During the past 15 years I and my colleagues have studied the dynamics of free (gravity-driven) subduction using a twofold approach: numerical simulations using the boundary-element method (BEM), and interpretation of the solutions using the theory of thin viscous shells. The basic model comprises a shell with thickness h and viscosity η₁ subducting in a mantle with viscosity η₂. The mantle has a finite depth H (in 3-D Cartesian geometry) or an outer radius R₀ (in spherical geometry). The key length scale governing subduction is the 'bending length' l_b, the sum of the slab length and the lateral extent of the  seaward flexural bulge. A dimensionless 'flexural stiffness' St = (η₁/η₂)(h/l_b)³ determines whether the subduction rate is controlled by η₁ or η₂. 3-D BEM simulations closely reproduce laboratory experiments, and reveal the physical mechanisms underlying the different modes of subduction observed.   In spherical geometry, subduction is controlled by St and a 'dynamical sphericity number' Σ = (l_b/R₀) cotθ_t, where θ_t is the angular radius of the trench. Spherical BEM solutions demonstrate the 'sphericity paradox' that the effect of sphericity on flexure is greater for small (more nearly flat) plates than for large ones  (e.g. hemispherical). Another surprising result is that state of stress in a doubly-curved slab is dominated by the longitudinal normal ('hoop') stress. BEM predictions of hoop stresses in slabs with positive and negative Gaussian curvature agree well with earthquake focal mechanisms in the Mariana slab. Linear stability analysis shows that a slab under compressive hoop stress is unstable to longitudinal buckling, which may explain the peculiar geomery of the Mariana slab. Finally, I will describe a new hybrid boundary-integral/thin-shell approach to coupling mantle flow with the deformation of a thin shell having non-Newtonian rheology. 

How to cite: Ribe, N.: Thin-shell dynamics of subduction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1740, https://doi.org/10.5194/egusphere-egu25-1740, 2025.

Venus is often called Earth’s sister planet due to its similar size and mass. Apart from that, however, the two planets are wildly different, with surface temperatures on Venus that easily melt lead and a Venusian surface pressure that is almost a hundred times larger than that of Earth. Additionally, Venus is completely covered in clouds; obscuring its surface and shrouding the entire planet in mystery. 

How did the observed topographic features form? Is there still some form of tectonics ongoing? Are there earthquakes - or indeed: venusquakes? 

These are just a few of the questions that Venus scientists would love to know the answer to. Luckily, several planetary missions will explore Venus in the coming decade. Focusing on tectonics, volcanism, and Venus’ atmosphere, missions like EnVision, VERITAS, and DAVINCI will likely provide rich new datasets to start answering the multitude of questions we have about Venus’ current and past state.

Until then, modelling is a useful tool to gain a first-order understanding of the physical processes on Venus. In addition, models can be used to make predictions and end-member hypotheses that can be directly tested by the upcoming missions. 

To gain first insights on how the observed rifting structures on the Venusian surface could have formed, we adapted 2-D thermomechanical numerical models of continental rifting on Earth to Venus-like environments. Our results show that a strong crustal rheology such as dry diabase is needed to localise strain and develop rifts under the high surface temperature and pressure of Venus. Models with different crustal thicknesses fit the topography profiles of the Ganis and Devana Chasmata well, indicating that the differences in these rift features on Venus might be due to different crustal thicknesses.

The rifts of Venus are potentially still seismically active and so could the fold belts and a subset of the coronae be. Scaling the seismicity of the Earth to Venus by identifying potential analogues for different tectonic settings, allowed us to provide several end-member estimates of the potential seismicity on Venus. Our most realistic estimate for a moderately active Venus results in a prediction of a few thousand venusquakes with magnitude 4 or higher per Earth year.

To assess the feasibility of measuring this seismicity with future missions, we estimated the seismic wave detectability of different ground-based, atmospheric, and orbital techniques. Airglow imagers, which can measure seismic wave patterns in the airglow of the upper atmosphere from orbit, appear to be the most promising technique due to their long mission duration, although they are limited to detecting larger magnitude events. 

In summary, since we are faced with many unknowns when it comes to Venus, this interdisciplinary approach that combines modelling aspects from both geodynamics and seismology and integrates observational techniques is the way forward to exploring the tectonics and seismicity of Venus and unravel the mysteries of this planet. 

How to cite: van Zelst, I., Garcia, R. F., Regorda, A., Maia, J., De Toffoli, B., Plesa, A.-C., Thieulot, C., Erdős, Z., and Buiter, S. and the ISSI team #566 - Seismicity on Venus: Prediction & Detection: Exploring the tectonics and seismicity of Venus , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6949, https://doi.org/10.5194/egusphere-egu25-6949, 2025.

The tectonic framework of Bhutan Himalaya documents significant along-strike variability in crustal structure and deformation. To visualize this spatial and depth variability, we compile an extensive dataset of surface-wave phase velocities derived from seismic ambient noise and teleseismic earthquakes recorded by the temporary GANSSER network (2013-2014) in Bhutan, aiming to produce Rayleigh phase-velocity maps over the period range of 4 to 50 seconds. We translate the phase-velocity maps into a 3-D shear-wave velocity model stretching from the surface to a depth of 42 kilometres. The employed methodologies enable imaging of the upper to mid-crustal and lower crustal velocity anomalies with a lateral resolution of approximately 25 km. The obtained tomographic model fills a void in the prior established shear-wave velocity structure of Bhutan, encompassing depths from upper-crustal to lowermost crust. Our findings indicate notable mid-crustal to lower-crustal high phase velocity anomalies in central Bhutan (around 90.5). The presence of this significant anomaly within the mid- to lower crustal layer may indicate localized stress accumulation along the Main Himalayan Thrust (MHT) resulting from the interaction of the dipping and sub-horizontal Moho. This area might act as a stress concentration zone, resulting in increased deformation and enhanced shear-wave velocity in the crust. Minor fluctuations in velocity across latitude may result from variations in the local geometry of MHT (dip or ramp-flat transition). Localised high shear velocity in western Bhutan may indicate a zone of crustal thickening. Northeastern Bhutan exhibits modest shear velocity, possibly because of a flat Moho and the partial creeping behaviour of the MHT.

How to cite: Kumar, G. and Tiwari, A. K.: Multiscale Surface Wave Tomography of the Bhutan Himalayas using Ambient Seismic Noise and Teleseismic Earthquake Data , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1021, https://doi.org/10.5194/egusphere-egu25-1021, 2025.

Southeastern Tibet, a segment of the eastern Himalayan Syntaxis, is a significantly deformed area resulting from multistage subduction and the ongoing collision of the Indian and Asian tectonic plates. The region has a clockwise material movement around the indenting corner of the Indian plate, evident on the surface as strike-slip faults aligned with the Himalayan Arc. Numerous scientific studies have focused on the east-west extension and tectonic history of southeastern Tibet; however, the scientific enquiries regarding the depth constraints of the crustal flow process—specifically, whether it is confined to the middle crust or extends to the lower crust beneath southeastern Tibet—remain unresolved. This study employs ambient noise tomography to  examine a 3-D high-resolution crustal velocity model for the region, which is crucial for unravelling the mechanisms that regulate crustal deformation and evolution in active orogenic systems. To do this, we examined ambient noise data from 48 seismic stations of the XE network, operational from 2003 to 2004. We obtained Rayleigh wave phase velocities ranging from 4 to 60 seconds and subsequently inverted them to develop a 3-D shear wave velocity model of the region extending to depths of 50 km. Our results reveal persistent low shear wave velocity zones at depths of 15–25 km (within the mid-crust), notably observed between the Indus Tsangpo suture and the Bangong-Nujiang Suture. We contend that the detected low-velocity zones are only linked to mid-crustal channel flow, a mechanism presumably essential for comprehending crustal deformation. Our findings provide significant constraints on the depth localisation of crustal channel flow and the interaction of tectonic forces in southern Tibet, enhancing the overall comprehension of Eastern Syntaxial tectonics.

How to cite: Mandi, A., Kumar, G., Bishoyi, N., and Tiwari, A. K.: 3-D Crustal Shear Wave Velocity Tomography Using Seismic Ambient Noise Data in Southeast Tibet, Close to Namcha Barwa Mountain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1178, https://doi.org/10.5194/egusphere-egu25-1178, 2025.

With the continuous development of deep learning technologies, fault prediction techniques based on various neural networks have been evolving. The deep learning modules based on U-Net residual networks have shown significant advantages in both learning efficiency and effectiveness. In this paper, we propose a deep learning model that integrates a 3D U-Net residual architecture, Convolutional Block Attention Module (CBAM), and Multi-scale Enhanced Global Attention (MEGA) module for automatic seismic fault detection and segmentation. This model can effectively handle complex 3D seismic data, fully exploiting both spatial and channel information, significantly improving the prediction accuracy for small faults, while only slightly increasing the computational cost.

Firstly, the model uses the 3D U-Net as the backbone framework, where the residual blocks (BasicRes) extract features through multiple convolution layers. The CBAM module is incorporated to apply attention weighting, enhancing the model's ability to focus on critical information. The CBAM module combines channel attention and spatial attention, effectively adjusting the importance of feature maps from different dimensions, enabling the model to identify potential fault features in complex seismic data.

Secondly, the MEGA module is introduced into the model, which further improves the model's feature representation ability by fusing multi-scale features and applying a global attention mechanism. By weighting global information, the MEGA module helps the model better capture key seismic fault features during feature fusion. This design allows the model to focus not only on local details but also to fully utilize the global contextual information in 3D data, thereby enhancing the accuracy of fault detection.

After validation, the model achieved promising results in seismic fault detection tasks, automatically identifying and segmenting fault structures in seismic data. The accuracy was improved from 80% with the original 3D U-Net residual network to 85%-87%. This provides strong support for applications such as seismic exploration and subsurface imaging.

Keywords: Seismic Fault Detection, 3D U-Net, Convolutional Block Attention Module (CBAM), Multi-scale Enhanced Global Attention (MEGA), Deep Learning

How to cite: wang, Y.: Application of Optimized 3D U-Net Residual Network with CBAM and MEGA Modules in Seismic Fault Detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1772, https://doi.org/10.5194/egusphere-egu25-1772, 2025.

This article mainly studies the characteristics of the earthquake sequence and the post - earthquake trend of the Ms6.4 earthquake in Yangbi, Yunnan，China on May 21, 2021. The research area is located in Yangbi Yi Autonomous County in the western part of Yunnan Province. The earthquake caused severe disasters such as housing destruction, traffic interruption, water conservancy facilities damage and power supply interruption. Through the analysis of the basic parameters of the earthquake, the tectonic stress environment and the seismogenic structure, it is determined that the earthquake is a right - lateral strike - slip rupture, with a focal depth of 8 kilometers, consistent with the direction of the Weixi - Qiaohou and Honghe fault zones. The earthquake sequence type is determined as the main shock - aftershock type (including the foreshock - main shock - aftershock type). Spatially, the source rupture expands unilaterally from the northwest to the southeast, mostly occurring in the upper crust high - speed zone or the high - low speed transition zone. Based on the G - R relationship and other analyses, the earthquake activity cycle in this area has active and quiet periods, and there are certain abnormal change laws before strong aftershocks, such as strain accumulation, calmness or enhancement of earthquakes above magnitude 3.5, and abnormal frequency of earthquakes above magnitude 2. The conclusion is that the earthquake sequence is normal, and the post - earthquake trend shows the characteristics of long - term calmness - breaking calmness - becoming calm again - signal earthquake (main shock). In the next few years, the strain accumulation may reach the peak and release. It is predicted that there may be a larger earthquake accompanied by strong aftershocks in 2025, or enter an active period with a strong aftershock magnitude exceeding 5.9 and lasting for more than half a year. Finally, the earthquake prevention and disaster reduction countermeasures are proposed.

How to cite: Wu, B.: The determination of the seismic sequence characteristics and post - earthquake trend of the Ms6.4 earthquake in Yangbi, Yunnan, China on May 21, 2021, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2519, https://doi.org/10.5194/egusphere-egu25-2519, 2025.

Seismic inversion in geophysics is a method that uses certain prior information, such as known geological laws and well logging and drilling data, to infer the physical parameters of underground media, such as wave impedance, velocity, and density, from seismic observation data, and thereby obtain the spatial structure and physical properties of underground strata. Seismic inversion is a highly complex problem with multiple solutions, and with the advancement of collection equipment, the volume of geophysical observation data is increasing at an astonishing rate. This presents new challenges for the accuracy and speed of seismic data inversion methods. There is an urgent need to develop intelligent and efficient inversion technologies for seismic inversion.

Deep learning networks have powerful nonlinear fitting capabilities and can be used to solve complex nonlinear problems, such as seismic inversion. However, the predictive ability of deep learning networks largely depends on the quantity of training data. In the early stages of oil and gas exploration and development, the amount of well logging label data available for training is very limited, which poses a challenge for the application of deep learning in seismic inversion. Semi-supervised learning seismic inversion methods consider both data mismatch issues and well logging data mismatch issues, and can better adapt to inversion problems in real-world scenarios. Unlike supervised learning approaches, semi-supervised learning does not require a large amount of labeled data, thus it can better handle situations of data scarcity or mismatch.

This paper utilizes a semi-supervised learning workflow to perform inversion on post-stack seismic data and has conducted experimental validation on the Marmousi 2 model. The experimental results show that, compared to supervised learning networks, the semi-supervised learning network still exhibits good predictive performance with a limited amount of data, demonstrating better stability in the presence of noise and geological variations, and effectively learns the mapping relationship between seismic data and artificial intelligence. Furthermore, as the amount of training data increases, the performance of the network also improves, confirming the importance of data quantity for training deep learning networks. The application results of the network on actual data indicate that the network has broad application prospects and feasibility. However, since the network is based on a channel-by-channel inversion method, there is still a lack of representation in terms of lateral continuity, which requires further exploration and improvement in subsequent research.

How to cite: zou, C., zhang, J., tang, B., and huang, Z.: Post stack inversion of seismic data based on Semi-supervised learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2973, https://doi.org/10.5194/egusphere-egu25-2973, 2025.

Seismic attribute analysis technology has been widely used in the prediction of fluvial reservoir sand body, but the traditional seismic attribute fusion technology based on linear model has low prediction accuracy and limited application range. This study focused on the non-linear fitting between seismic attributes and reservoir thickness, and used a variety of machine learning technologies to predict the fluvidal reservoir in Chengdao area of Dongying Sag (China).The channel sand body in Chengdao area is deep buried, thin in thickness, fast in velocity and affected by gray matter, so it is difficult to predict, which greatly restricts the oil and gas exploration in this area. In this study, on the basis of fine well earthquake calibration, several seismic attributes such as amplitude, frequency, phase, waveform and correlation are extracted and correlation analysis is done to remove redundant attributes. Then model training and parameter set optimization are carried out, thickness prediction is carried out with verification set, and vertical resolution is improved by logging reconstruction and waveform indication inversion. The results show that compared with the conventional support vector machine and back propagation neural network, the prediction accuracy of echo state network optimized by Sparrow algorithm is greatly improved. Based on the comprehensive prediction method of fluvial reservoir, three large channels developed in the lower part of Chengdao area and several small channels developed in the upper part of Chengdao area are effectively described. The research method can be used for reference to the similar complicated river facies prediction.

How to cite: Huang, Z. and Zhang, J.: Study and Case Application of Fluvial Reservoir Prediction Based on the Fusion of Seismic Attribute Analysis and Machine Learning Technologies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3391, https://doi.org/10.5194/egusphere-egu25-3391, 2025.

A strong earthquake with a magnitude of Mw 7.8 and a nearby epicenter in the city of Pedernales, Ecuador, occurred on April 16, 2016. This seismic event severely affected several cities in Ecuador, including Chone and Portoviejo, both in the Manabí province, located some 85 km and 150 km away from the hypocenter, respectively. In Chone, a total of 662 homes were damaged, while 2,678 collapsed dwellings were registered in Portoviejo, where 137 fatalities were reported. These, like most cities in the Manabí province, were built in narrow valleys over colluvial and alluvial soils.  The thickness of these sediments in contact with the rock is between 40 and 70 meters, which corresponds to both ancient and contemporary alluvial plains that are supported by alluvial-colluvial and alluvial valley-fill deposits. After the 2016 interplate subduction earthquake, the main co-seismic geological effects were reported for constructions built on these soils. Landslides were primarily documented in the colluvial soils, while soil liquefaction effects were reported in soft and loose soils. In this research, the influence of the presence of paleochannels in both cities, Chone and Portoviejo, on the liquefaction effects reported during the seismic event is analyzed.

The Chone River flows through Chone city from east to west, while its western part was modified after 1975, leaving an abandoned meander where the river channel was between 7 and 22 meters wide. The soil profile in this area demonstrates a low percentage of fines, ranging from 15 to 52%, with a relative density of about 50%, making it susceptible to liquefaction. After the 2016 earthquake, evidence of liquefaction effects was concentrated along the old meander. The Portoviejo River, which flows through the city of Portoviejo, has changed from a pronounced meandering shape in 1911 to its current form. This change spans about 4.5 km with a low slope between 0.1 and 0.2%. The width of the river has also been reduced, from 12 to 19 meters. The analysis of the liquefaction evidence indicates that the damage was very severe, especially in the constructions along the river.

The damage inventories performed in both cities have evidenced that paleochannels exhibited several signs of soil liquefaction. The geological and geotechnical conditions of these soils, such as size distribution, shallow groundwater table and recent-age deposits, may be considered as factors potentially increasing the probability of liquefaction. Therefore, a geomorphological study of the cities can help identify areas with a higher liquefaction potential.

How to cite: Pastor, J. L., Ortiz-Hernández, E., Toulkeridis, T., and Chunga, K.: Influence of paleochannels on liquefaction effects in the cities of Chone and Portoviejo (Ecuador) following the strong Pedernales earthquake in 2016, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3782, https://doi.org/10.5194/egusphere-egu25-3782, 2025.

This paper proposes a deep learning model based on 3D Convolutional Neural Networks (CNN) and a custom attention mechanism (ESSAttn) for seismic fault interpretation from 3D seismic data. The model combines the advantages of self-attention mechanisms and convolutional neural networks to enhance the ability to capture and represent features in three-dimensional seismic data. The core innovation of the model lies in the introduction of the ESSAttn layer, which applies a non-traditional normalization process to the input feature queries, keys, and values, thereby strengthening the relationships between features, especially in high-dimensional seismic data. Unlike traditional attention mechanisms, the ESSAttn layer normalizes feature vectors by squaring them and integrates features across depth, width, height, and channel dimensions, significantly improving the effectiveness of attention computation.

The model's role in seismic fault interpretation is reflected in several aspects. First, the 3D convolutional layers automatically extract spatial features from seismic data, accurately capturing the location and shape of faults. Second, the ESSAttn layer enhances critical region features and focuses attention on important areas such as fault zones, reducing the interference from background noise and significantly improving fault detection accuracy. Finally, by using a weighted binary cross-entropy loss function, the model can prioritize fault regions when handling imbalanced data, improving sensitivity to weak fault signals.

The network architecture consists of three main parts: encoding, attention enhancement, and decoding. Initially, two 3D convolutional layers and max-pooling layers are used for feature extraction and down-sampling, followed by the ESSAttn layer to enhance the extracted features. The decoding part restores spatial resolution through upsampling and convolution layers, ultimately outputting the fault prediction results. The model is trained using the Adam optimizer, with a learning rate set to 1e-4.

Experimental results show that the model performs well in seismic fault interpretation tasks, effectively extracting and enhancing fault-related features. It is particularly suitable for automatic fault identification and localization in complex geological environments. The model's automation of feature extraction and enhancement reduces manual intervention, increases analysis efficiency, and demonstrates strong adaptability to large-scale 3D seismic datasets. Furthermore, the model architecture was visualized and saved using visualization tools for easier analysis and presentation.

Keywords: 3D Convolutional Neural Networks, ESSAttn, Attention Mechanism, Fault Interpretation, Weighted Cross-Entropy, 3D Seismic Data, Deep Learning

How to cite: zhang, Y.: "Deep Learning Application for Seismic Fault Interpretation Based on 3D Convolutional Neural Networks and ESSAttn Attention Mechanism", EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4961, https://doi.org/10.5194/egusphere-egu25-4961, 2025.

How to cite: Motti, A.: Active and capable faults (FAC) and buildings in Norcia, interventions carried out and possibile technicolor and regulatory actions., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5076, https://doi.org/10.5194/egusphere-egu25-5076, 2025.

Coal seam floor water hazards, caused by stress changes resulting from coal mining, are a common type of mine water disaster, and their monitoring and prevention are critical for mine safety. The mine resistivity method, a geophysical exploration technique, is widely used for monitoring and detecting such water hazards due to its high sensitivity to water-bearing structures. In practical monitoring, it is necessary to rapidly and accurately invert apparent resistivity data. However, traditional linear inversion methods are prone to local optima, leading to biased results. In contrast, deep learning-based inversion methods utilize data mining to train networks, avoiding reliance on initial models and enabling fast computation of global optimal solutions.

This study constructs a multi-layer convolutional and skip-connected U-Net model to capture resistivity features at different scales. The model is trained and validated using synthetic data to evaluate its inversion accuracy and efficiency in monitoring coal seam floor water hazards. The results show that the U-Net-based inversion method can accurately identify low-resistivity anomalies associated with water hazards in the coal seam floor and quickly achieve the global optimal solution.

The method is further applied to the inversion of resistivity models with complex boundaries to simulate the impact of stress changes caused by coal mining on the formation of floor water hazards. The results demonstrate that this method is several times faster than traditional linear inversion methods, while maintaining high consistency with the actual model. Therefore, this inversion method provides an efficient new tool for monitoring coal seam floor water hazards and holds great promise for advancing technologies in mine water disaster prevention and geological exploration.

How to cite: Wang, H. and Hu, Y.: Research on mine electrical resistivity inversion method based on Deep Learning Method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5528, https://doi.org/10.5194/egusphere-egu25-5528, 2025.

The Himalayan region, shaped by the ongoing collision of the Indian and Eurasian tectonic plates, is one of Earth’s most seismically active and geologically complex areas. The Indian plate moves northeastward at a rate of approximately 5 cm per year, driving tectonic activity in this region. Understanding earthquake source mechanisms in this region is crucial for seismic hazard assessment and geodynamic studies. Moment tensor (MT) inversion, a widely used technique for analysing earthquake faulting mechanisms, matches synthetic waveforms to observed data by minimising the misfit. However, conventional 1D velocity models often fail to capture the region’s complex lateral heterogeneities, leading to inaccuracies in source characterisation. Synthetic waveforms, generated via Green’s functions using frequency waveform (FK) methods and 1D velocity models, are critical for MT solutions, with time shifts playing a pivotal role in achieving optimal waveform correlations.

This study employs a 3D velocity model to improve MT inversion for a Mw 3.5 earthquake on 9 January 2021 (30.76°N, 78.54°E). Green’s functions were generated using the spectral element method for six simulations. Each simulation resulted in three-component waveforms, with a total of 18 synthetics per station. Observed data from 24 broadband stations were analysed, and results were compared to those obtained using 1D models. Slight variations in strike, dip, and rake values underscore the limitations of 1D models in capturing Earth’s heterogeneities.

The study reveals that 3D velocity models significantly enhance MT solution accuracy, particularly in determining focal depths, faulting mechanisms, and seismic moment magnitudes. A probabilistic approach was also applied to quantify the uncertainty associated with MT estimates, providing confidence measures. Extending this approach, MT inversion was performed for another earthquake in the Uttarakhand Himalaya using the same 3D velocity model, further demonstrating the advantages of 3D wavefield simulations in seismically active regions.

Keywords: Himalayas, Moment Tensor, Green’s Function, Spectral element method.

How to cite: Maurya, S., Silwal, V., Mahanta, R., and Yadav, R.: Earthquake Moment Tensor Inversion Using 3D Velocity Model in the Himalayas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6545, https://doi.org/10.5194/egusphere-egu25-6545, 2025.

The effect of heterogeneity (dissimilar materials) and geometry constituting an interface is an important problem in earthquake source mechanics. These two parameters in the fault interface are responsible for complex rupture propagation and instabilities compared to the homogeneous planar interface. Here, a boundary integral spectral method (BISM) is proposed to capture the in-plane rupture propagation in the non-planar bi-material interface. The conventional traction BISM suffers from the disadvantages of hyper singularity and regularisation is needed (Sato et al., 2020; Romanet et al., 2020; Tada and Yamashita, 1997). So, we are utilising the representation equation arising from the displacement formulation devised by Kostrov (1966). It uses the elastodynamic space-time convolution of Green’s function and traction component at the interface. These displacement boundary integral equations (BIEs) are the inverse equivalent of traction BIEs. When applied to an interface between heterogeneous planar elastic half-spaces, these displacement BIEs have yielded simple and closed-form convolution kernels (Ranjith 2015; Ranjith 2022). Displacement BIEs of this kind have not been utilised to analyse fracture simulation for non-planar bi-material interfaces until now. We assume the small slope assumption (Romanet et al., 2024) in our formulation to get the required displacement BIEs. Also, we expand the displacement BIEs of a non-planar bi-material interface to the leading order to obtain the non-planarity effects. Finally, we present a general spectral boundary integral formulation for a non-planar bi-material interface independent of specific geometry and traction distribution in a small fault slope regime.

How to cite: Kumar, S. and Kunnath, R.: Boundary integral spectral formulation for in-plane rupture propagation at non-planar bi-material interfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8250, https://doi.org/10.5194/egusphere-egu25-8250, 2025.

In this study, we used the P-wave receiver functions (PRFs) to investigate the crustal structure of northern Morocco, located at the westernmost edge of the Mediterranean, near to the boundary between the African and Eurasian tectonic plates. This region is an integral part of the complex crustal deformation and tectonic system associated with the Alpine orogeny, characterized by concurrent compressional and extensional processes. These dynamics have led to the development of various structural and tectonic models aimed at explaining the area‘s geological evolution. The significant tectonic activity, evident in frequent seismic events, and complex lithospheric deformation, makes it an ideal location for studying crustal variations, lithospheric interactions, and mineralogical contrasts.

To achieve these objectives, we utilized high-quality seismic broadband data from the TopoIberia and Picasso seismic experiments, provided by the Scientific Institute, as well as from the broadband seismic stations operated by the National Center for Scientific and Technical Research (CNRST). The PRFs were extracted by decomposing teleseismic P-waves to isolate the effects of the local crustal structure. The dataset covers a wide range of regional stations, and the RFs provide detailed insights into crustal thickness, density and velocity contrasts, as well as deep discontinuities. Our preliminary results reveal significant variations in Moho depth, ranging from approximately 22.7 km in the eastern part of the region to 51.7 km in the western part. These variations correlate with changes in Vp/Vs and Poisson’s ratios, indicating mineralogical heterogeneity, with compositions spanning from mafic to felsic. These findings provide new constraints for tectonic models and enhance our understanding of the geodynamic processes involved, particularly the interactions between the crust and the upper mantle. This study not only improves our understanding of active tectonics and crustal composition in northern Morocco but also offers valuable insights for refining evolutionary models of the Western Mediterranean within its complex geodynamic context.

Keywords: Teleseismic event, P-wave, Receiver functions, Seismic Network, Vp/Vs ratio, Poisson ratio, Crustal structure, Mineralogical composition, Seismotectonics, Northern Morocco.

How to cite: Zakarya, H., El Moudnib, L., Badrane, S., Zeckra, M., and Lharti, S.: Continental Crustal Structure Beneath Northern Morocco Deduced from Teleseismic Receiver Function: Constraints into structure variation and compositional properties., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9078, https://doi.org/10.5194/egusphere-egu25-9078, 2025.

Here, we disentangle a complex disturbance deposit sequence attributed to the ~M 7 1873 CE Brookings earthquake from lower Acorn Woman Lake, Oregon, USA, using sedimentological techniques, computed tomography, and micro-X-ray fluorescence. The lower portion of the sequence is derived from schist bedrock and has characteristics similar to a local landslide deposit, but is present in all cores, suggesting that it is the result of high frequency (>5 Hz) ground motions from a crustal earthquake triggered the landslide. In contrast, the upper portion of the sequence is similar to a deposit attributed to the 1700 CE Cascadia subduction earthquake (two-sigma range of 1680-1780 CE): the base has a higher concentration of light-colored, watershed-sourced silt derived from the delta front followed by a long (2-5 cm) organic tail. The soft lake sediments are more likely to amplify the sustained lower frequency accelerations (<5 Hz) of subduction earthquakes, resulting in subaquatic slope failures of the delta front. The upper portion of the 1873 CE deposit, however, has an even higher concentration of watershed-sourced silt as compared to the 1700 CE deposit, which is suspected to be the result of shaking-induced liquefaction of the lake’s large subaerial delta. The tail of both the 1873 CE and 1700 CE deposits is explained as the result of flocculation that occurred during sustained shaking. A preliminary literature search suggests that flocculation may occur during low frequency (<4-5 Hz) water motion that is sustained for an extended period of time (~minutes). The subduction interpretation of the upper portion of the 1873 CE deposit is supported by the observation of a small local tsunami offshore and the presence of a possible seismogenic turbidite attributed to the 1873 CE Brookings earthquake in southern Oregon sediment cores.

These results are important to regional seismic hazards for several reasons. Southern Cascadia crustal earthquakes, not previously recognized as a threat in southern Oregon, have the potential to cause damage to infrastructure, including the Applegate dam and buildings and other structures at Oregon Caves National Monument. They also identify a previously unrecognized recent southern Cascadia subduction earthquake. Finally, the close temporal relationship between these two types of earthquakes, not observed elsewhere in the downcore record, may be early evidence of the transition of the Walker Lane belt into a transform fault as predicted.

How to cite: Morey, A. E., Shapley, M. D., Gavin, D. G., Goldfinger, C., and Nelson, A. R.: A complex deposit sequence from a small, southern Cascadia lake suggests a previously unrecognized subduction earthquake immediately followed a crustal earthquake in 1873 CE, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11849, https://doi.org/10.5194/egusphere-egu25-11849, 2025.

Local heterogeneities on a steadily propagating crack front create persistent disturbance along the crack front. These propagating modes are termed as crack front waves. There have been numerous investigations in the literature of the crack front wave associated with a Mode I crack (for e.g., Ramanathan and Fisher, 1997, Morrissey and Rice, 1998, Norris and Abrahams, 2007, Kolvin and Adda-Bedia, 2024). It has been shown that the Mode I crack front wave travels with a speed slightly less than the Rayleigh wave. However, similar investigation of the Mode II rupture has got minimal attention. Although, Willis (2004) demonstrated that for a Poisson solid, Mode II crack front waves do not exist for crack speeds less than 0.715, explicit results on the speed of the crack front waves, when they exist, have not been reported in the literature. The focus of the present work is on a numerical investigation using a recently developed spectral boundary integral equation method (Gupta and Ranjith, 2024) to obtain the speed of the Mode II crack front waves. Further, the perturbation formulae for Mode II crack, developed by Movchan and Willis (1995) are exploited to validate the numerical results on the crack front wave speeds.

How to cite: Mouli, Y. S. C. and Kunnath, R.: Crack front waves under Mode II rupture dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14737, https://doi.org/10.5194/egusphere-egu25-14737, 2025.

In Greece, almost all accelerometer stations provided accelerometer recordings, more than 400 in total, are characterized by inferred Vs30 values based on combination of surface geology and slope proxy (Stewart et al. 2014). However, only about 15% of them have been characterized by in-situ geophysical and geotechnical methods (invasive or/and non-invasive) were performed at a distance less than 100m from the station. In addition, regarding reference rock stations where shear wave velocity Vs30 is equal or greater than 800m/sec (engineering bedrock), only five (5) of them have been characterized todate, with respective values ranging between 800Vs301183m/s. It is evident that measured site characterization parameters of accelerometer stations in Greece is far from a desired goal, especially regarding those on rock reference sites. In this study multiple/combined non-invasive passive and active seismic techniques are applied in six (6) accelerometer stations throughout Greece, to improve earthquake site characterization metadat of the national accelerometer network, focusing on stations placed on geologic rock conditions. The Vsz (S-wave) and Vpz (P-wave) profiles and thereby Vs30 site class according to the Eurocode-8 are determined. In addition, to form a holistic picture of the site’s characterization, surface geology and topographic properties are provided for the investigated stations. Results of this study aim at contributing on improving site characterization parameters estimated by the Generalized Inversion Technique (source, path, site), as well as in defining Ground Motion Models for rock site conditions.

How to cite: Theodoulidis, N., Hollender, F., Rischette, P., Buscetti, M., Douste-bacque, I., Grendas, I., and Roumelioti, Z.: Characterization of selected “rock” reference stations of the Hellenic Accelerometer Network (HAN), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16647, https://doi.org/10.5194/egusphere-egu25-16647, 2025.

Ambient noise surface wave imaging has become a powerful tool for mapping subsurface velocity structures. Recent advancements in seismology, including the widespread deployment of high-density arrays such as nodal seismometers and Distributed Acoustic Sensing (DAS) systems, have facilitated the use of subarray-based methods for surface wave dispersion data extraction, such as phase-shift, F-K, and F-J methods. Alternatively, dispersion data can also be derived from two-station approaches, such as the FTAN method. However, integrating dispersion data extracted from subarrays and two-station methods remains challenging. In this study, we propose a joint inversion framework that combines these two types of surface wave dispersion data to achieve improved constraints on subsurface structures. We demonstrate its accuracy and practical applicability by conducting numerical experiments and applying the method to field data. The proposed approach introduces intrinsic spatial smoothing constraints. It effectively integrates subarray and two-station dispersion measurements, resulting in better imaging of subsurface shear-wave velocity structures compared to using either dataset alone. The versatility and potential of this method highlight its promising applications in a wide range of geophysical scenarios.

How to cite: Luo, S.: Joint inversion of surface wave dispersion data derived from subarrays and two-station methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20181, https://doi.org/10.5194/egusphere-egu25-20181, 2025.

The Sargur Schist Belt (SSB), the oldest supracrustal greenstone belt, present in the south-eastern part of the Western Dharwar Craton (WDC), is a ~ 320 km long N-S to NNE-SSW trending discontinuous belts that occurs as patches and pockets within the granitic‒gneissic complex. The SSB is mainly composed of metamafic, metaultramafic, metapelite, banded magnetite quartzite, micaceous quartzite, pyroxene granulite, amphibolite, hornblende-biotite schist/gneiss, etc. The schistose belt has undergone at least five deformations in which the last three are very prominent. The N-S trending high strain zones with S₄ mylonitic foliation were produced during the EDC-WDC accretion (D₄ deformation). The D₅ deformation (developed due to the accretion of the WDC to Southern Granulite Terrane (SGT) along the Moyar/Bavali Shear Zone (BSZ)) developed broad open folds/warps in the N-S trend of the SSB (as well as WDC) with E-W trending axial planes. On a regional scale, the D₃ fold axes curve into the WNW-striking BSZ (D₅ deformation), a steeply dipping transpressional shear zone with dextral kinematics.

The estimated metamorphic P-T conditions of 440-585 °C and 6.0-9.5 kbar in metapelites from north to south and 640-770 °C and 7-10 kbar in granulites present in south only. The grade of metamorphism varies from greenschist facies in the north to upper amphibolite to granulite facies in the south. The metapelite and pyroxene granulite shows a loading and slow cooling path. The top to the north movement along the BSZ thrusted the high-grade metapelites, mafic-ultramafic rocks and granulite facies rocks over the WDC lithologies. The higher grade of metamorphism along the southern part as compared to the rest of the WDC is due to its location close to the WDC-SGT accretion zone. The zircons from the metapelitic schist provided older age population ranging between 3.3-3.2, 3.1-3.0 Ga followed by 2.9-2.7 Ga and 2.55-2.4 Ga, whereas the granulites (2.5 and 2.4 Ga) and foliated granites (2.6 Ga) yielded only the younger age populations. However, the monazites in schistose rocks located along the northern part recorded the oldest ages up to 2.7 Ga followed by 2.4 and 2.2-2.1 Ga ages. The monazites from foliated granites, irrespective of their location, provided ages of 2.53, 2.36 and 2.24 Ga. However, the monazites in schists and granulites from the southern part provided younger ages of 0.77, 0.67, 0.53 Ga. The prominent 0.84, 0.76 and 0.62 Ga monazite ages obtained from the metapelites close to the BSZ suggests that the accretion along the BSZ initiated in Mid-Neoproterozoic and continued till Early-Paleozoic. 

How to cite: Swain, M. and Rekha, S.: Structure, metamorphism and geochronology of Archean Sargur Schist Belt, southern India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-941, https://doi.org/10.5194/egusphere-egu25-941, 2025.

This study analyses shear wave splitting measurements for core-refracted SKS and SKKS phases using data from nine strategically positioned seismic stations operated between 2023 to 2024 in the Central Indian Tectonic Zone (CITZ). The CITZ was formed during the mesoproterozoic orogeny in central India, resulting from the collision of the northern Bundelkhand Craton with a jumble of South Indian cratons (Dharwar, Bastar and Singhbhum Cratons). Understanding seismic anisotropy in this region is essential for elucidating mantle deformation patterns, which provides vital insights into geodynamic processes, lithospheric interactions, and ongoing tectonic activities shaping the CITZ. We employed both rotation-correlation and transverse energy minimisation techniques to determine the shear wave splitting parameters, namely the fast polarization directions (FPDs) and splitting delay times (δt). A total of 104 high-quality splitting measurements and 37 null measurements were obtained from 85 earthquakes (M ≥ 5.5) within epicentral distances of 84°-145° for SKS phases and 84°-180° for SKKS phases. The averaged δts at each seismic station ranges from 0.8 to 1.3 seconds, demonstrating significant anisotropy and heterogeneity in the upper mantle under the studied region. Our observations predominantly reveal NE-SW FPDs throughout the majority of stations, which correlate with the Absolute Plate Motion (APM) of the Indian plate. The discrepancies between FPDs and APM direction at some stations suggest the presence of fossilised anisotropic fabrics resulting from prior subduction events during mesoproterozoic. The smaller δt (0.8 sec) at the seismic station in the Pachmarhi region may be attributed to the significant magmatism during the cretaceous period. Null measurements, in conjunction with splitting measurements, suggest that the stations may be located in a region characterized by multi-layered or complex anisotropy. Our observations indicate that the mantle flow beneath the CITZ is influenced by the contemporary APM direction of the Indian plate as well as lithospheric frozen anisotropy.

How to cite: Bishoyi, N., Tiwari, A. K., and Dubey, A. K.: Mantle Deformation Pattern Beneath Central Indian Tectonic Zone: A Seismic Anisotropy Study in Satpura Gondwana Basin and Surrounding Areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-964, https://doi.org/10.5194/egusphere-egu25-964, 2025.

A mineralogical study of early Cretaceous lamproite sill intrusions from the Raniganj Gondwana sedimentary basin in eastern India shows that apatite occurs as both phenocrystic and groundmass phase. Based on texture and compositional zoning patterns of apatite in lamproites from the Rajpura and Ramnagore collieries, three paragenetic stages of apatite are identified. Early-magmatic apatite (Ap-I), which forms the core of zoned grains, is Sr-rich–LREE-poor fluorapatite. This apatite underwent resorption prior to the growth of a second generation of magmatic fluorapatite (Ap-II). In Rajpura, Ap-II overgrowth rim is richer in Sr and LREE compared to Ap-I core. The increase in LREE is explained by the substitutions: (Na,K)⁺ + ∑LREE³⁺ = 2Ca²⁺, and [2∑LREE³⁺ + ₶ = 3Ca²⁺]. Ramnagore Ap-II overgrowth rim is oscillatory-zoned with fluctuations in Sr and LREE, which likely resulted from slow rate of diffusion of these elements relative to fast growth of crystals. Apatite of the third generation (Ap-III) forms the outermost rim of zoned grains and is marked by enrichment in Na, K and Ba. The substitutional schemes which explain the increase in Na and K from Ap-II to Ap-III are: (Na,K)⁺ + CO₃^2– = Sr²⁺ + PO₄^3– and [(Na,K)⁺ + (F,OH)^– = ₶ + ₶]. The role of carbonate in the former substitution is supported by high content of stoichiometrically calculated carbon (0.21–0.30 apfu) in Ap-III. The formation of Ap-III is attributed to metasomatic alteration of Ap-II by CO₂-bearing hydrothermal fluid and is associated with sodic metasomatism. Microporous texture has developed in Rajpura Ap-III which suggests a dissolution–reprecipitation mechanism for its development. This study demonstrates that compositional variations among different generations of apatite provide a meaningful record of melt evolution from early magmatic to magmatic-hydrothermal stages.

How to cite: Saini, J., Patel, S. C., and Kaur, G.: Apatite compositional constraints on the magmatic to hydrothermal evolution of lamproites from Raniganj Basin, eastern India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1988, https://doi.org/10.5194/egusphere-egu25-1988, 2025.

The Neoproterozoic western margin of the Yangtze Block in South China records significant continental crust-forming and modification processes through two distinct magmatic episodes. Using integrated geochemical and petrological approaches, we demonstrate that the 811-802 Ma Yuanmou Complex comprises alkaline high-Nb mafic rocks characterized by high Nb (15.7-41.9 ppm), TiO₂ (2.13-3.39 wt%) contents and positive ε_Nd(t) (+4.8 to +6.9), coupled with adakitic granodiorites showing high Sr/Y (17.4-49.0), (La/Yb)_N (16.3-52.6) and consistent bulk rock ε_Nd(t) (-0.5 to -1.5) and zircon ε_Hf(t) (0.0 to +2.3). The younger 750 Ma Jinping I-type granites exhibit high SiO₂ (71.2-73.5 wt%) and alkalis contents, enriched LREE patterns and depleted isotopic signatures (ε_Nd(t): -0.4 to +1.3; zircon ε_Hf(t): +4.83 to +8.37). Thermodynamic modeling reveals how crustal water content-controlled magma generation at different depths - low water-fluxed melting (2.0-3.5 wt% H₂O) produced I-type granites at medium pressure (6-9 kbar), while deeper settings with higher water content generated adakitic melts. The high-Nb mafic rocks in the Yuanmou Complex, derived from metasomatized mantle wedge, provide evidence for crustal-mantle interaction during back-arc extension. These coupled magmatic processes demonstrate how water content variations with depth influenced continental crust formation and evolution in arc settings.

How to cite: Huang, B., Wang, W., Zhao, J., Khattak, N. U., Li, R., Huang, S.-F., Lu, G.-M., Sun, L., Xue, E.-K., Zhang, Y., and Cai, X.-Y.: Water-fluxed melting and back-arc extension in the continental arc: Evidence from I-type granites, adakitic rocks and high-Nb mafic rocks at the western margin of the Yangtze Block, South China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7536, https://doi.org/10.5194/egusphere-egu25-7536, 2025.

A petrological and geochemical study was performed on 5 selected samples of peridotites from two different sites (Finero and Balmuccia) outcropping in the Ivrea Verbano Zone, with the aim to investigate the processes occurring in the deep lithosphere and the possible interaction with the lower crust.

The peridotites from Finero area fall in the harzuburgite (FIN1, FIN3, FIN4) field whereas those from Balmuccia are lherzolithes (BALM1) and werlhites (BALM4), highlighting respectively the presence of a more fertile and primordial mantle for two sites.

The rocks from Finero are featured by higher MgO (42-45.7 wt%) and lower Al₂O₃ (0.6-2.4 wt%), CaO (0.42-2.09 wt%) content with respect to Balmuccia (MgO: 39.6 wt%, Al₂O₃: 2.9 wt%; CaO: 2.8 wt%) as a consequence of their harzburgitic nature. They display an enrichment in large-ion lithophile elements (LILE), light rare earth elements (LREE, La_N/Yb_N:13.6) and depletion in high field strength elements (HFSE) differently from the Balmuccia peridotites, which are featured by a light depletion in LREE (La_N/Yb_N:0.4-0.8) and nearly flat HREE pattern. The LILE and LREE enrichment measured in the Finero peridotites could suggest that a portion of the mantle below Ivrea Verbano area was influenced by metasomatic fluids/melts. The BALM4 sample is characterized by anomalously low values of MgO (16.05 wt%) and high values of Al₂O₃ (16.3 wt%) and CaO (14.5 wt%), reflecting the high modal proportion of spinel.

Even the higher Sr (⁸⁶Sr/⁸⁷Sr= 0.70736-0.72571) and lower Nd (¹⁴³Nd/¹⁴⁴Nd=0.51236) isotopic values measured in selected mineral phases from Finero with respect to Balmuccia (⁸⁶Sr/⁸⁷Sr= 0.70268-0.70644; ¹⁴³Nd/¹⁴⁴Nd=0.51334) allow to speculate a relation with crustal fluids in the Finero mantle.

The composition of fluid inclusions entrapped in olivine and pyroxene crystals from Finero peridotites evidenced CH₄ and CH₄-N₂ associated with antigorite and magnesite whereas prevalent CH₄ associated with antigorite, magnesite and graphite was measured in the rocks from Balmuccia area. The origin of CH₄ could be related to synthesis via reduction of CO₂ by H₂ from internal/external serpentine to minerals or re-speciation of initial CO₂-H₂O fluids associated to graphite precipitation during cooling by obduction after orogeny; differently, the CH₄-N₂ fluids could be introduced by past subduction-related processes.

The isotopic helium (³He/⁴He ratio) varies between 0.08 and 0.17 Ra in the Finero peridotites and among 0.18 and 0.48 Ra in the Balmuccia ones, evidencing an isotopic difference between the two sites that cannot be explained by ⁴He radiogenic production. Differently, the Finero-Balmuccia variability could reflect the helium signature recorded in deep by subduction events and confirm the previous petrologic and geochemical evidences in favour of a metasomatised mantle by crustal fluids in the Finero area with respect to a more primordial in the Balmuccia one.

How to cite: Correale, A., Romano, P., Arienzo, I., Caracausi, A., Carnevale, G., Fazio, E., Mormone, A., Paonita, A., Piochi, M., Rotolo, S. G., and Zucali, M.: Two different mantle types as evidenced from a geochemical and petrological study of peridotites from the Ivrea-Verbano Zone , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8654, https://doi.org/10.5194/egusphere-egu25-8654, 2025.

The viscosity of silicate melts is one of the most important physical parameter governing natural processes such as volcanic eruptions, as well as manufacturing processes in the ceramic and glass industries. The traditional techniques for measuring viscosity are commonly time- and energy-consuming, they require equilibrium conditions, and are mostly limited to reduced viscosity intervals. Reducing testing time is a critical target for both academic and productive purposes. In order to calibrate an efficient tool capable of both reducing testing time and expand the range of viscosity determination, we used the hot stage microscope (HSM) technique. Specimens (pressed powders) of natural samples, previously measured employing a combination of concentric cylinder and the micropenetration dilatometric techniques, were heated at a rate of 10°C/min until melting. Characteristic shapes (Start sintering, End sintering, Softening, Sphere, Hemisphere, and Melting) were observed at characteristic temperatures (CT); then their viscosities were calculated from their known viscosity-temperature (Vogel-Fulcher-Tammann, VFT) relationships. The observed shapes result from a combined effect of viscosity and surface tension, allowing viscosity values at each CT to linearly scale with surface tension. Viscosity was calibrated by introducing correction factors based on glass chemistry. This approach provides two independent data sets – CT (from HSM) and the corresponding characteristic viscosity (from glass composition) – which can be used to calculate the VFT parameters. The comparison between calculated and experimental viscosity shows good correspondence, which significantly improved previous attempts using only HSM data. These results also highlight the potential of this non-contact technique for evaluating the effects of crystalline particles and porosity on the rheological properties of alumosilicate melts.

Contribution of PNRR M4C2 - PRIN 2022PXHTXM - STONE project, funded from EU within the Next generation EU program. CUP: D53D23004840006

How to cite: Giordano, D., Molinari, C., Dondi, M., Conte, S., and Zanelli, C.: A Method for Measuring Viscosity of Silicate Melts Using Hot Stage Microscopy (HSM), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8768, https://doi.org/10.5194/egusphere-egu25-8768, 2025.

Four multicomponent metaluminous glasses were designed to investigate the evolution of residual glass-ceramics comprising glass and crystals. Samples were obtained from melting of quartz-feldspars mixes (with varying Na/K ratio and silica content) further fast sintered at temperatures of 1200-1260°C. Using an integrated approach combining high- and low-frequency Raman spectroscopy and Differential Scanning Calorimetry (DSC), we characterized the viscous and elastic response of the residual glass and its role in the mechanical properties of the corresponding ceramic products.

