Subduction zones play a key role in the tectonic and chemical evolution of the Earth and are the site of the largest earthquakes and most explosive volcanic eruptions. Subduction zones are diverse, varying in rates, shape of the trench and slab, relative contribution and direction of trench motion versus plate motion, coupling between the two plates, and state of stress of the upper plate.

To understand what controls such diversity, my group and several others have been building a systematic understanding of subduction dynamics, starting from the simplest system of a single subducting plate, free subduction.  Free subduction models illustrate how sensitive the subduction system is to the balance between slab density which drives it, the resistance of the plate to bending at the trench (and base of the transition zone) and drag by the mantle below the unsubducted plate and around the slab. Tectonic reconstructions and seismic tomography show that in response to the extra resistance to sinking encountered at the transition to the lower mantle most slabs retreat and flatten. Such observations constrain the magnitude of slab strength relative to the other forces. Any dynamic models of subduction, even for investigating more complex dynamic settings, need to ensure plate properties yield such an earth-like sinking mode of subduction.

Varying trench shapes can be understood from variations in plate width, which lead to simple C-shaped trenches for small subduction zones or W-shapes for trenches that are long relative to slab bending lengths. Although slab pull is the dominant driver of mantle convection, local (plate-age) dependent slab buoyancy does not have a strong expression in trends of plate and trench velocities, indicating the importance of considering spatially varying plate buoyancy. Models show that buoyant features such as aseismic volcanic ridges can lead to either slab steepening or flattening depending on the background plate buoyancy and strength and position relative to the free-subduction shape of the trench. Together, these factors explain quite a bit of the complexity seen in natural subduction zones. Further influences come from global plate interactions, which limit the motions of upper and lower plates, and mantle flow including upwellings and flow driven by previously subducted slab remnants.

The resulting imbalance between the bending a free slab tries to achieve and the bending it undergoes to adjust to the net forces acting on the system affects how much of the deformation is viscous versus elastic. An initial study showed that a measure of this elasticity (the Deborah number) may correlate with the proportion of larger relative to smaller intraplate earthquakes.  In my talk, I will present a summary of some of these key previous insights into subduction dynamics and natural examples.

How to cite: Goes, S.: Towards understanding the dynamics of subduction zone diversity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10356, https://doi.org/10.5194/egusphere-egu26-10356, 2026.

Earth's mantle drives fundamental processes that shape our planet and directly impact us. Convective flow induces both lateral and vertical motion of the surface, with consequences across timescales. Over geological time, dynamic topography modulates continental flooding, sedimentary basin development, and global sea level. On shorter timescales, glacial isostatic adjustment governs the ongoing response to ice sheet fluctuations, reshaping coastlines and redistributing ocean mass. These vertical motions, coupled with lateral plate displacements, also control the burial and exhumation of rocks, processes central to the genesis of mineral and critical resource deposits. Quantitative models of mantle dynamics are therefore essential not only for understanding Earth's past but for anticipating its future trajectory.

Traditional forward modelling approaches, while physically rigorous, fail to fully exploit the wealth of observational constraints now available, including seismic tomography, geodetic measurements, tectonic reconstructions, and geological indicators of past topography. These data encode invaluable information about mantle structure and rheology that forward models cannot systematically assimilate.

Here I present a framework for constructing Digital Twins of Earth's Mantle, physics-based models systematically optimised against observations using formal inverse methods. Central to this approach is the adjoint method, which enables efficient computation of gradients through complex time-dependent simulations, making large-scale inversions tractable.

I demonstrate this framework across three complementary problems spanning temporal scales. For long-term mantle evolution, I show how seismic tomography and plate reconstructions can be inverted to recover Earth's mantle history in the Cenozoic. Turning to the present day, I illustrate how observations of dynamic topography constrain three-dimensional variations in mantle rheology. Finally, addressing shorter timescales, I consider glacial isostatic adjustment, where the joint reconstruction of ice loading history and mantle viscosity structure emerges from geodetic and geological sea-level data.

Together, these applications establish adjoint-based Digital Twins as powerful tools for synthesis across Earth science disciplines, enabling both retrodiction of past states and predictions that inform sea level projections, coastal vulnerability assessment, and mineral exploration.

How to cite: Ghelichkhan, S.: Digital Twins of Earth's Mantle: Adjoint Inverse Approaches for Reconstructing Mantle Dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19971, https://doi.org/10.5194/egusphere-egu26-19971, 2026.

North-central Chile is a highly seismically active region. While the last megathrust earthquake occurred in 1730, the area has also experienced large events in recent decades, such as the 2015 Illapel earthquake (Mw 8.3), as well as numerous seismic sequences and persistent swarms. Although these phenomena are widespread along the Chilean subduction margin, their dynamics and potential connection to major earthquakes remain poorly understood. 

Within this framework, the ABYSS project has deployed Distributed Acoustic Sensing (DAS) interrogators along offshore telecommunication fiber-optic cables, complemented by temporary and permanent onshore seismic stations. This configuration offers a unique opportunity to monitor and investigate the offshore microseismicity in a region characterized by sparse permanent instrumentation and the absence of previous offshore sensors.

In this study, we develop a workflow to precisely relocate the seismicity recorded by the ABYSS network. We combine the probabilistic, non-linear hypocentral inversion using NonLinLoc with double-difference relocation using HypoDD, incorporating a 3D P- and S-wave velocity model and differential times derived from waveform cross-correlation on both DAS and onshore stations. Through this integrated approach, we identify and analyze clusters of seismicity associated with swarm activity and short-term seismic sequences. In particular, we apply the workflow to episodes such as the Tongoy swarm initiated on 30 December 2024, whose largest event reached Ml 5.3, and the offshore Ovalle sequence that occurred between October and November 2025.

Our goal is to precisely characterize these sequences by improving constraints on the geometry and spatio-temporal evolution, gaining insights into the processes driving this activity, and shedding light on how present-day swarm dynamics may relate to the occurrence of larger earthquakes along the Chilean subduction margin.

How to cite: Peralta, T., Flores, M. C., Rivet, D., Potin, B., Baillet, M., and Ruiz, S.: High-resolution relocation of seismic swarms using offshore DAS and onshore seismic data in north-central Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-887, https://doi.org/10.5194/egusphere-egu26-887, 2026.

Numerical simulations of earthquake cycles provide essential insights into fault mechanics and the physical interpretation of frictional parameters. Here, we utilize a spring-block system governed by rate-and-state friction to systematically compare earthquake cycle behaviors under quasi-dynamic and fully dynamic conditions. Our simulations demonstrate that for both approaches, the static stress drop, dynamic stress drop, and peak stress scale linearly with the logarithm of the loading rate [ln(Vpl/V0)]; however, the scaling coefficients are distinct and are modulated by both frictional parameters and the system stiffness. Specifically, we observe stress overshoot during the coseismic phase in dynamic models, contrasting with the undershoot observed in quasi-dynamic simulations. Additionally, parameter sweeps reveal that stress drops decrease as the stiffness ratio kc/k increases. This study highlights the importance of the inertial term effect in interpreting earthquake cycle behaviors.

How to cite: Chai, L. and Hu, F.: Scaling of Stress Drop with Rate-and-State Frictional Parameters in Spring-Block Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6568, https://doi.org/10.5194/egusphere-egu26-6568, 2026.

Collision and relentless underthrusting of India beneath Eurasia resulted in large-scale deformation of the Indian lithosphere. Anisotropic parameters serve as a good proxies to decipher deformation in such complex orogenic collision zones. In this study, we present anisotropy characteristics of the crust beneath Sikkim Himalaya using harmonic decomposition of P-to-S converted phases identified in P-wave receiver functions (P-RFs). Analysis of azimuthal variation of these phases enabled parameterizing the crustal anisotropic properties, with depth. Initially, 11,087 high quality P-RFs were computed using waveforms of teleseismic earthquakes having magnitude  ≥ 5.5 and signal to noise ratio  ≥ 2.5 within an epicentral distance range of 30° - 100°, recorded at a network of 38 seismic stations deployed in Sikkim Himalaya and the adjoining foreland basin. Analysis of the first three harmonic degrees (i.e. k= 0, 1 and 2) reveals that the upper crustal anisotropy is oriented WSW-ENE to E-W, coinciding well with the trends of crustal microcracks and fractures. The mid to lower crustal anisotropy aligns predominantly with the dipping decollement layer along which the Indian plate is underthrusting Tibet. An orthogonal reorientation is observed within the extent of the Dhubri-Chungthang Fault Zone authenticating its role in segmenting the orogen. The lower crustal anisotropy is highly perturbed signifying a highly heterogeneous nature of the Moho.  Existence of multiple layers of anisotropy possessing distinct geometries varying with depth could be an indication of a highly complex deformational regime resulting from active crustal shortening.

How to cite: Kumar, G., Singh, A., Singh, C., Saikia, D., and Kumar, M. R.: Crustal Seismic anisotropy in Sikkim Himalaya: Implications for deformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10972, https://doi.org/10.5194/egusphere-egu26-10972, 2026.

Regular monitoring of small to moderate sources of continuous earthquake events in the complex tectonics of Himalayan region helps in clearly defining the ongoing seismotectonic process. The study of moment tensor inversion to decipher the fault planes responsible for current seismic activity in the Kishtwar region of Northwest part of Himalaya has been undertaken by establishing a six-station network in 2022 and among them 15 events of shallow origin with magnitude ranging from M_L ~ 3.0 to 4.0 occurred in the local region of seismic network are used for the moment tensor inversion. A few number of studies didn’t able to clearly demarcate the actual scenario of seismotectonics in the northwest part of Himalaya due to its difficult terrain and complex geology. This area has been studied for fault plane solution by a software package ISOLA based on MATLAB programming environment. The source inversion is performed via iterative deconvolution method and synthetic seismogram is generated through green’s function computation via discrete wavenumber method using the regional crustal velocity model. However, the inversion is performed at several trial source position and at various frequency bands based on the epicenter distance and the magnitude of earthquake to find the best solution resulting from the maximum correlation between the recorded and synthetically generated waveforms. A 2D space-time grid search is performed for determining the optimal time and positon of earthquake generation. Perhaps calculating source parameters such as moment magnitude, centroid depth and fault parameters equally with describing uncertainty quantities such as variance reduction factor and condition number will deliver the reliability and stability to the solution. A strong follow-up uncertainty quantification can justify the best estimated fault plane solution. Quality of earthquake event can be calculated through their DC and CLVD percentage and maximum & minimum compression stress direction. Focal mechanism solution of these events following thrust with strike-slip focal mechanism and represents the compressional regime in north-northeastern direction. The centroid depth obtained by moment tensor inversion of all events falls within the depth zone of Main Himalayan Thrust (MHT) suggesting seismicity is concentrated along the major detachment in the region.

How to cite: Tiwari, S. and Gupta, S. C.: Moment tensor analysis and uncertainty quantification of local earthquake events: tectonic implication in the northwestern Himalayan region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13656, https://doi.org/10.5194/egusphere-egu26-13656, 2026.

With the popularization of dense seismic array observations, tomographic imaging of subsurface velocity structures using surface wave dispersion data extracted via subarray partitioning has emerged as a new trend. The primary advantages of subarray-based dispersion data extraction lie in its reduced susceptibility to the inhomogeneous distribution of noise sources, which yields more stable and reliable dispersion measurements. Additionally, this approach enhances the energy of higher-order modes, thereby providing tighter constraints on subsurface velocity structures. Compared with the higher-order modes of Rayleigh waves, both the fundamental and higher-order modes of Love waves exhibit simpler dispersion characteristics with fewer mode crossings and overlaps, making them more favorable for joint inversion to constrain subsurface SH-wave velocity structures.

Traditional subarray surface wave imaging methods (e.g., SSWI) typically perform 1D velocity structure inversion at individual locations first, followed by stitching all 1D models to generate pseudo-2D or 3D velocity models. Despite its simplicity and computational efficiency, this direct stitching strategy is highly vulnerable to uneven station distributions, and the resultant velocity models may suffer from artificial velocity jumps. To address these limitations, Luo & Yao (2025) proposed a direct subarray surface wave imaging method (SSWDI), which eliminates the stitching step inherent in traditional methods and incorporates spatial smoothness constraints on velocity structures, thus enabling more robust inversion of subarray-derived dispersion data for subsurface imaging. However, the SSWDI method originally focused exclusively on the fundamental mode of Rayleigh waves. In this study, we further extend the SSWDI framework to accommodate both fundamental and higher-order modes of Love waves, and validate the improved method using both numerical synthetic data and field observational data.

Reference

Luo, S., and H. Yao (2025), Direct Tomography of S-wave Structure Using Subarray Surface Wave Dispersion Data: Methodology and Validation, Geophysics, 1–60, doi:10.1190/geo-2024-0515.

How to cite: Luo, S.: 3D SH-wave Velocity Tomography via Direct Inversion of Multimode Love Wave Dispersion Curves from Seismic Subarrays, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16937, https://doi.org/10.5194/egusphere-egu26-16937, 2026.

Seismic hazard assessment is crucial for the design of critical facilities, whose damage could lead to severe consequences. The design of such facilities typically requires the definition of seismic actions associated with recurrence periods on the order of 5,000-10,000 years. Earthquakes with such low frequencies are well documented in highly deforming regions, where paleoseismic records commonly encompass several seismic cycles of active faults. In contrast, in slow-deforming regions or areas of low seismicity, the scarcity of seismic data hinders the definition of seismogenic zones. In this context, geological studies of active seismogenic faults are essential, as they allow the characterisation of seismic behaviour over time spans far exceeding those covered by instrumental or historical records. These data can contribute to constraining fault’s seismic cycles and estimating earthquake magnitude–frequency distributions at the fault scale.

Despite their importance, the incorporation of faults into seismic hazard models remains challenging, particularly in low strain regions such as the western margin of the Valencia Trough. This region of the NE of Iberia (from the Vallès-Penedès Graben to the Valencia Depression) corresponds to a passive margin characterised by a basin-and-range structure, bounded by multiple NNE–SSW-oriented normal faults formed during the Neogene rifting episode. Those faults are usually associated with mountain fronts, although our recent studies have found some new faults crosscutting Pleistocene alluvial fans. These newly discovered faults are being studied by means of geomorphology, geophysics, paleoseismology and geochronology in order to estimate their seismic parameters. Several challenges arise when analysing these faults, including fault identification, incomplete geological records, and the need for complex dating techniques.

Moreover, in regions characterised by fault systems, fault interactions may play a significant role. In regions such as the studied area, these interactions may result in long quiescent periods followed by phases of increased activity or even cascading events. Under such conditions, distinguishing between quiescent and active phases is especially difficult, as recurrence intervals are expected to span several thousands of years in both cases.

In this work, we explore existing methodologies for the computation of seismic hazard incorporating geological data from faults and fault systems in slow-deforming regions, using the western margin of the Valencia Trough as a case study. To this end, a detailed geometric characterization of the fault system is carried out to establish the geometric relationships among faults. Recent morphotectonic analyses and newly acquired geological data are then used to constrain the seismic parameters of the studied faults and to estimate their earthquake frequency distributions. Finally, several alternative seismic source models are proposed, forming the basis for the construction of a logic tree for subsequent seismic hazard calculations. These
models, although in progress, provide a framework for improving seismic hazard assessments in slow-deforming regions, contributing to safer design of critical infrastructure.

How to cite: Ollé-López, M., García-Mayordomo, J., Scotti, O., and Masana, E.: A seismogenic modelling approach for rift-basin fault systems in slow-deforming regions: application to the western margin of the Valencia Trough, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20741, https://doi.org/10.5194/egusphere-egu26-20741, 2026.

The 2015 Mw 7.8 Gorkha earthquake was followed by numerous aftershocks that provided important information on active faulting in central Nepal. Accurate moment tensor estimations are essential for determining the source parameters of these seismic events. In this study, we determine double-couple and full moment tensor solutions for selected aftershocks of the 2015 Nepal earthquake sequence using a regional 1D velocity model.

The waveform data recorded by the temporary broadband network (NAMASTE) are used to analyse 51 aftershocks with M > 3.5. A library of Green’s functions is computed using the frequency–wavenumber method based on a 1D velocity model of the Nepal region. Synthetic waveforms derived from the Green’s functions are used to invert the waveform data for moment tensor estimation. Both body waves and surface waves are used in the inversion, and they contribute separately to the moment tensor solutions. The analysis focuses on regional waveforms in relatively higher frequency ranges.

Both double-couple–constrained and full moment tensor inversions are performed, and the resulting source parameters are examined in terms of waveform fit, centroid depth, and fault-plane orientation. This work presents a set of moment tensor solutions for the 2015 Nepal aftershocks using a 1D regional velocity model and provides a reference for future studies using more complex velocity structures.

How to cite: Lahon, P., Silwal, V., and Mahanta, R.: Double-Couple and Full Moment Tensor Solutions of the 2015 Nepal Aftershocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21099, https://doi.org/10.5194/egusphere-egu26-21099, 2026.

The alternative proxy parameters for seismic site amplification beyond the conventional time-averaged shear wave velocity of the upper 30 m (V_S,30) are investigated in this study with a focus on quantities that can be derived or constrained from surface wave-based measurements such as Spectral Analysis of Surface Waves (SASW) and Continuous Surface Wave System (CSWS) testing. Surface wave methods provide dispersion curves that are inverted to obtain near-surface shear wave velocity profiles, which are then used to construct synthetic one-dimensional layered models for ground response analysis. For each profile, two different candidate site parameters are evaluated, including V_S,30 and the impedance ratio between the surface layer and the underlying half-space. These parameters are chosen to reflect what can realistically be inferred from SASW/CSWS-derived velocity profiles, particularly the shallow stiffness and impedance contrasts that strongly influence amplification. Correlation analyses are carried out to quantify how well each parameter explains the variability in amplification across the synthetic suite. The results are used to assess whether the impedance ratio provides stronger or more consistent correlation with amplification than V_S,30, thereby offering guidance on how surface wave–based site characterization can be better integrated into proxy-based amplification and site classification schemes in seismic design practice.

How to cite: Singh, V. and Baidya, D. K.: Evaluating SASW/CSWS-Derived Proxies for Seismic Site Amplification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21425, https://doi.org/10.5194/egusphere-egu26-21425, 2026.

The Rif’s belt is characterized by low to moderate seismic activity resulting from the continental collision between the African and Eurasian plates. This seismic activity, which involves devastation and human losses, requires an in-depth study of its origins and mechanisms. This study aims to identify the geological structures responsible for seismic activity in the eastern Rif by adopting an integrated methodological approach. The methodology relies on the use of a Geographic Information System (GIS) to process and analyze multiple geological, seismological, and geophysical datasets. Various filters were applied to magnetic and gravimetric data (vertical derivatives) to characterize the subsurface. The analysis of earthquake focal mechanisms helped identify active faults. The results show that the seismicity, with a NW-SE orientation, is localized within a fragile depression south of the city of Selouane. The final geological model highlights a system of faults and strike-slips oriented NE-SW and NW-SE. A significant spatial correlation is observed between epicenters and Messinian-aged NW-SE strike-slips, suggesting their reactivation. The analysis indicates that a system of dextral strike-slips is likely the source of this seismic activity. The proposed geodynamic model represents a major advancement in understanding local seismic activities and serves as an essential reference for future studies. These results significantly contribute to the assessment and management of seismic risks, thereby enhancing the safety and resilience of populations in this high-risk area.

KEYWORDS: Geodynamic model; Seismotectonic; Focal mechanism; Magnetic; Gravimetric; ·
Eastern Rif. 

How to cite: Iken, H., Nouayti, A., Nouayti, N., and Khattach, D.: An integrated geodynamic analysis of seismic sources in the Eastern Rif: Insights from geological, seismological, gravimetric, and aeromagnetic data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22669, https://doi.org/10.5194/egusphere-egu26-22669, 2026.

Current demand for critical metals including Cu is outstripping current supply and will further escalate in the future. A significant source of Cu comes from porphyry deposits, which contribute to >60% of global Cu ore production. Many of these porphyry Cu deposits are found along convergent margins such as the Andes and the Sunda-Banda arc in Indonesia and these same arcs also host highly active volcanoes. Understanding the magmatic and geodynamic factors that contribute towards priming magmas for Cu fertility as opposed to volcanic eruptions can aid in identification of prospective targets for exploration.

Here we present analyses of apatite populations from known porphyry Cu deposits and active volcanoes along the Sunda-Banda arc in Indonesia. To gain a complete overview of the mineral associations and their information, we incorporate textural information to analyze both apatite inclusions and their mineral hosts, such as pyroxenes and amphiboles, as well as groundmass apatite. These mineral compositions will serve as input for thermodynamic models to constrain the volatile chemistry and budget, as well as the volatile saturation depths. The information gathered will be combined to test our working hypotheses that the magmas with high Cu fertility store at distinct depths, have geochemical signatures that suggest deep fractionation of garnet and amphibole, and are associated with anomalous geodynamic features such as slab tears.

Our ongoing work advances current understanding on magma storage and transfer along and across fertile magmatic arcs, aiming to better understand magmatic pre-conditioning for porphyry copper deposit formation to complement exploration efforts to find copper deposits in the geological records.

How to cite: Utami, S. B., Ubide, T., Rosenbaum, G., Li, W., Handini, E., Wood, S., Handley, H., and Goode, L.: Insights into the copper accumulation potential of magmas along the Sunda-Banda arc, Indonesia from apatite and its mineral hosts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-938, https://doi.org/10.5194/egusphere-egu26-938, 2026.

Abstract:

Strike-slip basement faults and their related segments are crucial for oil and gas exploration. These faults are considered favorable channels for hydrocarbon migration. The multistage activities of these faults influence the development of hydrocarbon-bearing structures. They can also produce fracture systems that enhance reservoir properties and boost oil and gas production. Understanding how strike-slip fault segments and their associated structures affect hydrocarbon accumulation is essential for geological research and exploration planning. This study aims to characterize the geometry and structural evolution of the strike-slip basement fault with Pan-African or Arabian trends, investigate the relationship between fault segments, and assess their impact on the distribution of hydrocarbon traps. This research focuses on the structural and tectono-sedimentary analyses of the Kazerun fault system based on processing and interpretation of the surface data (e.g., satellite images and aeromagnetic data) and the subsurface data (e.g., 2D and 3D seismic and well data) in the Zagros orogenic belt, SW Iran. The relationship between the segmented strike-slip fault zone and hydrocarbon reservoirs is analyzed through map view patterns and profile features. Results reveal that the Arabian-trending Kazerun fault system comprises segmented dextral strike-slip faults and is considered a transform and wrench fault. These faults display various planar configurations, including linear, en-echelon, horsetail splays, and irregular geometries in the map view. Based on the seismic data interpretation, three structural styles develop along the Kazerun strike-slip fault zone, including vertical or oblique, pull-apart (negative flower structure), and push-up (positive flower structure) segments. Releasing and restraining bends and oversteps formed at the tail end of the Kazerun strike-slip fault segments. In the study area, salt diapirism occurred along the pull-apart segment and the releasing bend. Hydrocarbon traps are developed in the push-up segment and the restraining bend. Fractures are less prominent in the vertical segments but more developed in push-up and pull-apart segments, which act as pathways for fluid migration and improving reservoir quality. The push-up segment and restraining bend exhibit a higher degree of branching fractures, making them the most significant for reservoir development. This research shows that strike-slip fault segmentation (in the form of fault overlapping or stepping) and their lateral linkage control the reservoir distribution and connectivity. Recognizing the growth and lateral connections of strike-slip fault segments is crucial for structural analysis and predicting fault-controlled reservoirs. These findings offer valuable insights into the structural characteristics of strike-slip fault zones and can enhance oil and gas exploration in the Zagros fold-and-thrust belt and other similar regions.

Keywords:

Strike-slip basement fault, Segmentation pattern, Oil/Gas fields, Zagros orogenic belt, SW Iran

How to cite: Soleimany, B., Tajmir Riahi, Z., Payrovian, G. R., and Sepahvand, S.: Impact of segmentation pattern of the Pan-African trending strike-slip basement fault on the spatial distribution of hydrocarbon traps in SW Iran, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1377, https://doi.org/10.5194/egusphere-egu26-1377, 2026.

Skarn-type Cu–Fe–Au mineralization in the Middle–Lower Yangtze River Metallogenic Belt (MLYRB) is closely associated with Early Cretaceous intermediate to felsic magmatism; however, the links between magmatic evolution and ore-forming efficiency remain poorly constrained. In the Tonglushan ore field, one of the largest Cu–Fe–Au skarn systems in eastern China, multiple intrusive phases are spatially distributed, providing an ideal opportunity to investigate how magmatic processes control metallogenic potential. Here we present new geochronological and geochemical constraints on quartz monzodiorite porphyry, quartz monzodiorite, quartz diorite, and their mafic microgranular enclaves (MMEs) from different sectors of the Tonglushan ore field.

Zircon U–Pb ages indicate synchronous emplacement of all intrusive phases and MMEs at ca. 142–140 Ma. Whole-rock geochemistry and Sr–Nd–Hf isotopes indicate that these intrusive rocks belong to a high-K calc-alkaline to weakly adakitic series and were derived from an enriched lithospheric mantle source modified by slab-derived components, followed by extensive fractional crystallization. The MMEs record efficient mixing between mafic and felsic magmas, highlighting the role of mafic recharge in supplying heat and metal components to the evolving system. Estimates of magmatic water contents and oxygen fugacity from zircon compositions reveal systematic variations among different intrusions. The Jiguanzui and Tonglushan quartz monzodiorite porphyries are characterized by high water contents and elevated oxidation states, consistent with intense Cu–Au and Cu–Fe–Au mineralization, whereas the weakly mineralized Zhengjiawan quartz diorite exhibits lower values. These observations suggest that, beyond structural controls, the metallogenic fertility of intrusions in the Tonglushan ore field was primarily governed by fractional crystallization, mafic magma input, and the development of highly hydrous and oxidized magmatic systems.

Our study demonstrates that integrated whole-rock and zircon geochemical indicators provide effective tools for evaluating the ore-forming potential of skarn-type Cu–Fe–Au mineralization related intrusions in the MLYRB.

How to cite: Zhang, M. and Tan, J.: Magmatic controls on skarn-type Cu–Fe–Au mineralization in the Tonglushan ore field, Middle–Lower Yangtze River Metallogenic Belt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2162, https://doi.org/10.5194/egusphere-egu26-2162, 2026.

Low-temperature thermochronology provides key constraints on the post-mineralization exhumation and preservation of orogenic gold deposits. In this study, we investigate the exhumation histories of the Anjiayingzi and Jinchanggouliang gold deposits, located respectively in the Kalaqin metamorphic core complex (MCC) and the Nuluerhu magmatic dome within the Chifeng–Chaoyang metallogenic belt on the northern margin of the North China Craton.

Both deposits formed in the Early Cretaceous (~130 Ma), but at significantly different depths (5.6–7.1 km for Anjiayingzi and 1.0–2.6 km for Jinchanggouliang), and are currently exposed at the surface, implying differential post-mineralization exhumation. Zircon and apatite (U–Th)/He and fission-track analyses were conducted on ore-hosting rocks to reconstruct cooling and exhumation histories. Combined age–elevation relationships and thermal history modeling reveal that the Anjiayingzi deposit experienced multi-stage, rapid exhumation totaling ~6.75 km since mineralization, with the most intense exhumation occurring between 130 and 80 Ma. In contrast, the Jinchanggouliang deposit underwent slower and more limited exhumation, with a total exhumation of ~2.50 km over the same period.

The contrasting exhumation histories coincide with an Early Cretaceous regional extensional regime affecting the northern margin of the North China Craton. We suggest that tectonic setting plays a first-order role in controlling post-mineralization exhumation. Deposits hosted within MCCs are characterized by rapid extensional denudation related to detachment faulting, whereas deposits hosted in magmatic domes are mainly exhumed through regional uplift and surface erosion. These results emphasize the importance of structural architecture in governing the exhumation, preservation, and exposure of gold deposits in extensional orogenic systems.

How to cite: Li, A. and Fu, L.: Post-mineralization exhumation of gold deposits on the northern margin of the North China Craton: constraints from low-temperature thermochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2243, https://doi.org/10.5194/egusphere-egu26-2243, 2026.

The Southeast Anatolian Suture Belt hosts the oceanic and continental remnants of the southern Neotethyan realm. During the Late Cretaceous, the southern Neotethyan domain experienced an Andean-type magmatism on its northern continental margin (the Tauride-Anatolide Platform), characterized by the Baskil Magmatics. The plutonic part of this unit is intruded by numerous dikes, which are the primary focus of this study. The U-Pb zircon dating of the dikes and their granodioritic host rocks indicates that their emplacement occurred within a narrow interval, between 81-79 Ma. The dikes vary chemically from basalt to dacite, while the host rocks range from andesitic to dacitic. On the normal mid-ocean ridge (N-MORB)-normalized plots, all samples exhibit negative Nb anomalies. Trace element systematics reveals that this dike system is chemically heterogeneous, consisting of five distinct chemical types. The elemental and isotope ratios indicate varying contributions from depleted and enriched components. All chemical types, with relative Nb depletion, suggest incorporation of slab-derived and/or crustal additions. This interpretation is further supported by the EM-2-like Pb isotopic ratios. Based on the variability in elemental and isotopic composition, this intrusive system appears highly heterogeneous, likely due to the combined effects of mantle source, crustal contamination, and fractional crystallization. The bulk geochemical characteristics of the studied dikes and their host rocks suggest that these intrusives formed at a continental arc. Considering the available paleontological and geochronological age data, it appears that the intraoceanic subduction and continental arc magmatism in the Southern Neotethys occurred simultaneously; the former created the Yüksekova arc-basin system, whereas the latter formed the Baskil Arc.

Note: This study was supported by project Fübap-MF.15.12.

How to cite: Ural, M., Sayit, K., Koralay, E., and Göncüoglu, M. C.: Geochemical and Geochronological approaches of Baskil Dikes (Elazığ, Eastern Turkey): Discrimination between the Late Cretaceous Continental and Oceanic Arc-related Magmatism in the Southern Neotethys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2274, https://doi.org/10.5194/egusphere-egu26-2274, 2026.

The Kaladgi Basin, an E–W trending intracratonic basin in the northern part of the Dharwar Craton, preserves favourable structural and stratigraphic conditions for sandstone-hosted and unconformity-related U–REE mineralization. In the study area, the Neoproterozoic Cave Temple Arenite (CTA) of the Badami Group unconformably overlies deformed Mesoproterozoic rocks of the Bagalkot Group. The crystalline basement of the Kaladgi Supergroup comprises Meso- to Neoarchaean Peninsular Gneiss and the Chitradurga Greenstone Belt. This association of cratonic basement, schist belt, and basin-margin fault and fold systems provides an excellent structural framework for hydrothermal fluid circulation and mineralization.

Detailed thematic mapping at 1:25,000 scale in the Ramdurg–Suriban sector reveals that NNW–SSE–oriented Dharwarian stress generated a series of anticlines and synclines involving the Saundatti Quartzite, Malaprabha Phyllite, and Yaragatti Argillite, as constrained by conjugate fracture analysis and S–C fabric development. An E–W trending tectonic fault defines the contact between the Peninsular Gneissic Complex and Saundatti Quartzite, with comparable faulted contacts also developed within the Bagalkot Group. Intense faulting resulted in silicification, chalcedonic brecciation, and pervasive hydrothermal alteration along these contact zones. Transverse normal faults with associated brecciation accommodate strain related to the main E–W structure and indicate episodic reactivation of the basin architecture.

Fusion ICP–MS analysis of 20 bedrock samples collected proximal to these fault zones shows U₂₃₈ concentrations exceeding twice the threshold values of National Geochemical Mapping (NGCM) stream sediment sample. Uranium enrichment is spatially associated with Malaprabha Phyllite, first-cycle CTA, and silicified banded hematite quartzite veins of the Hiriyur Formation. Chondrite-normalized (La/Yb)_n versus (Eu/Eu*)_n systematics indicates a dominantly low-temperature basinal brine hydrothermal system characterized by low (La/Yb)_n <25 and negative Eu anomalies. Redox-sensitive (Ce/Ce*)_n versus (Eu/Eu*)_n plots further indicate reducing fluid conditions. In contrast, quartz–chlorite veins developed within sheared Malaprabha Phyllite and younger dolerite record comparatively higher-temperature fluids, marked by Eu²⁺ mobilization ((Eu/Eu*)_n > 0.8) and negative Ce anomalies. These results suggest that reactivated, structure-controlled tectonites acted as effective fluid pathways, with the TTG-dominated Peninsular Gneissic Complex serving as a likely uranium source and contributing to localized U–REE mineralization along the basin margin.

How to cite: Mahanandia, A., Lal, M. M., Singh, T. G., Nandhagopal, N., and Singh, S.: Structure-controlled Uranium + REE mineralization in low temperature basinal brine hydrothermal system at the contact of Kaladgi Basin and Peninsular Gneissic Complex, South India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2923, https://doi.org/10.5194/egusphere-egu26-2923, 2026.

Gravity observations are widely used in volcanic monitoring to infer subsurface mass redistributions, commonly interpreted in terms of magma intrusion. However, gravity changes may also arise from thermo-poro-elastic (TPE) processes associated with temperature and pore-pressure variations in fluid-saturated reservoirs. Neglecting these effects can lead to ambiguous or misleading interpretations of gravity signals during volcanic unrest.

The recent development of TPE inclusion models allows us to describe the mechanical fields induced by fluid-saturated rock volumes undergoing pore-pressure and temperature variations. These sources can coexist with magmatic sources within volcanic systems and are typically located at shallower depths than the deep magmatic reservoir, which acts as the primary engine by releasing hot fluids. These exsolved fluids rise from depth and either accumulate in, or migrate through, overlying brittle rock volumes, which respond to thermal and pore-pressure perturbations and therefore act as secondary sources of deformation and gravity change. In this work, we consider a disk-shaped TPE inclusion, a geometry that has been successfully applied in previous studies to represent deformation fields that are predominantly radial and associated with axisymmetric sources.

The results show that gravity variations induced by a TPE inclusion depend strongly on the fluid phase. Both liquid water and gaseous fluids can produce the same significant ground uplift, but lead to different gravity residuals: negative for liquid water and minor but positive for gaseous fluids. In contrast, condensation or vaporization of a thin layer near the surface can generate large gravity changes without notable deformation. As a result, heating and pressurization of a TPE inclusion can mask or weaken the gravitational signature of magma ascent, complicating the interpretation of gravity data and highlighting the need to account for hydrothermal effects when estimating magma volumes during unrest.

Gravity data collected over the past decades at the Campi Flegrei caldera (Italy) provide an ideal test site for applying our model and offer intriguing insights into both past and current unrest phases, although our results are applicable to any volcanic system with an active hydrothermal system. These findings highlight the importance of incorporating TPE effects into gravity data interpretation and integrated volcano monitoring strategies. Accounting for them improves our ability to distinguish between magmatic and hydrothermal contributions, leading to more robust assessments of subsurface dynamics and volcanic hazards.

How to cite: Nespoli, M., Bonafede, M., and Belardinelli, M. E.: Thermo-Poro-Elastic effects as hidden drivers of gravity signals in volcanic systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3001, https://doi.org/10.5194/egusphere-egu26-3001, 2026.

Abstract: Unlike ionosphere, troposphere is nondispersive and delays cannot be determined from observations of signals at different radio frequencies. In GNSS data processing, station height, receiver clock error and tropospheric delay are highly correlated to each other, especially in kinematic situations. Although zenith hydrostatic delay can be provided with sufficient accuracy, zenith wet delay, which is more spatially and temporally varying than hydrostatic component, has to be carefully processed. Usually, temporal dependence of tropospheric delays at zenith is modeled as a random walk process with a solely given process noise rate σ_rw in GNSS processing. The usually used σ_rw is a constant throughout whole process session and is in range of 3~10 mm per sqrt hour. This setting is generally appropriate for desirable GNSS positioning estimation in normal conditions. However, modeling zenith tropospheric delay by using a constant σ_rw in whole session will be unsatisfactory in cases of special weather conditions, e.g., the shower case. The σ_rw is a measure of magnitude of typical variation of zenith path delay or its residual after calibration in a given time. Values of σ_rw that are too large could weaken strength for geodetic estimation, while values that are too small may introduce systematic errors, since a strong constraint for tropospheric unknowns is imposed to stabilize the system. The random walk model for wet delay must be constrained approximately to "correct" value to obtain optimum parameters estimates. Assuming temporal change of tropospheric delay at an arbitrary station can be described by random walk model, the process noise levels were calculated by some scholars. They employed water vapor radiometric, surface meteorological measurements and numerical weather model data set for optimum selection of σ_rw. In general, although a lot of efforts have made to optimize post-processing and/or real-time GNSS tropospheric delay estimation, stochastic modeling of zenith wet delay remains insufficiently investigated, especially for kinematic applications. Since temporal variation of zenith wet delay depends on water vapor content in atmosphere, it seems to be reasonable that constraints should be geographically and/or time dependent. In this work, we first investigate sensitivity of both station coordinates and zenith wet delay estimators on different σ_rw values, and then try to propose to take benefit from post-processed static or kinematic estimated tropospheric delay to obtain the optimum σ_rw. The general objective is that if zenith tropospheric delays are of different variation characteristic, e.g., relatively stable or rapid changing, then a varying σ_rw, e.g., small or large value, could be employed, which should be more theoretically feasible compared with a invariant σ_rw. The initial results show that the new method can efficiently obtain epoch-wise σ_rw values at different stations. Compared to results from conventional constant σ_rw value, time-varying noise rate can improve precision of PPP solutions. We note that this first results represent performance view at several selected stations, more works should be done to draw global or even long-term conclusions.

This work is supported by National Natural Science Foundation of China (42304010), Youth Foundation of Changzhou Institute of Technology (YN21046).

How to cite: Wang, M., Lu, B., and Zhong, Q.: The initial results about optimum the random walk process noise rate for GNSS tropospheric delay estimation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4327, https://doi.org/10.5194/egusphere-egu26-4327, 2026.

The Yanshan-Liaoning metallogenic belt (YLMB), the second-largest molybdenum deposit cluster in China, hosts over twenty porphyry molybdenum deposits, including the large-scale Caosiyao, Sadaigoumen, and Dasuji deposits, as well as the newly discovered medium- to large-scale Qiandongdamiao, Zhujiawa, and Taipingcun deposits. Geochronological data indicate that the duration of molybdenum mineralization spanned ca. 100 Myrs, from the Triassic to Early Cretaceous (240–140 Ma). However, the reasons for such a prolonged or multi-period metallogenic event, and the magmatic and geodynamic processes controlling the spatial–temporal distribution of these deposits, remain poorly understood.

Here we summarize the geological, chronological and geochemical data from selected molybdenum deposit to reconstruct the temporal–spatial distribution and tectonic setting of ore- metallogenic history in the YLMB. The formation of molybdenum deposit in the YLMB can be divided into three periods of 240–220 Ma, 185–180 Ma and 160–140 Ma. The ore-forming intrusions among these three periods illustrate an overall characteristic that metaluminous to peraluminous, high-K calc-alkalic to shoshonite series acidic rocks, and the source of intrusions is the Archaean–Paleoproterozoic lower crust. Through in-depth analysis of Sr-Nd-Hf isotopic data, we find that the magma source that during the 185-180 Ma stage is relatively younger, mainly reflecting the partial melting of Paleoproterozoic crust, whereas the magma source that during the 240–220 Ma and 160–140 Ma stages likely are contained both from the Paleoproterozoic and Neoarchean crust. Further calculations using trace element content ratios reveal a shallower magma source along the magma evolution during the 240–220 Ma period, which supported by the gradual decrease trend in crustal thickness. In contrast, the calculation of crustal thickness during the 185–180 Ma and 160–140 Ma stages show an increase trend, suggested an thicken process in the depth of the magma source.

Spatially, the porphyry molybdenum deposits formed during these three periods exhibit distinct geographic distributions. Deposits formed at 240–220 Ma are mainly located in the northern part of the YLMB, including the Chengde-Zhangbei-Fengning district. Those formed at 185–180 Ma are primarily located in the Liaoxi district, eastern part of the YLMB while deposits formed at 160–140 Ma are located in the southern part of the YLMB, particularly in the Xinghe-Zhangjiakou-Xinglong district. We propose that the variations of the spatial–temporal distribution and geochemical characteristics of the molybdenum deposit formed during different periods in the YLMB are controlled by variations of their geodynamic settings. The porphyry molybdenum deposits formed in 240–220 Ma are under the post-collision or post-orogenic extension environment between the North China Plate and the Siberian Plate in the Middle Triassic. Deposits formed in 185–180 Ma are under the extension environment in the early stage of the Yanshanian movement, and porphyry molybdenum deposits formed in 160–140 Ma are in the strong extrusion environment in the main stage of the Yanshanian movement.

Our findings demonstrate the multi-period metallogenic history of the YLMB, highlighting the critical role of magma source, storage depth, and geodynamic setting in controlling the formation of porphyry molybdenum deposits.

How to cite: Jiang, C., Liu, Q., Cao, L., Li, A., and Fu, L.: Magmatic and geodynamic processes control on the formation of porphyry molybdenum deposits: Insights from the Yanshan-Liaoning metallogenic belt, northern margin of North China Craton, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4396, https://doi.org/10.5194/egusphere-egu26-4396, 2026.

Microcontinents are isolated fragments of continental crust surrounded by oceanic lithosphere. They commonly occur in modern ocean and are also recognized in orogenic system. They can be accreted onto continental margins through collision and subduction during ocean-continent subduction process, and lead to migration of subduction zone toward the oceanic side. However, it is not well understood whether and how this process can be recorded by metamorphism. In this study, a high grade metamorphic-magmatic terrane is recognized along the previously defined Qilian block. The Datong-Mengyuan terrane (DMT) is separated from the low-medium grade metamorphic basement of the Qilian block (QLB) by dextral strike-slip ductile shear zone and ophiolite mélange. The petrology and texturally-controlled U-Pb multi-mineral geochronology reveal that the mafic and felsic granulites from the DMT record two significance events of metamorphism. The earlier event experienced a pressure and temperature conditions of 11.4–13.7 kbar and 735–805°C at ca. 500 Ma, and later stage records a pressure and temperature conditions of 5.5–9.6 kbar and 790–840°C at ca. 460 Ma. We suggest that the earlier Cambrian high pressure granulite facies metamorphism is resulted from collision and thickening related to the accretion of the DMT to the Qilian block, and the later low-medium pressure granulite facies overprinting formed by decompression heating, which happened in continental arc setting and is associated with shift of subduction zone toward the ocean. These findings provide a critical example of metamorphic record on the microcontinent accretion and convergent plate boundary dynamics.

How to cite: Mao, X. and Zhang, J.: Metamorphism records microcontinent accretion and subduction relocation: an example from early Paleozoic Qilian Orogenic Belt, NW China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4872, https://doi.org/10.5194/egusphere-egu26-4872, 2026.

The distribution of rare gases within the Earth’s interior has caught the attention of scientists for the past few years. The inertness and volatility of noble gases make them excellent tracers for understanding the chemical evolution of Earth’s mantle and atmosphere. Previous studies indicate that noble gases can be found associated with clathrates, form their own oxides, or, in some cases, noble gases such as helium and xenon can even bond with Fe under extreme pressure (p) - temperature (T) conditions like those in Earth’s core. However, the ability of lower mantle mineral phases to house rare gases remains poorly understood, leaving important gaps in knowledge. Helium and argon are noble gases of interest in this study. The isotopes ⁴He and ⁴⁰Ar are produced from the radioactive decay of ²³⁸U and ⁴⁰K within the Earth’s interior, while ³He and ³⁶Ar are regarded as primordial, introduced during the accretion of Earth. Dong et al. (2022) revealed that noble gases can become reactive under mantle pressure conditions. Still, their ability to be incorporated into mantle minerals via adsorption needs to be thoroughly studied, as there are many limitations in the experiments conducted to measure the solubility of noble gases in minerals under mantle p-T conditions. In this study, we investigated the adsorption behavior of helium and argon on the (001) plane of periclase (MgO) by employing first-principles density functional theory (DFT) calculations.

Adsorption energies were estimated across pressures ranging from 0 to 125 GPa, representative of conditions throughout Earth’s interior, i.e., approximately up to the Core Mantle Boundary (CMB). At ambient pressure, both helium and argon showed negative adsorption energies, indicating stable adsorption relative to isolated species (MgO, Ar, He). These energies became increasingly negative with pressure, becoming notably negative beyond 75 GPa which corresponds to lower mantle pressures. This may be due to the accelerated reactivity of noble gases at extreme pressure conditions, as reported in previous studies. Additionally, under all pressure conditions argon exhibited stronger adsorption than helium, indicating enhanced argon retention in lower mantle conditions. However, further investigations into the mechanical and dynamical stability of these adsorbed structures are required to completely understand the mechanisms governing noble gas occurrence in the Earth’s lower mantle.

How to cite: Karangara, A. and Kumar Das, P.: Adsorption of Helium and Argon on the (001) Surface of Periclase: A First-Principles Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4988, https://doi.org/10.5194/egusphere-egu26-4988, 2026.

Soil CO₂ emission is a key proxy for investigating fluid migration processes associated with volcanic and tectonic activity. In particular, the analysis of the spatial distribution of geochemical anomalies represents an effective tool for identifying active structures and zones of ongoing deformation. Numerous studies have shown that faults and fracture systems play a fundamental role in controlling the localization and evolution of surface geochemical anomalies.

Vulcano Island (Aeolian Archipelago, Italy) is characterized by intense hydrothermal activity and persistent soil CO₂ emissions, providing a natural laboratory to investigate the relationships between fluid circulation and active tectonic structures. In this study, we present an integrated analysis of soil CO₂ fluxes based on results obtained from periodic surveys and continuous soil CO₂ flux records acquired at key sites across the island.

Periodic measurements are performed on fixed spatial grids, allowing the production of soil CO₂ flux maps and the identification of areas characterized by elevated degassing rates. At selected sites, the carbon isotopic composition of gases is analyzed to constrain gas sources.

These spatial datasets provide insights into the structural control exerted by the main tectonic lineaments on gas release at the surface. Continuous CO₂ flux monitoring enables the investigation of temporal variations and transient degassing signals potentially related to seismic and tectonic processes. In particular, the recent volcanic crisis at Vulcano Island, started on 2021, characterized by a marked increase in soil CO₂ flux, allowed a more detailed identification of preferential CO₂ emission pathways, highlighting zones of enhanced permeability associated with fault and fracture systems.

This work is carried out within the framework of the CAVEAT project (Central-southern Aeolian islands: Volcanism and tEArIng in the Tyrrhenian subduction system), which aims to provide a comprehensive understanding of the current geodynamics of the southern Tyrrhenian region.

How to cite: De Gregorio, S., Camarda, M., Capasso, G., Di Martino, R. M. R., Pisciotta, A., and Prano, V.: Soil CO₂ Emissions as Indicators of Fluid Pathways in Volcanic–Tectonic Environments: Insights from Vulcano Island, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5147, https://doi.org/10.5194/egusphere-egu26-5147, 2026.

Mg-bearing minerals, including brucite [Mg(OH)₂], lizardite [Mg₃(Si₂O₅)(OH)₄] and iowaite [Mg₆Fe³⁺₂(OH)₁₆Cl₂·4H₂O] are variably reactive with carbon dioxide (CO₂) at Earth’s surface conditions and can be used to mineralize and sequester this greenhouse gas. Here, we assess the impact of temperature (5, 20 and 40 °C) on the rate of CO₂ mineralization of these minerals. At each temperature, mineral powders (~100 mg ) were placed in a 7.5-litre flow-through reactor that was supplied with humidified laboratory air (0.042% CO₂; 100% RH) at ~200 mL/min. Subsamples (n = 54) of each mineral were collected over 3 months and analyzed (XRD, TIC, BET) to ascertain the amount and rate of carbonation as a function of time, temperature, and mineral feedstock.

Preliminary X-ray diffraction (XRD) results show the formation of dypingite [Mg₅(CO₃)₄(OH)₂·5H₂O] and a decrease in the abundance of brucite over time. The 003 peak of iowaite shifted to smaller d-spacings, indicating replacement of chloride by carbonate ions and a transition to a more pyroaurite-rich [Mg₆Fe³⁺₂(CO₃)(OH)₁₆·4H₂O] composition. Total Inorganic Carbon (TIC) measurements were used to determine the amount and rate of carbonation as a function of time, temperature, and mineralogy.

The results of this study will help us estimate the carbonation kinetics of these minerals in ultramafic ores and mine tailings under different temperature conditions relevant to large-scale deployment of CO₂ mineralization at mines across the globe.

How to cite: Sulemana, S. Z., Wilson, S., Moyo, A., Akhtar, S., Power, I. M., and Sleep, S.: Temperature-dependence of CO2 drawdown into Mg-bearing minerals., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6294, https://doi.org/10.5194/egusphere-egu26-6294, 2026.

The main focus of the study is to calibrate Sentinel-1 InSAR Line-of-Sight (LOS) velocities along a ~700 km North-South transect extending from the Black Sea coast (Kastamonu-Samsun) to the Mediterranean (Mersin-Gaziantep). This transect encompasses diverse tectonic regimes, including the North Anatolian Fault Zone, the Central Anatolian Block, and the junction of the East Anatolian Fault Zone. This complex structure of the transect requires detailed analysis of the GNSS-InSAR calibration procedure including validation. 

Across the study region, processed LiCSAR products are integrated with 3D velocities derived from the continuous local CORS network (21 stations) and an extensive campaign-based GNSS network (200 stations). For calibration, GNSS velocities are first projected into the satellite LOS geometry using LOS vectors derived from coherent InSAR pixels within a 1-km radius. The velocity bias (ΔVlos) is calculated at continuous GNSS locations. This correction surface is propagated using various conventional and Machine Learning techniques independently, including Kriging, Weighted Least Squares (WLS) based Quadratic Surface fitting, Thin Plate Spline (TPS) and Radial Basis Functions (Gaussian, Multiquadric, and Inverse Multiquadric). To address specific error sources, the contributions of topography-correlated atmospheric delays and local spatial trends are also analyzed by Geographically Weighted Regression (GWR) and Random Forest regression. Cross-validation is applied to assess the quality of each model individually where spatial random sampling and plate boundaries are also considered. This study presents preliminary results for obtaining a validated basis for generating up-to-date velocity fields over Türkiye.

How to cite: Elvanlı, M. and Durmaz, M.: Comparative Analysis of Machine Learning and Geostatistical Approaches for GNSS-InSAR Integration: A Case Study in Anatolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7178, https://doi.org/10.5194/egusphere-egu26-7178, 2026.

Geomagnetic storms (GS) significantly perturb the near-Earth environment, leading to enhanced thermosphere density, increased non-conservative forces, and degraded satellite orbit determination, particularly for Doppler-based techniques such as DORIS. In this study, we investigate and improve DORIS orbit determination performance during GS conditions by developing storm-adapted processing strategies. Storm days were classified using geomagnetic indices and categorized into moderate to severe storm levels (G3-G5).

Four distinct processing strategies were implemented and evaluated: a standard operational solution and three experimental storm-adapted solutions, designed through systematic modifications of drag constraints and observation-elimination criteria. These strategies were tested through targeted daily and weekly experiments conducted across multiple DORIS-equipped satellites, with a particular emphasis on periods of intense storms.

The storm-adapted strategies demonstrate clear performance improvements relative to the standard solution during geomagnetic storms. The modified strategies reduce orbit residual RMS in all orbital components, improve Length-of-Day (LOD) variance by approximately 40-80%, and decrease LOD mean biases by nearly 60%. Additionally, Earth Rotation Parameters (ERP) exhibit notable improvements, with reductions of approximately 22–25% in both bias and variability for the polar motion components (X/Y pole). Among the tested configurations, the combined strategy, particularly when applied with zero-rotation constraints, consistently delivers the best performance during intense storm conditions (Kp ≥ 8+). These results demonstrate that storm-adapted DORIS processing strategies significantly enhance orbit and geophysical parameter estimation during disturbed space-weather conditions.

How to cite: Kumar, V., Stepanek, P., Filler, V., Balasubramanian, N., and Dikshit, O.: Impact of Storm-Adapted DORIS Processing on Orbit Quality and Earth Rotation Parameters During Geomagnetic Storms , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7764, https://doi.org/10.5194/egusphere-egu26-7764, 2026.

Abstract: The study of fluid inclusions and sulfur isotope characteristics of barite deposits is crucial for tracing the source of ore-forming materials and predicting prospecting targets. Current research indicate that the Sangmuchang barite deposit in northern Guizhou is primarily hosted within the joint fractures of dolomites in the Sinian Dengying Formation and Cambrian Qingxudong Formation. The contact between ore bodies and surrounding rocks is distinct, with the orebodies occurring as veins and lenticular. The ore textures are mainly veinlets, stockworks, massive, and banded, while the ore structures consist of inequigranular tabular-columnar blastic, fine-crystalline, and arenaceous texture.  Fluid inclusion studies reveal that  the inclusions are single-phase aqueous inclusions. Microthermometric measurements of 33 inclusions show that their homogenization temperatures range from 81°C to 182°C, with an average of 132°C; Salinity values vary from 9.61 wt.% NaCl eqv to 20.63 wt.% NaCl eqv, with an average of 17.53 wt.% NaCl eqv. Ten sulfur isotope analyses from the deposit show that the δ³⁴SV-CDT values range from 40.89‰ to 46.95‰, with a mean of +44.51‰.The characteristics of fluid inclusion salinity, temperature and sulfur isotopes suggest that the ore-forming fluids of this barite deposit are characterized by moderate-low temperature and moderate-high salinity. These ore-forming fluids were mainly derived from basin brines, with contributions from meteoric water. The significant enrichment of heavy sulfur isotopes and homogeneous sulfur isotope composition reveal that the sulfur source of ore-forming materials in this barite deposit is a relatively singular source for the sulfur in the ore-forming materials, which is similar to the δ³⁴S characteristics of Sinian marine evaporites, suggesting a close genetic relationship between the sulfur source and evaporites. Therefore, the Sangmuchang barite deposit is interpreted as a moderate-low temperature hydrothermal deposit.  It was formed by the migration of moderate -low temperature hydrothermal fluids in the sedimentary basin, which leached ore-forming materials from underlying and surrounding barium-rich evaporite sequences, followed by precipitation within structural fracture zones under the mixing of meteoric water. The structural fracture zones and areas indicative of fluid migration pathways along the basin margin are important targets for exploration prediction. Keywords: ore-forming fluid; fluid inclusion; sulfur isotope; barite; northern Guizhou

How to cite: Chen, Y., Wang, J., and Liu, Z.: Study on the Source of Ore-Forming Materials of the Sangmuchang Barite Deposit in Northern Guizhou, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8505, https://doi.org/10.5194/egusphere-egu26-8505, 2026.

