images reveal an antiform within the Erqis crust, an ∼10 km Moho offset between the Altai arc and the East Junggar area, and a major south-dipping (30° dip) thrust in the lower crust beneath the Altai Mountains, which is connected to the Moho offset. The south-dipping thrust not only records the southward subduction of the Ob-Zaisan Ocean in the Paleozoic but also controlled the Altai deformation pattern in the Cenozoic with the Erqis antiform. The Erqis antiform prevented the extension of deformation to the Junggar crust. The south-dipping thrust in the lower crust of the Altai area caused extrusion of the lower crust, generating uplift at the surface, thickening of the crust, and steep (∼10 km) Moho deepening in the Altai Mountains. This process significantly widened the deformation zone of the Altai Mountains. These findings provide a new geodynamic model for describing how inherited crustal structure controls intraplate deformation without strong horizontal stress. [ABSTRACT FROM AUTHOR]

The study of the deep structure and tectonics of the Arctic region is relevant not only for solving fundamental problems of modern geodynamics, but also for developing natural resources in the circumpolar regions; it is also of interest from the geopolitical view when determining the boundaries of the marginal seas shelves. To analyze the anomalous magnetic field in the Polar Arctic region, experimental CHAMP satellite data were used, obtained at the last stage of its operation, when the orbit altitude decreased to 280–260 km, which made it possible to obtain geomagnetic parameters with higher spatial resolution. For several sectors of the Polar Arctic, maps of the lithospheric magnetic anomalies field distribution for various scales and degrees of averaging over this area were constructed. The anomalies parameters were analyzed and an explanation was proposed for the geological and physical nature of the anomalies, which are images of the most significant geological–tectonic structures of the North Atlantic Igneous Province and complex of Central Arctic underwater rises. The article discusses the relationships between the discovered features of the lithospheric anomalous magnetic field distribution, and the known geological structures of Amerasia and Eurasia, and tectonic processes that occurred here in the past and still proceed now. The results obtained are of interest for further comprehensive geological and geophysical studies and construction of substantiated models of the Arctic region lithosphere evolution. [ABSTRACT FROM AUTHOR]

We developed an enhanced Kalman‐based approach to quantify abrupt changes and significant non‐linearity in vertical land motion (VLM) along the coast of Chile and the Antarctic Peninsula using a combination of multi‐mission satellite altimetry (ALT), tide gauge (TG), and GPS data starting from the early 1990s. The data reveal the spatial variability of co‐seismic and post‐seismic subsidence at TGs along the Chilean subduction zone in response to the Mw8.8 Maule 2010, Mw8.1 Iquique 2014, and Mw8.3 Illapel 2015 earthquakes that are not retrievable from the interpolation of sparse GPS observations across space and time. In the Antarctic Peninsula, where continuous GPS data do not commence until ∼1998, the approach provides new insight into the ∼2002 change in VLM at the TGs of +5.3 ± 2.2 mm/yr (Palmer) and +3.5 ± 2.8 mm/yr (Vernadsky) due to the onset of ice‐mass loss following the Larsen‐B Ice Shelf breakup. We used these data to constrain viscoelastic Earth model parameters for the northern Antarctic Peninsula, obtaining a preferred lithosphere thickness of 115 km and upper mantle viscosity of 0.9 × 1018 Pa s. Our estimates of regionally‐correlated ALT systematic errors are small, typically between ∼±0.5–2.5 mm/yr over single‐mission time scales. These are consistent with competing orbit differences and the relative errors apparent in ALT crossovers. This study demonstrates that, with careful tuning, the ALT‐TG technique can provide improved temporal and spatial sampling of VLM, yielding new constraints on geodynamic models and assisting sea‐level change studies in otherwise data sparse regions and periods. Plain Language Summary: The difference in sea‐level records from satellite altimeters and coastal tide gauges can reveal the Earth surface's vertical land motion (VLM) and potential errors in either system. Time‐varying changes in the VLM can occur because of phenomena such as earthquakes or glacier melt which changes the mass load on the crust. We developed a flexible data combination framework to use records from multi‐mission altimeters (ALTs), tide gauges (TGs), and GPS sites to allow the estimation of substantial non‐linear VLM that complements the previous estimates which can be sparse in the 1990s especially. We considered the study period since the launch time of TOPEX mission in ∼1992. We used our new approach to investigate the earthquake‐induced deformation at TG locations along the near‐coast subduction zone in Chile that could not be inferred from temporally and spatially sparse GPS records. We also provide insights into the rapid change in VLM at coastal TGs in the Antarctic Peninsula after the Larsen‐B Ice Shelf breakup in ∼2002, where the existing knowledge dates to ∼1998 from only one GPS at Palmer station. These significant insights into present‐day deformation help to fill the knowledge gap from GPS‐inferred records and improve VLM sampling across space and time. More generally, this new approach may assist resolve complex VLM for sea‐level studies globally and could add new constraints to inverse geophysical modeling, especially where GPS data are sparse in space and/or time. Key Points: We developed an advanced Kalman approach to estimate highly non‐linear vertical land motion using altimeter, tide gauge and GPS data, while simultaneously capturing significant mission‐specific systematic errorsWe derived new estimates of pre‐seismic velocity, co‐seismic jumps, and post‐seismic velocity at tide gauges in Chile that add additional constraints on the solid‐Earth response to major earthquakes in the regionWe observed the onset of rapid uplift at tide gauges in the Antarctic Peninsula caused by the 2002 breakup of the Larsen‐B Ice Shelf, filling a historical knowledge gap from GPS records and further constraining modeled viscoelastic deformation [ABSTRACT FROM AUTHOR]