High-frequency Raman spectroscopy allows for the analysis of Qn species, which represent the polymerization state of the glass network. Q⁰, Q¹, Q², Q³, and Q⁴ correspond to isolated tetrahedra, short chains, branched structures, and fully polymerized networks, respectively. This provides insights into how chemical composition affects the microscopic structure of the residual glass. Simultaneously, low-frequency Raman spectroscopy probes the boson peak, a signature of collective vibrational modes in the glass, which is directly linked to its elastic properties. By coupling the boson peak analysis with the elastic medium scaling law, we determine the vibrational density of states and shear modulus, key parameters for understanding the mechanical behavior of the system.

DSC measurements further enable the determination of critical thermal transitions of the glass, including the glass transition temperature, crystallization, and relaxation processes, which are essential for characterizing the viscous behavior of the residual glass. The integration of these techniques provides a comprehensive understanding of the role of residual glass in stress transfer and mechanical properties control within multicomponent ceramics.

This is a first insight on the characteristics of technologically relevant glasses for the production of porcelain and vitrified ceramic tiles. The approach here followed actually allows appreciating the effect of variations in the Na/K ratio and silica content that mirror what can occur in the industrial production. This paves the way for application in more complex materials and real industrial conditions.

Contribution of PNRR M4C2 - PRIN 2022PXHTXM - STONE project, funded from EU within the Next generation EU program. CUP: D53D23004840006

How to cite: Giordano, D., Cassetta, M., Conte, S., Zanelli, C., Molinari, C., Dondi, M., and La Felice, S.: Characterization of Residual Glass Evolution from Vitrified  Ceramics: Insights from Raman Spectroscopy and DSC into Viscous and Elastic Properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8978, https://doi.org/10.5194/egusphere-egu25-8978, 2025.

Investigating the main geochemical characteristics of the lower continental crust is essential to understand its formation and evolution, identifying crustal differentiation processes and possible crust-mantle interactions. We performed bulk rock (major and trace elements), noble gases isotopes (He, Ne, Ar), and fluid inclusions (Raman spectroscopy) analyses on metamorphic rocks from Ivrea-Verbano Zone (Southern Italian Alps). Specifically, we studied various lithologies (metapelite, metagabbro, mafic and felsic granulite, amphibolite, and gneiss) to analyse the continuous metamorphic gradient from amphibolite- to granulite-facies.

Bulk rock analyses confirm the mafic nature of the protoliths for metagabbros (MgO = 5.36-10.25 wt.%), mafic granulites (MgO = 8.32-25.80 wt.%) and amphibolite (MgO = 7.98 wt.%) plotting in the metabasite field of the ACF chemographic diagram. Felsic granulite and sillimanite-gneiss fall within metamorphosed quartz-feldspar rocks, except for metapelite, which approaches the metacarbonate field, due to the presence of secondary carbonates. Metagabbros, mafic granulites and amphibolite show low REE concentrations (∑REE between 3 and 25 ppm) and high Cr and Ni contents (up to 1865 and 265 ppm respectively in mafic granulite), reflecting the mafic/ultramafic nature of the protoliths, whereas felsic granulite, sillimanite-gneiss and metapelite show higher REE contents (∑REE between 48 and 197 ppm).

³He/⁴He isotope ratios in metamorphosed quartz-feldspar rocks (0.06-0.30 Ra) and metabasites (0.15 and 0.45 Ra) are significantly radiogenic, although the metabasites show slightly higher values, corroborating a more primitive component in their source. Most samples plot near the air component in the ²⁰Ne/²²Ne vs ²¹Ne/²²Ne diagram, except for mafic granulites which show a crustal-air mixing trend. As regards the Ar isotope ratios, all samples appear rich in radiogenic component (⁴⁰Ar/³⁶Ar up to 2645 in metagabbros).

Raman spectroscopy analyses on fluid inclusions in orthopyroxene from mafic granulites show the coexistence of talc, graphite and magnesite with methane, providing direct evidence of a complex history in terms of post-metamorphic reactions and P-T-fO₂ conditions.

Our preliminary results show the compositional diversity and evolution of the lower continental crust, highlighting the interplay between mafic and sedimentary sources and the importance of fluid interactions and post-metamorphic processes.

How to cite: Carnevale, G., Caracausi, A., Correale, A., Fazio, E., Paonita, A., Romano, P., and Zucali, M.: Geochemical characterisation of Permian lower continental crust: case study from Ivrea-Verbano Zone (NW Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9306, https://doi.org/10.5194/egusphere-egu25-9306, 2025.

Experimental data on rock physical properties obtained through laboratory methods are enhanced by advanced techniques like X-ray microtomography (µCT) and image analysis. Lava rocks are important geological formations worldwide with varying textures, structures, and physical and mechanical behaviour. This research focuses on the heterogeneity analysis of vesicular lava rocks with intermediate composition from the Fogo Volcano (or Água de Pau Volcano, S. Miguel, Azores, Portugal). The effective porosity of six cubic samples is determined using the buoyancy technique. Ultrasonic wave velocities and capillarity absorption coefficient are obtained along three orthogonal directions using the through-transmission method and a European standard, respectively. Unconfined compressive strength (UCS) combined with µCT is determined in three cores from a single cube.

Results demonstrate that pore structure governs water uptake by capillarity and ultrasonic wave velocities. Regardless of the direction, the nonlinear water imbibition reflects a bimodal pore size distribution, confirmed through µCT imaging. The Sharp Front model describes this behaviour as the sum of two separate absorption processes related to larger (28.01-12.96 g/m²·s^0.5) and finer (0.45-1.73 g/m²·s^0.5) pores. Capillary-connected porosity (5.07%) is lower than connected porosity (18.5–20.1%) since gravitational fluid transport dominates for large pores (>1 mm). P-wave velocities (2802–3208 m/s) show minor dependence on pore shape, while Vp/Vs ratios (1.76 ± 0.25), dynamic Young’s modulus (16.78 ± 3.20 GPa), and Poisson’s ratio (0.23 ± 0.11) reflect vesicular textures.

µCT-based image analysis enables porosity quantification, revealing that effective porosity includes vesicles and pore-linking fractures. Permeability (0.7–6.6 mD) depends on tortuosity, which reduces fluid percolation despite higher connected porosity.

UCS (15.5-36 MPa) variations depend on pore size, orientation relative to the loading direction, and connected porosity, with minor influence from pore shape. µCT imaging reveals failure through tensile splitting, with fractures propagating from pore edges in all cores. The weakest specimen has more plagioclase phenocrysts, whose borders, intragranular cracks, and pores contribute to reduced strength.

These findings underscore the need to consider the heterogeneous pore structure of vesicular lavas when interpreting field measurements or improving volcano stability models. Advanced imaging and computational techniques clarify the role of vesicles and phenocrysts in strength and crack development patterns, providing important insights into the mechanics of lava rocks.

How to cite: Pereira, M. L., Cueto, N., Pappalardo, L., Buono, G., Falasconi, A., Moreira, M., Zanon, V., and Fernandes, I.: Characterisation of the heterogeneity of vesicular lava rocks from Fogo Volcano (Azores, Portugal) combining conventional laboratory methods with X-ray microtomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9505, https://doi.org/10.5194/egusphere-egu25-9505, 2025.

In the last decades, the volcanically active Aeolian Islands have been the focus of numerous geochemical investigations and monitoring activities, primarily focused on the islands of Vulcano, Stromboli and Panarea. However, relatively few studies have explored the geochemical characteristics of other islands, despite evidence of hydrothermal activity. Salina, for instance, hosts a shallow, cold, low-salinity aquifer that overlies a deeper warmer aquifer, with highly saline water. Additional noteworthy features include hydrothermal deposits on the seafloor and offshore submarine gas emissions. Similarly, Lipari hosts a thermal aquifer (e.g. Terme di San Calogero) and exhibits significant hydrothermal emissions along its western coast, particularly in areas of Valle del Fuardo and Caolino quarry. In this study we conducted detailed geochemical surveys on Lipari and Salina to investigate the origins of the fluids and their relationship with the geodynamic framework. The research is part of the Project CAVEAT (Central-southern Aeolian islands: Volcanism and tEArIng in the Tyrrhenian subduction system), which aims to provide a comprehensive understanding of the current geodynamics in the southern Tyrrhenian region, focusing on the interaction between volcanism and tectonic activity within the Tyrrhenian subduction system.

On Salina and Lipari islands, soil CO₂ flux measurement campaigns were conducted to examine the spatial distribution of soil CO₂ emissions. Thermal surveys using an Unmanned Aircraft System were conducted over fumarolic areas to detect thermal anomalies associated with zones of preferential fluid emissions. These measurements helped define preferential pathways for fluid migration and identify active tectonic structures associated with areas of elevated soil CO₂ emissions. At selected sites, isotopic composition of gas was analyzed to infer the gas origins. On Lipari, soil CO₂ emission anomalies revealed a NNW-SSE alignment consistent with the area’s primary tectonic structures. Isotopic analysis confirmed a contribution of deep-origin fluids to these emissions. Thermal (up to 45.8 °C) and cold waters from Salina and Lipari were sampled and analyzed for their chemical and isotopic composition, as well as for dissolved gases. The isotopic composition of the water clearly indicates that the sampled groundwater originates from a mix of meteoric water and seawater, with varying degrees of mixing at each site. Gases dissolved in water exhibit an atmospheric component with a high content of CO₂ in the most brackish samples. At Salina, the isotopic composition of dissolved helium reflects a mantle contribution. Collectively, the findings emphasize the significant influence of mantle and deep-origin origin fluids in shaping the geochemistry of both islands. They further highlight the critical role of geodynamic and tectonic processes in governing fluid emissions across the two islands.

How to cite: Camarda, M., De Gregorio, S., Liotta, M., Di Martino, R. M. R., Oliveri, Y., Palano, M., Pisciotta, A., Riolo, G. M., and Romano, P.: Unveiling the geochemistry of fluids in the Central Aeolian Islands (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10890, https://doi.org/10.5194/egusphere-egu25-10890, 2025.

During active-source 2D marine ocean bottom seismic exploration, significant deviations of shot lines from the designed survey lines can introduce errors in 2D structural models, particularly in areas with rough bathymetry, such as mid-ocean ridges. By employing 3D tomography, it is possible to construct a three-dimensional model of the survey area that incorporates the actual shot locations and Ocean Bottom Seismometer (OBS) positions, leading to more accurate velocity structure models.

In 2021, the Joint Arctic Scientific Mid-Ocean Ridge Insight Expedition (JASMInE) acquired high-quality OBS data from the Gakkel Ridge in the Arctic Ocean. However, due to the presence of dense floating ice, significant offsets occurred between the shot lines and the OBS station profiles. Consequently, applying a 3D tomography-based modeling approach is essential for imaging the velocity structure in this region.

This study utilized the JIVE3D software to develop a 3D P-wave velocity model along a profile perpendicular to the 85°E spreading axis of the Gakkel Ridge, based on high-resolution multibeam bathymetry data. Compared to the velocity structure derived from 2D modeling, the P-wave velocities beneath the spreading axis are found to be lower in the 3D model, while lateral velocity variations in the upper oceanic crust are more pronounced away from the spreading axis. Despite these differences, the overall velocity structure and crustal thickness trends are consistent, indirectly validating the reliability of the 2D structural model.

Based on this 2D P-wave model, with data of 1257 S-wave arrival times picked from 9 OBS stations along the profile perpendicular to the mid-ocean ridge, using a forward modeling trial-and-error approach, a preliminary Poisson’s ratio structure beneath the profile was obtained. The Poisson’s ratio in Layer 2 of the oceanic crust ranges from 0.36 to 0.40, with relatively lower values beneath the spreading axis. In Layer 3, the Poisson’s ratio varies from 0.28 to 0.38. The relatively higher Poisson’s ratio values may indicate the presence of abundant fractures or fluids within the oceanic crust in this region.

How to cite: Niu, X., Li, J., Yang, W., Yu, J., Ding, W., and Zhang, T.: Poisson’s ratio structure and three-dimensional P wave velocity structure beneath the profile across the Gakkel ridge 85°E axis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11736, https://doi.org/10.5194/egusphere-egu25-11736, 2025.

Natural CO₂ emissions play a crucial role in understanding global CO₂ budget estimates. Consequently, numerous studies have focused on CO₂ emissions across various regions worldwide. However, the majority of these investigations have concentrated on terrestrial CO₂ emissions, with relatively fewer studies exploring submarine CO₂ emissions. Moreover, almost all the studies have focused on areas with significant hydrothermal activity, particularly those along Mid-Oceanic Ridges, while shallow-water hydrothermal vents have received comparatively little attention. Furthermore, diffuse submarine gas emissions, lacking or with little visible surface evidence, remain largely unexplored. This study investigates the CO₂ emissions in the shallow submarine environment around the coast of the Island of Vulcano (Aeolian Islands, Italy) by measuring dissolved CO₂ concentrations. Vulcano, has been characterized by an intense hydrothermal activity since its last eruption from La Fossa cone (1888-­1890). Vulcano features several fumarole fields, including one on the northern crater rim of La Fossa cone and another near the sea in the northeastern sector. Additionally, significant soil CO₂ degassing occurs across the volcanic edifice. In the Vulcano Porto area, numerous thermal wells discharge fluids with temperatures reaching up to 80 °C. Submarine emission areas are visible, at shallow depths, close to the beaches in the southern and northeastern sectors. Measurements of dissolved CO₂ concentrations were conducted along seashores and rocky coastlines and in sites encompassing both visible and non-visible emissions. In the northeastern sector, measurements focused on the area between the Vulcanello peninsula and the northern slopes of the volcanic cone. The northernmost section of this area, extending to the Faraglione cone, is widely recognized in the literature as Baia di Levante (BL), a well-documented site of significant CO₂-dominant hydrothermal fluids discharge, trough submarine vents placed on the seafloor, at shallow depth, near the shoreline. In this area, we performed measurements along the beach at depth of about 50 cm below sea surface. The measured values remain elevated throughout the entire profile, consistently surpassing those of seawater in equilibrium with the atmosphere (ASSW). Concentrations peaked near visible bubbling zones, with concentration values ​​that exceeded the 20%. Moving southward, between the port dock and the crater slopes, measurements were conducted both close to the coastline and approximately 30 meters off the coast. In this area, sporadic bubble emissions from the seafloor were observed and the concentration of dissolved CO₂ decreases significantly compared to the BL area. However, the dissolved CO₂ concentration remain elevated, above those expected for ASSW. Along the eastern coast, measurements were performed in two selected sites along the rocky coastlines. Anomalous dissolved CO₂ concentrations, reaching up to 1400 ppm, were recorded also in these areas. In the southern sector, measurements were taken along Gelso beach. CO₂ concentrations were consistently high along the entire beach profile. The results indicate that submarine CO₂ emissions are not confined to areas with visible surface evidence, but also occur in areas with minimal or no-visible hydrothermal activity.

How to cite: De Gregorio, S., Camarda, M., Cappuzzo, S., Francofonte, V., and Pisciotta, A.: Investigations on the shallow submarine CO2 emissions around the Island of Vulcano (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11968, https://doi.org/10.5194/egusphere-egu25-11968, 2025.

Correlating surface hotspot volcanism with sharply defined edges of Large Low Shear Velocity Provinces (LLSVPs) is a common yet potentially oversimplified approach in mantle geodynamics. Such direct radial projections ignore the lateral displacement of plume conduits observed in seismic tomographic imaging, which suggests that purely vertical transport through the mantle is not guaranteed. Furthermore, many studies merge the African and Pacific LLSVPs, despite evidence that their correlation with hotspots differs significantly. These oversimplifications can lead to misinterpretations of plume-lithosphere interactions, the interaction between mantle plumes and the ambient ”mantle wind”, and mantle flow dynamics in general. Here, we systematically investigate how varied criteria can alter the inferred hotspot– LLSVP edge relationship. We separately analyze African and Pacific LLSVPs using: multiple tomography models, horizontal-gradient based definitions of edges, different vote-map methodologies, and distinct plume geometry assumptions–from perfectly vertical “spokes” to randomly deflected trajectories. We also apply the 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), to provide a geodynamically consistent assessment of the relationship between present-day hotspot locations and their source regions in the deep lower mantle. This independent geodynamic assessment clarifies how arbitrary choices concerning the interpretation of hotspots and LLSVP edges may lead to biased or skewed deep-plume reconstructions. Our results reveal that adjustments in hotspot catalogs, or the decision to combine the two main LLSVPs rather than regard each as dynamically distinct, can yield important differences in the significance attributed to sharply defined LLSVP edges. These findings underscore that commonly cited correlations between hotspot locations and LLSVP boundaries hinge on assumptions that vary considerably across the literature. Recognizing and rigorously defining input parameters–particularly the separate treatment of the African and Pacific LLSVPs and the inclusion of realistic lateral plume deflection–proves essential for robust interpretations of deep Earth structure. This highlights the need for standardized methodologies and careful parameter choices to avoid overstating the importance of LLSVP edges in shaping plume pathways.

How to cite: Johnston, G., Liu, S., Forte, A., and Glisovic, P.: Playing with Edges: The Influence of Arbitrary Definitions on Hotspot–LLSVP Correlations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14815, https://doi.org/10.5194/egusphere-egu25-14815, 2025.

The 2023-2024 eruptions at Sundhnúksgígar in Iceland produced tholeiitic basaltic lavas that traveled at high velocities, affecting vast areas. In this context, disequilibrium crystallization can play a fundamental role in modulating the lava flow dynamic and inundation capacity. To investigate this phenomenon, we performed a comprehensive rheological characterization of the Sundhnúksgígar basaltic liquid and crystal-bearing suspension under both disequilibrium and near-equilibrium conditions. Compared to other basalts erupted worldwide, our results reveal unique features of the Sundhnúksgígar melt: i) exceptionally low solidification rates and ii) the ability to crystallize even at the highest cooling rates applied during the experiments. These characteristics enhance the efficiency of external crust formation, minimizing heat loss from the inner portion of the lava flow, which consequently experiences slower cooling rates. As a result, the lava is able to flow for longer times and travel greater distances than other basaltic flows. Our findings underscore the critical influence of disequilibrium crystallization on the rheological evolution and emplacement behavior of basaltic lavas, with implications for hazard assessment and risk mitigation during effusive eruptions.

How to cite: Di Fiore, F., Vona, A., Di Genova, D., Caracciolo, A., Pontesilli, A., Calabro', L., Giuliani, G., Mollo, S., Bondar, D., Nazzari, M., Romano, C., and Scarlato, P.: Impact of Cooling Rate on Rheology and Emplacement Dynamics of Basaltic Lava Flows: Insights from the 2023-2024 Sundhnúksgígar Eruption (Iceland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17683, https://doi.org/10.5194/egusphere-egu25-17683, 2025.

This study focuses on characterizing seismogenic zones by establishing a interrelationship between electrical and elastic properties using Effective Medium Theories (EMTs). The seismogenic zones exhibit complex geological and geophysical signatures that can be explored through joint analysis of electrical resistivity and elastic moduli. The research applies EMTs such as Self-Consistent Approximation (SCA), Generalized Effective Medium (GEM), and Differential Effective Medium (DEM) to model the physical properties of rocks under varying conditions of pressure, porosity, and fluid saturation.

The study compares theoretical predictions with observed data to understand how resistivity, influenced by fluid connectivity and composition, correlates with elastic properties, which are sensitive to stress and fracture networks. The study can reveal critical insights into the mechanical and fluid characteristics of seismogenic zones. By integrating theoretical models with available geophysical data, this work provides a framework for analyzing the interdependence of electrical and elastic properties in seismogenic regions. The findings contribute to advancing the understanding of fluid dynamics, and rock deformation in seismogenic zones, offering a valuable tool for seismic hazard assessment and monitoring.

How to cite: Raju, K. and Siniscalchi, A.: Interrelationship between the electrical and elastic properties using effective medium theories, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17921, https://doi.org/10.5194/egusphere-egu25-17921, 2025.

The Istituto Nazionale di Geofisica e Vulcanologia - Osservatorio Etneo (INGV-OE) is in charge to monitor Mt. Etna (Catania, Italy), one of the most active volcanoes in Europe. Its activity is characterised by mild strombolian to powerful lava fountains. Monitoring active volcanoes is fundamental to reduce the volcanic hazard, in particular in dense populated areas as it is the case for the Mt. Etna [1]. The combination of different remote sensing systems can improve the analysis of Etna volcanic activity and give a more reliable quantification of volcanic source parameters as the Cloud Height, Mass Eruption Rate, Fine ash Mass and Particle Size. Volcanic source parameters are used as input parameters by volcanic ash transport and dispersal model. A more accurate estimate of these parameters reduces the uncertainty of numerical dispersal model simulations. The data used for this study come from different sources: The VIVOTEK IP8172P is a visible camera located in Catania. The second is a Thermal-Infrared camera located in Nicolosi that collects images (320 x 240 pixels) at few meters resolution [2] [3]. The third instrument is a X-band (9.6 GHz) polarimetric weather radar located nearby the International Airport Vincenzo Bellini (Catania). The fourth is the Spinning Enhanced Visible and Infrared Imager onboard the Meteosat Second Generation Geostationary Satellite [4]. Through the use of complementary remote sensing systems, we aim at improving our understating of explosive phenomena at Etna volcano.

[1] Bonadonna, C., Folch, A., Loughlin, S., & Puempel, H. (2012). Future developments in modelling and monitoring of volcanic ash clouds: outcomes from the first iavcei-wmo workshop on ash dispersal forecast and civil aviation. Bulletin of volcanology, 74 , 1–10.

[2] S. Scollo, M. Prestifilippo, E. Pecora, S. Corradini, L. Merucci, G. Spata, et al., "Eruption column height estimation of the 2011–2013 Etna lava fountains", Ann. Geophys., pp. 57, 2014.

 [3] S. Calvari, G.G. Salerno, L. Spampinato, M. Gouhier, A. La Spina, E. Pecora, et al., "An unloading foam model to constrain Etna’s 11–13 January 2011 lava fountaining episode", J. Geophys. Res. Solid Earth, vol. 116, pp. B11207, 2011.

[4] S. Scollo, M. Prestifilippo, C. Bonadonna, R. Cioni, S. Corradini, W. Degruyter, et al., "Near-Real-Time Tephra Fallout Assessment at Mt. Etna Italy", Remote Sens., vol. 11, pp. 2987, 2019.

How to cite: Romeo, F., Mereu, L., Prestifilippo, M., and Scollo, S.: Etna volcano monitoring by remote sensing systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20022, https://doi.org/10.5194/egusphere-egu25-20022, 2025.

Deception Island, the most active volcanic system in the South Shetland Islands (Antarctica), has recorded over 20 explosive monogenetic eruptions in the past two centuries. The island’s most recent eruption in 1970 was one of its most violent, with a Volcanic Explosivity Index (VEI) of 3. This event generated a column height of up to 10 km and produced an estimated bulk eruptive volume exceeding 0.1 km³, with tephra fallout recorded over 150 km away on King George Island. To investigate the magmatic processes leading up to this significant eruption, we conducted detailed geochemical and textural analyses of near-vent pyroclastic deposits and distal tephra fall-out layers preserved in Livingston Island’s glaciers. Near-vent deposits include dilute pyroclastic density currents (PDCs) and lithic-rich breccias. Olivine crystals in these deposits exhibit two distinct populations: low-forsterite (Fo_65–70 mol.%) and high-forsterite (Fo_80–85 mol.%), with similar CaO contents (0.1–0.5 wt.%) but varying NiO concentrations (0–0.4 wt.% in low Fo; 0.02–0.10 wt.% in high Fo). Pyroxene microanalyses also reveal two distinct populations: i) augite-diopside (En_45–50, Fs_5–25, Wo_38–50) and ii) enstatite (En₉₀, Fs₁₀, Wo₀). Augite-diopside crystals can be further subdivided based on their Mg# (Mg# = Mg/(Mg+Fe) x 100) and TiO₂ contents. The first group shows Mg# values between 80–85 mol.% and TiO₂ ranging from 0.5 to 3.0 wt.%, while the second group displays Mg# values of 55–70 mol.% and narrower TiO₂ concentrations (0.5–1.25 wt.%). Notably, the enstatite population was not found in distal tephra layers. Plagioclase crystals range in composition from Bytownite to Andesine (An_85–40 mol.%). Comparative analyses with distal tephra layers confirm the presence of both olivine populations and overlapping augite-diopside compositions but lack enstatite. Plagioclase compositions show consistency between near-vent and distal deposits. These findings align the 1970 eruption deposits with compositional trends observed in other post-caldera collapse eruptions, shedding light on the island's eruptive history and magmatic evolution.

This work has been partially financed by the grant PID2023-151693NA-I00 funded by MCIN/AEI/10.13039/501100011033.This work is part of the CSIC Interdisciplinary Thematic Platform (PTI) Polar zone Observatory (PTIPOLARCSIC) activities. This research was partially funded by the MINECO VOLCLIMA (CGL2015-72629-EXP) and HYDROCAL (PID2020-114876GB-I00) MICIU/AEI/10.13039/501100011033 research project. Sampling was founded by CICYT (ANT91-1270, ANT93-0852 and ANT96-0734) and MICINN grant CTM2011-13578-E.

How to cite: Albert, H., Ruiz, J. L., Hopfenblatt, J., Pedrazzi, D., Geyer, A., Aulinas, M., Polo-Sánchez, A., Álvarez-Valero, A. M., and Vilanova, O.: Magmatic processes driving the 1970 eruption on Deception Island, (Antarctica), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20055, https://doi.org/10.5194/egusphere-egu25-20055, 2025.

Vulcano Island in Aeolian Archipelago last erupted in 1888-1890 and since then it is affected by an intense fumarolic activity from both the summit crater area of La Fossa volcano and by the hydrothermal system of Baia di Levante located very near to the main settlement of Vulcano Porto.  Ordinary solfataric activity is periodically interrupted by unrest crisis at La Fossa crater associated with increase in fumarole temperature and output, anomalous seismicity, ground deformation and accompanied by an increase in diffuse soil CO₂ degassing at Vulcano Porto. In Autumn 2021 a new major unrest crisis began exposing to a high gas hazard Vulcano Porto settlement due to contemporary dispersion of crater fumarolic plume and diffuse soil CO₂ degassing; Starting from February 2022, with apex in May, a huge increase in gas output of the geothermal system of Levante Bay was observed. The Baia di Levante area is characterized by the presence of a low-temperature fumarolic field (<100°C) either onshore and offshore and fed by a shallow hydrothermal aquifer heated by magmatic gases. A wide diffuse soil CO₂ degassing area extends all over the main beach. The chemical composition of bubbling gases is CO₂-dominant, associated with a 1-3 vol.% of H₂S and minor CH₄ and H₂. The Bay is one of the main sites of attraction for the thousands of tourists who visit the island and given the increased risk for gas emissions and possible phreatic eruptions (due to overpressuration of the geothermal aquifer) we carried out some extraordinary geochemical surveys. These consisted of (i) estimation of diffuse soil CO₂ flux over a target area (154 points over 16,750 m²) established since 2004; (ii) estimation of the convective CO₂ and H₂S flux (the main hazardous gases) from the onshore (50 points in the Mud Pool and surrounding areas) and offshore gas vents (2 main large vents and 60 small vents); (iii) Repeated measurements of the chemico-physical parameters (temperature, pH, Eh, conductivity and dissolved O₂) in the Baia di Levante sea water (107 profiles; water depth from 50cm to 12m). In particular we investigated the areas characterized by the presence of whitish waters, trains of gas bubbles, emissive vents. Results shown significantly increased values ​​compared to the past of the total CO₂ and H₂S output (diffuse and convective) measured on land and at sea surface. The sea water shows the presence of a wide anomalous pH in the near-shore sector between Faraglione and Vent 1 and to a lesser extent to the N of the bay. A wide anomaly of negative Eh values ​​persist at all depths in almost all of the bay. A huge emissions of acid gases from the increased submarine fumaroles alter the chemical-physical parameters of the sea water along the bay. Considering the increased gas hazard the adoption of risk prevention measures was suggested to authorities.

How to cite: Ranaldi, M., Carapezza, M. L., Tarchini, L., Pagliuca, N. M., Pruiti, L., and Sortino, F.: Gas hazard assessment at the hydrothermal system of Baia di Levante at Vulcano Island during the 2021-23 unrest of La Fossa crater (Aeolian Islands, Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20387, https://doi.org/10.5194/egusphere-egu25-20387, 2025.

Natural microseismicity serves as a potent tool for exploring smaller-scale hydrothermal and tectonic phenomena. Investigating seismic activities within the hydrothermal fields of mid-ocean ridges(MORs) offers profound insights into earth's internal dynamics. However, studies on natural earthquakes at ultra-slow spreading ridges, especially the Southwest Indian Ridge (SWIR), remain relatively scarce. To investigate the microseismic distribution, heat flow pathways, and tectonic characteristics of the Longqi hydrothermal field, a typical representative of SWIR, this paper processed one month of passive source OBS data from the DY43 cruise through microearthquake detection and relocation, obtaining a catalog of over 3000 earthquakes, significantly expanding the earthquake database for the Longqi field and improving the magnitude completeness. And the b-value calculation and imaging of the earthquake catalog were carried out using the maximum likelihood method and grid search method, respectively. The research results indicate that: ① The overall b-value of the SWIR Longqi field is 0.989; ② The b-value at the center of the Longqi hydrothermal vent is approximately 0.8, while the b-value around the vent is around 1.2; ③ High and low b-value areas alternate at a depth of 10km along the ridge axis; ④ There is an anomalously low b-value area of around 0.5 at depths of 12-16 km to the north across the ridge axis. Combining previous research results on b-values at MORs, this paper suggests that the background b-value of less than 1 in the Longqi field is consistent with its tectonic-type hydrothermal origin. The detachment fault beneath the Longqi hydrothermal vent leads to high stress and a low b-value, while the microseismic activity around the vent originates from rock fracturing caused by the combined effects of cold seawater and hydrothermal fluids. The uneven distribution of high and low b-values in the deep part of the hydrothermal field may reflect the uneven distribution of subsurface magma. The low b-value area in the north is speculated to be due to high stress resulting from torsional compression at the bottom of the detachment fault. In summary, it can be anticipated that the spatial distribution of b-values will serve as an indicator and reference factor for stress, fault structure, and magmatic-hydrothermal activity in MOR hydrothermal field in the future.

How to cite: wang, K.: Spatial distribution of b-values for microseismicity in the SWIR Longqi hydrothermal field and magmatic-tectonic interpretation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20441, https://doi.org/10.5194/egusphere-egu25-20441, 2025.

Transform faults are often considered to be geometrically simple, nearly linear, vertical structures that localize crustal deformation within a narrow zone surrounding the fault. The deformation kinematics are typically purely strike-slip, parallel to far-field plate motion, with seismic slip above the brittle-ductile transition, near the 600 °C isotherm, which is well predicted by thermal models. Although deviations from these simplified features have been described, much remains to be learned about the seismogenic behavior of transform faults, for example, why they release much less seismic moment than predicted by plate motion models, or why they so rarely produce earthquakes of magnitudes as large as would be expected given their geometric segmentation (>M7). 

The Oriente Transform Fault (OTF) along the southern margin of eastern Cuba, at the boundary between the Caribbean and North American plates, is a particularly relevant example to inform on the seismogenic behavior of transform faults for at least 5 reasons: (1) the OTF geometry changes from a nearly continuous trace along the Cayman Ridge to a highly segmented one westward along eastern Cuba, (2) the geometrically continuous segment was the location of a magnitude 7.8 supershear earthquake in January 2020, (3) GNSS-derived strain measurements indicate that this segmentation variation corresponds to a transition from very shallow (<5 km) mechanical coupling —perhaps creep— of the fault, to complete coupling across the entire crustal thickness (20 km), (4) earthquake hypocenters offshore eastern Cuba locally reach subcrustal depths, (5) earthquake focal mechanisms and offshore geological observations show fault-normal compressional deformation along this purely strike-slip segment.

Here we revisit the offshore trace and seismotectonics of the OTF in light of recent data. We benefit from several oceanographic campaigns in the northern Caribbean, in particular the recent Haiti-TWIST campaign of the Pourquoi Pas? R/V, during which new high-resolution bathymetric and seismic reflection data were acquired, filling several important gaps. We also benefit from recent deformation results from GNSS measurements in Cuba, as well as a new compilation of earthquake moment tensor solutions.

How to cite: Calais, E., Leroy, S., Poort, J., Lebrun, J.-F., Mercier de Lépinay, B., Gonzalez, O., Moreno, B., Granja-Bruna, J.-L., Roest, W., Marcaillou, B., Aiken, C., and Klingelhoefer, F.: Seismotectonics of the Oriente Transform Fault revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20933, https://doi.org/10.5194/egusphere-egu25-20933, 2025.

Subduction zones represent more than half of the total plate boundaries length (38,000 over 64,000km) and cause fast geographic changes by a range of geological processes occurring at local to regional scales such as crustal deformation, volcanism, or dynamic topography. The associated transient changes in land-sea distributions influence the migration, genetic drift, adaptation, speciation, and endemism of the terrestrial biosphere that conquered emerged landmasses. Today, archipelagos located along subduction zones hostone-third of the biodiversity hotspots in the world (Myers et al., 2000). In this context, SUBUTTEC research team aim at combining geological and biological data to unravel the links between the subduction dynamics and terrestrial life in subduction zones based on the case study of the Antilles hotspot. This short and dynamic subduction zone, bounding the east of the Caribbean plate, is ideally circumscribed by two giant continents and two equally giant oceans that provide rather static boundary conditions. To unravel the role of the southern Lesser Antilles in the dynamics of Caribbean biodiversity, we will perform paleogeographic reconstructions over the last 20 Myrs, focused on the unknown role of the southern Lesser Antilles, will be done by integrating tectonics, paleomagnetism, (bio-)stratigraphy and geochronology. We will match these paleogeographic reconstructions with the assemblage distribution and phylogenetic records of extant endemic species, which will allow us to test for alternative scenarios of the temporal dispersion and evolution of life in this highly dynamic hotspot region for both biodiversity and tectonic activity. The implementation of comparative biogeographical methods provides here a powerful tool to reveal natural classification of biogeographic areas i.e. bioregionalization and identification of vicariant events. The joint analysis of the geological and biological records will provide a macro-ecological framework of the biosphere/biodiversity dynamics over subduction zones.

How to cite: Philippon, M., Roncal, J., Cornée, J. J., Quillevere, F., Arcay, D., Cerpa, N., Husson, L., Boucharat, Y., Rousteau, A., Ung, V., Bezault, E., Lorcery, M., Bernet, M., Sarr, A.-C., Riel, N., Kaus, B., Pubellier, M., Thivaiou, D., Montheil, L., and Noury, M. and the SUBUTTEC Team: SUBUTTEC Project: SUBdUcTion triggered Terrestrial Evolution in the Caribbean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20984, https://doi.org/10.5194/egusphere-egu25-20984, 2025.

The Guaymas Basin is a large marginal rift basin in the Gulf of California with ongoing seafloor spreading and strong hydrothermalism centered around two axial troughs. Extremely high concentrations of methane are discharged from diffuse hydrothermal flow, black smokers, and cold seeps. A thick sediment layer across the basin allows for thermocatalytic production of methane in the hot subsurface, resulting in the discharge of hydrothermal fluids from powerful black smokers with temperatures exceeding 300°C. The cooler surface sediments additionally support methanogenesis, providing a complex interplay between the biogenic and abiogenic systems. The dynamism of the Guaymas Basin means that the flux and distribution of hydrothermal vents in this region can change rapidly, impacting the wider oceanography of the region.

We present here results from a 2024 study of hydrothermalism in the Guaymas basin using a new optical sensor, developed at the Woods Hole Oceanographic Institution. SAGE – the Sensor for Aqueous Gases in the Environment – utilizes laser absorption spectroscopy through a hollow core optic fiber to quantify the partial pressure of dissolved methane extracted from the deep sea. This in situ sensor, deployed during a cruise on the R/V Atlantis allows continuous measurement of methane concentrations with high spatiotemporal resolution, with a sampling rate of 1Hz and a stable response time of 1-5 minutes. This new sensing technique facilitated analysis of the relationships between microbial communities and hydrothermalism and guided dives towards hydrothermal vents based on the real-time methane concentration. It also allowed the comprehensive in situ analysis of a rapidly evolving black smoker vent site in the northern axial trough, allowing the methane export to the water column to be characterized with high spatiotemporal resolution. The low detection limit of SAGE – down to ~10 ppm – allows the analysis of the broader impact of these dynamic methane-based systems into the wider oceanography of the region.

How to cite: Michel, A., Burkitt-Gray, M., Marquardt, S., Youngs, S., Remar, J., Joye, S., and Kapit, J.: Chemical mapping of methane in the Northern Guaymas Basin hydrothermal field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21421, https://doi.org/10.5194/egusphere-egu25-21421, 2025.

The continent-derived nature of the western Philippines (Palawan-Mindoro Microcontinental Block; PCB) contrasts with the island arc-dominated eastern Philippines (Philippine Mobile Belt; PMB). Petrological investigation on the P-T-D history of the metamorphosed rocks in between these two terranes and how they relate to the broader tectonic events are however lacking. In this study, we examined rock units related to the arc-continent collision events in two areas: the Romblon Island Group and the central Zamboanga Peninsula.

In central Philippines, the Romblon Metamorphic Complex (RMC) represents the PCB-derived materials. The RMC consists of metapelitic and metapsammitic paraschists in Tablas, Romblon, and Sibuyan with minor orthoschists and marbles. Using two-feldspar geothermometery, and Raman Spectrometry of Carbonaceous Material, the temperature variations revealed a low P/TStage 1 metamorphism of all RMC units with peak T and P values of about 450-540°C at <5 kbars. Based on tensional structures (e.g. boudins) and preserved metapelitic-metapsammitic interlayering, we attribute this Stage 1 to the PMB continental rifting and subsequent shallowing of the paleogeothermal gradient. The RMC paraschists which are adjacent to the Sibuyan Ophiolite  Complex (SOC) meanwhile register significantly higher T at the same low P conditions (= 570-630 °C). This suggests a second stage of higher T deformation and metamorphism directly linked with the juxtaposition of the continental RMC and the island arc SOC. This is consistent with the subsolidus shearing and metamorphism of the isotropic gabbro units of the SOC with preserved P-T conditions of about 500-800°C.

The southern extension of the PCB-PMB collision is even less understood although earlier works extend the arc-continent suture zone in Mindanao Island, southern Philippines. The purported boundary of the continent-derived Zamboanga Peninsula and the island arc Eastern Mindanao is the northwest-southeast trending Siayan-Sindangan Suture Zone. Our field mapping in central Zamboanga Peninsula however revealed a distinct northeast-southwest trending suture zone of an apparent arc-continent collision zone. Across this NE-SW suture zone, the lithologies progress from the paraschists of the Gutalac Metamorphic Complex (GMC) in the northeast to the amphibolites of the Dansalan Metamorphic Complex (DMC). Further southeast, the residual peridotites and pillow lavas with intercalated chert, deep marine turbidites and limestones of the Polanco Ophiolite Complex (POC) are exposed. Such progression hints at a NE-SW convergence of an ancient arc (POC) with its metamorphic sole (DMC) against the continent-derived GMC following the consumption of an ancient oceanic basin.

How to cite: Valera, G. T., Badillo, J. K., Tabilog, A. E. S., Balanial, N. M., Alcancia, M. L., and Payot, B. D.: Understanding the arc-continent collision zones in western Philippines: Novel insights from the Romblon Island Group and the Central Zamboanga Peninsula, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21462, https://doi.org/10.5194/egusphere-egu25-21462, 2025.

The eastern Liaoning-southern Jilin tectonic zone (also referred to as the Liao-Ji tectonic zone), a potential zone for rare-metal and REE mineralizations in China, hosts over 10 rare-metal and REE deposits and ore occurrences with varying scales and mineralization characteristics, which establish this zone as an ideal target for research on the metallogenic regularities of rare-metal and REE mineralizations.The study area resides in the northern part of the East Asian continental margin, lying on the overlapping part of the North China and the Western Pacific Plates, is located in the northeastern North China Plate, consisting of the North China Craton and the north margin orogen of the North China Plate. This area serves as a critical large-scale copper-gold and polymetallic mineral resource base in China, also providing favorable geologic conditions for the enrichment and mineralization of rare metals and REEs. So far, many rare-metal and REE deposits and ore occurrences have been discovered in the Liao-Ji tectonic zone, including two large Nb-Be-Zr-REE deposits (i.e., Lijiapuzi and Pianshishan), two medium-sized Rb-Be-Nb-Ta-REE deposits (i.e., Saima and Gangshan), one small Nb-Ta-REE deposit (i.e., Shijia), and over 10 rare metal-REE ore occurrences (e.g., Xiaolizi, and Baiqi), suggesting considerable mineralization potential. Most of the deposits in the Liao-Ji tectonic zone are closely associated with alkaline rocks.

Extensive field surveys and geochemical studies of the above deposits reveal that the ore-forming rock masses of the Pianshishan, Gangshan, and Lijiapuzi deposits include alkaline granites and pegmatites and those of the Shijia and Saima deposits are quartz syenites and aegirine nepheline syenites, respectively. The Pianshishan (67±2.2 Ma) and Gangshan (110±1.2 Ma) deposits were formed during the Yanshanian, the Shijia (226.3±2.4 Ma) and Saima (224.4±6.1 Ma) deposits originated from the Late Indosinian magmatism, while the formation of the Lijiapuzi deposit (2501±11 Ma) was associated with the Lvliang Movement. Therefore, the study area underwent three stages of regional rare-metal and REE mineralizations: the Late Yanshanian (Mesozoic), Late Indosinian (Mesozoic), and Proterozoic Lvliangian mineralizations. The petrogeochemical analysis indicates that the ore-forming rock masses of several typical deposits all belong to the metaluminous, alkaline - calc-alkaline, and tholeiitic basalt series, sharing similarities with the elemental geochemical characteristics of intraplate rift rock series and rocks in an extensional environment under plate subduction. The rare-metal and REE mineralizations in the study area were primarily governed by the evolution and crystallization differentiation of alkaline magmas. Given that the alkaline magmatic rocks were all formed by crust-mantle contamination, this study posits that the enrichment and mineralization processes of rare metals and REEs in the Liao-Ji tectonic zone are intimately associated with the highly evolved alkaline magmas. Under the action of water and volatile constituents, magmas underwent intense fractional crystallization, leading to the migration and accumulation of ore-forming elements. With changes in ore-forming conditions such as temperature and pressure, ore-bearing fluids became enriched and mineralized in the late stage of magmatism with the crystallization of primary rock-forming minerals.

How to cite: Ju, N., Yang, G., Zhang, P., Li, J., Wu, Y., Lu, S., Liu, B., Yang, X., Liu, X., and Feng, Y.: Rare-metal and rare earth element mineralizations in the eastern Liaoning-southern Jilin tectonic zone in Northeast China: A review, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2404, https://doi.org/10.5194/egusphere-egu25-2404, 2025.

The second member of the Fengcheng Formation in the early Permian of the Mahu Depression has a rock series with interbedded alkali mineral layers and tuffaceous layers. The dark layer contains a large amount of associated metal minerals, which are closely related to the volcanic hydrothermal material at the Fengnan fault nose. However, due to the presence of detrital rock deposits on the west side of the Mahu Depression, this area is jointly controlled by volcanoes and terrestrial sources to form alkali mineralization. There are also a large number of dark hydrocarbon source rocks developed in the region, which are also one of the reasons for the mineralization of alkali minerals and associated metal minerals. Therefore, a mineralization model is established.

How to cite: Liu, X. Y., Longwei, Q., and Yongqiang, Y.: Enrichment Factors of Alkali and Key Metal Mineral Resources in Fengcheng Formation of Mahu Sag, the Junggar Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2960, https://doi.org/10.5194/egusphere-egu25-2960, 2025.

The Global Navigation Satellite Systems - Interferometric Reflectometry (GNSS-IR) method has been utilized for nearly fifteen years as an alternative and cost-effective approach to determine hydrological parameters such as sea level, snow depth, and soil moisture through the analysis of signal-to-noise ratio (SNR) data. Most GNSS-IR studies to date rely on archived data and post-processed results. However, the potential for near real-time GNSS-IR analysis is increasingly being explored. In this study, high-rate GNSS archive data, sampled at 1-second intervals and stored in 15-minute files, were processed in a simulated near real-time workflow. Every 15 minutes, new data were added to the analysis, focusing exclusively on the most recent 60 minutes of observations. A novel approach for detecting outliers in near real-time GNSS-IR estimates was also proposed. The median-based robust outlier detection (ROD) method, previously validated for post-processed GNSS-IR snow depth results, was adapted and applied to near real-time GNSS-IR data. A 30-day dataset of multi-GNSS, multi-frequency SNR observations from the Portland (PTLD) GNSS station in Australia, collected in November 2024, was analyzed. The near real-time GNSS-IR results were validated using sea level measurements from the PORL tide gauge station. The results demonstrate that the modified ROD approach can be used to identify outliers in near real-time GNSS-IR sea level retrievals.

How to cite: Altuntas, C., Erdogan, B., Tunalioglu, N., and Williams, S.: Improving near real-time GNSS-IR sea level retrievals with robust outlier detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3157, https://doi.org/10.5194/egusphere-egu25-3157, 2025.

The bauxitic region of Sumbi and its surroundings in Kongo Central (DR Congo) is located in an area corresponding to “bands” of basic rocks made up of microdolerites, basalts and andesites. The problem of this study is linked to the similarity of the phenomena that generated the depositional process of these ferruginous and aluminous formations. The aim of this article is to carry out a chemical and petrographic study of samples of bauxitic materials from the Mayedo and Kinzoki regions, with a view to their possible recovery. To this end, the chemical and petrographic analysis of the weathering formations outcropping in the study area was carried out using X-ray fluorescence and thin section methods. The latter revealed that two lithologies were detected in the healthy rocks: basalts with a mineralogical assemblage of plagioclase crystals, pyroxene microcrystals and oxide opaques; and dolerites represented by plagioclase crystals, pyroxenes and a few quartz crystals. X-ray fluorescence revealed high levels of Al₂O₃ (32.69%) in the Mayedo zone (MHb1). This visibly gibbsite-rich level corresponds to the zone of friable, homogeneous bauxite with a massive, blood-red texture, with an estimated gibbsite percentage of 55.50. The percentage of Fe₂O₃ is high in these zones at 42.77%, hence the dark red colour, reflecting a strong zone of ferruginasation. This horizon contains a high concentration of hematite and goethite minerals. Highly variable SiO₂ contents ranging from 13.48% to 40.82%. These variations are essentially due to the dissolution of silica by leaching and resilification.

How to cite: Mwanakangu, E. and Ungu, D.: Petrographic and Geochemical Characterization of Mayedo and Kinzoki Ranges (Sumbi Bauxite Region, Kongo Central/DR Congo), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3874, https://doi.org/10.5194/egusphere-egu25-3874, 2025.

High-precision GNSS coordinate time series modeling and prediction provide a critical reference for applications such as crustal deformation, structural safety monitoring, and regional or global reference frame maintenance. A Deep neural network framework based on Transformer was applied to 22 GNSS stations, each with 1000 days, in which data is preprocessed using a synchronization sliding window. The overall fitting and prediction trends exhibit a high degree of consistency with the original time series. The average fitting RMSE and MAE are 3.40 mm and 2.64 mm, respectively, while the corresponding average prediction RMSE and MAE are 3.54 mm and 2.77 mm. In comparison to the LSTM model, the proposed method achieved a redu78ction in RMSE and MAE by 20.7% and 19.6%, respectively. Furthermore, when benchmarked against the traditional least squares approach, the improvements were even more pronounced, with RMSE and MAE decreasing by 35.7% and 37.8%, respectively. The approach demonstrates robustness and effectiveness under conditions of discontinuous data. Therefore, it could be used as a convenient alternative to predict GNSS coordinate time series and will be of wide practical value in the fields of reference frame maintenance and deformation early warning.

How to cite: Wang, J., Li, Z., and Jiang, W.: Deep Neural Networks for GNSS Coordinate Time Series Modeling and Prediction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4633, https://doi.org/10.5194/egusphere-egu25-4633, 2025.