Uranium is a strategically important metal with applications in nuclear energy, medicine, radiometric dating, food processing, industrial radiography, material sciences, and catalysis. This study presents a detailed microtextural and geochemical investigation of uranium mineralization from the Bodal uranium mine, Mohla-Manpur-Chowki, Central India. Uranium occurs as both crystalline and colloidal precipitates, with coffinite [U(SiO₄)_1-x(OH)_4x] and gummite representing the dominant uranium-bearing phases. The mineralization is spatially and genetically associated with altered metabasalts. Petrographic and geochemical evidence indicates that late-stage hydrothermal alteration played a crucial role in uranium remobilization and ore enrichment. Sulphide minerals, including cobaltite (CoAsS), galena (PbS), arsenopyrite (FeAsS), and chalcopyrite (CuFeS₂), are intimately associated with uranium phases and likely acted as effective reductants and sorption substrates, facilitating uranium precipitation under reducing conditions. The ore assemblage is accompanied by abundant accessory minerals such as zircon, allanite, and apatite. Substitution of U⁴⁺ for Zr⁴⁺ in zircon locally records uranium-rich hydrothermal fluids and contributes to zirconium enrichment. Collectively, these observations suggest that hydrothermal fluid–rock interaction and redox-controlled precipitation were the dominant processes responsible for uranium enrichment at the Bodal mine.

Keywords: Uranium mineralization; Hydrothermal alteration; Redox-controlled precipitation; Bodal mine; Central India

How to cite: Ganveer, S., Mallick, S. P., and Pruseth, K. L.: Hydrothermal remobilization and redox trapping of uranium in metabasalts of the Bodal mine, Central India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11094, https://doi.org/10.5194/egusphere-egu26-11094, 2026.

The Kirazlı porphyry and high-sulfidation (HS) epithermal system is situated in the central Biga Peninsula of northwestern Türkiye, a region characterized by the protracted closure of the Tethyan oceanic branches and the subsequent collision of Gondwana-derived continental fragments with the Sakarya Zone. This geodynamic framework facilitated the development of diverse tectono-magmatic environments, leading to the formation of porphyry and associated hydrothermal mineralization during the Cenozoic. Based on established geochronological data, magmatism in the Biga Peninsula occurred in five discrete chronostratigraphic episodes: Paleocene to Early Eocene (65–49 Ma), Middle–Late Eocene (49–35 Ma), Late Eocene to Early Oligocene (35–23 Ma), Late Oligocene to Middle Miocene (~23–14 Ma), and Late Miocene to Pliocene (14–5 Ma). Mineralization within the Kirazlı district is temporally constrained to two primary intervals—Late Eocene to Early Oligocene and Oligocene to Early Miocene corresponding to specific magmatic pulses and structurally mediated by major regional shear zones.

Integration of the ages of fault-hosting lithologies, structural styles, fault geometries, and paleostress reconstructions indicates three distinct tectonic phases consistent with the regional Cenozoic evolution: (1) NW–SE extension (Phase-1), (2) NNE–SSW extension (Phase-2), and (3) NE–SW extension (Phase-3). Detailed field observations, petrographic analysis, and microstructural investigations of oriented samples demonstrate that the porphyry and HS-epithermal stages were governed by these shifting stress regimes. B- and D-veins associated with the porphyry stage exhibit preferred orientations along an ENE–WSW strike, consistent with the NW–SE extensional regime of Phase-1. In contrast, late-stage quartz veins within the HS-epithermal overprint formed under a NNE–SSW extensional stress field, aligning with the Phase-2 tectonic pulse.

Analysis of fault planes for both Phase-2 and Phase-3 indicates that ENE–WSW and NE–SW strike directions are common to both phases. Phase-3 displays kinematic and geometric features characteristic of the modern transtensional NE–SW and strike-slip regime currently active in the Biga Peninsula. Correlation of these structural data with magmatism–mineralization age constraints indicates that the porphyry and HS-epithermal components of the Kirazlı system were emplaced during distinct tectonic periods. This evolution reflects the transition from a post-collisional setting to the current extensional and strike-slip dominated regime of western Anatolia.

How to cite: Çam, M., Kuşcu, İ., and Kaymakcı, N.: Tectono-Magmatic Evolution and Structural Controls on the Kirazlı Porphyry-High Sulfidation Epithermal System, Biga Peninsula, NW Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11195, https://doi.org/10.5194/egusphere-egu26-11195, 2026.

El Chichón is an active volcano in Chiapas, Mexico, that features a hydrothermal system characterized by thermal springs, fumaroles and an acid crater lake. Many studies have focused on tracking the geochemical evolution of its fluids since its last eruption in 1982 and some have specifically aimed to evaluate the geothermal potential.  This work assesses the evolution of the geothermal potential through time using published geochemical data (1983-2025). We use geochemical diagrams, temperatures estimated with geothermometers and water-rock interaction analysis to identify the main system changes that influence the geothermal potential estimations. Given that El Chichón has been considered  a geothermal prospect since the 1980s, we discuss the possible uses of this resource in terms of its recent active seismicity, the risk scenarios and the local socio-cultural context. 

How to cite: Salas Ferman, J. L., Jácome Paz, M. P., Campion, R., Armienta, M. A., and Inguaggiato, S.:  Temporal evaluation of El Chichon´s geothermal potential in the period of 1983-2025. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15407, https://doi.org/10.5194/egusphere-egu26-15407, 2026.

Traditional methods for determining geopotential and height require successive transfers of leveling and gravity measurements, which are prone to error accumulation, face challenges in transoceanic applications, and are generally time-consuming, labor-intensive, and inefficient. Based on the principles of general relativity, an alternative approach using high-precision time-frequency signals to determine geopotential can overcome these limitations. In this study, simulation experiments were conducted to determine geopotential differences using BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer technology. The simulations employed clocks with different performance characteristics, utilizing precise clock offsets and multi-frequency observation data from both systems. The results show that the frequency stability achieved by BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer can reach approximately 3×10⁻¹⁷. The root mean square of the determined geopotential differences corresponds to centimeter-level equivalent height accuracy, and the convergence accuracy of the geopotential difference by the final epoch can reach better than 3.0 m²·s⁻². Given the rapid development of GNSS multi-frequency signals and ongoing improvements in the precision of products such as code and phase biases, geopotential determination based on Galileo and BDS multi-frequency signals is expected to have broader application prospects in the future. This study was supported by the National Natural Science Foundation of China project (No. 42304095), the Key Project of Natural Science Research in Universities of Anhui Province (No. 2023AH051634), the Chuzhou University Research Initiation Fund Project (No. 2023qd07).

How to cite: Xu, W. and Song, J.: Geopotential Difference Determination via BDS and Galileo Multi-Frequency Time-Frequency Signals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15725, https://doi.org/10.5194/egusphere-egu26-15725, 2026.

How well mixed is Earth's mantle? Are there primordial reservoirs? What fraction of the mantle feeds surface volcanism? We attempt to address these questions using large-scale Lagrangian particle tracking in time-reversed and forward convection models. We track particles backward in time using a Back-and-Forth Nudging (BFN) method applied to time-reversed thermal convection, initialized with a present-day seismic–geodynamic–mineral physics model (Glisovic & Forte, 2016, 2025). We likewise carried out long-term (multi-hundred-million-year) forward-in-time mantle convection simulations initialized with present-day mantle structure inferred from tomography. In all cases, we employ mantle viscosity structure that has been independently constrained and verified against a wide suite of present-day geodynamic observables that include free-air gravity anomalies, dynamic surface topography, horizontal divergence of plate velocities, excess core-mantle boundary ellipticity, and glacial isostatic adjustment data. A voxel-based analysis quantifies sampling density, residence time, and flux throughout the mantle.

We use different particle starting conditions, each designed to address a specific aspect of mantle mixing. To identify long-lived isolated regions, we track uniformly distributed particles both forward and backward in time, calculating residence times to locate candidate reservoirs. To estimate the sampling of lower mantle material in the upper mantle, we initialize particles in the D" layer and track them forward to determine what fraction reaches the upper mantle. To address plume dynamics and sampling, we place cylindrical arrays of particles beneath present-day hotspots and track them backward, using the statistical evolution of their standard deviation to quantify mixing along transport pathways, with transit time, and voxel analysis. To measure upper-to-lower mantle exchange, we initialize particles uniformly in the upper mantle. By combining these approaches, we systematically identify regions of low flux and high residence time, candidates for reservoirs. We further take a statistical approach based on voxel density sampling to quantify mixing across the volume of the mantle.

How to cite: Johnston, G., Anderson, M., Forte, A., and Glišović, P.: How Well Is the Mantle Sampled? A Global Voxel-Based Analysis of Residence Time and Flux from Forward- and Reverse-Time Mantle Convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15990, https://doi.org/10.5194/egusphere-egu26-15990, 2026.

Accurate geoid models are essential for converting GNSS-derived heights into physically meaningful elevations and for ensuring consistency in modern height reference systems. This study presents a unified geodetic framework for refining gravimetric geoids using GNSS/leveling residuals through physically interpretable fitting models. Five correction representations are evaluated, ranging from local Cartesian planar surfaces to geodetically consistent spherical formulations of increasing degree. The analysis demonstrates that low-order models effectively remove regional bias and tilt but show limited predictive stability. To enhance robustness, iteratively reweighted least squares is applied to mitigate the influence of outliers while preserving deterministic structure. Higher-order geodetic models are stabilized using ridge regularization, with the regularization strength selected objectively through leave-one-out cross-validation. This strategy ensures numerical conditioning while directly optimizing predictive performance. Results show that the full degree-2 geodetic model offers the best balance among accuracy, stability, and physical interpretability. It reduces long-wavelength distortions while maintaining consistent in-sample and cross-validated performance. The proposed approach supports reliable GNSS-based height determination in modern vertical datum realization and height modernization efforts.

How to cite: Abdalla, A. and Dwira, C.: Geodetic degree-based Models for Robust Regional Geoid Refinement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16148, https://doi.org/10.5194/egusphere-egu26-16148, 2026.

Sulfur released by magmatic activity strongly impacts the climate and is essential for ore mineralisation. Many porphyry systems contain up to billions of tons of sulfur, far exceeding the sulfur capacity of silicate melt and therefore requiring an additional, efficient S‑transfer mechanism.

We present a unique mafic rock (SiO₂ = 53–59 wt.%, MgO = 5.3–7.3 wt.%) containing ~15–20 vol.% anhydrite, ~30–40 vol.% biotite and ~40–50 vol.% plagioclase from the largest porphyry–epithermal system in China. Magmatic anhydrite, indicated by textural relations and LREE‑rich compositions, yields bulk‑rock S contents of ~2–3 wt.%, far above experimental S solubilities.

Plagioclase shows sharp core–rim decreases from An₅₀–₇₀ to An₂₅–₄₅, recording strong CaO depletion caused by sulfate saturation. Extensive sulfate saturation also suppressed amphibole/orthopyroxene and removed a large proportion of LREEs from the melt, producing flat REE patterns in co-crystallised apatite. Biotite exhibits pronounced Ba depletion from core to rim. Because Ba partitions strongly into sulfate melt, not into anhydrite, this Ba zoning is best explained by the formation of a sulfate melt, rather than by crystallisation of anhydrite from a silicate melt.

Nd isotopic compositions (ԑNd(t) ≈ -1.0) indicate that the magma was derived from partial melting of the mantle wedge. We suggest that ascent of this oxidised, sulfur‑rich mafic magma led to decompression-driven oxidation of S²⁻ to S⁶⁺, sulfate saturation, and exsolution of an immiscible sulfate melt. This discrete sulfate‑melt migrated upward and provided an efficient pathway for long‑distance transfer of large amounts of sulfur to porphyry systems. This sulfate‑melt exsolution process is a previously unrecognised mechanism that relaxes the constraint imposed by the sulfur capacity of silicate melt, and LREE‑depleted apatite associated with abundant magmatic sulfate phases may serve as an indicator of sulfate‑melt exsolution and a proxy for porphyry mineralisation potential in the upper crust.

How to cite: Huang, W., Humphreys, M., and Liang, H.: Magmatic sulfate‑melt exsolution as a mechanism for excess sulfur in porphyry systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22040, https://doi.org/10.5194/egusphere-egu26-22040, 2026.

Geomagnetic jerks are the fastest variations we observe in secular variation (SV) of the internal geomagnetic field. They have been deemed spatiotemporally unpredictable, and thus make it difficult to forecast magnetic field changes. Recent core surface flow-inversions of satellite SV data show that pulses in modelled azimuthal flow acceleration are contemporaneous with localised low latitude jerks observed in the Atlantic and Pacific from 2000—2024.

In order to explore to what extent such pulses might be responsible for observed geomagnetic jerks, we simulate them with synthetic flow models. We use a Fisher–Von Mises probability distribution to spatially define the pulse, which ensures that its spherical harmonic expansion in terms of poloidal and toroidal spherical harmonic coefficients converges. To recover a dynamic flow, we add uncorrelated noise to these toroidal and poloidal acceleration coefficients.  After this, we obtain SV from flow acceleration using the diffusionless induction equation, investigating a variety of background flows and core-surface magnetic field structures with our flow-acceleration pulse. Finally, we plot the expected SV at the Earth’s surface.

We successfully generate geomagnetic jerks, similar to those observed by CHAMP in the Atlantic in 2003.5 and 2007, and Swarm in the Pacific in 2017 and 2020. This pulse-like simulator for low-latitude jerks is in agreement with results from numerical dynamo simulations, which suggest that jerks originate from Alfvén wave packets emitted from the inner-outer core boundary. Our results further suggest that there is no need for waves longitudinally propagating along the outer core surface for jerks to occur.

How to cite: Madsen, F., Whaler, K., Brown, W., Beggan, C., and Holme, R.: Geomagnetic jerks as core surface flow acceleration pulses – observations and simulations., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-255, https://doi.org/10.5194/egusphere-egu26-255, 2026.

Heat flux at the Earth’s core-mantle boundary (CMB) partially controls the outer core dynamics and its associated geodynamo. On the mantle side, lateral variations in temperature above the CMB trigger lateral variations in heat flux with low temperature (typically, in and around subducted slabs) and high temperatures (at plumes roots and beneath hot thermo-chemical piles) areas being associated with high and low heat flux regions, respectively. Spatial and temporal variations in temperature are, in turn, controlled by details of mantle convection and mantle material properties. Here, we investigate the influence on CMB heat flux of two key parameters: the excess internal heating within piles of hot, dense material (also referred to as primordial material) modelling the large low shear-wave velocity provinces (LLSVPs) observed by global seismic tomography maps; and the temperature-dependence of thermal conductivity. For this, we perform a series of high-resolution numerical simulations of thermo-chemical convection in spherical annulus geometry using the code StagYY. Importantly, the total heating rate within the mantle is fixed, meaning that an excess heating within piles is balanced by a reduced heat released elsewhere. The initial condition on composition consists in a thin basal layer of chemically denser material, which subsequently evolves into piles of hot, primordial material on the top of which plumes are being generated. Our simulations show that the CMB heat flux is lower than the core adiabatic heat flux throughout the base of primordial material piles, and that it can be locally negative, i.e., heat flows from the mantle to the core. We further investigated the conditions needed for such patches to appear. As one would expect, a larger internal heating excess and a stronger temperature dependence of thermal conductivity both favor the development of negative heat flux patches. However, patches disappear if the piles excess heating gets too large. In this case, heat released in the regular mantle is strongly reduced, allowing plumes generated at the top of piles to extract more heat from these piles. Finally, our simulations predict relatively large CMB heat flux spatial heterogeneity, together with substantial temporal variations in this heterogeneity. Our findings have strong implications for core dynamics. In particular, they support the hypothesis that partial stratification at the top of the core can occur beneath LLSVPs, reconciling geomagnetic and seismic observations. In addition, and based on core dynamics studies, the CMB heat flux heterogeneity and temporal variations predicted by our simulations may play a key role in the occurrence of geomagnetic superchrons.

How to cite: Deschamps, F., Guerrero, J., Amit, H., Terra-nova, F., and Hsieh, W.-P.: Patches of negative core-mantle boundary heat flux: simulations of mantle convection and implications for core dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2141, https://doi.org/10.5194/egusphere-egu26-2141, 2026.

In data assimilation, smoothers improve estimates of the system state by incorporating future observations. However, in geomagnetic data assimilation, the application of smoothers requires solving complex adjoint operators associated with the full nonlinear MHD equations, and the computation of gradients of the objective function is computationally expensive. Here, we employ the ensemble Kalman smoother (EnKS), which exploits ensemble-based statistical correlations across different times and thereby avoids the explicit construction of adjoint operators. We evaluate the performance of EnKS using synthetic observation experiments in moderately nonlinear models and compare it with Ensemble Kalman Filter (EnKF). The results show that both methods recover similar velocity field structures. EnKS exhibits velocity intensities closer to the reference model and performs better in the recovery of the surface flows. However, EnKS is more sensitive to sampling errors, which lead to filter divergence in the magnetic field. We further examine the impact of model error on EnKS, where the model error only arises from variations in viscous effects. The results show that model error causes the loss recovery of some dominant velocity field modes in the recovered solution and ultimately leads to filter divergence. Overall, our results indicate that EnKS can further improve recovery quality in regimes where EnKF already achieves reasonable performance, but may perform worse in regions strongly affected by sampling errors.

How to cite: Zhipeng, Z. and Yufeng, L.: Geomagnetic data assimilation utilizing the ensemble Kalman smoother, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2437, https://doi.org/10.5194/egusphere-egu26-2437, 2026.

Dynamo action in Earth's liquid-iron core has generated a magnetic field for at least 3.4 billion years. Prior the onset of solidification that formed the inner core at about 1 Ga, the energy source driving the geodynamo is unknown. Contemporaneously, the bottom of the mantle may have been fully molten, forming a basal magma ocean. We propose that the boundary between this silicate magma and the immiscible, liquid core was susceptible to tides driven by the Moon’s gravity. We present theoretical predictions for the laminar component of this tidal flow. Our results indicate that a tidal resonance provided enough energy to sustain dynamo action for ~3.5 Gyr by turbulent magnetic induction. Lunar tides may thus have played a key role in generating Earth's ancient magnetic field, which shielded early life from solar radiation.

How to cite: Katz, R. F., Kiernan, M. B. C., Hay, H. C. F. C., Rees Jones, D. W., and Bryson, J. F. J.: Ancient geodynamo driven by lunar tides beneath a basal magma ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2575, https://doi.org/10.5194/egusphere-egu26-2575, 2026.

Slab pull has come to be widely regarded as a dominant driver of plate motions. The nature of slab–plate coupling is typically conceptualised in terms of the Orowan–Elsasser stress-guide model, in which the capacity of the slab to support a differential stress results in a tension-like force transmitted through the subduction hinge, providing an edge force on the trailing plate. Meanwhile, advances in geodynamic modelling now allow subduction to be simulated using increasingly Earth-like constitutive behaviour and, critically, permit the internal force balance to be examined explicitly. While the forces driving tectonic plates on Earth remain debated, the force balance within any given numerical model should be unambiguous.  I discuss results from a vertically integrated horizontal force balance applied to a suite of numerical subduction models. I focus on a particularly useful decomposition that highlights the role of topographic (or gravitational potential energy–related) forces, including ridge push, plate tilting driven by asthenospheric pressure gradients, and—critically—the influence of non-isostatic trench topography. Each of these topographic forces can be expressed in terms of differences in the integrated vertical normal stress - a proxy for the topographic-related pressure gradients in the boundary layer. The trench topographic force,   or trench pull force, is of special interest because it mediates the coupling between predominantly vertical loading imparted by the slab and a horizontal force (pressure gradient) acting on the trailing plate.  Numerical models suggest that a tension-like formulation of net slab pull plays at most a secondary role. Instead, it is primarily through the trench topographic force (trench pull) that the slab induces a net horizontal force on the trailing plate. Numerical models provide a direct means to isolate, compare, and quantify the trench topographic force relative to a tension-like edge force, and to establish quantitative bounds that can guide future analytical investigation of trench topographic forces. 

How to cite: Sandiford, D.: Re-examining Slab Pull: Trench Topography and Trailing Plate Force Balance in Numerical Subduction Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2649, https://doi.org/10.5194/egusphere-egu26-2649, 2026.

Oceanic lithospheric plates form from hot mantle material ascending along the axis of mid-ocean ridges (MORs). As newly formed lithosphere moves away from the ridge, it cools from the surface, leading to progressive deepening of the ocean floor due to thermal contraction and to a decrease in surface heat flow. Turcotte and Oxburgh (1967) proposed a model in which the lithosphere is treated as a cooling half-space with a uniform initial temperature and purely conductive heat transport. Assuming constant thermophysical properties, this model predicts that heat flow and seafloor depth vary linearly with age⁻¹ᐟ² and age¹ᐟ², respectively. Observations of ocean floor topography and heat flow follow these trends up to ages of approximately 50–60 Myr. For older lithosphere, however, the agreement breaks down: observed heat flow is higher and seafloor depth is shallower than predicted by the half-space model.

Several models have been proposed to account for this discrepancy, but all of them are purely kinematic in nature. For example, the widely used “plate model” assumes that temperature is fixed at a certain depth within the mantle. At young ages, the solution coincides with the half-space model, whereas at greater ages it asymptotically approaches the prescribed basal temperature. Although both the basal temperature and the depth of the thermal boundary can be adjusted to fit observations, no known physical mechanism can sustain the boundary condition assumed by this model.

In contrast, we demonstrate that a rheological instability developing within the cooled upper part of the lithospheric plate explains the observations both qualitatively and quantitatively. The key point is that such an instability inevitably arises in a plate cooled from above. Our quantitative analysis is based on experimentally determined non-Newtonian rock viscosity (Hirth and Kohlstedt, 2003) and on the formulation of the Rayleigh number for Arrhenius-type rheology (Solomatov, 1995; Korenaga, 2009). We show that the characteristic Rayleigh number of the instability increases as surface heat flow decreases. Owing to the strong temperature dependence of viscosity, only the lower part of the cooled lithosphere is potentially unstable. For a given heat flow, the thickness of this deformable layer is self-consistently determined by the condition of maximum Rayleigh number. Once the Rayleigh number reaches its critical value, an instability develops that supplies heat to the oceanic lithosphere, inhibits further cooling, and results in the observed flattening of heat flow and seafloor depth records with age.

How to cite: Aryasova, O. and Khazan, Y.: Physics of the flattening of ocean floor depth and heat flow records, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2743, https://doi.org/10.5194/egusphere-egu26-2743, 2026.

The geomagnetic field has undergone hundreds of polarity reversals over Earth's history, at a variable pace. In numerical models of Earth's core dynamics, reversals occur with increasing frequency when the convective forcing is increased past a critical level. This transition has previously been related to the influence of inertia in the force balance. Because this force is subdominant in Earth's core, concerns have been raised regarding the geophysical applicability of this paradigm. Reproducing the reversal rate of the past million years also requires forcing conditions that do not guarantee that the rest of the geomagnetic variation spectrum is reproduced. These issues motivate the search for alternative reversal mechanisms. Using a suite of numerical models where buoyancy is provided at the bottom of the core by inner-core freezing, we show that the magnetic dipole amplitude is controlled by the relative strength of subsurface upwellings and horizontal circulation at the core surface. A relative weakening of upwellings brings the system from a stable to a reversing dipole state. This mechanism is purely kinematic because it operates irrespectively of the interior force balance. It is therefore expected to apply at the physical conditions of Earth's core. Subsurface upwellings may be impeded by stable stratification in the outermost core. We show that with weak stratification levels corresponding to a nearly adiabatic core surface heat flow, a single model reproduces the observed geomagnetic variations ranging from decades to millions of years. In contrast with the existing paradigm, reversals caused by this stable top core mechanism become more frequent when the level of stratification increases i.e. when the core heat flow decreases. This suggests that the link between mantle dynamics and magnetic reversal frequency needs to be reexamined.

How to cite: Aubert, J., Landeau, M., Fournier, A., and Gastine, T.: Core-surface kinematic control of polarity reversals in advanced geodynamo simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3465, https://doi.org/10.5194/egusphere-egu26-3465, 2026.

The thermal conductivity of iron and iron alloys play a key role in determining how telluric planetary cores cool over time. The thermal conductivity of core-forming alloys is needed to establish the heat budget for core and mantle processes. This budget in turn controls the characteristics of core and mantle dynamics, as well as the geologic timescales over which they are active. However, there is little consensus on the effect of composition on the thermal conductivity of iron at conditions relevant to planetary interiors. Here I present the results of recent experimental investigations to understand how the thermal conductivity varies for iron and iron alloys varies at extreme pressures and temperatures, providing quantitative insight into the transport properties of core-forming alloys.

How to cite: Edmund, E.: Thermal Conductivity of Iron and Iron Alloys at Planetary Core Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3504, https://doi.org/10.5194/egusphere-egu26-3504, 2026.

Sub-plate mantle flow traction (MFT) has been considered as a major driving force for plate motion; however, the force acting on the overlying plate is difficult to constrain. One of the reasons lies in the variable rheological flow laws of mantle rocks, e.g. linear versus power-law rheology, applied in previous studies. Here, systematic numerical models are conducted to evaluate MFT under variable rheological, geometrical and kinematic conditions. The results indicate that MFT with power-law rheology is much lower than that with linear rheology under the same mantle/plate velocity contrast. In addition, existence of a lithospheric root in the overlying plate could enhance MFT, where integrated normal force acting on the vertical walls of lithospheric root is much lower than the shear force in a large-scale domain. In a regime of several thousand kilometers, MFT with power-law rheology is comparable to the ridge push of about 3×10¹²N/m, whereas that with linear rheology is comparable to the slab pull of about 3×10¹³ N/m. The roles of MFT in driving plate motion are further analyzed for the Tethyan evolution. It indicates that MFT with power-law rheology could partially support the cyclic Wilson cycles experienced in the Tethyan system, whereas that with linear rheology could easily dominate any kinds of plate tectonic evolutions. The quantitative evaluation of MFT in this study clarifies the roles of rheological flow laws on MFT and could help to better understand the contrasting results in previous numerical studies.

How to cite: Cui, F., Li, Z.-H., and Fu, H.-Y.: Quantitative evaluation of mantle flow traction on overlying tectonic plate: Linear versus power-law mantle rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3641, https://doi.org/10.5194/egusphere-egu26-3641, 2026.

Subduction is considered the primary driver of plate tectonics, which is sometimes accompanied by back-arc spreading. Back-arc deformation on Earth exhibits substantial variability, ranging from compressional regimes in the Japan Sea to rapid spreading with rates up to 15 cm/yr in the Lau Basin. Even within a single subduction zone, back-arc basins can exhibit significant spatial and temporal variability in spreading rates along the trench. The mechanisms underlying this variability remain inadequately understood. To address this issue, we compiled global back-arc deformation rates and quantified slab area penetration into the deeper mantle. Additionally, we conducted a series of numerical simulations to elucidate the factors that govern back-arc deformation rate. Our global back-arc compilation and numerical models reveals a robust negative correlation between back-arc spreading rate and slab penetration into the deeper mantle, highlighting the initial stage of subduction as the peak phase of back-arc spreading. Furthermore, numerical simulations offer insights into the underlying dynamic mechanisms, demonstrating that slab-driven poloidal flow play a dominant role in governing back-arc deformation rates.

How to cite: Jian, H.: Evolution of slab-driven poloidal flow symmetry governs back-arc deformation rates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3957, https://doi.org/10.5194/egusphere-egu26-3957, 2026.

Small-scale lateral heterogeneities at the lowermost mantle are fundamental to understanding mantle convection dynamics and core-mantle interactions. PKP precursors, generated by seismic scattering from fine-scale structures near the core-mantle boundary (CMB), provide a powerful yet underutilized probe for imaging deep Earth heterogeneities. However, the manual identification of these weak signals is inefficient, subjective, and inadequate for the vast volumes of modern seismic data.
We present a comprehensive analysis of global PKP precursor observations using a supervised deep learning framework combined with iterative human-guided optimization. Processing over 2 million vertical-component waveforms from earthquakes (Mw ≥ 6.0) recorded between 1990 and 2024, we automatically identified 227,770 high-quality PKP precursor signals—an order of magnitude increase compared to previous global compilations. This unprecedented dataset, termed DeepScatter-PKP, provides the densest and most spatially complete observational foundation for characterizing CMB scattering structures to date.
To systematically evaluate the stability and spatial distribution of scattering signals, we developed a dual-probability framework integrating precursor occurrence probability (Pocc) and scatterer location probability (Pscat). This approach enables simultaneous assessment of broad-area scattering stability and precise localization of strong scatterers. Our significantly enhanced sampling density and coverage connect previously isolated scattering patches into continuous anomaly belts, notably beneath the Pan-American region and the western Pacific margin.
Cross-validation with independent seismic phases confirms the robust embedding of multiple ultra-low velocity zones (ULVZs) within diverse velocity heterogeneity backgrounds, suggesting thermochemical origins involving remnants of multi-episode subducted slabs, partial melting, and interactions with large low-velocity provinces (LLVPs). Extension to undersampled regions reveals six previously unidentified high-potential strong scattering zones, including beneath the South Atlantic, high-latitude Eurasia, and circum-Antarctic domains.
Our results demonstrate that small-scale scatterers occur in both high-velocity and low-velocity domains, highlighting the diversity and independence of their origins beyond LLSVP boundaries. The DeepScatter-PKP dataset and dual-probability framework establish priority targets for future multi-phase joint inversions and high-resolution CMB imaging, offering new constraints on the thermochemical state and dynamic evolution of Earth's deep interior.

How to cite: Guan, Y., Li, J., Xiao, Z., Wang, W., and Xu, T.: Global Mapping of Small-Scale Heterogeneities at the Core-Mantle Boundary: Insights from Deep Learning Analysis of PKP Precursors, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4040, https://doi.org/10.5194/egusphere-egu26-4040, 2026.

Lithospheric uplift, once attributed mainly to plate tectonic and isostatic processes, is now recognized to be strongly influenced by convective processes in the Earth's mantle. Advances in satellite observations and data analysis have strengthened geodetic constraints on geodynamic models, specifically through satellite gravimetry. However, the superposition of mass change signals driven by different Earth processes requires robust signal separation to quantify the contributions of individual processes in the data.

Signal separation is a fundamental challenge in geodetic datasets, which commonly represent the superposition of multiple physical signals. Previous studies have explored isolating solid-Earth signals due to glacial isostatic adjustment (GIA) ^[1] applying a neural network–based signal separation method to simulated temporal gravity data. The neural network (NN) was trained to recognize and separate individual signal components by exploiting prior knowledge about their characteristic spatiotemporal behavior, derived from forward-modeled time-variable gravity data and additional constraints.

The employed NN architecture is a multi-channel U-Net designed to separate superimposed temporal gravity signals arising from mass redistribution in the atmosphere and oceans, continental hydrosphere, cryosphere, and solid Earth. The network separates these combined inputs into their constituent sub-components. The framework is generally applicable to signal separation in any three-axis dataset (e.g., latitude, longitude, and time), using a sampling strategy in which the data are partitioned along one axis to determine the optimal two-axis combination for training ^[2].

This work presents progress towards extracting signals originating from deep-Earth processes, particularly mantle convection signals, from time-variable gravity data such as observed by the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow on (GRACE-FO) satellite missions. In this context, NN-based signal separation has been demonstrated primarily for signals with comparably large amplitudes. In contrast, time-variable gravity signals caused by processes in the Earth's mantle are approximately three orders of magnitude weaker than signals related to surface processes, rendering their detection and separation particularly challenging. The current study therefore focuses on enhancing sensitivity to low-amplitude mantle signals by leveraging the ability of machine learning methodologies to learn subtle spatiotemporal patterns.

For application to real data from the GRACE/-FO missions or the upcoming Mass-Change and Geosciences International Constellation (MAGIC), we propose training the framework on representative forward-modeled signals and simulated noise and subsequently applying the trained separation model to observational time-variable gravity data.

References:

• Heller-Kaikov B, Karimi H, Lekshmy Raj D, Pail R, Hugentobler U, Werner M. 2025 Signal separation in geodetic observations: satellite gravimetry. Proc. R. Soc. A 481: 20240820.
• Heller-Kaikov B, Pail R, Werner M. 2025, Neural network-based framework for signal separation in spatio-temporal gravity data Computers & Geosciences, Volume 207, 2026, 106057, ISSN 0098-3004.

How to cite: Lekshmy Raj, D., Pail, R., and Heller-Kaikov, B.: Signal separation of temporal gravity signals for low-amplitude signal detection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4065, https://doi.org/10.5194/egusphere-egu26-4065, 2026.

Seismic tomography provides critical insights into Earth’s evolution, yet the origin of deep-mantle seismic velocity anomalies—particularly slow anomalies—remains debated. Here we constrain the nature of the slow anomalies within the mantle transition zone (MTZ) beneath eastern North America by quantifying their dynamic impact on continental-scale drainage evolution and offshore sedimentation since the Miocene using coupled mantle–surface process modeling. We show that reproducing the observed stability of the Mississippi River basin, the long-term subsidence of the eastern North American margin, and the sedimentary record of the Gulf of Mexico requires a dynamic-topography scenario consistent with neutral net buoyancy of these slow anomalies. Independent geophysical observations further support this interpretation: the MTZ slow anomalies spatially correlate with the remnant Farallon slab within the lower mantle, and coincide with regions of elevated electrical conductivity. This implies that the slow seismic anomalies beneath eastern North America are best explained by hydratedcompositional heterogeneity associated with long-lived Farallon subduction, rather than by a purely thermal origin. Our results further support regional buoyancy compensation, in which dense melts above the MTZ are offset by buoyant hydrous and/or thermal contributions, yielding neutral buoyancy at long wavelengths despite strong seismic velocity reduction. Finally, the predicted trajectories of subducted slabs and mantle flow from data assimilation models indicate that the MTZ slow anomalies mostly likely represent dehydration of the Mesozoic Farallon slab within the lower mantle, providing a long-lived source ofmantle volatile circulation.

How to cite: Jin, X., Liu, L., Cao, Z., Dong, H., Yang, R., Anders, A. M., and Gao, C.: Stable continental-scale drainage of North America reveals hydrated upper mantle anomaly due to long-lived oceanic subduction , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4320, https://doi.org/10.5194/egusphere-egu26-4320, 2026.

I present the results of a series of numerical experiments, based on a visco-elasto-plastic rheological model of the lithosphere, aimed at studying the interplay between mantle convection and tectonic processes at continental margins. In these experiments, the reference thermal states of the oceanic and continental lithospheres are described by a plate cooling model and by the solutions of the steady heat equation, respectively, while a small non-adiabatic temperature gradient is assumed for the asthenosphere and transition zone. The resulting thermo-mechanical model incorporates both vertical (Rayleigh-Benard) and horizontal (small-scale) convection and allows to predict the state of stress across continental margins, as well as some tectonic processes that are observed in these regions. Small-scale convection arises from lateral temperature gradients. It always develops along passive margins, where the thermal regime of the oceanic lithosphere meets the downward-dipping isotherms of the continental lithosphere. This form of horizontal convection has the potential to deform the lower part of the continental lithosphere, generate Rayleigh-Taylor instabilities, and produce up to ~50 MPa of compressional stress across continental margins. The formation of Rayleigh-Taylor instabilities is accompanied by lithospheric thinning, which in turn induces negative thermal anomalies that contribute to the maintenance of isostatic equilibrium by increasing the density of the residual lithosphere. These anomalies propagate towards the interior of the continental lithosphere, until the increased rheological strength associated with lower temperatures is sufficient to prevent further delamination. Therefore, the lower continental lithosphere is always colder than predicted by steady-state solutions of the heat equation. Basal landward traction along passive margins, resulting from small-scale convection, is further enhanced when the oceanic lithosphere adjacent to the continental margin is bounded by a spreading ridge. In this instance, numerical experiments consistently show the existence of an active spreading component, up to 5 mm/yr, which generates additional traction below the continental margins and contributes to a compressive stress regime in these regions. Consequently, a net horizontal landward push develops along the continental margins of a tectonic plate, which combines with other driving forces to determine the plate kinematics. Finally, numerical experiments show that non-adiabatic vertical temperature gradients drive the formation of Rayleigh-Benard convective cells with a wavelength of 600-700 km and a height 500-600 km.

How to cite: Schettino, A.: Sea-floor spreading, small-scale convection, and passive margins: Interplay and effect on the driving forces of Plate Tectonics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4362, https://doi.org/10.5194/egusphere-egu26-4362, 2026.

Dynamic topography is a crucial geodynamic observable that emerges as a consequence of flow in the mantle. Buoyancies associated with mantle convection induce vertical deflections at the Earth's surface. Negative surface deflections create depositional environments and allow sedimentation to occur, while positive surface deflections create erosional/non-depositional environments, that induce gaps (hiatuses) in the geological record. The temporal and spatial extent of these gaps can be mapped using geological maps and regional studies, thus providing a means of tracking mantle processes through geological time.
Here, we compare a manual and digital extraction of hiatus distributions in China. We utilise a manually compiled dataset of un/conformable contacts and compare it to a digital contact extraction using the recently published digital geological map of China. The digital approach is limited to surface data, whereas the manual approach allows the utilisation of subsurface information. We find that the digital approach is substantially faster than the manual extraction. Our results indicate that the optimal methodology combines digital processing with refinement of manual subsurface information. Furthermore, we observe that mapping the absence and presence of a geological series shows very similar results when processed using either approach. The current limitation to a wider application of this approach is the limited availability of digital geological maps. A standardised digital database of geological maps enhanced with subsurface information (i.e., covered geological maps) is necessary to promote the use of geological data within the wider Earth science community, and would increase the opportunities for interdisciplinary collaboration.

How to cite: Vilacís, B., Carena, S., Hayek, J. N., Robl, G., Bunge, H.-P., and Ma, J.: Mapping geological hiatus using a manual and a digital approach: A case study from China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4939, https://doi.org/10.5194/egusphere-egu26-4939, 2026.

The Earth’s inner core is made of a solid iron alloy. Seismic observations suggest a structure and an anisotropy which leads to variations in both the velocity and the attenuation of the seismic waves. Attenuation is the loss of energy during the propagation of the seismic waves. Whether this attenuation arises from intrinsic properties of the iron alloys or extrinsic origins remains an open question. In this context, studying attenuation in metallic alloys could help improving our knowledge about the physical properties and the geodynamic of the inner core.

Extrinsic attenuation is linked to external environment that impact the wave propagation, such as scattering or heterogeneities. Intrinsic sources are related to the properties of the material itself such as its viscoelastic behavior. This work focuses on the latter and particularly on the anelastic relaxation, which is one of the sources of internal friction.

In this work, we seek to understand attenuation mechanisms in metals at high temperature. The experiments are conducted on a dynamic mechanical analysis (DMA) instrument with control of temperature and oxygen fugacity albeit at ambient pressure. We use a Mg alloy as analogous material to that of the inner core, which presents similar crystallographic structure and is expected to behave the same way.

Here, we will present some results and hypotheses derived from temperature, frequency, and strain sweeps realized with DMA. These analyses allow us to investigate viscoelastic values like internal friction, storage and loss modulus at different conditions. Results show a temperature-dependent behavior that can be related to the underlying mechanisms. Scanning electron microscopy analyses (electron back scattered diffraction) were performed to further assess the attenuation mechanisms involved in our experiments. Grain size, texture or grain boundaries were analyzed to understand our analogous material. These experiments are led in conditions which could allow us to discuss attenuation in the inner core.

How to cite: Carin, L., Manda, S., Kolesnikov, E., Chantel, J., Hilairet, N., and Merkel, S.: First results for experiments on inner core attenuation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5753, https://doi.org/10.5194/egusphere-egu26-5753, 2026.

The majority of metallic materials exhibit viscoelastic or anelastic behavior when subjected to elastic cyclic loading under specific temperature and frequency conditions. This anelastic nature is commonly characterized by the dissipation or loss of mechanical energy, manifested as a hysteresis loop between stress-strain signals. The energy loss is quantified by the loss tangent (tanδ) or the inverse of quality factor (Q^-1). The origin of this dissipation is associated with internal variables, particularly the microstructure, and this phenomenon is referred to as internal friction. The microstructures are inherently complex, and their overall response is governed by multiple factors such as solute type and content, crystallographic texture, dislocation density, residual stresses, and grain boundary characteristics. Consequently, any modification in microstructure directly influences the internal friction behavior. Additionally, the operating temperature and imposed frequency strongly affect the magnitude of  tanδ. This work provides a comprehensive summary of the role of microstructural parameters on the viscoelastic behavior of various metals over a wide range of length and time scales and over an extensive temperature range.

Subsequently, the understanding of internal friction in metallic materials is extended to the earth’s inner core. It is well established that inner core exists under extreme conditions, with very high temperatures (~5700 K) and extremely high pressures (~330 GPa). Under such conditions, reliable estimates of seismic wave dissipation or attenuation are not readily available. At same time, the underlying mechanisms governing seismic wave propagation remain unclear. This study provides a summary and proposes plausible attenuation mechanisms in the earth’s inner core over a range of testing conditions. These are supported by dynamic mechanical analysis (DMA) experiments and atomistic simulations. 

How to cite: Manda, S., Carin, L., Kolesnikov, E., Chantel, J., Hilairet, N., and Merkel, S.: Understanding Relaxation Mechanisms in Metals: Application to Earth’s Inner Core , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5754, https://doi.org/10.5194/egusphere-egu26-5754, 2026.

The origin of the two large low-velocity provinces (LLVPs) remains debated today. The debate has often focused on their density, which can provide us insight into their origin. For example, if LLVPs were long-lived features, they would require a higher intrinsic density (the difference in density to the background mantle under the same temperature and pressure) than their surroundings to negate their positive thermal buoyancy and to remain physically stable at the base of the mantle for billions of years. Better constraints on the origin of LLVPs would provide further insight into dynamic processes at the lower boundary of the mantle. This has implications for how the deep mantle impacts Earth’s surface.

Long-wavelength observations of the geoid and core-mantle boundary (CMB) topography are particularly sensitive to the lowermost mantle. These observables have therefore been used to infer the density of LLVPs, often attributing a higher intrinsic density, if any, to chemical heterogeneity. Yet, many of these studies have not jointly considered the effects of chemical composition with the transition from bridgmanite to post-perovskite on lowermost mantle density. This phase transition is associated with a 1-2% increase in density, but occurs primarily in cold regions, thus impacting the amplitude and spatial patterns of the geoid and CMB topography. Therefore, the presence of post-perovskite can affect inferences of LLVP chemical composition and density from geodetic observables. It is therefore important to take the presence of post-perovskite into account when inferring LLVP density and chemical composition from geoid and CMB topography observations.      

Here, we investigate the geodetic signatures expected from a range of scenarios related to the distribution of post-perovskite within different models of lowermost mantle temperature and composition. We calculate synthetic density fields from existing temperature and compositional fields as predicted by geodynamic simulations and a recent thermodynamic database. These density fields are then convolved with kernels derived from models of instantaneous mantle flow to obtain synthetic geodetic observables. We show that the effect of a higher post-perovskite density alone produces a comparable effect to chemical heterogeneity on the geoid and CMB topography. This implies that the effects of post-perovskite need to be taken into account when modelling dynamic processes and inferring physical properties in the deep mantle.

How to cite: Leung, J., Walker, A. M., Koelemeijer, P., and Davies, D. R.: Implications of post-perovskite on the density of lowermost mantle structures based on geoid and core-mantle boundary topography observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5779, https://doi.org/10.5194/egusphere-egu26-5779, 2026.

Understanding the stable phase of iron under Earth's inner core conditions is fundamental to interpreting its composition, evolution, and dynamics. Despite its importance, the stability of candidate phases (e.g., bcc, fcc, hcp) remains contentious due to the extreme pressure-temperature conditions and the meagre free energy differences (~10 meV/atom) between them. This has resulted in conflicting predictions from ab initio, force field, and machine learning approaches. To resolve this discrepancy, we introduce a Bain-path thermodynamic integration (BP-TI) method that directly computes free energy differences from the work performed by internal stress along a transformation path. This approach eliminates the need for an external reference system and avoids the uncertainties associated with conventional entropy calculations. Applying this rigorous benchmark with strict convergence criteria, we find that hcp Fe is the thermodynamically stable phase with the highest melting temperature under inner core conditions. In contrast, bcc Fe is consistently shown to be metastable across all tested interatomic potentials and computational methods. This metastability is intrinsic, persisting independent of simulation cell size and thus is not a finite-size artifact. Our findings reconcile previous disparities and provide a robust thermodynamic foundation for future studies of inner-core properties and dynamics.

How to cite: Yang, H., Wan, L., Li, Y., Vočadlo, L., and Brodholt, J.: Resolving the Iron Phase Stability Debate in Earth's Inner Core: A Consistent Thermodynamic Benchmark, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6077, https://doi.org/10.5194/egusphere-egu26-6077, 2026.

Seismic data from the InSight mission reveal that Mars possesses a structure comprising a crust, mantle, and core, with recent studies indicating the existence of a solid inner core. While the composition of the inner core of Mars remains unclear, but some scholars argue that it might be FeO and/or Fe₃C. Here, the thermoelastic properties of high‑spin antiferromagnetic B1‑phase FeO was derived from first‑principles calculations, and the composition of the core was inverted by combining with the previous experimental data. Additionally, the possible light element components in the Martian outer core have also been restricted. These results provide a new starting point for the composition of the Martian core and might have implications for understanding the chemical composition and magnetic evolution of the Mars.

How to cite: Pan, Z., Wang, W., and Wu, Z.: High‑Spin Antiferromagnetic B1‑Phase FeO: Implications for the Martian Inner core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6533, https://doi.org/10.5194/egusphere-egu26-6533, 2026.

Iron content in the lower mantle significantly influences mineral density and mantle convection dynamics. Electrical conductivity, an important physical property of minerals and rocks, is highly sensitive to iron content. Ground-based and satellite geomagnetic observations reveal radial and lateral variations in electrical conductivity in the lower mantle, where some conductive anomalies are up to one order of magnitude higher than the ambient mantle. However, the poorly understood quantitative correlation between iron content and electrical conductivity hinders our ability to decipher the composition of the lower mantle. We systematically measured the electrical conductivity of Al-bearing bridgmanite, the most abundant mineral in the lower mantle, as a function of iron content (X_Fe= 0.1–0.37) at 27 GPa and temperatures up to 2000 K, corresponding to conditions in the uppermost lower mantle. Our results demonstrate that bridgmanite conductivity increases substantially with iron content while exhibiting minimal temperature dependence. This remarkable sensitivity of bridgmanite conductivity to iron content enables us to constrain the iron content of the lower mantle through geomagnetic observations.

How to cite: Han, K., Özaydın, S., Fei, H., Man, L., Wang, F., Chanyshev, A., Withers, A., Grayver, A., and Katsura, T.: Constraining iron content in the lower mantle through electrical conductivity of bridgmanite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6558, https://doi.org/10.5194/egusphere-egu26-6558, 2026.

High-frequency seismic scattered waves provide unique sensitivity to small-scale heterogeneity in the lowermost mantle and at the core mantle boundary (CMB), but their interpretation is challenged by wavefront healing and the huge cost of full-waveform simulations at frequencies above about 1 Hz. We evaluate the precision of radiative transfer equation (RTE) modelling compared with wave equation (WE) modelling to establish a basis for future coupled RTE-WE approaches to high-frequency seismic scattering at the CMB.

We have used the RTE based on the Monte Carlo method to efficiently simulate the global transport of seismic energy with a 1D spherical symmetrical model and reproduced scattered waves, such as PKP precursors and Pdiff coda. Now, WE simulations are employed in localised CMB domains to resolve deterministic wave structure interactions, including scattering, interference, and diffraction. Forward models are constructed from the CMB and D” layer, including layered structures, CMB topography, ultra-low velocity zones, and distributed volumetric heterogeneity. We analyse full waveform simulations in terms of their associated energy distributions and envelopes, and explore how these waveform-derived quantities can be related to seismic intensities modelled by RTE under different structural cases. This framework provides a way toward coupling RTE simulations with WE modelling in further studies, enabling detailed investigation of CMB structure using localised wave equation modelling while substantially reducing the computational cost of global high-frequency simulations.

How to cite: Zhang, T. and Sens-Schönfelder, C.: High-Frequency Seismic Scattering at the Core Mantle Boundary: Insights from Radiative Transfer Equation and Wave Equation Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7762, https://doi.org/10.5194/egusphere-egu26-7762, 2026.

The emergence of plate-like surface motion in self-consistent mantle convection models is a key behaviour requiring detection in numerical experiment results featuring terrestrial characteristics. However, the identification and verification of candidate plates is a challenging task, in practice. On Earth, narrow divergent, convergent, and strike-slip plate boundaries as well as regions exhibiting widespread diffuse deformation, comprise roughly 10 to 20% of the lithosphere that does not adhere to rigid body motion. Accordingly, the detection of candidate plates must be performed in light of the existence of diffuse deformation occurring regularly as a tectonic characteristic. To address this challenge, we have recently developed a new plate detection tool, `platerecipy`, that utilizes the Random Walker (RW) segmentation algorithm to identify candidate plates in both mantle convection model output as well as global geophysical data sets and terrestrial measurements. We describe how the discrete probability solution arising from RW can be used to both assess confidence in the association of each location with a distinct rigid plate, and to identify diffuse surface regions. Furthermore, we show how utilizing the RW probabilities can significantly improve Euler vector inversion for fitting the plate motion as a probability field allows for a systematic means of incorporating uncertainties inherent to the plate detection process. We demonstrate the effectiveness of our method by applying it to the surface of a mantle convection model and a terrestrial strain-rate dataset. We show how our findings can be used for an Euler vector inversion that allows plate rigidity analysis.

How to cite: Javaheri, P. and Lowman, J.: Implementing Platerecipy: an open access tool utilizing a graph theory method for detecting tectonic plate boundaries in geophysical data sets and numerical model output, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8360, https://doi.org/10.5194/egusphere-egu26-8360, 2026.

Mantle convection models are of utmost importance in understanding the physics governing major geological processes of our planet such as earthquakes, mountain building, etc. The TerraNeo framework is focussed on creating extreme-scale high-resolution geodynamic models which it achieves
with the massively parallel matrix-free finite element package HyTeG. To handle the Stokes system which arises from the conservation of mass and
momentum equations, a multigrid preconditioned Krylov subspace solver is used, whereas to handle the advection term in the conservation of energy
equation, an operator splitting approach based on the modified method of characteristics (particles) is used.

We first present standard numerical benchmark experiments for geodynamic validation of the framework against other community codes. In addition, we verify order of convergence of error in velocity and pressure against highly accurate solutions for the Stokes system computed with the propagator matrix method for radially varying viscosity and density cases. Next, a mantle circulation model with spatially varying physical parameters (viscosity and density) and assimilated plate velocities is simulated from a past physical state to present day and assessed for geodynamic correctness. Finally, we present scalability studies performed on the supercomputer SuperMUC-NG Phase 1 at LRZ (91st in TOP500, Nov’ 25). In these experiments, we were able to scale the framework to a global model resolution of ≃ 7.5 km on > 300, 000 MPI processes. These results combined with the numerical benchmarking of the framework clearly show that TerraNeo is well suited for creating large-scale geodynamic models.

How to cite: Ilangovan, P., Robl, G., Rezaei, F., Vilacis, B., Burkhart, A., Kohl, N., Mohr, M., and Bunge, H.-P.: Geodynamic Validation and Scalability of TerraNeo: Matrix-Free Mantle Convection Framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8727, https://doi.org/10.5194/egusphere-egu26-8727, 2026.

Cratons such as the Guiana Shield are often considered as stable regions, undergoing long-term emergence and denudation due to buoyancy. However, by integrating geological and geomorphological observations with apatite fission-track analysis, we define a history involving repeated episodes of burial and exhumation over the last 500 Myr.

Over much of the shield, the thermal history is dominated by the effects of earliest Jurassic magmatism, followed by Early Cretaceous exhumation coincident with the onset of seafloor spreading in the southern South Atlantic when South America was driven westward by mantle flow from the hot, upwelling upper mantle in the southeast toward the downwelling, pre-Andean subduction zone in the west.

Further episodes of regional exhumation occurred in Aptian-Albian time coincident with a global-scale plate reorganization and in Eocene times coincident with a slowdown in the movement of the South American plate. Results from the Amazon Basin also define these four episodes.

Thermal data from a deep well in the Amazon Basin show that the Early Cretaceous and Eocene exhumation episodes were preceded by burial by kilometre-scale thicknesses of cover, subsequently removed. Continuity of data from basin to shield suggests that burial extended across the shield. Early Cretaceous exhumation led to formation of a base-Cretaceous peneplain across the entire continent, from the Andes (during post-orogenic collapse) to the Amazon Basin and the Guiana Shield. This peneplain was then buried beneath Cretaceous–Paleogene sediments prior to the onset of Eocene exhumation, which also extended into in the offshore. The Eocene episode also correlates with post-orogenic collapse of the Andes.