The Vemula-Velpula hydrothermal barite deposit is hosted by mafic dykes (ca. 1850 Ma. [1]) intruding into the uppermost part of about 1900 m thick carbonate strata of the Vempalle Formation (ca. 2000 Ma. [2]) in Cuddapah basin and occurs as fracture-fill and breccia-fill veins. The veins dominantly consist of barite with minor quartz. The host mafic rock has undergone various extents of hydrothermal alteration, due to which the primary calcic plagioclase-clinopyroxene assemblage is altered to albite and clinochlore, along with the introduction of secondary epidote, quartz, and calcite. The wide range in Ba concentration of mafic rock (68 to 3012 ppm) associated with the barite mineralization indicates that Ba was mobilized and subsequently leached from the mafic rock by the hydrothermal fluid during this alteration event. The δ³⁴S values of barite range from +16.19 to +23.24‰ which falls within the range of δ³⁴S value of +10 to +30‰ estimated for Proterozoic seawater [3]. At shallow crustal depth where this deposit was formed, direct participation of seawater is unlikely and therefore basinal brine is inferred to be the source of sulphate ion required for barite mineralization. Primary aqueous biphase fluid inclusions in barite have homogenization temperatures ranging from 180 to 300 °C, with most of them clustering in the range 220-250°C, and salinities ranging from 2.4 to 25.8 wt.% NaCl equivalent. The first ice melting temperature of these inclusions was measured between -55 and -37°C, broadly pointing towards an H₂O-NaCl-CaCl₂ fluid system. Petrography and microthermometric data of fluid inclusions indicate the involvement of two fluids of different salinities, which, upon mixing and cooling, led to barite precipitation.

This research work was funded by SERB, New Delhi (Scheme No. CRG/2019/001015).

References

[1] Chakraborty K. et al. (2016), Journal of the Geological Society of India 87, 631–660.

[2] Rai A.K. et al., (2015), Journal of the Geological Society of India 86, 131–136.

[3] Strauss H (1993) Precambrian Research 63(3–4), 225–246.

How to cite: Devanand Sreekala, D. and Muthusamy, S. P.: Insight into the genesis of barite deposit in Vempalle Formation, Cuddapah basin, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4666, https://doi.org/10.5194/egusphere-egu25-4666, 2025.

Direct ore-mineral U-Pb geochronology of scheelite (CaWO₄), cassiterite (SnO₂), and wolframite ([Fe,Mn]WO₄) using recently-developed reference materials led to new ore-genesis insights for multiple worldwide W-Sn/rare metal deposits. Scheelite from the Yellow Pine epithermal Au-W-Sb deposit in Idaho, USA was age dated using U-Pb via isotope dilution thermal ionization mass spectrometry (TIMS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). These analyses provided both the first age constraints on the tungsten mineralization (ca. 57 Ma) and a scheelite U-Pb reference material (NMNH-107667; 57.52 ± 0.22 Ma). The data reveal ore mineralization occurred in numerous discrete pulses during crustal uplift, which contrasts with the previous two-mineralization-event model.

The Yellow Pine scheelite reference material enabled U-Pb scheelite geochronology via LA-ICP-MS for multiple other deposits worldwide; namely, the polyphase stratabound scheelite-ferberite mineralization hosted within Fe-rich magnesite zones and marbles in two locations around Mount Mallnock, Austria. Two unexpected but geologically meaningful age dates (294 ± 8 Ma) for Mallnock West and (239 ± 3 Ma) for Mallnock North revealed for the first time that ore mineralization occurred during an extensional geodynamic setting as part of the breakup of Pangea, as opposed to the previous model invoking the older compressional tectonics of the Variscan orogeny.

Combining direct-ore geochronology methods for several ore minerals was particularly powerful for Sn- and W-bearing deposits in southeast Australia. A U-Pb cassiterite age date (435 ± 2 Ma) revealed the tin-bearing lithium pegmatites of the Dorchap Dyke Swarm are ca. 15 Ma older than some previous estimates suggesting mineralization was related to the earliest magmatic activity recorded in the Wagga-Omeo Metamorphic Belt. Additionally, a new U-Pb wolframite age date (395 ± 5 Ma) for the Womobi polymetallic (W-Mo-Bi) deposit is ca. 21 million years younger than the host Thologolong granite, suggesting the granite was a passive host that was mineralized by a concealed intrusion. Both instances revealed mineralization ages that were significantly different than previously accepted. More widespread application of these increasingly diverse, direct-ore geochronology methods stand to replace uncertain spatial or textural associations, thereby providing an opportunity to significantly improve ore genesis models.

How to cite: Wintzer, N., Holm-Denoma, C., Altenberger, F., and Waugh, S.: W-Sn Ore-Mineral Geochronology: New Ages Improve Genesis Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5245, https://doi.org/10.5194/egusphere-egu25-5245, 2025.

The relationship between the length of day (LOD) and the El Niño-Southern Oscillation (ENSO) has been extensively studied since the 1980s. LOD represents the negative time derivative of UT1-UTC, directly proportional to the Earth Rotation Angle (ERA), a key Earth Orientation Parameter (EOP).

ENSO is a climate phenomenon occurring in the tropical eastern Pacific Ocean that primarily impacts the tropics and subtropics. Extreme ENSO events can lead to severe weather conditions, such as flooding and droughts, across various regions worldwide. ENSO event undergoes a lengthy incubation period, during which the interannual variations in length-of-day (LOD) and atmospheric angular momentum (AAM) are rapidly influenced by the interactions between the ocean and the atmosphere.

The significant characteristics of climate change are the rise of global temperature and sea level, which are driven by ENSO. Interannual oscillations in global mean sea temperature (GMST) and global mean sea level (GMSL) might also impact changes in the Earth’s rotation velocity.

The goal of this study is to explain in more detail connections among the interannual (2-8 years) variations of the LOD, AAM, and different climate indices, like the Southern Oscillation Index SOI, Oceanic Niño Index ONI, GMSL, and GMST. The influence of climate signatures on LOD from January 1976 to December 2024 is assessed using semblance analysis based on continuous wavelet transform. This method evaluates the correlation between climate time series in the time and wavelength domains.

Studying the relationship between LOD, AAM, GMSL, GMST, and ENSO indices enhances our understanding of Earth's dynamic system, improves geophysical models, and increases the precision of applications dependent on accurate timekeeping and Earth rotation measurements.

How to cite: Wińska, M., Śliwińska-Bronowicz, J., Nastula, J., and Staniszewska, D.: Length of the Day changes and climate signatures- their relations in detected ENSO Events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8007, https://doi.org/10.5194/egusphere-egu25-8007, 2025.

Anelasticity is a type of rheology intermediate between elasticity and viscosity, responsible for rock’s transient creep behaviour. Whether to consider anelasticity in geodynamic processes operating outside the seismic frequency band which likely involve transient mantle creep is still under debate. Here, we focus on the geodynamic process of ocean tide loading (OTL), namely the deformational response of the solid Earth to the periodic ocean water-mass redistributions caused by astronomical tides. By analysing high-precision Global Positioning System (GPS) data from over 250 sites in western Europe and numerical OTL values from advanced three-dimensional Earth models, we unambiguously demonstrate anelastic OTL displacements in both the horizontal and vertical directions. This finding establishes the need to consider anelasticity in geodynamic processes operating at sub-seismic timescales such as OTL, post-seismic movement, and glacial isostatic adjustment (GIA) due to rapid ice melting. Consequently, to construct a uniform viscoelastic law for modelling Earth deformations across multiple timescales anelasticity must be incorporated. Our best-fitting anelastic models reveal the shear modulus in Earth’s upper mantle to be weaker at semi-diurnal tidal frequencies by up to 20% compared to the Preliminary Reference Earth Model (PREM) specified at 1 Hz, and constrain the time dependence of this weakening.

How to cite: Huang, P., Penna, N. T., Clarke, P. J., Klemann, V., Martinec, Z., and Tanaka, Y.: Signature of mantle anelasticity detected by GPS ocean tide loading observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9320, https://doi.org/10.5194/egusphere-egu25-9320, 2025.

This study investigates the present-day seismotectonic framework of the High Atlas Mountains, Morocco, with a specific focus on the area affected by the devastating Mw 6.8 Al Haouz earthquake of September 8, 2023. Leveraging a high-resolution seismic dataset encompassing over twenty moderate earthquakes (M 3.5-6.8) recorded by regional networks between 2008 and 2024, the research aims to refine earthquake locations and characterize the regional stress field. Initially located using P-wave arrival times, earthquake hypocenters were subsequently relocated using the double-difference method, which yielded more precise locations by minimizing travel-time residuals between pairs of events recorded at common stations. The high degree of agreement between the initial and relocated solutions validates the robustness of the location estimates. Notably, the observed seismicity is confined to shallow crustal depths, consistently shallower than 30 km, corroborating the shallow rupture observed for the Al Haouz earthquake, which occurred at a depth of approximately 31 km. This shallow seismicity suggests a shallow deformation style within the High Atlas.

To determine the state of the present-day tectonic and stress regimes across the western and central segments of the High Atlas, the study uses two complementary approaches: regional seismic moment tensor inversion and P-wave first motion focal mechanism analysis. Fault plane solutions were calculated using P-wave first motion polarities and further constrained through regional moment tensor inversion. The majority of analyzed earthquakes exhibit reverse faulting mechanisms, often with a significant strike-slip component, indicating a complex deformation pattern. Analysis of the principal stress axes (P, B, and T) derived from the focal mechanisms reveals average orientations of 16/189, 39/036, and 08/104 (plunge/azimuth), respectively. Subsequently, tectonic stress tensor properties were derived through inversion of the focal mechanism parameters. The results of this stress inversion indicate a predominantly N-S oriented maximum horizontal stress (σ1) in the Western High Atlas, closely aligned with the faulting style of the Al Haouz earthquake. In contrast, the stress field in the Central High Atlas exhibits a transition to a NW-SE to NNW-NNE orientation of σ1. These spatially varying stress orientations are consistent with independently derived GPS velocities and available neotectonics data, which document ongoing shortening across the High Atlas. This integrated analysis provides a comprehensive understanding of the active tectonic deformation within the High Atlas, shedding light on the complex interplay of faulting styles and stress orientations, and providing crucial insights into the source mechanism and broader tectonic context of the Al Haouz earthquake within the Western High Atlas region.

How to cite: Oujane, B., El Moudnib, L., Zeckra, M., Badrane, S., and Nouayti, A.: Seismotectonics of the Intracontinental High Atlas Mountains, Morocco, Derived from Regional Seismic Moment Tensor Analysis: Insights into tectonics and stress regimes., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9503, https://doi.org/10.5194/egusphere-egu25-9503, 2025.

North East India (NEI) is situated between the Himalayan collision arc to the north and the Indo-Burmese Ranges (IBR) to the east. The tectonic unit of the NEI, Shillong Plateau (SP), is one of the most active seismotectonic zones of the Indian subcontinent, as demonstrated by its seismicity. It is crucial to identify active faults in populated areas for human safety and the sustainable development of society. The gravity method is one of the convenient methods to delineate the shallow to deeper subsurface discontinuities, i.e., it is useful to detect active faults in the subsurface compared to other geophysical methods (e.g., Electrical, and Electromagnetic methods). In this study, detailed multilayer horizontal tectonics stress (HTS) was calculated using the approach of multi-scale decomposition of gravity anomalies data. HTS can be helpful in demarcating shallow to deep-seated tectonic structures. The tectonic features exhibit a strong correlation with the distribution of HTS at different depths. Major faults and earthquake epicentre align with areas of high stress, while stable zones correspond to regions of low stress. It means that HTS is employed to deduce the distribution and stability of faults. The high value of HTS is increased from shallow to deep depths for SP, Mikir Hills, IBR and Eastern Himalaya in the NEI region, and it varies as ~ 0.2-0.53 MPa, ~ 0.24-0.61 MPa, ~ 0.3-0.84 MPa, ~ 0.4-1.2 MPa, ~ 0.57 1.86 MPa, ~ 0.8-2.4 MPa, ~ 0.84-3.0 MPa at 4, 8, 12, 20, 40, 50, and 60 km depths, respectively. While the Brahmaputra Valley and the Surma Basin show relatively less stress, where HTS varies between ~ 0.1-0.33 MPa for 4, 8, 12, 20, 40, 50, and 60 km depths. It can be interpreted that the populated SP and Mikir Hills are highly unstable or earthquake-prone regions due to high stress.

How to cite: Pathak, P. and Kumar Mohanty, W.: Horizontal tectonic stresses and its implications in the Shillong Plateau and its adjoining using gravity data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9618, https://doi.org/10.5194/egusphere-egu25-9618, 2025.

The Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC) aimed to evaluate and compare various methods of Earth Orientation Parameters (EOP) predictions. One of the goals of the 2nd EOP PCC was to prepare a combination of the predictions to obtain one robust and accurate solution for forecasts of individual parameters. This presentation focuses on identifying the most reliable and accurate combination of predictions for polar motion (PMx, PMy), universal time variations (UT1-UTC), and length of day (LOD) among the methods tested during the 2nd EOP PCC.

Two types of experiments were designed for this study: "operational" combinations tailored to real-time comparisons and practical application and "final" combinations designed for comprehensive analysis. Boths approaches incorporated six methods for handling outlier predictions, ranging from no filtration to progressively stricter criteria using the σ+β method (with α values ranging from 5 to 1). All experiments cover the period of 2nd EOP PCC (from September 1, 2021, to December 31, 2022), and each approach includes 70 10-day predictions.

The results show that combining various submissions generally enhances stability and accuracy of EOP forecasts. The σ+β criterion with α = 1 achieved the smallest Mean Absolute Prediction Error, indicating high accuracy of prediction. However, this method of eliminating outliers forecasts is the most restrictive, as it excludes a significant number of predictions. In contrast, operational combinations without filtering proved more practical for real-time applications, albeit with slightly higher errors.

The findings underscore the importance of tailoring combination strategies to specific goals—whether prioritizing maximum accuracy or practical applicability. This research highlights the benefits of prediction combination methods in improving EOP forecasts, offering a foundation for further development of operational strategies and expanding their use in geophysical and astronomical applications.

How to cite: Michalczak, M., Śliwińska-Bronowicz, J., Wińska, M., Partyka, A., Ligas, M., and Nastula, J.: Exploring various approaches to combine Earth Orientation Parameter (EOP) predictions gathered during the Second EOP Prediction Comparison Campaign (2nd EOP PCC), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9658, https://doi.org/10.5194/egusphere-egu25-9658, 2025.

This study introduces a methodology designed to enhance the accuracy of Celestial Pole Offset (dX, dY) prediction, with a focus on a short-term forecast horizon (up to 30-days). IERS EOP final data as well as those published by JPL are used as input for the  prediction algorithms. The prediction procedure is consistent, in the sense that, it does not rely on any external data to fill any latency gaps in the final IERS product. This is handled within the prediction routine itself by enlarging the forecast horizon to the gap filling horizon and proper forecast horizon. In this way, the presented methodology is ready to use under operational settings what makes it well suited for real time applications. Such an approach enables also to asses prediction capabilities of the methods in offline experiments whilst maintaining the operational settings. JPL CPO data serves as supplementary series for prediction and adjusting using Deming regression to align it  with IERS CPO values (attempt to assess fixed and proportional biases between series). The prediction strategy applies also the Whittaker-Henderson smoother to IERS CPO series, which after smoothing is treated as an additional source of information in the prediction process. Separate predictions based on JPL, IERS and smoothed IERS series are also averaged in different combinations giving rise to ensemble data-based prediction model. In this way we show that the overpredictive and underpredictive characteristics of specific input data, even with the application of a single prediction method, can result in a more precise and accurate final forecast. The presented approach was tested against the results obtained within the course of the 2^nd EOPPCC, as well as other contemporary studies. This presentation includes also a comparison of performance of the method in reference to different series, i.e., IERS EOP 14 C04 and IERS EOP 20 C04.

How to cite: Ligas, M., Michalczak, M., Belda, S., Ferrándiz, J. M., Karbon, M., and Modiri, S.: Enhanced Celestial Pole Offset forecast via combination of different data sources, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11708, https://doi.org/10.5194/egusphere-egu25-11708, 2025.

Geodetic VLBI (Very Long Baseline Interferometry) currently consists of two observing networks (legacy S/X and broadband VGOS). Heretofore, the two networks have run rather independently, which is non-ideal. There have been several attempts to combine observations from both networks at sites with co-located antennas using either conventional local-tie surveys or VLBI tie-sessions between S/X and VGOS, or both. Unfortunately, the number of sites with co-located VLBI antennas is rather limited, which hampers progress. To overcome this problem, we proposed an approach, the so-called mixed-mode VLBI tie session, that does not require to have co-located VLBI antennas. Instead, mixed-mode sessions have the S/X and VGOS networks observed simultaneously as a single geodetic VLBI technique to thus obtain global ties between the two networks. Two of the sessions observed in 2020 were already included in the ITRF2020 combination. We hypothesize that the global-tie approach helps preserve the geometry of the networks when aligning with the state-of-art ITRF2020 frame. In this presentation, we will describe the observed mixed-mode sessions, detailing scheduling strategies, correlation techniques, and geodetic processing methods used. We will also demonstrate how mixed-mode sessions can help realize a stable global geodetic reference frame such as the ITRF.

How to cite: Mondal, D. R., Elosegui, P., Ruszczyk, C., Lemoine, F., and Behrend, D.: Global VLBI ties using mixed-mode sessions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12533, https://doi.org/10.5194/egusphere-egu25-12533, 2025.

The progressive development of navigation technology has significantly improved real-time positioning accuracy, addressing the needs of modern applications. GNSS (Global Navigation Satellite System) is the primary system used for precise positioning across various platforms. However, GNSS is susceptible to errors, particularly interference, which degrades signal quality and compromises accuracy. Auxiliary systems such as INS, gyroscopes, and map-matching algorithms enhance reliability during interference but depend on GNSS for initialization. Signal detection algorithms, often employing CRPA (Controlled Reception Pattern Antennas) and advanced computational techniques, are essential for mitigating the impact of interferences and ensuring reliable navigation. This study compares the performance of two CRPA systems with different GNSS modules and algorithms, subjected to spoofing-jamming interference during experiments. The first CRPA, integrated with the u-blox ZED-F9P module, supports GPS, BeiDou, and Galileo satellites, employing an adaptive notch filter and pulse blanking. The second CRPA, featuring the Unicore UM980 module, supports GPS, BeiDou, and GLONASS satellites, utilizing a space-time algorithm alongside the JamShield adaptive mechanism for interference mitigation. In this study, real-time measurements were conducted on a car-mounted device platform under normal operating conditions. The platform was tested stationary for 5 minutes, followed by 15-minute intervals at speeds of 60 km/h. During each interval, 5 minutes of jamming and 5 minutes of spoofing were applied, with independent spoofing signals introduced. Jamming signals reached up to 50 dB-Hz, and spoofing signals were applied at levels up to 32 dB-Hz using a specialized interference device. During constant-speed travel, the second CRPA tracked 28 satellites with an HDOP of 0.5, while the first CRPA tracked 23 satellites with an HDOP of 0.75. Under jamming conditions, The second antenna maintained consistent satellite visibility, whereas the first experienced a pronounced decline in the number of observable satellites. Similarly, spoofing had no adverse effect on the second antenna, but the first suffered reduced satellite counts and positional accuracy. Additionally, the first antenna consistently underestimated the vehicle’s speed by approximately 5 km/h and exhibited a speed fluctuation of 0.5 m/s under interference conditions. 

How to cite: Karlitepe, F., Sezen, S., Velibasa, B. E., and Kabalci, A.: Advancements in Navigation Technology and Robustness Against GNSS Interference: A Comparative Analysis of CRPA , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12972, https://doi.org/10.5194/egusphere-egu25-12972, 2025.

The need to improve Earth rotation theories and models in a consistent and accurate
manner is currently widely recognized. Several researchers and groups at different
institutions have been working on this problem using quite different approaches, either
from the theoretical or computational perspective.
A potential source of the loss of accuracy of celestial pole offsets can be due to the
mismodeling of the planetary component of the IAU2000 nutation series. In fact, as
recognized in Ferrándiz et al. (2018), this component is actually based on a rigid-Earth
solution and does not include the Oppolzer terms that are significantly affected by the
Earth non-rigidity.
Such hypothesis was showed to be realistic by adjusting directly the amplitudes of a
small number of nutation periods of strictly planetary origin that could be reasonably
well separated by analyzing the series of VLBI observations. The results provide
significant fittings and the WRMS was successfully decreased by amounts comparable
to those achieved with lunisolar amplitude rescaling. A further step in this direction
requires the consideration of theoretical developments for the amplitudes of the non-
rigid Earth planetary nutations.
In this contribution, we present preliminary results considering the analytical formulae
of such planetary amplitudes for a two-layer earth model including dissipation effects at
the core-mantle boundary and anelasticity, obtained from a Hamiltonian method. Their
performance is assessed using several series of VLBI observations, with satisfactory
results, and is placed in the general context of the improvement of the precession and
nutation models sought by the IAG and the IAU.
Acknowledgment. This research was supported partially by Spanish Projects PID2020-119383GB-I00 funded by
Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033); SEJIGENT/2021/001, funded by
Generalitat Valenciana; and the European Union—NextGenerationEU (ZAMBRANO 21-04).

How to cite: Zerifi, A. Z., Ferrándiz, J. M., Escapa, A., Baenas, T., Juárez, M. A., Belda, S., and Karbon, M.: Performance of a new set of analytical corrections to planetary nutations: preliminary results and outlook, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13099, https://doi.org/10.5194/egusphere-egu25-13099, 2025.

The rapidly changing climate is amplifying both the frequency and severity of extreme weather events in the Azores archipelago, Portugal. Understanding the underlying dynamics of these events is essential for effective mitigation. Atmospheric water vapor data derived from the Global Navigation Satellite System (GNSS) data and reanalysis outputs from an atmospheric general circulation model offer valuable tools for studying the behavior of weather fronts around the Atlantic Ocean environment of the Azores. This research aims to conduct a detailed comparison between GNSS-based measurements and atmospheric reanalysis data, such as those available from ERA/MERRA2, focusing on the detection of small-scale atmospheric structures with high temporal resolution. We utilize atmospheric reanalysis products to decode long-term trends in the frequency and severity of extreme weather events in the Azores. We then apply statistical methods to identify consistencies and differences between these two approaches in capturing atmospheric water vapor patterns. By combining water-vapor estimates from both GNSS data and atmospheric reanalysis, we are able to characterize the dynamics of atmospheric turbulence from small (few meters) to large (few tens of kilometers) scales. 

How to cite: Ramrajvel, N., Mondal, D., Elosegui, P., Paine, S., Mateus, P., and Mendes, V.: Decoding the signal of extreme weather events in the Azores archipelago using GNSS and atmospheric reanalysis products, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13415, https://doi.org/10.5194/egusphere-egu25-13415, 2025.

Abstract.

The Isiro and Ngayu belts in northeastern Democratic Republic of Congo (DRC) are part of the Congo Craton and among the most poorly known Archean terrains worldwide. These belts consist of metavolcanic and metasedimentary rocks surrounded or intruded by granitoid rocks. minimum age of deposition for the supracrustal formations is defined at ca 2633 Ma (e.g. Allibone et al., 2020), whereas the granitoids were dated between 3200 Ma and 2530 Ma (Allibone et al., 2020; Turnbull et al., 2021) and are strongly deformed with variable proportions of mafic enclaves at outcrop scale (Turnbull et al., 2021). Both Isiros and Ngayu belts host important gold deposits, but the genetic relationships between gold mineralization, deformation and the diverse host rocks remain ambiguous. In this context, the work we present here is part of a multidisciplinary approach, combining the processing of satellite images and field observations using GIS to map the structural lineament that may control gold mineralization in the region. The results show that the strains are large, marked by NW-SE lineaments at low angle to the belt strikes and combined with a secondary ENE-WSW brittle structure. The overall structural pattern, together with the existence of artisanal gold mining in the area, emphasizes that gold mineralization is largely controlled by structures localization along the greenstone belts.

Key words: Congo craton, gold mineralization, field observations, satellites images, structural lineaments.

Reference

Allibone, A., Vargas, C., Mwandale, E., Kwibisa, J., Jongens, R., Quick, S., Komarnisky, N., Fanning, M., Bird, P., MacKenzie, D., Turnbull, R., Holliday, J., 2020. Chapter 9: Orogenic Gold Deposits of the Kibali District, Neoarchean Moto Belt, Northeastern Democratic Republic of Congo, in: Sillitoe, R.H., Goldfarb, R.J., Robert, F., Simmons, S.F. (Eds.), Geology of the World’s Major Gold Deposits and Provinces. Society of Economic Geologists, p. 0. https://doi.org/10.5382/SP.23.09

Turnbull, R.E., Allibone, A.H., Matheys, F., Fanning, C.M., Kasereka, E., Kabete, J., McNaughton, N.J., Mwandale, E., Holliday, J., 2021. Geology and geochronology of the Archean plutonic rocks in the northeast Democratic Republic of Congo. Precambrian Research 358, 106133. https://doi.org/10.1016/j.precamres.2021.106133

How to cite: Birimwiragi Namogo, D., Martial Akame, J., Mbuluyo, M., Debaille, V., Mango Itulamya, A. L., and Hubert-Ferrari, A.: Geology of the Isiro-Ngayu gold-bearing region, western belts of the Kibali granite-greenstone superterrane in the northeastern Congolese craton, Democratic Republic of Congo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13796, https://doi.org/10.5194/egusphere-egu25-13796, 2025.

The Crustal Dynamics Data Information System (CDDIS) provides essential support for the Global Geodetic Observing System (GGOS) by operating a data and product archive for the main geodetic techniques.   As GGOS matures and grows, the CDDIS adopts the latest data practices to strengthen its support for the community and ensure quality products are available in a timely manner.  This poster explores the breadth of work done at the CDDIS and provides highlights of the latest developments including new data and product holdings, updates to provide clarity and usability for users, and updates on future works. Statistics on usage will also be provided.

How to cite: Woo, J.: The Crustal Dynamics Data Information System (CDDIS) Updates for 2025, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13924, https://doi.org/10.5194/egusphere-egu25-13924, 2025.

Abstract

Urban surface dust and soils serve as a primary source and reservoir of metals that substantially impact human health and urban ecosystems. This study investigates the impact of metal contamination on urban surface soils from diverse land-use locations and their potential risk to human health in Jammu City, India. A total of fifteen surface soil samples were collected to evaluate the total metal concentration (As, Cu, Fe, Mn, Ni and Zn), Contamination Factor (CF), Geo-accumulation Index (Igeo), Pollution Load Index (PLI), and Potential Ecological Risk Index (PERI). The research findings of this study revealed significant variation in metal concentration. In comparison to Upper Continental Crust (UCC, taken as background here), the average concentration of Fe and Mn is lower across all locations, whereas As, Ni, Cu, and Zn are significantly higher over all locations. Elevated levels of Fe and Mn were observed higher near samples collected from industrial zones while Ni, As, Cu and Zn showed wider distribution throughout the study area. Apart from all metals, high As content was observed at near-construction and high-traffic interactions. Higher CF (CF > 6) and PLI values in surface soil samples revealed high contamination of As, Cu, Ni and Zn due to intensive industrial and vehicular emissions in the study area. Igeo values in surface soil samples indicated severe contamination of As, Cu, Ni and ZN in the study area, while Fe and Mn showed no contamination. PERI assessment in surface soil samples revealed extremely high ecological risk for As and Cu in Jammu City. Risk index values indicated that 40% of surface soil samples carried a very high risk (RI > 600) of metal contamination in the study area. The overall findings advised that industrial, transportation, and construction activities need to be improved to protect the region's environment and public health.

Keywords: Heavy metals, geo-accumulation index (IGeo), risk assessment, roadside dust.

How to cite: Gorka, R. and Kumar, R.: Spatial Distribution and Contamination Levels of Heavy Metals (Fe, Mn, Ni, Cu, As, and Zn) in Urban Topsoils of Jammu City, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14122, https://doi.org/10.5194/egusphere-egu25-14122, 2025.

Low Earth Orbit (LEO) satellites have the advantages of high flight velocity and minimal influence from external environmental factors on onboard observation. Integrating LEO satellite observations with ground observations can improve the accuracy and convergence performance of GPS and LEO real-time orbit determination, which can simultaneously meet the prerequisites for real-time Positioning, Navigation, and Timing (PNT) services for both GPS and LEO systems. Therefore, this study employs the Square Root Information Filter (SRIF) for GPS and LEO satellites real-time joint orbit determination (RTJOD). Based on observations from eight existing scientific LEO satellites, a detailed study on RTJOD was conducted under two scenarios: one using observations from 100 global stations and the other using observations from 9 regional stations in Australia. The results show that, with 100 global stations, incorporating LEO observations can significantly improve the convergence performance and GPS satellite orbit accuracy. The convergence times in the Along-track, Cross-track, and Radial components are reduced from 3.5, 5.8, and 10.3 h to 0.9, 1.0, and 10.3 h, respectively. The accuracy improves from 5.8, 3.6, and 2.8 to 4.0 cm, 2.5 cm, and 2.5 cm. Additionally, the ambiguity resolution (AR) performance is significantly enhanced. The time required to achieve a 90% narrow-lane ambiguity fixing rate is reduced from 4.9 to 0.7 h. After AR, the orbit accuracy further improves to 3.1 cm, 2.3 cm, and 2.4 cm. In the case of the 9 regional stations in Australia, after incorporating LEO, the orbit accuracy of the float solution after convergence is comparable to that of the 100 global stations without LEO, with accuracies of 6.0, 4.8, and 2.9 cm in the three components. It is important to note that, due to insufficient observations in this case, AR does not result in any further improvement in accuracy. In addition, LEO can achieve orbit determination accuracy better than 5 cm within a short time in both station distribution scenarios. This ensures that RTJOD enables LEO and GPS to generate high-precision real-time orbits simultaneously. Finally, the processing time for each epoch in all scenarios is less than 5 seconds, ensuring that the GPS and LEO RTJOD can provide timely orbit updates.

How to cite: Lai, W., Huang, G., Wang, L., She, H., Xie, S., Xie, W., and Wang, Q.: Real-time high-precision joint orbit determination of GPS and LEO using SRIF, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15238, https://doi.org/10.5194/egusphere-egu25-15238, 2025.

Zenith Total Delay (ZTD) is a crucial parameter for understanding the effects of atmospheric conditions on satellite signals, constituting a fundamental aspect of precision positioning and atmospheric modeling applications. Traditional methods for ZTD estimation, including GNSS observations, numerical weather prediction models, and interpolation techniques, encounter critical limitations such as generalization constraints, sparse data availability, insufficient spatial coverage, high computational costs, and limited adaptability to dynamic atmospheric changes. Deep learning techniques provide substantial benefits, including processing large and complex datasets, enabling dynamic modeling, and delivering rapid and accurate estimations.

This study integrates real-time GNSS observations with high-resolution atmospheric reanalysis data from the ERA5 dataset to develop deep learning-based methods for ZTD estimation. GNSS data were sourced from 17 IGS tropospheric stations strategically selected to represent diverse geographic and climatic conditions. These stations supplied ZTD values and their temporal variations at 5-minute intervals, spanning February 2023 to January 2024. ERA5 data, offering hourly atmospheric parameters, necessitated the alignment of GNSS temporal resolution with ERA5 for spatial modeling. The spatial distribution of GNSS data was optimized using interpolation techniques to enhance the quality of inputs for deep-learning models.

The findings highlight the potential of deep learning techniques to enhance ZTD estimation processes. Future research will focus on integrating additional datasets, such as InSAR, to achieve higher spatial resolution and improved accuracy. Moreover, advanced deep learning architectures, including attention mechanisms, will be investigated to refine estimation methods and broaden their applications in atmospheric and geospatial studies.

How to cite: Tekin Ünlütürk, N. and Bak, M.: Deep Learning Approaches for Zenith Total Delay Estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15605, https://doi.org/10.5194/egusphere-egu25-15605, 2025.

A Global Geodetic Observing System (GGOS) affiliate is an organization or entity that collaborates with the Global Geodetic Observing System (GGOS) to enhance the global geodetic infrastructure and support the objectives of GGOS in a region.
With this goal, a GGOS affiliate was created to enhance geodetic infrastructure and scientific collaboration across the Iberian Peninsula and the Atlantic region. It is called GGOS IberAtlantic. This project focuses on improving the accuracy and reliability of geospatial data through the co-location and integration of geodetic space techniques to support various scientific and practical applications, including global reference frame maintenance, climate change monitoring, natural hazard assessment, in the perspective of a sustainable development. GGOS IberAtlantic aims to establish a robust network of geodetic stations, facilitate high-accuracy data collection, and promote international cooperation among geodetic institutions, contributing to a better understanding of Earth's dynamic processes. It is also focused on supporting decision-making in the area and bringing geodesy closer to society, specially to young scientists.
The upcoming presentation will outline the steps taken to establish the GGOS IberAtlantic group, as well as its future directions and objectives.

Acknowledgment. This presentation was supported partially by Spanish Project PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033)

How to cite: Azcue, E. and Ferrándiz Leal, J. M. and the GGOS IberAtlantic Governing Board: GGOS IberAtlantic Affiliate: Bringing Geodesy Closer to Society across the Iberian Peninsula and the Atlantic region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17154, https://doi.org/10.5194/egusphere-egu25-17154, 2025.

The neutral atmosphere that extending from the surface of earth to about 80 km overhead is the electrically neutral part (within a certain frequency band which GNSS signals fall) of the atmosphere. There is no doubt that neutral atmosphere has a delaying effect on transmitted radio waves. Spilker (1996) noted that the more precise term of this delaying effect is neutral atmosphere delay, even though this delaying effect has been traditionally referred to as just troposphere delay. At all events, the delaying effect has propagated into satellite observations, and we must deal with it appropriately in order to achieve precise satellite positioning results. There are many geodesists have been making their contributions to treatment of neutral atmosphere delay, and how to get satisfactory supports from numerical weather model data set is one of the efforts making to calibrate this delaying effect more precisely up-to-date. Currently, both Earth observation network and technology have great improvement, which results in wonderful increase of Earth observational data as well as the subsequent numerical weather model data set. Briefly speaking, numerical weather model data set which generally provided by different organizations and/or institutions is a global and/or regional gridded meteorological data set with specific temporal-spatial resolution. Generally, reanalysis data set and forecast data set are usually considered to be the two main data set representations, and they both provide two types of data level, i.e., three-dimensional pressure levels and two-dimensional surface level. The data set contains some usually used meteorological parameters, such as height, temperature, pressure, humidity. With these meteorological parameters, some main terms related to neutral atmosphere delay, such as hydrostatic/wet delay, gradient factors and mapping factors can all be calculated without any difficulty by using computing techniques like raytracing and interpolation. Undoubtedly, the performance of different types of data set that mentioned above in representing neutral atmosphere delay are not all the same. Definitely, some interesting and meaningful comparison results have found and widely propagated by many scholars. In this work, we put more emphasis on evaluation of the forecast data set from neutral atmosphere delay point of view, considering there is an objective fact that satellite positioning industry especially the (near) real-time positioning has vigorous development, in which the calibration of neutral atmosphere delay is required more and more accurate and timely-supported. Besides time-delayed reanalysis data set and time-advanced forecast data set, microwave radiometer data set and radiosonde data set are also employed. The first results show that empirical model such as UNB3 can only state the normal level of delaying effect and the obtained delay values are either larger or smaller; the pressure levels data set performs better than the surface level data set with very high proportion in time domain; even though reanalysis data set generally has good performance, forecast data set can work for the neutral atmosphere delay calibration with relatively satisfactory support in term of accuracy.

This work is supported by the National Natural Science Foundation of China (42304010), the Youth Foundation of Changzhou Institute of Technology (E3-6207-21-060, 31020222007).

How to cite: Wang, M.: First results about evaluation of forecasted numerical weather model data set in view of neutral atmosphere delay, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17506, https://doi.org/10.5194/egusphere-egu25-17506, 2025.

Tropospheric refraction is one of the major error sources in satellite-based positioning. The delay of radio signals caused by the troposphere ranges from 2m at the zenith to 20m at low elevation angles, depending on pressure, temperature and humidity along the path of the signal transmission. If the delay is not properly modeled, positioning accuracy can degrade significantly. Empirical tropospheric models, with or without meteorological observations, are used to correct these delays but they are limited in accuracy and spatial resolution resulting in up to a few decimeters error in positioning solutions. The present availability of ground-based GNSS networks and the state of the art of GNSS processing techniques enable precise estimation of Zenith Tropospheric Delays (ZTD) with different latency ranging from real time to post-processing.
We present a method for computing ZTD residual fields interpolating, through Ordinary Kriging, the residuals between GNSS-derived and model-computed ZTD at continuously operating GNSS stations. GNSS ZTD estimates, obtained in real time and in PPP mode, are augmented by a multi-prediction model based on a Graph Neural Network model trained using one year of Near Real Time ZTD observations and a model using a polynomial plus harmonic interpolation. A combination strategy is defined to merge GNSS ZTD estimates at sites with the predicted values, where predicted ZTD values act as hole fillers for stations missing from the GNSS network at the current epoch. The residual ZTD field, obtained from PPP/prediction model and ZTD empirical model, is modelled as a random process and for each epoch a variogram is estimated and fitted to characterize the spatial correlation of the process. At a known user location, ZTD value is obtained as the sum of site interpolated ZTD residual and modeled-ZTD value. The algorithm is validated with respect to GNSS ZTD estimates provided by an external provider at a selection of sites not included in the network used to fed the computation. Details about validation and possible improvements will be provided.

How to cite: Basoni, A., Pacione, R., Bagaglini, L., and Lanotte, R.: Real-Time ZTD correction grid based on augmented GNSS network for navigation services, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18280, https://doi.org/10.5194/egusphere-egu25-18280, 2025.

The University of Luxembourg (UL), in collaboration with the United Kingdom Met Office, continues to advance the provision of global and regional near real-time (NRT) Zenith Total Delays (ZTDs) from GNSS ground networks to support operational meteorological products within the EUMETNET EIG GNSS Water Vapour Programme (E-GVAP). E-GVAP facilitates coordination and uptake of NRT GNSS-based atmospheric monitoring, which is indispensable for assimilation in Numerical Weather Prediction (NWP) models across Europe, including at the Met Office, where high-temporal-resolution data enhance mesoscale weather forecasting. This study highlights the collaborative efforts of the Met Office and UL in delivering accurate, timely meteorological data from GNSS. The partnership has resulted in the development and enhancement of NRT processing systems using the state-of-the-art Bernese GNSS software version 5.4 (BSW5.4), generating ZTD products at both UL and the Met Office at 1-hour intervals globally and regionally, and at sub-hourly intervals regionally. Over the past year, UL has focused on developing hourly NRT ZTD solutions for global and regional networks, and more recently extending them to sub-hourly intervals (down to 15 minutes) for regional coverage, thereby refining the temporal resolution for E-GVAP users. In particular, we are now prepared to provide NRT products in the form of a global hourly product (ULGH), a regional hourly product (ULRH), and a regional sub-hourly product (ULRS) to E-GVAP. As part of the system's development, we validate our latest global, regional, and sub-hourly ZTD solutions against established NRT outputs from E-GVAP and benchmark post-processed Double-Difference Network (DDN) products, while also verifying Integrated Water Vapour (IWV) estimates against ECMWF Reanalysis v5 (ERA5). Finally, we highlight how higher-frequency updates can positively influence NWP assimilation in rapidly evolving weather situations, detailing data flow and latency management that ensure reliable NRT ZTD delivery to E-GVAP participants and the Met Office. By extending temporal coverage from hourly to sub-hourly in regional networks and continuing our global solutions, we advance the utility of GNSS-based atmospheric sensing for short-term weather forecasting, providing consistent, high-quality NRT GNSS products for meteorological operations in Europe and beyond. 

How to cite: Hunegnaw, A., Teferle, F., and Jones, J.: Extending Global and Regional Near Real-Time GNSS ZTD Solutions Using BSW5.4 at the University of Luxembourg: Contributions to E-GVAP , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18910, https://doi.org/10.5194/egusphere-egu25-18910, 2025.

The Geophysics Section of the Royal Institute and Observatory of the Navy (ROA) is structured into three main services: Seismology, Geomagnetism, and Space Geodesy, in addition to an auxiliary Meteorology service and participation in maritime scientific campaigns. Since its foundation, the ROA has played a pioneering role in Spain, being a member of the Spanish Commission of Geodesy and Geophysics and collaborating with international institutions across all its fields of activity, such as ILRS, IGS, INTERMAGNET, and GEOFON, as well as organizations like NASA and ESA, among others.

The Geomagnetism Service, established in 1879, studies the Earth's magnetic field and its variations to conduct scientific research. After several relocations due to electromagnetic interference, the current geomagnetic observatory is located at Cortijo de Garrapilos (Cádiz) and has been a member of INTERMAGNET since 2006. The Seismology Service dates back to 1898, when one of the 12 seismographs of the first global seismic network, promoted by geologist John Milne, was installed at the ROA. The current infrastructure is distributed across Spain and North Africa, including a short-period network for regional seismicity in the Gulf of Cádiz and the Alboran Sea, long-period stations for global seismicity, and the international Western Mediterranean network, in which prestigious institutions such as UCM and GFZ participate. The ROA has been involved in space geodesy with artificial satellites since the early days of the space era, starting just one year after the launch of the first SPUTNIK (1958) with the Baker-Nunn camera. This technique was followed by laser ranging (SLR) in 1975, when a station capable of tracking collaborative satellites was installed. By 1980, the station was exclusively operated by ROA personnel. Since then, the station has undergone constant upgrades to maintain a high level of operability. Today, it contributes to national and international tracking networks such as ILRS-EUROLAS and EU SST-S3T. Additionally, the ROA adopted GPS in the 1980s for geodetic studies and currently manages a GNSS network comprising 17 permanent stations spanning the southern Iberian Peninsula and North Africa. Maritime campaigns include studies in the Spanish Exclusive Economic Zone (EEZ), with objectives such as hydrographic surveys and geophysical exploration for seabed characterization. Since 1987, the ROA has also participated in Antarctic campaigns.

The Geophysics Section of the ROA combines tradition and advanced technology to contribute to the understanding of the Earth and space, consolidating its position as a national and international benchmark in the study of geophysical and geodetic processes. Evidence of this includes recent or ongoing scientific work over the past years: four doctoral theses (three of them in progress), various articles in high-impact journals, participation in numerous scientific projects, and extensive contributions to conferences. In this way, the ROA, through the Geophysics Section, fosters collaboration in geodesy through its active participation in international networks, addressing global scientific and societal challenges with cutting-edge technology and a multidisciplinary approach.

How to cite: Rodriguez Collantes, D., Sánchez Piedra, M. Á., Cabieces Díaz, R., and Fiz Barreda, J.: Scientific Legacy and Current Contributions of the Royal Institute and Observatory of the Spanish Navy: Impact on Geophysics, Geodesy, and other Scientific and Social Fields., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19802, https://doi.org/10.5194/egusphere-egu25-19802, 2025.

The accuracy and reliability of Earth Orientation Parameters (EOP) are significantly influenced by the geometric configuration of the Very Long Baseline Interferometry (VLBI) network. This astronomical technique employs a global network of radio telescopes to collect data. The distribution of VLBI antennas affects the triangulation process used to determine the positions of celestial sources, which is integral to the calculation of EOP. An optimal geometry yields more accurate and reliable EOP results, which are essential for many scientific applications.

This study examines the impact of different VLBI networks on EOP estimation, using data collected during several Continuous VLBI Campaigns (CONT) and designing alternative networks by removing various antennas and/or baselines from the original configuration. The results of this analysis aim to contribute to the refinement of EOP and the achievement of the stringent GGOS accuracy targets (i.e., a frame with accuracy at epoch of 1 mm or better and a stability of 0.1 mm/y).

How to cite: del Nido Herranz, L. D., Belda, S., Karbon, M., Ferrándiz, J. M., and Azcue Infanzón, E.: Influence of VLBI Network Geometry on the Estimation of Earth Orientation Parameters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20077, https://doi.org/10.5194/egusphere-egu25-20077, 2025.

The Residual Terrain Modeling (RTM) technique is commonly used to recover short-wavelength gravity field signals. However, classical gravity forward modeling methods for RTM gravity field determination face challenges such as series divergence, inefficient computation, and errors induced by tree canopy in Digital Elevation Models (DEMs). In this study, deep learning methods are employed to enhance the quality of the computed RTM gravity field. Experiments are conducted at the Wudalianchi airborne gravity gradiometer test site, which provides a large volume of precise gravity measurements. The Random Forest method is used to estimate and correct tree canopy height errors in DEMs. A fully connected deep neural network (FC-DNN) is introduced to efficiently calculate the RTM gravity field. Additionally, to improve the network’s generalization capability, a novel terrain information fusion regularization method is applied to create an Improved FC-DNN with a refined loss function. The accuracy, computational efficiency, and generalization performance of the deep learning method are evaluated and compared in the Wudalianchi volcanic region. The results demonstrate a significant improvement in the accuracy of the RTM gravity field when based on tree canopy-corrected DEMs. The RTM gravity fields determined using both FC-DNN and Improved FC-DNN achieve mGal-level accuracy, with a remarkable 10,000-fold increase in computational efficiency compared to the classical Newtonian integration method. The Improved FC-DNN exhibits superior generalization, with accuracy enhancements ranging from 7% to 21% compared to the standard FC-DNN.

How to cite: Yang, M., Zhang, B., Wang, L., Feng, W., and Zhong, M.: Deep learning in RTM gravity field modeling: A case study over Wudalianchi area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20320, https://doi.org/10.5194/egusphere-egu25-20320, 2025.

Phanerozoic intraplate magmatism has frequently been observed in association with ancient sutures, palaeorifts and strike-slip fault zones across multiple ancient cratons, including Laurentia, Baltica, Australia, Siberia. However, it is still unclear whether these lithospheric discontinuities were passive conduits for the melts generated in the asthenosphere, or if their tectonic reactivations acted as a primary control on melt production and distribution. In the Superior province of the Canadian shield, we explore the relationship between intraplate tectonic and magmatic activity along two segments of the Proterozoic St. Lawrence failed rift system, which hosts two Jurassic kimberlite fields (Kirkland Lake, Timiskaming) and a Cretaceous alkaline province (Monteregian Hills). Our goals are 1) to examine the structural settings of these provinces and 2) investigate the potential role of these lithospheric structures in melt production and channelling under the Mesozoic stress regime.

Basement fault structures associated with kimberlite pipes and alkaline intrusions were identified using available aeromagnetic data from Timiskaming and Montérégie. Magnetic data were employed  to construct a constrained 3-D inversion of the magnetic susceptibility distribution using Oasis montaj VOXI software package. Additionally, the regional stress field in the Superior province in the Mesozoic was reconstructed based on 542 measurements of joints, shear fractures, veins and dykes taken at 36 sites across the Palaeozoic cover of St. Lawrence lowlands. The Right Dihedron and Rotational Optimisation methods implemented in WinTensor 5.9.2 were used to compute stress tensors for structural associations of different relative ages.

The results demonstrate that Kimberlite pipes of the Timiskaming and Kirkland Lake fields tend to cluster around the intersections of two fault families: 1) thrust faults of Neoarchean Destor-Porcupine and Esker – Larder Lake sutures (trending W–E), and 2) normal faults of the Proterozoic Timiskaming graben (trending NNW – SSE). Intrusions of the Monteregian Hills alkaline province are also emplaced at the intersection of two fault families: 1) normal faults of the Proterozoic Ottawa – Bonnechere graben (trending W–E), and 2) a N–S trending set of faults of unclear kinematics or age. Reconstructed stress tensors for the Mesozoic are indicative of an extensional regime and a progressive counter-clockwise rotation of the stress-field throughout the Mesozoic (subhorizontal σ₃  trend shifts from 86 to 306).

The spatial distribution of intrusions within the Timiskaming and Ottawa-Bonnechere grabens, indicates that intraplate magmatism was strongly controlled by St. Lawrence paleorift structures. However, intrusions are preferentially localized in areas where the paleorift is intersected by other fault systems. We speculate that these local fault systems are transfer faults oriented perpendicular to the normal faults of St. Lawrence system, creating pull-apart-like structures that accommodated intraplate magmatism. This emplacement model aligns with geochronological data, which indicate Jurassic intrusions of the Timiskaming and Kirkland Lake fields were emplaced along NNW–SSE-trending graben under a SW–NE  trending σ₃ , while the Cretaceous Monteregian Hills were emplaced along the W–E-trending Ottawa–Bonnechere graben under a N–S trending σ_3.