Miocene exhumation correlates with a regional, late Miocene unconformity, onshore and offshore, coincident with a slowdown in the movement of the South American plate. This episode resulted in the formation of a vast coastal planation surface, along the Guyanas Atlantic margin and in the incision of the present-day valley along the Amazon River, leading to the reversal of the Amazon River.

The history of repeated burial and exhumation defined for the Guiana Shield appears to be a common property of supposedly stable cratons. The correlation between Andean tectonics, episodes of exhumation and changes in the motion of the South American plate, shows that sub-lithospheric forces and intra-plate stress governed the vertical movements across the continent.

References

Baby et al., 2025. The Northern Central Andes and Andean tectonic evolution revisited: an integrated stratigraphic and structural model of three superimposed orogens. Earth Sci. Rev. https://doi.org/10.1016/j. earscirev.2024.104998

Japsen et al., 2025. Ups and downs of the Guiana Shield and Amazon Basin over the last 500 Myr. Gondw. Res. https://doi.org/10.1016/j.gr.2025.06.020

Stotz et al., 2023. Plume driven plate motion changes: New insights from the South Atlantic realm. J. S. Am. Earth Sci. https://doi.org/10.1016/j.jsames.2023.104257

Szatmari & Milani, 2016. Tectonic control of the oil-rich large igneous-carbonate- salt province of the South Atlantic rift. Mar. Pet. Geol. https://doi.org/ 10.1016/j.marpetgeo.2016.06.004

How to cite: Japsen, P., Green, P. F., and Bonow, J. M.: Ups and downs of the Guiana Shield and Amazon Basin driven by sub-lithospheric forces and intra-plate stress, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8912, https://doi.org/10.5194/egusphere-egu26-8912, 2026.

How to cite: Bott, J., Scheck-Wenderoth, M., May, T., and Cacace, M.: Upper Mantle Controls on the Phanerozoic Evolution of Western and Central Europe , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9286, https://doi.org/10.5194/egusphere-egu26-9286, 2026.

The Hawaiian–Emperor Seamount Chain (HESC) is the longest volcanic island chain in the world, which is formed by the thermal erosion of the Pacific Plate by a hot mantle plume. The HESC has two major characteristics. First, it features an approximately 60° bend formed around 47 million years ago (Ma), giving rise to its distinctive geometry. Second, over the past ~2 million years (Myr), the HESC has developed into two sub-parallel Loa-Kea trends that exhibit markedly different incompatible element and isotopic signatures, resulting in its distinctive geochemical characteristics. The causes of the two features remain vigorously debated. Here, we use global-scale geodynamic models to investigate their formation mechanisms. We find that intra-oceanic subduction systems existed in the North Pacific from the Jurassic to the Eocene, exerting significant influences on Pacific Plate motion and the thermo-chemical evolution of the Hawaiian plume from its generation at the Large Low–Velocity Provinces (LLVPs), to its drift beneath the plate, and finally its structural evolution throughout the mantle.
We quantitatively resolve the relative contributions of Pacific Plate rotation and Hawaiian hotspot drift to the formation of the Hawaiian-Emperor Bend (HEB). We propose that the demise of the Kronotsky intra-oceanic subduction system was the primary driver of a major rotational reorganization of the Pacific Plate at ~47 Ma, which our numerical simulations quantify as a ~30° rotation. Using global mantle convection models, we successfully reproduce the slab structures, the basal thermochemical anomalies including the LLVPs and an intermediate-scale anomaly (the Kamchatka anomaly) beneath the northwestern Pacific, and more importantly the present-day location of the Hawaiian hotspot. Our model predicts a predominantly southwestward migration of hotspot over the past ~80 Myr. This hotspot trajectory is consistent with plate kinematic constraints, but differs substantially from those of earlier geodynamic models that predict a predominantly southward or southeastward hotspot motion. We find the westward component of the hotspot motion is crucial for the formation of HEB. Further analysis suggests that an Late Jurassic-Cretaceous intra-oceanic subduction system in the northeast Pacific provided the forcing necessary to drive this westward hotspot migration. Combined with modeled Pacific Plate motion, we have fully reproduced the observed ~60° HEB. Furthermore, subduction activity in the North Pacific influenced the structural evolution of the Hawaiian plume, triggering a bottom-up splitting of the plume conduit. This splitting generated internal material zoning, which is expressed at the surface as parallel Loa–Kea geochemical trends. These findings not only explain the geometry and geochemistry of the HESC, but also provide insights on the tectonic evolution of the North Pacific.

How to cite: Zhang, J. and Hu, J.: Geometry and Geochemistry of the Hawaiian–Emperor Seamount Chain reproduced by global plate-mantle coupling geodynamic models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9615, https://doi.org/10.5194/egusphere-egu26-9615, 2026.

We derive global stress fields through time using an analytical asthenospheric flow estimation that involves plate motions, subduction geometry, and time-variable plume flux. Among these, the most effective way to drive rapid regional stress changes in the continents is by varying plume flux, especially when more than one plume is present, as is the case for Europe. We apply our paleostress model to the case study of western Europe, a region that experienced rapid, substantial, and large-scale lithospheric stress changes in the Late Mesozoic and Cenozoic. We find that the behaviour of pressure-driven asthenosphere flow, resulting from variations in plume flux, dominates the rapidly temporo-spatially varying stress signal. Given the potential causes of stress change in this particular region, we further interpret the tectonic changes in the context of dynamic topography as expressed by the stratigraphic record, shifts in plate motion, paleostress indicators, and past interpretations of the tectonic evolution of Europe. Through this approach we move away from the paradigm of stress changes being driven by plate-boundary or body forces in the lithosphere, and emphasize the active role of the mantle and the importance of interpreting models in relation to multiple process-linked observations.

How to cite: Bunge, H.-P., Hayek, J. N., Stotz, I. L., Kahle, B., and Vilacis, B.: Plume-driven rapid paleo stress field changes in western Europe since Mid-Cretaceous inferred from analytic upper mantle flow models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9724, https://doi.org/10.5194/egusphere-egu26-9724, 2026.

Stratigraphic evidence shows the presence of an unconformity starting at 68 Ma (Maastrichtian) in the Canadian archipelago, on- and off-shore west and north Greenland, in Svalbard, on the Lomonosov Ridge, in East Greenland, on- and off-shore Norway and the Faroe Basin (Japsen et al., 2023). These observations are consistent with interpretation of apatite fission track data in the same areas. We suggest that this unconformity reflects doming above the rising head of the Iceland Plume in the upper mantle and prior to its impact at the base of the lithosphere at 62 Ma, 6 Myr later. These observations are consistent with the predictions of Campbell (2007) who showed evidence that pre-impact doming can become evident 3 to 10 Myr before plume impact, and that the diameter of the dome can be of the order of 1000 to 2000 km.

References.

Campbell, 2007. Testing the plume theory. Chem. Geol. 241, 153–1117. https://doi.org/10.1016/j.chemgeo.2007.01.024

Japsen, Green, Chalmers, 2023. Synchronous exhumation episodes across Arctic Canada, North Greenland and Svalbard in relation to the Eurekan Orogeny. Gondwana Research, 117, 207-229. https://doi.org/10.1016/j.gr.2023.01.011

How to cite: Chalmers, J., Japsen, P., and Green, P.: Stratigraphic and fission track evidence for the rising Iceland Plume in the Maastrichtian , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9778, https://doi.org/10.5194/egusphere-egu26-9778, 2026.

Subducting slabs play a fundamental role in controlling mantle circulation, plate motions, and surface tectonics. Global slab geometry models such as Slab2 provide an essential community reference by integrating seismicity to describe the geometry of subduction zones worldwide. In many regions, however, slabs are inferred to extend beyond the depth range of seismicity, motivating the incorporation of complementary constraints from seismic tomography.

Here we introduce 3DSlabs, a new global three-dimensional upper mantle slab geometry model constructed from seismic tomography. Following the workflow of Wu et al. (2016), fast tomographic velocity anomalies are interpreted and mapped into continuous three-dimensional slab surfaces using GOCAD. Unlike automated iso-surfacing, this approach allows complex variations in slab dip and curvature to be represented with high fidelity. Furthermore, by mapping seismic velocity directly onto the slab surfaces, 3DSlabs facilitates the identification and tracking of subducted buoyancy anomalies, such as aseismic ridges, plateaus, and hotspot tracks.

To maximize utility for the community, 3DSlabs is integrated with the Geodynamic World Builder (GWB), ensuring direct compatibility with geodynamic codes such as ASPECT. The resulting high-fidelity model is well suited for instantaneous mantle flow modeling and investigations of slab–mantle interaction. The inferred subducted features mapped onto these surfaces further provide new opportunities to investigate how along-slab heterogeneities influence subduction dynamics.

How to cite: Chen, Y.-W. and Wang, J.-L.: 3DSlabs – a global tomography-based upper mantle slab geometry model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10169, https://doi.org/10.5194/egusphere-egu26-10169, 2026.

On January 23, 2024, an Ms7.1 earthquake struck Wushi County, Aksu Prefecture, Xinjiang. While resulting in relatively limited casualties and economic losses, the event posed a certain threat to the geological safety of the Tianshan region. The Tianshan seismic belt has a history of intense seismic activity, with 17 recorded earthquakes of magnitude 7 or greater since 1716, including four exceeding magnitude 8. Notably, the Wushi earthquake is the largest event in this belt since the 1992 Ms7.3 Suusamyr earthquake in Kyrgyzstan. The 1992 Suusamyr earthquake was the first in the Tianshan region recorded by broadband digital seismographs, whereas the recent Wushi earthquake presents a valuable opportunity for a detailed case study using modern high-precision geodetic techniques. Occurring at the junction of the South Tianshan and the Wushi Basin, this event provides a crucial chance to investigate the deformation characteristics of strong earthquakes within the Tianshan seismic belt and to reveal the associated seismogenic structures and mechanisms. This research carries significant implications for understanding fault activity absorption mechanisms within the Tianshan Mountains and the characteristics of active deformation along the boundary between the Tianshan orogen and its foreland basin.

For the Wushi earthquake area, we acquired Sentinel-1 satellite data and GNSS data covering the region. Pre-seismic data collection included 200 frames from Sentinel-1 ascending track (T56) and 208 frames from descending track (T136). For co-seismic deformation analysis, data from tracks T56, T136, and T34 were utilized. Post-seismic data comprised 44 frames from track T56 and 36 frames from track T136. Time-series InSAR and D-InSAR methods were employed to derive regional deformation. The co-seismic results show significant line-of-sight surface deformation in both ascending and descending tracks, with a maximum displacement of approximately 75 cm. Fault slip distribution inversion indicates that the earthquake occurred on a northwest-dipping, left-lateral strike-slip fault with a variable strike and a thrust component. Co-seismic slip was primarily concentrated at depths between 4 and 25 km. Post-seismic deformation results suggest that short-term deformation was mainly induced by an Ms5.7 aftershock. Pre-seismic GNSS deformation results reveal differential crustal activity between the eastern and western sections of the Maidan Fault Zone within the study area, with higher activity observed in the eastern segment where the Wushi earthquake occurred.

Future work will involve analyzing pre-seismic InSAR deformation results to obtain long-term, large-scale seismic cycle deformation fields for the Tianshan earthquake region. The co-seismic slip motion consistency model will be applied to analyze the seismogenic structure and mechanism of the Wushi earthquake. Furthermore, numerical simulations will be employed to elucidate the coupling mechanisms of various post-seismic deformation effects, such as afterslip, viscoelastic relaxation, and pore rebound, following the Wushi earthquake. This integrated approach aims to establish a more systematic understanding of the earthquake's seismogenic mechanism and its post-seismic deformation processes.

How to cite: qingyun, Z., quancai, X., and shuang, Z.: Analysis of Seismic Cycle Deformation for the Ms7.1 Wushi Earthquake in Xinjiang Based on Geodetic Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10499, https://doi.org/10.5194/egusphere-egu26-10499, 2026.

Histories of vertical lithospheric motion preserved in sedimentary basins provide constraints on evolving mantle buoyancy and convection histories. We present a quantitative analysis of subsidence, exhumation and stratigraphic hiatuses to constrain mantle dynamics during the Cretaceous–Cenozoic, illustrated by case studies from northwestern Australia. Basin analysis across multiple basins from this region calculates the continental-scale vertical response to evolving geodynamic forces, from Jurassic–Cretaceous subsidence during sub-basin development associated with rifting and Gondwana breakup to the recent northeastward tilting of Australia driven by dynamic topography linked to slab subduction beneath the Indonesian margin.

In particular, our kinematic reconstructions of the Northern Carnarvon Basin quantify Jurassic–Cretaceous nearshore intraplate rift-extension rates (~8 mm/yr), with rift cessations at ~155 and ~120 Ma coinciding with major Gondwana breakup events. This temporal correspondence demonstrates strong coupling between far-field plate reorganisations and regional vertical and lateral motions and constrains lithospheric controls on strain localisation during Gondwana breakup events.

Integration of compaction and paleothermal data identifies two significant Mesozoic exhumation episodes that correlate spatially with mapped magmatic bodies, implying that thermal perturbations from sub-lithospheric sources drove regional uplift. Jurassic–Early Cretaceous NE–SW gradients in uplift and exhumation shoe dynamically evolving magmatic systems, associated with the Kerguelen and Exmouth plumes. In addition, we present uncertainty propagation analysis. This analysis indicates that robust coverage and high-quality data on the Northwest Shelf reduces uncertainty in subsidence and exhumation estimates, thereby increasing our confidence in the results and conclusions from this study.

How to cite: Clark, S., Makuluni, P., and Hauser, J.: Dynamic Reconstructions of Basins in Australia: Stratigraphic Constraints on Cretaceous to Cenozoic Mantle Convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10561, https://doi.org/10.5194/egusphere-egu26-10561, 2026.

Properties of the mantle are difficult to constrain and critical for controlling mantle evolution and dynamics. We attempt to constrain these properties by comparing the outputs from mantle circulation models (MCMs) to 9 disparate observations.  Over 250 MCMs driven at the surface by 1 Ga of plate motion history are considered. A metric is developed to quantify the fit/misfit between each observation and MCM prediction. The observations include, global seismic tomography, SOLA seismic inference of the Pacific upper mantle, global surface wave phase velocity data set, gradients of seismic velocity in the deep mantle, dynamic topography, geoid, geomagnetic reversals, temperature difference between MORB and OIB source regions, and the difference in amount of recycled oceanic crust in MORB versus OIB source regions. The comparisons are done with (i) heatmaps of each metric for each MCM, (ii) correlation between the metrics and input parameters, (iii) analyses of sub-sets where only a single MCM parameter is changed, (iv) random forest analysis where the importance and partial dependence plot of MCM parameters are produced for each metric. From this analysis we find that parameters can be constrained, including for example the temperature at the core mantle boundary, the preferred equation of state, the preferred plate motion history model, the presence of a basal layer, the buoyancy number of the recycled basalt, viscosity profile. For example the MCMs prefer a cooler core-mantle boundary, a mantle reference frame-based plate motion history, a Murnaghan EoS and a basalt buoyancy number in the lower mantle of around 0.4-0.5. Methods, analyses and further results will be presented.

How to cite: Davies, J. H., Panton, J., Plimmer, A., Beguelin, P., Andersen, M., Nowacki, A., Mason, S., Davies, C., Myhill, B., Elliott, T., Wookey, J., Roberts, G., O'Malley, C., Ferreira, A., Sturgeon, W., Shorttle, O., Andrew, W., Koelemeijer, P., Latallerie, F., and Biggin, A.: Constraining properties of mantle circulation models using disparate observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10775, https://doi.org/10.5194/egusphere-egu26-10775, 2026.

In this presentation, I will review some of our recent global tomography results, that provide constraints on the Earth mantle structure and mantle convection.

In the upper mantle, we have recently constructed global tomographic models of SV wave velocity, 𝑉𝑠𝑣, and radial anisotropy, 𝜉, using the same tomographic approach, with similar regularization and smoothing for the Rayleigh and Love wave data. We also use Rayleigh waves to constrain the azimuthal anisotropy, the quality factor 𝑄 and the melt content. We find that a 1-D model of radial anisotropy, close to PREM, but including a 3D crustal structure, explains the Love/Rayleigh differences almost everywhere, except in oldest parts of the continents and youngest parts of the Pacific ridge. No age dependence of the radial anisotropy 𝜉 in the oceanic upper mantle is required, while age is the main parameter controlling 𝑉𝑠𝑣, melt content and azimuthal anisotropy. In the asthenosphere, azimuthal anisotropy aligns on a large scale with present  plate motion only for fast plates (> ∼4 cmyr−1), suggesting that only fast-moving plates produce sufficient shearing at their base, to organize the flow on the scale of the entire tectonic plates. Part of the azimuthal anisotropy is also frozen in the shallow oceanic lithosphere. The presence of a small amount of partial melt, by reducing mantle viscosity, facilitates plate motion and large-scale crystal alignment in the asthenosphere.

We have also built global shear tomographic models of the whole mantle for the shear velocity (SEISGLOB2) and attenuation (Q_L3D). In the lower mantle, SEISGLOB2 has revealed a change in the shear velocity spectrum at around 1000 km depth. The spectrum is the flattest (i.e. richest in "short" wavelengths corresponding to spherical harmonic degrees greater than 10) around 1000 km depth and this flattening occurs between 670 and 1500 km depth. Q_L3D combines various S-phase measurements, including surface waves, direct (S, SS, SSS, SSSS), core-reflected (ScS, ScSScS, ScSScSScS), diffracted (S_{𝑑𝑖𝑓𝑓}) and their depth phases (e.g., sS, sScS, sS_{𝑑𝑖𝑓𝑓}), providing extensive depth and spatial coverage. A high attenuation zone highlights the peculiar nature of the mantle around 1000 km depth. This may indicate the presence of a global low-viscosity layer, in a region that roughly corresponds to the upper boundary of the Large Low Shear Velocity Provinces (LLSVPs), and where various changes in the continuity of slabs and mantle plumes have been observed. Our 3D shear quality factor model also confirms that the LLSVPs are attenuating, at least for body waves with periods near  35 s. The correlation between strong attenuation and low shear velocities within these regions suggests that the shear quality factor mostly captures the thermal signature of the LLSVP.

How to cite: Debayle, E., Stéphanie, D., Sun, S., and Ricard, Y.: Insights on mantle convection from global tomography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11226, https://doi.org/10.5194/egusphere-egu26-11226, 2026.

The geochemical composition of ocean island basalts (OIB) from Réunion Island has been controversially interpreted as recording either interaction between the mantle and Earth’s core [1] or the preservation of an ancient, Hadean silicate reservoir isolated since early Earth differentiation [2,3]. Resolving this debate bears directly on the nature of deep mantle heterogeneity, the longevity of early-formed reservoirs, and the efficiency of whole-mantle mixing through time. In particular, the extinct ¹⁸²Hf-¹⁸²W decay system provides a powerful tracer of both, core contribution due to the strong siderophile behaviour of W during core formation as well as early silicate differentiation processes because of the short half-life of ¹⁸²Hf.

Here we present new high-precision radiogenic W isotope data (μ¹⁸²W) for 39 basaltic lavas from Réunion Island, complemented by major and trace element compositions and long-lived radiogenic isotope ratios including ¹⁴³Nd/¹⁴⁴Nd, ⁸⁷Sr/⁸⁶Sr, and ^206,207,208Pb/²⁰⁴Pb. Measured μ¹⁸²W values range from 0 to –11, fully overlapping with the range reported in previous studies of Réunion and related plume products [1–3]. These results confirm that the Réunion mantle source is isotopically heterogeneous and requires the involvement of a geochemically distinct component not represented in depleted upper mantle reservoirs.

By integrating short-lived and long-lived isotope systematics with trace element constraints, we evaluate the origin of this component and its implications for deep Earth processes. In particular, we assess whether the observed μ¹⁸²W anomalies are more consistent with contributions from an early-formed silicate reservoir that avoided complete mantle homogenization, or with addition of core-derived material to the mantle plume source. Our dataset is discussed in the context of isotopic findings that provide compelling evidence for ongoing or episodic core–mantle chemical exchange recorded in OIB sources [4].

The combined data of Réunion basalts indicate that core addition is the most likely process to explain the chemical and isotopic observations. Our findings allow qualitative constraints on the mass exchange between the Earth’s core and mantel and highlight the importance of integrating multiple isotope systems to disentangle the complex history of mantle plume sources and their role in recording the mass exchange from core to surface on Earth.

References:

[1] Rizo et al. (2019) Geochemical Perspectives Letters, 6–11.

[2] Peters et al. (2018) Nature, 555, 89–93.

[3] Pakulla et al. (2025) Earth and Planetary Science Letters, 653.

[4] Messling et al. (2025) Nature, 642, 376–380.

How to cite: Willbold, M., Messling, N., Huang, X., and Hoffmann, D.: The Réunion Island mantle plume – isotopic constraints on core addition or ancient silicate component?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12125, https://doi.org/10.5194/egusphere-egu26-12125, 2026.

Tomographic images play a crucial role in estimating the thermodynamic state of Earth's mantle, yet reliable quantification of their uncertainties is essential for drawing robust conclusions in geodynamics. In particular, reconstructions of past mantle flow that rely on tomographic inputs require a practical handling of the difference in spatial scales between predictions from fluid dynamics and the heterogeneities observable through seismology. This scale discrepancy can indeed already be addressed through so-called tomographic filtering as a post-processing step applied to standard forward models of mantle circulation. However, integrating such approaches technically into adjoint or inverse modeling frameworks—used in data-driven mantle flow reconstructions—remains to be thoroughly explored.

Here, we perform a fully synthetic experiment to highlight the difficulties in quantitatively linking tomographic images with geodynamic models. Specifically, we employ the Subtractive Optimally Localized Averages (SOLA) method—a linear Backus–Gilbert-type inversion technique—to image a reference mantle circulation model. The SOLA inversions are based on finite-frequency traveltime residuals derived from full-waveform numerical seismograms computed for the geodynamic reference model.

Drawing on the insights provided by this synthetic experiment, we propose a workflow for adjoint-based mantle flow reconstructions that aims to leverage the tools provided by the SOLA approach. For the tomographic component, this involves generating spatially optimized averaging kernels that characterize local resolution (i.e. the specific tomographic filter), along with rigorous uncertainty estimates for parameter averages obtained by the propagation of data errors (both being built-in features of SOLA). On the geodynamic side, one should first aim to incorporate measures of tomographic resolution directly into the misfit/cost function of the adjoint method. This step is critical because the adjoint model validation compares observed surface dynamic topography in time with its prediction from the reconstructed flow history, which is highly sensitive to the tomographic input.  Once resolution-related biases are factored in, small model ensembles should make it possible to practically account for stochastic uncertainties, eventually yielding more robust constraints on mantle flow history. We suggest that the success of a specific misfit function and the realization of model ensembles can be assessed with dedicated synthetic closed-loop experiments, prior to their actual application.

Overall, our results offer practical guidance towards a strategy that integrates the complete tomographic information, including resolution and uncertainty, into fully operational reconstructions of past mantle flow.

How to cite: Freissler, R., Schuberth, B. S. A., Stotz, I. L., Zaroli, C., and Bunge, H.-P.: On the role of tomographic resolution and uncertainty in reconstructing past mantle flow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12227, https://doi.org/10.5194/egusphere-egu26-12227, 2026.

Constraining the transport of mass in the Earth’s mantle over a broad range of timescales is a key step in order to understand the mantle convection and its dynamic interactions with tectonic plates and core flows. Mapped with high accuracy all over the globe from GRACE and GRACE Follow-On satellite missions, the temporal variations of the gravity field can provide unique information on potential rapid mass redistributions within the Earth’s deep interior, even if their separation with the signals from the Earth’s fluid enveloppe is challenging. In the present study, we focus on the base of the mantle and the boundary with the core (CMB). Applying dedicated methods of space-time patterns recognition in the gravity field, we identify a rapid, anomalous north-south oriented gravity signal at large spatial scales across the Eastern Atlantic ocean in January 2007, which evolves over months to years. We show that this signal likely originates, at least partly, from the solid Earth ; it appears concomittant, both spatially and temporally, with the 2007 geomagnetic jerk. We hypothesize that it may be induced by vertical displacements of the perovskite to post-perovskite phase transition, caused by moving thermal anomalies near the base of the African Large Low Shear Velocity Province. This may result in the creation of a decimetric dynamic CMB topography over a timespan of a few years. To assess a potential link with the 2007 geomagnetic jerk, we finally investigate the impact of these changes in core-mantle boundary topography on the flow and the geomagnetic field in a thin layer at the top of the core. These results stress the interest of satellite gravimetry for providing novel insights into the dynamical interactions between the mantle and the core.

How to cite: Gaugne Gouranton, C., Panet, I., Mandea, M., Greff-Lefftz, M., and Rosat, S.: Rapid mass redistributions in the deep mantle from satellite gravity and interactions with core flows, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12420, https://doi.org/10.5194/egusphere-egu26-12420, 2026.

The Earth has possessed a magnetic field for at least ~4.3 Ga, as indicated by paleomagnetic data. To constrain Earth’s thermal and magnetic evolution, parameterized core models have traditionally relied on a parameterized mantle assumed to be vigorously convecting due to plate tectonics. By neglecting spatial variations in mantle temperature and viscosity, these models typically predict an inner core nucleation (ICN) age of 0.5–0.8 Ga, which requires a thermally driven dynamo prior to that time. Recent experimental constraints indicating higher core thermal conductivities have therefore led to the “new core paradox,” in which sub-adiabatic conditions can result in gigayear-long interruptions of the modeled geodynamo.

Alternatively, studies that couple higher-dimensional mantle convection models with parameterized core evolution have found that hot initial core temperatures and an insulating primordial lid above the core–mantle boundary (CMB) are required to reproduce the present-day inner core size, with minimal influence from the surface tectonic regime. However, these studies did not predict magnetic field strengths and showed that the available magnetic dissipation overestimates Earth’s magnetic field in the early evolution and underestimates it at later times.

Here, we present a new two-dimensional mantle convection model coupled to a core evolution model that incorporates state-of-the-art mineral physics data and magnetic field strength scaling laws. Our results require a ~200 km thick primordial dense layer and the presence of the post-perovskite phase at the base of the mantle, forming a CMB thermal lid that inhibits strong early core-cooling. By varying surface plasticity and the maximum density contrast of the lower mantle relative to the ambient mantle, we identify best-fit models that reproduce both inner core growth and the secular variation of the magnetic field.

Assuming a bulk silicate Earth (BSE) composition, 12 wt.% light elements in the core, a core thermal conductivity of 125 W m⁻¹ K⁻¹, an initial CMB temperature of 4564 K, and a CMB lid that is 7% denser than peridotite, ICN occurs at ~1.3 Ga, while the thermal dynamo ceases after ~3 Ga. Future constraints on the presence and evolution of a thermally stable layer in the core will further refine models of Earth’s magnetic field evolution.

How to cite: Müller, L., Kislyakova, K., Noack, L., Macdonald, E., Van Looveren, G., and Raorane, A.: Core–mantle coupling: New insights into the magnetic and thermal evolution of Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12612, https://doi.org/10.5194/egusphere-egu26-12612, 2026.

The Earth has sustained a magnetic field for at least 3.4 billion years, generated by convective motions of liquid iron within the outer core. Maintaining such a long-lived geodynamo requires efficient cooling of the core. However, a high core thermal conductivity as suggested by experiments and theoretical calculations reduces the convective power available prior to inner-core nucleation, making the continuous persistence of the magnetic field more difficult. This apparent incompatibility between high thermal conductivity estimates and evidence for a ~3.4 Ga-long geodynamo is known as the “New Core Paradox”. Because core cooling is primarily controlled by heat transfer through the overlying solid mantle, an accurate quantification of the heat extracted from the core via mantle convection is therefore essential to resolving this paradox.

Today, the mantle cools efficiently mainly through plate tectonics, via subduction of cold large plates. But when plate tectonics actually began is still debated. Did it start soon after Earth formed, around 4.5 billion years ago? Did it appear later, between 4 and 3 billion years ago? Or is it a more recent process, less than a billion years old?

We explored how different styles of mantle cooling would have influenced Earth’s thermal and magnetic history. We explored either a mobile surface like modern plate tectonics (i.e. mobile lid) or a less efficient, stagnant-lid-like regime (where the surface doesn’t move), or a transition from stagnant- to mobile-lid regime at a given time and with a given duration. This is important because how Earth’s mantle cooled over time is closely tied to its ability to keep generating a magnetic field.

We built a global model for the Earth coupling a core model including inner core formation and the possibility to form stably stratified layers, with a mantle model simulating different convective (hence cooling) regimes.

We performed a Markov Chain-Monte Carlo inversion using as constraints the present-day size of the inner core, the continuous 3.4 billion years old magnetic record, and the mantle potential temperature record. We inverted the viscosity parameters, tectonic transition parameters and core thermal conductivity. Our models successfully reproduce all the constraints for an onset between 4.0 Ga and 2.5 Ga, with a bimodal distribution characterized by a relatively early onset of mobile-lid convection with a long-duration transition, or a later onset with a more rapid transition to a mobile-lid regime. Our result show that the late and rapid transition case allows for a core thermal conductivity up to 110 W/m/K, providing a possible solution to the New Core Paradox.

How to cite: Bonnet Gibet, V. and Tosi, N.: A late onset of plate tectonics as a solution of the New Core Paradox., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13060, https://doi.org/10.5194/egusphere-egu26-13060, 2026.

Light elements are thought to be essential components of liquid cores in terrestrial planets and play a key role in core formation, chemical evolution, and the generation of planetary magnetic fields. In multicomponent iron–light element (Fe–LE) systems, when multiple light elements coexist in liquid iron, their solubilities are mutually constrained, forming an anti-correlated solubility relationship, referred to here as simultaneous solubility.

Here we investigate the simultaneous solubility and exsolution behavior of light elements in the Fe–Si–C–(H) system using a combination of high-pressure and high-temperature experiments and machine-learning force field accelerated molecular dynamics (MLFF-MD) simulations. Multi-anvil experiments conducted at pressures of 9–21 GPa and temperatures of 1400–2200 °C reveal that these light elements can dissolve simultaneously in liquid iron and exhibit simultaneous solubility limits, with exsolution of Si, C, and H observed during melting and quenching. Complementary MLFF-MD simulations of the Fe–Si–C system provide atomic-scale insights into light element interactions in metallic melts and reproduce the experimentally observed anti-correlated solubility trends under core-relevant conditions.

By combining experimental and computational results, we derive simultaneous solubility relationships in the Fe–Si–C–(H) system and show how they vary with temperature and pressure. These results suggest that in reduced planetary cores, such as those of Mercury and Earth, Si, C, and H may coexist as simultaneously dissolved light elements. As the liquid core cools, the progressive decrease in simultaneous solubility drives continuous exsolution of light elements, providing an additional potential energy source for core dynamics and offering a potential explanation for chemical heterogeneity at the core–mantle boundary (CMB).

How to cite: Li, Y. and Zhu, F.:  Light Elements Exsolution in the Fe–Si–C–(H) System of Terrestrial Planet Liquid Cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13280, https://doi.org/10.5194/egusphere-egu26-13280, 2026.

Earth’s magnetosphere is generated by convective dynamo action within its liquid metallic outer core. This same core-driven dynamo process has been inferred for other terrestrial planetary bodies which either presently possess a magnetosphere, or may have in the past. These bodies include Ganymede, Mercury, the Moon, and Asteroid 4 Vesta. However, understanding these core processes requires that the core composition be known. By experimentally determining the solid-liquid phase transitions of core-relevant alloys, the likely compositions of these terrestrial cores may be constrained.

            Experiments were conducted on 8 Fe-Si alloys in the range of Fe-5 wt% Si to Fe-33 wt% Si (FeSi) using a 1000-ton cubic anvil press, at pressures of 3-5 GPa and temperatures into the liquid state. A central 5-hole BN cylinder held 5 different Fe-Si sample compositions simultaneously with a thermocouple located at the base of the BN cylinder, and was surrounded by a graphite furnace within a pyrophyllite cubic pressure cell. Following quenching of each experiment, the samples were analysed by electron microprobe for composition and texture. From these analyses, the solidus and liquidus boundaries were mapped across the aforementioned compositional range at of 3, 4, and 5 GPa.

            It was determined that the melting boundary for 3-5 GPa was roughly 50-150 K higher than that of 1 atm, with a eutectic composition of Fe-20 wt% Si. Across the 3-5 GPa range, there was an increase in the melting boundary of roughly 50-75 K. Using pressure and temperature estimates from previous core modelling studies, a range of approximately 10-15 wt% Si was suggested for the core of the Moon.

How to cite: Kalman, B., Yong, W., and Secco, R.: High pressure melting of Fe-Si alloys with applications to the lunar core composition and dynamo processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13514, https://doi.org/10.5194/egusphere-egu26-13514, 2026.

The structure of the Earth's deep mantle is a result of complex processes that are influenced by surface tectonics through the subduction of oceanic lithosphere and by core dynamics through the heat flow across the core-mantle-boundary. The other way around the structures in the deep mantle affect the Earth's surface by feeding mantle plumes that sustain volcanism. By modulating the heat flow at the CMB the mantle also affects the dynamics of the core and the magnetic field.

These processes focus in the D'' layer that marks the mysterious few hundred kilometers directly above the core-mantle-boundary which contain dominant features like the Large Low Shear Velocity Provinces and features with rather extreme properties like the Ultra Low Velocity Zones. Knowledge of the structural features in the D'' layer is of importance for the understanding of long- and short-term processes in our direct environment at the surface of the Earth.

The remoteness of D'' layer more than 2,500 kilometers below the surface poses challenges for geophysical investigations and limits the resolution of seismological imaging. Seismic tomography with surface waves and normal modes therefor locate the large scale features, only. Detailed wavefield analysis and modeling of particular seismic phases, often based on array observations provide more detailed information about locally dominating structures and their contrasts. For the characterization of distributed small scale structures that can be referred to as heterogeneity even wavefield analysis fails due to the superposition of waves scattered at different locations of the heterogeneous material. Such heterogeneity can for instance represent remnants of oceanic crust that has been subducted down to the CMB.

Despite the complexity of signals generated by distributed heterogeneity the analysis of high frequency scattered waves provides constraints on the presence structures at short length scales of a few kilometers in the deep mantle. I review the theoretical basics of scattering theory and the observational evidence for deep Earth distributed heterogeneity. I discuss new observations of high frequency seismic waves scattered in the deep mantle together with limitations in the interpretation imposed by the nature of the scattered wavefield.

How to cite: Sens-Schönfelder, C.: Investigating small-scale deep-mantle structure, the stories told by high frequency scattered waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14881, https://doi.org/10.5194/egusphere-egu26-14881, 2026.

Some hotspot tracks, such as those formed by the Hawai’i and Galápagos mantle plumes, exhibit long-lived cross-track isotopic zonation, thought to reflect the streaking out of heterogeneous material in the plume conduit during upwelling. In lavas associated with the Galápagos mantle plume, three geochemical domains, present for at least 15 Myr, have been identified: northern, southern and central. The most extreme isotopic enrichments are observed in the northern domain of the Cocos Ridge at ~15 Ma, and in the southern domain of the Galápagos Archipelago at the present day. Owing to the northward migration of the Galápagos Spreading Center above the plume at ~5-10 Ma, this relationship suggests that geochemical enrichment in the Galápagos basalts is greatest above the region of the plume furthest from the nearby mid-ocean ridge. We examine the hypothesis that these temporal and spatial variations in geochemical enrichment reflect a ''shallow mantle control'', associated with differences in the mean depth of melting. We conducted forward melting models of a mixed peridotite-pyroxenite mantle to calculate the isotopic composition of the resulting melts formed under two different mantle flow regimes. Our results demonstrate that variations in the average pressure of melt generation, due to the influence of the nearby ridge axis, may explain the range of isotopic compositions across ~15 Ma of Galápagos plume-related volcanism. The patterns of isotopic zonation observed along the hotspot track confirm the paradigm of persistent plume striping, with variations in the degree of geochemical enrichment modulated by shallow mantle processes.

How to cite: Richards, M., Gleeson, M., Farnetani, C., Hoernle, K., and Gibson, S.:  Persistent Geochemical Zonation (“Striping”) within the Galápagos Mantle Plume, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15073, https://doi.org/10.5194/egusphere-egu26-15073, 2026.

The Galápagos Islands’ unique endemic flora and fauna originated mainly from colonization from South and Central America, including the famous Galápagos iguanas. Genetic analysis suggests that these iguanas arrived from Central America ~5-12 Ma million years ago (Late Miocene) or even earlier, yet the oldest of the present-day islands were formed at ~3.5 Ma. Recent geophysical analysis shows that now-submerged islands along the Cocos Ridge (Galápagos hotspot track) provided terrestrial habitat for colonization and differentiation during the time frame ~6-18 Ma. Remarkably, this was also a time window during which ocean currents and winds were much more favorable for transport from mainland Central America to these ancient islands, prior to the closing of the Isthmus of Panama at ~3-5 Ma due to regional plate tectonic forces. Thus, we can explain both the colonization timing and provenance of Galápagos iguanas in a framework that shows much promise for understanding the origins of other unique Galápagos species.

How to cite: Richards, M., Gentile, G., Karnauskas, K., and Orellana-Rovirosa, F.:  Geophysically Determined Island Habitat History and Colonization of the Galápagos Islands by Central American Iguanas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15113, https://doi.org/10.5194/egusphere-egu26-15113, 2026.

The nature and properties of the inner core has been a topic of keen interest since its discovery as a solid body by Lehmann in 1936. Since then, there have been numerous studies into its (isotropic and anisotropic) velocity and attenuation structure. These models typically feature strong hemispherical and layered structures, which dominate the interpretations of these models.

In this study, we focus on the attenuation structure of the inner core: energy that is lost inelastically, i.e. not through elastic scattering or redistribution. Here, we will demonstrate the progress we have made in creating a data set of new measurements of attenuation in the inner core from a variety of seismic phases (but especially PKPdf-PKPbc) with a focus on improving the spatial distribution of observations from previous studies using earthquakes from 2018--2025. We go on to benchmark our results against those of Pejic et al (2017), who used 400 high quality dt* measurements to invert for attenuation structure in the uppermost 400 km of the inner core.

How to cite: Martin, C. and Tkalčić, H.: New measurements of inner core attenuation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15485, https://doi.org/10.5194/egusphere-egu26-15485, 2026.

During the last 7 years several groups have reported paleomagnetic data documenting an unprecedented interval during the Ediacaran Period when the global geomagnetic field strength was only 10 to 3 percent of the present-day value, defining an ultra-low time-averaged field interval (UL-TAFI) from 591 to 565 Ma. Moreover, the EMANATE hypothesis suggests that atmospheric H loss to space through the UL-TAFI weak magnetosphere led to increased oxygenation, assisting the Avalon explosion of animal life (Tarduno et al., 2025). A relatively rapid increase in field strengths after the UL-TAFI has been suggested to record the onset of inner core nucleation; the return of magnetic shielding may have assisted subsequent Cambrian evolution. Herein, we present new data that suggest: 1. the UL-TAFI was at least 90 million years long, beginning in the Cryogenian Period and, 2. the field may have completely collapsed to zero during events as long as 200 kyr within the UL-TAFI. While the existence of the UL-TAFI does not comment on the need for core supercooling for inner core nucleation, the extended duration defined here is compatible with some models for such a process.  Variations of the field strength and dipolarity within the UL-TAFI may record bistability between the weak and strong field branches of the geodynamo as seen in some numerical simulations. This bistability, proposed to characterize the very start of the geodynamo, may have also been the underlying nature of the field during late Neoproterozoic times, explaining seemingly anomalous magnetic directions from global sites. The extended duration of the UL-TAFI, and the episodic complete collapse of the dynamo, support the hypothesis that H loss and increased oxygenation of the atmosphere and ocean, enabled the radiation of macroscopic Ediacaran animal life.

How to cite: Tarduno, J., Blackman, E., Schneider, J., and Cottrell, R.: A fibrillating Cryogenian-Ediacaran magnetic field: Implications for the nature of the dynamo, inner core nucleation, and the Avalon explosion of life, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15540, https://doi.org/10.5194/egusphere-egu26-15540, 2026.

True polar wander (TPW) records displacements of Earth’s rotation axis induced by mantle convective redistribution of internal mass anomalies. A TPW reversal near ~50 Ma inferred from paleomagnetic data remains debated, particularly its cause and its robustness across reference frames. We present 70-million-year, tomography-assimilative mantle-convection reconstructions that evolve present-day seismic structure backwards in time, with an energy-consistent flow formulation, yielding time-dependent density, inertia tensor, and TPW. Three independent diagnostics converge on a single, time-localized driver: (i) maps of the long-wavelength geoid-rate (∂N/∂t) show a focused Aleutian–Kamchatka lobe at 50 Ma; (ii) off-diagonal inertia-tensor time derivatives peak contemporaneously at this time; and (iii) cap-blanking experiments that zero anomalies within a 30–40° North-Pacific cap erase the U-turn, whereas comparable caps elsewhere do not. We interpret the causative structure as a coherent North-Pacific (“Kula–Izanagi” sensu lato) slab-flux pulse entering the lower mantle.

Predicted TPW paths quantitatively match palaeomagnetic trajectories across multiple mantle frames (reduced χ² ≈ 0.6; mean path-averaged angular misfit ≈ 1.7°) and reproduce the observed ~50 Ma U-turn bracketed by twin maxima in TPW speed. Present-day mantle-driven TPW rates of 0.2–0.4° Ma^-1 imply ~20–40% of the 20th-century geodetic rate. In head-to-head tests, slab-history reconstructions (with or without hotspot-fixed “domes”) differ markedly in azimuth and TPW-speed evolution, tend to distribute path reorientation over 60–45 Ma, and yield substantially larger misfits to the same data.

These results (i) isolate a geographically localized, time-specific mantle driver of the ~50 Ma TPW reversal, (ii) demonstrate reference-frame robustness using explicit misfit metrics, and (iii) provide a transferable workflow – geoid-rate mapping, inertia-tensor derivatives, and cap-blanking – for attributing TPW events to concrete mantle processes.

How to cite: Forte, A., Glišović, P., Greff-Lefftz, M., Rowley (Deceased), D., and Kamali Lima, S.: A North-Pacific slab-flux pulse drove the ~50 Ma TPW reversal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15742, https://doi.org/10.5194/egusphere-egu26-15742, 2026.

With the plans of the MAGIC/NGGM mission approved, there will be several decades of satellite gravity  data available. Both periodic and secular mass changes can be studied with this data, mostly surface mass changes like hydrology, ice melt, glacial isostatic adjustment, and large earthquakes. With the increasing time period of the gravity data set, smaller processes in the signal can be detected. Therefore, we conduct sensitivity analysis on small temporal gravity signals which can be related to mass change due to mantle convection.

We perform various sensitivity analysis studies to understand the added benefit of detecting mantle flow with satellite gravity change observations. A fast stoke solver (FLAPS) is developed that is based on an axisymmetric half annulus geometry. The model evolves over 50 years after which the difference between the initial and final state to compute the rate of change. Realistic Earth models (PREM) as well as synthetic models are tested to better understand the sensitivity of the gravity change data. To understand 3D variations in structure and viscosity, we use the open-source mantle flow software ASPECT and incorporate interior models related to ESA's 4D Dynamic Earth project. For the upper mantle the WINTERC-G model incorporates multi data types information in a joint inversion. New analysis show data sensitivity down to the transition zone. For the lower mantle, we use available global tomography models.

The gravity change observations are sensitive to the absolute viscosity state of the mantle. This is contrary to dynamic topography and geoid data, which do not have this sensitivity and studies using these data always have an ambiguity wrt. viscosity state. Moreover, it seems that the gravity change data is more sensitive to the lower mantle of the Earth. 3D calculations need HPC resources and we show that the mesh resolution needs high computational demands to consistently account for the temporal gravity due to mantle flow. Nevertheless, the modelled magnitude of the gravity change linked to global mantle convection seems to be larger than the formal error estimates of the GRACE and GRACE-FO instrumentation. A longer acquisition period will reduce the secular errors in the ocean, atmosphere and tidal correction models, such that eventually mantle convection can be studied directly by satellite gravimetry.

How to cite: Root, B. and Thieulot, C.: Global simulations of temporal gravity due to mantle flow and their sensitivity to the mantle rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16730, https://doi.org/10.5194/egusphere-egu26-16730, 2026.

The geological evolution of the Barents Sea Basin in the Arctic region during the Cretaceous reflects a complex interplay between subsidence and uplift processes. In this study, we analyse well lithostratigraphic data to identify hiatuses, unconformities and depositional periods, assess their spatial distribution, and quantify subsidence using the backstripping technique. Our results reveal episodic deposition and hiatuses across all wells during the Early Cretaceous, followed by a dominant basin-wide hiatus in the Late Cretaceous. Early Cretaceous subsidence was spatially variable, the southeastern parts of the Barents Sea Basin experienced more intensive subsidence compared to other areas. These observations could be linked to the influence of mantle-driven dynamic topography on basin evolution in relation with the High Arctic Large Igneous Province. The results indicate the importance of geodynamic processes in controlling basin architecture and stratigraphic development, with implications for understanding sedimentary evolution and hydrocarbon prospectivity in the Barents Sea.

How to cite: Babina, E., Vilacís, B., Makuluni, P., and Clark, S.: Vertical motions and Cretaceous basin evolution of the Barents Sea Basin in relation to mantle-induced dynamic topography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16736, https://doi.org/10.5194/egusphere-egu26-16736, 2026.

The geomagnetic field undergoes both long-term and short-term deviations from its predominantly dipolar configuration, expressed as polarity reversals and geomagnetic excursions. These episodes are characterized by significant drops in field intensity and an increase in the paleosecular variation index (PSV index), reflecting changes in the underlying geodynamo. This work focuses on analysing the temporal evolution of the field during these events in order to better constrain the dynamics of the geodynamo.

We utilized some of the most reliable paleomagnetic data-based models such as LSMOD.2, GGFSS70, GGFMB and PADM2M, encompassing different time periods to analyse the rate of change in the dipole moment and the PSV index. A sawtooth pattern of gradual dipole decay followed by rapid recovery during reversals, as proposed by past studies, has been observed in our study on the Matuyama Brunhes reversal. But, in contrast, we observed an opposite behavior of fast decay and slow recovery during most of the excursions. Accordingly, the PSV index exhibited a slow growth–fast recovery pattern during the reversal and a fast decay–slow recovery pattern during many excursions, although the PSV index results vary more than the dipole moment results. In this study, we test whether similar or distinct asymmetries characterize the Gauss–Matuyama reversal. The preliminary outputs from the newly developing Gauss–Matuyama field model were made use for that. Here, we will report the results of this ongoing work.

How to cite: Shinu, S., Nasser Mahgoub Ahmed, A., and Korte, M.: Geomagnetic Field Dynamics During Excursions and Reversals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17051, https://doi.org/10.5194/egusphere-egu26-17051, 2026.

The frequency of geomagnetic field reversals varies on time scales of tens of millions of years, reflecting mantle-controlled changes in outer core flow that sustains the geodynamo. Accurate knowledge of lateral heat flow variations across the core–mantle boundary (CMB) and their evolution over geologic time is therefore fundamental to understanding the long-term geodynamo behaviour.

Here, we aim at generating robust predictions of lower mantle thermal evolution based on compressible high-resolution mantle circulation models (MCM). By assimilating 410 million years of plate motion history, which coincides roughly with two mantle overturns, the time span of geologically-informed structure above the CMB covers the Cretaceous normal superchron and beyond. To estimate uncertainties in lower mantle thermal evolution, we will employ systematic variations of model parameters, with a focus on uncertainties in the underlying absolute plate motion reference frame. Appraisal of the MCMs will be performed by predicting seismic data that can be compared to observations. Long-period normal mode data are particularly suited in this context, as they provide global constraints. In addition, splitting functions show high sensitivity to variations in the absolute reference frame. The realistic histories of mantle thermal evolution and CMB heat flux that we aim for in this project can in future be linked to geodynamo models and thus be used to predict time-series of Earth's magnetic field behaviour.

How to cite: Schneider, A., Schuberth, B., Koelemeijer, P., Myhill, A., and Al-Attar, D.: Constraining deep mantle thermal evolution by linking geodynamic modelling, absolute plate motions and normal mode seismology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17109, https://doi.org/10.5194/egusphere-egu26-17109, 2026.

Within the DFG Priority Program 2404 'Reconstructing the Deep Dynamics of Planet Earth over Geologic Time' (DeepDyn, https://www.geo.lmu.de/deepdyn/en/) we investigate possible seismic signatures related to deep Earth processes. Specifically, we investigate seismic anisotropy, by measuring shear wave splitting (SWS) of SKS, SKKS, and PKS phases. Thereby, we determine the splitting parameters, the fast polarization direction Φ and the delay time δt, using both the energy-minimization and the rotation-correlation methods. Especially, we search for phase pair discrepancies based on the observation type (null vs. split) between SKS and SKKS phases. Such discrepancies are indications for a lowermost mantle contribution to the splitting signal because these phases propagate along different paths after leaving the core. Besides using own measurements, we complement our database with measurements from Wolf et al., GJI, 2025. In two regions, beneath Siberia and North America, we find laterally varying values for Φ, in the D’’ layer just above the core-mantle boundary. The preferred directions of Φ are thought to be due to the alignment of minerals resulting from shear in a material flow. In the centers of the study regions, where high seismic velocity is present in global seismic tomography models, mainly null measurements are retrieved whereas systematic variations of Φ seem to dominate at the edges of the high seismic velocity anomalies which are often interpreted as remnants of slabs. A preliminary interpretation for our observations may be that the sinking slab material pushes local mantle material aside, inducing a flow pattern which causes an alignment of minerals and thereby seismic anisotropy.

How to cite: Ritter, J. and Dresler-Dorn, F.: Mantle flow pattern from seismic anisotropy above the core-mantle boundary underneath Siberia and North America, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17168, https://doi.org/10.5194/egusphere-egu26-17168, 2026.

The structure of Earth's crust, mantle, and core holds clues to its thermal state and chemical composition, and, in turn, its origin and evolution. Geophysical techniques, and seismology in particular, have proved successful at probing Earth's deep interior and have done much to advance our understanding of its inner workings from mantle convection to crystallization and solidification of Earth’s liquid core. As the outer core cools and solidifies, light elements, such as Si, S, C, O and H, preferentially partition in the fluid outer core. However, the exact composition and thermal state of the outer core remains unknown. Traditionally, the composition of the core has been determined by performing theoretical ab initio calculations on candidate compositions and comparing the results for Vp, Vs and density to seismic reference models (e.g., PREM). Instead, we determine structure, composition and thermal state of Earth's outer core by inverting a plethora of short- and long-period seismic and astronomic-geodetic data in combination with new density functional theory calculations that are fit to a novel Gaussian Process Regression (GPR) equation of state (EoS). The GPR-EoS allows us to self-consistently compute thermo-elastic properties of liquid multi-component mixing models in the Fe-Ni-Si-S-C-O-H system along outer-core adiabats and across its entire pressure and temperature range. By mapping out the thermo-chemical model space of Earth’s outer core that match the seismic and geophysical data within uncertainties, we find two families of solutions characterised by: 1) Si (~4 wt%) and negligible amounts of H and C and 2) C and H (both 0.5 wt%) and smaller amounts of Si (<1 wt%). A correlation between H content and outer-core thermal structure is apparent, such that solutions with little-to-no H correspond to relatively high CMB and ICB temperatures (4100--4400~K and 5750–6000 K, respectively), whereas models with large amounts of H are characterised by lower CMB and ICB temperatures (~3600 K and 4750 K).

How to cite: Munch, F. D., van Driel, J., Khan, A., Brodholt, J., and Vocadlo, L.: Unraveling the composition and structure of the Earth's outer core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17208, https://doi.org/10.5194/egusphere-egu26-17208, 2026.

A key characteristic of plate tectonics is strain localization along narrow, weak boundaries between otherwise rigid tectonic plates. This localization enables efficient deformation, subduction, and plate motion, and plays a central role in the dynamic evolution of Earth. However, in mantle circulation models, plate velocities are often assimilated as surface boundary conditions without accounting for the rheological weakness of plate boundaries, relative to the surrounding lithosphere.

Weak plate boundaries can be reproduced via sophisticated strain weakening rheologies. While effective, this strategy makes the Stokes system nonlinear and incurs substantial computational cost.

Here, we exploit the fact that data assimilation implies that the locations of plate boundaries are known a priori and introduce specifically prescribed weak zones along plate boundaries in the models. These low-viscosity zones allow us to mimic the natural strain localization of Earth’s lithosphere, allowing deformation to focus at plate margins. We show that this approach can provide a computationally efficient and robust framework for bridging the gap between simplified convection models and the complex tectonic behavior of the real Earth.

How to cite: Rezaei, F., Bunge, H.-P., Ponkumar Ilango, P. I., Vilacís, B., Robl, G., Kohl, N., and Mohr, M.: Assessing the effect of weak tectonic plate boundaries in 3D global mantle circulation models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17266, https://doi.org/10.5194/egusphere-egu26-17266, 2026.

Understanding the internal dynamics, structure, and composition of our planet is a fundamental goal of Earth science, and geodynamic modelling has been central to this effort by providing a theoretical window into mantle convection. Moreover, the asthenosphere plays a key role in linking mantle dynamics to surface observations; its channelized nature allows it to be described analytically within the framework of Couette and Poiseuille flow regimes.