How to cite: Koptev, E., Peace, A., and Boyce, J.: Tectono-magmatic reactivation in cratonic settings: a case study from the Superior province, Canada, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-708, https://doi.org/10.5194/egusphere-egu25-708, 2025.

Cold slab subduction and hot plume burst are generally envisaged as independent triggers for convergent margin and intraplate magmatisms, respectively. However, descending oceanic plates occasionally encounter ascending mantle plumes, leading to contrasting hypotheses that plumes interrupt subduction processes and/or slabs choke plume pathways. This study used 2-D numerical simulation to reproduce a Paleozoic scenario in Central Asia where a subduction-induced plume head is invoked to interpret the formation of the Tarim large igneous province (LIP). The model assumes a long-lived mantle plume beneath the South Tianshan oceanic plate adjacent to the trench. As subduction initiated, plume materials spread first under the moving oceanic lithosphere, which developed a sequence of seamounts. Subsequently, the continual subduction drove a strong downwelling flow that stalled or restricted plume ascent in the upper mantle and caused the accumulation of hot materials in the uppermost lower mantle. Ultimately, the slab break-off after collision provided an opening pathway allowing for the accumulated hot materials to reach the surface, resulting in the development of a concurrent plume head and the formation of LIP on the overriding Tarim craton. Bending and rollover of the subducted oceanic lithosphere beneath an implemented stationary trench may contribute slab components to the LIP source, which can reasonably explain the slab-like geochemical fingerprints of basaltic rocks. Our work offers a tentative interpretation for the paradox that seamount formation preceded the LIP eruption in Tianshan and highlights possible slab effects, where subduction can stall the plume tail, causing heat accumulation that triggers a LIP.

How to cite: Wang, K.: Subduction-stalled plume tail triggers Tarim large igneous province, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1969, https://doi.org/10.5194/egusphere-egu25-1969, 2025.

Multiple magmatic and metamorphic events occurred in northeast Asia during the Orosirian period. Orosirian multiple magmatic and metamorphic events are also known to provide information about the amalgamation and break-up of the Columbia/Nuna supercontinent. The Yeongnam Massif, one of the Paleoproterozoic tectonic provinces in the Korean Peninsula, is known to have undergone two magmatic activities during ca. 2.02-1.86 Ga. This study focused on the Orosirian metagranitoid and amphibolite in the Gangjin-Wando-Jangheung area in the southwestern part of the Yeongnam Massif. In this study, we conducted the zircon Lu-Hf isotope analysis, the whole-rock geochemical analysis, and zircon U-Pb dating for metagranitoid and mafic xenoliths. Our study, a detailed investigation into the emplacement timing and petrogenesis of the Orosirian metagranitoid and mafic xenoliths in the study area, can provide crucial insights into the Orosirian multiple magmatic activities in the Yeongnam Massif along with their tectonic implications.

How to cite: Ko, K.: Zircon U-Pb-Hf isotope and whole-rock geochemical analysis of the Paleoproterozoic Orosirian metagranitoid and mafic xenolith in the southwestern part of the Yeongnam Massif, South Korea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3561, https://doi.org/10.5194/egusphere-egu25-3561, 2025.

The Miocene epoch on Svalbard is characterized by volcanic activity and tectonic uplift, but the causes and relationship between these two processes remain debated. The evidence of coeval basaltic magmatism has probably affected a large area including Svalbard. The Seidfjellet Formation, a series of basaltic lava flows, represents a unique late Miocene subaerial magmatic event (5–10 Ma) in northwestern Spitsbergen. These flows, covering more than 200 km², are exposed on top of numerous mountains in Andrée Land overlying Devonian sedimentary rocks. This study investigates the structure, composition and origin of this underexplored igneous province within a tectonomagmatic context, focusing on defining the magnitude, paleoenvironment, and chronology of the volcanism and contributing to our understanding of the Miocene evolution in Svalbard and adjacent Arctic regions.

In the summer of 2023, we systematically mapped and sampled (n = 83) well-exposed outcrops along Woodfjorden, logging basaltic lava flows from an elevation of approximately 600 to over 1000 m above sea level. Additionally, we acquired photospheres and photographs using unmanned aerial vehicles (UAVs). Photographs were processed to obtain high-resolution georeferenced digital outcrop models (DOMs) for systematic mapping of the Seidfjellet Formation and its relationship with the pre-basal emplacement paleosurface. To enhance the consistency of our dataset, 13 legacy samples collected in 2014 were analyzed for standard geochemical characterization, including major and trace element concentrations, isotopic ratios, and ⁴⁰Ar/³⁹Ar age determination.

The mapped lava flow sequences have variable thicknesses, with 400 m being the observed local maximum, indicating significant magma accumulation.  A massive 50 m thick olivine-rich sheet-flow unit is present in the lower part of the formation. Locally, a distinct hyaloclastic unit documents subaqueous lava emplacement. In contrast, the upper sections provide clear evidence of subaerial emplacement, with pahoehoe lava flow features. The interpretation of DOMs, the distribution of the lava flows as well as GIS-based thickness and volume estimates suggest that the igneous province extends more widely than what is evident from the existing remnant outcrops.  The Seidfjellet Formation shows variable sediment-basalt transitions, including sharp valley infill profiles and erosion surfaces above Devonian sandstones. Thickness estimates and remnant outcrop distributions point towards an eruption center near Scott Keltiefjellet, where hyaloclastites and dolerite layers are also exposed. Geochemical analysis reveals both silica-saturated 'tholeiitic' and silica-undersaturated 'alkaline' magmas, with isotopic evidence of crustal-contaminated mantle-derived magmas, reflecting a complex geological setting. Six Ar/Ar ages document a timespan of over 1 million years between 8 and 10 Ma, whereas one sample has an age of about 5 Ma refining earlier estimates.

The Seidfjellet Fm. represents the only subaerial expression of Miocene volcanic activity in Svalbard. Linking this event to similar and coeval features in the Arctic, both in terms of geochemistry and paleoenvironmental studies, provides an opportunity to identify a significant magmatic event potentially linked to the region's vertical motion history.

How to cite: Telmon, M., Betlem, P., Grundvåg, S. A., Kenji Horota, R., Minakov, A., Planke, S., Senger, K., Tegner, C., and Zastrozhnov, D.: The Seidfjellet Formation in NW Spitsbergen: A Window into Miocene Volcanism and Tectonics of Arctic-Atlantic Gateway , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3700, https://doi.org/10.5194/egusphere-egu25-3700, 2025.

The Northeast Atlantic Igneous Province (NAIP) formed during the Paleocene/Early Eocene, driven by the Iceland hotspot. Its volcanic margins show a positive correlation between igneous thickness (H) and lower-crustal P-wave velocity (V_P), indicating that high-temperature is driving excess mantle melting. However, previous studies have argued for large variations in structure and magmatic volumes between the conjugate margins of the Vøring Plateau and East Greenland, and there are inconsistencies in defining the conjugate continent-ocean transition zones (COTs). In this study, we use the H-V_P correlation from various wide angle seismic studies, where a positive trend identifies igneous crust, while a rapid transition to a strong negative trend marks the increased presence of continental crust to redefine the COTs on conjugate Vøring Plateau and East Greenland margins. This definition gives consistent COTs in plate reconstruction to opening. Our results show that the total  magmatic volume of the East Greenland margin (8.23 × 10⁵ km³) is only slightly larger than for the Vøring Plateau (7.51 × 10⁵ km³). Later secondary magmatism in East Greenland (Late Eocene to Miocene) occurred during the separation between East Greenland and the Jan Mayen Microcontinent. Assuming symmetric magmatic volumes on each plate after breakup between the East Greenland margin and the Vøring Plateau, the difference can be used to estimate secondary magmatic volume in East Greenland (0.72 × 10⁵ km³), which is less than 10% of the initial breakup magmatism. In addition, other post-breakup mid-to-late Cenozoic events including Logi Ridge, Jan Mayen Plateau, Vesteris Seamount, Jan Mayen Island and Vøring Spur, contribute an estimated total volume of 2.2 × 10⁵ km³. While quite visible, the igneous volume of these events is thus far less than the Early Eocene breakup magmatism.

How to cite: Tan, P. and Breivik, A.: Break up and Post-Breakup Magmatism between the conjugate margins of the Vøring Plateau and East Greenland, NE Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4037, https://doi.org/10.5194/egusphere-egu25-4037, 2025.

Granitoids are prevalent in southeastern China and are associated with numerous renowned polymetallic deposits. The mineralization is thought to have a close genetic linkage with granitic magmatism in this region. However, the petrogenesis of these granites remains a subject of debate. Dengfuxian granites in the eastern Hunan Province, a representative granitic pluton, formed during this geological period and are linked with tungsten deposits. To constrain their magmatic origins and petrogenesis, analyses were conducted, including whole-rock geochemistry, SIMS zircon geochronology, oxygen isotope studies, and LA-ICPMS zircon Lu–Hf isotopic analyses on selected samples of Dengfuxian granites.The Dengfuxian granitic pluton predominantly consists of biotite granite, two-mica granite, and muscovite granite. Age determinations of the various granite types indicate the existence of two distinct episodes: the Late Triassic (221–226 Ma) and the Late Jurassic (150–151 Ma). Granites from both periods consistently exhibit high concentrations of SiO₂, Al₂O₃, total alkalis, K₂O, and P₂O₅, while showing low levels of MgO, TiO₂, and MnO₂, exhibiting a range from weak to strong peraluminous characteristics. Geological and geochemical evidence supports that the Dengfuxian granites are highly fractionated I-type granites, although some features typical of S-type granites are present, likely due to significant magmatic fractionation.Zircon Hf and O isotopic data reveal that the granites from both episodes originated from ancient crustal material, undergoing partial melting and substantial fractionation. The Late Triassic granites, in particular, appear to have incorporated a greater proportion of ancient crustal material into their magma.

How to cite: Liu, Q. and Zhang, H.: Petrogenesis of Dengfuxian granites in Hunan Province, SE China: Insights from U-Pb zircon ages and geochemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5901, https://doi.org/10.5194/egusphere-egu25-5901, 2025.

Hotspots create linear volcanic features on Earth’s crust as tectonic plates migrate over and thus are often used to trace absolute plate motion. The effectiveness of a hotspot reference frame depends on the hotspot’s fixity or constraints on its motion history. Studies of Pacific hotspots revealed distinct hotspot motions that were variously attributed to shallow and/or deep mantle convection processes, but knowledge of hotspot movements elsewhere remains limited. Here we report robust and high-precision ⁴⁰Ar/³⁹Ar ages for the Ninetyeast Ridge, a >5000-km long linear volcanic ridge generated by the Kerguelen hotspot during the Indian Plate’s northward drift towards Eurasia. New ages suggest changing volcanic progression rates along the ridge, in contrast to a constant rate as previously documented. Combined with independent constraints on the Indian Plate motion and seafloor spreading, we reveal two periods of northward hotspot migration together with the Indian-Antarctic spreading ridge, and two periods of rapid southward motion of the hotspot when it was disconnected from and re-captured by separate spreading ridge segments. These rapidly changing motion histories affected by spreading ridges suggest that mantle plume lateral flows are susceptible to changes in shallow mantle convection processes due to the existence of horizontal ponding zones and vertical conduits as revealed by recent seismic tomography images of mantle plumes.

How to cite: Jiang, Q., Olierook, H., Jourdan, F., Carmona Hoyos, D., Merle, R., Mervine, E., and Sager, W.: Motions of the Kerguelen hotspot constrained by high-precision 40Ar/39Ar ages of the Ninetyeast Ridge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6674, https://doi.org/10.5194/egusphere-egu25-6674, 2025.

Enigmatic fayalite and orthopyroxene-bearing quartz-monzonite, locally named bauchite, is identified at the lowest exposed structural level of the Pan-African basement in Nigeria. This very iron-rich rock challenges the typical Bowen's reaction series, which suggests that olivine and quartz should not coexist. Nigeria's Precambrian basement consists of a series of metamorphosed magmatic and sedimentary rocks including schists, quartzites, amphibolites, and calc-silicates, transitioning into a granitoid-gneiss complex, designated as the Bauchi complex, in the north-central region. The lowest structural level of this complex consists, from bottom to top, in bauchite, hornblende-biotite granite and biotite granite, which is in contact with granulite facies migmatites. Earlier studies attributed bauchite formation to the impregnation of granites by iron-rich fluids and argued that the coexistence of ortho- and clino-pyroxenes with fayalite and quartz suggests deep-crustal magmatic emplacement (≈30 km depth).

Our field investigations indicate that bauchite and surrounding granite, crosscuts the regional scale NW-SE trending foliation of the host migmatites, which is consistent with an intrusive plutonic body. The preferred orientation of feldspar phenocrysts in bauchite but also in granites, delineates a shallow-dipping magmatic foliation and a regional-scale domal structure. Bauchite, exposed in the core of the dome, has a granular texture, with microcline and albite phenocrysts in a matrix of fayalite, ortho- and clino- pyroxenes, hornblende, biotite, and quartz. The accessory minerals present are zircon, apatite, magnetite, ilmenite, and titanite. At the lowest structural level, green bauchite dominated by fayalite and pyroxenes grades in brown bauchite characterized by a larger amount of hornblende and biotite. Textural analysis indicates a magmatic layering delineated by the alternation of fayalite-pyroxenes and microcline-albite layers. Interstitial quartz shows no signs of intracrystalline deformation, consistent with late crystallization from a melt. Hornblende shows lobate contacts with feldspars and typically forms a corona around fayalite and pyroxenes. Biotite is present as euhedral crystals in contact with hornblende. Microcline is typically bordered by myrmekite. These textures point to a reaction between fayalite-pyroxenes and microcline-albite layers leading to the crystallization of hornblende, biotite and quartz. Bauchite samples have an average SiO₂ content of 65%, a high FeO/MgO ratio (14-17), and low Mg/(Fe+Mg) ratios (0.09-0.12). Their average K/(Na+K) is 0.49, with K₂O exceeding 4%, making them highly potassic. The SiO₂ content negatively correlates with most major oxides except K₂O and Na₂O, which show positive correlation. Trace elements data show high concentrations of Rb, Ba, K, and Zr, along with negative anomalies in Nb, Sr, P, Ti, Gd, Lu, and Y but positive anomalies in Zr, pointing to a deep-seated, alkaline magma. These features are consistent with an origin of bauchite resulting from interaction between an exotic iron-rich mantle derived alkaline magma and a felsic hydrous crustal one.

How to cite: Yahuza, I., Vanderhaeghe, O., Grégoire, M., and Isah Haruna, A.: The Pan-African fayalite quartz-monzonite from north-central basement of Nigeria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8869, https://doi.org/10.5194/egusphere-egu25-8869, 2025.

Proterozoic massif-type anorthosites are large plutons, predominantly composed of plagioclase, emplaced between 2.7 and 0.5 Ga. The Mesoproterozoic Kunene Complex is the largest massif-type anorthosite complex in the world, with an estimated area of ∼ 42,500 km², emplaced in southern Angola and northern Namibia. Recent geochronological studies on the main lithologies indicate ages between 1.50 and1.36 Ga, with the anorthosite dating between 1.43 and 1.37 Ga.

The anorthosite suite of the Kunene Complex locally hosts irregular pegmatoidal enclaves (a few meters-long, one meter-wide), primarily composed of large grains of orthopyroxene, clinopyroxene, Fe-Ti oxides, apatite, and plagioclase, with minor quartz, zircon, titanite and sulphide. The mineralogy and pegmatitic texture suggest that these enclaves represent evolved residual melts, occurring during the final stages of the liquid line of descent of parental magmas to the anorthosite. However, a U-Pb zircon date at ∼1.50 Ga obtained from an enclave is 60 Myr older than the oldest age measured on the Kunene anorthosite so far.

In this study, we provide new U-Pb dates and mineral trace element chemistry for zircon, apatite, and titanite in a set of enclaves and their direct host anorthosites. Samples were collected in two quarries in the central region of the complex in Angola, where these enclaves are well exposed.

Zircon dates from anorthosites and hosted enclaves range between 1.52 and 1.40 Ga. This establishes the beginning of the Kunene magmatism at around 1.5 Ga, testifies to coeval crystallisation of enclaves and host anorthosite, and indicates a prolonged zircon resetting due to the magmatism extending more than 130 Myr.

Both the subhedral cm-scale apatite observed in the enclaves and the smaller grains (max 200 µm) show textural features suggesting they are primary phases. Their trace element signature (relative enrichment in light rare earth elements) agrees with a magmatic origin. With no Pb loss after crystallisation, the igneous age would have been preserved. However, no ages at 1.5 Ga were documented for apatite, as they range between 1.41 and 1.35 Ga and overlap with the youngest zircon dates. We attribute these ages to partial resetting of the parent-daughter system during prolonged thermal activity and fluid circulation triggered by the long-lived Kunene magmatism, which resulted in apparent or mixed apatite ages.

Titanite in the enclaves crystallised as a secondary phase, appearing as clusters of minute anhedral grains closely associated with other alteration minerals. The U-Pb dates for titanite range from 1.41 to 1.37 Ga, overlapping with those for apatite. Titanite records the greenschist facies assemblages observed in the enclaves, providing key evidence of fluid-rock interactions during the post-magmatic stage.

The prolonged magmatic history of the Kunene Complex testifies to extended interaction between crystallisation processes, thermal reworking, and fluid-induced alteration. The new findings indicate that the enclave and host anorthosite are coeval, place the beginning of the anorthosite magmatism at 1.5 Ga, with metasomatic and thermal overprint at 1.42–1.35 Ga. The new data refine the temporal framework of the Kunene Complex emplacement and provide new fascinating insights into the magma dynamics of massif-type anorthosites.

How to cite: Ngomane, G., Lekoetje, T., Milani, L., Bybee, G. M., Hayes, B., Owen-Smith, T. M., Lehmann, J., and Jelsma, H.: Prolonged (>100 Myr) magmatic and thermal evolution in the world’s largest massif-type anorthosite complex (Kunene Complex, Angola and Namibia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10002, https://doi.org/10.5194/egusphere-egu25-10002, 2025.

Mantle plumes, the hot upwellings from the Earth's core-mantle boundary, are thought to trigger surface uplift and the emplacement of large igneous provinces (LIPs). Magmatic centres of many LIPs are scattered over thousands of kilometres. This has been attributed to lateral flow of plume material into thin-lithosphere areas, but evidence for such flow is scarce. Here, we use new seismic data and new methods of seismic thermography to map previously unknown plate-thickness variations in the Britain-Ireland part of the North Atlantic Igneous Province, linked to the Iceland Plume. The locations of the ~60 Myr old uplift and magmatism are systematically where the lithosphere is anomalously thin at present. The dramatic correlation indicates that the hot Iceland Plume material reached this region and eroded its lithosphere, with the thin lithosphere, hot asthenosphere and its decompression melting causing the uplift and magmatism. We demonstrate, further, that the unevenly distributed current intraplate seismicity in Britain and Ireland is also localised in the thin-lithosphere areas and along lithosphere-thickness contrasts. The deep-mantle plume has created not only a pattern of thin-lithosphere areas and scattered magmatic centres but, also, lasting mechanical heterogeneity of the lithosphere that controls long-term distributions of deformation, earthquakes and seismic hazard.

How to cite: Bonadio, R., Lebedev, S., Chew, D., Xu, Y., Fullea, J., and Meier, T.: Volcanism and long-term seismicity controlled by plume-induced plate thinning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10558, https://doi.org/10.5194/egusphere-egu25-10558, 2025.

The Makbal Complex is located within the western Tien Shan mountain range in NW-Kyrgyzstan. It’s central part comprises high-pressure (HP) and ultrahigh-pressure (UHP) metasedimentary and metabasaltic rocks of continental and oceanic origin, respectively.

Within the eastern part of the Makbal complex, abundunt 0.5 to 5 meter wide NW-SE oriented sills occur mainly within the Neldy group, but were also found in the Chymynsai and Kaindy groups.

The sampled rocks are altered to different extents with a dark to medium gray-green fine grained matrix comprising mainly chlorite and one to three millimeter sized porphyroclasts of amphibole, biotite, feldspar and carbonate, the latter most likely of secondary origin. Chlorite is not only the dominating matrix phase due to low grade alteration, it often replaces other mafic minerals such as amphibole, biotite and clinopyroxene. Although the majority of samples are highly altered, some phenocrysts are still fresh and include: (1) amphibole (kaersutite), (2) Mg-rich augite, (3) biotite of intermediate Fe-Mg content, (4) plagioclase of andesine to labradorite composition, and in some cases (5) K-feldspar. Based on the observed porphyritic texture and distribution of observed phenocrysts, the dikes can be classified as lamprophyres belonging mainly to the spessartite and to a lesser extent to the minette and vogesite groups.

Within the Nb/Y–Zr/Ti as well as the TAS diagrams (Pearce, 1996, Le Bas et al, 1986), the samples plot in the basalt, basaltic andesite, trachyandesite, and andesite fields. They all fall into the subalkaline field and most follow a shoshonitic or high-K calcalkaline trend in the SiO₂-K₂O diagram (Peccerillo and Taylor 1976). According to the Ti-Zr classification diagram after Pearce and Cann (1973) and the Nb/Yb−Th/Yb diagram (Pearce 2008), the lamprophyres were clearly emplaced within a compressional/continental arc setting. The chondrite normalized rare earth element pattern display a 100 times enrichment in light rare earth elements and a nearly constant 10 to 20 times enrichment of the middle and heavy rare earth elements excluding a deep-seated garnet bearing mantle as source of the lamprophyre melt. The patterns neither show a pronounced negative Nb-Ta anomaly nor any Eu anomaly.

Zircons could be extracted from an altered lamprophyre sample with kaersutite and plagioclase phenocrysts. The zircons are elongated with magmatic oscillatory zoning in CL image. The weighted mean ²⁰⁶Pb/²³⁸U age is 457 +/- 1 Ma, but a trend towards younger ages down to 440 Ma is observed. This age is similar to the intrusion age of a calcalkaline granodiorite body exposed approximately 5 to10 km to the west of the lamprophyre dikes. Both magmatic intrusives post-date the UHP event in the Makbal complex and bear important information to understand the full tectonic evolution. A genetic relationship of the lamprophyres and mafic enclaves found within the granodiorite is postulated.

How to cite: Gallhofer, D., Rechberger, J., Skrzypek, E., Orozbaev, R., and Hauzenberger, C. A.: Petrology, Geochemistry and Geochronology of Lamprophyres from the UHP Makbal Complex, NW-Kyrgystan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12274, https://doi.org/10.5194/egusphere-egu25-12274, 2025.

Age-progressive volcanic “hotspot” chains result from the passage of a tectonic plate over a deep-rooted thermochemical plume, thereby sampling the otherwise-inaccessible lowermost mantle. A common feature of oceanic hotspot tracks is the occurrence of two parallel volcanic chains. For example, the Hawaiian Loa and Kea chains are separated by a gap of 50 km, and likely sample the same ~100-km wide mantle melting zone. Several other tracks (including Tristan-Gough, Shona, the Wake seamounts, Tuvalu and Cook-Australs) are made up of a double chain with a 200-400 km spacing, but the origin of such widely-spaced double hotspots remains unknown.

Here, we explore 3D Cartesian geodynamic models of thermochemical plume ascent through the upper mantle. We investigate the effects of the lateral distribution of intrinsically-dense eclogitic material across the plume stem on upwelling style. For small eclogite contents, the plume rises as a “classical” columnar upwelling. For a wide range of intermediate eclogite contents in in the plume, the plume spreads laterally in the depth range of 300~410 km, where the excess density of eclogite is greater than above and below, as also predicted by [1]. This “Deep Eclogitic Pool” then splits up into two lobes that feed two separate shallow plumelets, particularly for significantly higher eclogite contents in the center than the periphery of the underlying plume stem. These two plumelets sustain two separate melting zones at the base of the lithosphere, which are elongated in the direction of plate motion due to interaction with small-scale convection. Such a “forked plume” morphology can account for hotspot chains with two widely-spaced (200~350 km) tracks and with long-lived (>5 Myr) coeval activity along each track. Some cases can even account for intermittent tripe-chain hotspot volcanism. Forked plumes may provide an ideal opportunity to study geochemical zonation of the lower-mantle plume stem, because each of the two plumelets robustly samples a distinct sector of the underlying deep plume stem, preserving chemical heterogeneity from the lowermost mantle.

We compare our model predictions to geochemical asymmetry evident along the Wake, Tuvalu and Cook-Austral double-chain segments, which together make up the extensive (>100 Ma) Rurutu-Arago hotspot track. The preservation of a long-lived NE-SW geochemical asymmetry along the Rurutu-Arago double chain indicates a deep origin, likely originating from the southern margin of the Pacific large low shear-velocity province. Our findings highlight the potential of the ocean-island basalt geochemical record to map lower-mantle structure over space and time, thus complementing seismic-tomography snapshots.

[1] Ballmer et al., 2013 (doi:10.1016/j.epsl.2013.06.022)

How to cite: Ballmer, M. and Finlayson, V.: Widely-spaced Double Hotspot Chains due to Forked Plumes sample Lower Mantle Geochemical Structure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12410, https://doi.org/10.5194/egusphere-egu25-12410, 2025.

The Rodrigues Ridge (Indian Ocean) is a N100°E oriented submarine volcanic structure stretching eastward of the Mascarene Plateau and toward the Central Indian Ridge (CIR). The geodynamic origin of Rodrigues’ volcanism is a matter of debate because the ridge neither follows the track of the Réunion hotspot nor the fabric of the oceanic lithosphere. To decipher the origin of this volcanism, we investigated the construction history of Rodrigues Island (i.e., the emerged portion of the ridge), by means of geomorphology, field observations, geochronology, and geochemistry. The morphology of Rodrigues Island’s slopes, the shape of the coral shelf, and unconformities observed in the field suggest that the island was constructed in two stages, including formation of a subcircular shield edifice, followed by formation of a N070°E ridge. This scenario is confirmed by K-Ar dating of groundmass and (U-Th)/He dating of zircon from volcanic rocks, suggesting that the circular edifice grew from 2.7 Ma to 2.5 Ma. Then, after a ca. 0.3 Myr hiatus and subsidence of the island, volcanic activity resumed from 2.2 Ma to 1.1 Ma, resulting in formation of the present-day ridge shape of Rodrigues Island. These ages are much younger than the unpublished ages ranging from 9.7 to 7.5 Ma reported for submarine volcanic rocks dredged on the flank of the Rodrigues Ridges.

Major/trace element and Sr-Nd-Pb isotopic analyses of the samples further show that the two stages of subaerial volcanism are chemically relatively homogenous, but much more enriched in incompatible elements than samples from the submarine ridge. Rodrigues Island was thus built by rejuvenescent volcanism of the submarine ridge. Available bathymetric and paleomagnetic data show that the Rodrigues Ridge propagates toward the east onto a less than 3 Ma old oceanic lithosphere (Demets et al., 2005) toward the CIR as en-échelon N070°E segments, called the Three Magi and the Gasitao ridges. The subaerial ridge shape of Rodrigues Island may thus belong to this array of en-échelon segments formed in the past 3 Ma.

Collectively, all the pieces of information suggest that the N100°E Rodrigues Ridge grew by protracted volcanism from ca. 10 Ma to ≤7 Ma, then from ca. 3.5 Ma to ca. 1 Ma by the propagation toward the CIR and coalescence of en-échelon N070°E segments of rejuvenated volcanism. Intriguingly, this temporality is coeval with the volcanic activity of Mauritius and Réunion Islands along the track of the Réunion hotspot, and particularly with the rejuvenescent volcanism of Mauritius since ca. 3.5 Ma. This coincidence favors a scenario of Rodrigues volcanism formed by capture of the Réunion plume ascending material by the CIR. We will discuss our results and their implications on the volcanic, structural and  geomorphology history of the Rodrigues Ridge.

How to cite: Seghi, J., Famin, V., Quidelleur, X., Gourbet, L., Danisik, M., Nauret, F., Révillon, S., Michon, L., and Arnould, M.: History of the Rodrigues Ridge, Indian Ocean: implications of the Réunion hotspot and the Central Indian Ridge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12411, https://doi.org/10.5194/egusphere-egu25-12411, 2025.

During the Lower Cretaceous, a significant tectonomagmatic activity around the South Atlantic Rift System led to the formation of numerous sedimentary basins, continental volcanism (basaltic and silicic), dike swarms, sill complexes, alkaline intrusions, and volcanic margins. In the northern Mantiqueira Province (Espírito Santo, Brazil), the Vitória-Ecoporanga belt is characterized by intense NW-SE-oriented faulting and fracturing zone, that hosts the Vitória Dikes, the northernmost low-Ti tholeiitic plumbing system of the Paraná Magmatic Province. These dikes exhibit microgabbroic textures and mineralogy composed mostly of plagioclase, clinopyroxenes, and Fe-Ti oxides. Geochemically, they have MgO = 3.83-7.2 wt.%, aligning with subalkaline tholeiitic basalts to basaltic andesites (total alkalis = 2.4-4.8 wt.%). These tholeiites are enriched in large ion lithophile elements, showing pronounced negative anomalies of Nb(-Ta) in comparison to Rb, Ba, U, Th, K, La, Ce, and Pb. They have ⁸⁷Sr/⁸⁶Sr_(i) ranging from 0.70994 to 0.70575, and εNd_(i) varying from -0.95 to -11.4, combined with heterogeneous values of Pb isotopes: ²⁰⁶Pb/²⁰⁴Pb_(m) (18.2-16.7), ²⁰⁷Pb/²⁰⁴Pb_(m) (15.6-15.4), and ²⁰⁸Pb/²⁰⁴Pb_(m) (38.9-37.6), thus suggesting some degree of lithospheric/crustal contribution. New ⁴⁰Ar/³⁹Ar and K-Ar geochronology confirms an Early Cretaceous filiation to the Vitória Dikes. After comparing the multidata types of the Vitória tholeiites with the existing dataset of the Riacho do Cordeiro Dikes of the Equatorial Atlantic Province, it is possible to suggest that both were interconnected during the Early Cretaceous. This reinforces therefore that the Vitória and Riacho do Cordeiro Dikes would constitute one of the largest low-Ti tholeiitic plumbing systems in the South Atlantic area associated with the Cretaceous breakup of the West Gondwana supercontinent. In this context, a parental E-MORB magma mixed with melts derived from the West Gondwanan lithosphere to form the low-Ti tholeiites. Although tracing a mantle plume as a direct geochemical contributor to low-Ti basalts is challenging and not straightforward, it cannot be completely dismissed. A smaller contribution from the plume may have been involved in the formation of potential parental liquids with signatures analogous to E-MORBs.

How to cite: Avelino de Macedo Filho, A., Janasi, V., Oliveira, A., Hollanda, M. H., Dantas, E., and Lino, L.: The Vitória Dike Swarm: A Key Piece in the Puzzle of Low-Ti Tholeiitic Magmatism Related to the South Atlantic Rift System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12432, https://doi.org/10.5194/egusphere-egu25-12432, 2025.

The origin, processes, and significance of intra-plate magmatism have long been debated, with the spotlight predominantly directed to oceanic volcanism. However, on continental margins the mechanisms that can generate or sustain prolonged magmatism throughout vast regions remains puzzling, with hotspot (s.s.), mantle plumes or edge-driven convection being invoked to explain these noteworthy manifestations.

Based on the age of emplacement and the present-day location of the magmatic occurrences, across the Central-East Atlantic Alkaline Province (CEAAP; Southwest Iberian Margin - SWIM, Morocco, Canarias and Madeira), the crustal paleogeographic location of emplacement was investigated. In parallel we analysed their relative motion paths relative to a stationary mantle reference and its associated tectonic plates.

Magmatism in this province, is revealed to be derived from a stationary super-plume ponded at the 660 km discontinuity at least since the late Cretaceous. Additionally, the recent discovery of new magmatic manifestation on the SWIM shows that magmatism in the region is more pervasive than anticipated. Our models indicate that this active mantle upwelling resulted in three main periods of activity and has been responsible for the irregular spatial-temporal distribution of magmatism. As tectonic plates wandered, alkaline magmatism that was initially emplaced within the Southwest Iberian Margin (103-70 Ma), was subsequently affecting continental Morocco (57-45 Ma), Canarias and Madeira (< 32 Ma), resulting in episodic and dispersed intra-plate magmatic activity, both on oceanic and continental crust. We estimate the position of the stationary mantle upwelling located between 20-30ºN and 10-20ºW.

Our models unravel prominent paleogeographic affinities of a common mantle source, linking late Cretaceous SWIM magmatism (e.g., Tore NW, Tore N, Ormonde, Sintra, Monchique) with present day Canarias and continental Morocco (e.g., Taourirt, Rekkame, Tamazert). Contrastingly, the motion paths from the occurrences on the SWIM (e.g., Torillon, Ampère and Unicorn), relate with the more recent magmatism at Madeira. Older magmatism from southern Canarias (e.g., Bisabuelas, Henry, Tropic) is revealed affine to the present-day location of the Sahara seamounts and Cape Verde. Younger magmatism in the High Atlas (e.g., Siroua, Sarrho, Oujda) appears to be as unrelated with the inherited SWIM mantle upwelling.

Results suggest that the intermittent emission of secondary mantle plumes (plumelets) ascended to the crust to form, as a whole, a cluster of dominantly non-aligned magmatism manifestations, including laccoliths, seamounts and volcanoes. Moreover, the spatial-temporal analysis of the magmatism on the CEAAP indicates a relative N-NW rejuvenation of emplacement. This is considered to have resulted from post-Cretaceous induced drag, as the plumelets progressively interacted with the base of the Nubian plate.

Acknowledgments: RP is supported Fundação para a Ciência e a Tecnologia, I.P. (FCT), Portugal, through the research unit UIDB/04035/2020 - GeoBioTec. JCD is supported by an FCT contract CEEC Inst. 2018, CEECINST/00032/2018/CP1523/CT0002.

How to cite: Pereira, R., Araújo, B., Duarte, J. C., and Mata, J.: Tracking a common mantle plume, from Iberia to Canarias-Madeira, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13333, https://doi.org/10.5194/egusphere-egu25-13333, 2025.

Classification of silica-undersaturated igneous rocks represents of one long-standing problems in igneous petrology. Mineralogical classification of foid-bearing rocks has been formally set [1,2] but no continuously applicable systematics and universal classification criteria have been developed for alkaline ultramafic rocks including melilite-bearing varieties and special rock groups [3,4,5]. Chemical classification is primarily based on the total-alkali – silica (TAS) diagram [2], but condensation of multiple components (CaO, MgO, MnO, FeO, Fe₂O₃, Al₂O₃, TiO₂, P₂O₅) in the diagram’s origin precludes its effective use for descriptive classification and petrogenetic interpretation involving mafic and ultramafic rocks. Universal availability and accuracy of whole-rock geochemical data together with fine-grained or glassy character of many volcanic rocks on one hand and historical origin of petrographic classifications in mineral mode and involvement of mineral-melt relations in magma evolution and crystallization on the other hand require consistent and universal link between the chemical and mineralogical approaches. This is a component transformation problem, which can be approached from several different perspectives: (i) component transformation sensu stricto preserving the composition space dimensionality, (ii) reduction of space dimensionality involving projecting or condensing components, usually for graphical applications or for condensation of complex natural compositions into simplified synthetic (e.g., experimental) systems, and (iii) subsection of the space leading to multiple combinations of new components; this approach is embodied in norm calculations. The widely applied tool – the CIPW norm [6,7] – suffers from several inadequacies when applied to silica-undersaturated rocks: (i) persistence of anorthite to critically undersaturated state, (ii) absence of melilite or its end-members, and (iii) incomplete or incorrect feldspar-foid compatibility relations. In this contribution we develop a condensed composition space to represent principal chemical variations in silica-undersaturated rocks. The condensation offers uniform treatment of diverse heteromorphic relations in dependence on temperature, pressure or water activity. The breakdown of plagioclase to aluminous clinopyroxene with decreasing silica activity and subsequent transformation of clinopyroxene to melilite is visualized in chemographic projections via olivine and nepheline, involving thermodynamically based phase relations as a function of silica activity. Finally, we define intermediate members of feldspar, nepheline, clinopyroxene and melilite solid solutions and develop a more comprehensive, quasimodal normative calculation for anhydrous silica-undersaturated igneous assemblages. This approach offers successive, rigorous steps for (i) overall classification and interpretation of chemical variations independently of mineral assemblages, (ii) projective analysis for comparison of chemical variations with experimental or thermodynamic phase relations, and (iii) algorithm for normative calculation approaching modal associations. This provides a uniform basis for both descriptive classification as well as genetic interpretation of silica-undersaturated magmas and rocks.

References: [1] Streckeisen A., 1965. Geol. Rundsch. 55, 478-494; [2] Le Maitre R.W., ed., 2002. Igneous Rocks. A Classification and Glossary of Terms, Cambridge Univ. Press; [3] Woolley A.R., et al., 1996. Can. Mineral. 34, 175-186; [4] Dunworth E.A., Bell K., 1998. Can. Mineral. 36, 895-903; [5] Tappe S., et al., 2005. J. Petrol. 46, 1893-1900; [6] Cross W., et al., 1902. J. Geol. 10, 555-690; [7] Janoušek V., et al., 2016. Geochemical Modelling of Igneous Processes, Springer.

How to cite: Dolejs, D.: Chemographic projections and normative calculations for silica-undersaturated igneous rocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13724, https://doi.org/10.5194/egusphere-egu25-13724, 2025.

Iceland has long been a focal point of geophysical research due to its potential association with a mantle plume. While earlier studies generally supported a plume originating from the core-mantle boundary with minimal lateral displacement during ascent, recent high-resolution tomographic images have indicated the presence of a curved, ascending mantle plume beneath Iceland. Consequently, the detailed source region and morphology of the Iceland plume remain debated. In this study, we provide new constraints on the Iceland mantle plume by examining the structure of the mantle transition zone (MTZ) using SS precursor imaging. We collected a large SS precursor dataset from 1976 to 2023 and adopted a recently proposed multi-dimensional reconstruction method to enhance the weak SS precursor phases for improved probing of the MTZ.

Our seismic observations reveal substantial thinning (~230 km) of the MTZ beneath Iceland compared to the regional average of 238 km and the global average of 242 km. This thinning is characterized by a slight depression of the 410 km discontinuity (~5 km) and a pronounced uplift of the 660 km discontinuity (~12 km). Temperature anomalies estimated using Clapeyron slopes suggest respective perturbations of +50 K and +300 K at the 410 and 660 discontinuities beneath Iceland. The former estimate is significantly lower compared to the reported thermal anomalies at major hotspots, e.g., ΔT410 ≈ +200 K west of Hawaii. This large temperature contrast suggests that either strong thermal heterogeneities exist across the MTZ or an alternative mechanism is required to explain the thinning of the MTZ beneath Iceland. We suggest that the mildly depressed 410 may be partly attributed to the influence of water during the ascent of the mantle plume. The presence of water effectively reduces pressures for the phase transition from olivine to wadsleyite, causing upward displacement of the 410 km discontinuities. This result suggests that variations in water distribution and content play a critical role in the structural anomalies observed in the MTZ beneath Iceland. The observed thinning of the MTZ supports the existence of a deep mantle plume, potentially supplying material to the shallow hotspots near the Iceland-Mid-Atlantic Ridge.

How to cite: Jiang, X., Chen, Y., Oboue, Y. A. S. I., Wang, J., Fei, H., and Thomas, C.:  Seismic Imaging of Mantle Transition Zone Suggests Hot Deep Plume Underneath Iceland-Mid-Atlantic Ridge Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16914, https://doi.org/10.5194/egusphere-egu25-16914, 2025.

The Mascarene Basin, between Madagascar, the Seychelles Plateau, and the Réunion hotspot track, is an ocean lithosphere whose geodynamic evolution remains enigmatic in many aspects. Part of the enigma concerns the unexplained extinction of the Mascarene mid-ocean ridge ca. 62 Ma ago and the shift of oceanic accretion to a new ridge (i.e., the Carlsberg Ridge) further north. The presence and timing of the Amirante aborted subduction trench (between Madagascar and the Seychelles) is another enigmatic aspect of the regional geodynamics (e.g., Rodriguez, CRGEOS 352, 235-245, 2020).

To shed light on these conundrums, we investigated the architecture of the Mascarene Basin during the MD245 “MASC” oceanographic cruise onboard the Marion Dufresne II research vessel. Bathymetric surveying revealed numerous seamounts at the axis of the paleo-ridge, along paleo-transform faults, and some also on the southern flank of the paleo-ridge. Interestingly, all the seamounts are located in the continuity of the Amirante paleo-subduction trench. Dredging operations on the seamounts recovered a suite of highly differentiated magmatic rocks ranging from biotite-rich basalts to rhyolites and granodiorites. Zircon and apatite (U-Th)/He data from these igneous rocks suggest that the seamounts formed during a protracted period between ca. 67 Ma and ca. 43 Ma.

Does this highly differentiated magmatism at 67-43 Ma reflect a residual activity of the ridge under extinction? Or, a nascent arc magmatism associated with the Amirante subduction? Further geochemical analyses are required to answer this question. Regardless, we note that the 67 Ma date coincides with the first magmatic manifestation of the Réunion plume as the Deccan traps, whilst the 43 Ma date corresponds to the deceleration of India and the passage of the Somalia Plate over the Réunion plume. We thus posit that differentiated magmatism, ridge extinction, and subduction initiation and abortion could be all related to the Réunion plume. Indeed, the Réunion plume is suspected to have pushed the Indian Plate toward Asia, causing its drastic acceleration and slowdown from 67 to 43 Ma (Cande and Stegman, Nature 475, 47-52, 2011). We further propose that the Réunion plume had a symmetric push effect on the Somalia Plate, converting oceanic spreading into compression, hampering spreading of the Mascarene Ridge, and eventually leading to the Amirante subduction. Compression (and differentiated magmatism) vanished when the Somalia Plate passed over the Réunion hotspot.

How to cite: Famin, V., Danišík, M., Révillon, S., Zaragosi, S., Beaufort, L., Sauter, D., Tzevahirtzian, A., Lebeau, G., Seghi, J., Leduc, G., Bassinot, F., Eude, A., Vinet, N., Quidelleur, X., Nauret, F., Michon, L., and Bachèlery, P. and the MASC Team: Ridge extinction in the Mascarene Basin due to the Réunion hotspot: preliminary results of the MASC Cruise, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17727, https://doi.org/10.5194/egusphere-egu25-17727, 2025.

Nyamuragira volcano is an active volcano near the city of Goma in the Democratic Republic of the Congo, situated about 25 kilometers north of Lake Kivu. It has been described as Africa's most active volcano and has erupted over 40 times since 1885. on 2 January 2010 Nyamuragira began spewing out lava flows. Extensive lava flows from the 2010 eruption can be seen on satellite photographs reaching 25 kilometers south-west to Lake Kivu, about 22 kilometers north-west and 35 kilometers north-north-east. The volcano erupted again on 5 November 2011.That eruption produced a 400-meter-high column of lava, and it is said to have been its largest eruption in 100 years. Volcanic activity attributed to The Kivu rift resulted from a sub-equatorial extensional motion and normal faulting and accompanied with seismological activities.  It suggests a complicated lower and upper crust tectonic patten and old neo tectonic settings.

It is a challenge to determine active tectonic and geologic structure attributed to magma eruption. Shallow and deep geologic structures around the volcanic area. Heterogeneities of the lithosphere and its impact on the volcanic activities. Old and neo tectonics responsible for volcanic and seismic activities. quantitatively predict the position and direction of dike intrusions and resulting eruptive fissures at volcanoes, because they are governed by the interplay between several factors, such as a heterogeneous regional stress field, preexisting discontinuities and heterogeneous and anisotropic properties of rocks.

  Radar altimetry data has been used to derive gravity and its variations over the world's oceans and an excellent tool for mapping sea floor structures, including tectonics, sea mounts and rifts. On the other hand, the Gravity Recovery and Climate Experiment (GRACE) satellite mission has widely demonstrated its sensitivity to ongoing mass redistribution within the various sub-systems of the earth. Finally, GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite is the first satellite mission that observes gradient of the Earth gravity field from space.  Integrated satellite gravity data have been used to delineate the tectonic settings, magma referred pathway, magma reservoirs and vertical dikes.

How to cite: Zahran, K.: Volcanic activity at the East African Rift System as seen from space, case study Nyamuragira Volcano, D.R. Congo., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17876, https://doi.org/10.5194/egusphere-egu25-17876, 2025.

Density variations within the Earth’s mantle drive convective Stokes flow and shape key geophysical observables, one of which is dynamic topography, defined as the surface deflection due to normal stresses exerted on the base of the crust. For decades, predicted dynamic topography has differed from observations in two regards. First, the predictions contain too much power at long wavelengths  i.e > 10,000 km). Secondly, there is insufficient power at shorter wavelengths (i.e. < 1,000 km). Here, the propagator method is utilised to solve for the Stokes equation and self-gravitation within a spherically symmetric viscosity regime. To solve these equations, kernels (i.e. Green’s functions) are obtained, which represent the sensitivity of observables like surface and core-mantle boundary topographies to density anomalies at varying depths and wavelengths within the mantle. These kernels are strongly sensitive to viscosity structure. In exploring the parameter space within the forward problem, predicted dynamic topography must match the observational dataset of dynamic topography, containing over 14,000 measurements. The geoid is sensitive to the Earth’s (relative) viscosity structure, and therefore provides an excellent primary constraint. In constructing predicted dynamic topography, a whole-mantle density model is required, usually  acquired from a global shear-wave velocity model and using a constant scaling factor from mineral physics. A large range of tomographic models (n = 17) are utilised to undertake a more comprehensive search for the most appropriate mantle structure. In isolation, the lower mantle is found to produce several hundred metres of surface dynamic topography and match the long-wavelength features remarkably well. Current whole-mantle tomographic models result in predictions with insufficient short-wavelength features, as compared to residual topography studies. Hybrid density models are therefore constructed by smoothly blending high-resolution upper-mantle models, such as SL2013, with the previous suite of whole-mantle models, resulting in a predicted dynamic topography signal which better matches observed dynamic topography on shorter length scales. An improved velocity-to-density conversion is explored, by introducing a depth-dependence on the conversion and focussing on the anelastic effects within the upper mantle. Reconciling predicted and observed dynamic topography strengthens the integration of dynamic topography with other observable fields, such as the geoid, and offers a more comprehensive framework to study Earth’s interior processes. 

How to cite: Jacob, I., White, N., and Al-Attar, D.: Probing Mantle Structure to Reconcile Predicted and Observed Dynamic Topography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-908, https://doi.org/10.5194/egusphere-egu25-908, 2025.

Surface features in oceanic basins, such as mid-oceanic ridges, hotspots, seafloor subsidence, and fracture zones, result from geodynamic processes in the uppermost mantle. Insight into these processes are obtained from tomographic imaging using surface waves. However, the poor distribution of earthquakes and seismic stations, as well as noise in seismic data, give rise to spatial resolution artefacts and errors in tomography models, complicating their interpretation.

We constructed SS3DPacific, a model of the vertically-polarised shear-wave velocity structure of the Pacific uppermost mantle and surrounding regions. The model derives from Rayleigh-wave phase delays, that we measured along with an estimation of their uncertainty. SS3DPacific is accompanied by 3D resolution and uncertainty. To obtain this information, we combined the SOLA inverse method to control and produce resolution and uncertainty with finite-frequency theory for Rayleigh waves, leading to a 3D model.

In this talk, I will present SS3DPacific, its 3D resolution, and uncertainty. The model shows well-known large-scale features such as cratons, ridges, and the increase of seismic velocity with distance from mid-oceanic ridges. Detailed analysis of the 3D resolution reveals strong spatial artefacts, particularly vertically, which manifest themselves in the form of structural depth leakages. This effect, expected for this type of surface-wave tomography, will ultimately bias the analysis of the lithosphere cooling process if not accounted for. Additionally, SS3DPacific shows an intriguing pattern of bands of velocity variations aligned with fracture zones.

Given the availability of 3D resolution and uncertainty quantification, SS3DPacific can be utilised in studies aimed to assess mantle circulation models, and thus dynamic processes in the Earth.

How to cite: Latallerie, F., Zaroli, C., Lambotte, S., Maggi, A., Walker, A., and Koelemeijer, P.: SS3DPacific: Structure of the Pacific uppermost mantle with 3D resolution and uncertainty, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1081, https://doi.org/10.5194/egusphere-egu25-1081, 2025.

The Hawaiian-Emperor Chain in the North Pacific features a conspicuous 60° bend that has been the subject of multiple interpretations, including an abrupt change in Pacific plate motion in the Eocene (~47 Ma), a rapid southward drift of the Hawaiian hotspot before the formation of the bend, or a combination of the two factors. The latest geodynamic model has proposed that 30-35° of the Hawaiian-Emperor Bend (HEB) was caused by the sudden westward movement of the Pacific Plate at the latitude of Hawaii around 50 Ma, which occurred as a result of the cessation of the slab pull force generated by intraoceanic subduction in the northern Pacific. The remaining 25-30° of the bend is attributed to the southward movement of the Hawaiian hotspot. But according to geometric analysis and back extrapolation of plate reconstructions, a stronger westward component in the motion of the Hawaiian hotspot is required to achieve a better fit of the HEB. However, there is no geodynamic justification for a significant westward component in the drift of the hotspot.

Here, using geometric analysis with constraints from plate kinematics, we show a significant longitudinal hotspot motion is required to fit the Hawaiian-Emperor Chain. Further application of global mantle convection models reveals a westward (by ~6°) and then an eastward (by ~2°) hotspot drift in addition to the southward motion before and after the bend, with the westward motion primarily controlled by the intraoceanic subduction in Northeast Pacific. While both the westward and southward motion are required to fit the seamount chain, the former contributes ~20 degrees to the bend angle, larger than the later, challenging traditional views. Combining geodynamically-predicted Pacific Plate motion change at 47 Ma, our model provides a nearly perfect fit to the seamount chain, suggesting plate-mantle reorientation as the ultimate cause. It also suggests that the Hawaiian plume conduit is tilted towards the southwest, solving the long-lasting debate on the source of the Hawaiian plume among seismological studies.

How to cite: Zhang, J. and Hu, J.: Dynamics of longitudinal Hawaiian hotspot motion and the formation of the Hawaiian-Emperor Bend, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1975, https://doi.org/10.5194/egusphere-egu25-1975, 2025.

Mantle convection alters Earth’s ellipsoidal shape and modifies its moment of inertia, leading to rotation-axis shifts known as true polar wander (TPW). By combining seismic tomography with the Back-and-Forth Nudging (BFN) method, we created a time-dependent convection model that reconstructs mantle density evolution and Earth’s moment of inertia over the last 70 million years. This modeling framework closely agrees with independent paleomagnetic data on Cenozoic changes in Earth’s rotation pole, notably reproducing the previously unexplained U-turn in TPW around 50 million years ago.

Our results show that TPW can exceed five degrees, despite stabilizing factors such as high viscosity in the lower mantle and Earth’s remnant rotational bulge. Verification of predicted variations in Earth’s ellipsoidal figure, based on paleomagnetic constraints, provides a robust reference point for forecasting convection-induced dynamic flattening. Over the 70-million-year interval, we document changes in flattening that range from -0.2% to +0.1% during the Paleogene. Furthermore, our predictions of Paleogene axial precession frequency align with recent independent cyclostratigraphic analyses, offering strong evidence for the accuracy of our model and reinforcing the hypothesis of diminished luni-solar tidal dissipation during that period.

How to cite: Forte, A. M., Rowley, D., Rowley, D., and Kamali Lima, S.: Resolving 70 Million Years of Earth’s True Polar Wander and Precession: Paleomagnetic Validation of a Seismic Tomography–Based Mantle Convection Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2596, https://doi.org/10.5194/egusphere-egu25-2596, 2025.

Dynamic uplift may be expressed in the geologic record by the presence of unconformities, which represent periods of erosion and/or halted sedimentation. One distinct example, the early Miocene unconformity (EMU), formed shortly before the impingement of the Yellowstone plume in the northern Rocky Mountains. The most complete geologic record around this event is preserved in southwest Montana. There, we sampled eight sedimentary sections crossing the EMU. Our magnetostratigraphic study in combination with published radiometrically-dated ash layers determines the EMU ended at ~20.1 Ma and lasted up to 1.5 Myr. We found that the EMU is marked by an abrupt increase in magnetite concentration coincident with a shift in detrital zircon age spectra. These data indicate a rapid reorganization in sediment source likely caused by the emplacement of the Columbia River flood basalt synchronous with a shift in the North American drainage divide. The passage of the Yellowstone plume and/or the onset of Basin and Range extension likely provided the tectonic stimulus for the widespread unconformity and changes in sediment source.

How to cite: Gerritsen, D., Gilder, S., Chen, Y.-W., Wack, M., and Ludat, A.: Magnetic tracing of lost time in Cenozoic sediments: Testing dynamic topography of the Yellowstone plume, USA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3202, https://doi.org/10.5194/egusphere-egu25-3202, 2025.

Mantle convection is a crucial component for providing driving and resisting forces for horizontal motion of tectonic plates, as well as for generating non-isostatic vertical motion commonly termed “dynamic topography”. These two kinds of surface motion are often investigated in isolation. However, the existence of a thin, mechanically weak asthenosphere allows us to study mantle convection in the context of Couette/Poiseuille flow, which links mantle flow properties to temporal changes in both horizontal and vertical motions. In this study, we utilize publicly available finite rotations and stage-resolution stratigraphic dataset in the North Atlantic region to investigate its surface-motion history in early Paleogene, which coincides with the peak Icelandic plume activity deduced from independent geologic constraints. We find that our inferred horizontal and vertical motion changes are temporally correlated. We examine this correlation through a quantitative torque analysis, which incorporates an analytic Couette/Poiseuille flow model. We parameterize this flow model in terms of observed kinematics coupled with flow-flux estimates of Icelandic plume and/or Farallon slab activity. Our analysis indicates (1) that torque-variation tied to the Icelandic plume flux closely resembles our kinematic inferences, and (2) that the inclusion of slab flux does not modify such a scenario significantly. In light of these inferences, our efforts shed light on the role of asthenospheric channelized flow flux in influencing the North Atlantic surface expressions in early Paleogene.

How to cite: Wang, Z. R., Iaffaldano, G., and Hopper, J.: North Atlantic surface-motion changes in early Paleogene: Observations and geodynamic interpretations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3336, https://doi.org/10.5194/egusphere-egu25-3336, 2025.

The lateral and vertical thermochemical heterogeneity in the mantle is a long-standing question in geodynamics. The forces that control mantle flow and therefore Plate Tectonics arise from the density and viscosity lateral and vertical variations. Satellite gravity data are a unique source of information on the density structure of the Earth due to its global and relatively uniform coverage, which complements gravimetric terrestrial measurements. Gravity data (geoid, gravity, gravity gradients) sense subsurface mass anomalies have proven to be helpful in determining the Earth’s thermochemical field in virtue of density’s relatively stronger dependence on rock composition compared to seismic velocities. However, the inversion of gravity data alone for the density distribution within the Earth is an ill-posed problem with a highly non-unique solution that requires regularization and smoothing, implying additional and independent constraints. A common approach to estimate the density field for geodynamical purposes is to simply convert seismic tomography anomalies sometimes assuming constraints from mineral physics. Such converted density field does not match in general with the observed gravity field, typically predicting anomalies the amplitudes of which are too large. Furthermore, a complete description of the Earth’s gravity field must include the internal density distribution and must satisfy the requirement of mechanical equilibrium as well. Therefore, the deformation of the density contrast interfaces (surface of the Earth and Core Mantle Boundary-CMB, primarily) must be consistent with the 3D mass distribution for a given rheological structure of the Earth. With the current resolution of modern tomography models and integrated geophysical-petrological modelling it is possible to consistently predict the topography of the mineral phase transitions across the transition zone (i.e., olivine à wadsleyite, and ringwoodite+majorite à perovskite+ ferropericlase) based on a temperature and chemical description of the Earth. However, for a consistent representation of the gravity field such thermochemical (i.e., density) 3D models must be compatible with the mantle flow arising from the equilibrium equations that explains both the surface topography (dynamic + isostatic-lithospheric components) and the CMB topography. Here we present a new inversion scheme to image the global thermochemical structure of the whole mantle constrained by state-of-the-art seismic waveform inversion, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission) and surface heat flow data, plus surface and CMB dynamic topography (Stokes flow). The model is based upon an integrated geophysical-petrological approach where mantle seismic velocities and density are computed within a thermodynamically self-consistent framework, allowing for a direct parameterization in terms of the temperature and composition variables.

How to cite: Fullea, J., Ortega-Gelabert, O., Lebedev, S., Martinec, Z., Afonso, J. C., and Root, B.: Geodynamic modelling the thermochemical structure of the Earth's mantle using integrated geophysical and petrological inversion of surface wave and satellite gravity data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3690, https://doi.org/10.5194/egusphere-egu25-3690, 2025.

We begin with a simple mantle dynamics model that integrates subducted lithosphere and large-scale upwelling plumes over the last 300 million years (Ma). Our calculations are performed using several plate models and mantle reference frame models, which are constructed based on various surface indicators, including geological data, thermal data from boreholes, a compilation of global surface volcanism, a reassessment of hotspot classifications, and paleomagnetic data.

A Monte Carlo approach identifies the optimal mantle viscosity and density contrasts that explain present-day geoid, gravity, and gravity gradients. Results highlight a consistent degree-2/order-2 mantle mass anomaly over 300 Ma, linked to the stable subduction girdle around the Pacific Ocean and two equatorial, quasi-antipodal mantle domes.

Time-dependent calculations of the Principal Inertia Axis (PIA) and True Polar Wander (TPW) reveal significant shifts in Earth's rotation axis, including cusps caused by the cessation of Paleo-Tethys and Tethys subduction and notable polar wander events .

Dynamic topography is computed and compared with geological and current observations, providing further insight into mantle dynamics and Earth's surface evolution.

How to cite: Greff-Lefftz, M., Robert, B., and Besse, J.: 300 Million Years of Mantle Dynamics: Subduction, True Polar Wander, and Earth's Surface Evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3805, https://doi.org/10.5194/egusphere-egu25-3805, 2025.

The Lithosphere-Asthenosphere Boundary (LAB) demarcates the transition from a conductive thermal lid to a convecting asthenosphere below. The Southwestern United States presents an intriguing natural laboratory for investigating the processes at play in this critical boundary: intraplate volcanism is abundant and geochemical and geophysical analyses suggest the presence of a sub-lithospheric layer of partial melt. It has been suggested that a change in mantle strength at the top of the melt-bearing layer helps to create the LAB, indicating that melt stability is an important factor in understanding lithospheric dynamics. The mechanism, or interplay between mechanisms, that govern the LAB has implications for geodynamic modeling as well as for understanding the long-term evolution of lithosphere and volcanism. The analysis presented here is based on seismic observations of surface waves and converted body waves, which are used to determine 1-D profiles of shear wavespeed (Vs) throughout the Southwestern United States, from the surface to 300 km depth. The LAB is determined from the depth location of negative Vs gradients within the mantle. From the Vs profiles, we estimate temperature within the upper mantle, using two different geophysical interpretive toolkits. These toolkits each predict geophysical properties via forward-modeling of temperature, melt fraction, and/or compositional state, and assumptions made within the forward-modeling can yield large discrepancies in interpreted temperature. We leverage temperatures derived from geochemical thermobarometry as a constraint to guide our choice of method and attenuation parameterization. From this workflow, we report inferred temperature at and below the gradient inferred to be the LAB, and evaluate the relationship of these temperatures to the mantle adiabat and the peridotite solidus. Temperatures are near the solidus in portions of the lithospheric mantle, particularly in the Basin and Range province, suggesting that melting does play a role in defining the LAB, but not in every location. Moreover, the prevalence or absence of partial melt appears to be connected to regional variations in deformation style, surface heat flow, and topography. Finally, we note that additional constraints on hydration state and composition of the lithosphere, as well as the geometry and distribution of partial melt, will improve the workflow presented here.

How to cite: Golos, E. and Fischer, K.: Seismic constraints on temperature and melting at the Lithosphere-Asthenosphere Boundary in the Southwestern United States, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3867, https://doi.org/10.5194/egusphere-egu25-3867, 2025.

Seismological observations suggested that Earth’s inner core presents complex heterogeneity and anisotropic structure. The key to understand the structure of Earth’s inner core is to study the mineralogical composition and dynamic mechanism of the anisotropic structure of Earth’s inner core. Hexagonal close-packed (hcp) and body centered cubic (bcc) Fe alloys both have seismically anisotropic features under temperature and pressure conditions of the Earth’s inner core. When the fast axis can be oriented along the Earth’s rotation axis, the anisotropic characteristics of the Earth’s inner core, which is fast in the north-south direction and slow in the equatorial direction, can be explained. The input of light elements into Fe alloys significantly changed the anisotropy of Fe alloys. Particularly, the fast axis orientation of superionic Fe-H alloys changes with the increase of H contents in those alloys. Interestingly, superionic Fe alloys present both ionic diffusion and seismic velocity anisotropy, which establish a potential connection between the lattice preferred orientation (LPO) anisotropic structure and dipole geomagnetic field. If the Earth’s inner core is under the superionic condition, the directional diffusion of light elements driven by the geomagnetic field could result in the presence of the lattice internal stress which would then result in the LPO. The anisotropic superionic fibers explain the anisotropic seismic velocities in the IC, suggesting a strong coupling between the IC structure and geomagnetic field.

How to cite: He, Y.: Superionic inner core and anisotropic structure driven by geomagnetic field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4922, https://doi.org/10.5194/egusphere-egu25-4922, 2025.

Global topography plays a fundamental role in shaping climate, influencing atmospheric circulation and precipitation patterns through orographic effects. While much of Earth's topography arises from isostatic support due to variations in crustal and lithospheric thickness and density, a significant portion of up to 1-2km results from dynamic forces driven by slow yet vigorous mantle convection. Despite decades of research on the spatial and temporal evolution of such ‘dynamic topography’, its impact on global climate remains largely unexplored. In this study, we address this gap by quantifying the influence of mantle-induced dynamic topography on present-day atmospheric circulation and precipitation patterns. Using an Earth Model of Intermediate Complexity forced with different models of global dynamic topography, we isolate the mantle’s contribution to climate patterns. Our findings reveal prominent climatic effects linked to mantle dynamics, particularly along the American Cordillera, the East African Rift System, and other regions across latitudes which are critical to biodiversity and the evolution of life. These results uncover a hitherto unknown connection between Earth's deep interior and surface environments, with the mantle dynamics as active driver of climate processes, enhancing our understanding of the Earth System. By linking mantle dynamics to global climate, our study offers new opportunities for paleoclimate investigations and insights into how geodiversity and biodiversity have co-evolved throughout Earth's history.

How to cite: Sternai, P., Meroni, A., Vaes, B., and Pasquero, C.: Dynamic Topography and The Mantle Forcing on Climate: A Missing Link in Earth System Science, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5805, https://doi.org/10.5194/egusphere-egu25-5805, 2025.

Within the 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 at magnetic high-latitude flux lobes (HLFLs). The focus is on four target regions on the Northern Hemisphere: Siberia, Canada, the North Atlantic, and Indonesia. While Siberia and Canada show the HLFLs, the North Atlantic should be the location of a third postulated HLFL, but this area does not show an intense-flux signal in the magnetic field. The region beneath Indonesia and the Indian Ocean is characterized by an area of intense magnetic flux that changes direction and moves westwards over time. Our aim is to understand whether mineralogy and seismic structure (i.e., thermal constraints) could be responsible for the different magnetic signatures at the core mantle boundary (CMB). This is done by combining two approaches: seismic anisotropy (KIT) and seismic reflections (University of Münster) near the CMB (https://www.geo.lmu.de/deepdyn/en/projects/ritter-joachim-und-thomas-christine-understanding-the-influence-of-deep/).

To study anisotropy, we measure 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), e.g., between SKS and SKKS phases, as they are a clear indication for a lowermost mantle contribution to the splitting signal. For the target region underneath Siberia, SWS measurements are obtained using earthquakes with epicenters in Southeast Asia recorded at stations in the North of Scandinavia and Svalbard as well as earthquakes with epicenters in Central America recorded at the station ULN in Mongolia. These SWS measurements indicate that for the discrepant pairs the phases with piercing points closer to the center of the HLFL beneath Siberia show splitting while the phases more distant to the HLFL do not show anisotropy. Furthermore, we present first results for the target region North Atlantic. Based on our SWS measurements, we will derive structural and mineralogical anisotropy models using the MATLAB Seismic Anisotropy Toolbox (Walker and Wookey 2012). To test these models, we then simulate synthetic seismograms using AxiSEM3D (Leng et al. 2016, 2019).

How to cite: Fröhlich, Y., Dorn, F., Dillah, M. I. F., and Ritter, J. R. R.: Investigation of seismic anisotropy in the D’’ layer and at the CMB underneath Siberia and the North Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6615, https://doi.org/10.5194/egusphere-egu25-6615, 2025.

In their seminal work, Munk and MacDonald (1960) showed that considering only the crustal contribution to the Earth’s moment of inertia (MOI) would predict a rotation axis passing through a location near Hawaii – clearly inconsistent with the present-day geographic pole. This finding implied there must be additional mass anomalies, which the authors speculated to be in the convecting mantle, that realign the rotation axis with the observed North Pole.
Modern geodynamic studies confirm that isostatic compensation of crustal thickness and density variations explains much of Earth’s observed topography, yet the crust’s gravitational contribution is often overlooked because it is relatively small compared to that generated by density anomalies in the mantle. As a result, residual topography (the difference between observed and isostatic topography) remains a prominent global constraint on the amplitude and spatial distribution of mantle density anomalies, while residual geoid (the difference between observed and crustal isostatic geoid) is utilized far less frequently. Crucially, this omission disregards the crust’s influence on Earth’s moment of inertia (MOI) and, by extension, its impact on the location of the rotational axis. Overlooking crustal mass heterogeneities can therefore lead to unrealistic (non-Earth-like) inferences of mantle density anomalies that do not correctly predict the location of the present-day rotational axis.
By analyzing satellite-derived non-hydrostatic geoid data and comparing modeled and observed moments of inertia, we find that preserving the present-day location of the rotational axis requires systematically accounting for crustal contributions. We implement a second order-accurate isostasy model – which integrates crustal buoyancy variations in a deformable crust – to more accurately capture the interplay between surface topography, the geoid, and the convective mantle. Neglecting this refinement not only fails to preserve the present-day rotational axis position but also compromises True Polar Wander (TPW) predicted by time-dependent mantle convection simulations.
Our findings suggest that integrating a second-order accurate isostasy framework into global mantle convection models is essential for producing consistent TPW trajectories, ensuring alignment between the modeled rotational axes and Earth’s observed pole positions.

How to cite: Kamali Lima, S., Forte, A. M., Greff, M., and Glišović, P.: Crustal Contributions to Moment of Inertia as Key Constraints for Earth-Like Mantle Convection Models: “Munk & MacDonald (1960)” Revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7454, https://doi.org/10.5194/egusphere-egu25-7454, 2025.

The tectonic evolution of the Tibetan Plateau has been influenced by continental collision and post-collisional convergence of Indian and Eurasian plates, both of which have undoubtedly imposed their imprints on the lithosphere and upper-mantle structures beneath the collision zone. However, the mode by which the Indian Plate has subducted beneath Tibet, and its driving forces, have been highly uncertain. Here, we present seismic evidence from a full-waveform tomographic model that reveals flat subduction of the Indian Plate beneath nearly the entire plateau at ~300 km depth, implying that the slab may have transitioned to positive/neutral buoyancy and is no longer capable of supporting steep-angle deep subduction. The horizontal distance over which the flat slab slides northward increases from west (where it collides with the Tarim lithospheric keel) to east (where it has resided approximately north of the Songpan-Ganzi Fold Belt beyond the Qiangtang Block). The Asian lithosphere is subducting beneath northeastern Tibet without colliding with the Indian slab. The low-velocity zone, with a thickness of 50-110 km, sandwiched between the Tibetan crust and Indian slab, is positively correlated with the high-elevation, low-relief topography of Tibet, suggesting partial melting of the uppermost mantle that has facilitated the growth and flatness of the plateau by adding buoyant material to its base. We propose that deep mantle convective currents, traced to the Réunion plume and imaged as large-scale low-velocity anomalies from the upper mantle under the Indian Plate downward towards the uppermost lower mantle under the Baikal-Mongolia Plateau, are the primary force driving the ongoing India-Asia post-collisional convergence.

How to cite: Ma, J., Song, X., Bunge, H.-P., Fichtner, A., and Tian, Y.: Wholesale flat subduction of Indian slab and northward mantle convective flow: Plateau growth and driving force of India-Asia collision, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7772, https://doi.org/10.5194/egusphere-egu25-7772, 2025.

The transport of heat from the interior of the Earth drives convection in the mantle, which involves the deformation of solid rocks over billions of years. Significant advancements have been made over recent years to study lower mantle assemblages under relevant pressure and temperature conditions, which have confirmed the usual view that ferropericlase is weaker than bridgmanite. However, natural strain rates are 8 to 10 orders of magnitude lower than those observed in the laboratory, and remain inaccessible to us. Once the physical mechanisms of the deformation of rocks and their constituent minerals have been identified, it is possible to overcome this limitation thanks to multiscale numerical modeling, which allows for the determination of rheological properties for inaccessible strain rates. This presentation will demonstrate how this theoretical approach can be used to describe the elementary deformation mechanisms of bridgmanite and periclase. These descriptions are compared with available experimental results in order to validate the theoretical approach. In a subsequent phase, the impact of very slow strain rates on the activation of the aforementioned mechanisms is evaluated. Our findings indicate that significant alterations in deformation mechanisms can occur in response to changes in strain rate.

How to cite: Carrez, P., Cordier, P., Gouriet, K., Weidner, T., Van Orman, J., Castelnau, O., and Jackson, J.: On the effect of strain rates on the deformation creep mechanisms in deep Earth mantle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8576, https://doi.org/10.5194/egusphere-egu25-8576, 2025.

Reconstructing the thermo-chemical evolution of Earth’s mantle and its diverse surface manifestations is a grand challenge in the geosciences. Achieving this requires the development of a digital twin -- a dynamic digital representation of Earth’s mantle across space and time, constrained by observational data on the mantle’s structure, dynamics, and evolution. To this end, geodynamicists are increasingly exploring adjoint-based approaches, which reformulate mantle convection modelling as an inverse problem. In this framework, unknown model parameters are optimized to fit available observational data.

Traditionally, inverse geodynamic models have primarily focused on observations that constrain either the initial (inverse sense) or final (forward modelling sense) state of the system, such as seismic tomography and geodesy. However, additional observational constraints are needed to rigorously reconstruct the mantle’s evolution over geological time. Surface plate velocities, their time-dependent behaviour, and plate boundary characteristics provide critical constraints. Another untapped dataset is the geochemistry of intra-plate volcanic lavas, which reflects the depth and temperature of mantle melting at the time of eruption. This geochemical signature provides insights into lithospheric thickness (the ‘lid’) and underlying thermal structure, extending our ability to constrain mantle evolution into the past.

Here, we present early efforts to incorporate mantle geochemistry into adjoint models of mantle convection using the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT -- https://gadopt.org/). Our synthetic experiments demonstrate that geochemical constraints on temperature and pressure enhance the accuracy of reconstructed mantle flow trajectories, unlocking insights into dynamic processes and interactions previously obscured in mantle retrodiction models. This integration offers the potential for a transformative leap in resolving mantle evolution, illuminating the interplay between deep Earth dynamics and surface processes that shape our planet’s geological history.

How to cite: Davies, R., Ghelichkhan, S., and Turner, R.: Enhancing Adjoint Reconstructions of Earth’s Mantle with Geochemical Data from Intra-Plate Lavas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8681, https://doi.org/10.5194/egusphere-egu25-8681, 2025.

One of the surface expressions of mantle convection is dynamic topography, as the the surface is uplifted above upwellings and pulled down above downwellings. However, it is challenging to extract the topography signal from the convecting mantle, because of large isostatic topography contributions from within the crust and subcrustal lithosphere. Technically, the latter can be included as part of dynamic topography but that needs to be clearly specified to avoid confusion. Here we use two recent crustal models to subtract crustal isostasy, and show that the remaining (residual) topography signal as well as the geoid can be matched well by a model where density anomalies and temperatures in the subcrustal mantle are inferred from seismic tomography. The model uses depth-dependent viscosity, and lateral variations due to temperature dependence below depth 219 km, and the distinction between (thicker) cratons, thinner lithosphere elsewhere and weak plate boundaries above that depth. We show that the fit can be improved if, in addition to densities inferred from tomography, a negative buoyancy between zero and about -40 kg/m^3 is added in continental lithosphere, in particular in cratons. The exact amount depends on model specifics, especially which crustal and tomography models are used. In our model, this buoyancy is added in the entire lithosphere, however, in reality, chemical buoyancy may be prevalent in certain depth regions. To address that issue we follow an approach similar to Wang et al. (Nature Geoscience, 16, 637–645, 2023) and plot the difference between dynamic topography from only sub-lithospheric density anomalies, and residual topography after only subtracting crustal isostatic topography against lithosphere thickness derived from tomography. The slope of this plot gives an indication of lithospheric density anomalies. For our best-fitting combination of dynamic and residual topography, we find a break in slope from nearly zero above 150 km to a negative slope below. This indicates that chemical density anomalies that cause lithospheric buoyancy are concentrated in the upper ~150 km.

How to cite: Steinberger, B. and Cui, R.: Modeling geoid and dynamic topography from tomography-based thermo-chemical density anomalies in the lithosphere and convecting mantle beneath  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8840, https://doi.org/10.5194/egusphere-egu25-8840, 2025.

Mantle slabs imaged by seismic tomography provide complementary subsurface information that could improve global plate reconstructions because they are indications of ancient tectonic plates. Linking mantle slabs to the surface plates requires approaches that follow geodynamic principles in a highly vigorous mantle. Here, we propose a new workflow that couples a slab unfolding approach and a mantle circulation model through which tomotectonic reconstructions can be performed, evaluated, and improved in a closed-loop experiment. We found that intra-oceanic subductions are crucial for understanding the evolution of the mantle and surface tectonics in the Pacific realm. Our closed-loop experiment allows us to reinterpret published tomotectonic reconstructions based on the vertical sinking slabs hypothesis. We conclude that highly vigorous mantle flow that allows lateral slab transport up to 4,000 km and non-constant sinking rates that deviate by up to 10 mm yr^-1 locally within a 1,000 km area must be accounted for in tomotectonic reconstructions.

How to cite: Chen, Y.-W., Wu, J., Bunge, H.-P., Stotz, I., Robl, G., and Schuberth, B. S. A.: Tomotectonic reconstructions validated via mantle circulation models in a closed-loop experiment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10156, https://doi.org/10.5194/egusphere-egu25-10156, 2025.

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 is a crucial parameter measuring the mass and heat mantle upwellings bring to the surface. However, the calculation of the global plume buoyancy fluxes is still in contention. Hotspot swells (topographically high regions with elevations of up to 2~3 km and widths of up to ~1500 km) are diagnostic surface expressions of mantle plumes.

Traditional approaches to calculate the swell buoyancy flux 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 move faster than the corresponding plate motion. Also, hotspot swells are partly dynamically compensated as plume material is injected into the upper mantle. With increasingly accurate observational constraints for dynamic seafloor topography, it is 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, plume radius, plate velocity and age, and mantle rheological parameters. From these results for plume spreading beneath moving plates, the buoyancy fluxes of individual plumes, as well as the relevant plume temperatures and radii are quantitatively constrained. We find that: (1) for a fixed plume radius, higher plume excess temperature results in higher but not necessarily wider swell; (2) plume buoyancy flux is linearly proportional to swell height × width²; (3) both faster plate velocities and older plates result in a lower swell height; (4) Lower upper mantle viscosity results in a wider but lower swell provided at a fixed plume buoyancy flux.

We demonstrate that previous swell-geometry-based estimates underscore the true buoyancy fluxes of the underlying plume upwelling. We update the plume-flux catalogue by building a scaling law for buoyancy flux as a function of swell geometry in order to estimate global heat and material fluxes carried by plumes.  

How to cite: Ma, Z., Ballmer, M., and Manjón-Cabeza Córdoba, A.: New Insights into Plume Buoyancy Fluxes and Dynamic Topography from Numerical Modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10765, https://doi.org/10.5194/egusphere-egu25-10765, 2025.

The Earth's palaeomagnetic record reveals the existence of a global magnetic field persisting for at least 3.4 billion years. This geomagnetic field is generated by thermochemical convection, driven by the cooling of the Earth's core. Efficient cooling of the core is crucial to sustaining the magnetic field. The solid mantle plays thus a critical role in regulating the core's long-term evolution. Notably, efficient mantle cooling resulting from plate tectonics is important for sustaining the magnetic field observed in the geological record up to the present day.

However, the timing of the onset of modern-style plate tectonics remains an open question. It may have been active since the Earth's formation (~4.5 billion years ago), or since the Archean (4 – 3 billion years ago), or emerged much more recently (<1 billion years ago). When and how plate tectonics began are major scientific questions in Earth science because of their profound implications for Earth's thermal and magnetic history. The convection regime that preceded plate tectonics remains unclear. Observations of other planetary bodies in the solar system such as Mars, Mercury, and the Moon suggest that a stagnant lid regime—characterized by a single and immobile plate—is the norm. This raises the possibility that early Earth operated under a stagnant lid regime, which is significantly less efficient at dissipating heat. Such inefficient cooling would limit the capacity to sustain a long-lived magnetic field, unlike the plate tectonics regime.

Our study aims to constrain the mantle-core co-evolution by investigating the impact of these two convection regimes—stagnant lid and plate tectonics (i.e. mobile lid)—and their transition during Earth's geological evolution. To achieve this, we developed a coupled model that integrates two one-dimensional evolution frameworks. One model describes the core's thermochemical evolution, including inner core crystallization and the potential formation of a thermally stratified layer. The other describes mantle dynamics, allowing for either stagnant lid or mobile lid behaviour.

We systematically explored a wide range of mantle parameters such as mantle viscosity, the relative efficiency of stagnant - versus mobile-lid regimes, the timing of plate tectonics onset, and the mantle's and core initial temperatures. For the core, we focused on two  end-member scenarios to account for the low and high thermal conductivity of iron whose precise determination remains controversial. We compared the resulting model predictions with key constraints, including the present-day inner core size, the palaeomagnetic record, the evolution of the mantle potential temperature, and the present-day thickness of a thermally stratified stable layer at the top of the liquid core. This integrated approach sheds light on the interplay between mantle dynamics and core processes since the time of Earth’s formation.

How to cite: Bonnet Gibet, V. and Tosi, N.: The effect of different mantle convection regimes on the long-term thermochemical evolution of the Earth’s core., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11498, https://doi.org/10.5194/egusphere-egu25-11498, 2025.

The planform is a defining feature of mantle convection and it can be gleaned from the stratigraphic record by mapping the continent-scale sediment distribution. Positive and negative surface deflections induced by mantle convection (dynamic topography) imprint the stratigraphic record at inter-regional scales. Dynamically uplifted continental regions create erosional/non-depositional environments which lead to gaps in the stratigraphic record, known as sedimentary hiatuses. Contrarily, subsided regions result in continuous sedimentation.
We use continental- and country-scale digital geological maps, regional geological maps, online geological databases, correlation charts, drill logs and regional stratigraphic studies, at a temporal resolution of geological series (ten to tens of millions of years) to map these events through geological time. This results in the hiatus maps---a proxy for the interregional patterns of uplift and subsidence associated with dynamic topography.
We carry this out for all continents apart from Antarctica for eight geological series since the Upper Jurassic and obtain a proxy for dynamic topography for each geological series. We study the temporal and spatial changes of the hiatus surfaces, their correlation with flood basalts eruptions, and the effects of sea-level variation in the resulting maps. Moreover, we also study the manual and digital approaches employed in the mapping of these hiatus surfaces.

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How to cite: Vilacís, B., Brown, H., Carena, S., Hayek, J. N., Stotz, I. L., Bunge, H.-P., and Friedrich, A. M.: Tracking dynamic topography through hiatus surfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11583, https://doi.org/10.5194/egusphere-egu25-11583, 2025.

The StruCtiv project, funded by and in collaboration with the Geological Survey of Bavaria (Bayerisches Landesamt für Umwelt, Hof), focuses on the structural geological characterization of active fault zones in the Frontal Bavarian Forest and explores their implications for large-scale cause-effect relationships of tectonic activity within the crystalline basement of the Bavarian Forest. Our findings provide new insights into the tectonic, petrological, structural, and geomorphological processes shaping the region while highlighting the need for further investigations to refine our understanding of these complex systems.  Preliminary U–Pb and K–Ar dating of minor faults exposed in granite quarries reveal a multiphase tectonic evolution spanning the Eocene to the Pleistocene, with possible indications of recent activity. U–Pb dating of calcite has proven especially promising, though additional sampling and structural characterization are required to address variability in ages within quarry outcrops. Complementary geomorphological analyses and cosmogenic nuclide measurements of river sediments show regional differences in erosion rates (21–40 m/Myr) and topographic variations, reflecting differential uplift rates. We used high-resolution TanDEM-X data and cosmogenic nuclide dating of older fluvial terraces to explore the long-term interactions between tectonics, climate, and erosion.  Deliverables from the first project phase include ten high-resolution 3D models of quarries in the Bavarian Forest, structural measurements, dating of fault surfaces, and geomorphological analyses. These results have identified episodic fault reactivation from the post-Variscan to late Cenozoic periods. Landscape analyses based on chi-index and knickpoint studies and cosmogenic nuclide dating provide a consistent picture of the region's landscape evolution. Together, these findings suggest differential tectonic uplift across the Bavarian Forest.  The ongoing project aims to build on these results through expanded structural and geochronological studies, the development of 3D models in additional quarries, and further digital mapping of structural inventories. The outcomes will deepen our understanding of fault-system evolution in continental intraplate settings and their role in understanding the long-wavelength vertical motion of the Earth's surface.

How to cite: Friedrich, A., Ludat, A., Zebari, M., Carena, S., Hildebrandt, D., Kahle, B., Assbichler, D., and Dusingizimana, M.: Structural Geological Characterization of Active Fault Zones in the Frontal Bavarian Forest and Implications for Large-Scale Cause-Effect Relationships of Tectonic Activity in the Bavarian Crystalline Basement (StruCtiv), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11593, https://doi.org/10.5194/egusphere-egu25-11593, 2025.

Many geophysical studies require knowledge on the present-day temperature distribution in Earth's mantle. One example are geodynamic inverse models, which utilize data assimilation techniques to reconstruct mantle flow back in time. The thermal state of the mantle can be estimated from seismic observations with the help of thermodynamic models of mantle mineralogy. However, the temperature estimates are significantly affected by inherent limitations in both the seismic and mineralogical information, even in the case of (assumed) known chemical composition.

Using a synthetic closed-loop experiment, we quantify the theoretical ability to determine the thermal state of the mantle from tomographic models. The 'true' temperature distribution is taken from a 3-D mantle circulation model with Earth-like convective vigour. We aim to recover this reference model after: 1) mineralogical mapping from the 'true' temperatures to seismic velocities, 2) application of a tomographic filter to mimic the effect of limited seismic resolution, and 3) mapping of the 'imaged' seismic velocities back to temperatures. We test and quantify the interplay of tomographically damped and blurred seismic heterogeneity in combination with different approximations for the mineralogical 'inverse' conversion from seismic velocities to temperature. Our results highlight that, given the current limitations of seismic tomography and the incomplete knowledge of mantle mineralogy, magnitudes and spatial scales of a temperature field obtained from global seismic models will deviate significantly from the true state, with average deviations up to 200 K in the deep mantle. Large systematic errors furthermore exist in the vicinity of phase transitions due to the associated mineralogical complexities.

The inferred present-day temperatures can be used to constrain buoyancy forces in time-dependent geodynamic simulations. Initial errors in the temperature field might then 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.

How to cite: Robl, G., Schuberth, B., Papanagnou, I., and Thomas, C.: From seismic models to mantle temperatures: Uncertainties and implications for geodynamic simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11599, https://doi.org/10.5194/egusphere-egu25-11599, 2025.

The flux of subducting slabs into the mantle is an essential component of the Earth’s mantle convection. However, the slab flux remains poorly known for pre-Jurassic times because of the absence of preserved oceanic seafloor. Sinking of subducted slabs within the mantle perturbs Earth’s moment of inertia, which, in addition to perturbations related to upwellings, results in long-term motion of the solid Earth relative to the rotation axis, resulting in so-called True Polar Wander (TPW). This motion, which can be inferred using paleomagnetic data, should therefore yield crucial information about the large-scale subduction kinematics back in time. However, it is not yet clear how to separate the numerous contributions to TPW, since these result from the superimposition of a complex distribution of mantle mass heterogeneities that are advected through time. In this study, we developed a new approach to assess the impact of subducting slabs on TPW based on the harmonic decomposition of plate kinematics into large-scale patterns. We constructed simple plate models that yielded pure dipole and pure quadrupole and net stretching kinematics, which represent the spherical harmonic degree 1 and degree 2 components of relative plate motions, respectively. We then implemented these three patterns of large-scale plate motions, and their subduction zones, into three simple mechanistic models and computed mantle mass heterogeneities through time. We then calculated changes to Earth’s moment of inertia tensor to predict the resulting TPW. In this contribution, we will first show the results of these sensitivity experiments highlighting the evolution of inertia perturbations associated to each of these three large-scale patterns. We will then show the calculated TPW using the harmonic decomposition of full-plate models over the last 250 Myrs and discuss the influence of each of these three plate kinematic components on the observed TPW. Finally, we will discuss how the observed TPW can help better constrain the evolution of mantle mass heterogeneities and rates of subduction flux for past times.

How to cite: Robert, B., Conrad, C. P., Steinberger, B., and Domeier, M. M.: Linking Plate Kinematics and True Polar Wander over the last 250 Myrs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11831, https://doi.org/10.5194/egusphere-egu25-11831, 2025.

Constraining the long-term evolution of geoid anomalies is essential for unraveling Earth's internal dynamics. While most studies focus on present-day geoid snapshots, we reconstruct the time-dependent evolution of Earth’s strongest geoid depression, the Antarctic Geoid Low (AGL), over the Cenozoic. Unlike geodetic reference frames that place the deepest geoid low in the Indian Ocean, a geodynamic perspective (relative to a hydrostatic ellipsoid) reveals the strongest nonhydrostatic geoid depression actually resides over Antarctica. Using a back-and-forth nudging technique for time-reversed mantle convection modeling, we leverage 3-D mantle density structures derived from seismic tomography and geodynamic constraints. Our results show that the AGL has persisted for at least ~70 Myr, undergoing a major transition in amplitude and position between 50 and 30 Ma. This coincides with abrupt lateral shifts in Earth’s rotation axis at ~50 Ma, validated through paleomagnetic constraints on True Polar Wander. Initially, stable lower mantle contributions dominated the AGL, but over the past ~40 Myr, increasing upper-mantle buoyancy, particularly above ~1300 km depth, amplified the AGL magnitude. This shift stems from the interplay between long-term deep subduction beneath the Antarctic Peninsula and a buoyant, thermally driven upwelling of hot, low-density material from the lowermost mantle. These new results contrast with earlier interpretations, clarifying the crucial role of evolving mantle buoyancy in shaping global geoid anomalies. By incorporating seismic, geodynamic, and mineral-physics data, our reconstructions provide a more comprehensive understanding of mantle flow beneath Antarctica and offer new insights into the dynamic coupling between lower and upper mantle processes that govern Earth’s long-wavelength geoid evolution.

How to cite: Glišović, P. and Forte, A.: The Cenozoic Evolution of Earth’s Strongest Geoid Low: Insights into Mantle Dynamics below Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12626, https://doi.org/10.5194/egusphere-egu25-12626, 2025.

One major objective in geodynamics is to create models of mantle flow that provide quantitative information to other Earth science disciplines. In this respect, geologically informed fluid dynamics simulations, such as mantle circulation models (MCMs) are a key component. In addition, thermodynamic models of mantle mineralogy are essential in that they can provide detailed information on material behaviour, such as density, thermal expansivity, elastic parameters and specific heat capacity, as a function of pressure and temperature for the geodynamic simulations. They are also required in the assessment of the MCMs to link temperatures to seismic velocities and density. This way, a number of secondary predictions, such as seismic, geodetic and geologic data, can be computed, which enables the validation of our models and the testing of geodynamic hypotheses by comparison to observations.

Here, we focus specifically on the dynamic effects and seismic imprint of the mantle transition zone (TZ). The complex set of phase transformations, together with an increase in viscosity, in this depth range is expected to influence vertical mass flow between upper and lower mantle. Still, neither the associated dynamic effects nor the seismic structure of the TZ have conclusively been constrained to date. Using our highly scalable new mantle convection software TerraNeo, based on the matrix-free finite-element framework HyTeG, we present a suite of MCMs with different formulations of compressibility. Classically, compressibility is included in the mantle convection simulations in form of the truncated anelastic liquid approximation (TALA), and the effects of phase transformations are either neglected or incorporated in parametrized form at constant depth. A physically more complete treatment of compressibility has recently been introduced in the form of the ‘Projected Density Approximation’ (PDA; Gassmöller et al., 2020). The PDA is based on tabulated material properties from the thermodynamic mineralogical models, thus allowing us to self-consistently capture non-linear buoyancy effects specifically due to phase transitions in the simulation. Comparing MCMs using TALA and PDA, we will highlight effects of mineral phase transitions on the evolution of mantle flow over time, the resulting present-day temperature field, as well as its seismic signature.

How to cite: Papanagnou, I., Schuberth, B. S. A., Robl, G., Freissler, R., Ilangovan, P., D'Ascoli, E., Vilacís, B., Brown, H., Schneider, A., Burkhart, A., Kohl, N., Chen, Y.-W., Stotz, I., Mohr, M., and Bunge, H.-P.: Dynamic and seismic expressions of mineral phase transitions in mantle circulation models computed with TerraNeo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12820, https://doi.org/10.5194/egusphere-egu25-12820, 2025.

Reconstructions of past mantle flow provide a powerful framework to sharpen our understanding of the dynamics and structure of the deep Earth. As a data-driven approach to geodynamic modelling, these reconstructions explicitly require an estimate of the present-day thermal state of the mantle, which can be derived from seismic tomography and an interpretation of observed mantle heterogeneity with mineral physics. Nonetheless, various uncertainties complicate the direct use of tomographic images. Critical issues are the spatially heterogeneous imaging quality, and the lack of definite metrics for seismic resolution and a practical quantification of model uncertainty. In many regions the patterns, but especially the amplitudes of velocity variations, are thus insufficiently constrained, making global tomography prone to drawing a dynamically inconsistent picture of the mantle’s buoyancy field. For geodynamic inferences, it is therefore vital to establish to what degree these current limitations affect our capacity to accurately reconstruct the mantle’s evolution back in time, and, where necessary, what strategies can be advised to address their impact.

We introduce a tomographic-geodynamic framework designed to tackle this issue with the aid of closed-loop experiments. Based on a reference mantle circulation model (MCM), we set up a complete, synthetic tomographic experiment with the following key components: 1) S-wave finite-frequency traveltime residuals are obtained from seismograms predicted for the MCM, recorded at ~10,000 real station locations. Therefore, we use the global wave propagation code SPECFEM3D_GLOBE to simulate in total 3,800 teleseismic earthquakes accurate down to a shortest period of ~10s. 2) We sample the complete dataset on the basis of ray turning point locations to obtain an optimal and balanced illumination of the entire mantle. 3) We perform tomographic inversions with the SOLA method and paraxial finite-frequency kernels. The explicit computation of the inverse and the corresponding resolving kernels in SOLA allow us to create tomographically filtered representations of the `true` MCM heterogeneity. Furthermore, it gives us the possibility to analyze them together with associated local resolution and uncertainty estimates. The resulting synthetic tomographic images are generally able to reproduce the patterns of major anomalies from the MCM. Yet, the amplitudes and exact shapes remain difficult to recover, even in the case of optimized data coverage and tuning of inversion parameters towards highly localized and narrow resolving kernels. This work serves as the basis for subsequent testing of the tomographic input within adjoint mantle flow reconstructions to complete the closed-loop setup.

How to cite: Freissler, R., Schuberth, B. S. A., Zaroli, C., and Bunge, H.-P.: A tomographic testbed for geodynamic reconstructions of past mantle flow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12871, https://doi.org/10.5194/egusphere-egu25-12871, 2025.

Mantle convection drives large-scale vertical motion at the surface (dynamic topography), which is linked to present-day geoid undulations and residual topography. However, this link depends crucially on the mantle viscosity profile, which remains one of the largest uncertainties in global geodynamics. While instantaneous flow models based on seismic tomography have provided classic constraints on mantle viscosity structure, here the profile acts only to map a given density structure to surface observations. This means the viscosity profile is not necessarily consistent with the density structure. Here we tackle this problem using a suite of high-resolution time-dependent mantle circulation models which assimilate plate velocities over the past 400 Myrs. This allows us to study the role of the mantle viscosity profile in altering the density structure of the mantle through the planform of convection, in tandem to its role in mapping this to the surface through kernels. We find that the changes in the spherical harmonic density spectrum of the mantle, which result from a given change in the profile, can alter surface observations with the same magnitude as the changes to the kernel. The coupled influence of the profile on the mantle density spectrum and kernels, together with observed geoid undulations and residual topography, provides a new method of constraining the mantle viscosity profile using time-dependent convection modelling. 

How to cite: Brown, H., Stotz, I. L., and Bunge, H.-P.: Probing the influence of the mantle viscosity profile on the density spectrum and its effect on present-day surface observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12880, https://doi.org/10.5194/egusphere-egu25-12880, 2025.

Ferropericlase (Mg,Fe)O, is the second most abundant mineral in the Earth’s lower mantle, and it’s structural and electronic properties are critical for understanding the formation processes and evolutionary history of the Earth's core.

This study focuses on the behavior of ferropericlase under extreme conditions that simulate the environment near the core-mantle boundary (CMB) and within the outer core, at pressures around 130 GPa and temperatures of about 3500 K related to a depth of approximately 2800 km by using shock compression experiments. It is well-documented that FeO exhibits varying structural configurations under high pressure and temperature [1] and iron electron spin changes [2]. This study aims at deepening understanding of ferropericlase's role in geophysical processes occurring at extreme conditions within Earth’s interior, ultimately contributing valuable insights into core formation theories and mantle dynamics. To investigate these properties, we synthesized ferropericlase (Fe_0.14Mg_0.86O) samples resembling pyrolytic mantle composition suitable for dynamic compression experiments. The experiments were conducted at the High Energy Density Scientific instrument at European XFEL within the scope of the DiPOLE community proposal 6656, utilizing time-resolved diagnostics to capture changes in the material's structure and electronic state. Two X-rays pulses were synchronized with a target impact, one before and another after the drive laser pulse of the DiPOLE 100-X laser, which allow us to probe the sample in a cold state and under pressure and temperature. The setup enabled us to acquire multiple datasets, including Velocity Interferometry for Any Reflector (VISAR) images, X-ray emission spectroscopy (XES), and X-ray diffraction (XRD). Data processing involved several steps: XES, spectra of Fe Kβ_1,3 lines were analyzed for both pulses separately ensuring accurate timing of X-ray arrivals. XRD data underwent flat fielding correction followed by summation of diffraction patterns to calculate unit cell parameters for ferropericlase.

The XES data reveal a clear transition from high-spin to low-spin states as a function of laser energy and delay relative to the ambient conditions. Concurrently, XRD analysis shows a notable shift to larger momentum transfer in the main Bragg peak compared to cold runs, allowing for precise calculation of unit cell dimensions under varying pressure conditions. By integrating our initial findings with established equations of state (EoS) [3] we can estimate the pressure conditions at each experimental shot, indicating the variation of pressures up to ~130 GPa, i.e. conditions at the CMB. This analysis facilitates the construction of a volume-pressure curve that elucidates spin transitions relevant to Earth's depths. Next step consists in analyze VISAR data and get the Hugoniot for this composition. Furthermore, we aim to understand the electronic structure of the melts.