Using this framework, we predict global stress fields and compare them directly with observations from the World Stress Map (WSM), a global compilation of crustal stress indicators. Our approach enables fast hypothesis testing and the development of first-order expectations for how different mantle flow states influence surface stress patterns. It also identifies three distinct basal shear traction regimes, depending on whether the asthenosphere locally moves faster than, slower than, or at the same velocity as the overlying plate. As a result, some regions experience driving tractions, others resisting tractions, while some are nearly traction-free. These results show that stress field patterns cannot be explained without realistic upper mantle flow geometries, particularly the spatial distribution and combined effects of plumes, slabs, and plate-driven flow.

How to cite: Stotz, I. L., Hayek, J. N., Bunge, H.-P., and Carena, S.: Predicting present-day Earth’s lithospheric stress using analytical upper mantle flow models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17485, https://doi.org/10.5194/egusphere-egu26-17485, 2026.

Many geophysical studies require knowledge on the present-day temperature distribution in Earth’s mantle, which can be estimated from seismic velocity perturbations imaged by tomography in combination with thermodynamic models of mantle mineralogy. However, even in the case of (assumed) known chemical composition, both the seismic and the mineralogical information are significantly affected by inherent limitations and different sources of uncertainty. We investigate the theoretical ability to estimate the thermal state of the mantle from tomographic models in a synthetic closed-loop experiment and quantify the interplay of tomographically damped and blurred seismic heterogeneity in combination with different approximations for the mineralogical conversion from seismic velocities to temperature. Our results highlight that, given the limitations of tomography and the incomplete knowledge of mantle mineralogy, magnitudes and spatial scales of a temperature field obtained from global seismic models deviate significantly from the true state. The average deviations from the reference model are on the order of 50–100 K in the upper mantle and can increase with depth to values of up to 200 K, depending on the resolving capabilities of the respective tomography. Furthermore, large systematic errors exist in the vicinity of phase transitions due to the associated mineralogical complexities. When used to constrain buoyancy forces in time-dependent geodynamic simulations, errors in the temperature field might grow non-linearly due to the chaotic nature of mantle flow. This could be particularly problematic in combination with advanced implementations of compressibility, in which densities are extracted from thermodynamic mineralogical models with temperature-dependent phase assemblages. Erroneous temperatures in this case might activate ‘wrong’ phase transitions and potentially flip the sign of the associated Clapeyron slopes, thereby considerably altering the model evolution. Overall, the strategy to estimate the present-day thermodynamic state of the mantle must be selected carefully to minimize the influence of the collective set of uncertainties.

How to cite: Robl, G., Schuberth, B. S. A., Papanagnou, I., and Thomas, C.: Mantle temperatures from global seismic models: Uncertainties and limitations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18500, https://doi.org/10.5194/egusphere-egu26-18500, 2026.

Reconstructing the thermo-chemical evolution of Earth’s mantle across geological time is a central challenge in the geosciences. Addressing this problem increasingly relies on adjoint-based approaches, which cast mantle convection modelling as an inverse problem and enable the systematic assimilation of observational data into time-dependent simulations. Such methods underpin emerging efforts to build a digital twin of Earth’s mantle: a dynamic, physics-based representation constrained by diverse geological and geophysical observations.

To date, adjoint geodynamic inversions have primarily relied on constraints that act at the beginning or end of model evolution, or at Earth’s surface only, such as plate motions, geodesy, or seismic tomography. However, these datasets provide limited leverage on the evolving thermal and chemical structure of the mantle through time. Intra-plate volcanic lavas offer an underexploited observational constraint, as their major- and trace-element geochemistry records the pressure, temperature, and composition of mantle melting at the time of eruption, providing direct insight into past lithospheric thickness, plume excess temperature, and mantle source heterogeneity.

Here, we present an integrated framework for assimilating geochemical information from ocean island basalts into adjoint models of mantle convection using the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT). Using simulation-informed inversions of rare earth element concentrations, we demonstrate the power of geochemical data to recover the thermal structure of plume melting regions, including lithospheric thickness and plume excess temperature. We then use synthetic experiments to show how these geochemically derived constraints on melting conditions can be incorporated into adjoint reconstructions, substantially improving recovery of mantle temperature fields and flow trajectories relative to inversions based on surface or boundary constraints alone.

By explicitly linking geochemical observables to mantle thermal structure and flow, this approach reduces non-uniqueness in time-dependent inversions and strengthens the ability of adjoint models to retrodict mantle evolution. More broadly, it highlights the transformative potential of integrating geochemistry into data-assimilative geodynamic frameworks and represents a key step toward a fully constrained digital twin of Earth’s interior.

How to cite: Davies, R. and Ghelichkhan, S.: Assimilating Intra-Plate Lava Geochemistry into Adjoint Reconstructions of Earth’s Mantle Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19074, https://doi.org/10.5194/egusphere-egu26-19074, 2026.

Dynamic topography, the transient deflection of Earth's surface driven by mantle convection, exerts a first-order control on continental flooding, sedimentary basin subsidence, and long-term eustatic sea level. Changes in dynamic topography have been invoked to explain the widespread Cretaceous marine transgression, the subsequent retreat of epicontinental seas, and regional patterns of uplift and subsidence that cannot be attributed to tectonics alone.

Here I present global, high-resolution retrodictions of dynamic topography evolution over the Cenozoic, constrained by seismic tomography, plate kinematic reconstructions, and geological proxies of past surface elevation. These models reveal how migrating mantle upwellings and downwellings have driven substantial changes in surface elevation across multiple continents throughout the Cenozoic. The retrodicted patterns of dynamic topography change provide estimates of mantle-driven sea level contributions, offering new constraints on interpreting the stratigraphic and palaeogeographic record in terms of deep Earth processes.

How to cite: Ghelichkhan, S. and Davies, R.: Reconstructing Cenozoic Dynamic Topography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20350, https://doi.org/10.5194/egusphere-egu26-20350, 2026.

Recent advances in geodynamo modelling have been very successful in explaining many features of the geo-
magnetic field, including the field reversals and excursions. Previous studies have shown that the dynamics 
of these features depend on spatial variation in the core-mantle boundary (CMB) heat flux pattern. Contrary to 
previous studies, an up-to-date mantle reconstruction for the last 200 Myr provides patterns with a higher degree 
of complexity, featuring a network of interconnected regions with subadiabatic heat flow. We use these patterns 
as outer boundary conditions for dynamo simulation in order to explore whether its evolution can explain the 
observed variation in reversal rate. While the impact of large-scale structures at the core-mantle boundary has 
been thoroughly explored by Frasson et al. (2025), the contribution of smaller scales remains poorly constrained, 
which we aim to cover within the scope of these studies.

For our study, we apply the codensity approach which combines the effects of thermal and compositional density 
to represent both thermally driven convection and the enrichment of the outer core with light elements due to 
the inner core solidification. We first investigate the relative impact of thermal and compositional convection 
a for patterns with various degrees of complexity, defined by the spherical harmonics degree truncation l_max. 
Our models indicate that the field dynamics, including the reversal rate, depends on the truncation l_max, with 
solutions for l_max = 8 and l_max = 16 exhibiting more reversals than higher truncation degrees. This effect is 
present in models with mixed convection (a = 0.33 and a = 0.66). However, when compositional convection 
clearly dominates (a = 0.99), the pattern has no impact on the reversal behaviour, and the model evolves 
similarly to the homogeneous case. We also observe the emergence of subsurface low-radial-velocity regions, 
reminiscent of the stably-stratified lenses discussed by Mound et al. (2019). Our models also show strong 
zonal flows comparable to those discussed in Frasson et al. (2025). Our ongoing work focuses on comparing 
simulations for the CMB heat flux pattern at the present-day time and during the CNS.

How to cite: Lohay, I. and Wicht, J.: Influence of Small-Scale Core-Mantle Boundary Structures on the Dynamics of the Earth’s Outer Core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20825, https://doi.org/10.5194/egusphere-egu26-20825, 2026.

The investigation of geomagnetic variations has revealed the presence in Earth's core of a planetary-scale, axially columnar and eccentric gyre flow. Together with the magnetic anomaly of low intensity presently seen beneath the South Atlantic, these structures show that longitudinal hemisphericity is a common feature of the geodynamo. Here, we propose that these hemispherical features result from the onset properties of spherical shell rotating convection in presence of an imposed axial magnetic field, with spatially homogeneous fixed-flux thermal boundary conditions. For an Earth-like range of background magnetic field amplitudes, we find hemispherical critical convection modes that are largely supported by a magneto-Archimedes-Coriolis (MAC) balance and where viscosity plays a secondary role. Pursuing this analysis with fully developed, turbulent self-sustained dynamo simulations, we find that hemispherical modes inherited from convection onset can be maintained if the MAC balance is not perturbed by inertia, the force coming at the next order in the force balance. The presence of the eccentric gyre is therefore conditioned to the magnetic energy matching or exceeding the kinetic energy in the system, the so-called strong-field dynamo regime. The simulations also feature low magnetic intensity anomalies that rotate westward together with the gyre flow.  We highlight a strong correlation between the gyre longitudinal position, the low intensity focus of magnetic intensity, and the eccentricity of the dynamo-generated dipole, showing that these hemispherical structures are indeed linked by the properties of magnetic induction.

How to cite: Grasset, L.: Longitudinally hemispheric structures in the geodynamo : from their physical origin to their geomagnetic consequences, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21834, https://doi.org/10.5194/egusphere-egu26-21834, 2026.

How to cite: Roy, P., van Hunen, J., and Pons, M.: Sagduction: Could This Explain Early Earth Tectonics? A Modeling Perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-83, https://doi.org/10.5194/egusphere-egu26-83, 2026.

Near the equator of Mars, between the branched valleys of Noctis Labyrinthus and Valles Marineris, a large rift system, lies a heavily fractured and eroded region, whose tectonic history is poorly constrained. In this region, an eroded shield volcano, named ‘Noctis Mons’, was recently identified through satellite imaging (Lee & Shubham, 2024). Its complex topography makes it difficult to provide a clear chronology of events that led to its formation and erosion. Processes such as plume uplift, fracturing and interaction with the Valles Marineris rift system, gravitational collapse, and the contact of hot volcanic materials with shallow subsurface ice likely played an important role for shaping this volcanic construct. 

In this work, we test the hypothesis that an ascending mantle plume is responsible for the unique features of Noctis Mons.  We first model a rising plume using the geodynamic code GAIA (Hüttig et al., 2013). The Tharsis province represents a large-scale and thick regional crustal thickness anomaly that we incorporate into our plume model by adding a step-like function to evaluate the influence of varying crustal thickness on an ascending plume. We further test several parameters that control the plume dynamics and morphology, including the distribution of heat sources between the mantle and crust, the thermal conductivity of the crust and mantle, the depth-dependence of the viscosity, as well as the consideration of partial melting and melt extraction. Once the plume reaches the base of the lithosphere, we use the GAIA-generated plume temperature distribution to compute crustal deformation. We evaluate flexural uplift and strains in response to this plume to identify regions of extension using a methodology similar to (Broquet & Andrews-Hanna, 2023). The density variations of the plume generated by our geodynamical models is used to solve a system of flexure equations for dynamic uplift, accounting for horizontal and vertical loading as well as self-gravity effects. We iterate both the plume characteristics produced by the geodynamical model and its induced crustal deformation until we find an optimal scenario that reproduces Noctis Mons’ topography and predicts extensional features similar to Noctis-related graben systems seen in satellite images and topography. We also analyze present-day gravity and topography to characterize the rigidity of the lithosphere and the density of the materials composing Noctis Mons.

With our computational framework we aim to constrain the magmatic behavior as well as thermophysical and rheological parameters for the crust and mantle that led to the complexity of tectonic features observed at Noctis Mons, informing our understanding of the formation and evolution of volcanic constructs on Mars.  

Studying plume ascent near Noctis Mons further informs our understanding of volcanism on Mars in its early history. Recent seismic recordings from the InSight lander reported activity in Elysium Planitia, indicating a potential upturn in tectonic activity. We will apply our ascending mantle plume model to Elysium Planitia, a region near Mars’ equator, that potentially hosts a giant and presently active mantle plume (Broquet & Andrews-Hanna, 2023).

How to cite: North, A., Broquet, A., and Plesa, A.-C.: Flexure Modeling of Plume Ascension on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-416, https://doi.org/10.5194/egusphere-egu26-416, 2026.

Mantle plumes are hot upwellings that transport heat from the core to the base of the lithosphere, and sample lowermost-mantle chemical structure. Plume buoyancy flux Q_B measures the vigor of upwellings, which relates to the mass and heat fluxes that mantle plumes convey to sub-lithospheric depths. Hotspot swells are broad regions of anomalous topography generated by the interaction between mantle plumes and the overlying lithosphere, yet the links between plume properties and swell morphology remain poorly understood.

Traditional approaches to measure Q_B are based on two assumptions: (1) the asthenosphere moves at the same speed as the overriding plate; (2) hotspot swells are fully isostatically compensated, in other words, the seafloor is uplifted due to the isostatic effect of replacing ”normal” asthenosphere with hot plume material. However, at least some plumes (e.g., Iceland) can spread laterally faster at the base of the lithosphere than the corresponding plate motion. Also, hotspot swells are partly dynamically compensated. With increasingly accurate observational constraints on dynamic seafloor topography, it is the time to update plume buoyancy fluxes globally and build a scaling law between the surface dynamic topography and plume buoyancy flux.

Here, we conduct thermomechanical models to study plume-lithosphere interaction and hotspot swell support. We use the finite-element code ASPECT in a high-resolution, regional, 3D Cartesian framework. We consider composite diffusion-dislocation creep rheology, and a free-surface boundary at the top. We systematically investigate the effects of plume excess temperature (∆T), plume radius (r_p), plate velocity (v_p), plate age, and mantle rheological parameters. From these results, we develop a scaling law that relates swell geometry to plume parameters. We find that swell height and cross-sectional area (A_swell) have a robust power-law relationship with Q_B. A_swell shows an almost linear dependence and provides the most reliable geometric indicator of Q_B. Empirical fitting further reveals that r_p has a dominantly positive correlation with swell height, width, and A_swell, while ∆T contributes secondarily. On the contrary, v_p has a relatively small (and mostly negative) effect on swell parameters. Higher viscosities in the asthenosphere lead to wider swells, higher A_swell andQ_swell. Applying these empirical fits to Hawaii indicates a minimum Q_B of ~3,860 kg/s.

Figure 1. Results of example cases at 300 Myr. Each row represents the cases A2, A7, and C7. The left column displays the potential temperature isosurface (contours at 1500K and 1700K), while the right column presents the dynamic topography.

We demonstrate that previous swell-geometry-based estimates underestimate the true buoyancy fluxes of the underlying upwelling, partly because plumes spread faster than plate motion for high Q_B and low v_p. The empirical fits developed here highlight the need for future models to incorporate melting, compositional effects, and variable lithospheric structure.

As a final step, we invert these predictive fittings and apply them to intraplate hotspot swells in all ocean basins to quantify the heat and material fluxes carried by plumes on Earth. This effort will help to inform the Core-Mantle Boundary heat flux.

How to cite: Ma, Z., Ballmer, M., and Manjón-Cabeza Córdoba, A.: New Scaling between Plume Buoyancy Fluxes and Dynamic Topography from Numerical Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-720, https://doi.org/10.5194/egusphere-egu26-720, 2026.

During the past 2 decades, data coverage and methodological developments have considerably improved the resolution of seismic tomography maps, refining our mapping of the deep Earth’s mantle structure. Nevertheless, the uneven distributions in sources (the earthquakes) and receptors (the seismic stations) leads to non-uniqueness of the solution and requires the prescription of a priori information (mostly damping and smoothing), the effect of which is to smear out seismic images and degrade their effective resolution. Alternatively, statistical quantities have been used to investigate the nature, purely thermal or thermo-chemical, of the structures observed by seismic tomography. In particular, it has long been recognized that the statistical distribution of shear-velocity anomalies (dlnV_S) in the lowermost mantle shows some degree of asymmetry in the form of a slow velocity tail, and that this slow tail is associated with the large low shear-wave velocity provinces (LLSVPs), the prominent feature on lowermost mantle tomographic maps. This bimodal distribution appears from around 2200 km and persists towards the deeper mantle. Yet, the phase transition to post-perovskite (PPv) at depth ~2700 km, if not happens globally, implies a trimodal distribution for dlnV_S. Here, we bring new insights on these questions. First, we investigate the effect of the seismic tomography ‘operator’ on seismic velocity anomalies triggered by different possible lowermost mantle thermo-chemical structures. For this, we first run simulations of thermal and thermo-chemical convection including or not the post-perovskite phase, and we calculate synthetic velocity anomalies predicted by these simulations. We then apply to these synthetic velocity anomalies a tomographic filter built for the tomographic model HMSL-SP06. We show that seismic signatures corresponding to different materials (regular mantle, thermo-chemical piles and PPv) are clearly distinct on statistical distribution of unfiltered shear-and compressional velocity anomalies, dlnV_S and dlnV_P, but get mixed or partially mixed after applying the filter. Interestingly, for synthetic velocity anomalies built from thermo-chemical simulations, a low velocity tail clearly appears on dlnV_S histograms, but not on dlnV_P histograms, similar to what is observed in real seismic tomography maps. For synthetic velocity anomalies built from purely thermal simulations, dlnV_S histograms do not feature any low velocity tail, and distribution histograms for both dlnV_S and dlnV_P are fairly Gaussian. Overall, our results therefore support the hypothesis that the LLSVPs observed at the bottom of the mantle are composed of hot, chemically differentiated material. They further show that the mixing of seismic signatures due to tomographic filter, implying the statistical distribution of dlnV_S and dlnV_P may be richer and more complex than it appears to be from seismic tomography models. Acknowledging the mixing of seismic signatures inherent to tomography models, we then apply cluster analysis with trimodal distribution to four recent tomographic models: GLAD-M35, REVEAL, SPiRaL-1.4, and TX2019slab.  We identify three velocity clusters, slow, neutral, and fast, which we associate with thermo-chemical piles, regular mantle, and PPv. Based on this analysis, we provide a probability map of the three clusters, which may be used to better understand the lowermost mantle structure and facilitate future geodynamic studies. 

How to cite: Shih, S.-A., Deschamps, F., and Su, J.: Seismic signatures: mixing with a tomographic filter and identifying with cluster analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2256, https://doi.org/10.5194/egusphere-egu26-2256, 2026.

The Thermal Lattice Boltzmann Method (TLBM) models finite Prandtl number thermal convection and multiphase flow at high Rayleigh numbers in the turbulent regime. As such, it offers a powerful means to study early earth which was shaped by magma oceans (MOs) where turbulent convection governed the transport of heat, silicates and volatiles. Ab-initio molecular dynamics shows that pressure and temperature dependent viscosity of silicates can vary by many orders of magnitude resulting in stratified Prandtl numbers ranging from much lower to much higher than unity spanning up to 3 – 5 orders of magnitude. We incorporated such P-T dependent viscosity into the Thermal LBM to explore the impact of stratified Pr on the convective dynamics of turbulent magma oceans. We find that the Pr stratification has a dramatic influence on turbulent flow, with strong vorticity only occurring at shallower depths above 1000 km for colder adiabats which implies greater chemical equilibration. We also combined the TLBM and multiphase LBM to model iron-silicate segregation due to large iron-rich impactors in a 3000 km thick magma ocean with a Prandtl number of unity. These studies indicate that thermal convection exerts only a modest influence on the spatial distribution of iron in MOs. Our results reveal that the time for iron droplets to fully settle lies in the range 15 – 30 days, and that vigorous thermal convection tends to confine fragments of smaller impactors to deeper regions of the MO, whereas, fragments of larger impactors disperse throughout all depths of the MO.

How to cite: Mora, P., Morra, G., Honarbakh, L., Jackson, C., and Karki, B.: Research progress with Thermal Lattice Boltzmann Method to study early Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2345, https://doi.org/10.5194/egusphere-egu26-2345, 2026.

The mantle’s redox properties play a pivotal role in regulating the exchange of redox budget between Earth’s deep interior and surface, ultimately influencing the accumulation of atmospheric oxygen and the evolution of life. However, how mantle redox state developed, particularly the mantle source associated with mid-ocean ridge-like settings, remains a subject of ongoing debate. Here, we employed thermodynamic-thermomechanical numerical simulations to explore the redox properties of melts formed under mid-ocean ridge-like settings in both Archean and modern conditions. The results of these simulations were systematically compared with an extensive database of mid-ocean ridge-like rocks, dating back as far as 3.8 Ga, to reconstruct the mantle’s redox evolution since the early Archean. This reconstruction utilized a novel and reliable redox proxy, the whole-rock Fe³⁺/ΣFe ratio, by integrating forward numerical modeling with thermodynamic inversion based on natural observations. This ratio is defined as the primary proxy for redox budget variations under mantle reference conditions, especially when the influence of other minor redox-sensitive elements (e.g., carbon, sulfur) is negligible. Our findings demonstrate that the mantle’s average Fe³⁺/ΣFe ratio has approximately doubled since the early Archean. Moreover, our calculations suggest that the ancient ultra-low-oxygen-fugacity mantle found in modern oceanic lithosphere results from an initially reduced origin, rather than deep and hot partial melting. By linking the non-monotonic evolution to geological evidence of tectonic activity, we suggest that the mantle’s redox history may reflect significant tectonic reorganization events. Our findings highlight the intrinsic coupling between Earth’s oxygen-rich environment and tectono-magmatic processes.

How to cite: Duan, W., Zhu, X., Gerya, T., Zhou, X., and Tian, J.: The Mantle Fe3+/ΣFe Ratio Has Doubled Since the Early Archean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2595, https://doi.org/10.5194/egusphere-egu26-2595, 2026.

As the origin of the stable large low shear velocity provinces (LLSVPs) beneath Africa and the Pacific is still unclear, we numerically consider two possible scenarios. Structures can form either from a primordial layer or a growing layer above the core-mantle boundary (CMB). The primordial layer is considered as a remnant of the early magma ocean phase, while the growing layer results from core-mantle interaction. In our 2D Cartesian study we analyze a diffusive influx of iron-rich core material.

We investigate the temporal and spatial stability of thermochemical piles under the influence of rheological parameters. Our model rheology is given by a viscosity depending on temperature, stress, depth and composition. Furthermore, we also investigate the effect of a depth-dependent thermal expansion coefficient. As all these parameters affect the strength of convection, they ultimately also have an impact on the stability of piles. Increasing the ratio between the top and bottom viscosity or expansivity leads to longer pile lifetimes and more stable piles. Therefore, piles can have formed in the Archean mantle but will have broadened and stabilized in time with the cooling of the mantle.

Typically, we find that these piles anchor thermochemical plumes, so that long-lived plumes exist in the center of piles. Less stable plumes occur at the edges of piles for a few million years as piles move and merge. The movement of piles results is a consequence of slabs pushing them around or of thermal plumes attracting dense piles.

How to cite: Stein, C., Sitte, H. W., Weber, C., and Hansen, U.: Stability of thermochemical piles of different origins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2708, https://doi.org/10.5194/egusphere-egu26-2708, 2026.

The formation and stabilization of continental crust during the Archean remains a fundamental problem in Earth sciences, requiring numerical models that can self-consistently capture multiphase flow, melt segregation, and thermochemical buoyancy within a convecting mantle. Here, we employ a thermal Lattice Boltzmann Method (TLBM) based on the Rothman–Keller multiphase formulation to investigate continent formation in a dynamically evolving Archean mantle. The model resolves two interacting lithological components representing basaltic crust and peridotitic mantle, coupled to a thermal field through the Boussinesq approximation. Melt generation, extraction, and retention are explicitly incorporated, allowing density and viscosity to evolve continuously as functions of temperature, melt fraction, and composition. Melt extracted from basalt is treated as an immiscible, low-density phase representing Tonalite–Trondhjemite–Granodiorite (TTG) crust. Unlike traditional marker-based or fixed-density approaches, this framework enables self-consistent tracking of compositional evolution without prescribing rigid phase boundaries. Simulations are conducted in annular geometry to approximate spherical curvature while retaining computational efficiency, with spatial resolution ranging from ∼15 km near the surface to ∼8 km at the core–mantle boundary (CMB). Results show that thermally driven melt production and compositional differentiation naturally generate buoyant, long-lived TTG crust that thickens and stabilizes against recycling. Residual basalt forms a denser layer beneath the TTG crust, contributing to lithospheric stabilization while remaining susceptible to recycling under cold, dense conditions.

How to cite: Bargees, A., Pilia, S., Mora, P., Morra, G., Kuang, J., and Honarbakh, L.: Thermal Lattice Boltzmann Modeling of Archean Continent Formation Using a Rothman–Keller Multiphase Framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2842, https://doi.org/10.5194/egusphere-egu26-2842, 2026.

The existence and eruptibility of mantle plumes in the Hadean-early Archean mantle are fundamental to interpreting the scarcity and timing of komatiites and other ultramafic magmas. Existing approaches often rely on parameterized thermal evolution or idealized forced-plume setups, so they rarely test plume eruptibility in fully convecting, high-Rayleigh whole-mantle dynamics. We use a thermal lattice-Boltzmann mantle convection approach with a multiphase formulation to test whether thermochemical plumes in a hot, vigorous, post-magma-ocean mantle can dynamically reach the surface, and under which conditions they are expected to erupt rather than stall and pond.

We simulate whole-mantle convection in annular geometry, solving Boussinesq Stokes flow coupled to heat advection-diffusion, and explore Hadean-like thermal structures at high Rayleigh numbers. Deformation is governed by nonlinear, visco-plastic rheology with Reynolds temperature-dependent viscosity, allowing transitions between weak- and strong-lid regimes via depth-dependent yield stress. Thermochemical plumes are represented by introducing a dense (e.g., eclogite-rich) component in the deep mantle that can be entrained into rising hot material, enabling us to quantify how compositional loading modifies plume ascent, head-tail structure, and interaction with the lithosphere. Melting is implemented within the simulations: melt generation, extraction, and retention are explicitly coupled so that density and viscosity evolve continuously as function of temperature, melt fraction, and composition.

Across the parameter suite, we track plume head trajectories, maximum ascent depth, and the spatiotemporal distribution of melt production/extraction to map an “eruption window” in Rayleigh-rheology-composition space. We compare this dynamical window with the observed timing and abundance of komatiites, and infer how thermochemical structure near the core-mantle boundary may have regulated the longevity and eruptibility of early Earth plumes.

How to cite: Pilia, S., Bargees, A., Mora, P., and Morra, G.: Can Hadean thermochemical plumes erupt? Insights from a high-Rayleigh number thermal lattice-Boltzmann mantle convection model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4360, https://doi.org/10.5194/egusphere-egu26-4360, 2026.

The thermal history of the Earth, it’s chemical differentiation and also the reaction of the interior with the

atmosphere is largely determined by convective processes within the Earth’s mantle. A simple physical model,

resembling the situation,shortly after core formation, consists of a compositionally stable stratified mantle, as

resulting from fractional crystallization of the magma ocean. The early mantle is subject to heating from below

by the Earth’s core and cooling from the top through the atmosphere. Additionally internal heat sources will

serve to power the mantle dynamics. Under such circumstances double diffusive convection will eventually lead

to self organized layer formation, even without the preexisting jumps is material properties. We have conducted

2D and 3D numerical experiments in Cartesian and spherical geometry, taking into account mantle realistic

values, especially a strong temperature dependent viscosity and a pressure dependent thermal expansivity . The

experiments show that in a wide parameter range. distinct convective layers evolve in this scenario. The layering

strongly controls the heat loss from the core and decouples the dynamics in the lower mantle from the upper

part. With time, individual layers grow on the expense of others and merging of layers does occur. We observe

several events of intermittent breakdown of individual layers. Altogether an evolution emerges, characterized by

continuous but also spontaneous changes in the mantle structure, ranging from multiple to single layer flow. Such

an evolutionary path of mantle convection allows to interpret phenomena ranging from stagnation of slabs at

various depth to variations in the chemical signature of mantle upwellings in a new framework

How to cite: Hansen, U. and Dude, S.: Dynamical layering in planetary mantles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4522, https://doi.org/10.5194/egusphere-egu26-4522, 2026.

Do the various continental crustal growth curves formulated from disparate geochemical models robustly inform us as to why the Hadean (pre-4 Ga) rock record is basically non-existent? Is its absence due to extrinsic effects (bombardment)? Or, could it be that little or no continental crust existed at first? On the other hand, was this record essentially lost over time by recycling processes? For instance, the biggest problem with searching for any information about the history of plate tectonics is that the process erases evidence of its own existence. The age of oceanic crust averages about 70 Ma and is not older than 200 Ma because plate tectonics keeps recycling it (except for some old ophiolites). Most of the crust by surface area is oceanic, whereas most crust by volume is continental. The mean age of continental crust (ca. 2 Ga) is 36× greater than that of oceanic crust because its buoyancy prevents it from subducting except for loss to subduction via erosion. The overall decline in preserved continental crust based simply on the detrital zircon record shows a roughly 1.4 Gyr e-folding time. The residence time of the lithosphere is the average length of time that it will remain as a geochemical entity; this is estimated to be about 500-750 Myr. The value is about half of the observed e-folding time for the pre-Phanerozoic (>542 Ma) continental crust, but is close to the average mixing timescale since the Archean of about 420-440 Myr for primitive mantle, recycled continental crust and mantle residue. Assuming the residence time of 750 Myr is a good estimate for the half-life of continental crust, then the e-folding time is in broad agreement with both the zircon record and model calculations of crustal reworking. The zircon record is strongly biased to continental crust, because zircon is most commonly found in granites and granitoids, which constitute the major rock fraction of the continents.  The trends in the detrital zircon data can be interpreted to represent decreasing preservation rather than increasing production, of continental crust. 

How to cite: Mojzsis, S. J.: Whence the Missing Hadean Rock Record?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4906, https://doi.org/10.5194/egusphere-egu26-4906, 2026.

Calcium silicate perovskite (CaPv) is the host for many large ion lithophile elements including the heat-producing elements in the lower mantle. Whether, when, and where it forms during the solidification of the magma ocean is fundamental to understanding the geochemical and geodynamical evolution of the early Earth and the trace element distribution in the lower mantle. In this study, we performed first-principles molecular dynamics simulations to investigate the partitioning behavior of Ca (alongside other alkali-earth elements, Sr and Ba) between bridgmanite and molten pyrolite. Our results show that the bridgmanite-melt partition coefficient of Ca remains smaller than 1 along the liquidus across the lower mantle, and decreases further between the magma ocean liquidus and solidus, indicating that Ca is incompatible in bridgmanite at all relevant crystallization conditions in the lower mantle. This results in a progressive enrichment of Ca in the magma ocean as it solidifies, leading unavoidably to the crystallization of CaPv during the final stages of solidification in the deep mantle. Laser-heated diamond anvil cell experiments performed to replicate the crystallization of pyrolitic melt in the same conditions as our simulations confirm the crystallization of CaPv in the last stages of solidification. From Ca to Sr to Ba, the bridgmanite-melt partition coefficients decrease by orders of magnitude, indicating a significant enrichment of these large ion lithophile trace elements in the residual melt. Combined with previous experimental studies at lower P-T conditions, our findings infer that both large ion lithophile elements and their host, CaPv, will be concentrated in the deep mantle at the end of magma ocean solidification.

How to cite: Wang, T., Badro, J., Caracas, R., Gendre, H., and Hébert, C.: Formation of calcium silicate perovskite above the core-mantle boundary during solidification of Earth’s magma ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5529, https://doi.org/10.5194/egusphere-egu26-5529, 2026.

Degassing of the magma ocean shaped the Earth’s early atmosphere and volatile budget. Despite its fundamental importance, the oxidation conditions of the magma ocean and the associated degassing processes remain poorly constrained. Sulfur, an abundant volatile element with multiple valence states, provides a sensitive tracer of redox-dependent degassing, making it an ideal probe for these processes.

Here, we present the first systematic investigation of sulfur degassing under realistic magma ocean conditions typical of the beginning of the Haden, using ab initio molecular dynamics simulations. Our results reveal that sulfur volatility and its speciation in the gas phase are strongly controlled by redox conditions: oxidizing conditions make sulfur highly volatile as sulfur oxides, reducing conditions keep it bound to the silicate melt. In view of our results, the observations of sulfur depletion in the Earth today, can be explained if degassing of the early magmas from planetesimals during accretion occurred under relatively reducing conditions. Sulfur degassing at the magma ocean stage of the early Earth brought reducing species to the early atmosphere, with the sulfur vapor phases being favorable for the prebiotic synthesis of amino acids. Our sulfur degassing results establish a direct link between the depletion of volatile elements, the redox state of the magma ocean, and the composition of the early atmosphere, providing new insights into the evolution of early Earth.

How to cite: Wang, D., Wang, W., Wu, Z., and Caracas, R.: Redox Controls on Sulfur Degassing in the Magma Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5569, https://doi.org/10.5194/egusphere-egu26-5569, 2026.

Cooling of the core provides a substantial part of the mantle heat budget, while mantle convection determines the heat flux across the core-mantle boundary, hence the existence or not of a planetary dynamo. Thus, the thermal evolutions of core and mantle should be treated in a coupled manner. To accomplish this, the core has normally been coupled into mantle convection simulations assuming that it has an adiabatic temperature profile and can thus be characterized by single temperature (e.g. the CMB temperature) (e.g. Nakagawa & Tackley, 2014 GCubed), allowing a simple 0-dimensional parameterization such as a uniform "heat bath" or one including inner core growth (e.g. Buffett et al, 1996 JGR).

However, when the CMB heat flux F_CMB becomes lower than adiabatic, core convection no longer occurs (as evidenced by no magnetic field on Venus and Mars) and thus the core temperature profile is not adiabatic. F_CMB can even become negative in models with a layer of dense heat-producing-element (HPE)-enriched material above the CMB: assuming this heats the entire core uniformly is unrealistic as heating from above is a very inefficient way of heating a layer. Another end-member approximation is to decouple the core and mantle temperatures in the latter case (Cheng et al, 2025 JGR).

To treat cases where F_CMB is sub-adiabatic or negative, a 1-D conductive core model is presented. When the temperature profile is adiabatic to super-adiabatic, an eddy diffusivity acting on the super-adiabatic temperature parameterizes heat transport by turbulent convection and keeps the temperature profile very close to adiabatic (see Abe, 1997 PEPI). When the temperature profile is sub-adiabatic, normal thermal diffusion is the dominant heat transport process. Compressibility, crystallization of an inner core and the presence of light elements are included.

A MATLAB implementation is presented. Then, results from coupling this 1-D core model to 2-D thermo-chemical mantle evolution models using StagYY (Tackley, 2008 PEPI) are presented. When F_CMB is always super-adiabatic, similar results are obtained for 1-D and 0-D models, but:

(i) Results for a post-giant-impact core superadiabatic temperature profile with the outermost core extremely hot were presented by Tackley (2025 AGU Meeting; https://agu.confex.com/agu/agu25/meetingapp.cgi/Paper/1909859). A thin, convecting layer forms at the top of the core and rapidly thickens until the whole core becomes adiabatic again.

(ii) For an HPE-enriched dense layer above the core-mantle boundary the layer and CMB temperatures to rise quickly if the core is decoupled from the mantle, slowly for a 0-D coupled core model, and at an intermediate rate with this 1-D core model. The layer temperature has implications for the formation of plumes, as well as other thermal evolution characteristics.

In conclusion, the new 1-D core model facilitates more realistic core-mantle coupled evolution simulations in the case that CMB heat flux is lower than that conducted down the core adiabat or even into the core.

How to cite: Tackley, P. J.: A one-dimensional core model for coupling to mantle convection simulations: Equations and results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5829, https://doi.org/10.5194/egusphere-egu26-5829, 2026.

Terrestrial planets—Mercury, Venus, Earth and Mars—formed by the accretion of smaller objects, each planet with their own timescale. The Earth was probably the latest terrestrial planet to form and reached about 99% of its final mass within about 60–100 Myr after condensation of the first solids in the Solar System. This contribution examines the disproportionate role of the last approximately 1% of Earth’s growth, or late accretion, in controlling its long-term interior evolution, and in particular metal-silicate mixing and bulk volatile budget. 

The coupling of impact and geodynamical simulations reveals underappreciated consequences of Earth’s late accretion with implications for a correct interpretation of the geochemical and geodynamical properties of the present Earth’s mantle. Similar implications are expected for Venus and Mars, and are also likely to occur and modulate the interior evolution of rocky exoplanets.

How to cite: Marchi, S. and Korenaga, J.: The shaping of the terrestrial planet’s interiors by late accretions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5902, https://doi.org/10.5194/egusphere-egu26-5902, 2026.

Early planetary accretion and giant impacts likely generated a global magma ocean on the proto-Earth, enabling extensive dissolution of primordial volatiles from the solar nebula into silicate melts. During subsequent core-mantle differentiation, the partitioning of noble gases between pyrolitic silicate melts and iron-sulfur (Fe-S) melts would have controlled their redistribution and long-term preservation in Earth’s deep interior. The contrasting noble gas signatures observed in mid-ocean ridge basalts and mantle plume sources, particularly in He/Ne ratios, motivated the existence of a deep primitive reservoir potentially linked to early core-mantle differentiation. Here, we use ab initio molecular dynamics simulations combined with thermodynamic integration to quantify the partition coefficients of He, Ne, Ar, Kr, and Xe between pyrolitic silicate melts and Fe-S melts. We further assess the effects of melt composition by comparing pyrolite with MgSiO₃ melts and Fe-S with metallic iron melts. Our results reveal systematic variations in noble gas partitioning with atomic size and melt chemistry. Based on these partitioning coefficients, we estimate the potential noble gas inventories preserved in the mantle and core. These results provide new quantitative constraints on the fate of primordial noble gases and the origin of deep-mantle volatile reservoirs.

How to cite: Zhao, Y., Wang, T., Caracas, R., Wang, W., and Wu, Z.: Fate of primordial noble gases during core-mantle differentiation from ab initio simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7052, https://doi.org/10.5194/egusphere-egu26-7052, 2026.

Geodynamic models require constraints from phase equilibria to infer how changes in phase abundance and composition affect physical properties. When applying such models on a planetary scale, performance becomes especially crucial. Therefore, computationally costly methods, such as Gibbs free energy minimisation, are no longer a viable option for predicting phase equilibria directly. We present a machine learning (ML) surrogate that can approximate phase equilibrium predictions for silicate mantles of rocky planets. ML surrogates have proven to be useful tools for approximating complex physics-based simulations in various fields, as they are computationally efficient, highly scalable, and fully compliant with GPU-based computation in high-performance computing clusters and automatic differentiation.

We calibrated a neural network surrogate on a large synthetic dataset (n = 2.0×10⁶) generated using MAGEMin (Riel et al., 2022) and the thermodynamic dataset from Stixrude and Lithgow-Bertelloni (2022). The training dataset ranges over typical upper to transition-zone mantle conditions in terms of pressure, temperature, and bulk rock composition. The model architecture and calibration strategy presented can accurately predict the molar proportions and molar oxide composition of multicomponent solid solutions from pressure, temperature, and bulk rock composition. Constraints on mass balance and closure of compositional variables are actively enforced during calibration through additional physics-informed misfits, in addition to the data-driven convergence. Evaluation of the model indicates uncertainties of less than ±0.02 molmol^-1 for the prediction of phase fractions and less than ±0.005 molmol^-1 for most compositional variables within solid solutions for the phases considered. The performance assessment shows a systematic increase in computational speed of two orders of magnitude when comparing the prediction between the ML surrogate and MAGEMin. Moving the computation to a GPU can improve performance by up to 5 orders of magnitude, <100ns per point, for large data sets of 10⁵ points, compared to the Gibbs free energy minimiser.

In this presentation, the ML surrogate will be used to map the stability of wadsleyite, ringwoodite and akimotoite within the Martian mantle. This ultra-fast prediction method enables the incorporation of poorly constrained minor components (e.g. Na₂O) using a Monte Carlo approach. Our results demonstrate the significant influence of these minor components on phase stability. This, in turn, determines seismic velocities and can be associated with water storage in nominally anhydrous minerals.

[1] Riel, N., Kaus, B. J. P., Green, E. C. R., & Berlie, N. (2022). MAGEMin, an efficient Gibbs energy minimizer: Application to igneous systems. Geochemistry, Geophysics, Geosystems, 23.

[2] Stixrude, L. & Lithgow-Bertelloni, C. (2022), Thermal expansivity, heat capacity and bulk modulus of the mantle, Geophysical Journal International, 228 (2), 1119–1149. 

How to cite: Hartmeier, P. and Lanari, P.: Machine learning is all you need: A surrogate model for phase equilibrium prediction for planetary-scale models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7087, https://doi.org/10.5194/egusphere-egu26-7087, 2026.

The formation and earliest evolution of a secondary atmosphere is tightly linked to its underlying magma ocean. Our current understanding of this coupled evolution is mainly built on thermal evolution coupled to chemical equilibrium models, which inherently assumes instant chemical exchange between the atmosphere and magma ocean. However, some recent numerical models [1,2] have challenged this assumption.  In this work, we address the issue both theoretically and numerically.

Volatile transport within the bulk of the magma ocean can, to a certain extent, be approximated as a passive particle diffusion process. Even when the buoyancy of volatiles is neglected, we demonstrate through two complementary approaches that the bulk transport is rapid. First, we extend a theoretical model for turbulent diffusion whose predictions align well with numerical simulations, which enables to replace empirical constants with more fundamental parameters. When extrapolated to magma ocean conditions, the characteristic diffusion timescale is found to be significantly shorter than the expected lifetime of the magma ocean. Second, we perform numerical experiments by initializing a passive scalar field at mid-depth in a statistically steady-state turbulent convection simulation. The evolution of its distribution, governed by an advection-diffusion equation, shows that the initial central peak flattens within just a few free-fall time units, which is a direct indicator of vigorous turbulent mixing.

The seemingly inefficient transport observed in some recent studies may be attributed to the behavior of a compositional boundary layer, which forms in conjunction with a laminar velocity boundary layer near the top surface. We analytically derive the composition flux across a no-slip boundary layer, which is supposed to scale with the chemical diffusivity and the square root of a characteristic Reynolds number. Numerical simulations show good agreement with this prediction. Nonetheless, this boundary-layer bottleneck is unlikely to significantly limit vertical volatile transport under realistic magma ocean conditions, for several reasons:
- Volatile parcels could grow in size as they approach the boundary layer, when buoyancy becomes significant and  the "passive particles" assumption no longer holds
- Even a no-slip boundary layer can be turbulent at the relevant extremely high Rayleigh number, where vertical transport is much more efficient than in a low-Ra laminar boundary layer
- The atmosphere-magma ocean interface is a free-surface, instead of a no-slip or free-slip wall

Building on recent findings that rotation significantly alters magma ocean dynamics (e.g., [3]), our future research will incorporate rotational effects to develop a more comprehensive understanding of volatile transport efficiency.

References:
[1] Salvador, A. & Samuel, H.  Icarus 390, 115265 (2023).
[2] Walbecq, A., Samuel, H. & Limare, A. Icarus 434, 116513 (2025).
[3] Maas, C. & Hansen, U. EPSL 513, 81–94 (2019).

How to cite: Yang, X., Gillmann, C., and Tackley, P.: Efficient volatile exchange between atmosphere and magma ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7098, https://doi.org/10.5194/egusphere-egu26-7098, 2026.

Recent analyses of seismic data recorded on Mars suggests a heterogeneous mantle where a global molten silicate layer lies above the core, followed by a partially crystallized layer (Samuel et al., 2023). The formation of such mantle structure is inherently link to the planet's early evolution when a global magma ocean was present and its crystallization process. Previous studies have shown that mantle overturn events during/after crystallization can produce a silicate layer enriched in iron and heat-producing elements that resides above the core-mantle boundary (CMB) (e.g., Tosi et al., 2013; Plesa et al., 2014; Samuel et al., 2021). However, processes such as melt transport, phase change, and chemical fractionation are not accounted for which are important in the describing the mantle's long-term evolution. By accounting for the aforementioned processes (Boukaré et al., 2025), we show that for the first time, a stratified melt layer can be formed and preserved over geological timescales in a self-consistent model. We observe that during the early stages of solidification, iron-rich silicates produced by chemical fractionation at the shallow mantle are delivered to the CMB. The presence of iron-rich materials at the CMB not only reduces the melting temperature of the silicates, but also produces a stably stratified melt structure at the bottom of the mantle that is resistant to chemical and thermal erosion over long timescales.

How to cite: Lim, K. W., Boukaré, C.-É., Samuel, H., and Badro, J.: The Formation of Mars' Basal Melt Layer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7328, https://doi.org/10.5194/egusphere-egu26-7328, 2026.

Evolution of deep mantle reservoirs after the magma ocean: the influence of melt extraction

Laura Lark, ChEd Boukaré, James Badro, Henri Samuel

Earth’s magma ocean stage and aftermath likely produced a reservoir of iron and trace element enriched silicate melt at the base of the mantle, termed a “basal magma ocean” (BMO) (Boukaré et al., 2025; Labrosse et al., 2007). As the BMO crystallized, its cumulates would likely be buoyant both because iron would behave somewhat incompatibly and because melt under extreme pressure is compressed to similar (or even higher) density than crystal of the same composition (Caracas et al., 2019). Consequentially, BMO crystallization would have been self-limiting, in that heat loss is necessary for crystallization to progress, but crystallization forms a layer of cumulates which insulate the BMO, reducing heat loss. Therefore, the evolution of the cumulates of the BMO interacting with convection in the overlying mantle is extremely important for the thermal evolution of the deep planet, with implications for BMO longevity and core dynamo generation.

We investigate the co-evolution of the BMO, its cumulates, and the overlying mantle with the fluid dynamics code Bambari (Boukaré, 2025) which incorporates melting, melt-crystal fractionation, and melt migration into a mantle convection model with coupled core (0-D heat reservoir). We are exploring the evolution of cumulates from the freezing BMO and how this affects BMO heat loss. For example, we vary the initial concentration of heat-producing elements in the BMO vs. solid mantle (γ) and observe that piles form preferentially in models with a more strongly heated basal magma ocean. At the base of piles, melting and drainage of iron-rich melts results in overall depletion of iron from piles. The lower density reinforces piling behavior, which strengthens melting and iron drainage (Figure 1). We are continuing to evaluate regimes of piling and implications for heat loss and interaction with the overlying mantle.

Figure 1. Snapshots of model mantle composition, cropped to show deep mantle only. Piles in convecting mantle overlie freezing basal magma ocean (white above melt fraction of 0.9). Model with more strongly heated BMO (higher ) shows more depleted upwellings within piles (yellow arrows).

References

Boukaré, C.-É., Badro, J., & Samuel, H. (2025). Solidification of Earth’s mantle led inevitably to a basal magma ocean. Nature, 640(8057), 114–119. https://doi.org/10.1038/s41586-025-08701-z

Caracas, R., Hirose, K., Nomura, R., & Ballmer, M. D. (2019). Melt–crystal density crossover in a deep magma ocean. Earth and Planetary Science Letters, 516, 202–211. https://doi.org/10.1016/j.epsl.2019.03.031

Labrosse, S., Hernlund, J. W., & Coltice, N. (2007). A crystallizing dense magma ocean at the base of the Earth’s mantle. Nature, 450(7171), 866–869. https://doi.org/10.1038/nature06355

How to cite: Lark, L., Boukaré, C.-E., Badro, J., and Samuel, H.: Evolution of deep mantle reservoirs after the magma ocean: the influence of melt extraction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7578, https://doi.org/10.5194/egusphere-egu26-7578, 2026.

The Lunar crustal dichotomy, expressed in farside-nearside differences in crustal thickness, volcanism and surface composition, does not yet have a well-established origin. Multiple mechanisms proposed in the literature can explain some aspects of the dichotomy; however no single model is able to fully explain the entirety of its observed features. We hypothesize that all aspects of the dichotomy are related and originate from the solidification of the Lunar Magma Ocean (LMO). Given that the dichotomy is aligned in reference to Earth, we investigate if Earth’s tidal influence on the LMO, when the Moon was in proximity to the Roche limit, can explain this dichotomy.

We investigate this hypothesis with numerical models of lunar evolution, using a modified version of StagYY (Tackley, 2008) that includes three-dimensional gravity accounting for tidal effects. We model the LMO solidification starting from a fully molten Moon, followed by the onset of solid-state mantle convection.  

Our models show that an asymmetric degree-two convection pattern can emerge during the early stages of the LMO solidification. This tide-driven magma ocean convection is characterized by two large plumes on the nearside and farside, with downwelling in the perpendicular plane at the poles. The nearside plume upwells faster than the farside plume given the asymmetries in the tidal forces between each side of the Moon. This convection pattern inhibits both the solidification of the LMO, and the compaction of the solid fraction, resulting in a convecting mush. Melt segregates towards the sides of the plume heads, where velocities are lowest, forming a low crystallinity magma ocean that is continuously replenished by decompression melting of the mostly solidified mantle that rises through the plumes. The LMO solidifies near the surface as material travels towards the perpendicular plane and subducts, creating a barrier that isolates the two hemispheres. Differences in the timing of melt segregation and the rate of decompressive melting eventually create significant hemispheric chemical contrasts, which ultimately can lead to all observed aspects of the crustal dichotomy of the Moon.

Reference

Tackley, P. J. (2008). Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid. Physics of the Earth and Planetary Interiors, 171(1-4), 7-18.

How to cite: Astudillo, D., Tackley, P., and Lourenço, D.: Tide-Driven Magma Ocean Convection as the Origin of the Lunar Crustal Dichotomy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7700, https://doi.org/10.5194/egusphere-egu26-7700, 2026.

How the very early Earth lost its internal heat remains a subject of debate. Early Earth may have been characterized by extensive magmatism due to a hot mantle, which then acted as the primary heat loss mechanism, or been more volcanically quiescent, where heat conduction through the lithosphere served as the primary heat loss mechanism. The primary mode of early Earth heat loss would then strongly influence tectonics and crust formation, the long-term thermal evolution of the interior, and surface environments where life could originate in the Hadean or Eoarchean.

Our recent crustal evolution model suggests that mantle melt production and mafic extrusive volcanism must have been limited prior to 3.6 Ga to remain consistent with Hf isotope data. We hypothesized that these geochemical constraints require a 'quiescent Earth' with a low melt production rate (<0.6 mm/yr). However, the actual magma supply is governed by complex geodynamic factors: specifically, the mechanics of melt generation, ascent, and accumulation at the mantle-crust boundary. Understanding these physical mechanisms is critical, particularly when evaluating high-flux regimes such as heat-pipe tectonics, which may be incompatible with the low rates inferred from the geochemical record.

A critical phenomenon affecting this supply is the formation of a decompaction layer beneath the mantle-crust interface (Sparks and Parmentier, 1991). Since the crust acts as a rigid thermal boundary, temperatures drop rapidly near this interface. Consequently, ascending melt encounters a freezing horizon that acts as a permeability barrier, causing it to accumulate. Within this zone, the decompaction layer and accumulated magma generate significant melt overpressure relative to the solid matrix, driving magma into the plumbing system and initiating ascent. Therefore, characterizing the dynamics of the decompaction layer is crucial for understanding the physical controls on melt supply.

Recent numerical modeling of Io, an active heat-pipe body (OReilly and Davies, 1981), demonstrates that crustal thermal structure is controlled by the physics of two-phase melt transport (Spencer et al., 2020). This model suggests that magma transport is driven by mantle overpressure at the decompaction layer but limited by solidification within the plumbing system. Applying this physical framework to the Hadean, we tested which mantle dynamics and temperature ranges are compatible with the restricted melt fluxes required by the geochemical record. Preliminary results demonstrate the existence of a decompaction layer, where both effective pressure and extraction rates increase significantly with porosity. By systematically exploring the parameter space, we identify the specific mantle geodynamic conditions required to align plateau melting tectonics with the Hf isotope constraints.

How to cite: Kubota, Y., Rudge, J., and Foley, B.: The role of the mantle decompaction layer in Hadean volcanism, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7793, https://doi.org/10.5194/egusphere-egu26-7793, 2026.

Through Gibbs free energy solvers combined with published experimental data, we assess the structurally bound water capacity (s^H2O) of nominally anhydrous minerals, together with low and high pressure hydrous phases. These maps are implemented into a global mantle convection model to investigate the long-term evolution of the mantle water content (c^H2O). A parameter study spanning a range of yield stresses is performed, with particular emphasis on the role of surface mobility in controlling volatile exchange fluxes between the mantle and the atmosphere. Across multiple simulation ensembles, surface mobility emerges as the primary control on the intensity of ingassing between the two reservoirs. Time-series autocorrelation analysis of reservoir H₂O mass indicates that the mantle transition zone (MTZ) behaves as a transient, high-s^H2O layer that is unable to sustain long-lived hydrated states in the absence of frequent water-rich slabs penetrating beyond 410 km depth. Principal component analysis reveals divergence in simulation evolution as a function of surface yield stress, leading to distinct H₂O partitioning regimes between the MTZ and the lower mantle, with coupled increase in upper mantle c^H2O dominance. This highlights the tendency of episodic or stagnant-lid regimes to sequester water at greater mantle depths relative to tectonically active planets. Bottom-up integration of our model profiles suggests a total stored mantle H₂O in the order of 1–1.5 ocean masses, an amount significantly lower than previous estimates, resulting from the rapid decrease of s^H2O beyond 660 km depth and subsequent ease of outgassing. Because supercriticality-enhanced extraction processes are not included and a depth-dependent background permeability restricts vertical transport, this estimate should be regarded as an upper bound. We further find that the s^H2O associated with the perovskite phase is of first-order importance in determining total mantle water storage. Low convective velocities maintain relative water enrichment within the perovskite-dominated region, implying that deviations from the commonly assumed dry-perovskite composition may increase estimated storage by non-negligible amounts.

In addition, recent advances in high-pressure thermodynamic databases enable the assessment of oxygen fugacity profiles down to core–mantle boundary depths. Building on this framework, a separate suite of simulations explores a new carbon-tracking scheme that accounts for solid and molten reservoirs, redox-dependent melting interactions, and enhanced shallow magmatism, with the ultimate objective of coupling the deep carbon and water cycles.