[1] Ozawa et al.  Spin crossover, structural change, and metallization in NiAs-type FeO at high pressure. Phys. Rev. B 84, 134417 (2011)

[2] Greenberg et al. Phase transitions and spin state of iron in FeO under the conditions of Earth's deep interior. Phys. Rev. B 107, L241103 (2023)

[3] Fei et al. Spin transition and equations of state of (Mg, Fe)O solid solutions. Geophys. Res. Lett., 34, L17307 (2007)

How to cite: Camarda, C., Appel, K., Buakor, K., Amouretti, A., Crepisson, C., Harmand, M., Pennacchioni, L., Sieber, M., and Sternemann, C.: Characterization of ferropericlase under extreme condition using shock wave experiments carried at European XFEL utilizing DiPOLE 100-X drive laser, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13580, https://doi.org/10.5194/egusphere-egu25-13580, 2025.

Mantle convection is the principal driver of Earth's long-wavelength surface structure, manifesting as dynamic topography—surface undulations induced by convective currents within the mantle. Unveiling the temporal evolution of dynamic topography remains a central challenge in predictive geodynamics. Adjoint methods have recently gained prominence for reconstructing mantle convection history and correlating it with key geological phenomena, including the cessation of marine inundation in North America, the uplift of Africa, and the tilting of Australia.

In this study, we introduce a new generation of retrodiction models developed using the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT). These models incorporate Earth-like rheological parameters and leverage state-of-the-art Global Full‐Waveform seismic tomography to achieve unparalleled resolution of mantle structures. The models are refined through integration with the latest plate reconstruction models, yielding regularised solutions that reconcile tectonic and seismic observations.

For the first time, we unveil the evolution of dynamic topography during the late Cenozoic, as derived from these advanced models. These results provide novel insights into the interplay between mantle convection and surface processes, refining constraints on dynamic topography and illuminating the forces that have governed Earth’s geological evolution.

How to cite: Ghelichkhan, S., Davies, D. R., Gibson, A., and Roberts, D.: Unveiling Late Cenozoic Dynamic Topography Evolution Using Non-Linear Adjoint Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13762, https://doi.org/10.5194/egusphere-egu25-13762, 2025.

Complex interactions between plate subduction, mantle flow, and the overriding plate govern the dynamics of subduction zones. Numerous studies have highlighted the critical role of subduction processes in redistributing thermo-chemical domains within the mantle, significantly influencing mantle dynamics and plate tectonics. However, debates persist regarding the thermal conditions and dynamic models of the mantle affected by stagnant slabs. The physical state and long-term dynamics of the mantle surrounding stagnant slabs in the mantle transition zone (MTZ) remain poorly understood, partly due to the lack of detailed reconstructions of subduction history and robust constraints on mantle temperatures. 

The northwestern Pacific region, with its extensive subduction history spanning over 40 million years and involving multiple oceanic plates with episodic plate boundary modifications, provides an ideal setting for studying subducting slab structures and their associated tectonic and dynamic processes. High-resolution seismic tomography of the MTZ beneath the coastal margins of northeast Asia has revealed a narrow channel of low-velocity anomalies surrounded by high-velocity regions, indicating the presence of segmented western Pacific stagnant slabs. The geometric features of these imaged structures likely reflect rapid plate boundary reorganization during the Cenozoic in the western Pacific, driven by continuous lateral extension and tearing of the retreating Pacific slab. This process has led to the formation of a laterally extended MTZ gap characterized by moderate mantle temperatures (Tp ~1350–1450°C), as determined through joint analyses of seismic velocities and mantle phase transition thicknesses.

We propose that the current MTZ gap in the western Pacific exhibits minimal thermal anomalies capable of inducing focused mantle upwellings. Our observations suggest that mantle dynamics around the stagnant slabs would be largely passive, unless thermochemical sources capable of driving active convection are present. This further implies that active mantle upwellings, if they existed, were spatially and temporally constrained during past slab segmentation processes.

How to cite: Song, J.-H., Rhie, J., Kim, S., and Tauzin, B.: Cold Mantle Transition Zone Gap Formed by Progressive Tearing of the Segmented Western Pacific Slab, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14576, https://doi.org/10.5194/egusphere-egu25-14576, 2025.

As a consequence of the evolution of the water-bearing basal magma ocean, water-induced mantle overturn can well account for many puzzling observations in the early Earth, such as the formation of the Archean continents and the boundary of the Archean and Proterozoic. The upwelling of the hot basal magma ocean during the mantle overturn also significantly affects the thermal state of the core-mantle boundary and the geomagnetic field. This study models the thermal evolution of the core-mantle boundary to investigate the effects of mantle overturn on the geomagnetic field. Our results demonstrate that mantle overturn substantially accelerates the cooling of the core and increases the heat flow across the core-mantle boundary. This enhanced heat flow strengthens the geomagnetic field, which well explains the high virtual dipole moments at ~3.5-2.5 Ga. The palaeomagnetic records and the formation of the Archean continents generate a concordant picture on the evolution of the water-induced mantle overturn. Additionally, the Earth's mass redistribution driven by the mantle overturn provides a novel mechanism for triggering true polar wander in the Archean. Therefore, the recorded apparent polar wander at 3.34-3.18 Ga may not result from plate tectonics.

How to cite: Wang, D. and Wu, Z.: Water-Induced Mantle Overturn Provides a Unifying Explanation for Palaeomagnetic Records and Formation of Archean Continents, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14806, https://doi.org/10.5194/egusphere-egu25-14806, 2025.

This study introduces a time-domain methodology for analyzing the response of solid Earth tides, focusing on their phase delay relative to maximum vertical gravitational attraction. Unlike traditional frequency-domain approaches, which primarily decompose tidal signals into harmonic components, the proposed method emphasizes temporal dynamics, offering higher resolution and fewer assumptions about signal periodicity.  

Solid Earth tides, driven by gravitational forces from the Moon and Sun, induce periodic deformations of the Earth's surface, known as tidal bulges. These bulges are expected to coincide with maximum gravitational attraction, but a measurable phase delay often occurs due to the Earth's internal rheological and viscoelastic properties. Understanding this delay is crucial for deciphering the complex interplay between tidal forces and tectonic processes, including stress evolution, crustal deformation, and even earthquake triggering mechanisms.  

To achieve this, the study analyzed high-precision gravity data from 14 permanent gravity stations in Europe, alongside GNSS-derived measurements of vertical surface displacement. Corrections were applied to isolate the gravitational effects of solid Earth tides, accounting for factors such as atmospheric pressure variations, ocean tidal loading, and direct gravitational attraction. The residual gravity signal, reflecting the solid Earth tidal bulge, was then examined for phase delay using time-domain algorithms.  

Key findings revealed significant variability in the phase delay across geographic and tectonic settings, suggesting localized geological factors influence the Earth’s response to tidal forcing. This delay, although small, was found to redistribute stresses within the crust and mantle, potentially affecting fault reactivation and long-term tectonic plate dynamics. The integration of GNSS data allowed a comprehensive view of vertical deformation, further validating the gravity-based findings.  

This time-domain approach provides a complementary perspective to frequency-domain analyses, capturing nonlinear and time-dependent effects often overlooked in traditional studies. By enhancing our understanding of tidal lag phenomena, the research contributes to refining models of lithospheric and asthenospheric dynamics. The methodology holds promise for broader applications in geophysical monitoring, offering insights into stress and strain evolution in tectonically active regions.  

These advancements pave the way for improved interpretations of solid Earth processes and their implications for natural hazards, resource management, and planetary dynamics. This study underscores the potential of integrating gravity and GNSS data for high-resolution analyses of Earth’s dynamic behavior.

How to cite: Capponi, M., Sampietro, D., and Greco, F.: Time-Domain Analysis of Solid Earth Tides: A Pathway to Understanding Tectonic Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16300, https://doi.org/10.5194/egusphere-egu25-16300, 2025.

Viscosity and thickness of Earth’s asthenosphere are typically inferred from observations of postglacial rebound of the lithosphere. Parameter values deduced from studies of these observations serve a wide range of geodynamic models that simulate processes evolving over time periods of hundred Myr - much longer than the duration of the rebound process itself. The question remains whether inferences derived from the kyr-long rebound process hold over Myr-long periods. The record of past motions of non-subducting plates may help address such a question, because these motions are necessarily driven by asthenospheric Poiseuille-type flow, which is sensitive to viscosity and thickness of the asthenosphere. Here I show how a simple model for the dynamics of non-subducting plates may be used to address the question whether parameter values derived from the kyr-long rebound hold over the longer time-scales of plate motions. By interrogating the reconstructed records of past motions of three non-subducting plates, I find that indeed this is the case. Furthermore, including also constraints on the asthenosphere thickness from seismic tomography narrows down the range of plausible values of asthenosphere viscosity to [1, 3]*10^19 Pa*s.

How to cite: Iaffaldano, G.: Viscosity and thickness of Earth’s asthenosphere: inferred from Kyr-long processes, applicable to Myr-long dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16470, https://doi.org/10.5194/egusphere-egu25-16470, 2025.

How to cite: Kahle, B., Kübler, S., Purohit, C., Junginger, A., Sloan, A., Friedrich, A., Rieger, S., and Zebari, M.: Fault evolution in the Kenya Dome: an area of highly elevated topography within the East African Rift System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16517, https://doi.org/10.5194/egusphere-egu25-16517, 2025.

Recent studies suggest that the secular variation dynamics of the geomagnetic field exhibits periodic patterns that indicate underlying wave processes in the Earth’s core. However, as long as the analytical core field models are based on geographically sparse and noisy observatory data, they have apparent limitations for studying fine structure of its spatiotemporal variations. The advent of satellite measurements of the full geomagnetic field vector in 1999 removed this limitation and made it possible to produce reliable and highly accurate models of the secular variation, allowing downward continuation to the core-mantle boundary. These models have revealed rapid core field variations on a time scale of the order of 10 years. In particular, the 6-year quasi-periodicity in the second time core feld derivative has been established. In our recent research, we expand our previously successful efforts to extract the secular variation and secular acceleration signal from the magnetic observatory data over 90-year period (1932-2022), i.e. far before the advent of the space era. As a result, our approach to data analysis for the first time has made it possible to confirm the existence of a 3-year quasi-periodicity of secular acceleration pulses of alternating polarity over the mentioned period. The proposed methodology does not imply an intermediate production of a core field model, as done according to classical approaches.

How to cite: Sidorov, R., Soloviev, A., and Bogoutdinov, S.: A 6-year quasi-periodicity in the Earth's core magnetic field dynamics from 1932 to 2022, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16588, https://doi.org/10.5194/egusphere-egu25-16588, 2025.

The alternation between superchrons and periods of rapid field reversals is comparable
to timescales of mantle convection, suggesting that lowermost mantle evolution impacts
the reversal frequency of the Earth’s magnetic field. By controlling the heat flow from
the outer core, the deep mantle temperature distribution can either support or hamper
the convective pattern in the outer core that generates the dipolar field component.

Due to the long timescales, the main means of testing a potential correlation between
reversal frequency rate and CMB heat flow distribution is through tectonically informed
geodynamic modelling. However, even though state-of-the-art mantle circulation models (MCMs) 
typically explain statistical properties of seismological data, they do not consistently 
reproduce the location of present-day mantle features. The main influence
on position is given by the assimilated absolute plate motion model, which is inherently
restricted by the lack of longitudinal constraints as well as the need to separate plate
motion and true polar wander signal in paleo-magnetic data. Geodynamic model predictions 
therefore need to be compared to independent observations.

In this contribution, we investigate predictions of present-day mantle structure that
are based on differences in the absolute plate motion model. We compute synthetic seismic
data by coupling MCM predicted structure with a thermodynamic mineralogical model.
The analysis is predominantly focused on normal mode data, as they capture the longwavelength 
component of structures throughout the entire mantle. In addition, the
global sensitivity of normal modes reduces the drawbacks of uneven data coverage. By
quantifying the fit to seismic data, we evaluate different realisations of mantle structure
that reflect plausible variations in the absolute plate motion history.

How to cite: Schneider, A., Schuberth, B., Koelemeijer, P., Shephard, G., Myhill, A., and Al-Attar, D.: Investigating deep mantle evolution by linking geodynamic modelling to seismic data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16609, https://doi.org/10.5194/egusphere-egu25-16609, 2025.

The Earth's lithosphere undergoes vertical motion on a range of spatial and temporal scales. In recent years it has become increasing clear that mantle related forcing and in particular mantle plumes are a significant contributor to uplift events in many regions of the world, making vertical motions a powerful probe into sublithospheric processes. Significant improvements of observational methods (e.g. satellite missions) and publicly-accessible databases (e.g. digital geological maps) make it now feasible to map vertical motions from geodetic to geologic time scales. This in turn provides invaluable constraints to inform key, yet uncertain, parameters (e.g. rheology) of geodynamic models. Here we report results of an ongoing Research Training Group (RTG) 2698, with 10 individual dissertation projects and a Post-doc project, funded by the German Research Foundation. The RTG follows an interdisciplinary approach of Geodynamics, Geodesy and Geology aiming to answer questions related to how the interaction of exo- and endogenic forcing shapes a diverse array of earth processes. From a combined interpretation of interdisciplinary observations with different spatial and temporal sensitivity, together with physical models, work in the RTG tries to disentangle different uplift mechanisms, including the plume, plate and isostatic mode, based on their specific spatial and temporal patterns. We will give an overview of key results and highlight the synergies that derive from bringing multiple constraints to bear on vertical motion processes of the lithosphere.

How to cite: Bunge, H.-P., Friedrich, A., Pail, R., and Chen, Y.-W.: Geophysical modelling of vertical motion processes constrained by geodetic and geological observations (UPLIFT), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17175, https://doi.org/10.5194/egusphere-egu25-17175, 2025.

The anomalous seismic structure of the upper mantle at the Hawaiian hotspot, including the X-discontinuity at 310 km depth and a perturbed 410, has been ascribed to large quantities (>40%) of recycled eclogite in the Hawaiian mantle plume. These estimates far exceed the classical geodynamic constraints of 15-20%, suggesting the existence of additional mechanisms driving eclogite accumulations. 

We tackle this discrepancy by superimposing discrete heterogeneities of recycled eclogite to a plume featuring a realistic mechanical mixture composition. This approach allows us to entrain higher amounts of denser material and quantify its segregation in the 310-410 km depth range. To reproduce the ample spectrum of buoyancy fluxes reported for the Hawaiian hotspot, we test plume radii of 80-100 km, excess plume temperatures of 200-300 K, and recycled heterogeneity fractions between 5 and 20%.

Our 8 best-fit cases yield average eclogite accumulations of 19.5% at 310 km and 21-25% at 410 km, with peaks of 21-24% and 26-32%, respectively. This uniformity indicates that higher eclogite entrainments do not substantially increase material segregation in the mid-upper mantle. 

We demonstrate that, while the Hawaiian plume has the potential of recycling more than 18% denser material, high segregations are unsustainable over geological timescales, and excess entrainments above 20% would require unrealistic buoyancy fluxes. Our findings provide the first quantitative constraint of the dynamic relationship between the Hawaiian mantle plume and the X-discontinuity, critically advancing our understanding of the influence of recycled eclogite on mantle discontinuities.

How to cite: Monaco, M., Russo, R., and Brown, H.: The thermochemical Hawaiian plume and its dynamic influence on upper mantle discontinuities , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18199, https://doi.org/10.5194/egusphere-egu25-18199, 2025.

Through almost the entire mantle column, oceanic crust is denser than ambient mantle. In a ca. 100 kilometers thick channel below the lower-upper-mantle boundary, however, this relation is reversed. Hence, this channel constitutes a trap for oceanic crust and several recent studies have indeed proposed large ponds of crust at this depth. Accumulation of crust would be expected to be continuous, while sequestration into the lower mantle should be episodic due to the metastable nature of the gravitational trap. Non-steady-state concentration of crust in the channel would be associated with variations in Earths volume in the order of several millions of cubic kilometers. While transfer of crust from the upper mantle into the channel causes volume increase, the collapse of crust into the lower mantle would be associated with net volume decrease. We propose that collapse events could be associated with rising mantle plumes, hence, a net volume decrease of Earth would precede the eruption of large igneous provinces (LIP). A dramatic volume loss in 650 kilometers depth might be able to pull down the surface for a brief time. Such an event might be expressed in an outstanding sea-level-drop before the eruption of LIP. This hypothesis is confirmed by a review of eustatic sea-level changes accompanying late Paleozoic – Cenozoic LIPs activity showing that a majority of LIP emplacement are shortly (< 500 kyr) preceded by an episode of up to 50 meters (average of 25 meters) eustatic sea-level fall, with return to pre-perturbation levels at the onset of LIP eruption.

How to cite: Nagel, T. and Bodin, S.: Variations of Earth's volume driven by intermittend mantle stratification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18671, https://doi.org/10.5194/egusphere-egu25-18671, 2025.

Over the past decade, advances in data assimilation techniques combined with a rapid increase in computational power have allowed for increasingly realistic dynamo simulations. One of the key parameters controlling the dynamics of the magnetic field is the amount of heat loss through the core-mantle boundary (CMB), highlighting the crucial role of the lower mantle in the dynamo processes. Previous studies (Kutzner and Christensen, 2004) suggest that heat flux variations at the lower mantle may explain the observed changes in reversal frequency on time scales of some 10 million years. 

To study the effect of the mantle on reversals, we use the numerical code MagIC, simulating the dynamo process over geological timescales. The long required simulation time forces us to use a relatively large Ekman number of E = 3 · 10^-4. Following Frasson et al. (2024), we first explore the impact of several fundamental heat-flux patterns (spherical harmonic degree Y₁₀, Y₂₀, Y₂₂, ...) and amplitudes imposed at the outer boundary. Secondly, we use a codensity approach to explore whether a higher degree of compositional driving reduces the impact of the core-mantle boundary heat flux pattern. Finally, we investigate the impact of the stably stratified layer at the top of the outer core (Buffett et al., 2016) on the geodynamo process and the stability of the magnetic field.

How to cite: Lohay, I. and Wicht, J.: Utilizing Codensity Approach to Assess How Core-Mantle Boundary Properties Influence Geomagnetic Reversal Frequency, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19113, https://doi.org/10.5194/egusphere-egu25-19113, 2025.

Postseismic deformation in the far field following large earthquakes is increasingly recognised as a key factor contributing to regional land height and relative sea-level (RSL) changes. The Sumatran subduction zone provides a unique setting to study this deformation owing to the availability of far-field (600 – 1000 km from the trench) and long-term (>20 years) Global Navigation Satellite System (GNSS) observations. In this study, we model the GNSS-constrained postseismic deformation of multiple great (M_w ≥ 8.0) regional earthquakes using a layered and self-gravitating spherical Earth model. Our results reveal a weak asthenosphere beneath the continental lithosphere in explaining the far-field GNSS observations. We estimated an asthenosphere Maxwell viscosity as low as 𝜂_m = 1.5 – 3e18 Pa s. Even assuming the presence of a weaker lithosphere-asthenosphere boundary layer (𝜂_m = 1.3 – 2.8e17 Pa s) of 5-10 km thickness, the asthenospheric Maxwell viscosity remains less than 1e19 Pa s. Using these mantle viscosities, we estimated horizontal and vertical postseismic viscoelastic surface deformation over a broader region beyond where GNSS observations are available. We show that a weak backarc asthenosphere leads to relatively large, fast, and extensive postseismic deformation, a conclusion that likely applies to many other subduction zones. The great Sumatran megathrust earthquakes, namely the 2004 Sumatra-Andaman, 2005 Nias-Simeulue, and 2007 Bengkulu events, caused continuous far-field postseismic land subsidence over two decades. The 2012 M_w 8.6 and M_w 8.2 Wharton Basin strike-slip earthquake sequences in the Indian Ocean produced postseismic uplift in the far field, slowing down but not offsetting the ongoing subsidence caused by the great megathrust earthquakes. Our results highlight a critical concern for Southeast Asia’s coastal population, as the regional VLM and RSL rise due to large earthquakes compounds the impacts of climate-driven sea-level changes.

How to cite: Ng, G., Feng, L., Zhou, X., Luo, H., Wang, K., Sun, T., Yong, C. Z., and Hill, E. M.: Geodetic Evidence for Weak Mantle Beneath the Sumatran Backarc and Its Influence on Regional Sea-Level, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19600, https://doi.org/10.5194/egusphere-egu25-19600, 2025.

The Afar Depression, a key tectonic and volcanic region in East Africa, is characterized by complex interactions between rifting processes and mantle dynamics, particularly the influence of the rising Afar plume. This study offers a detailed investigation of uplift patterns in the Afar Depression over a decade (from 2014 to 2024) using Interferometric Synthetic Aperture Radar (InSAR) time-series analysis. The objective of this study is to generate critical insights and key observations as a foundational resource for advancing and refining future geological research. Resolving subtle, spatially distributed uplift patterns linked to tectonic activity has historically been challenged by methodological limitations. To address this, we analyzed three ascending (14, 87, 116) and four descending (6, 35, 79, 108) Sentinel-1A paths, applying the Small Baseline Subset (SBAS) method, complemented by decomposition techniques to achieve precise deformation measurements. We categorized the Afar area according to regions with the highest uplift rates, aiming to identify zones exhibiting significant tectonic activity. Our analysis reveals significant spatial and temporal variations in uplift rates, providing new insights into the region’s tectonic complexity and the role of the Afar plume. These findings highlight the intricate interplay between plume-driven uplift and tectonic structures, advancing our understanding of the Afar Depression’s geological evolution and the broader dynamics of continental rifting and lithospheric deformation.

How to cite: Milczarek, W. and Namdarsehat, P.: Investigating Uplift in the Afar Depression: Tectonic Complexity and Afar Plume through InSAR Time Series (2014–2024), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19803, https://doi.org/10.5194/egusphere-egu25-19803, 2025.

The development of the Dead Sea Transform (DST) coincided with a vertical uplift of the transform margins, forming the main N-S mountain ridge of Israel, as well as a subsidence of Dead Sea pull-apart basin. So far only minor parts of these events have been accurately dated.  Karst processes that started after marine regression, led to the formation of karst aquifers in the carbonate lithologies of Cenomanian to Eocene age. The vertical tectonics (mountain uplift and Dead Sea Valley subsidence) caused the caves to be gradually uplifted above the regional groundwater level. In the current study, we used Laser Ablation (LA) U-Pb chronology of phreatic and vadose cave calcite to determine the timing of vertical tectonic stages: the marine regression, onset of karst processes, and transition of the caves from the groundwater up to the vadose zone. U-Th chronology was used for dating the youngest calcites. Phreatic and vadose calcite samples were collected from sites with similar altitudes and a spatial extent of ~150 kilometers on N-S transect along the western DST margin. In-situ LA U-Pb chronology of calcite,  along with calcite 18O values ranging between -16‰ and -9‰ (VPDB), fluid inclusion (FI) 18O-D analyses and associated d-excess values of 9‰ to 29‰ (VSMOW) indicates that meteoric waters infiltrated into the aquifer since Late Eocene – Early Oligocene (35.1±0.3 Ma to 29.17±0.4 Ma), marking the timing of sea regression and onset of meteoric water infiltration into the aquifer. The onset of vertical tectonics in the region during the early Miocene, caused an initial uplift of the caves above water table and deposition of first vadose speleothems around 20 Ma. The average uplift rate of the western margin of DST was approximately 26 m per million years, which increased to 120 m per million years from 6 Ma to the present. This change appears to correspond with a few degrees shift in previously parallel sinistral strike slip movement of the Dead Sea Transform, introducing an extensional component and leading to the development of the pull apart basin.

How to cite: Langford, B., Vaks, A., Golan, T., Levy, E., Zilberman, T., Yasur, G., Weiss-Sarusi, K., and Frumkin, A.: Morphotectonic Chronology of the Dead Sea Rift's Western Margin: Insights from U-Pb Dating of Speleothems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19898, https://doi.org/10.5194/egusphere-egu25-19898, 2025.

The South Atlantic Anomaly (SAA) represents the region of Earth’s weakest magnetic field intensity, where the inner radiation belt approaches closer to the planet’s surface. This anomaly is a critical region for understanding radiation belt dynamics and their responses to solar activity-induced magnetospheric changes.

This study is based on our recent numerical simulations of the inner proton radiation belt [Girgis et al., JSWSC (2021), SW (2024)], extending the model to include electron dynamics in the inner magnetosphere. The simulations adopted the IGRF and Tsyganenko models to provide a time-dependent magnetic field driven by solar input conditions detected by ACE mission, including the associated inductive electric field. A key feature of this research is the incorporation of wave-particle interactions, identified through Pc4-Pc5 wave detections using the MAGDAS ground magnetometer network. The primary objective is to simulate the enhancement of electron flux in the northern SAA region due to wave-particle interactions.

Understanding particle dynamics within the SAA is essential for predicting the radiation environment in low Earth orbit (LEO) missions, forecasting ionospheric responses to severe space weather, and assessing potential long-term impacts on Earth's climate system.

How to cite: Girgis, K., Hada, T., Yoshikawa, A., and Matsukiyo, S.: Multi-Scale Observation-based Simulation Model for Investigating the Wave-Particle Interactions in the South Atlantic Magnetic Anomaly: Preliminary Results, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-554, https://doi.org/10.5194/egusphere-egu25-554, 2025.

This study presents new paleomagnetic results from La Barrancosa Lake (37°19’ S, 60°06’ W), located in the Argentinian Pampean region. The region's sparse paleomagnetic studies and its location under the South Atlantic Anomaly (SAA) make it a key area to investigate past geomagnetic field behavior. A 1-meter-long sediment core (covering approximately the last 2500 years), the longest paleomagnetic record recovered from the lake to date, was collected and analyzed. This work aims to improve the understanding of paleosecular variations (PSV) and the geomagnetic field's non-dipole behavior in the Southern Hemisphere.

The magnetic susceptibility (k) profile was used to correlate this core with previous records from La Barrancosa. Standard paleomagnetic measurements were performed, including natural remanent magnetization (NRM) intensity and directions (declination D and inclination I). Stepwise alternating field (AF) demagnetization revealed a stable single-component NRM after removing a low-coercivity viscous component. Characteristic remanent magnetization (ChRM) directions were determined using principal component analysis. Additional rock magnetic experiments, such as anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) until saturation (SIRM), thermomagnetic curves, hysteresis loops and First Order Reversal Curve (FORC) analysis provided insights into the concentration, coercivity and grain size of magnetic minerals. The measurements were carried out at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.

Preliminary results demonstrate well-preserved paleomagnetic signals with inclinations ranging from -64° to -17°. MAD values lower than 5° in the samples indicate reliable ChRM directions. These data will be compared with global geomagnetic models to address potential discrepancies and explore the contributions of non-dipole features in the region, likely associated with the influence of the South Atlantic Anomaly (SAA).

The new paleomagnetic record from La Barrancosa Lake enhances the temporal resolution of paleomagnetic studies in the Pampean region and provides critical data to investigate geomagnetic field variations in the Southern Hemisphere. The results underscore the region’s potential for refining global and regional geomagnetic models and highlight the importance of further research to explore the implications of these deviations for understanding the evolution of the SAA.

How to cite: Achaga, R., Gogorza, C., Iruruzun, M. A., Orgeira, M. J., Spagnuolo, L., Sagnotti, L., and Winkler, A.: Paleomagnetic results from La Barrancosa Lake, Argentina, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-714, https://doi.org/10.5194/egusphere-egu25-714, 2025.

The tectonic evolution of the Aegean Region can be divided into two main geological phases in the Cenozoic era. The first phase began at the end of the Mesozoic and is characterized by a compressional regime resulting from the closure of the Tethys Ocean and the formation of the Alpine system. This period was dominated by subduction tectonics, which shaped the geological evolution of the region. During this time, the formation of rift valleys, which are the most prominent structural elements of the Aegean today, was triggered. These rift valleys, typically bounded by faults on both sides, developed asymmetrically. They are the most dominant geological and morphological feature of Western Anatolia. The rift valleys, which are mostly bounded by normal faults, are seismically active. These rift valleys can be listed from north to south as follows: Edremit Gulf, Bakırçay-Simav Rift, Gediz-Küçük Menderes Rift, Büyük Menderes, and Gökova Rift. The second phase is characterized by a regional North-South extensional period. During this time, the fault systems in the region became more pronounced under the influence of extension. This extensional regime is related to changes in the stress environment within the lithosphere.

The Menderes Massif, with its unique geological structure and evolution, is another important feature of the region. It is particularly notable for being cut by numerous late-stage rifts, resulting in a dynamic structural evolution. The majority of the massif contains high to medium enthalpy geothermal reservoirs, with temperatures ranging from 120°C to 240°C. These reservoirs generally lie within metamorphic rocks and are located in lithologically diverse units. This study will focus on magnetism studies of geothermal wells in Western Anatolia, with samples taken from different depths and temperatures. The aim is to investigate the magnetic characteristics of the geothermal wells under pressure and temperature conditions. The methods applied will include the following: Magnetic susceptibility study (frequency-dependent susceptibility), Thermal magnetic susceptibility study, Hysteresis measurement, Isothermal remanent magnetization (IRM), Saturation isothermal remanent magnetization (SIRM). The result really Show the transformation of magnetic minerals in geothermal wells which have undergone different pressure and temperature conditions. Additionally, paleomagnetic measurements will be carried out to determine the movement and evolution of rocks over geological time.

How to cite: Cabuk, B. S., Cengiz, M., and Karabulut, S.: The Role of Magnetic Properties of Rocks in Determining the Geothermal Potential in the Western Anatolia Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-889, https://doi.org/10.5194/egusphere-egu25-889, 2025.

How to cite: Schanner, M. A., Bohsung, L., and Korte, M.: Kalman filter based modeling of the Holocene geomagnetic field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2794, https://doi.org/10.5194/egusphere-egu25-2794, 2025.

One of the most prominent changes in Earth’s magnetic field over the past two centuries is the growth of the South Atlantic Anomaly (SAA)—a region of significantly weakened field intensity. Recent studies have suggested that weak field anomalies such as the SAA are recurrent features of the geomagnetic field, preferentially occurring around certain longitudes and generally drifting westward. These observations have sparked hypotheses linking the weak field anomalies to heat-flux heterogeneities at the core-mantle boundary and/or an eccentric planetary-scale gyre as observed in modern core surface flow reconstructions. To further investigate the underlying mechanisms, we generate core surface flow models that are compatible with the observed geomagnetic field changes. Several recent studies have made use statistics derived from geodynamo simulations to provide physically motivated priors on the core surface flow. Here, we adapt these methods to infer possible core flow solutions spanning the past 9000 years, constrained by archaeomagnetic and sedimentary palaeomagnetic data. Synthetic data are used to explore the extent to which archaeo-/palaeomagnetic observations can recover large-scale core flow variations. The integrated core-field and core-flow modelling approach is then applied to real-world data and the results are discussed within the context of recurrent weak field anomalies.

How to cite: Nilsson, A., Suttie, N., Gillet, N., and Aubert, J.: Core surface flow and geomagnetic field changes on millennial timescales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4289, https://doi.org/10.5194/egusphere-egu25-4289, 2025.

The reorientation of Earth through rotation of its solid shell relative to its spin axis is known as True polar wander (TPW). It is well-documented at present, but the occurrence of TPW in the geologic past remains controversial. This is especially so for Late Jurassic TPW, where the veracity and dynamics of a particularly large shift remain debated. Here, we report three palaeomagnetic poles at 153, 147, and 141 million years (Myr) ago from the North China craton that document an ~12° southward shift in palaeolatitude from 155–147 Myr ago (~1.5° Myr^-1), immediately followed by an ~10° northward displacement between 147–141 Myr ago (~1.6° Myr^-1). Our data support a large round-trip TPW oscillation in the past 200 Myr. By comparison of Jurassic paleomagnetic poles of the NCC and SIB, we suggest that the Late Jurassic true polar wander event may have biased paleomagnetic results and thereby affected the interpretation of the final closure of the Mongol-Okhotsk Ocean. Combining paleomagnetic data with regional geological evidence, we propose that the Mongol-Okhotsk Ocean was closed in its eastern segment in the Late Jurassic, marking the formation of the central Asian continent. We suggest that the shifting back-and-forth of the continents may contribute to the biota evolution in East Asia and the global Jurassic–Cretaceous extinction and endemism.

How to cite: Zhao, P., Hou, Y., Qin, H., Mitchell, R., Li, Q., Hao, W., Zhang, M., Ward, P., Yuan, J., Deng, C., and Zhu, R.: Late Jurassic true polar event revealed by paleomagnetic study in the North China Craton and its implication for regional tectonics and biota evolution in East Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4914, https://doi.org/10.5194/egusphere-egu25-4914, 2025.

    The West Pacific-East Asia transition zone is characterized by a remarkable continental mosaic system and a chain of marginal basins. However, the complexity of the continental amalgamation process has led to controversy regarding the origin and migration of many micro-continents. In particular, the origin of the East China Sea (ECS) remains a subject of debate. The question of whether the ECS is "part of the South China Block (SCB)" or an "exotic microcontinent" has yet to be definitively resolved (Niu et al., 2015; Fu et al., 2022). Furthermore, there is divergence in perspectives concerning the evolution of the ECS, exemplified by models such as "back-arc spreading" and "strike-slip pull-apart", which in turn fuel disputes regarding the nature of the ECS basin.

    In this study, we conducted paleomagnetic sampling of Cretaceous-Eocene cores from nine boreholes in the ECS basin. A systematic paleomagnetic study was undertaken, employing rock magnetic experiments, scanning electron microscope (SEM) analysis, and stepwise thermal demagnetization. Utilizing the inclination data of characteristic remanent magnetization (ChRM) obtained from thermal demagnetization experiments, we have, for the first time, derived paleomagnetic records for Early Cretaceous to Eocene cores from the ECS boreholes. The results indicate that the paleolatitudes of the ECS were 18.7° ± 4.5° (134 Ma), 21.4° ± 6.4° (107.2 ± 0.6 Ma), 18.1° ± 4.5° (66-61 Ma), 20.3° ± 4.3° (61-56 Ma), and 26.4° ± 8.2° (49-34 Ma). The investigation and comparison of the paleomagnetic data reveal that the paleolatitudes of the ECS are similar to those of the SCB from the Early Cretaceous to the Eocene. This suggests that the ECS and SCB have been part of the same tectonic block since the Early Cretaceous.

    Further analysis of the spatial relationship between the ECS and SCB confirms that their relative motions can be delineated into three distinct phases: (1) During the Cretaceous period, the ECS and the SCB moved in the same direction, albeit with a disparity in their velocities; (2) During the Late Cretaceous to Early Paleocene period, the ECS migrated northward while the SCB shifted southward; (3) During the Middle Paleocene to Eocene period, the ECS and the SCB moved in concert, with negligible differences in velocity, thereby establishing a stable connection. It is concluded that the kinematic transitions of the ECS and the SCB from the Early Cretaceous to the Eocene were directly governed by changes in the subduction direction of the Izanagi/Pacific Plate.

How to cite: Xu, M., Yang, F., and Hu, P.: Is the East China Sea an exotic microcontinent from the Paleo-Pacific? ——Paleomagnetic Insights from the East China Sea Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6135, https://doi.org/10.5194/egusphere-egu25-6135, 2025.

The Deccan Continental Flood Basalts (DCFB) are associated with three major dyke swarms: the Narmada-Satpura-Tapi (N-S-T), the Western Coastal, and the Nasik-Pune swarms. The DCFB around Pachmarhi is characterized by a lower Magnesium number (Mg#) and higher TiO₂ content, suggesting a more evolved composition compared to other Deccan basalts. Located in the eastern segment of the N-S-T swarms, the Pachmarhi dyke swarms comprise approximately 244 mapped doleritic and basaltic dykes, with lengths ranging from 140 m to 22 km, averaging ~5.15 km. These dykes are emplaced along pre-existing fractures and predominantly exhibit an E-W orientation. Petrographic and rock magnetic analyses indicate that the primary remanence carriers are high- and low-titanium magnetite particles, primarily in the pseudo-single domain state, with a minor contribution from multi-domain grains.

Paleomagnetic studies have been conducted on 12 dykes, revealing that five exhibit normal polarity while seven display reverse polarity. The normal-polarity dykes are characterized by a mean ChRM direction of D_m = 332°, I_m = -39.8° (k = 90.24, α₉₅ = 8.16°, N = 32), whereas the reverse-polarity dykes exhibit D_m = 156.1°, I_m = 38.1° (k = 55.4, α₉₅ = 8.02°, N = 63). The combined mean ChRM direction has been determined as D_m ≈ 334° and I_m ≈ -38.95° (k = 72.82, α₉₅ = 8.09°, N = 95). The calculated paleopole for the Pachmarhi dykes (37.97° N, 88.38° W) closely corresponds to that of the Nandurbar-Dhule (N-D) dykes (38.3° N, 79.9° W), which represent the western segment of the N-S-T dykes. The averaged paleopole position (38.14° N, 83.84° W) aligns well with the Deccan Superpole (36.96° N, 78.7° W). This similarity suggests that the emplacement of these dykes occurred synchronously during the late stages of Deccan volcanism. The Pachmarhi dykes with normal polarity have been tentatively linked to magnetic chron 29N, while those with reverse polarity correspond to chron 29R. It is inferred that these dykes may have fed late-stage Deccan flow units, such as the Ambenali and Mahabaleshwar formations of the Wai Subgroup. The paleolatitudes of the Pachmarhi (22.4° S) and N-D (25.4° S) dykes indicate minimal latitudinal variation, supporting the hypothesis of near-synchronous emplacement across the Narmada-Son-Lineament (NSL) region.

How to cite: Shukla, G., Lakshmi, B., and Mallik, J.: Paleomagnetic evidence of synchronous emplacement of Deccan dykes along the Narmada-Son Lineament witnessing the magnetic reversal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6567, https://doi.org/10.5194/egusphere-egu25-6567, 2025.

Pyrrhotite is conspicuous by its very strong magnetocrystalline anisotropy of magnetic susceptibility (AMS) that can be in turn used in the investigation of the preferred orientation of this mineral by crystal lattice in rocks. Unfortunately, the AMS of pyrrhotite-bearing rocks is often composite, carried not only by pyrrhotite, but also by magnetite and mafic silicates; contribution of pyrrhotite can even be overwhelmed by that of the other minerals. It is therefore desirable to separate the AMS component due to pyrrhotite from that due to the rest of the rock. This can be made using the anisotropy of the out-of-phase component of magnetic susceptibility (opAMS), which can be obtained through AMS measurement in alternating magnetic field. Namely, the out-of-phase susceptibility (opMS) of paramagnetic minerals as well as of pure magnetite is virtually zero, while it is clearly non-zero in pyrrhotite. However, the problem is with measuring precision. As shown earlier, the error in opMS determination increases with decreasing phase angle, reaching extremely high values for phase near zero. And the phase is affected not only by opMS but also by ipMS of the measured specimen. It is therefore desirable to study the properties of the opMS and opAMS of real rocks. 

The opMS of the pyrrhotite-bearing rocks investigated increases significantly with the field intensity and the increase is faster in very low fields (<100 A/m) than in stronger low-fields. The Rayleigh Law range, in which magnetization is linearly related to the field, is relatively narrow, less than 40 A/m. The principal directions of the opAMS are virtually field independent in the entire low-field range used (10 to 700 A/m) being also very well parallel to the ipAMS directions. The degree of opAMS is also virtually field independent, but much higher than the degree of ipAMS. The shape parameter in opAMS is also field independent and resembles that in ipAMS. Theoretical quadratic relationship exists between the degree of anisotropy of initial ipMS and that of the tensor of Rayleigh coefficient characterizing the opAMS. Searching for empirical relationship between degrees of the opAMS and ipAMS measured in stronger low fields is the purpose of the present paper.

Physically purest is evidently measurement of opAMS in very weak field, conveniently within the Rayleigh Law range. On the other hand, measurement of the opAMS in the strongest low-field available (700 A/m) is more convenient from the point of view of measuring precision. This is fully convenient if one is interested above all in principal directions and ellipsoid shapes, which are evidently field independent and closely resemble those of ipAMS, and less precise as for the degree of opAMS, which is significantly higher than degree of ipAMS. This must be respected in geological interpretation of the data.

How to cite: Hrouda, F., Chadima, M., and Ježek, J.: Low-field variation of out-of-phase susceptibility of pyrrhotite-bearing rocks and its implications for rock fabric studies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10873, https://doi.org/10.5194/egusphere-egu25-10873, 2025.

Low-field magnetic susceptibility of diamagnetic and paramagnetic minerals as well as that of pure magnetite and all single-domain ferromagnetic (s.l.) minerals is field-independent. In contrast, magnetic susceptibility of multi-domain pyrrhotite, hematite and titanomagnetite may significantly depend on the field intensity. Hence, the AMS data acquired in various fields have a great potential to separate the magnetic fabric carried by the latter group of minerals from the whole-rock fabric. The determination of the field variation of AMS consist of separate measurements of each sample in several fields within the Rayleigh Law range and subsequent processing in which the field-independent and field-dependent susceptibility tensors are calculated.

Using a 3D rotator developed for the MFK1/2/KLY5 series of AGICO Kappabridges, the measurement is fully automated in such a way that, once the sample is mounted into the rotator, it requires no additional positioning to measure the full AMS tensor. The important advantage of the 3D rotator is that it enables to measure AMS in a sequence of pre-set field intensities without any operator manipulation. Whole procedure is computer-controlled and, once a sequence of measurements is finished, the acquired data are immediately processed and visualized. Examples of natural rocks demonstrating various types of field dependence of AMS are given.

How to cite: Chadima, M. and Hrouda, F.: A simple toolbox for separation of field-independent and field-dependent AMS tensors using a sequence of fully automated measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11075, https://doi.org/10.5194/egusphere-egu25-11075, 2025.

In this presentation, we review the methodological, geomagnetic, and chronological insights gained from a newly developed high-resolution archaeomagnetic intensity curve for the Levant spanning over the past 9 millennia. The new compilation includes a variety of archaeological materials collected from Israel, Syria, Iraq, and Jordan, primarily dated using radiocarbon and/or historical constraints. Paleointensity data were obtained using two different methods: Triaxe, and Thellier-IZZI-MagIC incorporating anisotropy and cooling rate corrections. To validate the two methods, we tested a set of 30 self-made pottery vessels crafted from six different clay types using traditional techniques. The results demonstrated that baked clay materials dominated by pseudo-single domain vortex state serve as excellent recorders of the field.  Yet, to ensure robust results, data should be averaged from at least three fragments per archaeological context, with a minimum of three specimens per fragment. We confirm that in non-single domain recorders, thermoremanent magnetization exhibits a logarithmic dependence on the cooling rate, consistent with single domain theory. After applying stringent selection criteria, the current dataset comprises nearly 1700 samples (fragments) - mainly indicative pottery, fired structures, tiles, furnaces, and slag - from 310 different well-dated archaeological contexts. With the exception of a few short time intervals, the temporal resolution of the data is a century or better, enabling the construction of a continuous Bayesian curve covering the past nine millennia. This curve provides geomagnetic insights into the amplitude and rates of geomagnetic secular variations. Finally, we present a few case studies demonstrating the application of the curve for archaeomagnetic dating.

How to cite: Shaar, R., Gallet, Y., Hassul, E., Bar-Sovik, L., and Vaknin, Y.: Archaeomagnetic Intensity Curve for the Levant (9000 BP - Present) in Sub-Centennial Resolution: Methodological, Geomagnetic, and Chronological Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12593, https://doi.org/10.5194/egusphere-egu25-12593, 2025.

North Anatolia is defined by a magmatic arc which occurred as a result of the subduction of the Late Cretaceous Neotethys ocean under the Pontides. This arc shape is 2700 km long, and can be observed from the Lesser Caucasus on the southern edge of Eurasia to the Apuseni, Banat, Timok, Srednogorie line along the northern edge of the Pontides. The paleolatitude of the Pontide volcanic belt was the aim several studies that pointed to a position of 28°N-24°N, while paleomagnetic rotations were interpreted with either by an oroclinal bending model or the excursion of Anatolia to the west. In the Balkans, however, Middle Triassic and Jurassic rocks showed no rotation or remagnetization in several areas. This study depend of the paleomagnetic results from the Upper Cretaceous İğneada Group in the northernmost part of the Western Pontides, Turkiye and the Burgas groups rocks outcropped in the Srednogoria belt in Bulgaria. The results showed that the arc type rocks were remagnetized in localy areas due to hydrothermal alteration associated with Cu-Au mineralization. The paleolatitudes obtained from both volcanic and sedimentary rocks, on the other side, were compared with the results from the Pontide magmatic arc.

How to cite: Cengiz, M. and Karabulut, S.: Paleomagnetic Constraints on the Tectonic Evolution of the Upper Cretaceous magmatic arc rocks in Western Pontides, Türkiye and Srednogorie, Bulgaria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14640, https://doi.org/10.5194/egusphere-egu25-14640, 2025.

The study of geomagnetic field variations provides information on the Earth's inner dynamics, helps understanding the role of the Earth's magnetic field as the primary shield against cosmic radiations and is also used as a geochronological tool for dating archaeological artefacts. Geomagnetic field variations during the Early Medieval Age (EMA) in Central Europe are generally poorly constrained due to the scarcity of archaeological sites. While a rapid intensity increase in the 6th century, along with high intensity values for the 7th to 9th centuries, have been reported for Western Europe, new archaeointensity data from other regions is thus needed in order to reconstruct more closely the spatio-temporal geomagnetic field evolution.

This work focuses on the study of the secular variations during the EMA period for selected regions in Central Europe : Germany, Austria and Poland. We analyzed potsherds from Ternitz and Unterrohrbach, and baked clay from Frauenkogel in Austria. In Poland, we examined potsherds from Klenica and Chobienia from two different locations; for the latter also daub and baked clay of a drying pan have been investigated. Finally, we studied kiln rocks from Schnapsweg and baked clay of a rampart from Fergitz in Germany.

For setting up the archaeointensity measurements, we used thermal demagnetization of the NRM and thermal κ(T) cycling to determine the unblocking temperature spectra and alteration behavior. The MT4 protocol – a Coe variant of the Thellier method - was used, including pTRM, tail checks and additivity checks, as well as corrections for anisotropy and cooling rate effects. Modified selection criteria sets TTA and TTB were applied. For Ternitz and Fergitz sites, we also used the multi-specimen domain-state corrected (MSP-DSC) protocol. Rock magnetic experiments comprised hysteresis and backfield curve measurements.

Between 500 and 700 AD, results of Unterrohrbach and Ternitz yield palaeointensities around 50 µT. While the MT4 site mean for Ternitz is characterized by high scatter, MSP-DSC experiments revealed a reliable archaeointensity. For Unterrohrbach site, a similar value with a lower scatter is determined. Finally, results from Frauenkogel site, suggest a rapid and strong increase of the archaeointensity within 100 to 150 years to high values around 85 µT. Similar high values were obtained in France. After this maximum, a strong intensity decline is indicated by the results from the remaining sites.

How to cite: Ségué-Passama, G., Schnepp, E., Arneitz, P., Leonhardt, R., and Egli, R.: Strong secular variation in Central Europe during the Early Medieval Ages, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15788, https://doi.org/10.5194/egusphere-egu25-15788, 2025.

The Earth’s magnetic field, generated in the liquid outer core, predominantly behaves as a dipole over time. The processes generating the magnetic field, however, are complex and therefore also generate higher order pole signals. These higher order pole signals can alter the Earth’s magnetic field on a short time scale, even when the dipole signal is strong. A substantial deviation from the current dipole field is the South Atlantic Anomaly (SAA), a large weak spot in the Earth’s magnetic field above South-America. In the SAA’s center, the magnetic field strength is ~22 μT, approximately half of the field strength at the same latitude in Australia.

To better understand the origin and evolution of the SAA, it is essential to develop high-quality geomagnetic models of the Earth’s magnetic field over the past millennia. A major challenge for the current geomagnetic models is the significant data absence from the Southern Hemisphere, where the SAA is located. This lack of data hinders accurate modeling of the SAA’s evolution over time.

Our research aims to increase the amount of data on the Southern Hemisphere, particularly at locations on the same latitude as the current SAA. These locations are chosen based on the observation that the SAA has been moving westward over the past few decades, leading to the hypothesis that this westward movement has been ongoing for a longer period. We are currently working on enhancing the amount of data by adding high-quality full-vector paleomagnetic data from volcanic deposits on Réunion Island, Bali and Fiji.

Here we present the results of our paleomagnetic study of lava flows from Taveuni, Fiji, revealing a remarkable weak magnetic field of approximately 12 μT in flows dated to around 600 years ago. These flows also have a 20-30 degrees deviation in declination and inclination from expected values. Incorporating this new data into the global geomagnetic dataset allows us to refine existing models, leading to the unexpected conclusion that this exceptionally low field intensity cannot be attributed to the South Atlantic Anomaly—located below Africa at the time—but rather points to the presence of another geomagnetic feature: a West Pacific Anomaly.

How to cite: van Grinsven, L., Out, F., van den Bosch, M., Meyer, R., and de Groot, L. V.: New Evidence for a West Pacific Anomaly: Paleomagnetic Data from Taveuni, Fiji, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18828, https://doi.org/10.5194/egusphere-egu25-18828, 2025.

Data-based geomagnetic models are key for mapping the global field, predicting the movement of magnetic poles, understanding the complex processes happening in the outer core, and describing the global expression of magnetic field reversals. There exists a wide range of models, which differ in a priori assumptions and methods for the interpolation of data in space and time. A frequently used modeling procedure is based on regularized least squares (RLS) spherical harmonic analysis, which has been used since the 1980s. This technique minimizes the error between modeled observations and data while constraining the model to realistic values, although some of these constraints have (partially) lost their physical foundation.

The first version of this algorithm has been written in Fortran and led many different research groups to produce versions of the algorithm in other programming languages, either published open-access or only accessible within the institute. To open up the research field and allow for reproducibility of results between existing versions, we provide a user-friendly open-source Python version of the RLS algorithm accompanied by six spatial and two temporal damping methods from literature to enforce a spatially and temporally realistic magnetic field. We also provide a comprehensive discussion of key background concepts - concerning Maxwells equations, spherical harmonics, cubic B-Splines, and regularization – for a deeper understanding of the theoretical foundation of RLS geomagnetic models.

While Python is known for its readability, it is often criticized for its high overhead costs. We addressed this issue by leveraging the banded structure of the normal equations and incorporating C-code (via Cython) for matrix operations, significantly improving speed. As a result, the algorithm can run on a standard laptop with performance comparable to its Fortran predecessor. We show how to employ the new lightweight and quick algorithm with ample examples from our four included tutorials. With this well-documented open-source Python version, we aim to encourage both existing and new users to create their own geomagnetic models and further advance the method.

How to cite: Out, F., Schanner, M., van Grinsven, L., Korte, M., and de Groot, L.: pymaginverse: a python package for global geomagnetic field modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18949, https://doi.org/10.5194/egusphere-egu25-18949, 2025.

We present a paleomagnetic study of 471–454 Ma (Dapingian to Sandbian) limestones from the Siljan (Sweden) impact structure, offering new insights into Baltica’s paleogeography and the Mid–Late Ordovician geomagnetic polarity timescale. Stepwise thermal demagnetization revealed a primary magnetization component that passes fold and reversal tests. Our data indicate Baltica’s initial stationary phase at ~55°S during the Dapingian–Early Darriwilian, followed by rapid northward drift (~35 cm/year) starting in the Middle Darriwilian and slowing to ~15 cm/year by the Sandbian (~33°S). Furthermore, we established a detailed polarity timescale and correlated it with Ordovician outcrops across Baltoscandia and the Siberian platform. Based on our magnetostratigraphic data, we defined the end of the Ordovician superchron at 465.7 Ma, further advancing its temporal resolution. Our findings align with prior studies, including normal polarity chrons in the Mid and Late Darriwilian stages, and limit the superchron's maximum duration to about 14 Myr. 

How to cite: Ahanin, N., Gilder, S., Ebbestad, J. O., and Almqvist, B.: Reconstructing Baltica’s Ordovician paleogeography and pinning the end of the Ordovician Superchron: Paleomagnetic data from Siljan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20844, https://doi.org/10.5194/egusphere-egu25-20844, 2025.

Collision of the Indian and Asian continental plates and subsequent northwards subduction of the Indian plate beneath the active Andean-type southern margin resulted in the intrusion of a 2500km long Trans-Himalayan calc-alkaline batholith known as the Ladakh Plutonic Complex, or Ladakh Batholith. The Ladakh batholiths lies sandwiched between the Indus Suture Zone in the south and is unconformably overlain by the post-collisional Indus Molasse Group. In the Chumathang area, SE of Leh, the batholith (⁓ 400 mts high) is represented by two major granitoid phases exposed on the eastern side of Indus river. The granodiorite (57.7 ± 0.2 Ma) is dark-colored, massive, medium to coarse grained composed of plagioclase, quartz, hornblende, biotite with minor titanite, apatite, zircon, epidote, magnetite, ilmenite. The younger leucogranite (47.1 ± 0.1 Ma) is a relatively fine-grained rock containing quartz, plagioclase, and biotite with minor muscovite, zircon, tourmaline, and allanite. Several pegmatite veins of variable thickness are seen cross-cutting both phases of granite and at times intrude into the older metasediments.

Compositionally, these veins are dominated by quartz, plagioclase, orthoclase, microcline and minor biotite, muscovite, and zircon. Minerals like tourmaline, chlorite, fluorite, aquamarine, baryte etc. are commonly observed along vein margins. The Chumathang granitoids exhibit pervasive hydrothermal alteration, with pronounced chloritization observed in proximity to fluorite mineralization zones. Chlorite is seen closely associated with biotite (K = > 1wt.%) with enriched Fe, Mn and Mg concentrations indicating elevated oxygen fugacity conditions. Flourite typically occurs in variable colors like green, purple, white and brown indicating different stages of fluid evolution. Ca contents vary between 55.27 wt.% to 60.85 wt. % with F varying between 41.33 to 46.39 wt.% higher than previous reports. Allanite, a REE-rich mineral belonging to the epidote group, has been identified in the present study. Allanites exhibit compositional zoning with rims enriched in Ca, Mg and Al as compared to core. Aquamarine, the blue to greenish-blue gem variety of beryl has also been identified in the pegmatites from the study area. Presence of predominant minerals like biotite, amphibole and epidote clearly suggest that both phases of granites and pegmatites were formed from a high temperature magma source. Secondary minerals like chlorite, fluorite, allanite and aquamarine found associated with the host rocks indicate derivation from a complex interplay of both late stage pegmatitic as well as hydrothermal melts. The observed accessory and secondary minerals from the study area provide key insights into magmatic differentiation, post-magmatic fluid activity, thermal history, and mineralization potential and economic potential of such plutonic complexes.

Keywords: Ladakh Batholith, Chumathang granitoids, pegmatites, magma crystallization, hydrothermal alteration

How to cite: Bhoir, D., Jonnalagadda, M., Walunj, G., Sanklecha, H., Bose, R., Kulkarni, B., Duraiswami, R., and Karmalkar, N.: Petrogenesis of magmatic and hydrothermally derived late stage minerals associated with granitic plutonic complexes: A case study from the Ladakh Batholith, NW Himalayas, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-331, https://doi.org/10.5194/egusphere-egu25-331, 2025.

The evidences of deep melting processes in xenolith bearing mafic rocks in Southern Thrace region: The new insights for peridotite and the pyroxenite source melting

       Xenolith bearing mafic rocks with late Miocene age are widely distributed in southern Thrace region. Primitive mantle - normalised multi-element diagrams of these mafic rocks display OIB signature and specific incompatible element ratios such as Nb/La (1.65-2.05) Nb/U (37.81 -48.74), Zr/Ba (0.45-0.72) further indicate that mafic rocks were originated from the OIB-like component. Re content of xenoliths range between 0.09 – 0.44 and similar with fertile mantle values (0.26 ppb) suggested by Morgan (1986), besides, xenoliths (0.1191-.0.1379) and the host rocks (0.1279-0.1439) have the similar   ¹⁸⁷Os/¹⁸⁸Os isotopic compositions.

        Geothermobarometric analyses of clinopyroxene (Putirka, 2008) from host basalts express that the melting source resides at an estimated depth of around 85 km. In addition, Gd/Yb ratios span between 0.97-3.3 in xenoliths and also span between 3.92-5.24 in basaltic rocks, suggest melting from a deep source.The mafic lavas of Thrace region with high Tb/Yb(N) values (2.33 – 3.16) seem to be derived from garnet bearing peridotite (Tb/Yb(N) >1.8 Wang et al., 2002) and these ratios also gain significant support from Dy/Yb values that range between 2-2.43 for xenoliths and 1.98-3.27 for host rocks. High Nb/U, Gd/Yb ratios, Re-Os isotopic compositions, and the REE-based melting model starting from the primitive xenoliths (from study region) and pyroxenite source (Van Nostrand, 2015) reveal that single source melting is not capable of producing   the mafic lavas, instead, these rocks appear to originate from the melting of the deeper part of the mantle rather than shallow asthenosphere.

How to cite: Kurkcuoglu, B., Yürür, M. T., Günes, B., Furman, T., and Hanan, B.: The evidences of deep melting processes in xenolith bearing mafic rocks in Southern Thrace region: The new insights for peridotite and the pyroxenite source melting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-840, https://doi.org/10.5194/egusphere-egu25-840, 2025.

On June 10, 2021, a M 5.1 earthquake occurred in the region between two large parallel strike-slip faults in Shuangbai County, Yunnan Province. To investigate the earthquake's mechanism, the spatial and temporal distribution characteristics of the mainshock and its aftershock sequence were analyzed using template matching detection and relocation methods. Additionally, the regional stress field and fault slip tendency were examined. Other factors, such as tidal stress and the triggering effects of previous seismic events, were also considered. The results reveal that the 2021 M 5.1 Shuangbai earthquake sequence exhibited fluid-driven outward migration from the initial hypocenters. The study area is characterized by a strike-slip stress regime, with a nearly horizontal σ₁ oriented in the NNW-SSE direction and a horizontal σ₃. It was found that the seismogenic fault of the Shuangbai earthquake sequence was not optimally aligned with the regional stress conditions. The findings suggest that fluid overpressure played a primary role, while tidal stress had a secondary influence, in the occurrence of the mainshock and its aftershocks.

How to cite: Xie, C., Huang, M., and xu, Y.: Physical mechanism of the 2021 M 5.1 Shuangbai earthquake and its aftershock sequence in Yunnan Province, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1917, https://doi.org/10.5194/egusphere-egu25-1917, 2025.

The European Variscan orogen (EVO) originated through tectonic accretion of few continental ribbons followed by collision of Gondwana and Laurussia, including docking of mantle parts of incoming terrains to the mantle wedge. At the late- and post-orogenic stage, the thickened orogenic root (Moho depth ca 55-60 km) flattened by lateral crustal flow and gravitational collapse [1], although this was not uniform across the EVO. In the Bohemian Massif, the crust is still fairly thick (ca. 35 km) and the impact of gravity-driven lateral flow of partially molten orogenic root was rather limited [2]. In contrast, the geology of French Massif Central (FMC) reflects the importance of lateral flow of the partially molten crustal orogenic root and its exhumation in crustal-scale domes beneath low-angle detachments. Where flattening occurred, it produced a relatively flat Moho at ca 30-32 km depth [3]. Thus, the lithospheric and asthenospheric mantle underlying the orogen must have been exhumed by 20-30 km.

The mantle parts of the EVO are sampled – as peridotite xenoliths – by numerous Cenozoic alkaline lavas of the Central European Volcanic Province. Despite locally strong Cenozoic metasomatic overprint, these xenoliths offer the opportunity to decipher the evolution of lithospheric mantle from which they come [4] including whether the xenoliths can constrain which parts of the Variscan orogen escaped delamination.

Slices of Variscan “orogenic peridotites”, attached to the growing orogen, now occur in the exposed basement “massifs”. They usually belong to the peridotite garnet facies (e. g. [5]), whereas the peridotite xenoliths occurring in Cenozoic lavas are exclusively spinel peridotites [6], confirming that large part of lithospheric mantle underlying EVO was exhumed from garnet- to spinel-facies P-T conditions. This decompression is recorded by spinel-pyroxene symplectites after garnet in some xenoliths, such as at Montboissier in the northern FMC domain.

Indeed, the xenoliths sampling large parts of the EVO lithospheric mantle are clinopyroxene-poor and depleted in major melt-mobile elements, suggesting that they represent lithospheric mantle fragments tectonically attached to the orogen root during orogenesis (“Variscan orogenic mantle” of [5]) which escaped subsequent delamination.

Our analysis suggests that lithospheric mantle evolution deciphered from xenoliths, if combined with geological data on crust evolution, allow to elaborate more pertinent tectonic-geodynamic models of EVO.

Funding. This study originated thanks to the project of Polish National Centre of Research 2021/41/B/ST10/00900 to JP.

[1] Vanderhaeghe, O., Laurent, O., Gardien, V.Moyen, J.-F., Gébelin, A., Chelle-Michou, C., Couzinie, S., Villaros, A., Bellanger, M., 2020. BSGF-Earth Sciences Bulletin 191, 25.

[2] Schulmann, K., Lexa, O., Janoušek, V., Lardeaux, J.M. and Edel, J.B. 2014. Geology, 42, 275–278

[3] Artemieva, I., Meissner, R., 2012. Tectonophysics 530-531, 18-49.

[4] Puziewicz, J., Aulbach, S., Kaczmarek, M.-A., Ntaflos, T., Matusiak-Małek, M., Ziobro-Mikrut, M., Gerdes, A., 2025. Lithos 494-495, 107908.

[5] Kubeš, M., Čopjaková, R., Kotková, J., Ackerman, L., Haifler, J., Výravský, J., Holá, Škoda, R., Leichmann, J., 2024. Journal of Petrology 65, egae108.

[6] Puziewicz, J., Matusiak-Małek, M., Ntaflos, T., Grégoire, M., Kaczmarek, M.-A., Aulbach, S., Ziobro, M., Kukuła, A., 2020. Lithos 362-363, 105467.

How to cite: Puziewicz, J., Aulbach, S., Vanderhaeghe, O., Grégoire, M., and Ziobro-Mikrut, M.: Evolution of the of Variscan orogenic mantle root in Europe viewed through combined analysis of tectonic models and mantle xenoliths, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2372, https://doi.org/10.5194/egusphere-egu25-2372, 2025.

Fluid segregation in deep-seated rocks has profound implications for their physical and chemical properties. Gravity drives the segregation of fluids interconnected through grain edges and corners, along with the compaction of the rock matrix, whereas isolated fluids are retained in the rocks. For wetting fluids, the critical volume fraction (i.e., percolation threshold) separating these two cases is principally determined by the balance and anisotropy of solid-fluid interfacial tensions (i.e., dihedral angle and faceting effect); however, the processes controlling the percolation threshold for non-wetting fluids are unclear, despite their critical importance, especially in the amount of pore fluids down-dragged in subducting slabs to the Earth’s interior. Hence, we implemented a combined approach involving high-pressure rock synthesis, high-resolution synchrotron radiation X-ray computed microtomography (CT) imaging, and numerical permeability computation to better understand how the permeability decreases and fluids are retained at low fluid fractions. We chose quartzite as a well-studied natural rock analog that is simplified but does not lose its essence as a silicate polycrystalline aggregate. A mixture of finely ground quartz and amorphous silica powders was sealed in Pt-lined Ni capsules with C-O-H fluid sources at different fractions and compositions and hot-pressed using a piston-cylinder apparatus. The dihedral angles of the experimental systems were 52° and 61–71° for the wetting and non-wetting systems, respectively.

In the wetting system, fluid connectivity rapidly decreased to approximately zero when the total fluid fraction decreased to 3.0–3.7 vol. %, mainly due to the grain faceting effect, consistent with the results of the previous study. In the non-wetting systems bearing CO₂-rich fluids, the cutoff of fluid tubules isolated 4.8–6.2 vol. % of the fluid. A streamline computation based on the X-ray CT images of the experimental products revealed that the fluid flow just above this threshold focused on a few channels, establishing efficient channelized fluid pathways. These retained fluid fractions are higher than those in the previous assessment based solely on the dihedral angle, that is, the pinch-off condition for ideal (isotropic and homogeneous) fluid geometry and the equilibrium fluid fraction that minimizes the total interfacial energy of the fluid-rock system. Hence, the amount of aqueous fluids dragged down to the Earth’s interior could be higher than previously estimated, although the specific volume fraction depends on the anisotropy and heterogeneity of the system of interest.

How to cite: Nakamura, M., Fujita, W., Uesugi, K., Eichheimer, P., Thielmann, M., and Golabek, G.: Fluid segregation and retention in deep‑seated rocks near percolation thresholds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2750, https://doi.org/10.5194/egusphere-egu25-2750, 2025.

Metamorphic soles are key petrotectonic units that offer valuable insights into the processes governing ophiolite emplacement. Ophiolite obduction involves complex thermomechanical phenomena and is associated with limited petrological data. In this work, we have investigated the metamorphic sole of the Pindos ophiolite in northwestern Greece. In the studied locality, the sole is sandwiched between mantle peridotites and pillow lavas of N-MORB affinity. We mainly focused on two lithologies: a garnet-mica metapelite and an amphibolite. Petrographic investigation of the metapelite revealed quartz inclusions in garnet indicating syn-kinematic growth, asymmetric quartz ribbons and S-C shear bands of syn-kinematic mica, all being consistent with top-to-the-NE shearing. Petrographic and textural evidence, temperature calculations (Fe-Mg garnet-biotite exchange and paragonite-muscovite solvus thermometry), and phase-equilibria modelling using an effective bulk composition bracket metamorphism at amphibolite-facies conditions (ca. 620-640°C and 1.1-1.2 GPa). Moreover, Quartz-in-Garnet (QuiG) barometry yielded a pressure of ~1.2 GPa for 635°C demonstrating that the syn-kinematic growth of garnet took place under high-pressure conditions. New ⁴⁰Ar/³⁹Ar geochronology of syn-kinematic muscovite from the metapelite and amphibole from the amphibolite showed an apparent minimum age of 164.16 ± 0.37 Ma and a consistent age plateau at 165.5 ± 0.73 Ma respectively. Notably, the amphibole exhibited no evidence of argon loss, suggesting its apparent age closely represents the time of formation. The muscovite age, by contrast, should be considered a minimum apparent age due to the potential influence of argon diffusion. Despite this limitation, the studied metapelite represents, in all probability, metamorphosed pelagic sediments in association with oceanic crust of N-MORB affinity. A combination of heat conduction from the overlying peridotite and shear heating developed during emplacement are considered responsible for the formation of the metapelite. Our joint petrological, geochronological and structural data indicate that the Pindos metamorphic sole records evidence of rapid thrusting (<2.5Myr) of the ophiolite from a westerly oceanic tract (Pindos Ocean) onto the Pelagonian margin over to the east in Callovian times (uppermost mid-Jurassic).

How to cite: Moutzouris, D., Moulas, E., Kostopoulos, D., and Pomonis, P.: Emplacement of the Pindos ophiolite, NW Greece: P-T-t-kinematic constraints from the metamorphic sole, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4266, https://doi.org/10.5194/egusphere-egu25-4266, 2025.

The eruption risk of a volcano depends on how much melt and gas have built up in its magmatic hydrothermal system in the upper crust. However, it is still challenging to characterize their spatial distributions and quantitatively estimate their concentrations. By integrating geophysical imaging results, petrological analysis and rock physics models, we mapped the migration pathways of fluids and gases and estimated their concentrations beneath Uturuncu volcano in Bolivia. This volcano last erupted 250,000 years ago, and our results explain why it still shows activity and are helpful for assessing its future eruption risks. This study shows how combining seismology, petrology and rock physics can help resolve the internal structure and composition of hydrothermal system beneath a volcano.

How to cite: Liu, Y., Kendall, M., Zhang, H., Blundy, J., Pritchard, M., Hudson, T., and MacQueen, P.: Unraveling the structure of the magmatic hydrothermal system beneath Uturuncu Volcano by joint seismological and petrophysical analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4668, https://doi.org/10.5194/egusphere-egu25-4668, 2025.

Central Italy is affected by a significant migration of deep CO₂ through the crust. CO₂ upraise gives rise to numerous gas emissions in the western Tyrrhenian domain where extensional deformation has dismantled the compressional structures, enabling fluid emissions through a mature set of normal faults. Conversely, the thickened crust and the abundant groundwater circulation in carbonate aquifers of the Apennine “trap” migrating deep fluids. Here, in the eastern Apennine sector, deep CO₂ dissolves in the large carbonate aquifers, while the CO₂ anomalies disappear in the easternmost Adriatic domain. This divide is reflected in seismicity patterns, with Apennine earthquakes clustering close to the degassing anomaly boundary. Significant variations in dissolved deep CO₂ were observed in some springs from large Apennine aquifers during the seismic crises of L’Aquila 2009 and Central Italy 2016-17, suggesting feedback mechanisms between CO₂ degassing and seismicity. The region is also characterised by a dense hydrological network (i.e., the Tiber River Basin, TRB) running in the different tectonic settings, with some major rivers collecting water from areas where CO₂-rich springs, sensitive to the seismic activity, are present. In this framework, a two-year geochemical survey of the major rivers of TRB was conducted aimed to explore the reliability of investigating the regional CO₂ degassing process and its relations with the seismicity by studying the river’s waters. In addition to the geological peculiarities, this area is suitable for this objective, due to the well-developed hydrometric network managed by local authorities, allowing to couple geochemical and hydrological data. More than 350 river water samples were collected from the Tiber river and its 12 main tributaries. A large geochemical dataset including major ions and dissolved inorganic carbon isotopic compositions was produced covering different hydrological periods. Results show that river waters exhibit compositions and variability resembling those of the Apennine groundwaters, allowing to identify different fluids circulating in the crust. Compositional variation remains appreciable for long distances downstream of mixing between shallow and groundwaters and between rivers with different compositions, highlighting the preservation of the geochemical information over large areas. In particular, the content of dissolved carbon in river waters and its isotopic composition shows and preserves for long distances the signature of the input of deep CO₂-rich waters. Coupling river’s geochemical and flow rate data, fluxes of dissolved deep CO₂ were computed, providing results that closely match previous estimates based on spring data, indicating minor carbon loss along rivers. These findings highlight rivers as valuable indicators of deep CO₂ flux across large areas and potentially to investigate temporal variation of the flux. This study has been also focused on the definition of ‘easily detectable parameters’ (EDP) which correlate to dissolved deep CO₂. Measuring EDP at high frequency, together with the water flow rate, could provide a tool for monitoring variations of the deep CO₂ flux to enhance a possible geochemical monitoring of the seismic activity.

How to cite: Tieri, M., Cardellini, C., Chiodini, G., Caliro, S., Frondini, F., Cinti, D., Barberio, D., Di Renzo, D., Santi, A., Cuoco, E., Rufino, F., and Caracausi, A.: Deep fluids transported by Apennine rivers: quantification of deep CO2 emission and implications for geochemical monitoring of the seismic activity., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6264, https://doi.org/10.5194/egusphere-egu25-6264, 2025.

Olivine and its polymorphs are the dominant minerals in the upper mantle and transition zone. The olivine phase transitions, determined primarily by pressure and temperature, control mantle discontinuities and influence mantle dynamics. Pressure is a first-order control on olivine phase transition and relates primarily to depth; therefore, it is commonly used to interpret the depths of mantle discontinuities. However, mantle dynamic models predicted 100-300 MPa stress levels or as high as several GPa. Such stresses would affect the positions where mineral reactions occur and, hence, large-scale mantle structure. In this work, we focus on the feedback between pressure and stress on the olivine phase transition at grain scale, and then the results can be extrapolated and upscaled to mantle scale deformation.

We use the Open Phase Studio software based on the phase field model to simulate olivine phase transitions. The phase field model uses order parameters to distinguish different phases and describe their evolution. The parameter value of 1 indicates the bulk of the phase, and a value of 0 indicates the absence of this phase and is a smooth function of position. The smooth transition of a phase parameter indicates a diffuse interface between phases. The total free energies, including temperature-related, elastic and interfacial free energies, interface properties, and initial microstructure, govern the evolution of the phase field. We applied this model to the Forsterite (Mg₂SiO₄)-Wadsleyite (Mg₂SiO₄) phase transition under different stress boundary conditions. We considered both isotropic and anisotropic boundary stress conditions. Under isotropic stress conditions, we plotted the Forsterite-Wadsleyite phase transition boundary based on our simulation results. The results indicate that local pressure variations, characterized by lower pressure within the Wadsleyite grain, hinder the occurrence of the phase transition. The depth offset would be ~30 km depressed due to this problem, which would be seismically detectable. Under anisotropic stress conditions, the Wadsleyite phase grows faster towards the maximum compression direction, leading to an elongated grain shape; however, the deviatoric stress does not shift the phase transition boundary significantly. At the same pressure, the deviatoric stress slightly slows down the Wadsleyite growth in volume.

How to cite: Lu, L. and Wheeler, J.: Grain-scale simulation of olivine phase transition under stress: implications for mantle discontinuities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6808, https://doi.org/10.5194/egusphere-egu25-6808, 2025.

The Jurassic western-type ophiolites of the Tethyan Pindos oceanic basin are part of an ophiolite belt that extends within the Apulian and Pelagonian subcontinents in the Balkan Peninsula. These ophiolites tend to display MORB geochemical affinities, in contrast to the adjacent eastern-type ophiolites with SSZ affinities. The Orliakas locality in Pindos (Greece) and Krrabi in the Mirdita ophiolite (Albania) are two characteristic localities, representative of the south and north branches respectively of the Pindos western-type ophiolitic belt. Both localities include rodingitized gabbroic dykes hosted in highly serpentinized peridotites.

We report the occurrence of gabbronorite and olivine gabbro dykes of comparable thickness (0.5- 1.0 m) that were partly affected by rodingitization processes. In some cases, the gabbroic protoliths were found almost intact at the central parts of the dykes. Protoliths from the two localities exhibit highly comparable whole-rock geochemical properties: SiO₂: 48.1-49.3 wt.%, TiO₂: 0.08-0.11 wt.%, Al₂O₃: 16.7-18.0 wt.%, MgO: 12.2-13.5 wt.%; analogous REE patterns [(La/Yb)_CN=0.2-0.4; Eu_CN/Eu*= 1.65-1.82]. PM-normalized multi-element patterns are also evidently comparable: noticeable LILE enrichments (e.g. Cs, Ba), higher Th_PM-N and U_PM-N compared to Nb_PM-N and Ta_PM-N, striking positive Pb and Sr anomalies, negative Zr and Ti anomalies.

Within the same dykes from the two localities, rodingites are also highly comparable in terms of: i) participating minerals and modal composition; ii) presence of hydrogarnets of similar composition (Avg. Adr_4.0Grs_94.3Prp_1.6Sps_0.1Uv_0.1); iii) subparallel whole-rock PM-normalized multi-element patterns. In addition, the REE patterns obtained from LA-ICP-MS of the garnets, vesuvianites and clinopyroxenes display similar profiles. These features signify that similarities between the south and north branches of the Pindos ophiolitic belt are likely not limited to their magmatic lithotypes but may have also experienced comparable post-magmatic rodingitization processes, assigned to extensive infiltration of alkaline, Ca-rich, and Si-poor fluids.

How to cite: Koutsovitis, P., Tsiarsioti, L., Tsikos, H., Mason, P., Ntaflos, T., Pomonis, P., Karkalis, C., Rogkala, A., Petrounias, P., and Onuzi, K.: Comparable rodingitization processes identified in ophiolites from Pindos (Greece) and Krrabi (Albania)  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7412, https://doi.org/10.5194/egusphere-egu25-7412, 2025.

Combining the geochemistry of gas emissions in active volcanic regions with the signature of mineral-hosted fluid inclusions in mantle-derived xenoliths is the next frontier in geodynamics and volcano monitoring and can provide important clues on: i) the nature and evolution of the lithospheric mantle; ii) the storage and mobility of fluids through the lithosphere; and iii) the origin of fluids migrating within the mantle and in the plumbing system underneath active volcanoes.

In this study, we present new mineral and fluid inclusion chemistry (noble gases and CO2) data on a unique suite of mantle-derived xenoliths hosted in phonolite pyroclastic deposits in Mayotte island (Comoros archipelago, Indian Ocean), which was the scene of one of the largest submarine eruptions ever documented from 2018 to 2021 (Jacques et al. 2024).

The studied samples are spinel-bearing harzburgites and lherzolites, and are composed of Cr-spinel (Cr# = 0.4-0.55), Mg-rich olivine (Fo90-92, NiO = 0.3-0.5 wt%), orthopyroxene (Mg# = 91-92; Al2O3 = 1.5-3.0 wt%), and clinopyroxene (Mg# = 91-94; Al2O3 = 2.0-3.5 wt%). The mineral major and trace element distribution indicates that the xenoliths represent fragments of a residual lithospheric mantle which experienced 20 to 25% partial melting.

Olivine-, orthopyroxene-, and clinopyroxene-hosted fluid inclusions are CO2-dominated and have air-corrected 3He/4He isotopic ratios of 5.6-6.8 Ra that are intermediate between the typical signature of Mid-Ocean Ridge Basalt (MORB = 8±1 Ra) and Sub-Continental Lithospheric Mantle (SCLM = 6±2 Ra). Such He isotopic signature is similar to that of subaerial and submarine gaseous emissions in the Mayotte area (Liuzzo et al. 2021; Mastin et al. 2023).

With respect to the mantle xenoliths from the neighbouring Grande Comore Island (Coltorti et al. 1999; Bordenca et al. 2023), the peridotites from Mayotte lie within a narrower compositional range, being moderately depleted and not showing significant metasomatic enrichment. Despite comparable 3He/4He ratios, fluid inclusions in the Mayotte samples have higher 4He/40Ar* values than those of the refractory mantle (Rizzo et al. 2021), likely indicating a shallow overprint by magmatic fluids.

Mantle xenoliths and hosted fluid inclusion data are used here to model the melt-fluid/rock reactions in the lithospheric mantle, the genesis and ponding of magmas linked to the recent volcanic activity at Mayotte and the geodynamic setting of the Comores archipelago.

References

Coltorti, M., Bonadiman, C., Hinton, R. W., Siena, F., & Upton, B. G. J. (1999). Journal of Petrology, 40(1), 133-165.

Jacques, E., Hoste-Colomer, R., Feuillet, N., Lemoine, A., van der Woerd, J., Crawford, W. C., ... & Bachèlery, P. (2024). Earth and Planetary Science Letters, 647, 119026.

Liuzzo, M., Di Muro, A., Rizzo, A. L., Caracausi, A., Grassa, F., Fournier, N., ... & Italiano, F. (2021). Geochemistry, Geophysics, Geosystems, 22(8), e2021GC009870.

Mastin, M., Cathalot, C., Fandino, O., Giunta, T., Donval, J. P., Guyader, V., ... & Rinnert, E. (2023). Chemical Geology, 640, 121739.

Rizzo, A. L., Faccini, B., Casetta, F., Faccincani, L., Ntaflos, T., Italiano, F., & Coltorti, M. (2021). Chemical Geology, 581, 120400.

How to cite: Casetta, F., Faccincani, L., Rizzo, A. L., Faccini, B., Liuzzo, M., Nardini, N., Di Muro, A., and Coltorti, M.: Volcanic gases vs. mantle fluids: clues from mineral-hosted fluid inclusions in ultramafic xenoliths from Mayotte island (Comoros archipelago, Indian Ocean), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8395, https://doi.org/10.5194/egusphere-egu25-8395, 2025.

Continental mantle represents one of Earth’s most ancient and long-lived chemical reservoirs. It plays a crucial role in the global cycling of volatile elements—such as C, H, S, F  and Cl —because of its unique ability to both sequester volatiles via metasomatism and release them to the atmosphere during volcanism (Gibson and McKenzie, 2023).

The widespread generation of deep-sourced, volatile-rich melts is borne out by global maps of magmas rich in CO₂, H₂O, S and F (e.g. kimberlites, lamproites and carbonatites). Moreover, mantle xenoliths preserve evidence of repeated episodes of pervasive, reactive percolation and stalling of these volatile-rich melts. High-precision analyses of volatile elements in the abundant nominally-volatile-free mantle minerals and accessory phases, together with analyses of volatiles of intraplate magmas, allow quantification of the storage of volatile elements in the lithospheric mantle.

Recent advances in global tomography, particularly multi-mode surface wave analysis, have significantly refined estimates of lithospheric thickness. These improvements enable more reliable calculations of lithospheric mantle volume across different geodynamic environments, including cratonic regions, continental off-craton areas and oceanic domains. The results indicate that the most significant global volatile reservoir resides within the mantle beneath ancient cratons. This is primarily due to their large volume and the elevated volatile concentrations preserved within their stable ‘roots’. Our new thermal models show that the outer ~ 50 km of craton margins is especially susceptible to devolatilisation during rifting and heating events (Gibson et al., 2024b). The thermal stability of craton interiors, however, ensures these regions have acted as long-term volatile sinks for at least the past 2.5 billion years. The volatile budget of off-craton lithospheric mantle is more dynamic. Volatiles stored in these regions may have significantly shorter residence times and can be rapidly remobilized through rifting and heating events. As a result, off-craton lithospheric mantle can transition from a volatile ‘sink’ to a ‘source’ over relatively short geological timescales, potentially within a few million years.

The ultimate source of volatiles stored in the continental mantle is challenging to decipher but ³He/⁴He exhibits a systematic behaviour with melt depletion in mantle peridotites and deviations from this global trend may be correlated with subduction events (Gibson et al., 2024a). The dynamic nature of volatile storage and release within Earth's lower lithospheric ‘lid’ underscores the need for continued refinement of mantle volatile estimates to improve our understanding of deep volatile cycling.

Gibson, S. A., Crosby, J. C., Day, J. A. F., Stuart, F. M., DiNicola, L. & Riley, T. R. (2024a). Systematic behaviour of ³He/⁴He in Earth’s continental mantle. Geochimica et Cosmochimica Acta 384, 44–64.

Gibson, S. A. & McKenzie, D. (2023). On the role of the lithospheric mantle in global volatile cycles. Earth and Planetary Science Letters 602, 117946.

Gibson, S., McKenzie, D. & Lebedev, S. (2024b). The distribution and generation of carbonatites. Geology 52, 667–671.

How to cite: Gibson, S., McKenzie, D., and Lebedev, S.: The dynamic role of Earth's continental mantle in ‘deep time’ volatile cycles , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8582, https://doi.org/10.5194/egusphere-egu25-8582, 2025.

This study investigates the potential of hydroseismograms for seismic monitoring and understanding earthquake physics, utilizing high-frequency pore pressure measurements within the Gran Sasso Aquifer (GSA) in central Italy. Hydroseismograms, obtained from a hydraulic pressure device (HPD) installed in deep, horizontal wells intersecting a major fault network within the GSA, are compared with seismic records from the nearby GIGS station to assess the HPD's earthquake detection capabilities. This unique setting, combined with the HPD's high-frequency (20 Hz) data acquisition system, offers a sensitive method for monitoring both seismic activity and pore pressure anomalies. The GSA’s fractured-karst geology and its location within a high seismic hazard zone in Italy, along with the presence of the Italian Institute of Nuclear Physics (INFN) underground laboratory (UL), create an ideal environment for studying deep, saturated aquifer-earthquake interactions, minimizing interference from shallow hydrological processes. The UL houses two horizontal boreholes, named S13 (190 m) and S14 (175 m), equipped with the HPD. Approximately 250 meters from S13, the INGV seismic station GIGS, part of the GINGER experiment, uses two broadband seismometers for continuous microseismic monitoring and global seismicity recording. The research analyzes long-term, high-frequency pore pressure data from the GSA, aiming to further understand the complex relationship between groundwater and seismic activity. The primary objective of the joint analysis of well and seismic data, spanning from May 1, 2015, to December 31, 2023 (with ongoing monitoring), is to identify and correlate earthquake occurrence with hydraulic pressure variations detected by the HPDs in S13 and S14. A statistical inferential approach was used to evaluate HPD sensitivity, comparing the number of HPD-detected events with those recorded by GIGS (1068 events) across different magnitudes and epicentral distances. Statistical analysis demonstrates the HPD’s significantly enhanced sensitivity compared to previous studies. The HPD detected 148 of the 1068 events recorded by GIGS (a 13.9% overall success rate), with this detection probability strongly influenced by earthquake magnitude and epicentral distance. Mainly for far events, the identified detection threshold significantly exceeds the “hard” detection limit for typical aquifers defined by Montgomery and Manga (2003) based on the Dobrovolski et al. (1979) criterion, a limit below which they found no detections in a large dataset.

This finding warrants further investigation into the not yet fully understood mechanisms of hydroseismic detection. This study, covering data from May 2015 to December 2023, reveals the potential of HPDs installed in carbonate rock boreholes for seismic monitoring. The GSA hydrogeological and seismotectonic conditions provide an optimal environment for HPD deployment for both medium-to-long-term and high-frequency pore pressure monitoring. The strategic borehole locations intersecting the main fault network offer a unique opportunity to study the complex interplay between hydrological processes and seismic activity. Ongoing HPD monitoring will further explore their potential as a valuable tool for future seismic studies and contribute to the advancement of earthquake science, with implications for seismic hazard assessment and early warning systems.

References

Montgomery, D. R., & Manga, M. 2003. Streamflow and water well responses to earthquakes. Science, 300(5628), 2047-2049.

How to cite: Guerriero, V., Isaya, D., De Luca, G., Di Carlo, G., Martorana, R., and Tallini, M.: Earthquake Hydrology and seismic detection capability of deep pressure devices within the Gran Sasso aquifer (central Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12391, https://doi.org/10.5194/egusphere-egu25-12391, 2025.

Hydrothermal alteration and geofluid transport in magmatic systems plays a crucial role in the development of ore deposits, the systematics of geothermal resources and the structural stability of volcanic edifices. Characterising the type, intensity and distribution of alteration associated with geofluid pathways is therefore critical to understanding how essential resources form. However, alteration is routinely classified on the basis of highly subjective evaluations made by individual geologists or on single semi-quantitative datasets such as hyperspectral core analysis. Similarly, the role of alteration in controlling the distribution of strain is poorly constrained within magmatic systems. This study adopts a semi-quantitative approach to characterising hydrothermal fluid alteration using a novel combination of hyperspectral and magnetic analysis to efficiently characterise the silicate, oxide and sulphide mineralogy of a hydrothermally altered granitoid shear zone and its impact on strain development.

The monzodioritic Fand Pluton, NW Ireland, is a late Caledonian intrusion crosscut by a NE-SW shear zone in its eastern periphery. Field observations across the ≈10m wide shear zone show partitioned strain development, with ≈0.5m wide bands of heavily sheared and foliated granite interspersed between regions of strongly altered yet relatively undeformed granite. Alteration systematically intensifies toward the core of the shear zone, from a partial alteration of the host intrusion to a complete destruction of original rock texture.

Lab analysis aims to quantitatively evaluate the type and intensity of alteration across the shear zone and evaluate if zones of high strain systematically map to zones of high or low alteration. Hyperspectral reflectance data were collected using airborne multispectral and handheld hyperspectral instruments to characterise hydrous mineral phase assemblages within each alteration type. Magnetic characterisation experiments including hysteresis, first order reversal curves and temperature dependent susceptibility were combined to characterise the ferromagnetic mineral assemblage.  Anisotropy of magnetic susceptibility and anhysteretic remanent magnetisation were measured to determine the distribution of strain across the shear zone, evaluating the role of alteration intensity in the observed partitioning of strain.

Our results outline a multi-disciplinary method of mapping late-stage fluid transport within igneous intrusions, identifying pathfinder signatures and fabric parameters, linking them to alteration intensity from distance from fluid pathways.

How to cite: Latimer, B., McCarthy, W., Mattsson, T., and Reavy, J.: Tracing Late-Stage Fluid Migration within Intrusions via Magnetic and Spectral Characterisation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13892, https://doi.org/10.5194/egusphere-egu25-13892, 2025.

This study investigates the mineral chemistry of olivine, orthopyroxene, clinopyroxene, and chromite phases from the Wadi Zikt high Al-chromitite within the Khor Fakkan massif of the UAE ophiolites. The ophiolites, part of the well-preserved Semail ophiolite complex, represent mantle sections formed in a supra-subduction zone (SSZ) environment. Detailed analyses reveal that the olivine exhibits high forsterite contents (Fo > 90), elevated NiO concentrations (up to 0.6 wt%), and low MnO (< 0.2 wt%), indicating significant partial melting under hydrous conditions. Orthopyroxenes display high Mg# (> 90), low Al₂O₃ (< 1.2 wt%), and elevated Cr₂O₃ (up to 0.62 wt%) contents, consistent with residues of extensive melt extraction. Clinopyroxenes are characterized by high Mg# and low TiO₂, Al₂O₃, Dy, and Yb contents suggesting a forearc setting. Chromite analyses show high Cr# (51–67), low TiO₂ (< 0.8 wt%), and low Ga/Fe³_# ratio, reinforcing a fore-arc origin. The studied chromites are analogues to those of the fore-arc peridotite, indicating high degrees of partial melting (25–35%). The geochemical signatures of the studied phases, including low Ti, high Cr#, and high Mg#, suggest that the Wadi Zikt chromitite formed in a depleted mantle wedge influenced by subduction-derived fluids and boninitic melts during the early stages of subduction initiation. These findings provide critical insights into mantle wedge processes, arc magma genesis, and ophiolite formation in SSZ settings. This study underscores the significance of the Wadi Zikt chromitite as a key example of SSZ mantle dynamics and melt evolution, contributing to the broader understanding of ophiolite complexes worldwide.

How to cite: Sami, M., Mahmoud, B., Zhao, X., El-Awady, A., Ntaflos, T., Abart, R., and Fathy, D.: Petrogenetic and tectonic interpretation of Wadi Zikt Chromitite, Khor Fakkan block, United Arab Emirates: Evidence from major and trace mineral chemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16196, https://doi.org/10.5194/egusphere-egu25-16196, 2025.

Carbonatites are spatially and temporally associated with Large Igneous Provinces (LIPs) such as the Siberian traps, the Paraná-Etendeka and the Deccan traps. Carbonatites, and the associated alkaline rocks, can both predate and postdate the main tholeiitic volcanism. For example, the Sarnu Dandali complex (68.57±0.08 Ma) and the Mundwara complex (68.53±0.16 Ma), both characterized by high 3He/4He, predate the Deccan traps, whereas the 65±0.3 Ma carbonatites in the Narmada Rift postdate it. Similarly, carbonatites from the Amambay alkaline province (Eastern Paraguay) predate the Paraná-Etendeka LIP by several million of years, whereas the Jacupiranga carbonatites (130 Ma) in South America and the Damaraland carbonatites (129-123 Ma) in Namibia postdate the main tholeiitic pulse (134-132 Ma).

The origin of carbonatites remains a matter of debate, albeit radiogenic isotope ratios, trace element variations and primordial noble gases from most carbonatites support a plume origin. For carbonatites predating LIPs, a generally accepted model invokes partial melting of carbonate-metasomatized lithospheric mantle, heated by the plume. The implicit assumption is that heat, slowly diffused from the plume, can reach the lithosphere before buoyant melts from the plume itself, which is not obviously plausible.

Our 3D-numerical simulations of a mantle plume with millions of carbon- carrying tracers enable us to calculate the depth at which carbon-rich fluids form. These fluids, because of their physical properties, are highly mobile and separate from the solid matrix even at low melt fractions. At each time-step we calculate their ascent velocity (i.e., a linear combination of the solid matrix velocity and of the separation velocity) and their 3D-trajectories. We span a range of carbon concentrations in the plume source (196 ≤ C ≤ 440 ppm), and we explore different depths of redox melting and P-T conditions for the solidus of carbonated peridotite.

We find that, if mantle redox conditions allow for deep (>200 km) carbon-rich melting, then the fast rising carbonatitic fluids can reach the lithosphere 2-3 Myr before the onset of anhydrous peridotite melting. This key result reveals the existence of a precursory carbon flux (of order 10e+12 - 10e+13 mol/yr) across the base of the lithosphere (i.e., 140 km depth). When melting of anhydrous peridotite starts in the plume head, a total mass of 10e+16 kg C has already reached the lithosphere. This precursory carbon flux provides a new framework to interpret carbonatite complexes predating the earliest LIP's volcanism.

We also find that the radial extent of the zone permeated by carbon-rich fluids is much broader than the zone undergoing anhydrous peridotite melting. These vast lithospheric domains, fertilized during several millions of years by plume-derived carbon-rich fluids might be mobilized by peripheral tholeiitic magmas. Possibly, this scenario could explain the occurrence of carbonatites that postdate LIP's emplacement, but which carry a distinctive plume-like geochemical fingerprint (e.g., the high 129Xe/130Xe of the Jacupiranga carbonatites).

How to cite: Farnetani, C. G. and Richards, M. A.: The origin of carbonatite magmas predating main-phase LIPs eruptions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16266, https://doi.org/10.5194/egusphere-egu25-16266, 2025.

Geochemical anomalies are widely recognized as potential precursors to earthquakes. Recent studies on precursor signals and phenomena of the seismic process have demonstrated that significant transients in geochemical parameters may occur prior to moderate-to-high magnitude earthquakes (Magnitude > 4). Among the geochemical processes investigated, notable variations have been observed in the ion concentrations  and dissolved gases in groundwater, as well as in the composition of crustal and mantle-derived gases emanating from soils.

Soil gas anomalies, particularly diffuse degassing of CO₂, serve as critical indicators for identifying fault zones due to their strong correlation with increased crustal permeability in the fault zones. Temporal variations in the degassing rate are modulated by changes in crustal stress preceding or accompanying seismic events. Hydrogen, in particular, has emerged as a promising indicator of seismic activity. Observations have revealed that hydrogen anomalies in soil gas decrease with increasing distance from the seismic source and occur both prior to and during earthquakes. The existing literature suggests that hydrogen is produced in the crust through water-rock interactions, generating concentration anomalies that can exceed four orders of magnitude relative to atmospheric hydrogen.

This study outlines the implementation of a monitoring network designed to measure soil CO₂ flux, hydrogen concentrations in soil gas, and selected atmospheric variables (e.g., temperature, pressure, rainfall, wind speed, and wind direction) that may influence the emissions of soil gases. The network consists of four stations strategically deployed near the Matese-Irpinia region, an active seismic zone in the southern Apennine chain, Italy. This area hosts several active fault systems where earthquakes with magnitudes > 3.0 have been recorded over the past two decades. The region is characterized by normal faulting and shallow hypocentral depths (less than 15 km). Notably, the Monti del Matese area has experienced several prolonged seismic swarms, including more than 250 earthquakes within a month during 2013, culminating in a moderate-magnitude event (ML 4.9) on December 29, 2013.

Measurements are collected hourly and telemetered to the INGV in Palermo. An automated software platform, adapted from a pre-existing gas hazard monitoring system, has been optimized for the specific objectives of this study. This platform (Gas Net Analytics), which has several tools for the automated analysis of the geochemical data, adopts high standard for data management, including security. It facilitates automatic statistical analysis and visualization of the data, ensuring low latency in delivering the geochemical information.

The implementation of the monitoring network aims to characterize hydrogen concentrations and CO₂ flux as potential tracers of the local response to regional variations in crustal stress field which is associated with the seismic processes. The data collected on H₂ and CO₂ are further utilized to refine physical-mathematical models of gas transfer through crustal rocks. These models incorporate mechanisms of advective and diffusive gas transport through porous media, enabling the interpretation of diffuse degassing variations in the context of crustal stress dynamics. The integration of geochemical monitoring and modelling offers a robust framework for elucidating the relationship between soil gas anomalies and seismic activity, thereby advancing our understanding of earthquake precursors.

How to cite: Francofonte, V., Di Martino, R. M. R., Gurrieri, S., Mastrolia, A., and Altavilla, F.: Geochemical anomalies in the soil gases as potential precursors to seismic events: a case study in the Appennines, souther Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16410, https://doi.org/10.5194/egusphere-egu25-16410, 2025.