How to cite: Moccetti Bardi, N. and Tackley, P.: Effects of Surface Mobility on Relevant Mantle H2O - C Fluxes and Distribution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8347, https://doi.org/10.5194/egusphere-egu26-8347, 2026.

Thermo-chemical mantle convection models featuring heterogeneous thermal conductivity indicate that heat-producing element (HPE) enrichment in large low shear velocity provinces (LLSVPs) significantly impacts the long-term stability of these regions. Because the rate of internal heating was more significant in the past, thermal conductivity's influence on thermal buoyancy (and bulk erosion) must have also been more substantial. Consequently, their initial volume may have been significantly larger than their present-day volume. Energy balance calculations suggest that a smaller initial mantle volume fraction of LLSVPs material supports more HPE enrichment than a larger mantle volume fraction to maintain the mantle's internal heat budget. For example, an initial layer thickness of 160km (~3% mantle volume) implies present-day HPE enrichment factors greater than ~45 times the ambient mantle heating rate (compared with more conservative factors of 10 to 20 for similar initial conditions employed in previous studies of thermo-chemical pile stability). Thus, HPE enrichment may have been significantly underestimated in earlier models of LLSVPs evolution. Conversely, and assuming that LLSVPs formed from a much larger reservoir, HPE enrichment may be overestimated based on the present-day LLSVPs volume. Our study considers LLSVPs with a primordial geochemical reservoir composition (consistent with an undegassed ⁴He/³He signature and HPE enrichment). We present thermo-chemical mantle convection models that feature time-dependent internal heating rates and HPE enrichment (implied by initial mantle volume fraction). In this new context, we re-examine, in particular, the impact of a fully heterogeneous thermal conductivity, including a radiative conductivity, on the stability of LLSVPs. We then calculate synthetic seismic shear-wave velocity anomalies from the final distributions in temperature and composition tomographic of our simulations, filter these anomalies with a tomographic filter built from tomographic model HMSL-SPP06, and examine their distribution together with the heat-flux patterns at the core-mantle boundary. Using LLSVPs' present-day volume and core-mantle boundary coverage as a constraint, we finally discuss potential initial conditions, heating scenarios, and thermal conductivity for an Earth-like model.

How to cite: Guerrero, J., Deschamps, F., Hsieh, W.-P., and Tackley, P.: Assessing the effects of heat-producing element enrichment and mantle thermal conductivity on the stability of primordial reservoirs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8865, https://doi.org/10.5194/egusphere-egu26-8865, 2026.

The geological record indicates that Earth has experienced rapid and drastic tectonic reorganizations, such as the breakup of Pangea and the global event at ∼50 Ma marked by the Hawaiian–Emperor bend and synchronous kinematic shifts across all major plates (Whittaker et al., 2007). The mantle lithosphere system is a complex nonlinear dynamical system (Coltice, 2023) that can produce such tectonic transitions (Janin et al., 2025; Guerrero et al., 2025). By analogy with the climate system, which alternates between icehouse and hothouse states, a fundamental question arises: can plate tectonics exhibit multistability, and if so, does the whole mantle-lithosphere system as well?

Here we investigate dynamical transitions in mantle convection with self-consistent plate tectonics using tools from dynamical systems theory. We analyze outputs from 3D spherical mantle convection model of Coltice et al. (2019), which reproduces major tectonic features of Earth. From a 850 Myr long simulation, we construct a database of tectonic and physical variables, including plate-boundary lengths, number of plates, proportion of deforming lithosphere, global and surface root-mean-square velocities, surface and core–mantle boundary heat fluxes, mean mantle temperature, number of mantle plumes, and lithospheric net rotation rate.

We apply two complementary methods to detect dynamical transitions: (1) sample-based tests using Maximum Mean Discrepancy (MMD; Gretton et al., 2012), which identify statistical discontinuities in multidimensional distributions, and (2) Recurrence Quantification Analysis (RQA; Eckmann et al., 1987), which characterizes changes in recurrence patterns within the system’s phase space. We perform analyses separately on surface variables, mantle variables, and the combined dataset.

We identify four statistically significant transitions. Some coincide with major tectonic reorganizations, such as supercontinent assembly and breakup or global kinematic shifts, while others reflect intrinsic changes in convective or tectonic regimes. Certain transitions affect both mantle and surface dynamics synchronously, whereas others are confined to either the lithosphere or mantle flow. To interpret these transitions, we combine Principal Component Analysis (PCA) with spectral analyses of mantle thermal heterogeneity. In this framework, detected transitions correspond to shifts in one or more principal components representing distinct tectonic, thermal, and kinematic states of the system, providing quantitative evidence for multistability in mantle-plate dynamics.

How to cite: Jaah, I., Coltice, N., Janin, A., and Flament, N.: Tectonic Reorganizations and Multistability of the Mantle-Plate System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9605, https://doi.org/10.5194/egusphere-egu26-9605, 2026.

Rock-deformation laboratory experiments have shown that upper mantle flows with a combination of different creep mechanisms making its rheology composite (Karato & Wu, 1993; Hirth & Kohlstedt, 2003). At low stress levels in the cold and deep upper mantle, deformation occurs by diffusion creep where diffusive mass transport happens between grain boundaries. Whereas at relatively high stress levels in the hot regions of the uppermost mantle, deformation occurs by dislocation creep where crystalline dislocations move between grains. Although composite rheology has been considered in some recent global-scale geodynamical studies of rocky planets (e.g., Dannberg et al., 2017; Schierjott et al., 2020; Tian et al., 2023; Arnould et al., 2023), its influence on the thermo-compositional evolution and tectonic regime of early Earth remains unexplored.

In this study, the code StagYY (Tackley, 2008) is used to model the thermochemical evolution of solid Earth with three different rheological setups. In the first rheological setup, viscous deformation includes only diffusion creep. In the second setup, deformation is accommodated by a combination of diffusion creep and stress-dependent dislocation creep. In the third setup, a proxy for dislocation creep viscosity is used, which resembles temperature- and pressure-dependent Newtonian flow viscosity, where activation energy and activation volume relate to laboratory-estimated dislocation activation parameters divided by the stress exponent, representing dislocation creep with a constant strain rate. Such an approximation has been demonstrated to be a reasonable proxy of power-law viscosity in the classical modelling work by U. Christensen (1983, 1984).

These models self-consistently generate oceanic and continental crust, consider both plutonic and volcanic magmatism and incorporate pressure-, temperature-, and composition-dependent water solubility maps. Irrespective of the rheology considered, models exhibit mobile-lid regime with high mobility (ratio of rms surface velocity to rms velocity of mantle) with plume-induced lithospheric subduction for the initial 200-300 Myr. Afterwards, they transition to episodic-lid or ridge-only regime and are characterised by global resurfacing events. When compared to models with only diffusion creep rheology, models with composite rheology (either as stress dependent dislocation creep or dislocation creep proxy) have higher surface mobilities, experience resurfacings more frequently, produce more continental crust, and are more efficient at planetary cooling. These trends stay similar even in models that do not consider melting. In terms of code performance, computations with composite rheology take longer than just with diffusion creep. However, dislocation creep proxy models are faster than stress-dependent dislocation creep models by a factor of ~1.6x. In summary, a combination of diffusion and dislocation creep proxy is a viable formulation to realistically model long-term thermochemical planetary evolution with relatively low additional computational expense.

How to cite: Jain, C. and Sobolev, S.: Influence of composite rheology on planetary dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9998, https://doi.org/10.5194/egusphere-egu26-9998, 2026.

Large Igneous Province (LIP) volcanism is a major driver of past global change via degassing of large volumes of climate-altering and poisonous gases (such as H₂O, CO₂, CH₄, SO₂). These volatile species can produce contrasting effects on the atmosphere, from long-term global warming to short-lived volcanic winters. We know from historical cases (e.g., the 1783–84 Laki fires, the 1991 Pinatubo eruption) that sulfur-rich eruptions can produce global cooling with societal consequences. In deep time, repeated volcanic winters occurring during LIP emplacement, superimposed on long-term warming, could have stressed ecosystems and contributed to mass extinction, but their short duration makes them difficult to detect in the stratigraphic record (Callegaro et al., 2020; 2023; Kent et al., 2024). Sedimentary proxies of short-term cooling such as glendonite crystallization are being explored, but their signals remain ambiguous (Vickers et al., 2020). We propose a complementary, “within-magma” approach for tracing sulfur-rich magmatic pulses capable of generating volcanic winters. Using synchrotron X-ray microfluorescence, we measure sulfur concentrations in clinopyroxene from LIP magmas, and calculate equilibrium melt concentrations with established partition coefficients. Since clinopyroxene is an early and almost ubiquitous phase in LIPs magmas, this method allows the detection of variations in sulfur budgets throughout the stratigraphy of a lava pile, identifying intervals of sulfur-rich lavas as potential drivers of volcanic winters. We discuss future developments of the method, and results obtained for magmas of the Deccan Traps (Western Ghats lava pile, India), and Franklin large igneous province.

Callegaro, S., Geraki, K., Marzoli, A., De Min, A., Maneta, V. & Baker, D. R., 2020. The quintet completed: The partitioning of sulfur between nominally volatile-free minerals and silicate melts. American Mineralogist 105, 697–707.

Callegaro, S., Baker, D. R., Renne, P. R., Melluso, L., Geraki, K., Whitehouse, M. J., De Min, A. & Marzoli, A., 2023. Recurring volcanic winters during the latest Cretaceous : Sulfur and fluorine budgets of Deccan Traps lavas. Science Advances 9, 1–12.

Kent D.V., Olsen, P.E., Wang, H., Schaller, M.F., Et-Touhami, M. 2024. Correlation of sub-centennial-scale pulses of initial Central Atlantic Magmatic Province lavas and the end-Triassic extinctions. Proceedings of the National Academy of Sciences U.S.A. 121, e2415486121.

Vickers M.L., Lengger, S.K., Bernasconi, S.M., et al., 2020. Cold spells in the Nordic Seas during the early Eocene Greenhouse. Nature Communications, 11, 4713.

How to cite: Callegaro, S., Baker, D. R., Geraki, K., De Min, A., Melluso, L., Marzoli, A., Capriolo, M., Deegan, F. M., Caraffini, F., Bédard, J., Davies, J. H. F. L., Boscaini, A., and Renne, P. R.: Sulfur-in-clinopyroxene: tracing potential volcanic winters in deep time from a within-magma perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11141, https://doi.org/10.5194/egusphere-egu26-11141, 2026.

The solubility of various volatiles in magma oceans plays a significant role in the formation and evolution of planetary atmospheres. Using ab initio molecular dynamics simulations, we investigate the dissolution of various volatiles in a magma ocean with bulk silicate Earth composition under conditions relevant to both early Earth and exoplanetary systems.

We find that hydrogen is highly soluble in silicate magma oceans, and its solubility increases dramatically with pressure and temperature. In particular for exoplanets, like sub-Neptunes, this solubility influences the structure and functioning of the entire planet. It significantly alters the redox state of the system and causes a massive outflux of oxygen. The results are large-scale formation of water vapor and the release of other complex chemical species. This process profoundly impacts the thermal and chemical evolution of exoplanets, particularly sub-Neptunes, whose atmospheres may show observable spectral signatures linked to magma ocean interactions. At conditions characteristic to the beginning of the Hadean, the Earth’s magma ocean could have easily dissolved large amounts of hydrogen. As a result, the amount of water present in the early atmosphere was determined by a fine balance between water degassing and hydrogen solubility. Changes in the redox state of the magma at shallow conditions would further influence this balance.

With regard to noble gases and CO/CO2, our simulations show that they are profoundly incompatible in silicate melts. They easily degas under lower pressure conditions, particularly when they are present jointly in the melt. The partial pressures of either of these gases need to reach at least a couple GPa to prevent degassing. These results suggest that the magma ocean contributed to the CO2-reach atmosphere of the Hadean, by both limited ingassing in the aftermath of the giant impact, and by massive outgassing, once the magma ocean was put in place.

How to cite: Caracas, R.: Outgassing of the Hadean magma ocean: a computational perspective , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12545, https://doi.org/10.5194/egusphere-egu26-12545, 2026.

Large low shear-wave velocity provinces (LLSVPs) are degree-2, antipodal structures in Earth’s lowermost mantle that may play a key role in mantle convection and plate tectonics. However, the origin and timing of their degree-2 configuration remain poorly understood due to the lack of geological constraints (McNamara, 2019). Tidal evolution models predict that Earth’s length of day (L.O.D) increased from ~6 h to 24 h over geological time (Farhat et al., 2022), suggesting that centrifugal force could have significantly influenced early LLSVPs evolution. Here, we investigate this mechanism using 3D self-consistent thermochemical mantle convection models that incorporate centrifugal force, implemented with the code StagYY. In our models, L.O.D increases linearly from 6 h to 24 h over the full 4.56 Gyrs model time. We assume that LLSVPs originate from a uniform basal dense layer that are results of either magma ocean crystallization (Labrosse et al., 2007) or the Moon-forming giant impact (Yuan et al., 2023). We find that centrifugal force substantially accelerates the formation of degree-2 basal mantle structures. A subduction girdle centered at the equator and two basal mantle structures centered at the poles are observed in our models. These degree-2 structures emerge consistently across experiments with varying yield stresses and corresponding plate tectonic configurations. Thus, our simulations demonstrate that centrifugal force drives the formation of antipodal LLSVPs, further suggesting that the polar LLSVPs may subsequently migrate through true polar wander.

References:

Farhat, M., Auclair-Desrotour, P., Boué, G., Laskar, J., 2022. The resonant tidal evolution of the Earth-Moon distance. Astronomy & Astrophysics 665.

Labrosse, S., Hernlund, J.W., Coltice, N., 2007. A crystallizing dense magma ocean at the base of the Earth’s mantle. Nature 450, 866-869.

McNamara, A.K., 2019. A review of large low shear velocity provinces and ultra low velocity zones. Tectonophysics 760, 199-220.

Yuan, Q., Li, M., Desch, S.J., Ko, B., Deng, H., Garnero, E.J., Gabriel, T.S.J., Kegerreis, J.A., Miyazaki, Y., Eke, V., Asimow, P.D., 2023. Moon-forming impactor as a source of Earth’s basal mantle anomalies. Nature 623, 95-99.

How to cite: Shi, Z., Li, Y., and Zhu, R.: Centrifugal force drives the formation of the antipodal basal mantle structures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12628, https://doi.org/10.5194/egusphere-egu26-12628, 2026.

Accretion and early differentiation processes have left Earth's mantle in a chemically heterogeneous state at the end of the Hadean. Since then, these primordial heterogeneities have been progressively erased by mantle convection stirring. This is well-illustrated by short lived isotopic systems such as ¹⁴⁶Sm-¹⁴²Nd: mantle-derived rocks 2.7 to 4.0 Gy old have been found with measurable anomalies in ¹⁴²Nd/¹⁴⁴Nd, while younger rocks show no detectable deviations from the mantle average. This indicates that convective stirring within the mantle has reduced the level of heterogeneities below the instrumental detection limit in ~1.8 Gy since Earth's formation. These observations have the potential of giving constraints on the mantle stirring rate in the Archean, and therefore on the mantle's dynamical state. However, the survival time of an heterogeneity depends not only on the mixing rate, but also on the initial level of heterogeneity and instrumental detection limit. For these reasons, and also because of the relative scarcity of available data, the observed survival time cannot be simply translated into a mantle stirring time. A quantitative interpretation of the geochemical data in terms of stirring rate requires comparison with a model that can predict the evolution of the probability density function (PDF) of the abundance of a geochemical tracer (or, equivalently, histograms of concentration), as a function of the convective regime and characteristics of the initial heterogeneity. We present here an analytical model for the time evolution of the PDF of a chemical tracer that is initially heterogeneously distributed. The model predictions compare very well with results from numerical simulations. This provides a solid physical basis for interpreting ¹⁴²Nd/¹⁴⁴Nd variations in terms of mantle dynamical state.

How to cite: Deguen, R.: Mixing of a passive heterogeneity by mantle convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14260, https://doi.org/10.5194/egusphere-egu26-14260, 2026.

Plate tectonics is a characteristic feature of Earth, but its initiation and early evolution remain debated. Geological and geochemical evidence suggests that plate tectonics was initiated from a stagnant-lid regime in the Archaean, however mechanisms associated with this transition are unclear. Previous geodynamic models, which typically assume fixed lithospheric strength, require a low effective yield-stress rheology to obtain plate-like behaviour, inconsistent with laboratory measurements. Here, we apply a global-scale mantle convection model that incorporates a temperature-dependent friction coefficient, representing thermodynamic weakening on fault planes during rapid slip (Brantut & Platt, 2017), to study the tectonic evolution of Earth-like planets. As the timescales of geodynamic models and fault motion differ by several orders of magnitude, a simplified step-function approach is adopted, where reduced friction coefficients of 0.01~0.1 are applied below the temperature threshold to mimic unstable fault motion (Karato & Barbot, 2018). Our results show that temperature-dependent weakening does not systematically promote stagnant-to-mobile lid transitions. Instead, plume-induced subduction serves as the dominant process to transition from an initial stagnant phase to plate-like lithospheric behaviour (mobile lid). We find that temperature-dependent friction coefficients can act as an additional weakening mechanism to promote subduction even at high lithospheric strengths. Unlike earlier models, which produced mobile-lid behaviour only under lithospheric strengths much lower than laboratory estimates, these findings demonstrate that more realistic rheological parameters can sustain mobile-lid behaviour when dynamic weakening is considered. We also find that subduction-zone locations are stabilised over time in cases with temperature-dependent friction coefficients. This behaviour is associated with localised lithospheric weakening in cold downwellings, and consistent with the stability of trench locations in plate reconstructions (Müller et al., 2019) as well as of seismically-observed lower-mantle structures (Torsvik et al., 2010). Our results provide a possible explanation for why plume-induced subduction on Venus, where high surface temperatures inhibit dynamic weakening, remains short-lived and localised, preventing plate tectonics.

References

Brantut, N., & Platt, J. D. (2017). https://doi.org/10.1002/9781119156895.ch9

Karato, S., & Barbot, S. (2018). https://doi.org/10.1038/s41598-018-30174-6

Müller, R. D., Zahirovic, S., Williams, S. E., Cannon, J., Seton, M., Bower, D. J., Tetley, M. G., Heine, C., Le Breton, E., Liu, S., Russell, S. H. J., Yang, T., Leonard, J., & Gurnis, M. (2019). https://doi.org/10.1029/2018TC005462

Torsvik, T. H., Burke, K., Steinberger, B., Webb, S. J., & Ashwal, L. D. (2010). https://doi.org/10.1038/nature09216

How to cite: Lam, P. W., Ballmer, M., and Zarebski, A.: The Effect of Temperature-dependent Strength of Lithosphere on the Earth's Tectonic Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14754, https://doi.org/10.5194/egusphere-egu26-14754, 2026.

In their hot initial phase, rocky planetary bodies undergo a magma ocean (MO) stage. Crystallisation of this magma ocean sets the initial structure of planetary mantles, and thus determines the early stages, and long term evolution, of solid-state mantle convection, thus regulating the litrhospheric tectonic, core convection and associated magnetic field. This major planetary differentiation process also controls the outgassing of the primary atmosphere, and therefore the long-term surface evolution and habitability. While several studies have addressed this crystallisation process from a mass-balance or a dynamical point of view, few have studied remelting of the convecting solid mantle while a magma ocean was still present. We here present spherical annulus numerical calculations of mantle convection and melting under a magma ocean to address the role of heterogeneity and dynamic recrystallisation on remelting and differentiation. Results indicate that the parameters that typically impact mantle convection (viscosity, density anomaly, etc) also impact the differentiation of the magma ocean. In particular, dynamic topography has a great influence on the composition of the magma ocean and its differentiation, as it conditions both, excess melting above upwellings (e.g. Figure 1) and excess crystallisation above downwellings. These topography effects are greater the closest the system is to a magma ocean overturn. Our findings can help to understand the differences between solar system bodies, such as the presence or absence of basal magma oceans in terrestrial bodies, or to predict the convective evolution of rocky exoplanets.

Figure 1: Effects of different MO density on mantle upwellings, the greater topography due to higher density of the MO  causes increased excess melting.

How to cite: Manjón-Cabeza Córdoba, A., Ballmer, M. D., and Shorttle, O.: Planetary controls on magma ocean crystallisation, re-melting and overturn, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18147, https://doi.org/10.5194/egusphere-egu26-18147, 2026.

Earth’s interior plays a fundamental role in the long-term evolution of the surface, climate, and biosphere. However, Earth's mantle evolution remains largely ambiguous, as imaging techniques are limited to present-day observations and geochemical or geological constraints apply to a non-global scale. Plate tectonic reconstructions coupled with convection models could provide constraints on the evolution of mantle structure. In this study, we employ both fully self-consistent and kinematically constrained mantle convection models^[1]. The mantle rheology is temperature-, pressure-, phase-, and stress-dependent, with the latter represented through pseudo-plasticity. The novelty of this work lies in employing a composite rheology with “realistic” rheological parameters^[2] in a fully three-dimensional geometry. By using both fully self-consistent models and plate-driven models, we aim to address the discrepancies in terms of long-term convective and tectonic behaviour that arise when forcing plate velocities onto the surface. The latter is done by imposing time-dependent surface velocity boundary conditions provided by a plate tectonic reconstruction^[3].

To evaluate the extent to which the models reproduce plate-like tectonics, we explore several independent constraints. In particular, we compute slab sinking rates and compare them to estimates inferred from seismic tomography^[4]. Slab sinking rates in self-consistent models provide insight into the mantle’s rheology. For example, sinking rates that are lower than those based on tomographic and geological data may indicate an overly viscous mantle. Our results show that the slab sinking rate is generally higher in models with imposed plate velocities compared to fully self-consistent models. Furthermore, a tessellation algorithm^[5] will be applied to the surface of the models to detect plates in the self-consistent models with plate-like behaviour. Based on these results, a plate-size frequency distribution can be calculated and compared to present-day Earth^[6]. Results show that low yield stresses generate too many small plates, and too few large plates [Fig. 1]. In order to generate Earth-like plate tectonics, yield stress needs to be sufficiently high to reproduce the plate-size frequency distribution of present-day Earth, but also sufficiently low to facilitate a long-term mobile lid regime.

^[1] Tackley, P. J. (2008). Phys. Earth Planet. Inter. 171, 1–4.

^[2] Tackley, P. J., Ammann, M., Brodholt, J. P., Dobson, D. P., & Valencia, D. (2013). Icarus 225, 50–61.

^[3] Merdith, A. S., Williams, S. E., Collins, A. S., et al. (2021). Earth-Sci. Rev. 214, 103477.

^[4] Van der Meer, D. G., van Hinsbergen, D. J. J., & Spakman, W. (2018). Tectonophysics 723, 309–448.

^[5] Janin, A., Coltice, N., Chamot-Rooke, N., & Tierny, J. (2025). Nat. Geosci. 18, 1041–1047.

^[6] Bird, P. (2003). Geochem. Geophys. Geosyst. 4, 2001GC000252.

How to cite: Metternich, M., Tackley, P., Arnould, M., and Janin, A.: Rheological Controls on the Plate-Mantle System: Self-Consistent vs. Kinematically Constrained Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18572, https://doi.org/10.5194/egusphere-egu26-18572, 2026.

Radiogenic heating plays a crucial role in shaping a planet’s evolution and dynamics. On Earth, ~50% of surface heat loss originates from the decay of three long-lived, heat-producing elements (HPEs): potassium, thorium, and uranium. These elements are strongly lithophile and preferentially concentrate in the silicate mantle of planets. However, a recent study by Luo et al. (Science Advances, 2024) suggests that under the high-pressure, high-temperature conditions of core formation in large rocky planets (so-called super-Earths), these HPEs may become siderophile, partitioning preferentially into the iron core. The presence of HPEs in the mantles of super-Earths plays a crucial role in their internal dynamics. A feedback loop between internal heating, temperature, and viscosity regulates mantle temperature, adjusting viscosity to the value needed to facilitate convective loss of the radiogenic heat (Tackley et al., Icarus 2013). However, if these sources of radiogenic heat partition into the core, mantle convection in super-Earths becomes dominated by heat flowing from the core rather than by a mix of internal heating and cooling from above (as in Earth). Using 1D, parameterized mantle evolution models, Luo et al. (Science Advances, 2024) show that this shift leads to a sharp rise in core-mantle boundary (CMB) temperatures and an increase in total CMB heat flow, with significant implications for volcanism and magnetic field generation.

In this study, we perform mantle convection simulations using the StagYY code (Tackley, PEPI 2008), extending the models of Tackley et al. (Icarus, 2013) to include HPEs in the core, as suggested by Luo et al. (Science Advances, 2024). Our models are run in a 2D spherical annulus geometry and allow for melting at all mantle depths. We test different planetary masses, from 1 to 10 Earth masses, as well as different post-perovskite rheologies, (upper- and lower-bound, following Tackley et al. 2013, and interstitial rheology following Karato 2011), two tectonic regimes (stagnant and mobile-lid), and three mantle-to-core partitioning ratios of HPEs (0.1, 1, and 10). This work contributes to the growing understanding of the interior dynamics of super-Earths, and their implications on surface and atmospheric conditions, the presence of a magnetic field, and habitability potential.

How to cite: Lourenço, D. and Tackley, P.: Impact of Heat-Producing Elements in the Core on Super-Earth Evolution and Dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20916, https://doi.org/10.5194/egusphere-egu26-20916, 2026.

Rocky planets such as the Earth or Venus likely experienced at least one magma ocean (MO) episode, during which the silicate mantle was molten in part or in full due to the heat generated by accretion and radioactive heating. During this MO stage, volatile elements present in the magma degassed to form the secondary atmosphere. Better understanding this degassing process can help us constrain the duration of the MO stage, the volatile enrichment of the subsequent mantle and the conditions for habitability. 

The degassing process is typically assumed to be efficient, in equilibrium with the atmosphere: instant degassing of oversaturated fluid parcels in a well-mixed magma ocean. However, MO parcels may experience considerable delay in reaching the shallow pressures where bubbles can form and degas into the atmosphere.

We take into account this out-of-equilibrium degassing in a 1D interior model coupled to a radiative-convective CO2/H2O atmosphere. The model is parameterized using scaling laws derived from joint laboratory and numerical experiments. We explore a broad range of planet sizes, stellar radiation and CO2 and H2O initial concentrations, and examine the impact of rapid rotation akin to that of the early Earth.

Using this coupled model, we explore the impact of out-of-equilibrium degassing on atmospheric composition and habitability, the cooling time of the MO, and the volatiles trapped in the mantle.

How to cite: de Larminat, A., Samuel, H., and Limare, A.: Impact of out-of-equilibrium degassing of magma oceans on volatile trapping, solidification time and habitability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22000, https://doi.org/10.5194/egusphere-egu26-22000, 2026.

IR spectra of garnets from mantle xenoliths, diamond inclusions and UHP metamorphic rocks indicate that this mineral can be a principal participant in a water balance of the mantle and subduction zones. This conclusion is consistent with experiments showing that H₂O content in garnet increases with pressure and could reach up to >2000 ppm H₂O at the transition zone conditions (Liu et al., 2024; Chen et al., 2025). Although being controversial (dependent on starting materials, i.e. crystalline natural garnets vs. synthesized ones), available experimental data allow determination regularities of the H₂O solubility in garnet with respect to P, T, f_O2 and garnet composition. Present study shows an attempt to parametrize these regularities.

The parametrization is not possible for the experiments with starting crystalline garnets (Lu, Keppler, 1997; Zhang et al., 2022; Zhang, Yang, 2025). These data are not consistent between each other, and the reason for the inconsistency is not clear. The data on garnets synthesized from oxide mixtures are better self-consistent. 54 data points from (Geiger et al., 1991; Khomenko et al., 1994; Withers et al., 1998; Mookherjee, Karato, 2010; Fan et al., 2017; Bolfan-Casanova et al., 2000; Katayama et al., 2003; Thomas et al., 2015; Panero et al., 2020; Liu et al., 2021, 2024) represent intervals 2 – 25 GPa and 900 - 2000°C for a wide range of garnet composition including majoritic ones. The H₂O content (the Bell et al., 1995 calibration) in this set varies from 130 to 1620 ppm (the above mentioned data on the H₂O content >2000 ppm in garnet were excluded). The data were approximated with an equation DH - TDS + (p-1)DV – nRTlnf_H2O + RTlnC_H2O + W_Al*X_Al² + W_Si*X_Si² + W_Ca*X_Ca³ = 0, where C_H2O is the H₂O content in garnet, DH = 0 kJ/mol, DS = -92.96(±3.94) J/mol/K, DV = 0.475(±0.022) J/mol/bar are thermodynamic effects of the reaction Grt + nH₂O = Grt*nH₂O, f_H2O is a H₂O fugacity (Pitzer, Sterner, 1995), n = 0.5, W_Al = -30554.3(±4515) J/mol, W_Si = -81777.4(±29415) J/mol, W_Ca = -498078.1(±131842) J/mol, X_Al = [Al]/2 and X_Si = ([Si] - 3])/2 – Al and Si mole fractions in the VI site and X_Ca = [Ca]/3 – Ca mole fraction in the VIII site ([Al], [Si], [Ca] – a.p.f.u. per 12 О). The equation reproduces the H₂O content in garnet from 54 data points with a mean accuracy ±280 ppm.

Showing an increase of the H₂O solubility in garnet with pressure and a decrease with temperature, the equation predicts a solubility maximum, which is dependent on temperature (for pyrope, it is 2400 ppm at 18.5 GPa for 1000°C and 1270 ppm at 22 GPa for 1500°C). The H₂O solubility decreases with an increase of the majorite component in garnet. Following to these effects, the H₂O content in garnet in the upper mantle is expected to be about 600-800 ppm along the sub-cratonic geotherm.

The study is fulfilled under support of the RSCF project 23-17-00066.

How to cite: Safonov, O.: Water content in garnet: review of available experimental data and parameterization with respect to temperature, pressure and composition , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-173, https://doi.org/10.5194/egusphere-egu26-173, 2026.

Trachytes of the Deccan Traps from the Manori–Gorai area of Mumbai host numerous mafic enclaves which record magma chamber processes in continental flood basalt (CFB) settings. In this study, we undertook a comprehensive study, including petrography, mineral chemistry, whole-rock Sr-Nd isotope, in-situ trace elements and Sr isotopic analysis of the host trachyte (SiO₂ = 65-72 wt.%) and the mafic enclaves (SiO₂ = 45-52 wt.%) to understand magma chamber processes. A sharp-to-transitional hybrid mixed zone is evident between the host trachyte and enclaves, indicating mixing and mingling of two different magmas. Plagioclase and clinopyroxene are the major phenocrysts residing within a glassy groundmass. Plagioclase occurs as euhedral to anhedral grains, as inclusions, and within the groundmass across different zones. Clinopyroxene is predominantly augitic in composition throughout these zones. The wide compositional range from bytownite to sanidine indicates fractional crystallization coupled with heterogeneous magma mixing. Light rare earth element (LREE) enriched patterns (La_N/Sm_N = 3.4–5.4; Sm_N/Yb_N= 4.2–5.3), incompatible trace element enrichment, and whole-rock Sr–Nd isotopic compositions of both the enclaves (⁸⁷Sr/⁸⁶Sr_i = 0.70524–0.70536; ε_Ndi = +1.8 to +2.3) and trachyte (⁸⁷Sr/⁸⁶Sr_i = 0.70506–0.70511; ε_Ndi = +0.5 to +0.6) suggest derivation from a common parental magma, with minor crustal contamination recorded in the trachyte. In-situ trace element analyses and Sr isotopic ratios in feldspar (⁸⁷Sr/⁸⁶Sr_i = 0.7039–0.7056) further support a shared source affected by heterogeneous mixing. The observed geochemical trends in both the mafic enclaves and trachyte indicate recharge of mafic melt into an evolved, fractionated magma chamber, followed by buoyancy-driven ascent forming mafic enclaves at the interface.

How to cite: Halder, M., Mohan, M. R., Upadhyay, D., Shankar, R., and Bhunia, S.: A geochemical perspective of mafic enclaves in the Deccan Traps Continental Flood Basalts reveals magma chamber dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-678, https://doi.org/10.5194/egusphere-egu26-678, 2026.

Minerals from heavy concentrates from two phases of the Aykhal kimberlite pipe, Yakutia, were analyzed with the EPMA, SEM, and ICP-MS. They were used to reconstruct the mantle sections and their evolution, and to determine the features of the protokimberlite melts and melt/fluid metasomatic agents responsible for the geochemistry. A high amount of garnets belong to the dunitic type. The clinopyroxenes, as well as amphiboles, are Mg-rich and highly vary in Al, Cr, Ti, Na. Micas are Ti-biotites derived from protokimberlites. The ilmenites and chromites show domination of Mg- and Cr-rich compositions.

The mantle section of subcratonic lithospheric mantle (SCLM) for autholitic kimberlite breccia (AKB) reveals a long range of PT estimates for garnets from 8 GPa to Moho heated at the deeper part, showing in the P-Fe# plot sharp layering of 6 thick layers (subdivided to 2 sub-layers) visible by high Mg deviations and Ca fluctuations for garnets and grouping of PT points for other minerals. The lithosphere asthenosphere boundary (LAB) is marked by the ilmenite trend going from LAB to middle layer (4.5-3.5) GPa, traced by the Ti-augite and pyrope megacrysts. The minerals from tuffisitic kimberlitic breccia (TKB), show a similar division of the mantle section but amount of low-pressure pyrope and eclogite garnets is much higher.

The geochemistry of lherzolitic garnets show rounded curves of depletion in light rare earth elements (LREE) allows to subdivide them into the enriched, depleted, and common lherzolitic types. The megacrystic and low-crust garnets show higher HREE levels. The dunitic garnets reveal S-shaped, harzburgitic depressions in HMREE and curved patterns. All peridotitic garnets demonstrate U, Nb, Zr enrichment in multicomponent spider diagram (MSD). The Cr-diopsides show small U enrichment and pyroxenites with higher Th peaks Pb, Ba depressions. Ilmenites display very high Ta-Nb and Zr-Hf peaks and very low REE level except for two samples. The Cr-spinels demonstrate Ta peaks on the MSD. The phlogopites reveal Eu peaks and W-shaped REE distributions and high LILE in MSD. Diamonds show low REE levels and Pb peaks. The differences in TKB and AKB geochemistry of garnets and diopsides are in the higher level of the Th-Nb and Zr-Hf levels, showing the influence of the carbonate and H₂O-bearing melts that accompanied the interactions with the protokimberlite melts.

Reconstructed with partition coefficients, parental melts reveal highly inclined lines up to 1000/PM (primitive mantle). Peridotites show U-Ba- enrichment typical for subduction related melts and high Nb also – due to super plume melts influence. Cr-diopsides and pyroxenites show dominating Th enrichment due to interaction with the carbonatite melt.

  The high diamond grade of the Aykhal pipe is determined by mixing of subduction-related Na-Mn-U and peridotitic high Mg-Cr with Ti-Nb-Th plume components and hybrid melt interaction with peridotite eclogitic material with the mixing of all components.

 Work was done on state assignments of IGM SB RAS FWZN-2026-0007. Russian Science Foundation Grant (24-27-00411).

How to cite: Ashchepkov, I., Logvinova, A., Ivanov, A., Sotnikova, I., and Medvedev, A.: Mineralogy and geochemistry of the xenocrysts from Aykhal kimberlite pipe, Yakutia: comparison of phases, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3137, https://doi.org/10.5194/egusphere-egu26-3137, 2026.

Plateau, isochron and integral ages of 40Ar/39Ar xenocrysts and phlogopite grains from kimberlite xenoliths can be used to determine the ages of mantle processes (Hopp et al., 2008) and decipher the genesis of diamond-forming processes. Datings of deep xenoliths of kimberlites of the Siberian Craton reveal a significant spread (Pokhilenko et al., 2012; Solovieva et al., 2017b; Ashchepkov et al., 2015) from the Archean to a time close to the age of the host kimberlites, mainly Devonian. The oldest ages for the Udachnaya tr of the Daldyn field for phlogopites from xenoliths of spinel harzburgites of the uppermost level belong to the late Archean-early Proterozoic 2.1-1.5 Ga. In the Alakit field, all ages are younger than 1.6–1.05 and 0.928–0.87 Ga and belong to the metasomatic history of the Rodini mantle. Similar dates have been established for xenoliths from the Obnazhennaya trench (Kalashnikova et al., 2017).

Our 39Ar/40Ar data on micas often reveal complex spectral configurations. Micas from the Alakit field xenocrysts yield a series of peaks, beginning with the highest-temperature and oldest, which correspond to the Upper Proterozoic, Vendian, and Paleozoic, and only the lowest-temperature peaks with high Ca/K ratios correspond to kimberlite emplacement ages. Some peaks are possibly related to the thermal influence of the Vilyui plume (Kuzmin et al., 2012). The lowest temperature peaks are close in age to the time of kimberlite formation, which is confirmed by high 38Ar/39Ar ratios of gas released at the low-temperature stage, and can be used for dating kimberlites very approximately; however, the release of other gases at the low-temperature stages significantly increases the measurement error. All of them correspond to the interval 440-320 Mir, Internatsionalnaya, Ukrainskaya - 420, Yubileynaya - 342, and Botuobinskaya - 352); some determinations practically coincide with Rb/Sr ages (Griffin et al., 1999, Agashev et al., 2005, Kostrovitsky et al., 2008) and probably represent mixing lines. For many xenocrysts (Fainshteynovskaya, Ukrainskaya, Yubileynaya, and Krasnopresnenskaya pipes), the interval from 600 to 500 million years is manifested, which corresponds to the stage of breakup of Laurasia. The presence of relatively low-temperature plateaus with ancient ages and high-temperature young ones implies that some stages can be correlated with the mantle history of minerals.

How to cite: Iudin, D., Ashchepkov, I., and Travin, A.: Ages of micas from xenoliths and xenocrysts of kimberlites of the Siberian Craton determined by the 39Ar/40Ar method, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4754, https://doi.org/10.5194/egusphere-egu26-4754, 2026.

The ages for zircons from xenoliths of Cenozoic volcanics from TransBaikalia and Mongolia were determined by the same (LA-ICP-MS) aniCAP Q mass spectrometer (Thermo Scientific) and a NWR 213 in IGM SB RAS

The isotopic Pb/U and Pb/Pb ages  of the 6 zircon grains from the tuffs of the Bartoy volcano. They are plotting practically on  the207Pb/235U and 206Pb/238U concordia line (Figure 9). For the calculations ages the polynomial equations were used, obtained from the works of Khubanov et al., (2016-2024).

They may be divided into three groups. The ages of the zircons from tuffs 1160-1250 Ma mainly correspond to the meta-terrigenous rocks of the Shubutuiskaya Formation in the Khamar Daban zone (Gordienko et al., 2006). The Th/U ratio of 0.8-0.6 of these zircons corresponds to the common magmatic rocks, mainly of the basic type (Hawkesworth et al., 1997).

The ages near 800-860 Ma are determined for the suit from the metamorphic in Central Khamar-Daban (Shkol’nik et al., 2016). The collision events at the boundaries of the Paleoasian ocean occurred earlier in the Vend-Cambrian (Byzov, Sankov, 2024; Donskaya et al., 2013). Though some plutons with the model ages 1100-800 Ma were suggested by some authors to be referred to as collision. And elevated Th/U ratios of two zircons, 1.6-1.1, commonly correspond to the granites with the admixture of material of island arc environment with 3-5 Th/U ratios.

The age of granitic zircon, 300 Ma, just corresponds to the beginning of the Angaro-Vitim Batholith (AVP) formation (Tsygankov et al., 2010-2025). It may be connected to the movement of the superplume-formed kimberlites in Yakutia at the interval 420-340 Ma and later created the Biryusa and Tumanshet lamproites (Kostrovitsky et al., 2025) and later the Ingashi lamproites in Eastern Sayan ~306-309 Ma (Gladkochub et al., 2013). Further movement through Khamar-Daban and interaction with the lower crust and granulites brings to the creation of alkaline granitoids of AVP. But the Th/U ratio is rather low, 0.07, which commonly corresponds to the metamorphic type [90]; thus, they should be from granulites possibly remelted by a plume.

The ages of the granulite xenoliths from the Vitim picrobasalts (Ashchepkov et al., 2011) correspond to the initial stage of AVB.  And the next one, 873 may be correlated with the basic magmatism in Baikal uplift (Gladkochub et al., 2010).

In Shavaryn-Tsaram volcano two ages of zircons corresponds to Carboniferous stage 322 Ma of rifting in Mongolia (Kozlovsky et al., 2005) or close to last stage  AVP. The next one refers to the initial stage of Miocene plume magmatism (Ashchepkov et al., 2026).

The trace elements for two zircons determined in the granulites differ significantly. The inclined enriched in HREE pattern looks similar to carbonatitic zircons (Hardman, et al., 2025).  The next acid sample with La/Ybn <2 with  Eu minimum and without Ce anomaly. In MSD it shows the same peaks but without Y, Ta anomalies.

Work was done on state assignments of IGM SB RAS FWZN-2026-0007 and IG SB RAS. Russian Science Foundation Grant (23-17-00030).

How to cite: Tsygankov, A., Ashchepkov, I., and Burmakina, G.: The ages for zircons from xenoliths of Cenozoic volcanics from TransBaikalia and Mongolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4803, https://doi.org/10.5194/egusphere-egu26-4803, 2026.

Geochemistry and thermobarometry of mantle xenocrysts and xenoliths from Mir  kimberlite pipe were studied using new EPMA, SEM and LA ICP MS analyses

The PTX plot for the Mir pipe (Malo-Botuobinsky field) (Ashchepkov et al., 2010; 2014; 2019; 2022; 2023) shows the large interval from 8 to 1.1 GPa. The garnets show rathe narrow PT and P-Fe# but very wide P-Ca plots starting from the middle pyroxenitic layer to LAB. The Cr-Cpx and Cr-Sp are coinciding in Fe# in general. But the eclogites show very wide range of compositions trend. Diamond inclusions (DIA) (Sobolev, et al., 1976; 1997; Bulanova et al., 2002; Logvinova et al., 2004) the DIA pyropes have an opposite trend. In the P (GPa)-CaO plot largest variations in CaO are in the lower part of the mantle section. The most magnesian dunite varieties form an interval from 6.5 to 5 GPa, and then above them, the harzburgitic garnets again appear in the middle part of SCLM. There is high proportion of peridotite Cr-bearing varieties of ortho-and clinopyroxenes in the middle SCLM, which suggests that pyroxenites originated from peridotite partial melts. Omphacites together with garnets form an ascending P-Fe# plot. The geothermal conditions traced by DIA also form two branches. Even Cr-garnets partly trace the convective branch, although this is not evident in the middle part. The Cr-garnets are found at higher temperature conditions at deeper part of the SCLM. However, most of them plot between the 35–40 mWm−2 geotherms. The Cr-pyroxenites and Cr-diopsides form the colder branches to 35 mWm−2 geotherms or even lower. In the P-fO2 diagram, the less oxidized conditions correspond to the eclogitic clinopyroxenes in middle SCLM. At high pressures, the Cr-rich garnets give the lowest fO2 conditions.

The REE patterns of the pyropes show wide range of compositions from S-shaped dunitic to semi – rounded lherzolitic and flattened HREE harzburgitic and LREE enriched pyroxenitic. In multicomponent diagram they show peaks in Th-U and Pb and troughs in Sr and highly synchronously varying HFSE.

The Cpx form Gar lherzolites are showing several groups commonly inclined La/Ybn ~100 (normalization to primitive mantle (McDonough and Sun, 1995) with the hump at Ce- to Nd. In MCD they show very wide variations even in LILE from peak in Ba Rb to deep troughs and the same for U, Th. Pb, Sr. The HFSE are mostly moderately depleted (Zr <Hf) or deep minima Nb-Ta. Some low -Gar pyroxenites display less inclined patterns. There are more flattened patterns and REE -low for Sp lherzolites.

 The ilmenites in REE show different inclinations from positive (Lan ~100 and La/Ybn 70-100) to negative (Lan ~1-2 and La/Ybn ~0.1). They all show very high Ta-Nd peaks to 1000/PM and a bit less Zr-Hf (150-1000/PM).

Work was done on state assignments of IGM SB RAS FWZN-2026-0007. Russian Science Foundation Grant (24-27-00411).

How to cite: Vavilov, M., Ashchepkov, I., Medvedev, A., and Logvinova, A.: Geochemistry and thermobarometry of mantle xenocrysts and xenoliths from the Mir pipe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5851, https://doi.org/10.5194/egusphere-egu26-5851, 2026.

The Paleoproterozoic volcanic sequences of the Singhbhum Craton, Eastern India, encompass a broad compositional range, from ultramafic to felsic lithologies, and preserve important records of early subduction-related magmatism. This study investigates the petrogenesis of a newly identified Nb-enriched basalt (NEB) from the Kanjipani-Telkoi (KT) region, associated with the Malangtoli volcanics, offering key insights into mantle heterogeneity and slab melt-mantle interaction during the Paleo-Proterozoic era. The KT NEB is characterized by high niobium (Nb) levels, ranging from 7 to 29 ppm, along with elevated ratios of (Nb/Th)_PM (0.40-1.86), (Nb/La)_PM (0.29-0.82), and Nb/U (6.99-22.43). These geochemical features suggest that the NEB originated from the partial melting of a metasomatized mantle wedge that had interacted with subducting slab melts. Petrogenetic modeling suggests that the NEB compositions can be generated by ~5–20% partial melting of a metasomatized mantle wedge modified by interaction with high-silica, adakitic slab melts produced by ~15% partial melting of subducting oceanic crust. Furthermore, the chemistry of clinopyroxene in the NEB suggests crystallization at high temperatures, around 1016 to 1141 °C, at shallow to intermediate depths (1.6-7.6 kbar), consistent with conditions typical of a hot subduction environment. Collectively, these results provide robust evidence for Neoarchean–Paleoproterozoic arc magmatism in the Singhbhum Craton and underscore the critical role of slab-melt metasomatism of the mantle wedge in generating Nb-enriched magmas and promoting early continental crustal growth.

Keywords: Singhbhum craton, Nb-enriched basalt, clinopyroxene, slab melts, metasomatized mantle wedge, Partial melting.

How to cite: Sahoo, T. K. and Das, D. P.: Slab melt metasomatisation of a Paleo-Proterozoic mantle wedge: An insight from the geochemistry of rare Nb-enriched basalt of Singhbhum craton, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8209, https://doi.org/10.5194/egusphere-egu26-8209, 2026.

Cratons are ancient continental crust formed primarily in the Archean-Mesoproterozoic ages. Their perceived stability has been challenged over the past decades. Investigations reveal that cratonic lithosphere contains weak layers/zones at various scales and can undergo destabilization, leading to large-scale delamination under specific tectonic perturbations. Mantle plumes represent a key mechanism for such cratonic destruction. The Tarim Craton, amalgamated from Archean crystalline basements in the Neoproterozoic, hosts a Permian large igneous province potentially linked to plume activity, making it a natural laboratory for studying plume-craton interaction. This study systematically compiles geochemical data from Permian magmatic rocks in the Tarim Craton. Focusing on mafic-ultramafic and alkaline rocks with MgO >8 wt%, we employ an experimentally calibrated whole-rock thermobarometer to estimate the pressure-temperature conditions of melt generation, thereby constraining the paleo-lithospheric thickness. Integrating these results with seismic evidence for a mid-lithosphere low-velocity zone (the mid-lithospheric discontinuity, MLD) beneath Tarim, we propose a novel model: By the late Carboniferous, an MLD had developed at ~100 km depth in the craton lithosphere. The initial arrival of a mantle plume at the lithospheric root generated minor kimberlitic and carbonatitic melts. The thick (~200 km) lithosphere initially impeded the plume's ascent until delamination of the root below the MLD occurred. This removal enabled more efficient heating and melting of the upper lithosphere, producing voluminous flood basalts. Subsequent upwelling and melting of the plume itself formed the mafic-ultramafic rocks. Concurrently, interaction between the plume and the metasomatized MLD generated a portion of the alkaline melts. This process induced a local thickening of the MLD to ~130 km, consistent with its present-day depth. Our findings indicate that the mantle plume first thinned and subsequently thickened the cratonic lithosphere, with the MLD playing a crucial role in this evolution. This mechanism of cratonic destruction followed by "healing" may have operated not only in the Paleozoic but also during the Proterozoic, suggesting it could be a vital process for the episodic destabilization of cratons throughout geological time.

How to cite: Pan, Z., Cai, K., and Cheng, Q.: Modifying the Cratonic Lithosphere: The Role of Mantle Plumes Revealed by the Permian Tarim Large Igneous Province, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8766, https://doi.org/10.5194/egusphere-egu26-8766, 2026.

The oxygen fugacity (f_O2) of the mantle governs the behaviors of multivalent elements (e.g., Fe, V) and the speciation of C–O–H fluids, influencing mantle melting, magmatic evolution and volatile distribution across tectonic settings. However, the estimation of mantle f_O2 is limited by challenges in measuring Fe³⁺ in minerals like clinopyroxene (Cpx) due to analytical constraints and inconsistencies between oxybarometer methods. Here, we applied machine learning (ML) to predict Cpx Fe³⁺ content and equilibrium pressure-temperature and f_O2 conditions. We employed a nested cross-validation approach to minimize coincidental perfomance biases. Our models outperformed previous ferric iron and thermobarometer models on both metrics and generalization. The ML-based oxybarometer shows adequate generalization with R² peaking at 0.74, average MAE is 0.95, and average RMSE is 1.45. We compiled an application dataset comprising of 9,832 global mantle xenolith samples. For the subset with Fe³⁺ measurements (n≈600), ML-predicted f_O2 closely matches thermodynamic estimates, supporting the robustness and global applicability of our approach. Applying the model to the rest samples lacking Fe³⁺ analyses expands geographic coverage to data-sparse provinces (e.g., South America, India, and Eastern Europe), and reveals coherent global redox gradients. Xenoliths from cratonic mantle domains show no temporal f_O2 trends since Mesoproterozoic. Comparative analysis across cratonic mantle xenoliths, abyssal peridotites, and oceanic intraplate xenoliths indicates that mantle residues are initially oxidized by short-term metasomatism, but eventually equilibrate to stable redox conditions through interactions with neutral or reducing agents.

How to cite: Ye, C., Liu, C., and Zhang, Z.: Calibrating Mantle Redox Conditions Using Ferric Iron in Clinopyroxene Xenoliths: A Machine Learning Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9001, https://doi.org/10.5194/egusphere-egu26-9001, 2026.

Magmatic activity associated with active transform faults in the Eastern Mediterranean region is widely observed around Toprakkale (Osmaniye), Ceyhan (Adana), and Hatay. This magmatic activity is associated with the Toprakkale Fault (East Anatolian Fault Zone) to the west, the Amanos Segment (East Anatolian Fault Zone) and Yesemek Segment (Dead Sea Fault Zone), which border the Karasu Valley to the east.

Lavas from the western sector (Toprakkale region) are represented by predominantly alkaline mafic compositions, plotted within the basanite and basalt fields in total alkaline-silica (TAS) diagram and displaying SiO₂ and MgO contents of 43.70–48.77 wt% and 5.98–10.46 wt%, respectively. Furthermore, in the eastern sector (Karasu Valley) of the study area, mafic lavas similarly show alkaline affinities and mainly represented by basalts and trachybasalts with SiO₂ and MgO values ranging from 44.89–51.01 wt% and 4.53–9.21 wt% respectively.

Primitive mantle–normalized [1] multi-element patterns of basaltic rocks display LIL element enrichment relative to HFS elements and have broadly OIB-like affinities, but these rocks differ from OIB signature by the depletion in LIL element contents. In contrast, samples from the Karasu Valley are represented by enrichment in LIL and depletion of HFS elements, and are distinct from the OIB signature by enrichment in Cs, Ba, and Pb, along with depletion in Sm, Zr, and Hf. Incompatible element ratios of the mafic lavas show systematic similarities between the western (Toprakkale) and eastern (Karasu Valley) parts of the study area. Ba/La ratios from Toprakkale region range 7.29-9.41 whereas lavas from the Karasu Valley are characterized by higher values that range between 9.76-18.70. Similarly, both sectors are represented by elevated Th/U (3.02–9.16) and consistently high Dy/Yb ratios (>2) [2].

These geochemical features may indicate that the basaltic rocks were derived from a garnet-bearing mantle source. Decompression process appears to be related to the transform fault activities, and the upwelling of the asthenosphere is capable of producing alkaline magmatism within both sectors of the fault zones.

1. Sun, S., McDonough, W.F., 1989. In Magmatism in the Ocean Basins Geological Society London Special Publications, pp. 313–345.

2. Peters, et al., 2008. Lithos, 102(1-2), 295–315.

ACKNOWLEDGEMENTS

This research has been founded by TUBITAK COST project 125Y257

This research is financially supported by TUBITAK 2224-A

How to cite: Önder, D. A., Kurkcuoglu, B., Kahraman, B., Doğan Külahcı, G. D., Yürür, M. T., and Yüce, G.: Source melting and origin of the basaltic rocks situated along the active East Anatolian and Dead Sea Transform Faults, Southeastern Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10459, https://doi.org/10.5194/egusphere-egu26-10459, 2026.

The mantle transition zone (MTZ) is widely considered to be water rich, whereas the upper mantle has a much lower water storage capacity. Materials from the Earth’s surface are transported to the bottom of mantle transition zone and topmost lower mantle by slab subduction, resulting in the global upwelling of the mantle transition zone materials to shallow regions as counterflows. Since minerals in the mantle transition zone are considered to be water-rich, dehydration melting could occur near the 410-km discontinuity when the water-rich materials are transported to the low-water-storage-capacity upper mantle. However, the amount of the melt produced by the dehydration melting process remains poorly constrained. Here, we performed high-pressure phase equilibrium experiments under the conditions just above the mantle transition zone (at 13 GPa and 1800 K) using peridotite + 1 wt.% H₂O, which represents the bulk compositions of a water-rich mantle transition zone. Our results show a very high melt fraction ~ 10 wt.% (equivalent to 10.21 vol.%) produced by the dehydration melting process near the 410-km discontinuity, far exceeding the minimum melt fraction required to significantly reduce seismic velocities. Because of the low density and low viscosity, most melts formed near the 410-km discontinuity should migrate upwards rapidly to shallow regions. They may accumulate near the lithosphere-asthenosphere boundary, causing the rheological weakening of the asthenosphere.

How to cite: Chen, J., Yu, H., Fu, S., Xu, F., Zhang, B., and Fei, H.: The melt fraction induced by the dehydration melting at the base of upper mantle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13795, https://doi.org/10.5194/egusphere-egu26-13795, 2026.

We previously estimated geologically current rates of hotspot motion of 2 to 4 mm/yr from Monte Carlo inversion of the trend of 56 young tracks of hotspots.  Plate motions were constrained to consistency with the MORVEL set of plate relative angular velocities. To determine the average rate of motion, each realization randomly assigns a motion direction to each hotspot and a globally uniform rate of motion is imposed ranging from 0 to 15 mm/yr. We require the misfit for the solution set to lie in a range that is neither too small nor too large given objectively estimated uncertainties of observed hotspot trends. From one million realizations, only 21,749 (≈2%) gave an acceptable fit.

The set of successful solutions also contains information about what directions of hotspot motion produce misfits to the observed trends that are significantly better than those obtained assuming fixed hotspots.  For each hotspot we generate a Rose diagram showing the distribution of the direction of motion for the successful realizations.

We test the directions of motion for each hotspot using the Rayleigh test of uniformity.  Six of the 53 hotspots have a value of p > 0.05, which is not significantly different from a uniform distribution. The other 47 hotspots tend to move perpendicular to the plate-motion direction (p=5.1 × 10^–11 for the Rayleigh test applied to the set of hotspot-motion directions relative to the local plate motion direction).

Exceptions to this pattern occur for hotspots on ultra-slow-moving lithosphere.  Because they are sited on ultra-slow-moving lithosphere, the tracks of these hotspots may record the direction of motion of individual hotspots relative to the mean hotspot reference frame.  Examples of hotspot tracks on the Eurasian, Antarctic, and part of the Nubian plate, all sites of ultra-slow-moving lithosphere, will be examined and discussed.

How to cite: Gordon, R., Gaastra, K., and Mifflin, G.: Geologically Current Directions of Motion of 53 Hotspots Estimated from Monte Carlo Inversion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15215, https://doi.org/10.5194/egusphere-egu26-15215, 2026.

Cratons host diverse metal deposits, including Cu-Ni-PGE deposit systems, and their lithospheric mantle roots have recently been proposed to contain sulfide-hosted metal reservoirs that can provide a potential metal source for ore-forming systems. The base of cratonic mantle lithosphere (cratonic roots) have been suggested to be metasomatized by carbonate-rich magmas episodically over long periods of time. However, whether carbonated cratonic roots are ubiquitously enriched in Platinum-group elements (PGEs) and related metal elements remains debated. The Aillik Bay intrusive suite in Labrador, Canada, preserves magmatic rocks formed by the melting of cratonic roots in two stages: carbonate-poor lamproites in the Mesoproterozoic (~1.37 Ga) and carbonate-rich ultramafic lamprophyres (aillikites) in the Neoproterozoic (~590-555 Ma). These were succeeded by nephelinites during the Early Cretaceous (~142 Ma) by melting at shallower levels after the craton had been split. These samples constitute an ideal natural archive to test the hypothesis of whether carbonated melts drive PGE enrichment in cratonic roots. Here we present a systematic petrographic, whole-rock PGE, and Re-Os isotopic study of these alkaline silicate rocks and associated carbonatites, aiming to evaluate the temporal evolution of PGE budgets within cratonic roots. Rocks from all three periods contain well-preserved magmatic sulfides with negligible alteration, indicating that the observed PGE signatures are controlled by magmatic processes rather than post-emplacement overprinting or secondary alteration. Geochemical constraints further suggest that these magmas were generated under sulfide-saturated (or near-saturated) conditions in their source regions, establishing a basis for assessing sulfide control on PGE behavior. The lamproites formed in reduced, metal-bearing rocks and display MORB-like PGE patterns with depletion of IPGEs and enrichment of PPGEs, with IPGE contents slightly higher than MORBs. In contrast, the aillikites show significant IPGE enrichment, markedly different from MORB patterns. The lamproites and aillikites yield low and primitive mantle-like initial ¹⁸⁷Os/¹⁸⁸Os ratios (0.078 and 0.130), respectively. The Cretaceous nephelinites originated from melting of mantle source metasomatized by aillikite magmas and show MORB-like PGE patterns and initial ¹⁸⁷Os/¹⁸⁸Os ratios typical for metasomatized mantle sources. These observations point to a key control of CO₂ concentrations in magmas on PGE signatures. Therefore, we suggest that carbonatite metasomatism can enrich cratonic roots in IPGE.

How to cite: yu, S., chen, C., Foley, S., Liu, J., He, D., Jiang, W., and Liu, Y.: Carbonatite metasomatism drives PGE enrichment in cratonic roots, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15570, https://doi.org/10.5194/egusphere-egu26-15570, 2026.

Lithospheric thinning in the East Asia exhibits a broad spatial correlation with the stagnant slabs in the mantle transition zone (MTZ), and conceptual models have linked them via mantle upwelling, or plumes, from the MTZ. Because the stagnant slabs present a heat sink rather than a source, such mantle upwellings cannot be thermally driven. They are speculated to be driven by dehydration in the MTZ, but the mechanisms remain to be investigated. Here, we use 2D coupled thermochemical-mechanical modelling to explore the dynamics of the chemically driven mantle upwellings and their tectonomagmatic interactions with the overriding plate. We found that the chemically driven mantle upwellings in the upper mantle are generally narrower, faster, and can be stronger than thermally driven mantle upwellings. The chemically driven mantle upwellings can advect heat to the base of the overriding plate to cause thermal erosion and partial melting. Their roles are limited and unlikely to be the major cause of mantle lithospheric thinning in East Asia, but they provide a compelling mechanism for the widespread Cenozoic basaltic magmatism.

How to cite: Gou, Y. and Liu, M.: Mantle Upwellings Induced by the Stagnant Slabs in the Mantle Transition Zone: A Numerical Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15762, https://doi.org/10.5194/egusphere-egu26-15762, 2026.

A recent expedition aboard R/V Nathaniel B. Palmer (NBP25-01, 2025) sampled submarine seamounts across six regions of the Terror Rift, western Ross Sea, Antarctica. Volcanism in this area is dominated by explosive mafic alkaline magmas forming monogenetic and polygenetic seamounts (Tominaga et al., 2025). Of the 50 dredges collected, nearly half recovered mantle xenoliths, offering a rare opportunity to constrain the composition, thermal structure and evolution of the mantle beneath an active Antarctic rift.

The xenolith suite is dominated by peridotites (dunite to lherzolite), with subordinate pyroxenite and hornblendite. We present mineral chemistry and thermobarometric data from these lithologies to constrain their P-T-fluid history, and potential spatial heterogeneities.

Preliminary results from peridotite xenoliths sampled at Squid Ridge, a seamount located close to the rift axis, reveal evidence for two distinct melt–peridotite interaction events. The first event occurred at high temperature and is marked by the formation of interstitial diopside and Cr-rich spinel. Melt percolation was coeval with viscous deformation, recorded by olivine subgrain development and dynamic recrystallization of orthopyroxene when present. Pyroxene thermobarometry yields equilibrium conditions of 1065 ± 5 °C and 1.0 ± 0.2 GPa, corresponding to depths of ~30 km. The second event is characterized by brittle fracturing of the peridotites and the formation of alkali-rich glass, amphibole, augite and Mg-poor olivine in fractures. It is interpreted to reflect xenolith entrainment during magma ascent.

These results indicate a deep lithospheric mantle origin for the studied xenoliths, consistent with previous estimates from Franklin Island peridotite xenoliths located farther from the rift axis (Martin et al., 2023). Together, these observations suggest that rift-related fault systems efficiently channel deep-sourced melts to the surface and support the presence of a relatively cold geotherm beneath the Terror Rift, consistent with an idealized dynamic rift.

Martin et al. (2023). A review of mantle xenoliths in volcanic rocks from southern Victoria Land, Antarctica.

Tominaga, M. et al. (2025). Subglacial explosive volcanism in the Ross Sea of Antarctica. Communications Earth & Environment, 6(1), 921.

How to cite: Prigent, C., Walter, M., Panter, K. S., Berthod, C., Tominaga, M., and Cross, A.: Preliminary results on the composition of the Antarctic mantle below the Terror Rift, Western Ross Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17162, https://doi.org/10.5194/egusphere-egu26-17162, 2026.

It remains a persistent point of contention among igneous petrologists as to how alkaline magmas generated by small degrees of melting within the upper-most convecting mantle can traverse through relatively cool continental lithosphere without freezing and being trapped at depth. Melting experiments demonstrate that volatile-rich, silica-undersaturated liquid react with peridotite under P-T conditions equivalent to the base of lithosphere and can form hydrous cumulates consisting of clinopyroxene, amphibole and phlogopite^1-3. Furthermore, this metasomatic process enriches the mantle in incompatible elements in amounts similar to basalt (i.e. nephelinite, basanite) and may be a melt source for alkaline lavas⁴. The experiments and theoretical models provide important clues as to the cause and source of alkaline volcanism that occur within plates but demand evidence from natural settings. Here we present major and trace elements and ⁴⁰Ar/³⁹Ar ages from Pliocene-Pleistocene, olivine-phyric alkaline basalt erupted through extended continental lithosphere within and bordering the Terror Rift, southwestern Ross Sea, Antarctica. Subaerial and submarine basaltic tephra and lava from this region contain mantle xenoliths that include hydrous-phases that also display melt-solid reaction textures^5,6. We compare basalt erupted across the central portion of the rift with basalt erupted at the rift shoulder along the base of the Transantarctic Mountains^7,8. Our comparison shows that silica-undersaturation (i.e. nepheline-normative content) and highly incompatible trace element concentrations decrease with decreasing degree east longitude within the rift and on average are at their lowest on the rift shoulder. Variable degrees of partial melting of a common mantle source are modelled to match the trace element trends but require an unrealistic range of values: F = <3% beneath rift and as much as 15% beneath the rift shoulder. The models are also not consistent given the greater depth to the lithosphere-asthenosphere boundary (LAB) beneath the rift shoulder (>95 km) relative to the central rift (<85 km)⁹. We propose that the compositional variability may be explained by interaction-reaction of asthenospheric melt with mantle lithosphere manifest to a greater degree beneath the rift shoulder. But also, that that portions of the continental lithosphere that have been metasomatized by low-degree, volatile-rich, silica-undersaturated melt, evident in mantle xenoliths hosted by the basalt, are likely to be a contributing source for alkaline volcanism in this region.   

¹Foley 1992, Lithos 28; ²Pilet et al., 2008, Science 320; ³Pilet et al., 2010, Contrib. Mineral. Petrol. 159; ⁴Pilet et al., 2011, Jour. Petrol. 52; ⁵Martin et al., 2021, Geol. Soc. Lond. Mem. 55; ⁶Panter et al., 2025, AGU Fall Meet. Abst. 2025, OS51F-0475; ⁷Tominaga et al., 2025, Comm. Earth Environ. 6:921; ⁸Panter et al., unpubl.; ⁹An et al., 2015, Jour. Geophys. Res. 120:12.

How to cite: Panter, K., O'Conke, R., Tominaga, M., Prigent, C., Berthod, C., Pilet, S., and Konrad, K.: Lithosphere-melt interactions, evidence from basalt and xenolith cargo, Terror Rift, Ross Sea, Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21679, https://doi.org/10.5194/egusphere-egu26-21679, 2026.

Ilmenite is found in lithospheric mantle rocks ranges from 1.5% (Udachnaya pipe, center of Siberian craton, Yakutian kimberlite province) to 4-7% (Obnazhennaya pipe, northeastern margin of the craton). In the Mir and Obnazhennaya pipes, this mineral occurs as small, rounded and elongated inclusions (up to 20-50 μm in size) in garnet and clinopyroxene, also needles, and lamellae (up to 20-40 μm thick), following the crystallographic orientation of the host mineral. These are presumably exsolution structures. Lamellas show a wide range of chemical composition, from 39.7 to 57.6 wt.% TiO₂ and 4.2-12.5 wt.% MgO. Large variations in the compositions of ilmenite lamellas from pyroxene and garnet crystals suggest that these ilmenites formed as exsolution structures during the gradual cooling of initial pigeonite megacrystals. Ilmenite from mantle rocks forms relatively large (0.3–2 mm) isometric grains with thin elongations parallel to the banding, and lenticular porphyroclasts with features of mosaic polygonality, indicating the initial stage of rock deformation. Ilmenite from kimberlite xenoliths in the central Siberian Craton occurs in polymictic breccias and exsolution structures in other minerals and is predominantly of cumulative origin. Ilmenite from mantle xenoliths from northeast of Yakutia has a variety of morphologies, which allows us to distinguish several generations and indicates a multi-stage genesis.

The rates of their cooling and the P-T of final crystallization were different, which is reflected in the difference in ilmenite compositions. Diffusion of elements from the host mineral could also affect compositional variations, since the sizes of small inclusions are up to 20-40 μm. Moreover, some of the compositions of ilmenite lamellas from Mir pipe xenoliths are close to the compositions of late fine-grained ilmenites of the bulk of kimberlites. Polymictic peridotite rocks with Phl-Ilm cement and accessory rutile and zircon, termed polymictic breccias, were described in the Udachnaya pipe. It is assumed that Phl-Ilm and Ilm parageneses crystallized in equilibrium with residual asthenospheric melts remaining after the crystallization of most of the megacrysts of the low-chromium association and the formation of deformed garnet peridotites, and are of cumulative origin. Residual magmatic liquids are enriched in potassium, titanium, iron and volatiles. Moreover, the age of phlogopite deformation coincides with the age of the kimberlite pipes formation - 367.1 ± 1.4 Ma.

In addition, large (up to 100-200 μm) rounded inclusions of ilmenite in garnet and pyroxene, intergrowths of ilmenite with garnet - such samples were not found in our collection of xenoliths from the central parts of the craton. Ilmenite also forms individual isomorphic crystals (often intergrown with isomorphic phlogopite plates). Rounded inclusions from the Obnazhennaya pipe are distinguished by narrow compositional variations - 49.9-52.5 wt.% TiO2 and are close to the compositions of mantle, asthenospheric ilmenites. Presumably, they formed as a result of the influence of alkaline basaltic melts enriched in iron and titanium (FeO - up to 12-15 wt.%; TiO2 - up to 5-9 wt.%). The formation of several generations of ilmenite and phlogopite, zoning of associated minerals, suggests that the impact of such melt-fluids was repeated.

How to cite: Kalashnikova, T., Vorobiev, S., Kostrovitsky, S., and Aktinova, E.: Ilmenite from lithospheric mantle beneath Siberian craton - the formation ways , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22230, https://doi.org/10.5194/egusphere-egu26-22230, 2026.

Mantle/melt partitioning of trace elements is governed by both melt composition and the chemistry of peridotite-forming minerals (olivine, orthopyroxene, clinopyroxene and garnet/spinel), which in turn are controlled by the pressure-temperature conditions in the melting column. Although several sets of mineral/melt partition coefficients are available for various mantle lithologies and P-T conditions, none constrains the partitioning behavior for realistic CO₂-H₂O-bearing silicate melts saturated with the four mantle minerals along the mantle adiabat, conditions that will determine the geochemical signatures of melts released from asthenosphere upwellings. To thus performed “forced multiple saturation experiments” on a highly Si-undersaturated primitive ocean island basanite composition from Cape Verde in which the melt is forced into equilibrium with four-phase garnet lherzolite at adiabatic temperatures (1380-1420 ^oC) at 3-7 GPa. This yields mineral and melt compositions in the melting column of a mantle upwelling from the incipient redox melts forming at 7 GPa to the oceanic lithosphere-asthenosphere boundary (LAB). In-situ analyses by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were conducted to determine the mineral/melt partitioning of high field strength elements (HFSE: Nb, Ta, Zr, Hf), Ba, Sr, Th, U, REEs, Y, moderately siderophile elements (e.g., W, Mo), alkalis (K₂O, Na₂O) and other minor elements (TiO₂, P₂O₅) at each pressure step. These pressure-dependent partition coefficients and our melting reaction stoichiometries are then employed to model the geochemical signatures of CO₂-bearing silicate melt rising through the asthenosphere. The modeled results are then compared to primitive alkaline magmas erupted in both continental and oceanic settings to test whether peridotite/melt trace element partitioning to varying depths effectively encompasses the geochemical spectrum of intraplate magmatism.

How to cite: Schettino, E. and Schmidt, M. W.: Peridotite/melt partitioning experiments constraining the geochemical signature of CO2-bearing alkaline magmas from redox melting to the source of ocean island basalts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22348, https://doi.org/10.5194/egusphere-egu26-22348, 2026.

Dichotomous thinking also known as “black-and-white” and “all-or-nothing” thinking is a common cognitive distortion in which one sees things in absolute extremes without any middle ground. Not only does this bias distort reality and lead to interpersonal conflicts, but it also hinders problem solving. In the Geosciences, this bias is the source of a > 100 years old divide between tectonicists, i.e., early supporters of Continental Drift Theory (e.g., Alfred Wegener, Alexander du Toit), and paleontologists, who argued for (now sunken) land bridges between the continents based on similar fossil records (e.g., Charles Schuchert, John Gregory, Hermann von Ihering, Bailey Willis). Despite explaining the similar fossil record on continents now separated by oceans, Land Bridge Theory implied continental fixity. It was therefore completely abandoned in the 60–70s with the growing body of evidence supporting continent motion. Continental Drift Theory was then fully accepted without any middle ground despite the fossil record suggesting prolonged connection between the continents at specific localities. Possible causes for the black-or-white approach of the Geoscience community include (1) simplicity: easier to envision one hypothesis being right rather than a compromise of both, (2) guilt: Alfred Wegener had died in Greenland in 1931 only to be proven right 30 years later upon acceptance of continent motion, and (3) a feeling of inferiority amongst paleontologists and feeling of superiority (i.e., feeling of inferiority in disguise) amongst tectonicists upon demonstrating continental motion.

Since then, paleontologists have explored new hypotheses to explain the migration of species at times when oceans are believed to have fully separated the continents, e.g., migration of primates from western Africa to South America and of lizards the other way around in the Oligocene. A hypothesis under testing involves floating vegetation islands rafting the species as small groups of individuals across the ocean. This hypothesis implies that enough individuals survived the crossing, i.e., enough food and/or quick journey, and found one another upon landing.

Neither the new hypotheses nor the old ones take into account all the evidence, e.g., microcontinents along major transform faults (e.g., Romanche and St Paul fault zones) and correlation of all former land bridges with major transform faults and rift-oblique orogens on the adjacent margins (e.g., Central African Orogen in western Africa and Sergipano Belt in northeastern Brazil). Orogenic Bridge Theory reconciles these with both continent motion and the fossil record. Orogenic bridges are ribbons of continental crust transected by orogenic structures highly oblique to the active rift. These structures are unsuitably oriented to thin the crust and thus hinder rifting, delay breakup, and control the formation of major transform faults and elongated microcontinents. Orogenic bridges have the potential to form prolonged land connections between the continents while oceanic crustal domains form on either side, thus further allowing the spreading of terrestrial species while hindering that of marine species. This illustrates the need for more multidisciplinary collaboration across the geosciences. Creating a more flexible community that is both inclusive and mindful of diversity is key to enhance collaboration.

How to cite: Koehl, J.-B. and Foulger, G.: Black and white: the bias that shaped plate tectonics and the ongoing > 100 years old divide of the geoscience community, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-507, https://doi.org/10.5194/egusphere-egu26-507, 2026.

Marine biodiversity hotspots are regions characterized by exceptionally high species richness compared to surrounding areas. Fossil and molecular evidence indicate that these hotspots have shifted across space and time throughout the Cenozoic; yet the mechanisms driving their emergence and relocation remain inadequately understood. Here, we examine these dynamics—and their links to environmental change—using genus-level fossil data for molluscs, cnidarians, and foraminifera compiled from the Paleobiology Database and published sources.

Because publicly available fossil occurrence data exhibit strong geographic and temporal sampling inhomogeneities, sampling standardization is essential for robust interpretation of diversity patterns. To reduce sampling biases, we applied Shareholder Quorum Subsampling (SQS) and identified paleo-hotspots as regions where sampling-standardized richness exceeded global confidence intervals. We detected 40 paleo-hotspots exhibiting distinct clade-specific macro-evolutionary signatures. Using models based on Hierarchical Bayesian structural equations reveal that environmental conditions (sea surface temperature, shelf area, sea level) influence hotspot development formation predominantly by modulating macro-evolutionary processes (origination, extinction, immigration), though the strength and direction of these pathways differ among groups. Cnidarian hotspots arise from high evolutionary turnover, where elevated origination rates and expansive shelf area strongly increase hotspot probability. In contrast, for both benthic and planktic foraminifera, no single environmental or macro-evolutionary factor exerts a dominant direct influence; rather, interconnected processes indirectly shape diversity and, ultimately, hotspot formation. Together, these results show that marine biodiversity hotspots arise through distinct, clade-specific macro-evolutionary mechanisms influenced by the environment.

How to cite: Kella, V. G. and Chattopadhyay, D.: Interacting environmental and evolutionary controls on shifting marine biodiversity hotspots through Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1165, https://doi.org/10.5194/egusphere-egu26-1165, 2026.

Large Igneous Province (LIP) volcanism is commonly considered to have driven ocean deoxygenation and associated mass extinctions during the Phanerozoic. However, the impacts and feedback mechanisms associated with LIP emplacement in the prevailingly low-oxygen Precambrian environment remain poorly understood. Here, we present mercury isotope, iron speciation and phosphorus phase partitioning data for mid-Mesoproterozoic marine sediments of the Shennongjia Group, South China, to reconstruct the response of the phosphorus cycle to LIP volcanism. Our data indicate that LIP volcanism triggered an expansion in marine euxinia, which enhanced phosphorus recycling and stimulated surface ocean primary production, thereby promoting increased burial of organic carbon and pyrite. This facilitated net marine oxygenation, with repeated volcanic pulses ultimately resulting in enhanced ventilation of the mid-Proterozoic ocean. We propose that while mid-Proterozoic LIP volcanism may have caused short-term ecological crises, the ensuing redox-nutrient feedbacks ultimately stimulated progressive oxygenation of Earth’s surface environment.

How to cite: Sun, L., Sonke, J. E., Poulton, S. W., Tang*, D., Shi, X., Wang, X., Zhou, X., Meng, L., Xie, B., Xu, L., Yang, S., and Guilbaud, R.: Volcanic forcing of oxygenation dynamics in the mid-Proterozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1434, https://doi.org/10.5194/egusphere-egu26-1434, 2026.

Accurately distinguishing between biotic and abiotic microstructures is crucial for understanding the evolution of early life and the search for extraterrestrial life. The oldest putative fossils reported occur in the form of hematite filaments and tubes in the jasper-carbonate BIF from the Nuvvuagittuq Supracrustal Belt (NSB), Québec, possibly as old as 4.3 Ga. Although these twisted and branched hematite filaments and tubes are very similar to the Fe-oxyhydroxide filaments produced by Fe-oxidizing bacteria in modern hydrothermal deposits, they are still being questioned because morphologically and compositionally similar abiotic filamentous biomorphs can be produced in “chemical gardens”. Additionally, the origin of ubiquitous circularly concentric rosettes that occur with the filaments and tubes remains unclear. Systematic mineralogical and morphological characterization of these microstructures using a variety of correlated in-situ micro-analytical techniques such as polarizing microscopy, Raman spectroscopy, SEM-EDS, and XPS now yield a new understanding of these ancient microscopic objects.

Firstly, new observations of hematite filaments and tubes preserved in apatite crystals indicate phosphatization as another taphonomic mode of preservation. These apatites with filaments that are several hundred micrometers in size, and usually distributed in discontinuous bands between the silicon-rich and iron-rich microbands. The diameter of these hematite filaments and tubes is 4 to 8 μm, while their lengths are 10 to 200 μm. They are thinner than those previously reported preserved in quartz and their diameter is closer to that of modern iron-oxidizing bacteria. As for co-occurring hematite tubes, their interior is usually filled with apatite. The walls of tubes are often straight, and even crossing crystal boundaries between apatite and microcrystalline quartz. Furthermore, new Raman spectra show the occasional presence of organic matter in these filaments preserved in apatite, independently supporting a biological origin.

Secondly, rosettes widely present in the quartz have circularly concentric layers, radially geometric crystals of acicular hematite, and circular double or triple twins. These microstructures are akin to patterns seen in botryoidal minerals and likely produced by abiotic chemically oscillating reactions (COR). In addition, the walls of the tubes preserved in quartz are also sometimes wavy, curved, or botryoidal-like, along with concentric layers, which is comparable to botryoidal coatings on modern hollow filaments of ferrihydrite in deep-sea hydrothermal ecosystems, indicating the interaction between iron-containing minerals and decaying organic matter from biomass during diagenesis.

The latest observations suggest that in the early Earth's submarine hydrothermal environments rich in phosphate and organic acids, the widespread phosphatisation enables the oldest life preserved in the apatite in the form of hematite filaments and tubes. The new observations also emphasize the potential role of abiotic COR in the formation of rosettes, as well as the modifications of the surface features of microfossils during diagenesis. These biological and abiotic “biosignatures” provide a valuable reference to search for life signals in extraterrestrial environments such as Mars and icy moons.

How to cite: Ge, Y., Papineau, D., Guo, Z., She, Z., O'Neil, J., and Garçon, M.: Widespread chemically oscillating reactions and the phosphatization of hematite filaments and tubes in the oldest BIF from the Nuvvuagittuq Supracrustal Belt , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1919, https://doi.org/10.5194/egusphere-egu26-1919, 2026.

The concept of a warm, sluggish ocean recurs in the palaeoceanographic literature, yet over the last few years, both observation and model studies have challenged this concept repeatedly. Nevertheless, observations in the modern do link the ongoing anthropogenic warming to the slowing down of oceanic circulation. This mismatch between the different scales of observations presents a critical problem to our understanding of the past ocean. Here, we present a critical evaluation of this concept through an extensive series of intermediate complexity Earth system model experiments. Multiple paleogeographic scenarios across the Phanerozoic, CO2 concentration, and orbital configuration have been simulated to evaluate the relations between planetary surface temperatures and deep-water rejuvenation rate. Combined, the results of these simulations present a very limited contribution of warm climates to the global ocean circulation slowdown. For most experiments, warmer conditions enhanced overall oceanic turnover due to an increase in vertical density gradient, supporting more efficient downwelling. However, this state is only achieved in the long term, with some slowdown after the initial warming. The overall range of turnover time, even during the slowest period of deep-water rejuvenation, remains within the same order of magnitude as the modern. In light of these findings, it is unlikely that at any point through the Phanerozoic did oceanic turnover rate changed in a magnitude that would impact the mixing state of most marine dissolved chemical elements, at least at current flux state.

How to cite: Bialik, O. M., Sarr, A.-C., Donnadieu, Y., and Pohl, A.: Phanerozoic trends in deep water rejuvenation: Is there a relation between global temperature and ocean mixing? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2111, https://doi.org/10.5194/egusphere-egu26-2111, 2026.

Environmental variables like temperature, land availability and food availability constrain the ecological niches of terrestrial animals and, along with atmospheric oxygen levels, likely had a direct effect on their evolution and distribution over geological time. In this study we develop an agent-based terrestrial palaeoecological model, which we couple to an Earth system model to reconstruct how Earth’s habitability for terrestrial mammals has changed over the Mesozoic to Cenozoic eras. This allows us to investigate whether there was an environmental component to the early Cenozoic mammal radiation. Our findings indicate that Earth’s habitability for terrestrial mammals was maximised during the Cretaceous–Paleogene interval, due to the combination of elevated plant Net Primary Productivity (NPP), expansion of continental land areas, minimal glaciation, and elevated atmospheric oxygen levels. We propose that the rapid diversification of mammals during this period, while clearly enabled by the extinction of non-avian dinosaurs, was also influenced by the enhanced habitability of Earth’s surface during this time. Similar environmentally-driven changes in terrestrial habitability likely also play a significant role for other palaeobiological events.

How to cite: Hadjigavriel, N.: Early Cenozoic mammal radiation coincides with increased terrestrial habitability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3338, https://doi.org/10.5194/egusphere-egu26-3338, 2026.

Long-term sustainability of human civilization depends on secure supplies of metals and critical minerals that underpin energy systems, infrastructure, and technology (IEA, 2021; UNEP, 2024). By 2040, total mineral demand from clean energy technologies is expected to double or quadruple (IEA, 2021), raising concerns about long-term supply sustainability as anthropogenic extraction operates on timescales and magnitudes unconstrained by geological ore-forming rates. Although recycling and substitution can mitigate pressure, widely adopted outlooks still require substantial expansion of primary supply and are commonly framed around reserves, production, and announced project pipelines (IEA, 2024; USGS, 2025).

We present a plate-kinematic framework to forecast ore deposit formation over the next 10 Myr by coupling tectonic setting–specific deposit-generation functions to a forward plate-motion model. Unlike reserve- or discovery-trend extrapolations, this approach explicitly links plate tectonics to mineralization rates, providing a first-order estimate of Earth’s natural “mineral renewal” capacity (IEA, 2024; USGS, 2025). We apply the method to two deposit types: (1) porphyry–epithermal systems in continental arcs, parameterized by plate convergence rates and lithospheric factors (crustal thickness, slab composition, and proxies for slab oxidation state), reflecting how rapid convergence and thick crust favor porphyry formation, while explicitly accounting for melt–fluid–driven mass transfer of copper and oxidized species within subduction zones; and (2) mid-ocean ridge seafloor massive sulfides (SMS), linked to spreading rate, ridge depth, and detachment fault occurrence at slow-spreading centers. These parameterizations are integrated into a global 1°-resolution plate model extrapolated 10 Myr into the future to produce spatially explicit, time-dependent maps of ore-forming potential. Because most new oceanic crust is not subducted within a 10 Myr horizon, our model estimates gross SMS formation within a limited accessibility window (controlled by sediment burial), while acknowledging subduction recycling as a longer-term sink.

The resulting formation- and accessibility-weighted metrics provide benchmarks for Earth’s natural mineral replenishment rate, against which scenario-based demand projections can be compared, thereby strengthening sustainability discussions with geodynamically grounded constraints.

References:

International Energy Agency (IEA): The Role of Critical Minerals in Clean Energy Transitions, IEA, Paris, 2021.

International Energy Agency (IEA): Global Critical Minerals Outlook 2024, IEA, Paris, 2024.

United Nations Environment Programme (UNEP) and International Resource Panel (IRP): Global Resources Outlook 2024 – Bend the trend: Pathways to a Liveable Planet as Resource Use Spikes, UNEP, 2024, doi:20.500.11822/44901.

U.S. Geological Survey (USGS): Mineral Commodity Summaries 2025 (ver. 1.2, March 2025), U.S. Geological Survey, 212 pp., doi:10.3133/mcs2025, 2025.

How to cite: Ciazela, J., Gerya, T., Verard, C., Stern, R., Leybourne, M., and Duan, W.: A Plate-Tectonic Framework for Predicting Ore Deposit Formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4337, https://doi.org/10.5194/egusphere-egu26-4337, 2026.

Emerging geochemical evidence suggests highly heterogeneous ocean redox conditions in the mid-Proterozoic. Quantitative estimates of the extent of different modes of anoxia, however, remain poorly constrained. Considering the complementary redox-related behaviour, uranium and molybdenum isotopes can be combined to reconstruct ancient marine redox landscapes, which has not been applied to the mid-Proterozoic. In this study, we present new δ²³⁸U and δ⁹⁸Mo data for shales from the ~1.4 Ga Xiamaling Formation, North China Craton, together with independent redox proxies, including Fe speciation and redox-sensitive trace metals. We find that most oxic and dysoxic samples retain low U and Mo concentrations, with δ²³⁸U and δ⁹⁸Mo values indistinguishable from continental crust. While euxinic samples record the highest authigenic δ²³⁸U and δ⁹⁸Mo, consistent with efficient reduction of U and Mo. Samples deposited under ferruginous conditions exhibit a wider range of δ²³⁸U and δ⁹⁸Mo values that generally fall between the (dys)oxic and euxinic end-members. Using a coupled U-Mo isotope mass balance model, we infer limited euxinia but extensive low productivity, ferruginous conditions in mid-Proterozoic oceans.

How to cite: Song, Y., Mills, B., Bowyer, F., Andersen, M., Ossa Ossa, F., Dickson, A., Harvey, J., Zhang, S., Wang, X., Wang, H., Canfield, D., Shield, G., and Poulton, S.: Tracking the spatial extent of redox variability in the mid-Proterozoic ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5361, https://doi.org/10.5194/egusphere-egu26-5361, 2026.

Prevailing interpretations of large underground cavities in carbonate terrains are predominantly based on karst-related genetic models, in which dissolution-driven hydrological processes are assumed to be the primary mechanism of formation. While effective for explaining certain cave types, these models commonly rely on an implicit assumption: that underground cavities should be analyzed as isolated natural features. This assumption has limited the recognition of broader spatial patterns and system-level organization.

This study proposes a geoarchaeological, system-based approach to the interpretation of underground spaces, using the Zagros Mountains as a key case study. Given the extensive carbonate lithology of the region, classical karst theory would predict cave development closely associated with active or fossil drainage networks. However, field observations reveal a contrasting pattern, with numerous underground openings located at elevated positions, often on cliff faces or near ridgelines, lacking any evidence of hydrological concentration or outlet channels.

A focal example is provided by the Deh Sheikh area (central Zagros), where multiple underground entrances occur at the same elevation level and are separated by relatively regular horizontal distances. Such repeated and level-aligned configurations are difficult to reconcile with stochastic karstic dissolution processes and instead suggest a coherent spatial logic that becomes visible only when these features are considered collectively rather than individually.

Additional evidence includes stable arched geometries and persistent cavities that contrast with the irregular, downward-oriented erosion expected from water-dominated processes. These observations indicate that natural processes observed today are largely secondary modifications, overprinting earlier phases of space formation.

Rather than rejecting natural cave formation mechanisms, this study argues that, in the Zagros region, a system-based geoarchaeological framework provides a more coherent and parsimonious interpretive model. The results highlight the importance of analytical scale and interdisciplinary perspectives in re-evaluating underground spaces.

How to cite: Baghbani, F. and Baghbani, H.: From Isolated Caves to Spatial Systems: A Geoarchaeological Re-reading of Underground Spaces in the Zagros Mountains, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5975, https://doi.org/10.5194/egusphere-egu26-5975, 2026.

The degree to which Earth’s climate retained seasonality and ocean-atmospheric coupling during the two Cryogenian snowball Earth glaciations, the Sturtian (~717-658 Ma) and Marinoan (~654-635 Ma), is unknown. The classic hypothesis envisions ice at equatorial latitudes with a largely quiescent hydrological cycle. However, other observations imply the persistence of open water in the tropics, permitting ocean-atmospheric coupling and reconciling photosynthetic survival with low-latitude glacial activity. Consequently, open questions remain as to whether internal climate cycles could operate during snowball Earth, and if so, what their expression reveals about the extent of open ocean and the dynamics of the Cryogenian climate system; important climate questions that carry key biological implications. Varve-like laminites provide high resolution records of climatic variability as far back as the Proterozoic. However, varved sediments that retain climatic information are rare in the Cryogenian. Here, we analyse field data from rhythmic laminites from the Port Askaig Formation (Scotland). Petrographic and spectral analysis indicates that the laminites represent glacio-lacustrine annual varves, which reveal statistically significant centennial to interannual periodicities strongly similar to solar phenomena and modern ocean-atmospheric climate patterns. We interpret these signals with fully coupled Cryogenian climate simulations using the Community Earth System Model (CESM) under varying degrees of ice coverage to reconstruct climate variability during this interval of the Sturtian glaciation. These simulations suggest that open water is present to some degree in the tropics. Our study reveals a wider range of climatic variability than previously envisaged under snowball Earth conditions, and hints at the possibility of unfrozen tropical waters during this discrete interval of the Sturtian glaciation, or yet unexplored mechanisms of interannual variability on icy worlds.

How to cite: Griffin, C., Gernon, T., Fu, M., Rugen, E., Spencer, A., Warrington, G., and Hincks, T.: Distinguishing Snowball Earth climate modes using field data and climate simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6597, https://doi.org/10.5194/egusphere-egu26-6597, 2026.

The shift from the climate of the “boring billion” without evidence for major glaciations to the globally ice-covered “Snowball Earth” events of the Cryogenian (720–635 million years ago, Ma) remains enigmatic. Various factors have been suggested to drive the cooling in the early Neoproterozoic (1000–539 Ma), most prominently decreasing carbon-dioxide levels due to enhanced weathering of tropical continents or fresh volcanic material. However, these processes should have operated during the boring billion as well, triggering the quest for alternative explanations. It has been suggested, for example, that the increase in both the diversity and the biomass of eukaryotic algae around 800 Ma could have contributed to the cooling via the emission of dimethyl sulfide (DMS), a source of cloud condensation nuclei instrumental in forming bright clouds over dark ocean surfaces. Here, we investigate this hypothesis with a coupled climate–ocean biogeochemistry model, allowing for the first time the quantification of the relevant marine carbon cycle feedbacks. We confirm that the increase in cloud condensation nuclei cools the Neoproterozoic climate and can lead to global glaciation at low atmospheric carbon-dioxide concentrations. Our analysis sheds light on the positive and negative feedback loops associated with the rise of algae and demonstrates that changes in cloud cover remain a plausible contribution to Neoproterozoic cooling.

How to cite: Feulner, G., Hofmann, M., Eberhard, J., and Petri, S.: Ocean biogeochemistry amplifies cooling caused by increase in cloud condensation nuclei from algae prior to Cryogenian Snowball Earth events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6828, https://doi.org/10.5194/egusphere-egu26-6828, 2026.

The African continent has undergone major Cenozoic transformations, including the formation of the East African Rift System and the opening of the Red Sea and the Gulf of Aden. The impact of these transformations on the various components of the Earth system over time—climate, hydrographic networks, and the dispersal and evolution of biological species—raises multiple questions.

In this context, we aim to reconstruct the paleogeographic evolution of continental Africa over the past 30 million years using a multi-layered modelling approach. First, the integration of several geodynamic components (including mantle-driven dynamic topography, the history of crustal tectonics, plate tectonic motions, and volcanic eruptive dynamics) allows us to produce an elevation model for Africa since 30 Ma that is continuous in space and time. This elevation model is then used as a boundary condition for climate simulations, followed by physiographic simulations, generating a more comprehensive and coherent representation of past environments.

The simulation outputs reveal the sensitivity of climate reconstructions to topographic boundary conditions, as well as temporal variations in hydrographic networks. These new topographic, climatic, and physiographic constraints provide improved calibration for future eco-evolutionary studies (e.g., geographic barriers, water availability, resource distribution, and environmental stability) on the African continent.

We then evaluate the spatial and temporal accuracy of these reconstructions by confronting them with field-based evidence. This assessment identifies the scales at which the models are most robust, informing which interrogation can be explored with confidence. It also highlights where the reconstructions are consistent with geological, paleoenvironmental, and paleontological data, and where their precision may require further refinement.

Looking ahead, the objective is to continuously update these maps and simulations, which will also be used to investigate the dispersal and evolutionary changes of Cenozoic faunal communities in Africa, notably early hominids. This whole study offers a coherent spatio-temporal context for evaluating links between the different components of the Earthsystem.

How to cite: Tournier, R., Husson, L., Prat, S., Boisserie, J.-R., Barboni, D., Bellahsen, N., Doubre, C., Pik, R., Salles, T., Sepulchre, P., and Tiberi, C.: African paleogeography since 30Ma : setting boundary conditions for climatic, physiographic and biodiversity models., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7017, https://doi.org/10.5194/egusphere-egu26-7017, 2026.

Paleogeographic reconstructions of the deep past are affected by large uncertainties due to limitations in dating, the scarcity of sedimentary sequences, and imperfect constraints on the positions of tectonic plates. These uncertainties in the boundary conditions propagate into climate simulations, affecting their accuracy.

In this study, we compare two paleogeographic reconstructions, Panalesis [1] and PaleoMap [2], to assess how differences in the paleogeographic reconstructions influence the climate response at the Permian-Triassic Boundary. Climate simulations are performed using biogeodyn-MITgcmIS [3], a recently developed modelling tool in which the dynamical core of both the atmosphere and the ocean is provided by the MIT general circulation model, while offline coupling ensures the consistent evolution of vegetation and ice sheets (when present).

Beyond the direct comparison of paleogeographic reconstructions, aquaplanet and simplified configurations are employed under the same paleoclimate conditions to isolate feedbacks arising from land distribution. The resulting steady-state climates are systematically compared with those obtained using Pangea configurations derived from Panalesis and PaleoMap. The impact on terrestrial vegetation is also estimated and discussed. Overall, the results provide a framework for systematically assessing how paleogeographic reconstructions affect coupled climate-biosphere dynamics.

References

[1] Vérard, Geological Magazine 156, 320 (2019)

[2] Scotese, Atlas of Earth History, PALEOMAP Project (2001)

[3] Moinat et al., EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-2946 (2025).

How to cite: Kang, B., Moinat, L., Ragon, C., Vérard, C., and Brunetti, M.: How palaeogeographic reconstructions influence climate: the Permian-Triassic Boundary case study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7068, https://doi.org/10.5194/egusphere-egu26-7068, 2026.

The Lomagundi-Jatuli event (2.3-2.0 Ga) is one of the grandest carbon isotopic (δ¹³C_carbonate) excursion events in the Earth’s history, marked by anomalous δ¹³C_carbonate reaching up to + 30 ‰. Several hypotheses have been proposed to explain this excursion; however, they remain inadequate due to associated drawbacks. The conventional explanation is organic carbon burial due to enhanced productivity. But, the lack of organic rich stratas synchronous with the excursion demands the reconsideration of alternative biogeochemical processes to explain this isotopic anomaly. Moreover, the excursion is observed only in the evaporitic and nearshore carbonates, with no evidence from open ocean; demanding facies based biogeochemical explanation. Here, we explore the possibility of CO₂ outgassing and calcite precipitation as potential drivers responsible for this excursion as these two processes remain the least explored among the proposed hypotheses. Through sedimentological evidences from previous studies and Rayleigh fractionation calculations, we argue that dominant loss of DIC through CO₂ outgassing in the evaporitic facies and calcite precipitation in the nearshore facies along with a well-mixed DIC reservoir in the open ocean led to observed Lomagundi Excursion.

How to cite: Janaarthanan, P. A. and Kumar, S.: Can CO2 outgassing explain Lomagundi Excursion?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7342, https://doi.org/10.5194/egusphere-egu26-7342, 2026.

Plate tectonic reconstructions are different from palæogeographic reconstructions. The latter can be derived from the former, but not the opposite.

Many end-users (palæontologists, palæoclimate or mantle dynamics modellers) use a map (often without citing the source) of the palæogeography for a given time. However, there are various reconstructions of palæogeographies, based upon numerous plate tectonic models.

Aimed primarily at end-users, the presentation will focus on what are the main similarities and differences when creating a plate tectonic model. Then, different ways (mainly two) of proposing palæogeographies will also be discussed.

This information is crucial when using such maps and can have a significant impact on interpretations drawn from climate simulations or studies of the evolution of life through Earth history.

How to cite: Vérard, C. and Franziskakis, F.: The different approaches for reconstructing palæogeography at the global scale in deep time, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7347, https://doi.org/10.5194/egusphere-egu26-7347, 2026.

Despite evidence for generally elevated atmospheric CO₂ concentrations, the climate of the early Phanerozoic appears to have been neither uniformly warm nor stable. Proxy records, climate simulations, and paleogeographic reconstructions all carry large uncertainties, yet taken together they suggest that greenhouse forcing alone may not fully explain observed climatic variability, including intervals of pronounced cooling, such as the Hirnatian Glaciation. Understanding how early Phanerozoic climate responded to high CO₂ therefore requires explicit consideration of the boundary conditions under which greenhouse forcing operated.

Here, we examine the combined roles of paleogeography, land-surface properties, and reduced solar luminosity in shaping early Phanerozoic climate states. Using an intermediate-complexity Earth system model, we systematically explore climate sensitivity across a wide range of atmospheric CO₂ concentrations under pre-vegetation boundary conditions and early Paleozoic paleogeographic configurations. The experimental design focuses on how land–sea distribution, continental arrangement, and surface characteristics influence large-scale heat transport, cryospheric feedbacks, and the CO₂ levels required to maintain ice-free conditions.

Our working hypothesis is that early Phanerozoic climates were intrinsically biased toward cooler states relative to later, vegetated periods, due to higher surface albedo, altered hydrological cycling, and reduced incoming solar radiation. In such a climate system, maintaining temperate conditions may have required persistently high CO₂ concentrations, while gradual CO₂ drawdown could have positioned the system close to critical thresholds. Under these circumstances, comparatively small paleogeographic changes—such as shifts in continental connectivity or topographic relief—may have been sufficient to trigger short-lived glacial episodes, without invoking abrupt or extreme changes in greenhouse forcing.

By framing early Phanerozoic climate evolution as a problem of threshold behavior under uncertain boundary conditions, this work aims to clarify why high CO₂ and cooling are not necessarily incompatible. The results will help constrain which combinations of forcing and boundary conditions are physically plausible and guide more robust interpretations of proxy records and future paleoclimate modeling efforts.

How to cite: Werner, N., Franziskakis, F., Merdith, A., Vérard, C., Brunetti, M., Gerya, T., and Tackley, P.: Climate Sensitivity in a Pre-Plant World: Why High CO₂ May Not Have Been Sufficient to Maintain a Paleozoic Hothouse, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7546, https://doi.org/10.5194/egusphere-egu26-7546, 2026.

During the last million years, the growth and retreat of massive ice sheets in North America and Eurasia defined the alternating climate conditions of the glacial-interglacial cycle. The main driver of these climatic oscillations is the combined effect of precession, eccentricity, and obliquity frequency modes (Milankovitch cycles) [1]. However, the climate expected from the Milankovitch cycles does not always align with the records from the Marine Isotope Stages [2].

To address this discrepancy, we test the hypothesis that multiple climatic steady states (attractors) exist for a given CO₂ concentration and can be destabilized by different combinations of Milankovitch forcing. We developed a biogeodynamical coupled setup, biogeodyn-MITgcmIS [3], which has the MIT general circulation model as its dynamical core, and asynchronously couples hydrology, ice sheets, and vegetation. The results of this new coupled model show that including the long-term dynamics of vegetation and ice sheets is crucial to evaluate past and future climate trajectories.  
 
First, we construct the bifurcation diagram by varying the CO₂ concentration between 180 ppm and 320 ppm (i.e., within the observed range over the last 1 Myr). We analyze the stability range of the cold (glacial) and warm (interglacial) attractors, and identify their tipping points at the global scale. Second, we repeat selected simulations with different Milankovitch configurations to evaluate the robustness of the bifurcation structure. Finally, to detect signatures of climate multistability, we compare the simulation outputs with global mean sea level and temperature reconstructions [4], and we discuss preliminary results. 

[1] Barker et al. Science 387, eadp3491 (2025)

[2] Past Interglacials Working Group of PAGES, Rev. Geophys. 54, 162–219 (2016)

[3] Moinat et al. EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-2946 (2025).

[4] Clark et al. Science 390, eadv8389 (2025)

How to cite: Moinat, L., Vérard, C., Goldberg, D. N., Kasparian, J., Gerya, T., Marshall, J., and Brunetti, M.: Effect of the Milankovitch cycles on climate multistability for the last 1 Myr, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7612, https://doi.org/10.5194/egusphere-egu26-7612, 2026.

The evolution of plant diversity through Phanerozoic time is often understood as a succession of dominating evolutionary floras. Following the onset of land plant expansion and diversification in the Silurian to Middle Devonian, these include the successive dominance of plant ecosystems by spore-bearing plants (Paleophytic flora), gymnosperms (Mesophytic flora), and angiosperms (Cenophytic flora). The succession of these floras is associated with major evolutionary innovations in plant growth forms, physiology and reproductive systems, allowing for new strategies to utilize resources and diversify. In concert with biological innovation, environmental conditions over the Phanerozoic have strongly varied due to plate tectonic rearrangements of continents and topography, together with variation in atmospheric CO₂ and climate. However, our understanding of how biological innovation and environmental changes interacted to shape the diversity of land plants through deep time is limited by a fragmentary geologic record of both plant diversity and environmental conditions.

Here, we reconstruct high-resolution climatologies (0.5° in longitude and latitude) over the last 470 million years using the fully coupled atmosphere-ocean general circulation model HadCM3 [1], the landscape evolution model goSPL [2], and the mechanistic climate downscaling algorithm CHELSA [3]. Applying the trait-based plant diversity model TREED [4] we then investigate how paleogeographic changes, variation in atmospheric CO₂, and climate conditions shaped the Phanerozoic plant diversification. Combining the model-based diversity reconstruction with an analysis of 140,000 plant fossil occurrences from the Paleobiology Database, we show that Phanerozoic plant genus originations were strongly associated with variation in atmospheric CO₂ and the tectonic supercontinent cycle, both limiting terrestrial resource and niche availability, and modulating the efficiency of environmental heterogeneity to generate diversity. We further show that the angiosperm terrestrial revolution is unique not only due to the intrinsic diversification potential of flowering plants, but also because of the exceptional environmental opportunities following the Pangea supercontinent breakup.

[1] P. J. Valdes, et al., The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0. Geoscientific Model Development 10 (10), 3715–3743 (2017), doi:10.5194/gmd-10-3715-2017, https://gmd.copernicus.org/articles/10/3715/2017/

[2] T. Salles, et al., Landscape dynamics and the Phanerozoic diversification of the biosphere. Nature 624 (7990), 115–121 (2023), doi: 10.1038/s41586-023-06777-z, https://www.nature.com/articles/s41586-023-06777-z

[3] D. N. Karger, et al., Climatologies at high resolution for the earth’s land surface areas. Scientific Data 4 (1), 170122 (2017), doi:10.1038/sdata.2017.122, https://www.nature.com/articles/sdata2017122

[4] J. Rogger, et al., TREED (v1.0): a trait- and optimality-based eco-evolutionary vegetation model for the deep past and the present (2025), doi:10.5194/egusphere-2025-6002, https://egusphere.copernicus.org/preprints/2025/egusphere-2025-6002/

How to cite: Rogger, J., Allen, B., Donoghue, P., Karger, D., Salles, T., Skeels, A., and Lunt, D.: Timing and magnitude of Phanerozoic plant diversification are linked to paleogeography and atmospheric CO2, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7891, https://doi.org/10.5194/egusphere-egu26-7891, 2026.

During the Cambrian explosion, animals underwent profound ecological and evolutionary configuration. Small shelly fossils (SSFs), micrometre- to millimetre-scale skeletal elements representing multiple animal phyla, are particularly valuable for early Cambrian biostratigraphy and intercontinental correlation because of their widespread distribution. SSFs from North Greenland provide a high-resolution record of biotic and environmental change along the eastern margin of Laurentia. Here, we document a SSF assemblage that includes molluscs, hyoliths, brachiopods, ecdysozoans, echinoderms, and several problematic taxa from the Aftenstjernesø Formation in North Greenland. This integrated dataset enables detailed correlation with other Cambrian Series 2, Stage 4 successions on several palaeocontinents, including Gondwana, Siberia, and peri-Gondwana, based on shared taxa. During this period, many regions record a major faunal collapse associated with the first widely recognized Phanerozoic extinction event, the so-called Sinsk event, which has been linked to marine anoxia, decrease of diversity, and body-size reduction. In contrast, the Laurentian margin records pronounced taxonomic turnover dominated by faunal replacement rather than a net loss of diversity. This difference underscores the importance of palaeogeography and local geodynamic conditions in modulating how early Cambrian environmental crises were expressed biologically, and it demonstrates the utility of SSFs for reconstructing the biotic response to early Cambrian environmental crises.

How to cite: Oh, Y., Park, T.-Y. S., and Peel, J. S.: Global correlation of small shelly fossils from North Greenland and their importance for early Cambrian ecosystem change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8575, https://doi.org/10.5194/egusphere-egu26-8575, 2026.

Over geological timescales climate is regulated by the long carbon cycle, in which a balance is struck between CO₂ degassing from the solid Earth and CO₂ consumption by continental silicate weathering stabilizing atmospheric CO₂ levels and maintain habitable conditions. Geodynamic processes regulate both CO₂ degassing rates as well as the distribution and elevation of continents, thereby controlling continental weatherability and, ultimately, atmospheric CO₂ and long-term climate.

However, long-term carbon cycle models are often limited by their definition of degassing independently of geodynamics evolution and their inevitable attribution of continental weatherability as the primary driver of long-term climate. Furthermore, the sparsity of the geological record means that models often rely on observations of present-day Earth to simulate past Earth states. All these constrains provide limited insight into how geodynamics interacts with climate, and surface processes to regulate atmospheric CO₂ over geological timescales.

To address these limitations, we use fully integrated "digital siblings” of the Earth: 3D fully virtual planets designed to simulate internally consistent evolution of habitable planets over a several 100~Myr timescales, not necessarily aiming to replicate Earth. We integrate three numerical models in a dynamically interdependent framework: the geodynamic model StagYY (Coltice et al., 2019), the climate model PLASIM-GENIE (Holden et al., 2016), and the surface processes model goSPL (Salles et al., 2023).

From these simulations, we compute time-dependent CO₂ degassing rates, using geodynamic outputs, and weathering fluxes, using the formulation of West (2012). Our results reveal fluctuations in degassing rate over a factor of about three, consistent with reconstruction of Earth (Müller et al., 2024) and correlated with seafloor production rate. Weatherability strongly depends on True Polar Wander during supercontinent aggregation, and on sea level fluctuations controlled by seafloor production. Together, these results highlight how geodynamic evolution may regulate the long-term carbon cycle through its interdependent effects on degassing and continental weatherability.

How to cite: Martin, M., Coltice, N., Donnadieu, Y., Maffre, P., Salles, T., Rogger, J., Arnould, M., Husson, L., Leonard, J., Zahirovic, S., and Pellissier, L.: Geodynamic controls on long-term carbon cycle: insights from fully integrated virtual planets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9305, https://doi.org/10.5194/egusphere-egu26-9305, 2026.

The supercontinent cycle is often accompanied by True Polar Wander (TPW) events (Evans, 2003) — reorientation of the silicate Earth relative to its spin axis in response to internal mass redistribution. During TPW events, the maximum inertia axis (I_max) aligns with the spin axis to conserve the angular momentum (Gold, 1955). While an assembled supercontinent typically reside near the equator once it has developed its own degree-2 mantle structure driven by a circum-supercontinent subduction girdle with two antipodal superplumes (Li et al., 2023), this configuration is not always instantaneous with the assembly of a supercontinent. Supercontinent is in fact believed by some to assembly over a degree-1 mantle structure: a cold downwelling beneath the supercontinent and a hemispheric superplume on the opposite hemisphere (Zhong et al., 2007; Zhong and Liu, 2016). The resulting TPW behavior during such processes remains poorly constrained. Here we report a novel computational framework that couples 3D spherical mantle convection (CitcomS) with Earth’s rotational dynamics to simulate TPW driven by both convective mass anomalies and rotational bulge readjustment. We particularly examined the effect of varying upper/lower mantle viscosity ratios (η_um/η_lm).

Our results reveal a critical dependence of TPW behavior on viscosity stratification. For high η_um/η_lm (1:30), supercontinents assemble near the pole over a degree-1 mantle structure. Subsequent formation of a subduction girdle triggers TPW, transporting the supercontinent to the equator. In contrast, low η_um/η_lm (1:100) with a mean lower-mantle viscosity of 3×10²² Pa·s promotes equatorial assembly. Here, girdle development induces TPW that transports the supercontinent toward the pole, where it stabilizes for a considerable period. However, reducing lower-mantle viscosity destabilizes this polar position, causing rapid return to the equator. These dynamics arise because viscosity stratification determines the structure of the geoid kernel, which governs the geoid’s response to mass anomalies and thereby modulates TPW pathways. Our models demonstrate that before a stable degree-2 structure (e.g., modern LLSVPs) is developed, TPW can drive complex supercontinent trajectories—including equator-to-pole-to-equator round-trip migrations. Future work integrating plate reconstruction with viscosity constraints will refine predictions for specific supercontinents.

Evans, D. True Polar Wander and Supercontinents. Tectonophysics 362, 303-320 (2003).

Gold, T. Instability of the Earth’s axis of rotation. Nature 175, 526–529 (1955).

Li, Z.-X., Liu, Y. & Ernst, R. A dynamic 2000–540 Ma Earth history: From cratonic amalgamation to the age of supercontinent cycle. Earth-Science Reviews 238, 104336(2023).

Zhong, S., Zhang, N., Li, Z.-X. & Roberts, J. H. Supercontinent cycles, true polar wander, and very long-wavelength mantle convection. Earth and Planetary Science Letters 261, 551–564 (2007).

Zhong, S. & Liu, X. The Long-Wavelength Mantle Structure and Dynamics and Implications for Large-Scale Tectonics and Volcanism in the Phanerozoic. Gondwana Research 29: 83-104 (2016).

How to cite: Liu, Y., Li, Z.-X., and Liu, X.:  Numerical Simulation of True Polar Wander during Supercontinent Assembly, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10596, https://doi.org/10.5194/egusphere-egu26-10596, 2026.

The Ediacaran-Cambrian Transition (approx. 550-539 mya) was one of the planet’s most revolutionary events, marking the emergence of diverse and abundant animals. Changing environmental conditions – such as oxygen availability, carbon cycling and nutrient levels – are likely to have been both constricting and galvanising, resulting in the rapid radiation of diverse body plans alongside a permanently altered ocean-atmosphere system. For my PhD research, as part of the UK’s first Doctoral Training Programme in Extinction Studies, I took a biocultural approach, seeking to acknowledge both the catastrophic and creative aspects of ecological regime shifts, whilst offering an artistic response to the complex processes that occur at key chronostratigraphic boundaries, from mass extinctions and evolutionary radiations to global oxidation events. Combining palaeontological study and creative practice, I established a novel methodology conducting ‘lyric fieldwork’ at Global Stratotypes and Section Points, writing a radically ‘indisciplined’ thesis and accompanying long poem spanning deep time, from the Precambrian through to the Phanerozoic. In this presentation – a performative reading – I will share an excerpt of my poem, focusing on the closing moments of the Proterozoic Eon and the start of the Phanerozoic Era, where the Ediacaran Period moves into the Cambrian Period, and where major geochemical perturbations correspond with an ‘explosion’ of biological innovations, from biomineralisation and the evolution of hard body parts to the rise of predator-prey dynamics and increased locomotive strategies. 

How to cite: Simpson, K.: Ending the Proterozoic: A Poetic Reimagining , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10751, https://doi.org/10.5194/egusphere-egu26-10751, 2026.

The Phanerozoic Eon is characterized by profound variability in global climate and biogeochemical cycles, driven by some combination of the formation and break up of supercontinents, changes to tectonic degassing, the emplacement of Large Igneous Provinces and by biosphere evolution. Understanding the key drivers of these environmental transitions is an ongoing challenge in deep-time Earth system science.

The Spatially Continuous IntegratiON (SCION) climate-biogeochemical model is often used for the analysis these processes, and has successfully reproduced a number of first-order global trends through the Phanerozoic (1) and Neoproterozoic (2), including reconstructions of atmospheric CO₂, atmospheric O₂, and surface temperature. But many notable mismatches still occur, e.g. during the late Paleozoic icehouse interval and in the underestimation of warmth during the Cretaceous greenhouse period. Furthermore, many novel or revised proxy records have not yet been compared to the model outputs (e.g. global erosion rates (3), or new records for Phanerozoic temperature evolution (4) and atmospheric CO₂ (5)).

Here, we present a new integration of multiple environmental proxy record compilations with the SCION model outputs. We determine the key periods of model-data mismatch and explore possible solutions within the current model formulation, or possible model extensions. We then suggest critical intervals where proxy development or sampling work may be best directed.

(1) Merdith et al., 2025, Science Advances

(2) Mills et al., 2025, Global and Planetary Change

(3) Hay et al., 2006, Palaeo3

(4) Judd et al., 2024, Paleoclimate

(5) Steinthorsdottir et al., 2024, Treatise on Geochemistry

How to cite: Krewer, C. and Mills, B. J. W.: Modelling the Phanerozoic: Discrepancies and conformity with the geological record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11212, https://doi.org/10.5194/egusphere-egu26-11212, 2026.

During the Neoproterozoic, early land biota consisted of cyanobacteria, microalgae and various fungi or fungi-like communities. Although called micro-organisms, their role in stabilising environments, and driving and controlling nutrient cycles [1], creates a macro-scale impact. Photosynthetic microbial mats are predicted to have been present ~3 billion years ago, creating microcosms of oxygen-rich environments that contribute towards global net primary productivity, weathering and nitrogen fixation [2]. However due to the lack of fossil evidence and understanding of their role in a non-vegetated environment, it is unclear what their impact is on biogeochemical cycling and thus the shaping of Neoproterozoic climate. Building on the new process based spatial vegetation model [3], we try to understand the role of expanding microbial communities on events such as the Neoproterozic Oxygenation Event and Snowball Earth.

[1] Taylor, T.N., Krings, M. (2005) Fossil microorganisms and land plants: Associations and interactions. Symbiosis 40:119-135

[2] Lenton, T.M., Daines, S.J. (2016) Matworld- the biogeochemical effects of early life on land. New Phytologist 215: 505-507

[3] Gurung, K., Field, K.J, et al. (2024) Geographic range of plants drives long-term climate change. Nature Comms 15: 1805

How to cite: Gurung, K. and Mills, B. J. W.: Influence of terrestrial productivity by photosynthetic microbial mats on biogeochemical cycles over the Neoproterozoic landscape, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11296, https://doi.org/10.5194/egusphere-egu26-11296, 2026.

The mass extinction occurred at the Cretaceous/Paleogene (K/Pg) boundary event, approximately 66 million years ago, which resulted in global-scale biotic turnover that was ecologically diverse but selective. This extinction coincides with both the activities of Deccan Traps volcanism spanning approximately one million years and a large asteroid impact which formed the Chicxulub crater on the Yucatan Peninsula, Mexico. These two events and their environmental and biological consequences left a global imprint in the deep-sea sediments. Deep-sea sediment records indicate the collapse of the oceanic bottom-to-surface gradient of carbon isotope ratio and the carbonate compensation depth (CCD) deepening for several hundred thousand years after the K/Pg boundary. The collapse of the carbon isotope gradient has been variously interpreted as changes in biological production, including a global shutdown of primary production, reduced export production, and enhanced spatial heterogeneity. However, these interpretations remain insufficiently tested for consistency with the geological records. The pronounced long-term decline of carbonate mass accumulation rates (MAR) after the K/Pg boundary is also indicated from deep-sea records. This suggests the necessity of a prolonged reduction in biological carbonate productivity. However, existing boron isotope-based ocean surface pH reconstructions do not support prolonged and severe ocean acidification, making it difficult to explain the long-term decrease of carbonate MAR.

Here, we first investigate changes in marine biological productivity and particulate organic matter (POM) decomposition rate using a vertical one-dimensional ocean carbon cycle model to interpret the collapse of the vertical carbon isotope gradient. We find that, provided POM production and burial persist in coastal regions, the collapse can be explained by either reduced export productivity in the open ocean or reduced POM sinking rates, but cannot discriminate them from the modeling of this study with existing data. These results support the discussion of Kump (1991) and the Living Ocean hypothesis (e.g., D’Hondt et al., 1998). In this model, the CCD deepened, but carbonate production rate was comparable to previous modelling studies, and we were unable to reproduce the pronounced long-term decline of carbonate MAR after the K/Pg boundary event.

Next, we explore an alternative explanation for the long-term decline in carbonate MAR based on changes in the structure of primary producers. At the K/Pg boundary, calcareous nannoplankton, such as coccolithophores, experienced catastrophic extinction, whereas non-calcifying phytoplankton, such as diatoms, were relatively resilient. In addition, enhanced diatom productivity has been suggested for several hundred thousand years following the K/Pg boundary in the South Pacific. Therefore, climate change and ocean eutrophication following the K/Pg boundary may have favored diatom primary production at the expense of carbonate production by calcareous nannoplankton, but its quantitative contribution remains poorly constrained. We will distinguish calcareous nannoplankton and diatoms by their physiological characteristics and explore how background environmental changes sustain enhanced diatom abundance and reduced carbonate production.

How to cite: Takeda, T. and Tajika, E.: Modelling the changes in marine ecosystem and carbon cycle after the K/Pg boundary event, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11517, https://doi.org/10.5194/egusphere-egu26-11517, 2026.

Cenozoic greenhouse climates offer important insights into Earth’s climate system and carbon cycle under elevated CO₂ conditions. A major challenge in simulating these warm intervals lies in the accurate reconstruction of the paleogeography, yet its impact on modeled climates and their agreement with proxy data remains poorly quantified. In this study, we systematically assess the sensitivity of fully coupled climate simulations to alternative paleogeographic reconstructions for the Paleocene, early Eocene, and middle-late Eocene. Using the IPSL-CM5A2 Earth System Model, we find that regional climates are particularly sensitive to the paleolatitudinal position of landmasses and ocean basins. Latitudinal shifts of more than 5°, arising from the choice of mantle versus paleomagnetic reference frame, significantly alter modeled regional temperature and precipitation patterns, as well as ocean circulation patterns. Moreover, we demonstrate that reconciling simulated climates with temperature proxy data depends strongly on the reconstructed paleolatitude of the proxy sites. In regions such as the southwest Pacific, correcting for paleolatitude bias induced by a mantle frame reduces model-data temperature misfits by up to 5°C. Our results further show that the regional climatic impact of paleogeography can equal or even exceed that of a doubling of atmospheric CO₂, particularly at mid-latitudes. These findings highlight the importance of using accurate paleogeographic reconstructions and an appropriate reference frame for improving paleoclimate simulations and their integration with proxy data.

How to cite: Vaes, B., Donnadieu, Y., Licht, A., Pineau, E., Maffre, P., Chalk, T., and Sternai, P.: Paleolatitude bias in reconstructions of Cenozoic greenhouse climates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11558, https://doi.org/10.5194/egusphere-egu26-11558, 2026.

Paleogeography is a key boundary condition for reconstructing Earth’s climatic evolution and habitability. On geological timescales, paleogeographic changes control the latitudinal positioning of environments, governing received and reflected solar radiation and climatic zonation. The distribution and morphology of continents and oceans further control ocean–atmosphere circulation and influence the evolution and dispersal of marine and terrestrial biota.

Here we present a new effort to construct a continuous (1 Myr resolution) global paleogeographic digital elevation model for the entire Phanerozoic (540–0 Ma). The reconstructions integrate new and previously published plate models, and global and regional paleo-elevation datasets. Building on and extending methodologies previously applied to the Cenozoic (66–0 Ma), our approach incorporates dynamic topography from mantle circulation (100–0 Ma), oceanic lithospheric ages, sediment thickness, detailed continental margin evolution, parameterized subduction zones, and spatiotemporal interpolation between topographic datasets of different time intervals. The reconstructions focus in detail on key paleogeographic features relevant for ocean circulation, climate, and biogeography, including oceanic gateways, land bridges, and large-scale orogenies.

Finally, we present results from a variety of fully coupled Earth system model experiments, mainly with Cenozoic paleogeographic boundary conditions (e.g., present, Eocene–Oligocene, Late Eocene, and the DeepMIP Early Eocene ensemble), to demonstrate how paleogeographic changes influences planetary energy budgets, ocean circulation, and climate sensitivity. These results highlight systematic relationships that offer potential for extrapolation throughout the Phanerozoic.

How to cite: Straume, E., Torsvik, T., Domeier, M., and Nummelin, A.: Phanerozoic paleogeography and its impact on long-term climatic change and habitability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13853, https://doi.org/10.5194/egusphere-egu26-13853, 2026.

Volcanic ash is known to influence a range of biogeochemical processes once deposited in the oceans, with explosive volcanism inputting large amounts of highly reactive and nutrient-rich material to the oceans every year. This material can stimulate increases in primary productivity, with ash alleviating nutrient limitations. This may eventually lead to enhanced carbon burial at the seafloor, with evidence from deep time suggesting this process may play a role in episodes of global cooling. As a result, reconstructing the amount of volcanic ash entering the oceans is important for understanding the role explosive volcanic activity has on global climates. However, extant records of changing volcanic intensity are either limited to regional studies of small numbers of volcanoes or are based on imperfect methods such as visible tephra layer counting.

In this work, we use the output of a model-derived dataset of sediment provenance from the Pacific Ocean, which provides estimates of changing volcanic material input for 67 sites. We use these data, and an inverse weighting approach, to reconstruct changing levels of volcanic ash input for the Cenozoic Period (66 million years ago to present). With around 75% of all active volcanoes located in the Pacific Ring of Fire, this record likely represents the majority of all volcanic ash through the Cenozoic, and so we compare it to known climate change through the period. We see increases in volcanic ash input around 35 million years ago and 10 million years ago, which can be linked to eruptions from the Sierra Madre Occidental, and Izu Bonin Arc, respectively. The first uptick occurs at the same time as the Eocene-Oligocene transition, an episode of global climate cooling, whilst the second covers the descent into the Pleistocene glaciations. These findings hint at the climatic impact of ash input, one which has major implications for the development of the Earth system.

How to cite: Longman, J., Dunlea, A. G., and Merdith, A. S.: Reconstructing volcanic ash input to the Pacific Ocean: how does it link to Cenozoic climate?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14220, https://doi.org/10.5194/egusphere-egu26-14220, 2026.

The Great Ordovician Biodiversification Event (GOBE) marks one of the most profound radiations of marine life in Earth history. Numerous hypotheses have been proposed for the drivers of the increase in richness during this interval. Distinguishing among these factors requires biodiversity to be evaluated at both local and regional scales across different environments. Here, we compiled a high-resolution, assemblage-level dataset comprising 557 stratigraphic sections and 12,898 fossil occurrences from South China. We integrated these records using a quantitative stratigraphic approach, to examine changes in local (assemblage-level) and regional marine species richness from the Furongian (late Cambrian) to the Middle Ordovician across four depositional environments: littoral, platform, slope, and deep-shelf. We additionally assessed faunal differences across environments and geographic space. Our results suggest regional richness increased four-fold during the GOBE, closely paralleling the spatial expansion of fossil-bearing environments, especially the platform and slope. In contrast, local (assemblage-level) richness remained relatively stable and low through the study interval, despite fluctuations within the slope environment. The taxonomic composition of the platform and slope environments diverged during the GOBE, and spatial turnover increased from the early to late stages of the GOBE. Our findings suggest the expansion of shallow-marine environments tied to increasing sea levels may have been one of the primary drivers of the Ordovician marine biodiversification in South China, with increased faunal differentiation across both environment and space.

How to cite: Huang, H., Chu, T., Deng, Y., Zhang, L., Fan, J., and Saupe, E. E.: Local diversity remained relatively stable across the Great Ordovician Biodiversification Event (GOBE) in South China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15332, https://doi.org/10.5194/egusphere-egu26-15332, 2026.

The progressive restriction of seaways between the Caribbean and Pacific during the formation of the Isthmus of Panama fundamentally reorganized ocean circulation, biogeochemical cycling, and marine ecosystem structure across the tropical Americas. This tectonically driven reorganization provides a natural experiment for examining how long-term Earth system processes influence the structure, stability, and resilience of biological communities. The Bocas del Toro region of Caribbean Panama preserves a rich fossil record that captures ecological responses to these coupled physical and environmental changes.

This study examines temporal variation in marine community composition and functional trait structure using fossil assemblages from four marine formations: Cayo Agua, Escudo de Veraguas, Old Bank, and Isla Colón, spanning approximately 6.0 to 0.43 Ma. The analyses integrate multiple taxonomic groups, including bivalves, gastropods, bryozoans, corals, and fishes, enabling comparison of ecological responses among organisms that differ in life habit, mobility, feeding strategy, tiering, and ecological function. By incorporating multiple clades with contrasting ecologies, this approach allows assessment of whether community change reflects reorganization within broadly conserved functional roles or more fundamental shifts in ecosystem structure.

Community dynamics are quantified using a combination of model-based ordination, taxon-specific response analyses, and functional diversity metrics applied within a stratigraphic framework. These methods explicitly account for variation in sampling intensity and taxonomic richness, allowing ecological patterns to be distinguished from sampling effects. Biological patterns are evaluated alongside sedimentological and geochemical records to place community dynamics within their environmental context. Environmental–trait and environmental–taxon relationships are evaluated within a generalized linear latent variable modeling (GLLVM) framework to assess how changes in physical conditions, sedimentary processes, and geochemical variability influence community reorganization before, during, and after the formation of the Isthmus of Panama. Comparisons among contemporaneous formations allow local ecological responses to be distinguished from regionally coherent environmental signals.

Overall, this study aims to clarify how long-term tectonic and oceanographic reorganization shapes marine ecosystem structure and stability, providing a stratigraphically grounded perspective on the links between Earth system processes and ecological dynamics over geological timescales.

How to cite: Godbold, A., O’Dea, A., Grossman, E. L., de Gracia, B., Pardo Díaz, J., Pallacks, S., Todd, J., Johnson, K., and Connolly, S. R.: Biogeodynamic controls on Caribbean community structure during the formation of the Isthmus of Panama , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15410, https://doi.org/10.5194/egusphere-egu26-15410, 2026.

The reconstruction of paleogeography, that is, the reconstruction of Earth’s surface elevation within a plate tectonic context, is crucial for understanding changes in past climate, sea level, as well as variations in biodiversity through deep time. Although often presented as picturesque maps in publications or even museums, paleogeography reconstructions can provide important geoscientific context and serve as a key boundary condition in many aspects of Earth science including, but not limited to, the simulation of past climates and landscape evolution modelling. However, despite the potential influence and impact of paleogeography on many aspects of Earth’s history, there are very few published global reconstructions of paleogeography, and available reconstructions are often constrained to a single time slice (e.g., Middle Miocene, ~15 Ma), or are available in and represent longer (~5–10 Myr) increments. Additionally, there are major uncertainties in reconstructions of paleogeography, in part due to the poor temporal and/or spatial coverage of proxy data, but also uncertainties within the underlying workflows used to derive its key components. Here, I examine published paleogeography reconstructions throughout the Cenozoic, focusing on key time intervals. I compare the similarities and differences in reconstructions, including aspects of their workflows and sources of uncertainties within them. Finally, I present new approaches for generating paleogeography and quantified uncertainties in a more open and reproducible framework, allowing for future advances in proxy data and other constraints to be incorporated.

How to cite: Wright, N.: Current state and future directions in paleogeography reconstructions throughout the Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15492, https://doi.org/10.5194/egusphere-egu26-15492, 2026.

Insects are the most diverse groups on earth and preserved with plenty of fossils. Disentangling their ecological roles are crucial for understanding the evolution of terrestrial ecosystems, however, reconstructing the adaptive evolution of extinct insects has been proven to be highly challenging. Here, we conduct integrated approaches to reveal the macroevolution of two insect clades, katydids (Hagloidea) and giant cicadas (Palaeontinidae), on the basis of newly compiled morphological datasets. Our results provide novel information for coevolution of insects and vertebrates in the Mesozoic, and highlight the significance of fossil morphologies. 1) Acoustic evolution of katydids. We present a database of the stridulatory apparatus and wing morphology of Mesozoic katydids and analyze the evolution of their acoustic communication. Our results demonstrate that katydids evolved complex acoustic communication including mating signals, intermale communication, and directional hearing, by the Middle Jurassic; evolved high-frequency musical calls by the Late Triassic. The Early—Middle Jurassic katydid transition coincided with the diversification of mammalian clades, supporting the hypothesis of the acoustic coevolution of mammals and katydids. 2) Flight evolution of giant cicadas. We reveal the flight evolution of the Mesozoic arboreal insect clade Palaeontinidae. Our analyses unveil a faunal turnover from early to late Palaeontinidae during the Jurassic–Cretaceous, accompanied by a morphological adaptive shift and improvement in flight abilities including increased speed and enhanced maneuverability. The adaptive aerodynamic evolution of Palaeontinidae may have been stimulated by the rise of early birds, supporting the hypothesis of an aerial evolutionary arms race between Palaeontinidae and birds.

How to cite: Xu, C.: Coevolution of Insects and vertebrates in the Mesozoic: examples from katydids and giant cicadas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15628, https://doi.org/10.5194/egusphere-egu26-15628, 2026.

Sediment-hosted copper–cobalt and base metal deposits are critical to the global energy transition, yet the environmental conditions that favour their formation and preservation through Earth history remain poorly understood. Evaporites are considered crucial for the formation of sediment-hosted ore deposits as they generate saline brines that circulate metals and sulphur. These tend to form in desert belts at particular latitudes where evaporation outpaces rainfall. The world’s largest sediment-hosted Cu-Co deposits – located in the Central African Copperbelt – are hosted by Neoproterozoic rocks that formed during one of Earth’s most chaotic climatic periods. Whether this is a coincidence, or whether extreme climate plays a role in mineralisation remains to be tested. The relative roles of tectonic setting, climate and latitude remain poorly constrained but have important implications for predicting where sediment-hosted ore deposits formed in deep time.

We integrate a global database of sediment-hosted ore deposits with full-plate tectonic reconstructions spanning the last billion years to explore the relationship between deposits, paleolatitude and tectonic setting. Plate reconstructions and fossil rift margin datasets are used to assess the spatial association between ore deposits and long-lived extensional settings, with a focus on Neoproterozoic basins.

Preliminary results indicate a spatial correlation between sediment-hosted ore deposits and rifted continental margins. Paleolatitude reconstructions suggest that many deposits formed at low to mid latitudes; however, their distribution varies through time, which may be driven by major climatic fluctuations, including global-scale glaciations. Ongoing work integrating depositional age constraints from key regions and paleoclimate model outputs aims to further quantify these relationships and refine predictive frameworks for underexplored sedimentary basins.

How to cite: Armistead, S. and Williams, S.: Tectonic and climatic influence on sediment-hosted ore deposits in deep time , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16017, https://doi.org/10.5194/egusphere-egu26-16017, 2026.

Geodynamic redistribution of continents fundamentally reshapes Earth’s climate, ocean circulation, and nutrient cycles, thereby exerting a first-order control on biological evolution. A possible example of this coupling is the Cambrian explosion, a rapid diversification of animal life that followed profound tectonic, climatic, and oceanographic reorganization during the late Neoproterozoic. However, identifying the causal drivers of the Cambrian explosion remains challenging due to the fragmentary geological record.  To circumvent these limitations, we implement an integrated, mechanistic simulation framework that integrates the key Earth system processes governing climate, circulation, surface evolution, and marine biogeochemistry, allowing their interactions to be explored consistently in space and time. These components provide time-evolving boundary conditions for biological productivity, oxygen availability, and nutrient supply, which are then used to study how changing environmental states shape the range of biologically feasible organismal strategies.  Rather than simulating realized biodiversity or reconstructing a specific episode of Earth history, the model explores the full dynamical evolution of an Earth-like system across a supercontinent cycle, from continental assembly to breakup. In this framework, changing Earth system states expand or restrict the range of biologically feasible organismal strategies, providing a quantitative link between paleogeographic restructuring and the environmental opening of functional trait space relevant to the Cambrian explosion.  

How to cite: Lewkowicz, A., Affholder, A., Coltice, N., Martin, M., Salles, T., Werner, N., Leonard, J., and Pellissier, L.: Linking paleogeography and Earth system dynamics to evolutionary innovation during the Cambrian Explosion , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16603, https://doi.org/10.5194/egusphere-egu26-16603, 2026.

Biogeodynamics research seeks to link lithospheric scale processes with surface ecosystem evolution. Western Anatolia-Aegean region provides a critical testing ground for this coupling, where mantle dynamics have driven dramatic topographic reversals. Tectonostratigraphic and geomorphic insights indicate that Western Anatolia maintained elevated landscapes prior to and through Early Miocene extension. These observations are inconsistent with simple rift-related thinning but support dynamic uplift driven by removal of dense lithospheric mantle. Here, we integrate geodynamic modeling with geological observations to reconstruct the region's paleoelevation and its control on intercontinental faunal connectivity.  Our results indicate that lithospheric delamination (slab peel-back) was the primary driver of Early Miocene topography. Numerical models show that slab peeling from beneath the crust and subsequent asthenospheric upwelling triggered a transient surface uplift of > 1 km and southward younging volcanism from İzmir-Ankara suture to the western Taurides. Supported by metamorphic constraints indicating crustal thickness consistent with elevations of 2–3 km, these results are in good agreement with the existence of a paleo-"Anatolian Highland" at ~20 Ma.  Crucially, this geodynamically sustained topography acted as a significant biogeographic barrier. Synthesizing our models with recent fossil record analyses, we suggest that high elevations delayed faunal migration between Eurasia and Afro-Arabia, severing connectivity despite the closure of the Neo-Tethys. The timing of increased biotic interchange in the Middle–Late Miocene coincides with evidence for topographic lowering linked to post-delamination driven by crustal stretching.  We conclude that the thermal and mechanical evolution of the Anatolian lithosphere exerted a first-order control on the timing of biotic exchange, highlighting the direct link between lithosphere dynamics and vertebrate evolution.

How to cite: Göğüş, O. H., Saylor, J., Biltekin, D., Sundell, K., Mackaman-Lofland, C., Guan, X., Özyalçın, C., and Bodur, Ö.: Biogeodynamic Barrier: Lithospheric Delamination and Delayed Miocene Faunal Migration in the Anatolian Highland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16889, https://doi.org/10.5194/egusphere-egu26-16889, 2026.

How to cite: Franziskakis, F., Werner, N., Vérard, C., Castelltort, S., and Giuliani, G.: Assessing Sediment Flux Evolution for the entire Phanerozoic with Palaeogeography and Palaeoclimate simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17018, https://doi.org/10.5194/egusphere-egu26-17018, 2026.

The Pannonian Basin in Central and Southeastern Europe is a huge landlocked basin delineated by Alpine-Carpathian-Dinarides chain. This extensional backarc basin originating by tectonic rifting in the Early Miocene, was successively flooded by the Central Paratethys Sea. Slovenian Corridor along the Alpine-Dinarides junction enabled its communication with the Mediterranean Sea.  Marine flooding of the southern part of the Pannonian Basin - between the Styrian Basin in Austria and Velika Morava Basin in Serbia - is still poorly understood. While the conflicting biostratigraphic interpretations contribute to ongoing discussion on timing and mode of this major environmental turnover, independent radiometric data are still rare.  The present study contributes three new U-Pb zircon ages which are the very first such data on the Miocene marine transgression in northern Bosnia and Herzegovina. Dating from autochthonous tephra airfalls prove uniformly the middle Badenian age for marine transgression, with a 0.5 Ma eastwards-younging trend of its onset. This trend stays in line with the literature data suggesting a steady eastwards propagation of extension along the Pannonian Basin southern margin. Towards a better understanding of interplay between tectonic and glacioeustatic forcing of the regional marine progression, a review of published stratigraphic data has been conducted, depicted correspondingly in four paleogeographic maps of one-million-year resolution. Building on these data, we bracket the initial gradual flooding interval to the late Burdigalian–early Serravallian time interval, respectively, attaining up to 3.5 Myr overall duration in a step-wise manner.  Although the tectonic phases were main drivers in the creation of accommodation space, along the NE Dinarides, glacioeustasy driven by the global climate suspended landward propagation of the coastline during sea-level low-stands at long obliquity nodes. This result enables a more precise reconstruction of the interplay between landward sea ingression, regional climate change and effects to endemic evolution of biota inhabiting long-lived paleolakes in adjoining intramountainous basins.

This research was funded by the Austrian Science Fund (FWF) grant DOI 10.55776/I6504 and by the Deutsche Forschungsgemeinschaft (DFG) grant no. TO 1364/3-1.

How to cite: Mandic, O., Andrić-Tomašević, N., Šamarija, R., Ćorić, S., Rundić, L., Zeh, A., Pavelić, D., Vrabac, S., and Grunert, P.: Timing and mode of initial marine flooding in the southern Pannonian Basin: new U-Pb age constraints from the Prnjavor and Tuzla basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17538, https://doi.org/10.5194/egusphere-egu26-17538, 2026.

The strontium isotope ratio of ⁸⁷Sr/⁸⁶Sr is one of the best-defined tracers of Earth’s evolving surface environment over the Eon of macroscopic life, due to the long residence time of Sr in the ocean. If offers tantalising clues about past CO₂ emissions and the rate of continental weathering, which are vital considerations for understanding Earth’s changing surface temperature, climate, and atmospheric oxygen abundance. However, the Sr isotope ratio has strong regional lithological control, with mafic and felsic rocks having dramatically different isotopic compositions, which limits any simple analysis of Sr ratios over Phanerozoic timescales. We present an update to the SCION Earth Evolution Model, which allows it to track the spatial distribution of lithologies and Sr compositions over deep time, enabling regional-scale Sr isotope inputs to be assessed in the context of wider Earth system evolution. We use this to explore to what degree we currently understand the Phanerozoic Sr record, and how it can be used as a proxy to validate or falsify theories about long-term climate change and oxygen levels.

How to cite: Mills, B., Longman, J., and Merdith, A.: Understanding the drivers of the Phanerozoic strontium isotope record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18914, https://doi.org/10.5194/egusphere-egu26-18914, 2026.

Changes in atmospheric CO₂ concentrations during the last deglaciation have been attributed to the release of fossil carbon. However, the processes and mechanisms of the various carbon sources that contributed to this change in the carbon cycle are not yet fully understood. Cold-water corals and their ecosystems are considered important carbonate factories in the Arctic and are particularly vulnerable to changes in the carbon cycle and present an unique archive recording such changes.

Here, we present paired ²³⁰Th/U and radiocarbon (¹⁴C) measurements on pristine fragments of the scleractinian cold-water coral Desmophyllum pertusum, combined with measurements of stable carbon isotopes (δ¹³C) on various benthic foraminifera from a sediment core taken from the Lopphavet CWC reef (71°N, 21°E) covering the last 10 kyrs. This combined approach helps to narrow down sources of carbon cycled within this Holocene CWC reef in the Arctic.

Our results show Δ¹⁴C values that are as low as -500 ‰ resulting in extremely high bottom- atmosphere ages of up to 6000 years. Radiocarbon simulations performed with the ¹⁴C-equipped model CLIMBER-X show that such negative Δ¹⁴C values and high ventilation ages cannot be explained by oceanographically controlled changes in the marine radiocarbon cycle of the Arctic Ocean. Furthermore, the δ¹³C values of various benthic foraminifera with different microhabitats show the expected offsets, suggesting that the carbon source does not originate from dissociations of gas-hydrates.

We suggest that a continuous retreat of the ice-sheets has led to an accelerated release of terrestrial organic carbon into the Norwegian Arctic Ocean on which the corals fed on.  

Our results therefore highlight the need for further studies that constrain the mechanism and processes of organic carbon pathways from high-latitude terrestrial regime into the Arctic Ocean, especially in high latitude carbonate factories.  

How to cite: Raddatz, J., Butzin, M., Flögel, S., Rüggeberg, A., Wallmann, K., and Frank, N.:  Arctic cold-water corals record depleted radiocarbon signatures during the Holocene , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19123, https://doi.org/10.5194/egusphere-egu26-19123, 2026.

Metazoan reefs have experienced repeated crises throughout the Phanerozoic, marked by geologically rapid declines in reef carbonate production. While some of these crises coincided with major biotic turnovers, others left reef-building communities largely intact, and no simple relationship exists between crisis magnitude and ecological change. Consequently, the extent to which reef crises reshaped reef community composition and whether they triggered cascading extinctions among reef-dependent organisms remains unresolved.

Here, we use a global compilation of reef-related fossil occurrences over the Phanerozoic to test whether reef crises affected not only reef builders but also the wider marine biota. We distinguish three cohorts of reef affinity: (i) metazoan reef builders (i.e. colonial corals and sponges), (ii) reef dwellers, and (iii) non-reef organisms. By integrating these data with stage-level changes in reef volume, we evaluate extinction dynamics across four major Phanerozoic reef crises.

We find that reef builders and reef dwellers were tightly coupled over the last 500 million years. Although their background extinction patterns do not indicate simple, one-to-one cascading extinctions, extinction rates in both groups increased significantly during intervals of major reef loss. In contrast, non-reef organisms show no comparable response to reef crises. Our findings highlight the fundamental ecological interdependence between reef-building organisms and the diverse communities they support, and they underscore that the collapse of reef frameworks likely entails the loss of far more biodiversity than reef-building organisms alone.

How to cite: Dimitrijevic, D. and Kiessling, W.: Reef crises as an Earth-system driver of marine biodiversity loss, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19221, https://doi.org/10.5194/egusphere-egu26-19221, 2026.

Organisms whose activities impact the availability of resources in their environments, known as ecosystem engineers, are known to have profound controls on ecological and evolutionary dynamics throughout Earth history. Bioturbators – animals that mix seafloor sediments – are especially powerful ecosystem engineers due to their direct impacts on key benthic biogeochemical cycles. The emergence or loss of bioturbators throughout Earth history is associated with unique and profound shifts in benthic ecology and biogeochemistry. The end-Permian mass extinction (EPME), regarded as the most devastating climate-driven mass extinction in Earth history, saw devastating losses in marine benthic biodiversity and bioturbators, with the bioturbation-driven sedimentary mixed layer completely collapsing in some regions. The loss of bioturbating ecosystem engineers during the EPME has long been implicated in the rates of benthic recovery in the Early Triassic, although the precise impacts of bioturbator responses have remain unconstrained. Here, we test the hypothesis that loss of bioturbating ecosystem engineers during the EPME led to unique ecological and biogeochemical consequences in Early Triassic communities. Combining trace fossil data from literature and body fossil data from the Paleobiology Database for continuous stratigraphic sections across the EPME, we construct multiple comparative local time series of ecological responses of bioturbators and local benthic communities. We use the Earth system model cGENIE to reconstruct marine environmental conditions across the EPME, which also serve as boundary conditions for local biogeochemical models. For each region represented by continuous stratigraphic sections, we then use the fossil record to parameterise pre-EPME and post-EPME bioturbation in biogeochemical reactive-transport models and compare the impacts of the complete loss, reduction, or persistence of bioturbation on benthic biogeochemistry. Finally, we run local sensitivity analyses to constrain the impacts of bioturbation responses on biogeochemical change, and effect size analyses to quantify the relative roles of bioturbators and climate change on ecological responses across the EPME. These results address long-standing assumptions about the role of bioturbation in benthic ecosystem recovery through the Early Triassic and underscore the importance of local environments and community ecology for contextualising recovery in the aftermath of mass extinctions.

How to cite: Cribb, A., Sartin, A., Allen, B., Stokey, R., Monarrez, P., and Hulse, D.: Ecological and biogeochemical consequences of benthic ecosystem engineer responses to the end-Permian mass extinction  , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22916, https://doi.org/10.5194/egusphere-egu26-22916, 2026.

We argue that the habitability of terrestrial planets is linked to plate tectonics. We base our proposal on two premises.

First, in the absence of a robust magnetic field, a planet’s atmosphere is vulnerable to stripping by the solar wind, leading to catastrophic water loss and, ultimately, sterilization, as exemplified by modern Mars and Venus.

Second, a strong intrinsic planetary magnetic dipole must be generated by vigorous convection in the liquid core, which in turn requires efficient removal of heat from the core. On Earth, this heat removal occurs through the operation of plate tectonics.

The contrasting evolutionary paths of Earth, Venus, and Mars provide a natural laboratory for examining these relationships. Unlike Earth, both Mars and Venus lack plate tectonics and simultaneously lack a strong magnetic field. Venus currently operates in a stagnant-lid regime, in which heat loss occurs primarily by conduction across a thick lithosphere. This mode of heat transfer appears insufficient to sustain a core dynamo, resulting in the absence of a magnetic field and, consequently, in the loss of water and the development of an uninhabitable environment.

Another key “experiment” is recorded in Earth’s own history at the end of the Ediacaran period. This interval was preceded by approximately 1.5 billion years of a gradual decline in Earth’s dipole moment, from values comparable to the present field to a minimum that was roughly 30 times weaker. This minimum field strength persisted between 591 and 565 Ma, followed by a rapid threefold strengthening by about 532 Ma. Concurrently, atmospheric and oceanic oxygen levels began to rise, supporting an increase in the abundance and size of living organisms. These developments are commonly attributed to the formation of the inner core around ~550 Ma. However, both inner core growth and the associated intensification of the magnetic field would have been impossible without the simultaneous onset of plate tectonics. Thus, it was this tectonic regime change that enabled the rapid expansion of habitability at the Precambrian–Phanerozoic boundary.

We conclude that, although direct evidence remains limited, current scientific understanding strongly supports the notion that Earth’s long-term habitability is linked to the operation of plate tectonics, which sustains the geodynamo and protects the atmosphere from erosion by the solar wind. Nevertheless, the fundamental question of why Earth retained a functioning dynamo through plate tectonics, whereas Mars and Venus did not, remains an open problem for future investigation.

How to cite: Khazan, Y. and Aryasova, O.: Plate tectonics is crucial for habitability of terrestrial planets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3113, https://doi.org/10.5194/egusphere-egu26-3113, 2026.

JUICE (JUpiter ICy moons Explorer) is the first Large ESA mission in the Cosmic Vision Science program. JUICE was launched in 2023 and is aimed to study the Jupiter system in 2031-2035 where it will answer major science goals of the Jovian atmosphere and the Galilean satellites (Grasset et al., 2013). JANUS (Jovis, Amorum ac Natorum Undique Scrutator) is the high-resolution camera on JUICE and operates in the spectral range 340-1080 nm. The instrument is equipped with 13 filters and a detector of 1,504x2,000 pixels with a pixel FOV of 15 microrad and a total FOV of 1.29ºx1.72º (Palumbo et al. 2025).

JANUS imaged the Earth during and shortly after a Lunar and Earth Gravitational Assist maneuver (LEGA) on 19-20 August 2024. Earth observations offer a real testbed scenario to the science investigation of the Jovian atmosphere (Fletcher et al. 2023). Close approach observations were acquired at spatial resolutions of 126-256 m/pix and covered a narrow strip of the planet in which the spacecraft flew from the night-side over Madagascar, moved over the Indian Ocean, Cambodia and Vietnam and observed the terminator and dawn over Luzon Island. Later observations were acquired over morning to noon hours flying above tropical latitudes over the Western Pacific. Additional observations acquired on September 9, 2024 provided a low-resolution multi-filter portrait of the Earth and the Moon.

The high-resolution images contain atmospheric airglow, convective clouds illuminated by a full Moon, fires in rural areas, lights over the ocean from maritime traffic, city lights over Cambodia and Vietnam, and bright pixels compatible with meteoroids of 1-30 g entering Earth's atmosphere. Images over the terminator and dawn show crepuscular rays under extreme incidence angles with highly convective clouds projecting elongated shadows. Day-time observations show gravity waves on elevated cirrus clouds, sun glint on multi-filter images of the tropical Western Pacific, convective storms over tropical latitudes over the Northwest Pacific and internal waves in the ocean. We compared multi-filter images of the ocean and cloud systems over 12 filters through the JANUS spectral range with spectra obtained by the EnMAP and PRISMA instruments on Earth observing satellites showing good agreement.

These Earth images confirm the expected instrument performance and the ensemble of observations contains a large variety of atmospheric features that are good analogs to multiple systems in Jupiter's atmosphere (Hueso et al. 2026). Additional observations of the Earth will be acquired during the next two Earth flybys on September 2026 and January 2029 providing new data at a wider variety of spatial resolutions.

References

• Fletcher et al. Jupiter Science Enabled by ESA’s Jupiter Icy Moons Explorer, Space Science Reviews (2023).
• Grasset et al. JUpiter ICy moons Explorer (JUICE): An ESA mission to orbit Ganymede and to characterise the Jupiter system, Planet. and Space Sci. (2013).
• Hueso et al., JANUS observations of Earth in preparation for its investigation of Jupiter’s atmosphere, Annales Geophysicae, in preparation (2026).
• Palumbo et al. The JANUS (Jovis Amorum ac Natorum Undique Scrutator) VIS-NIR Multi-Band Imager for the JUICE Mission, Space Science Reviews (2025).

How to cite: Hueso, R., Palumbo, P., Tubiana, C., Portyankina, G., Lara, L. M., Stephan, K., Zinzi, A., Luchetti, A., Agostini, L., Penasa, L., Coustenis, A., Haruyama, J., Kersten, E., Matz, K.-D., Politti, R., Patel, M., Sato, M., Simon, A., Takahashi, Y., and Yair, Y. and the JANUS Earth flyby team: JANUS observations of the Earth during and shortly after JUICE’s Lunar and Earth Gravity Assist (LEGA) on August 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5763, https://doi.org/10.5194/egusphere-egu26-5763, 2026.

Earth's climate has changed in many ways over the past 4+ gigayears (Gyr), while mostly sustaining temperate conditions via volatile cycling.  This is remarkable given that the Sun's luminosity has changed by almost 30% in 4 Gyr.  The Earth's rotation rate has also changed by a factor of nearly 2 due to the receeding of the moon from Earth and changing bathymetry affecting tidal dissipation.  The climate of deep time future Earth (+1-3 Gyr) has seldom been explored, but one can use Earth's distant past to help inform us. The Sun's luminosity will continue to increase, while the moon's orbit will continue to grow affecting tidal dissipation in whatever bathymetry the Earth has in the future.  Using the ROCKE-3D climate model and VPlanet orbital dynamics components we attempt to model the future climate of Earth and how it might inform us about similar worlds orbiting nearby stars. For example, in one modeled dynamical scenario 1.9Gyr into the future the Earth's length of day (LoD) will increase to 46 days, while it's obliquity will approach zero. The global mean surface temperature (GMST) will only be 7.6C. If we choose a less dissipative scenario we find a LoD=1.5 days, an obliquity of 27.5, and a GMST=40C!  Will Earth eventually enter a moist and then a runaway greenhouse, or will it remain a temperate world until the Sun's red giant phase engulfs it in another 5 gigayears?  We will attempt to provide some answers to these questions.

How to cite: Way, M. and Barnes, R.: The Climate Evolution of Earth's Distant Future and implications for eta Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6124, https://doi.org/10.5194/egusphere-egu26-6124, 2026.

The toolkit of methods used in the search for life on other planets is growing vaster as research pushes new ways to examine the habitability of other planetary bodies. One method which can highlight the bioenergetic potential of our solar system involves thermodynamic calculations to estimate the Gibbs free energy produced by redox reactions. This method allows for predictions of the dominant biological reactions within environments such as Noachian-age martian hot springs and could be a useful indicator of habitability based on simple geochemical measurements capable by future Mars missions.

We utilise aqueous, gas and mineral measurements of key redox species within modern hot spring systems to predict the thermodynamic feasibility of chemolithoautotrophic metabolisms. These predictions are then compared to metagenomic and metatranscriptomic sequencing of these analogous microbial communities, to test the accuracy of Gibbs free energy calculations in predicting dominant redox metabolisms within primitive ecosystems. In addition, we model the outflow of these springs within a Noachian atmosphere to examine the differences in free energy availability and therefore dominant metabolisms compared to modern Earth systems.

Results reveal thermodynamically feasible carbon, iron and sulfur metabolisms and a ubiquitous reliance on biological fixation of inorganic N₂ and carbon within the hot spring communities. We find that the proportion of reduced and oxidised mineral iron in models impacts the feasibility of many redox reactions, including those which do not use iron species, suggesting that redox conditions are impacted by mineralogy. In addition, the free energy yield of redox reactions varies before and after equilibrating with mineral and atmospheric species, encompassing the natural chemical gradients within both modern hot springs and ancient systems on Mars.

Combining geochemical methods with genomic sequencing in this way allows for a true interdisciplinary assessment of free energy predictions and habitability of early Earth and Mars hot spring habitats.

How to cite: Galloway, T., Stüeken, E., Nixon, S., Telling, J., Nielson, G., Stead, C., Greco, C., and Cousins, C.: Thermodynamic predictions of redox metabolisms within Mars analogue hot springs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12339, https://doi.org/10.5194/egusphere-egu26-12339, 2026.

 Validated temporal gradient-driven gas migration on Earth as the primary mechanism for repeatable methane fluctuations on Mars.

By

Hovav Zafrir¹, Yuval Reuveni², Ayelet Benkovitz², Zeev Zalevsky¹, Elad Levintal³, Noam Weisbrod³,Danielle Ilzycer⁴

¹ Faculty of Engineering, Bar Ilan University, Ramat-Gan 5290002, Israel

²Department of Physics, Ariel University, Ariel 4070000, Israel

³The Jacob Blaustein Institutes for Desert Research, BGU University, of the Negev, Sede Boker, Israel

⁴Soreq NRC, Yavne, Israel

ABSTRACT

A significant observation by Curiosity’s Tunable Laser Spectrometer in Mars' Gale Crater involves repeatable methane fluctuations with distinct seasonal and sub-diurnal variability. After a decade of data, these methane emissions clearly require robust geophysical explanations rooted in thermodynamics.

On Earth, extensive field and laboratory research have demonstrated that surface temperature gradients primarily drive subsurface gas flows, particularly those of Radon-222. This thermally induced transport exhibits an exponential dependence, verified through long-term field measurements (4 years (*)) and also in controlled laboratory conditions, where oscillating vertical gas flow closely matches surface heating cycles, from the natural one per day to one per eight days. The field monitoring has shown that radon gas flows downward throughout all daylight hours within the bedrock to a measured depth of 100 meters and responds inversely to atmospheric temperatures at night, creating an inverted surface temperature gradient that drives nocturnal exhalation.

While gases on Earth's ground also respond linearly to semi-diurnal barometric pressure changes (barometric pumping), within cracks, voids, or fractures between geological layers and structures, our experience indicates that such effects become negligible when the pressure gradient is less than 2 millibars. Specifically, on Mars, where barometric pressure is two orders of magnitude lower than Earth's, the resulting pressure gradient is insufficient to drive significant gas transport, even through sand on Earth's surface.

^(*) Benkovitz et al., 2023, https://doi.org/10.3390/rs15164094. Zafrir, et al., 2016, https://doi. org/10.1002/2016JB013033.

How to cite: Zafrir, Dr. H., Reuveni, Y., Benkovitz, A., Zalevsky, Z., Levintal, E., Weisbrod, N., and Ilzycer, D.: Validated temporal gradient-driven gas migration on Earth as the primary mechanism for repeatable methane fluctuations on Mars., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14723, https://doi.org/10.5194/egusphere-egu26-14723, 2026.

Impact events represent the most energetic processes during late-stage terrestrial planet accretion and generate large amounts of debris that can be redistributed throughout the inner Solar System. The long-term dynamical fate of this impact-generated material plays a key role in regulating planetary growth, cross-planet mass exchange, and material loss from the system. However, most N-body accretion models still rely on simplified collision prescriptions that neglect the detailed structure and dynamics of impact remnants.

In this study, we investigate the long-term evolution and final fate of impact-induced debris by coupling high-resolution Smoothed Particle Hydrodynamics (SPH) simulations with GPU-accelerated N-body integrations. We perform a systematic suite of SPH simulations spanning a broad parameter space in impactor mass, impact velocity, and impact angle. Gravitationally bound clumps (GBCs) formed in the impact aftermath are identified using an energy-based clustering algorithm and mapped self-consistently into N-body initial conditions, which are then evolved for 15 Myr using the GENGA integrator in a realistic inner Solar System configuration.

Our simulations reveal a two-stage debris clearance process. More than 80% of the ultimately accreted mass is reaccreted within the first 10⁵ years after impact, followed by a prolonged phase of dynamical depletion dominated by planetary perturbations. Earth is the primary sink of impact debris, reaccreting on average ∼40% of the total fragment mass, while Venus acts as a significant secondary reservoir, capturing ∼18-27%. In contrast, Mercury and Mars contribute only marginally to debris accretion. Approximately 25-30% of the debris is ultimately ejected from the Solar System, primarily through gravitational scattering by Jupiter.

Statistical analysis demonstrates that impact angle and velocity are the dominant parameters controlling debris fate, with high-velocity and grazing impacts strongly enhancing mass loss via ejection. Initial orbital phase also modulates debris survival and reaccretion efficiency. These results provide quantitative constraints on post-impact mass redistribution and highlight the importance of explicitly resolving impact remnants when modeling late-stage terrestrial planet formation.

How to cite: Duan, R.: N-body simulations to track the long-term fate of impact–induced debris, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16133, https://doi.org/10.5194/egusphere-egu26-16133, 2026.

Earth is the best-constrained planetary body, yet many Earth-system challenges still require remote-sensing workflows that remain robust under incomplete ground truth, multi-sensor heterogeneity, and complex observation geometries. Planetary science has long operated under these constraints, developing interpretation strategies and processing practices that are increasingly relevant for Earth Observation (EO) applications in hazard monitoring, environmental change, and geological process understanding. In line with the PS1.3 scope of transferring planetary-science methodologies to advance Earth-system knowledge, we present an education-driven framework designed to operationalise this methodological transfer at MSc level.
We describe the structure and rationale of a new Earth Observation curriculum embedded within an MSc in Planetary Sciences, conceived as an “educational pipeline” that trains students to move from sensor-aware analysis to geology-driven interpretation and application-ready products. The curriculum integrates core modules on Earth Observation analysis, satellite multi/hyperspectral data analysis, and geospatial technologies, followed by geology-centred Earth-system applications (e.g., sedimentary environments, marine geology, global changes) and applied EO modules targeting volcanic monitoring and tectonic deformation. A distinctive component is digital field mapping with emerging technologies, designed to explicitly link remote-sensing products to validation strategies and field-based geological reasoning. The training pathway is reinforced through institutional collaboration with national agencies and research bodies, enabling exposure to operational practices and real-world constraints.
We argue that the key innovation lies in implementing a reproducible planetary-to-Earth methodological transfer framework based on: (i) observation-geometry and uncertainty-aware processing, (ii) scalable multi-sensor analytics, (iii) process-based geological interpretation, and (iv) field-connected validation and mapping. By framing education as a mechanism for transferring robust planetary methodologies into EO practice, this approach contributes to bridging planetary and Earth-system sciences while producing graduates capable of translating EO data into reliable, decision-relevant geoscience knowledge.

Keywords: comparative planetology; Earth Observation; remote sensing; hyperspectral; GIS/geoprocessing; hazards; digital field mapping. 

How to cite: Pondrelli, M., Salese, F., Coletta, A., Flamini, E., Mancini, F., Pace, B., Iezzi, G., Satolli, S., Vessia, G., Boncio, P., and Ori, G. G.: Education as a transfer mechanism: translating planetary remote sensing methodologies into operational Earth Observation for Earth-system applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20005, https://doi.org/10.5194/egusphere-egu26-20005, 2026.

Venus hosts hundreds of enigmatic circular tectono-magmatic features known as coronae, whose origins, activity state, and role in planetary heat loss remain among the most persistent open questions in Earth and planetary sciences. Coronae display extraordinary diversity in size, morphology, topography, gravity signatures, and tectonic setting, indicating that they do not represent a single formation mechanism, but instead reflect a spectrum of dynamic processes. Understanding these structures is critical not only for deciphering Venus’ geodynamic regime, but also for assessing whether similar processes may have operated on the early Earth before, or during, the onset of sustained plate tectonics.

Here, we present new insights into the coronae enigma by integrating results from a newly compiled global corona database with joint analysis of topography and gravity observations, complemented by recent three-dimensional thermo-chemical geodynamic modeling. The updated database includes 741 coronae, substantially more than previously catalogued features, enabling a more accurate global-scale statistical assessment of coronae morphology, geological setting, and spatial distribution. The expanded dataset reveals numerous corona(-like) structures not previously recognized and highlights systematic variations in corona expression across different tectonic environments.

We investigate the topography and gravity signatures of the largest coronae using Magellan datasets. By analyzing free-air gravity anomalies together with key topographic characteristics, we identify distinct classes of coronae that exhibit signatures consistent with buoyant mantle support and different styles of plume–lithosphere interaction, including scenarios in which crust is recycled back into the mantle through lithospheric delamination or subduction-like processes. Importantly, our analysis further reveals that the limited spatial resolution of the Magellan gravity field can obscure or suppress positive gravity anomalies beneath some coronae, particularly where deep annular troughs surround an uplifted interior. This suggests that a subset of potentially active coronae could be effectively “hidden” in current geophysical datasets. These coronae therefore represent key observables for forthcoming missions such as ESA's EnVision and NASA's VERITAS.

Finally, we explore how corona-formation models are relevant to early Earth evolution.  These results provide a framework for evaluating plume-induced lithospheric weakening and transient subduction-like behavior as key mechanisms for the onset of plate tectonics on our planet.

How to cite: Gülcher, A.: Venus: The Coronae Enigma and Lessons for Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20108, https://doi.org/10.5194/egusphere-egu26-20108, 2026.

Radar remote sensing is essential for investigating Venus’ surface due to its dense CO₂-rich atmosphere and permanent cloud cover. The forthcoming ESA EnVision mission, equipped with the S-band VenSAR instrument operating in dual polarimetric HH and HV modes, will provide high-resolution observations to characterise surface scattering mechanisms, surface roughness, and dielectric properties. These observations are expected to enable the identification of signatures associated with active volcanic processes, including recent lava flow emplacement and surface alteration driven by thermal and chemical weathering. However, interpretation of polarimetric SAR observations over volcanic terrains remains challenging due to strong surface roughness, structural anisotropy, and orientation angle-induced depolarisation effects. Terrestrial volcanic analogues therefore provide a suitable framework for the development and validation of physically consistent polarimetric models prior to the availability of VenSAR data. This study presents a technical analysis of polarimetric scattering mechanisms at the Sundhnúksgígar and Holuhraun volcanic sites in Iceland using dual and full polarimetric ALOS-PALSAR-2 L-band SAR datasets. Fully polarimetric observations are used to quantify dominant scattering contributions and to evaluate the performance of conventional model-based decomposition approaches, including Freeman-Durden and Yamaguchi decomposition, over rough and structurally complex lava surfaces. To address the systematic overestimation of volume scattering, which can cause rough aa lava flows to be misclassified as vegetation, a modified model-based decomposition technique is introduced. By redistributing cross-polarised backscatter as a function of surface roughness, the proposed approach improves the separation of scattering mechanisms and enables more accurate discrimination of lava flow units and volcanic surface textures across both study areas. In addition, a dual polarimetric analogue of the proposed model-based decomposition technique is developed to enable volcanic surface characterisation using reduced polarimetric configurations consistent with the EnVision VenSAR acquisition mode. Multi-temporal ALOS PALSAR 2 dual polarimetric acquisitions are analysed to investigate surface evolution and volcanic dynamics associated with lava emplacement, flow cooling, and post-eruptive surface modification at the Sundhnúksgígar volcano site. The dual polarimetric formulation demonstrates strong correspondence with full polarimetric results in terms of dominant scattering behaviour and spatial variability, supporting the applicability of the proposed framework for future Venus observations. These results provide a validated polarimetric approach for characterising volcanic surfaces and contribute directly to the scientific preparation and exploitation of EnVision VenSAR data.

Keywords: Volcanos; SAR Polarimetry; Polarimetric SAR Decomposition; EnVision; ALOS-PALSAR-2; VenSAR

How to cite: Awasthi, S., Gao, Y., Gallardo i Peres, G., Davidova, N., C. Ghail, R., and Mason, P. J.: Polarimetric Characterisation of Volcanic Surfaces Using Dual and Full Polarimetric Spaceborne SAR Datasets: Analogue Studies for the Venus’s EnVision Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20877, https://doi.org/10.5194/egusphere-egu26-20877, 2026.

Faults provide key evidence for a planet’s tectonic history, especially where direct geophysical data are scarce. Fault geometry analysis is essential for understanding tectonic deformation [1] and seismic potential [2]. Thorough fault geometry analysis constraints fault evolution mechanical response [3,4]. Marsquakes at Cerberus Fossae, Mars [5] which were detected by InSight mission’s seismometer renewed interest in Martian tectonics, and underscored the significance of extensional fault systems. Memnonia Fossae is a region hosting prominent extensional structures similar to Cerberus Fossae. Yet, these structures in Memnonia Fossae are much older than the ones in Cerberus Fossae, which provides a valuable opportunity to explore the long-term evolution of fault systems on Mars. However, due to the challenges in obtaining high-resolution topographic data [6], fault geometry studies on Mars are still limited. Therefore, to address this limitation, we use the Reykjanes Peninsula in Iceland as a terrestrial analogue, where active tectonic processes in basaltic terrains reflects those believed to occur on Mars. The objective of this study is to evaluate and compare the geometric properties and scaling relationships of normal faults in Memnonia Fossae region on Mars and Reykjanes Peninsula in Iceland, providing insights into fault growth mechanisms at a planetary scale.

Previously, we obtained a maximum displacement-to-length (D_max/L) ratio of 0.007 by analyzing fault scaling in Memnonia Fossae using remote sensing data from 100 faults. In this study, we focused on the Reykjanes Peninsula, and we collected structural measurements from 74 faults and fractures across 180 locations, recording parameters such as strike, dip, opening throw, shear, and extension vectors. Alongside field measurements, the Arctic DEM and drone imagery were employed also for less accessible faults.  The integration of field measurements, remote sensing, and drone imagery enabled a detailed characterization of fault geometry and displacement. The D_max/L ratio derived from Reykjanes peninsula was 0.006, closely corresponding to values derived for Memnonia Fossae and aligning with fault scaling observation in volcanic terrains on Earth. The observed similarities between faults in Reykjanes and Memnonia Fossae indicate that comparable fault growth processes may operate in both regions despite differences in age and origin. Reykjanes faults are part of an active plate-boundary rift zone on Earth, whereas Memnonia faults formed in the ancient crust of a single-plate planet. Comparing older and younger faults offer insights into the tectonic evolution of Mars and demonstrates the value of Earth-based multi-source datasets in planetary studies.

Figure 1: Dmax/L ratio comparisons of Memnonia Fossae, Reykjanes, and volcanic rocks on Earth [7].

[1] Schultz, R.A. et al. (2010) J. Struct. Geol., 32, 855-875. [2] Wells, D.L. and Coppersmith, K.J. (1994) Bull. Seismol. Soc. Amer., 84, 974-1002. [3] Cartwright, J. A., et al., (1995) J. Struct. Geol. 17, 1319-1326. [4] Cowie, P.A. and Scholz, C.H., (1992) J. Struct. Geol. 14, 1133-1148. [5] Drilleau, M., et al., (2021) EGU General Assembly. Conf. 14998. [6] Gwinner, K. et al., (2010) Earth Planet. Sci. Lett. 294, 506-519. [7] Lathrop, B. A., et al., (2022) Frontiers in Earth Science, 10, 907543.

How to cite: Yazıcı, I. S., Kenkmann, T., Sturm, S., Karagoz, O., Hauber, E., and Tirsch, D.: From Iceland to Mars: Fault Scaling and Tectonic Insights from an Earth Analogue, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21129, https://doi.org/10.5194/egusphere-egu26-21129, 2026.

The physical behaviour of silicate magmas and their eruptive style are strongly controlled by melt structure, volatile content, and cooling conditions, reflected in spectral properties. Magma rheology and eruptive style are primarily controlled by volatile-driven modifications of melt structure (especially due to H₂O), which govern fragmentation during magma–water interactions, producing fine, lithic-rich tephra. Spectroscopic techniques provide a powerful means to investigate melt structure and pre-eruptive volatile contents, offering insights into eruption dynamics.
We analysed tephra samples from two phreatomagmatic successions on Vulcano Island (Aeolian Arc, Italy), a natural laboratory to investigate relationships among magma composition, volatile content, and eruption style (Keller, 1980; De Astis et al., 1997). Eleven ash-rich layers were sampled. Field measurements included VNIR reflectance spectra acquired with an ASD FieldSpec spectroradiometer and portable Raman spectroscopy. Diffuse reflectance FTIR spectra were collected using a Bruker Invenio X spectrometer on natural and oven-dried samples (105 °C, 48 h) to evaluate adsorbed water. Quantitative spectral parameters were extracted, including band center, full width at half maximum, and area under the curve in the 300–25000 nm domain. We investigate whether VNIR reflectance spectroscopy and laboratory FTIR measurements can identify spectral criteria diagnostic of eruption style in surge-dominated pyroclastic deposits. Preliminary analyses reveal systematic spectral variations related to volatile content and silicate melt structure. The spectra display absorption features attributed to Fe³⁺, molecular H₂O, OH⁻, Al–OH, and Fe–OH vibrations, enabling extraction of band parameters sensitive to hydration state and polymerization degree. Thermal treatment experiments show reduced band areas and spectral slope associated with H₂O and OH⁻ absorptions after heating, indicating that most water in natural samples is weakly bound or adsorbed. However, water loss varies among stratigraphic levels, reflecting differences in glass content, porosity, and hydration history. Variations in Si–O and Al–O band positions and widths indicate differences in silicate network polymerization, with narrower bands and shifts toward higher wavenumbers consistent with evolved compositions. Overall, the spectral signatures are consistent with highly explosive eruptions involving water-rich, evolved magmas and record internal heterogeneity within the eruptive column, marked by progressive degassing during the eruptive event.
This study contributes to the development of spectral reference datasets of terrestrial volcanic materials, essential for interpreting remote sensing data. By linking spectral features to the physical and chemical characteristics of volcanic deposits and their eruptive context, we constrain the nature of volcanic activity on other planetary bodies.

De Astis, G.F. et al., 1997. Volcanological and petrological evolution of the Vulcano Is land Aeolian arc, southern Tyrrhenian Sea. J. Geophys. Res. 102, 8021–8050.
Keller, J., The island of Vulcano, Rend. Soc. Ital. Mineral. Petrogr., 36, 369–414, 1980

How to cite: Gentili, C., Tiraboschi, C., Pisello, A., Baroni, M., Ortenzi, G., Baqué, M., Bohnhardt, T., and Perugini, D.: From terrestrial volcanic ashes to planetary surfaces:FTIR spectral constraints on eruption style from surge deposits from Vulcano Island (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21130, https://doi.org/10.5194/egusphere-egu26-21130, 2026.

This study developed and applied an integrated framework to analyse surface mineralogical variability and radar backscatter response in Mawrth Vallis, Mars. The primary goals were to evaluate the lateral extent and potential subsurface continuity of phyllosilicate-bearing layers, and discussing the benefits, limitations and improvements for this approach. The methodology combined HRSC imagery, both color mosaics and digital terrain models to map four distinct surface units (S1, S2, S3, and DT) based on hue, brightness patterns, and topographic context. This was complemented by OMEGA and CRISM HSP hyperspectral data to characterize the regional distribution and composition of hydrated mineral phases, specifically Fe/Mg- and Al-phyllosilicates. Finally, SHARAD radargrams were used to identify clutter patterns, possible subsurface reflectors, and to analyse radar backscatter variations across the mapped surface units.

Spectral analysis confirmed that surface units mostly but not completely match the compositional boundaries, with S2 consistently shows dominant Fe/Mg-smectite absorptions, S1 exhibits Al-smectite features in a mixed spectrum, and S3 is characterized by dominant kaolinite absorptions. While these mineralogical variations generally align with the mapped surface units, small-scale heterogeneities suggest a finer stratification that is not fully resolved at the current data resolution.

SHARAD radargrams revealed variations in radar backscatter that are dependent on surface unit type. The DT unit consistently produces strong surface echoes, even in areas with similar terrain characteristics, which points to variations in the dielectric properties of the materials. In contrast, S2 returns weaker radar signals, consistent with the relatively lower dielectric constant of Fe-smectite. S1 exhibit intermediate radar responses. Additionally, potential subsurface reflectors were identified beneath the DT-S3 interface along Mawrth Vallis' southern flank, which may represent preserved stratigraphic interfaces, likely due to dielectric contrasts between the regolith-like DT material and the kaolinite-rich S3 unit.

This integrated approach highlights both the synergies and challenges of using multiple datasets for interpretation. Spectral data are effective for constraining surface composition but lack the ability to probe depth, while radar instruments can detect subsurface structures but struggle with thin layering and strong clutter patterns.

How to cite: Larrota, D., Bakker, W., and van Ruitenbeek, F.: Integration of Spectral Datasets and Radargrams in Mawrth Vallis, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-311, https://doi.org/10.5194/egusphere-egu26-311, 2026.

How to cite: Whorton, J., Jones, T. J., Wilson, L., and Pieterek, B.: Mudflow rheology under disequilibrium conditions: implications for the interpretation of Martian flow deposits, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-656, https://doi.org/10.5194/egusphere-egu26-656, 2026.

Before NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft entered Mars’ orbit in 2014, meteoric metals had not been directly measured in a planetary atmosphere beyond Earth. MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) has since measured a persistent layer of Mg⁺ in the Martian upper atmosphere. Metal species are injected into the atmosphere via ablation at altitudes where the pressure is ~1 μbar; the peak of the Mg⁺ layer varies over the Martian year due to changes in atmospheric density caused by the deposition and sublimation of CO₂ at the poles. During Mars’ close encounter with the Oort cloud comet, Siding Spring, in October 2014, the IUVS instrument could also observe Mg, Fe, and Fe⁺. Neutral Mg was observed to decay at rates much faster than predicted and global models simulate nominal densities above the detection limit of the IUVS instrument, suggesting an incomplete understanding of Mg chemistry. The MAVEN mission included nine ‘Deep Dip’ campaigns, during which the nominal altitude range of the spacecraft was extended to include altitudes as low as 125 km. These week-long campaigns were designed to sample a variety of locations, local times, and solar longitudes, and offered the unique opportunity to measure Mg⁺, Fe⁺, and Na⁺ in-situ with the Neutral Gas and Ion Mass Spectrometer (NGIMS).

This study investigates the variability of Mars’ meteoric metal layers by comparing MAVEN IUVS and NGIMS observations with PCM-Mars simulations of the deep dip campaigns and the passing of Siding Spring. The PCM-Mars is a 3D numerical model of the Martian atmosphere, simulating atmospheric chemistry, circulation, temperature, and dust from the surface to the exobase. For the deep dip simulations, the Leeds Chemical Ablation Model (CABMOD) and the Meteoric Input Function (MIF) of Carrillo-Sánchez et al. (2022) were used to model the injection of MgO, Mg⁺, Fe, Fe⁺, Na, Na⁺, SiO, and Si⁺; we implemented a Siding Spring MIF to investigate the missing neutral Mg. For all simulations we have implemented a 4-metal chemistry scheme modelling Mg, Fe, Na, and Si reactions. This intercomparison of MAVEN observations and PCM-Mars simulations is vital to constraining global models and understanding the key drivers controlling the variability of Mars’ metal layers.

References

Crismani, M.M.J., Schneider, N.M., Plane, J.M.C., Evans, J.S., Jain, S.K., Chaffin, M.S., Carrillo- Sánchez, J. D., Deighan, J.I., Yelle, R.V., Stewart, A.I.F., McClintock, W., Clarke, J., Holsclaw, G.M., Stiepen, A., Montmessin, F., and Jakosky, B.M. Detection of a persistent meteoric metal layer in the Martian atmosphere, Nat. Geosci., 10(6): 401-405, doi:10.1038/ngeo2958, 2017.

Crismani, M.M.J., Schneider, N.M., Evans, J.S., Plane, J.M.C, Carrillo-Sánchez, J. D, Jain, S.K., Deighan, J.I., and Yelle, R.V. The Impact of Comet Siding Spring’s Meteors on the Martian Atmosphere and Ionosphere, JGR. Planets., 123(10): 2613-2627, doi:10.1029/2018JE005750, 2018.

Carrillo-Sánchez, J. D., Janches, D., Plane, J.M.C., Pokorný, P., Sarantos, M., Crismani, M.M.J., Feng, W., and Marsh, D.R. A Modeling Study of the Seasonal, Latitudinal, and Temporal Distribution of the Meteoroid Mass Input at Mars: Constraining the Deposition of Meteoric Ablated Metals in the Upper Atmosphere, Planet. Sci. J., 3(10), art. no. 239, doi:10.3847/PSJ/ac8540, 2022.

How to cite: Gough, C., Marsh, D., Plane, J., Feng, W., Carrillo-Sánchez, J. D., Janches, D., Crismani, M., Poppe, A., Schneider, N., Benna, M., González-Galindo, F., Chaufray, J.-Y., and Forget, F.: Martian Meteoric Metals: An intercomparison of MAVEN Observations and PCM-Mars Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-912, https://doi.org/10.5194/egusphere-egu26-912, 2026.

Early Mars exhibited terrestrial-like hydrologic activity, with extensive fluvial networks and lacustrine deposits preserved due to the lack of plate tectonism. Ma’adim Vallis (≈22°S, 177.3°E) in Terra Cimmeria extends ~900 km, is 10–15 km in width, and reaches depths of ~2 km, linking the Eridania basin system to Gusev crater on the northern plain. The competing formation hypothesis involves surface runoff, paleolake overflow, and dry volcanic megafloods. This work employs high-resolution orbital imageries like CTX, HiRISE, CRISM, and Digital Elevation Models to quantify more than 50 morphometric parameters, including length-area scaling, sinuosity indices, dissection indices, and junction angles for channels, etc. Mineralogical mapping identifies key minerals, including Mg-smectite, Fe/Mg phyllosilicates, and olivine from the study area. Even though the integrated morphometric and mineralogical evidence points to a dominantly catastrophic water outflow event that carved the valley, implying a transient but intense hydrologic regime in Mars’ early climate history; evidence suggests that the evolution of Ma’adim Vallis may not be derived from a single process, indicating the involvement of multiple, distinct formative mechanisms.

How to cite: Ebrahim, S., Porwal, A., and Mullassery, N.: A comprehensive morphometric and mineralogical assessment of Ma’adim Vallis, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1024, https://doi.org/10.5194/egusphere-egu26-1024, 2026.

Lyot (50.8°N, 330.7°W), the largest and deepest impact structure on the northern plains of Mars, with an approximate diameter of 220 km, is a prominent peak-ring crater situated near the hemispheric dichotomy within the Vastitas Borealis region. This Amazonian-aged crater has long fascinated due to its potential association with past hydrologic activity. Previous studies have suggested that the Lyot impact may have breached the cryosphere, enabling the release or exposure of subsurface groundwater. As a result, the crater interior and its surroundings preserve geomorphic signatures of both ancient and relatively recent water-related processes, including groundwater upwelling as well as atmospheric precipitation.

The primary objective of this study is to systematically map and characterize the major morphological features and mineral assemblages within Lyot Crater to better understand its hydrologic and climatic evolution. For this purpose, we employ a multi-instrument dataset comprising MOLA blended DEM for topographic analysis, Context Camera (CTX) imagery (5–6 m/pixel) for regional geomorphologic mapping, and select high-resolution HiRISE images (25–30 cm/pixel) for detailed surface feature interpretation. Mineralogical information is derived from CRISM observations (18 m/pixel), enabling the detection of key alteration minerals. Our geomorphic analysis identifies a diverse suite of features including fluvial channels, distal ridges, glacial and periglacial landforms, and multiple dune fields. Spectral analysis reveals the presence of Fe/Mg-smectites, chlorites, illite/muscovite, prehnite, and other hydrated minerals distributed across the central peak ring, crater floor, and rim. Together, these features and mineral signatures highlight the complex interplay of fluvial, glacial-periglacial, and aeolian processes that have shaped Lyot over time. While hydrous minerals and water-related landforms provide important clues to subsurface water activity and Mars’ broader hydrologic evolution, the aeolian deposits record more recent atmospheric dynamics and ongoing topographic changes. Overall, this integrated investigation enhances our understanding of Lyot Crater as a key site for reconstructing Amazonian-era water activity and climate transitions on Mars.

How to cite: Mullassery, N. and Ebrahim, S.: Deciphering Water and Climate History in Lyot Crater, Mars: A Morphological and Mineralogical Perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1160, https://doi.org/10.5194/egusphere-egu26-1160, 2026.

Rio Tinto and Odiel are part of the fluvial system of the Iberian Pyritic Belt (IPB), so far the largest massive sulfide deposits found on continental crust on Earth. The extreme geochemical characteristics of Rio Tinto revealed this area as one of the most important geochemical Mars analogues on Earth. Its exotic mineralogy provides a good environmental analog for Hesperian/Teiikian mineral deposits on Mars, [1, 2, 3], and thanks to that, it is a unique place for developing and testing instruments for future planetary missions. Robotic vehicles and the recent technological demonstration of Ingenuity on Mars open up the possibility of using the powerful and non-destructive geophysical tool of magnetic surveys at different heights, for the investigation of surfaces and subsurfaces of planetary bodies. We explore IPB area Odiel-San Platón, were both jarosite (a key mineral from the Teiikian era of Mars) and important outcrops of Manganiferous Formation of the IPB are accessible. Manganese is a key element to support a putative microbial metabolism on Mars, but both acidic alteration of the rocks in this area and the low magnetic signal of manganese rich minerals, make the magnetic signature of the rocks, a challenge to be detected. We identify manganese-rich areas and minerals thanks to its magnetic signal, both in the field and with a detailed magnetic characterization of rock samples using a Vibrating Sample Magnetometer. In this research, we have done a magnetic survey and taken geological samples in field campaigns in 2018 and 2025. We propose a methodology which comprises an analysis of the morphology using images, magnetic field surveys, rock sample magnetic characterization, and simplified models for the interpretation of geological structures on the field. This methodology is applied successfully to the study of different areas of the Iberian Pyritic Belt, representative of the Martian landing sites mineralogy, as a preparatory action prior to the exploration of the planetary bodies’ surfaces.

How to cite: Díaz-Michelena, M., Velasco Domínguez, E., Melguizo Baena, Á., Cortés Mañanes, A., Rivero Rodríguez, M. Á., López Escolano, A., and Fernández Romero, S.: Magnetic survey in Rio Tinto area: a Mars analogue., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1716, https://doi.org/10.5194/egusphere-egu26-1716, 2026.

Mars lacks a global dipole magnetic field but hosts localized magnetic anomalies from magnetized crustal rocks. Accurate descriptions of the crustal magnetic field are crucial for understanding the magnetic environment and geology of Mars. In this study, We construct a Martian crustal magnetic field model using the Equivalent Source Dipole (ESD) approach, integrating data from three missions: Mars Global Surveyor (MGS), Mars Atmosphere and Volatile EvolutioN (MAVEN), and Tianwen-1. To mitigate contamination from solar wind-ionosphere interactions, we use satellite-measured upstream solar wind parameters, including the average values of IMF strength, IMF fluctuation levels, solar wind pressure, and electron density, as indicators of external field interference. The resulting model is then converted to a spherical harmonic (SH) model up to degree 130, achieving a spatial resolution of approximately 165 km at the Martian surface. Compared to previous studies, it exhibits reduced fitting residuals for the horizontal components of MAVEN dataset, confirming the effectiveness of our data selection methodology. Validation with rover measurements reveals that while the model’s predictions are significantly weaker at the InSight landing site, they show better agreement with observations at the Zhurong site than those of previous models. This work could assist in further research on the Martian magnetic environment and its interaction with the solar wind.

How to cite: Wanqiu, F., Long, C., Yuming, W., Zhenguang, H., and Rentong, L.: A Model of the Martian Crustal Magnetic Field Using Data from MGS, MAVEN, and Tianwen-1, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3633, https://doi.org/10.5194/egusphere-egu26-3633, 2026.

The Visual Monitoring Camera on board Mars Express provides images of varied resolutions, covering a wide range of locations and seasons, and has been taking images for several Martian Years. Some of these images show clear instances of aerosols layers in the limb of the planet, which allow studying their height and extension. Images close to pericenter display varying morphologies, and the extensive coverage by VMC allows determining inter-annual and areographicaI variations in occurrence.

The first years of the database were explored in Sánchez-Lavega (2018a), but this study was conditioned by the fact that there was no scientific programming of the observations until 2016. Nowadays, after several years of planning, a much more complete set of observations is available, covering four Martian years, with the added interest that a global dust storm developed in one of them (Sanchez-Lavega et al, 2018b). In this work, we will present results of a systematic analysis that aims to extend this study to MYs 33-37, measuring the extension and height of aerosols, their aerographic distribution and dependence on season and local time. We also contextualize our results using values of dust and water opacity retrieved by the Mars Climate Sounder onboard the Mars Reconnaissnce Orbiter and the estimates of the Mars Climate Database of the Laboratoire de Météorologie Dynamique.

References:

• Sánchez-Lavega, A. et al. “Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express” ICARUS 299, 194-205 (2018a)
• Sánchez-Lavega, et al. “The Onset and Growth of the 2018 Martian Global Dust Storm” Geophysical Research Letters, 46, 6101-6108 (2018b)

How to cite: del Río-Gaztelurrutia, T., Sanz Hernández, T., Sánchez-Lavega, A., and Hernandez-Bernal, J.: Aerosols and clouds in the limb of Mars: A study with the VMC camera onboard Mars Express, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4041, https://doi.org/10.5194/egusphere-egu26-4041, 2026.

Bright basal reflections detected on Mars by radar sounder MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) have been interpreted to indicate the presence of liquid perchlorate brines [1-2] in Ultimi Scopuli (193°E; 81°S) a marginal area of the South Polar Layered Deposits (SPLD). This is the first (and only) report of extant bodies of liquid water on Mars, although this interpretation is not universally accepted. Other authors have suggested that the bright reflections may be caused by clays [3], hydrated salts [4], basalt [5], or that they are produced by constructive interference of radar waves [6-7]. These alternatives to the liquid brine interpretation have been investigated and found to be implausible [8-11].

We are not yet close to a definitive explanation of the mechanisms of formation and persistence of liquid brines in the Martian south polar regions, however. Even though basal temperatures could conservatively be estimated to be as high as 193 K [12], a value close to the eutectic temperature of Ca-perchlorate (198.5 K; [13]), the commonly accepted tenet that the south polar region of Mars is too cold for the presence of large bodies of liquid water [14] has not shifted. Liquid brines could form metastably at sub-eutectic temperatures, but it is not clear whether they could persist over geologically significant timescales [15]. Recent geophysical and petrological evidence points to a heterogeneous Martian interior and suggests the possibility of higher heat flows than previous estimates [16-17], but these results have not translated into recalculations of SPLD basal temperatures. The presence of chemical species that could act as antifreeze (such as ammonia or methanol; [18]) or of clathrate hydrates [19] has been proposed, but not yet adequately modeled because of lack of data.

Stimulated by the complexity and current paucity of geophysical evidence to progress further, we reframe the problem from a cosmochemical perspective: if briny oceans exist beneath the frozen crust of small planetary bodies in the outer solar system, under what circumstances could small and contained bodies of subglacial liquid water exist on Mars? Here, we consider data and models of:  solar system formation;  element condensation temperatures;  relationship between planetary noon temperature, gravity, and atmospheric composition; Mars’s volatile budget; chemical reaction cycles in the Martian atmosphere; atmosphere-lithosphere processes. We identify current gaps in data, and highlight future work to fill the gaps.

References. [1]10.1126/science.aar7268. [2]10.1038/s41550-020-1200-6. [3]10.1029/2021GL093618. [4]10.1029/2021GL093880. [5]10.1029/2021GL096518. [6]10.1038/s41550-022-01775-z. [7]10.1126/sciadv.adj9546. [8]10.1016/j.epsl.2022.117370. [9]10.1016/j.icarus.2022.115163. [10]10.1029/2022JE007398. [11]10.1029/2022JE007513. [12]10.1038/s41467-022-33389-4. [13]10.1007/s11167-005-0306-z. [14]10.1029/2020GL091409. [15]10.1073/pnas.2321067121. [16]10.1016/bs.agph.2022.07.005. [17]10.1029/2023GL103537. [18]10.1089/ast.2024.0075. [19]10.1002/2014RG000463.

How to cite: Caprarelli, G., Mills, F. P., and Orosei, R.: Ocean worlds and Mars: A cosmochemical perspective on the liquid brines "problem", EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4366, https://doi.org/10.5194/egusphere-egu26-4366, 2026.

Valley networks and wrinkle ridges are commonly observed in the Martian highlands. Geologic cross-cutting relationships between fluvial and tectonic features provide constraints on their formation sequences and the spatiotemporal evolution of these processes. For example, in central Terra Sabaea, a valley network appears to be affected by a wrinkle ridge. Tributaries are diverted along the ridge front and converge into a single, elevated channel across the ridge, suggesting coevolution between fluvial erosion and wrinkle ridge development. In this work, we systematically examine all intersections between valley networks and wrinkle ridges across the Martian highlands, assessing the relative timing and activity of tectonics and fluvial erosion. We identify 70 intersection sites from previously mapped valley networks and wrinkle ridges. Among them, ~60% exhibit syn- to post-fluvial tectonic modification, as indicated by drainage reorganization and valley profile changes; ~30% record pre-fluvial tectonic activity, and only ~7% show purely post-fluvial tectonic activity. Longitudinal profiles from six syn- to post-fluvial tectonic sites indicate that tectonic uplift produced comparable amounts of deformation during syn-fluvial and post-fluvial periods, with one exception. Erosion efficiency coefficients estimated from the incised valley profiles are similar to those observed in arid climates or in regions underlain by resistant bedrocks on Earth. Our results suggest that the widespread tectonic modification of existing valley networks in the intersection sites may reflect a dynamic coevolution of tectonic and fluvial systems during Mars’ hydrologically active past.

How to cite: Chen, H., Moon, S., Kim, E., and Paige, D.: Dynamic coevolution of valley networks and wrinkle ridges in the Martian highlands: Implications for geologic evolution and paleoclimate, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4576, https://doi.org/10.5194/egusphere-egu26-4576, 2026.

Geological investigations of planetary surfaces require combination of orbital datasets. Multiple-instruments platforms operated by space agencies made the quantity of data available increase quickly. MarsSI [1] is a platform to facilitate exploring and processing those datasets.

As of 2026, MarsSI indexes and provide access to optical data (visible, multi and hyper-spectral) and derived products from the most recent missions. Our emphasis was to provide ”ready-to-use” products. MarsSI do not provide analysis or visualization tool, users will be able to use GIS or remote sensing software to run the analysis suited to their research.

MarsSI provides access to multiple optical datasets for visible, multi/hyper-spectral data. Optical imagery will follow a correction & projection piprline using ISIS (https://isis.astrogeology.usgs.gov/). Post-calibration, hyperspectral data is corrected with the volcano-scan method [2] and spectral parameter maps are produced.

MarsSI produces Digital Elevation Model (DEM) products from the CTX and HiRISE datasets (finding image pairs with a 60% minimum overlapping and 10° deviation in emission angle). DEM generation workflow was updated in 2020 with a completely new version[3].

MarsSI is accessed through a web browser portal. As shown on figure 1, the user can explore the datasets using a map interface. Data can be selected and sent to a workspace. The workspace view, shown on figure 2, allow to review products in detail, and request data processing. More Workspaces can be created to organize datasets.

When processing are finished, the user can order a copy operation, that make the requested data available in a SFTP directory. The platform now aims to complete its datasets, expanding on radar data (observation and simulation). Expanding non-martian datasets is also in our targets.

MarsSI offers the scientific communities a way to explore space agencies catalogs and automatically process them to high value products.

Acknowledgments

MarsSI is part of national Research Infrastructure PSUP, recognized as such by the French Ministry of Higher Education and Research under the ANO5 label. It was supported by the Programme National de Planétologie (PNP) of CNRS/INSU, co-funded by CNES. This application is part of the ERC project OCEANID funded by the Horizon Europe Program (ERC Grant Agreement No. 101045260).

References

[1]  C. Quantin-Nataf et al. In: Planetary and Space Science 150 (2018).

[2] P. C. McGuire et al. In: Planetary and Space Science 57.7 (2009).

[3] M. Volat, C. Quantin-Nataf, and A. Dehecq. In: Planetary and Space Science 222 (2022).

How to cite: Volat, M., Quantin-Nataf, C., Brighi, E., Dehouck, E., Millot, C., Pineau, M., Torres, I., Rogez, Y., Herique, A., and Zine, S.: MarsSI: Martian surface data processing service, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4855, https://doi.org/10.5194/egusphere-egu26-4855, 2026.

The astrobiological exploration of Mars is ongoing, with multiple missions investigating whether ancient environments could have supported life (Grotzinger et al., 2012) and whether traces of that life could still be preserved in the geological record (Farley et al., 2020). Clay-bearing terrains are regarded as prime targets for these missions because of the strong capacity of some phyllosilicates to adsorb, concentrate, and preserve organic carbon (Hedges and Keil, 1995; Kennedy et al., 2002). Early Earth clay-rich mudstones are also well known for exquisitely preserving delicate morphologies, including cells, filaments and microbial mats (Javaux, 2019). However, Martian surface radiation and oxidizing processes may alter such materials (cf. Fornaro et al., 2018). ESA’s ExoMars mission will therefore extend the search to the subsurface to access materials expected to be less altered (Vago et al., 2017). The selected landing site, Oxia Planum, is a Noachian region dominated by Fe/Mg phyllosilicates (Mandon et al., 2021) that has experienced at least two aqueous episodes, as evidenced by a clay-bearing unit overlain by fan-shaped sedimentary deposits (Quantin-Nataf et al., 2021).

If life ever existed on Mars, potential biomass sources at Oxia Planum could include (i) subsurface communities associated with clay-rich regolith, as observed in hyperarid Earth analogues (e.g., Azua-Bustos et al., 2020), later exhumed and physically reworked, and/or (ii) organisms living in surface or near-surface aqueous settings and locally incorporated into basin-floor clay-rich muds. On Earth, clay-rich sediments can physically shield labile organic matter, reducing its accessibility to microbial degradation within micro- to nano-porosity (McMahon et al., 2016), and low-oxygen bottom waters can further enhance organic carbon preservation in fine-grained deposits (Ritzer et al., 2024). Assuming anoxic conditions in Noachian depositional settings, biosignatures could be well preserved at Oxia. Yet, Oxia’s contrasting sedimentary contexts raise the following question: at constant bulk organic content and under identical diagenetic conditions, to what extent can different pre-diagenetic textures and microstructures bias the morphological and chemical signals, and thus the detectability of fossil biosignatures by vibrational spectroscopy and mass spectrometry in clay-rich sediments?

Here, we investigate this question by conducting laboratory fossilization experiments using saponite (a Mg-rich smectite, synthesized following the protocol of Criouet et al., 2023) and cells from the cyanobacterial strain Synechocystis sp. (PCC6803). Samples were prepared to represent two experimental end-members that differ in their initial texture (wet embedding within a clay-rich mud versus dry physical reworking) while maintaining the same organic content (TOC= 5 wt.%). All samples were then remoistened at the same water-to-rock ratio (W:R=3) and subsequently subjected to accelerated early diagenesis (100 °C, autogenous pressure ~2 bar, 30 days) in a closed system under an early Mars-like (CO₂-rich) atmosphere.

Experimental residues were characterized by SEM-EDS to document fossil morphologies and organo-mineral interactions from micro- to nano-scale, and by complementary spectroscopic (i.e., µRaman, FTIR) and mass spectrometric (i.e., GC-Orbitrap, EA-IRMS) analyses to evaluate associated chemical signals. Altogether, this work aims to provide well-constrained analogs for anticipating how biosignatures may be expressed across Oxia’s contrasting sedimentary contexts and to help validate space instrumentation and protocols.

How to cite: Criouet, I., Demaret, L., Boulesteix, D., Fadel, A., Buch, A., Lara, Y., Malherbe, C., Vertruyen, B., Lambion, A., and Javaux, E.: Effect of depositional mode on the detectability of microbial fossils in Mars-analog clay-rich sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5731, https://doi.org/10.5194/egusphere-egu26-5731, 2026.

Terrestrial microbial life is documented in micrometer-scale rock pores in boreholes and mines as deep as 5 km.  If life ever emerged in Mars, it may still survive actively at similar depths in the Martian crust, where temperatures are above zero Celsius. Since such Martian depths are out of reach for present technology, we set off to conceive Martian settings where putative life could be active closer to the surface.

One possible way for microbial life to approach the Martian surface is by using the warmth of eruptions to migrate parallel to magma vents, at distances where temperature is above 0 C. Magmatic activity creates dikes and surface lava flows with basalt at about 1250 C, transitorily increasing the temperature of the surrounding crust. We hypothesize that the cooling rates may be slow enough for Earth-like microbial-life to migrate through these warm corridors and approach the surface.

Bacteria and Archea swim at velocities faster than 250 m/yr and migrate through rock pores with highly variable motilities of 28 m/yr and higher (Horvath et al., 2021; Jin and Sengupta, 2024; Nishiyama and Kojima, 2012), depending on porosity types and fracturing. InSight data suggests a weakened Martian crust compatible with intense fracturing and high porosity infilled with water (Li et al., 2023), probably caused by the multi-billion-year long exposure to meteoritic impacts. Open fractures are hypothesized to be particularly prominent around and above magmatic dikes in Martian conditions due to stresses related to magma injection and later cooling (Rivas-Dorado et al., 2023). The lower Martian gravity should minimize mechanical and chemical pore compaction, contributing to make the Martian underground more passable than in Earth’s. We therefore test whether bacterial-like migration velocities can defeat post-magmatic underground cooling in Mars following a magmatic event and actively approach the surface. 

To this purpose, we perform diffusive thermal relaxation modeling of the subsurface inspired by the Elysium and Cerberus Fossae region, where 53,000 to 210,000 years old eruptions have been identified (Horvath et al., 2021). We constrain the magmatic intrusion’s geometry based on dike modeling (Rivas-Dorado et al., 2022) and on observed lava flows (Cataldo et al., 2015), supported by published interpretations of InSight seismic data. The results suggest that dike sizes are consistent with a passable pathway above freezing temperature propagating slower than Earth-like microbial motility. We constrain minimum depths reachable by hypothetical bacterial-like underground organisms as a function of realistic Martian magmatic intrusion parameters.

How to cite: Garcia-Castellanos, D., Butturini, A., Rivas-Dorado, S., Palomino, S., Schimmel, M., Jiménez-Munt, I., and Esteban, M.: Magmatic pathways for subsurface habitability on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5787, https://doi.org/10.5194/egusphere-egu26-5787, 2026.

Oxia Planum, the landing site for ESA’s ExoMars Rover, Rosalind Franklin, hosts widespread layered Fe/Mg phyllosilicate-bearing deposits of Noachian age, evidence of a potentially long-lived aqueous paleoenvironment in a deltaic to fluvio-lacustrine setting. Fluvio-lacustrine environments have moderate to high preservation potential for organic matter, due to rapid sedimentation and subsequent burial. As a result, these are also some of the environments that, over the course of Earth history, have preserved biosignatures on billion-year timescales. Microbial activity and capture within sediments can result in geochemical and mineralogical anomalies, including localised elemental enrichments. These provide a means of detecting evidence of past life in concert with molecular biosignatures. Microbial mats especially can alter the geochemistry of surrounding sediments, producing spatially constrained variations that persist over geological timescales. Investigating such biosignatures in sedimentary environments analogous to those recorded at Oxia Planum is essential for informing future rover observations and measurement strategies.

We examine clay-bearing sedimentary facies with well-preserved microbially induced sedimentary structures (MISS), including (1) the 1.0 - 1.1 Ga Clachtoll and Diabaig formations in northwest Scotland— a  package of fluviolacustrine and estuarine sedimentary rocks deposited under fluctuating redox conditions; and (2) the 2.7 Ga Tumbiana Formation (Pilbara Craton, Western Australia), which records deposition in a shallow lacustrine environment that received input from basaltic volcanism. We present elemental distributions, redox sensitive trace element behaviour, and mineralogical variations in preserved microbial mat structures and compare these to neighbouring sediments with no microbial influence. Using a combination of raman spectroscopy and elemental mapping, we show elemental enrichments linked to biology, such as iron, manganese, and potassium, coincide with clay-rich organic matter bearing areas within the sediment, indicating that ~1 – 2.7 Ga microbial mats can preserve distinct geochemical biosignatures in association with clay-bearing lithologies. The spatial association between centimetre-millimetre sized sedimentary structures observable at outcrop scale and sub-millimetre geochemical anomalies highlights the importance of integrating imaging and geochemical datasets to support biosignature interpretations.

How to cite: Nielson, G. C., Cousins, C. R., Stüeken, E. E., and Law, S.: Preservation of clay-bearing geochemical biosignatures in Mars analogue sedimentary rocks over billion-year timescales , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5974, https://doi.org/10.5194/egusphere-egu26-5974, 2026.

Landslides on Mars are abundant and far more mobile than terrestrial landslides. Their exceptional scale and mobility provide key constraints on Martian surface processes, tectonic activity, and the environmental conditions that govern landslide mechanics. However, existing global inventories remain incomplete as small, overlapping, or morphologically ambiguous deposits are difficult to capture through manual mapping alone, leaving uncertainty in understanding their spatial distribution. Automated Martian landslide detection remains challenging due to the data scarcity with only a few thousand labeled samples and the natural morphological complexity of landslides. Therefore, we propose Mars-DiSVM, a landslide identification framework based on multi-modal imagery, which fuses features extracted from CTX, MOLA-HRSC DEM, and THEMIS night-time imagery using a DINOv2 backbone, followed by a downstream SVM classifier. The classification using fused feature representations achieves the top accuracy, up to 97.5%, with precision, recall, and MCC consistently exceeding 90%. Mars-DiSVM was further assessed within four areas of interest (AOIs), including the area with mapped landslides in the existing global inventory [1] and areas without mapped landslides in Noachian/Hesperian highlands.
Our framework identified 25 previously unmapped landslides across four AOIs, where the features are predominantly located on slopes within impact craters and along valley slopes, and are classified as rock avalanches and slump/flow types. These features are generally small, with approximately
half exhibiting runout lengths shorter than 5 km, sizes which are often underrepresented in manual mapping due to limited visibility or morphological degradation. The newly mapped landslides display diagnostic morphological characteristics, including lateral levees, tongue-shaped deposits, and longitudinal ridges within the deposits. Notably, three of the detected landslides occur adjacent to impact craters, implying impact events as the possible trigger. These findings highlight the importance of improving the completeness of global inventory, providing clues to their potential triggering mechanism.
Mars-DiSVM is implemented at the global scale to generate a preliminary expanded global inventory of Martian landslides. The resulting dataset will provide new constraints on the spatial distribution of landslides, thereby improving our understanding of their relationship with key controlling factors, such as the presence of ice or water and seismic activity [2]. In addition, we plan to monitor recent Martian landslide activity by incorporating newly acquired CTX imagery, thereby gaining insights into Martian recent geological activity and triggering mechanisms.

[1] Crosta, G. B., Frattini, P., Valbuzzi, E., & De Blasio, F. V. 2018, Earth and Space Science, 5, 89, doi: 10.1002/2017EA000324

[2] Roback, K. P., & Ehlmann, B. L. 2021, Journal of Geophysical Research: Planets, 126, e2020JE006675, doi: 10.1029/2020JE006675

How to cite: Tao, Y., Pan, L., and Liu, Z.: Expanding the Global Martian Landslide Inventory with Multi-modal DINOv2 Feature Fusion and SVM Classification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6146, https://doi.org/10.5194/egusphere-egu26-6146, 2026.

Jezero crater is a 45-km diameter impact crater, formed during the Early-Middle Noachian period, ~3.9 Ga, on the northwest rim of the Isidis Planitia within the highland crust of Mars of the Nili Fossae region. Rocks excavated by the impact, thus pre-dating Jezero crater, potentially >4.0Ga, were investigated by the Perseverance rover on the rim of the crater. The outer Jezero rim displays a light-toned, layered unit informally named Witch Hazel Hill, which has been analyzed by Perseverance in locations named Broom Point and Sallys Cove. There, the SuperCam Remote Micro-Imager (RMI) and Mastcam-Z cameras revealed rocks with spherical granules, which hereafter we refer to as “spherules”, a term used here as purely descriptive. At Broom Point, we analyzed the largest number of spherule-bearing targets, among which two clasts and two bedrock targets have been analyzed thoroughly. The spherules are ~2-mm of mean diameter in all targets, are closely packed, and represent >90% of the granules. In one of the targets, they are partly broken and piled up by an energetic process. The elemental composition derived SuperCam is basaltic, close to that of the surrounding bedrock. However, the featureless infrared reflectance spectra lack signatures of hydration, and are interpreted as glasses, in agreement with their shiny surface on images. In contrast, the surrounding rocks display hydration features linked to the presence of sulphates and phyllosilicates. At Sally’s Cove, 50 m away to the north, spherules are scattered along laminae of the bedrock. They display a mean diameter (<0.5 mm) too small for SuperCam individual analysis. While no proximity science was possible at Broom Point, Sallys Cove was favourable for a chemical analysis by the PIXL instrument. The composition of the eight spherules analysed there show rims distinct from the interior, and diverse compositions ranging from plagioclase-rich to pyroxene-rich. On Earth, spherule-bearing rocks can be found in impact, volcanic or sedimentary rocks. The chemical characteristics of Jezero rim’s spherules do not favour sedimentary concretions such as those observed at Meridiani Planum. A volcanic context would reasonably explain the presence of spherical clasts such as accretionary lapilli produced by explosive volcanism. Nevertheless, the homogeneity of the spherule size and their well-defined sphericity is frequent for impact spherules observed on Earth at the K-Pg boundary for which spherules were created by droplets of melt ejected to several thousands of km. The basaltic, anhydrous composition is consistent with such a hypothesis, although it does not fully rule out volcanic fire fountains. Yet, at Sallys Cove, the variable compositions of spherules measured by PIXL are difficult to explain in a volcanic context, which assumes homogeneous compositions. Hence, we currently favour the presence of these spherules from impact ejecta. If this hypothesis was confirmed, the sample collected at this location could represent a unique opportunity to analyse impact processes at the surface of a terrestrial planet in the early history of the solar system.

How to cite: Mangold, N. and the Mars 2020 Perseverance Crater Rim spherule beds analysis team: Four-billion years old spherule beds revealed by Perseverance on the outer rim of Jezero crater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6455, https://doi.org/10.5194/egusphere-egu26-6455, 2026.

Fretted terrains are among the most striking geomorphological features on Mars. Predominantly developed in a 500-km-wide zone located along the dichotomy boundary especially between 270°W and 360°W in regions such as Deuteronilus Mensae, these landscapes are characterized by parallel ridges, troughs, and mesas separated by broad valleys. Understanding their formation provides critic insights into the geological and climatic evolution of Mars. Here we suggest that the development of fretted terrains occurred in several major stages, beginning with tectonic activity in relation with the formation of Tharsis, contemporaneous with fluvial erosion, and ending with glacial processes that further modified the landscape.

During the Late Noachian to Early Hesperian periods, Mars experienced significant crustal stress associated with the formation of Tharsis and the resulting true polar wander, leading to regional uplift along the fretted terrains. This stress generated extensional fractures and fault systems with the formation of kilometer scale U-shaped valleys. The resulting landscape consisted of plateaus and isolated mesas delineated by steep scarps.

The Mars’s climate is thought to have undergone a period of relative warm and wetter regime during the Hesperian period. During this time, heavy rainfall or snowmelt events likely led to widespread fluvial erosion. Water flowed through the pre-existing tectonic valleys, widening them into large troughs or “fretted” corridors. Fluvial processes removed material from the highlands and transported sediments northward, to the low-lying basins of the northern plains with the formation of a large sedimentary accumulation north of the fretted terrains.

The final phase in the evolution of fretted terrains was dominated by recent glacial activity. As Mars cooled during the Late Hesperian to Amazonian periods, the climate became colder and drier, leading to the accumulation of ice within the valleys.
Evidence for this glacial phase mostly includes lineated valley fills. The glaciers likely originated from snow accumulation on the plateau surfaces, which then flowed down into the valley postdating the fluvial episod.

How to cite: Costard, F., Séjourné, A., Bouley, S., and Schmidt, F.: A revised chronological formation of fretted terrains on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6618, https://doi.org/10.5194/egusphere-egu26-6618, 2026.

The SuperCam instrument onboard the Mars2020 Perseverance rover is a suite of remote sensing instruments that is operating on the Martian surface since February 2021 (Maurice et al., 2021 ; Wiens et al., 2021). It notably includes a Visible-InfraRed (VISIR) spectrometer covering the 385–465 nm, 536–853 nm, and 1.3–2.6 μm spectral ranges (Fouchet et al., 2022), which regularly performs observations of the Martian atmosphere using the passive sky geometry (Bertrand et al., 2022). At these wavelengths, scattering by aerosols is strongly sensitive to the particle size. The ability of the passive sky technique to retrieve the atmospheric dust content has been demonstrated in the VIS spectral range with MSL/ChemCam (McConnochie et al., 2018), and SuperCam is now able to probe for the first time the Martian atmosphere from the ground for both the VIS and near-IR domains, which provides further information on the aerosol properties.

Dust and water ice aerosols play an important role in the current Martian climate: they affect the thermal structure of the atmosphere as they absorb and scatter the incoming sunlight, and contribute to the global water cycle of the planet (Haberle et al., 2017). Thus, monitoring the properties of these aerosols is of importance to better understand and model the current Martian climate. On Perseverance, the optical depth of the aerosols above the rover is monitored on a seasonal and local time basis by the MEDA and ZCAM instruments (Toledo et al., 2024 ; Smith et al., 2025 ; Moya-Blanco et al., this conference).

By measuring the spectra of the sky luminosity at two different elevation angles, and by comparing the measurement with the results of a multiple scattering radiative transfer model, we are able to retrieve the aerosol properties for both the dust and water ice. Here we use the DIScrete Ordinate Radiative Transfer (DISORT) code in version 4 (Stamnes et al., 2017) through the pyRT_DISORT (Connour & Wolff, 2024) Python module to retrieve the respective optical depth of dust and water ice from the VISIR passive sky measurements of SuperCam performed since the beginning of the mission in 2021, and constrain their particle size. We assume asymmetric hexahydra dust particles and droxtals shapes for the water ice crystals, and we use vertical atmospheric profile from the Mars Climate Database version 6.1 (Forget et al., 1999 ; Millour et al., 2024). These retrievals complement the ones performed by the rover’s other instruments, notably ZCAM. While it is highly challenging with their measurements to distinguish between dust and water ice contributions in the total optical depth, their results can be directly compared with those from SuperCam, as the wavelength ranges of the two instruments overlap in the visible.

How to cite: Stcherbinine, A., Bertrand, T., Wolff, M., Lasue, J., McConnochie, T., Montmessin, F., Fouchet, T., Knutsen, E., Lacombe, G., Cousin, A., Gasnault, O., Maurice, S., and Wiens, R.: Retrieving the Properties of Martian Aerosols at Jezero Crater using SuperCam PassiveSky Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6805, https://doi.org/10.5194/egusphere-egu26-6805, 2026.

Impact-generated marsquakes with accurate positions are important to Mars seismic investigations. To better constrain the Martian crustal velocity structure, we repicked first-arrival P- and S-wave of three impacts (S0981c, S0986c and S1034a) near InSight lander and analyzed their possible ray paths. We significantly reduced body-wave arrival uncertainties by applying polarization filters and filter-bank methods. To verify that the detected energy originates from the corresponding events, the azimuth of each candidate arrival was calculated and compared with the true event azimuth. Then we derived the incidence angles from particle motion to constrain the ray path.

We find that for events at shorter epicentral distances (S0986c and S1034a), the first-arrival ray paths are typically confined to the uppermost crust. In contrast, first-arrival ray path from more distant event (S0981c) usually sample the mid-lower crust or the crust-mantle boundary. Furthermore, we detected later-arrival P-waves from S0981c. By combining these body-wave arrivals with incidence angles from three impacts, we inverted for the one-dimensional Martian crustal velocity structure beneath the InSight lander using a Markov Chain Monte Carlo (MCMC) method.

More refined processing techniques enable us to extract more information from marsquake signals, helping us understand Martian inner velocity structure better. In this study, we simultaneously incorporated body-wave travel times and incident angles into the inversion. This approach can lead to better constraints on the Martian crustal velocity structure and even constrict the Vp/Vs ratio at each crustal layer. 

How to cite: Tian, L. and Yao, H.: Improved Constraints on Martian Crustal Velocity Structure of InSight lander, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6830, https://doi.org/10.5194/egusphere-egu26-6830, 2026.