Knowledge of plumbing systems architecture and dynamics has increased in recent years. However, while the mid- to shallow-crustal regions are well-explored, the deepest parts of plumbing systems remain poorly understood. The Middle Triassic magmatic event in the Dolomites (Southern Alps; Italy) provides an exceptional opportunity to study all sections of ancient plumbing systems, owing to the excellent exposure and preservation of different magmatic lithologies representing various magma storage levels. Here, we present detailed textural and compositional analyses of ultramafic xenoliths embedded in mafic volcanic breccia from a diatreme outcropping in the Triassic Latemar carbonate platform (Zan de Montagna locality; 2576 m.a.s.l.). Ultramafic nodules have cumulate equigranular to inequigranular texture and are mainly clinopyroxenites, with subordinated wehrlites and websterites. Clinopyroxene goes up to 3 mm in size in all samples, while olivine in the wehrlite samples attains sizes of up to 1.5 mm. Clinopyroxene is diopsidic in composition (Wo_45-49 En_42-48 Fs_4-10) with Mg# [MgO/(MgO+FeOtot) mol%] of 82-93 and CaO, TiO₂, Cr₂O₃ and Al₂O₃ contents in the range of 22-24 wt%, 0.1-1.2 wt%, 0-0.7 wt% and 0.9-5.5 wt% respectively. Olivine has Fo contents between 84 and 89 and NiO concentration from 0.10 to 0.15 wt%. Notably, more primitive olivine can be found in the host lava, where crystals reach Fo₉₂ and NiO content of 0.4 wt%. Orthopyroxene in the websterite is <1 mm in size and has enstatite (Wo_1-4 En_76-79 Fs_17-23) composition, with Mg# values ranging from 77 to 82 and Al₂O₃ contents between 1.1 wt% and 1.8 wt%. Spinel is ubiquitous, occurring as chromite, magnetite and Ti-magnetite (Cr₂O₃=0.1-45.5 wt%; TiO₂=0.8-16.7 wt%; FeO_tot=29.0-81.0 wt%).

Overall, these xenoliths show compositional similarities with clinopyroxenitic nodules already reported in other localities of the Latemar platform (Nardini et al., 2024) and differ only for the wehrlite presence.

These new data represent an advancement in tracking back to the early stages of the liquid line of descent of the Middle Triassic magmas and help to reconstruct the deepest portion of the plumbing system of these ancient volcanoes. Moreover, the composition of clinopyroxene hosted by these nodules brings another piece of evidence about the source of the high-Mg# and high-Cr diopsidic antecrystic cores in the trachy-basaltic effusive rocks associated with this magmatism (Nardini et al., 2024).

Reference

Nardini, N., Casetta, F., Petrone, C.M., Buret, Y., Ntaflos, T., Coltorti, M., 2024. Modelling ancient magma plumbing systems through clinopyroxene populations: a case study from Middle Triassic volcanics (Dolomites, Italy). Contrib. Mineral. Petrol. 179, 22.

How to cite: Nardini, N., Casetta, F., Ntaflos, T., and Coltorti, M.: Exploring the roots of a plumbing system: insights from ultramafic xenoliths ejected during the Middle Triassic magmatic event in the Dolomites (Southern Alps; Italy)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17535, https://doi.org/10.5194/egusphere-egu25-17535, 2025.

The Mefite d’Ansanto is the largest non-volcanic low temperature CO₂ natural emission on the Earth (Di Luccio et al., 2023). It is located in the Southern Apennines, about 25 km away from the northern tip of the seismogenic structures of the November 23, 1980 M_S = 6.9 earthquake. The main gas emissions manifest in a roughly circular depression with about 100 m of diameter, whose centre is characterized by bubbling mud. The emissions of CO₂, likely of mantle origin, are probably fed by the reservoir found at Mt. Forcuso 1 well (Chiodini et al., 2010), located approximately 2 km east of Mefite area. In the framework of the Strategic INGV FURTHER Project, on 29 September 2020 a local seismic network was installed to investigate on the possible links between the fluid movements at depth and the seismicity of the area surrounding the CO₂ emission site (Cusano et al., 2021; Morabito et al., 2023). With the aim of obtaining information on how large the emission area is and on its sub-surficial structure, we investigated the crustal structure beneath Mefite d’Ansanto and the surrounding area analysing the waveforms of teleseismic events. We selected deep and intermediate earthquakes that have impulsive onset, epicentral distance ∆ ≤ 90° and magnitude M ≥ 6.0. The seismic traces are those recorded by MEFA, a temporary seismic station installed at Mefite d’Ansanto, and by CAFE, SNAL and RFS3, permanent seismic stations belonging to the INGV National Seismic Networks. We, first, utilized cross-correlation technique to check the similarities among the waveforms (Milano et al., 2023). Successively, we computed synthetic seismograms to obtain the best fit with the recorded seismograms. The synthetic seismograms were computed by means of QSEIS6 software (Wang, 1999), fixing a starting velocity model extracted from that IASPEI91 (www.iris.edu). Successively, we perturbed it beneath the study area taking also into account the upper crustal structure recently retrieved for the Irpinia region (e.g., Feriozzi et al., 2024). The cross-correlation analysis had already revealed some particularities in the waveforms suggesting similarities in the uppermost crust beneath MEFA and RSF3 stations, approximatively 2.5 Km apart. The first results from the synthetic seismograms evidence that the phase with the on-set in the range 4.5-5 s from the first arrival at each stations, is compatible with the P-to-S converted phase at Moho discontinuity.

Chiodini et al., 2010, Geophys. Res. Lett., 37, L11303.

Cusano et al., 2021, https://doi.org/10.5194/egusphere-egu21-10625.

Di Luccio et al., 2022, https://doi.org/10.1016/j.earscirev.2022.104236.

Feriozzi et al., 2024, https://doi.org/10.1029/2023TC008056.

Milano et al., 2023, https://doi.org/10.4430/bgo00416.

Morabito et al., 2023, https://doi.org/10.3390/s23031630.

Wang, 1999, Bulletin of the Seismological Society of America, 89(3), 733-741.

How to cite: Milano, G., Morabito, S., Cusano, P., and Gervasi, A.: Mefite d’Ansanto CO2 emission area (Southern Apennines, Italy):  first results on the uppermost crustal structure from teleseismic data., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19823, https://doi.org/10.5194/egusphere-egu25-19823, 2025.

Fluid injection activities cause pore pressure perturbations within the reservoir's rocks, which can potentially trigger fractures, faults failures, and alter the elastic properties of the surrounding rocks. Thus, monitoring stress conditions of the reservoir medium and the evolution of pore pressure around wells, is crucial for hazard assessment in injection areas.

We present a rock physics-based approach using induced micro-seismicity to track pore pressure temporal evolution from  Vp/Vs ratio variations. Additionally, focal mechanisms analysis (BISTROP, De Matteis et al., 2016; TESLA, Adinolfi et al. 2023) of microearthquakes revealed insights into local stress patterns within the host rocks, in relation to induced seismicity.

The method was applied to wastewater disposal-induced micro-seismicity detected near of the Costa Molina 2 injection well (High Agri Valley, Southern Italy) in the Val d’Agri oilfield, the largest onshore oil and gas field in Western Europe. We used as dataset the enhanced seismic catalogue obtained in the Costa Molina area by Stabile et al. 2021. It comprises 196 induced micro-earthquakes, occurred between 2016 and 2018 around the injection well. The catalogue has events magnitudes ranging between − 1.2 ≤ Ml ≤ 1.2.

Accurate arrival time measurements are essential for calculating the Vp/Vs ratio using the Wadati method. Therefore, we first refined the first P- and S-wave arrival times using waveform cross-correlation and hierarchical clustering method. Then, the Vp/Vs ratio was estimated for each source-station pair and averaged across events at the four nearest stations to the well. This allowed us to track the temporal evolution of elastic properties in the well’s surrounding region and compare it with injection parameters (i.e., injection volume and pressure). Our findings show that variations in the Vp/Vs ratio, especially for the station closest to the reservoir, closely correlate with injection parameters.

Additionally, the obtained focal mechanisms reveal strongly contrasting behaviors, ranging from strike-slip to reverse faulting. For the latter events, we identified highly anti-correlated seismic waveforms. The presence of anti-repeaters, as described by Cesca et al., 2024, has been observed in various settings and is often associated with transient stress perturbations. Since many of these phenomena have been attributed to fluid migration processes, they could provide valuable insights into subsurface fluid movements and help track their dynamics over time.

These findings demonstrate the potential of integrating accurate locations, seismic velocity monitoring and focal mechanism analysis to enhance reservoir monitoring systems. This method improves understanding of induced seismicity and offers a valuable tool for risk assessment and fluid injection management, applicable to various reservoir contexts.

References:

De Matteis R, Convertito V, Zollo A. 2016. Bayesian inversion of spectral-level ratios and P-wave polarities for focal mechanism determination. Seismol Res Lett. 87:944–954. https://doi.org/10.1785/0220150259.

Adinolfi G.M., Convertito V, De Matteis R. 2023. TESLA, A Tool for Automatic Earthquake Low‐Frequency Spectral Level Estimation: The Study of 2013 St. Gallen Earthquake Fault‐Plane Solutions. Seism ReS Lett.  94 (5): 2441–2455. https://doi.org/10.1785/0220230033

Stabile, T.A., Vlček, J., Wcisło, M. et al. Analysis of the 2016–2018 fluid-injection induced seismicity in the High Agri Valley (Southern Italy) from improved detections using template matching. Sci Rep 11, 20630 (2021). https://doi.org/10.1038/s41598-021-00047-6

Cesca, S., Niemz, P., Dahm, T. et al. Anti-repeating earthquakes and how to explain them. Commun Earth Environ 5, 158 (2024). https://doi.org/10.1038/s43247-024-01290-1

How to cite: Panebianco, S., De Landro, G., Muzellec, T., Adinolfi, G. M., Serlenga, V., and Stabile, T. A.: Tracking fluid-induced seismicity: integrating Vp/Vs ratio variations and focal mechanism analysis for reservoir monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20133, https://doi.org/10.5194/egusphere-egu25-20133, 2025.

Cenozoic volcanic rocks occurring in Devès volcanic field (3.5 – 0.5 Ma) in the southern mantle domain of the French Massif Central (FMC) carry abundant peridotite xenoliths sampling Continental Lithospheric Mantle (CLM) [1, 2]. CLM in this area is fertile and might have formed due to 1) extraction of small amounts of partial melt(s) from mantle, and/or 2) refertilization of depleted mantle by asthenosphere-derived melts [1, 2]. We present mineral data for peridotites from several xenolith localities at Devès, in order to shed new light on the problem and document regional-scale CLM variability. Here, we complement the existing set of mineral chemical data from Allègre [2], Mt. Coupet [3] and Mt. Briançon [4] with a new data set on peridotitic xenoliths from Allègre volcano.

Peridotite xenoliths from Allègre (n = 16) are represented mostly by fine- to medium-granular lherzolites. Forsterite in olivine varies from 89.34 to 91.42%. The Mg# and Al content in orthopyroxene are: 0.89 – 0.92 and 0.06 – 0.22 apfu, respectively. In clinopyroxene, Mg# is 0.88 – 0.93 and Al content is 0.03 – 0.32 apfu. In spinel, Cr# and Mg# are: 0.09 – 0.50 and 0.63 – 0.76, respectively. Three major groups are recognized based on clinopyroxene REE patterns: (A) LREE-depleted, (B) LREE-enriched and (C) moderately LREE-enriched (spoon-shaped). However, two samples are characterized by significantly higher Cr# (0.38 – 0.50), lower Mg# (0.63 – 0.68) in spinel and lower Al in Opx and Cpx (0.06 – 0.13 and 0.03 – 0.20 apfu, respectively), along with strong LREE-enrichment and were classified as group D.

The mineral major element compositions for peridotite xenoliths from Allègre resemble those from other xenolith suites at Devès [2, 3, 4]. The only difference is recognized in the composition of spinel, which in peridotites from Allègre has higher Cr# (higher by up to ~0.20) and lower Mg# (~0.05) than that from other Devès localities (including previous data from Allègre [2]). Moreover, the trace element composition of pyroxenes is very similar in all three localities. Therefore, we assume that Allègre peridotites share an evolution with peridotites from other Devès localities. They record multi-stage metasomatism, including reaction with MORB-like melt (group A) and overprint by percolating alkaline melts (group B), additionally documented by transitional lithologies (group C).  On the other hand, the chemical composition of group D peridotites, which are more refractory but more strongly incompatible element-enriched, suggests the existence of mantle domains, which were not affected by MORB-like metasomatism observed in group A. Thus, despite the generally fertile composition of peridotites typical for the southern FMC mantle domain [1, 2], isolated relic pockets of more refractory material persist in the CLM, offering the rare opportunity to unravel regional CLM evolution prior to pervasive refertilization.

Funding. We gratefully acknowledge funding by the project of Polish National Centre of Research 2021/41/B/ST10/00900 to JP.

[1] Lenoir et al. (2000). EPSL 181, 359-375.

[2] Puziewicz et al. (2020). Lithos 362–363, 105467.

[3] Mazurek et al. (2024). Abstract EGU24-8658

[4] Ziobro-Mikrut et al. (2024). Lithos 482-483, 107670.

How to cite: Matusiak-Małek, M., Mazurek, H., Puziewicz, J., Aulbach, S., and Ntaflos, T.: Multi-stage evolution of Continental Lithospheric Mantle beneath Devès volcanic field (Massif Central, France): an example from Allègre xenolith suite, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20279, https://doi.org/10.5194/egusphere-egu25-20279, 2025.

The polychronous Mundwara alkaline complex displays a range in ⁴⁰Ar-³⁹Ar ages between 68.5-110 Ma. It has been previously correlated to three distinct tectonomagmatic events: (i) the Deccan Large igneous Province associated with the Reunion plume, (ii) Indo-Madagascar breakup triggered by the Marion plume, and (iii) Rajmahal-Sylhet Traps linked to the Kerguelen plume. However, the age of carbonatites from the Mundwara complex was previously unknown and based on apatite U-Pb dating is now constrained at 100 ± 20 Ma. To further our understanding of carbonatite magmatism at Mundwara, this age is supplemented with petrographic observations, bulk-carbonate carbon and oxygen isotope analyses and in-situ determinations of trace element contents and Sr-Pb isotopic ratios for calcite and apatite. The Mundwara carbonatites consist of calcite cumulates and accessory apatite, pyrochlore, albite, orthoclase, Fe-oxides, and biotite. A range of REE-bearing phases is also present, including bastnaesite, parisite, and monazite. Cumulitic and seriate texture and high Sr contents (>1 wt%) attest to the primary igneous nature of the calcites. The apatites are magmatic, as demonstrated by their euhedral shape, low Sr content, and chondrite-normalized REE patterns, distinguishing them from typical hydrothermal apatite elsewhere. The apatite grains yield a weighted mean ⁸⁷Sr/⁸⁶Sr of 0.70447 ± 0.00003 (n = 24), indistinguishable from those of the carbonates analyzed in the same samples (⁸⁷Sr/⁸⁶Sr = 0.70446 ± 0.00001; n = 54). Lead (²⁰⁶Pb/²⁰⁷Pb = 0.820- 0.289; ²⁰⁶Pb/²⁰⁴Pb = 18.53-19.20) and Sr isotopic compositions of the calcites are broadly intermediate between enriched mantle (EM) and HIMU (high 238U/204Pb) compositions and signal a source that experienced geochemical enrichment by either metasomatism or addition of subducted material. The bulk- carbonate δ13C and δ18O data of the Mundwara carbonatites have a narrow range from -6.2‰ to -6.8‰ and from +6.3‰ to +7.3‰ respectively, showing typical mantle values and excludes significant contamination or post-magmatic alteration as well as contribution by subducted carbon. The mid-Cretaceous U-Pb age of the magmatic apatite overlaps with both the pre-breakup of the Indo-Madagascar event at ~88 Ma and the Kerguelen plume-induced magmatism (117 Ma) in the north-eastern parts of the Indian shield. Although this magmatic event cannot be assigned to a specific tectonic episode, this new temporal constraint and previously reported ages for other alkaline rocks from north-western India ascertains a pre-Deccan alkaline magmatic flare-up in this region.

How to cite: Bhunia, S., Rao, N. V. C., Giuliani, A., Tavazzani, L., Talukdar, D., Pandey, R., Kumar, A., Ansari, S., and Lehmann, B.: Apatite-calcite U-Pb geochronology, trace element and C-O-Sr-Pb isotope geochemistry from the polychronous Mundwara alkaline complex: New evidence of mid-Cretaceous Pre-Deccan carbonatite magmatism in northwestern India., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-216, https://doi.org/10.5194/egusphere-egu25-216, 2025.

Chhotanagpur Gneissic Complex (CGC) is a part of the E-W trending Central Indian Tectonic Zone (CITZ), India. The CITZ is a major intercontinental suture which separates the northern Indian and the southern Indian blocks whose subduction polarity is a contentious issue. We present petrography, mineral chemistry, bulk rock geochemistry, Lu-Hf, Re-Os and Pb-Pb isotopes of the Neoproterozic lamprophyre from Simdega. The studied lamprophyre is an unmetamorphosed and undeformed that exhibits a strong porphyritic-panidiomorphic texture imparted by the megacrysts/phenocrysts of mica and amphibole with feldspar, apatite, titanite, zircon and opaques confined to the groundmass. Our lamprophyre shows shoshonitic affinities and is classified to be of calc-alkaline variety (minette). The Mg# values (ranging from 70.7 to 78.2) indicate a primitive melt character while the trace element ratios are consistent with those of subduction-related rocks globally as well as with the calc-alkaline lamprophyres from the Eastern Dharwar Craton (southern India) that suggest no crustal contamination. Our findings demonstrate that the western part of the CGC was less affected by the M3 regional amphibolite-grade metamorphic event (ca. 920-880 Ma) compared to the eastern part. Our study also supports geodynamic models proposing northward subduction of the Southern Indian block beneath the Northern Indian block synchronous to the Rodinia assembly. Scanning Electron Microscopy (SEM) helped to identify some of the mineral phases occurring as inclusions in zircons having abnormally higher Thorium (Th) and Silver (Ag) concentrations.

How to cite: Kumar, D., Chalapathi Rao, N. V., and Belyatsky, B. V.: Neoproterozoic (942 Ma) calc-alkaline magmatism from Simdega, Chhotanagpur Gneissic Complex and their mineralisation aspects, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-519, https://doi.org/10.5194/egusphere-egu25-519, 2025.

This study presents a detailed investigation of the field relationships, geochronology, mineral-whole rock geochemistry, and isotope systematics (Sr-Nd-Pb-Os-C-O) of a newly identified carbonatite-alkaline syenite intrusive system from the Gundlupete area, located near the tectonic boundary between the Western Dharwar Craton (WDC) and the Granulite Terrain of South India. The carbonatite intrudes the syenite and is exposed along an E-W to ENE-WSW trending splay of the Moyar shear zone near the southern margin of the WDC. In-situ U-Pb dating of titanite and monazite provides crystallization ages of 2590 ± 42 Ma and 2474 ± 27 Ma for the syenite and carbonatite, respectively, indicating two distinct magmatic episodes with independent petrogenetic histories. The syenite comprises alkali feldspar (Or_93.7-100), albite (Ab_98-99), clinopyroxene (Di_{22.08–65.68} Hd_{20.04–44.65} Aeg_{13.91–44.64}), biotite (X_mg: 0.54–0.58), titanite (Al: 0.03–0.06 apfu), and quartz. Geochemically, the syenite exhibits shoshonitic characteristics (K₂O/Na_₂O: 0.9–2.42), enrichment in LILEs and LREEs, depletion in Mg, Ni, Cr, and HFSEs (Nb, Ta, Ti, Zr, Hf), and crust-like ratios such as high Th/Nb_PM (avg. 79) and low Nb/U (avg. 2.17). Initial εNd values (-1.4 to 1.0) align with the Mesoarchean Dharwar TTG suite, suggesting a derivation from evolved partial melts of TTG sources, followed by clinopyroxene-biotite dominated fractional crystallization. The carbonatite is coarse-grained and composed predominantly of calcite, apatite, magnetite, monazite, amphibole, and phlogopite. Calcite and apatite are enriched in Sr and REEs, while phlogopite is Fe-Al-rich (Fe/(Fe+Mg)>0.22), and magnetite, containing 0.39–0.81 wt.% TiO₂, follows a typical titano-magnetite evolutionary trend. Geochemically, the carbonatite shows selective enrichment in LILEs (e.g., Ba and Sr) and Th, with lower HFSE concentrations (e.g., Zr, Hf, Ti, Nb, Ta). Isotopically, the carbonatite has a narrow range of Sr (⁸⁷Sr/⁸⁶Sr_i: 0.70307–0.70321), Nd (εNd_i: -3.7 to -2.1), and Pb (²⁰⁶Pb/²⁰⁴Pb_i: 13.49–13.85, ²⁰⁷Pb/²⁰⁴Pb_i: 14.70, ²⁰⁸Pb/²⁰⁴Pb_i: 33.32–34.96), while C-O isotopes range from -10.2‰ to -9.4‰ (δ¹³C) and 7.7‰ to 10.3‰ (δ¹⁸O). These characteristics suggest a primary carbonate melt derived from chondritic to slightly enriched mantle sources, with minor crustal assimilation and extensive crystal fractionation. The syenite’s geochemical signatures, εNdi values, and Nd model ages (2.8–3.0 Ga) support a derivation from Mesoarchean TTG sources. The carbonatite’s low δ¹³C values, higher time-integrated Rb/Sr ratios, and lower Sm/Nd and U/Pb ratios reflect the influence of recycled subducted components. Field, geochronological, geochemical, and isotopic evidence links the ca. 2.59–2.47 Ga magmatic events to the Neoarchean amalgamation of the Dharwar Craton and Granulite Terrain, driven by the northward subduction of the Dharwar Ocean lithosphere beneath the WDC. We propose a tectonic model where subduction-induced magma underplating triggered syenite emplacement at 2.59 Ga, coinciding with similar arc-related magmatism in the region. The carbonatite represents a later magmatic pulse in a post-collisional setting at 2.47 Ga, utilizing pre-existing conduits during the terminal accretion phase of the Dharwar Craton and Granulite Terrain at the Archean-Proterozoic boundary.

How to cite: Pandey, R., Debnath, S., Belyatsky, B., Chew, D., Rao, N. V. C., and Singh, M. K.: Decoding Archean-Paleoproterozoic carbonatite and syenite magmatism at the Dharwar Craton-Granulite Terrain boundary, southern India: Implication for petrogenesis, source characteristics and timing of terrane subduction-accretion  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-594, https://doi.org/10.5194/egusphere-egu25-594, 2025.

The Cullinan kimberlite, also known as ‘Premier’, is located 40 km northeast of Pretoria on the Archean Kaapvaal craton, in South Africa. Dated at ca 1150 Ma, it provides a unique opportunity to explore the geochemistry and geodynamics of the deep mantle, and its interactions with the lithosphere.

This study integrates geochemistry of whole-rock and kimberlite indicator minerals with geothermobarometric evaluations to unravel the mantle components of the kimberlite magmas, and to disclose the diamond potential of the kimberlitic pulses. Major element thermobarometry on olivine, garnet, and pyroxene reveals pressure and temperature conditions of crystallization along the paleo-geotherm, as well as the correspondent mineral stability fields.

Cullinan consists of several distinct kimberlite types, four of which - Fawn, Pale Piebald, Black Transitional, and Blue - are the focus of this study. Geothermobarometric calculations demonstrates that each of these kimberlite eruptions formed under distinct chemical conditions, with three of the four types intersecting the diamond stability field. We highlight their potential to carry diamonds and we emphasize the influence of varying mantle conditions on their formation.

Preliminary geochemical classification confirms Fawn and Pale Piebald as Group I kimberlites, while Black Transitional and Blue kimberlites show evidence of contamination and metasomatic alteration, suggesting a more complex petrogenetic history. These variations in composition testify to the various mantle processes that contributed to the unicity of the Cullinan kimberlite pipe.

This study represents an advancement into the understanding of how mantle-derived melts evolve as they ascend and interact with the lithosphere. It provides critical insights into the geochemical fingerprints of the mantle and contributes to a better understanding of the dynamic processes that drive diamondiferous kimberlite formation, not only at Cullinan but also at a global scale.

How to cite: du Plessis, C., Lenhardt, N., Milani, L., Delport, J., and Phahla, T.: New Geochemical and Geodynamic Insights into the Cullinan Kimberlite, Kaapvaal Craton: Mantle Processes, Magmatic Heterogeneity, and Diamond Potential., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-596, https://doi.org/10.5194/egusphere-egu25-596, 2025.

Rifting-driven source melting and the origin of the alkaline magmatism located along the active fault segments in Southeastern Mediterranean, Türkiye

Rift-related extensive mafic magmatism was developed along the active segments of the East Anatolian zone in southeastern part of Anatolian lithosphere, since Quaternary times. These mafic and mainly basaltic rocks are widely distributed in Osmaniye - Ceyhan district and along the Karasu valley in Hatay. The mafic lavas from Toprakkale region are predominantly classified as alkaline basalts with SiO₂ and MgO contents ranging from 45.79-48.65 wt% and 7.99-8.88 wt%, respectively. Additionally, one sample is classified as basanite, with a SiO₂ content of 44.18 wt% and MgO content of 6.53 wt%.

The primitive mantle-normalized multi-element diagram exhibit enrichments in LILE relative to HFS elements, and these elemental patterns are similar to that those of OIB source but differ from OIB signature with relatively depleted LILE and HFSE contents. However, the basanite sample distinguishes itself by the enrichment in Nb, Ta, Sr, P and minor depletions in Zr, Hf contents relative to OIB source. The incompatible element ratios Nb/U (27.29-77.55), Nb/La (0.72-1.60), Zr/Ba (0.57-0.70) suggest that basaltic rocks were derived from OIB-like mantle source. The (Tb/Yb)_(N) ratios of the lava products span from 1.89 to 2.68 that separates the melting from the Garnet - Spinel ((Tb/Yb)_(N) >1.8; [1]) transition zone, accompanied with moderately to high (La/Yb)_(N) ratios (9.92-14.37). Besides, Zn/Fe ratios of basaltic rocks range between 10.40-12.41 which separates the peridotite-derived (Zn/Fe <12; [2]) and pyroxenite-derived (Zn/Fe 13-20); [2]) melts.

Rifting process has a key role in magma generation where the stretching lithosphere leads to decompression melting, collectively, all these elemental ratios strongly suggest that basaltic rocks were derived from the melting of peridotite source domains within the region significantly affected by the active fault segments.

1.Wang et al., 2002, J.Geophys.Res.vol:107, ECV 5, 1-21

2.Le Roux, et al.,2011, EPSL, vol:307, 395-408

How to cite: Önder, D. A., Kürkcüoğlu, B., Yürür, M. T., Kahraman, B., and Külahcı, G. D. D.: Rifting-driven source melting and the origin of the alkaline magmatism located along the active fault segments in Southeastern Mediterranean, Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-612, https://doi.org/10.5194/egusphere-egu25-612, 2025.

The phreatomagmatic Carnian (Upper Triassic) kimberlitic tuff deposit of the Bulkur anticline at the right side of the Lena Mouth has the most high diamond grade in Russia (to 12 crt/t). Comparison of the  thermobarometric reconstructions Ashchepkov ea 2001; Grakhanov ea., 2024) and geochemistry of pyropes (Skuzovatov et al., 2022) and presented here set of the EPMA (560), SEM (980) and LA ICP (140) analyses  from tuffs at Olenek’s duct at  Lena Mouth. Pyropes variations  0<Cr2O3<13% are similar to   (Grakhanov et al., 2024) but TiO2 are higher  to 2%.

 Chromites are  Ti -  Al rich - varieties, compared to (Biller et al., 2017). Micas from Bulkur refer to reaction of peridotite with K- rich melt (3.5-5 % FeO and Cr2O3 to 3%)  similar to range in orangeites or lamproites (Downes ea, 2006).  All   ilmenites ( MgO < 4%)   are not deep-seated. The Cr- diopsides divides to the Cr-Al rich and Fe- enriched types.

The PT diagram show 8 layers and comparing to (Ashchepkov et al., 2017) and (Grakhanov et al., 2024) show straight line P (6.5-2GPa)-Fe# (0.11-0.15) for megacrystic pyropes. The eclogitic inclined P- Fe# trend is less abundant than in previous sets. And Ca -rich layer in middle Eclogite layer 4-5 GPa chromites are Ti to 6% from 6.5-3. GPa

The Geochemistry of almost all pyropes despite on variations in REE from U to S- shaped (dunitic) and HMREE low harzburgitic and rounded lherzolitic varieties almost all show high U-Th-Nb-Ta- levels. There are extreme Zr-Hf types those with elevated Zr-Hf. Even Cr- highest pyropes reveal high HFSE. As well as Cpxs and Amphs with Nb peaks and Chrs – Ta peak. All carbonates in tuffs are magmatic showing high REE gently increasing Yb to La ~ 5000*C1. The mantle column beneath Bulkur was reacted with the HFSE -rich K-rich aillikite melt. The studied phase is late comparing to studied before. Grant RNF 24-27-00411.

Ashchepkov, I. V., Vladykin, N. V., Ivanov, A., Babushkina, S., Vavilov, M., & Medvedev, N. 2021, Ma Problems of mantle structure and compositions of various terranes of Siberian Craton. In Alkaline Rocks, Kimberlites and Carbonatites: Geochemistry and Genesis. pp. 15-48. Cham: Springer International Publishing.

Skuzovatov, S., Shatsky, V. S., Ragozin, A. L., & Smelov, A. P. 2022. The evolution of refertilized lithospheric mantle beneath the northeastern Siberian craton: Links between mantle metasomatism, thermal state and diamond potential. Geoscience Frontiers, 13(6), 101455.

Grakhanov, S. A., Goloburdina, M. N., Ivanov, A. S., & Ashchepkov, I. V. (2024). Mineralogical and petrographic characteristics of diamondiferous formations of the Bulkur anticline, Republic of Sakha (Yakutia). Regional Geology and Metallogeny, (98), 41-63.

How to cite: Ashchepkov, I., Smelov, A., Grakhanov, S., and Ivanov, A.: Bulkur phreato-magmatic diamond deposits – new incites for origin from the geochemistry and thermobarometry. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2176, https://doi.org/10.5194/egusphere-egu25-2176, 2025.

Diffusion-induced nickel isotope fractionation in pyroxenitic xenoliths

Xiao-Yang Hu, Shui-Jiong Wang

State Key Laboratory of Geological Processes and Mineral Resources, China

University of Geosciences (Beijing), Beijing 100083, China.

The bulk silicate earth has a homogenous nickel (Ni) isotopic value of +0.11±0.06‰^[1][2]. However, sizable Ni isotope fractionation could occur during mantle metasomatism and melt-rock interaction^{[1][2][3][4][5]}. Here, we analyzed the Ni isotopic composition of a pyroxenitic xenolith (~10cm in length) within Cenozoic intraplate basalts from the Hannuoba region, North China Craton. The host basalts have homogenous δ⁶⁰Ni value of -0.15±0.09‰, whereas the pyroxenitic xenolith has highly variable δ⁶⁰Ni value ranging from -0.05‰ to +0.95‰. In detail, the δ⁶⁰Ni of the pyroxenite exhibit extremely high value at one side of the basalt-pyroxenite boundary, and gradually transitioned to mantle-like δ⁶⁰Ni towards the other side of the basalt-pyroxenite boundary, leading to an stairs-like pattern instead of a U-pattern. Therefore, interaction of the pyroxenitic xenolith with the host basaltic magma after entrainment cannot account for the large Ni isotopic variation. It is likely that the ancient mantle metasomatism, during which, extensive elemental and isotopic exchange between the metasomatic agent and lithospheric mantle, has produced the diffusion-induced Ni isotope fractionation, and later ascending of the Cenozoic intraplate magmas has captured this metasomatized mantle materials, and erupted to the surface. 

References:

[1] Wang et al. (2021), Nat Comms, 12, 294; [2] Klaver et al. (2020), GCA, 268, 405-421; [3] Saunders et al. (2020), GCA, 268, 405-421; [4] Gall et al. (2017), GCA, 199, 196-209;  [5] Sheng et al. (2022), JGR-Solid Earth, 127, e2022JB02455.

How to cite: Hu, X. and Wang, S.: Diffusion-induced nickel isotope fractionation in pyroxenitic xenoliths, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3470, https://doi.org/10.5194/egusphere-egu25-3470, 2025.

The 3000 km SSW-NNE mantle transect through all Congo craton (including Angola and Congo DR) was constructed based on EPMA analyses of diamond satellite minerals (DSM) from  kimberlites (and placers) using monomineral thermobarometry (Ashchepkov et al., 2017)  and Surpher 8 software. It crosses Lucapa corridor from Kunene to Lushinga fields and goes from Mbuji-Mai and to Banalia field in Congo DR.  The NWW –SEE transect from Bas Congo to Kundelungu was built also.

The whole SW-NE profile consists of at least of 6 sections Angola part and 3 more in Congo DR part correspondently to the grouping of the kimberlites fields at the ancient mantle sub terranes. There are also heated regions with the higher concentrations of pipes correspondent to the boundaries of the sub terranes where the mantle columns are more heated and homogenized.

     Mantle sections show rather contrast layering. It is more evident and thin in P-FO2 diagram and total Fe# and less  for ToC and garnets CaO and Fe#.

      The section in Angola include several regions with the more dense  kimberlite population including Kunene, Cubango, Lubango and long array from Longo to Kamatue including Catoca cluster. The last highly diamondiferous part of mantle differ from other parts by the essential heating of the lower part of section relatively high amount of pyroxenitic and eclogitic material which probably define the high diamond grade. Several mantle clusters show heating and increase in Fe# accompanied by the low oxygen fugacity which corresponds to the high diamond grade In Angola: Cuilo – Liuele- Catoca and Camafuca Kamachia fields and in Congo DR – Mbuji- Mai and Wamba fields.

The relative homogenization beneath Catoca and close regions means more permeable mantle with concentration of proto-kimberlite magma chambers not only near the base of the lithospheric mantle, and also in intermediate and middle pyroxenite levels. The mineralogy suggests presence there and low-oxidized eclogites, dunites, and Mg-rich ilmenite-chromite-bearing metasomatites. Probably on such conditions many diamonds were growing during protokimberlite process in the large magmatic chambers near the lithosphere base where  large CLIPPIR type grains as megacrysts were growing.

The uppermost Early Archaean relatively thin plate mantle layers are inclined toward the  Catoca- Kamachia cluster in NNE  part of Congo where the concentration of eclogites are higher probably due subduction accretion.   RNF Grant 24-27-00411.

• Ashchepkov I.V., Zinchenko V.N., Ivanov A.S. Mantle Transects in Africa According to Data of Mantle Xenocrysts and Diamond Inclusions. In: Acta Geologica Sinica‐English Edition. Vol. 95(S1), pp.15-17 (2021).
• Zinchenko V., Ashchepkov I., Ivanov, A. Modelling of the mantle structure beneath the NE part of the Lucapa kimberlite corridor. Angola. In: Journal of science. Lyon, Vol.19. pp. 7-14. (2021).
• Ashchepkov I.V.; Ntaflos T., Logvinova, A.M., Spetsius, Z.V., Downes, H., Vladykin, N.V. Monomineral universal clinopyroxene and garnet barometers for peridotitic, eclogitic and basaltic systems. Geoscience Frontiers. Vol.8, pp.775-795. (2017).
• Ashchepkov I.V., Rotman A.Y., Somov S.V.et al. Composition and thermal structure of the lithospheric mantle beneath kimberlite pipes from the Catoca cluster, Angola. In: Tectonophysics. Vol. 530, pp.128-151 (2012).

RNF grant 24-27-00411.

How to cite: Zinchenko, V., Ashchepkov, I., Ivanov, A., Manuel, B. P., and Felix, J. T.: The 3000 km mantle transect through Angola and Congo based on diamond satellite minerals from kimberlites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4716, https://doi.org/10.5194/egusphere-egu25-4716, 2025.

Decades of studies have shown that the petrogenesis of kimberlite-borne cratonic eclogite and pyroxenite xenoliths reflects the endemics of their crustal protoliths and local lithosphere evolution. Detailed investigations of the origin and metasomatic history of individual eclogite xenolith suites are thus required to understand how cratonic eclogite reservoirs - and their diamond inventory - evolve in the regional tectonomagmatic context. Here, we investigate a little-studied eclogite and pyroxenite xenolith suite from the Balmoral kimberlite in the Kimberley area of the Kaapvaal craton, which, like eclogite suites in neighbouring kimberlites, likely originated as subducted Archaean oceanic crust. Detailed petrographic observations and mineral major- and trace-element analyses, combined with published data for eclogite xenoliths and eclogitic inclusions in diamond, show that this sample suite records at least two distinct episodes of metasomatic overprint: (1) Metasomatism by a kimberlite-like melt caused a decrease in clinopyroxene jadeite component and garnet grossular component and imparted high MgO and Cr₂O₃ contents, recorded dominantly by pyroxenite xenoliths. Comparison to Kaapvaal kimberlites and lamproites confirms that the geochemical trends cannot be reconciled with bulk kimberlite-eclogite mixing but require precipitation of metasomatic clinopyroxene from the melt instead. This metasomatic style is recognised world-wide, and at Balmoral is notably restricted to the shallow lithosphere (110-150 km). (2) A distinct metasomatic event generated eclogites with extreme Y-HREE enrichment, at Balmoral restricted to the deep lithosphere (150-200 km). We propose that this enrichment style reflects phlogopite formation at the expense of garnet, with the liberation of these garnet-compatible elements to the metasomatic melt. This signature is identified in eclogite xenoliths both from early Cretaceous lamproite (Bellsbank) and late Cretaceous kimberlite (Balmoral, Kimberley) localities, tentatively ascribed to interaction with melts forming the Karoo large igneous province. Balmoral corundum-bearing eclogites derive from depths overlapping eclogites showing a Karoo-type overprint, which significantly diluted the Al₂O₃ content in the bulk rock and increased silica activity as gauged by the decrease in Al[IV] in clinopyroxene, thereby destabilising corundum.

Craton-wide, preserved corundum-bearing eclogites record diamond-stable ƒO₂ and pressure conditions, yet show little compositional overlap with inclusions in eclogitic diamond. This may reflect the low propensity of COH fluids to reach carbon saturation in this lithology. The preserved corundum-bearing eclogites have reconstructed bulk major-element compositions, which, combined with small to absent Eu anomalies, suggest protoliths representing deep oceanic crustal (>0.5 GPa) cumulates of two pyroxenes plus only minor plagioclase that contained a significant melt component. The identification of such deep hybridised crustal rocks may reflect higher mantle potential temperatures and the formation of thicker oceanic crust in the Archaean.

How to cite: Pattnaik, J., Aulbach, S., Viljoen, F., Ueckermann, H., and Mxinwa, T.: The diamond-poor nature of corundum-bearing eclogite and Karoo-type overprint of deep eclogite sources beneath the Kimberley region (Kaapvaal craton), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4945, https://doi.org/10.5194/egusphere-egu25-4945, 2025.

Ilmenite is a diamond associate mineral from kimberlites and present in other ultramafic and basic alkaline rocks. In kimberlites ilmenite is common in the form of monomineral nodules-megacrysts, as well as phenocrysts in a fine-grained groundmass. The amount ilmenite-containing rocks from the total mantle xenoliths make up 4-7%, and it can be connected with proto-kimberlite melts. Ilmenite also occurs in a whole group of mantle rocks (called ilmenite hyperbasites), is presented as individual euhedral crystals, rounded grains, is also observed as inclusions in pyroxene, garnet and sometimes forms sideronite structures (intergrowths with silicates) and veinlets in a fine-grained olivine matrix.

In this work, mantle xenoliths were studied from the Mir (Mirny field) and Obnazhennaya (Kuoika field) kimberlite pipes of the Yakutian kimberlite province. These pipes are located in different parts of the Siberian craton and have different ages. The chemical composition of the ilmenite lamellaes and rounded inclusions from two pipes is discussed. A wide range of values ​​is observed for lamellae from both pipes - from 39.7 to 57.6 wt.% TiO₂. Rounded inclusions from the Obnazhennaya pipe are distinguished by narrow composition variations - 53-56 wt.% TiO₂. At the same time, they are close to megacrystalline and xenogenic (lithospheric) ilmenites from kimberlites. Large variations in the compositions of ilmenite lamellae from pyroxene and garnet crystals suggest that these ilmenites formed as disintegration and exsolution structures during gradual cooling of the initial megacrystals. Their cooling velocity and P-T final crystallization were different to reflect the difference in ilmenite compositions. Diffusion of elements from the host mineral could also affect composition variations, since the sizes of small inclusions are up to 20-40 μm. At the same time, some of the compositions of ilmenite lamellae from Mir pipe xenoliths close into the composition field of late fine-grained ilmenites of the main mass of kimberlites. This fact may indicate deep differentiation of melts enriched in iron and titanium, possibly longer processes of lithospheric mantle evolution under the Mir kimberlite pipe than under the northeast of the craton (Obnazhennaya pipe). Rounded inclusions of ilmenite in garnet and pyroxene from peridotites of the Obnazhennaya pipe have a different genesis. Their chemical compositions on the MgO-TiO₂ diagram form a compact group and are close to the region of the original, asthenospheric ilmenites. It was formed from melts, but in terms of formation time they are later than ilmenites from lamellas, which indicates a more complex history of formation and heterogeneity of the lithospheric mantle beneath the Obnazhennaya pipe.

The research was supported by Russian Science Foundation grant № 22-77-10073.

How to cite: Kalashnikova, T., Vorobey, S., and Kostrovitsky, S.: Ilmenite in peridotite and pyroxenite xenoliths from Siberian kimberlite pipes: morphology and genesis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11724, https://doi.org/10.5194/egusphere-egu25-11724, 2025.

In this paper, the evolution of the upper mantle and the formation of regions of partial melting of the asthenosphere are simulated numerically within the framework of a single-velocity multilayer hydrodynamic model that takes into account the main phase transitions. The modeling results can be used to formulate problems on the introduction of magmatic melts into the lithosphere and crust in the ocean-continent transition region. The region from the marginal sea and the ocean-continent transition zone of the northern Pacific Ocean to the rift zone was numerically studied. To formulate the numerical problem, the data on the analysis of the structure of the earth's crust and upper mantle in the ocean-continent transition region of the northwestern Pacific Ocean were used, carried out by seismic tomography methods using the GIS-ENDDB geoinformation and computing system (Mikheeva, 2016). Tomographic data made it possible to determine the regional structure of magmatic systems in the lithosphere and upper mantle of the northern Pacific Ocean. Analysis of these data, together with data on gravity and magnetic anomalies in the earth's crust, allowed us to estimate the levels and areas of transformation of the earth's crust and lithospheric mantle by past magmatic processes. The fields of shear wave velocities with vertical polarization for the areas of manifestation of PTTS for different depths of the mantle lithosphere and mantle of the northern part of the Pacific Ocean are shown in Figure 1 according to data (Schaeffer, Lebedev, 2013) in the format of the shadow model GIS-ENDDB in relative units.

Figure 1. Tomographic maps of vertically polarized shear wave anomalies for areas of PTTS manifestation at depths of 50, 100, 200, 300, 400, 500 km (according to [Schaeffer, Lebedev, 2013])

The results of the simulation of the ocean-continent transition zone and the northern part of the Pacific Ocean to the North American rift zone, calculated using a multilayer model taking into account seismic tomography data (Perepechko, Sharapov, 2014), are shown in Figure 2. The red zones indicate the melting regions that form the asthenosphere. The development of an active convective flow in the initially heterogeneous upper mantle leads to the appearance of ascending flows on the right boundary of the computational domain, corresponding to the north of the West Pacific rift belt.

Figure 2. Temperature distribution (blue) and degree of partial melting of mantle rocks (red) along the section of the northern part of the Pacific Ocean (at 47° N). The time corresponds to 72 and 149 million years after the emergence of active convective flow in the upper mantle.

Grant No. 24-27-00411.

How to cite: Perepechko, Y., Mikheeva, A., and Imomnazarov, S.: Structure of the lithosphere and upper mantle in the ocean-continent transition region of the northwestern Pacific Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11899, https://doi.org/10.5194/egusphere-egu25-11899, 2025.

It is suggested that in the genesis of the large volumes of the granites of Angara-Vitim Batholiths and similar huge granite massifs the important role play the plume magmas which were the major supply of the heart. But they also could directly participate in the magma generation providing volatiles and alkalis and other components. But of course the major melting components were granulites and lower crust gneisses.

We studied major elements and the geochemistry of the Pl- bearing pyroxenites captured by the Quaternary alkaline basalts from Baikal rift – using EPMA, SEM and LAM ICP methods from Vitim plateau, Tunka valley (Karierny volcano) (Ashchepkov et al., 2024) mainly compositions oof amphiboles, Pyroxenes, plagioclases and K-Fspars as well as micas and more rare garnets.

 Studied amphiboles mainly reveal  inclined spectra (La/Yb_n ~5-10) of pyroxenes and higher for amphiboles (~ 15 ) having higher REE and elevated LILE. Single – grain The Pls have flatter REE patterns with the peaks in Ba the K- alkali feldspars have lower REE levels and higher Ba, LILE Sr peaks. Much lower REE and higher Ba, alkalis reveal micas.

Less inclined spectra of minerals from Karierny volcano 13.5 Ma indicate a less deep of origin of the parent melts.

Thermobarometry of Vitim pyroxenites gives 5-12 kbar and for amphiboles, 8-5 kbar is somewhat shallower. In Tunka valley 10-4 kbar and 7-4 in amphiboles. This corresponds to the lower thickness of the crust in Tunka and lower garnet influence.

On the whole, amphiboles give closer TRE spectra to alkaline granitoids. But all of them have a minimum Pb, which indicates fractionation processes, and granitoids (Tsygankov et al., 2014-2017), on the contrary, have a Pb peak, which indicates partial melting. In addition, in syenites, the concave part of the HREE spectrum indicates low-temperature garnet in restites.

the Vitim Plateau imply the participation of garnet in the processes of partial melting.

The genesis of the alkaline granites and syenites (Tsygankov et al., 2014) suggest the fractional and possibly disequilibrium melting of the K -FSp and micas and partly butch melting of Ampx-Pl of the granulite and gneisses possibly in different levels as well the direct infiltration of alkaline basalt are also suggested. These magmas are more typical for the regions with the thicker crust. The major factor was the plume melts impact.

For the Ca- alkaline granitoids the batch melting is more realistic model with the higher participation of the Pl and amphiboles in magma genesis. And they corresponds to the central parts of the Transbaikal with the relatively thinner crust. These means also the more higher melting of crust material  under plume influence. Supported by RNF grant 23-17-00030

How to cite: Ashchepkov, I., Tsygankov, A., Burmakina, G., and Medvedev, N.: Trace elements in the black Pl bearing xenoliths in Quaternary basalts from Baikal rift. Implications to the origin of granites , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12237, https://doi.org/10.5194/egusphere-egu25-12237, 2025.

We present some data on Cenozoic (KZ) intraplate rocks in Baluchestan and Sistan, East Iran received by a group led by known regional trio: A. Hushmanzadeh, M.A.A. Nogol Sadate, and E. Romanko.

Some important features on intraplate and subduction-related rocks are as follows:

Rocks are mainly K-Na, middle K2O subalkaline (mainly) and alkaline ones, not very High-Ti, 87Sr/86Sr (ISr) = 0.7039+- 2 (trachyAndesite) and 0.7049+- 3 (trachyBasalt) alongside with 0.7049 of 'vulcanite' (Camp & Griffis, 1982), LREE-enrichment with a high LREE/HREE (La - more than 32 ppm), and a characteristical Eu/Eu* more than 1.1; up to high = 1/3 wt% CaO and up to a high=0.45% of Sr in basic trachyandesites (while Quaternary carbonatites are ca. 200 km to the east, Hanneshin, Afghanistan), complex correlation of some characteristical elements; then-High-Ti (rhutile, Ti-hornblende) and High-Ca phases (clinocoizite, also, Ca-rich ceolite - vayrakite is proposed), replacement of primary minerals due to a fairly strong rock-fluid interaction. North-East (submeridianal) tectonic-magmatic +- metallogenic (economic regional porphyry Cu-Au+-Mo; Pb, Zn, Au-Ag and fairly poor Ag, PGE, As, Hg, Bi etc. - e.x., Anarak known deposits in Central Iran associated with Pg (mainly Pg2) subalkaline volcanites (E. Romanko et al., 1984) ) ZONING related to known subduction of Arabian plate, e.x.: subduction-related (1) - intraplate (2) rocks:

1: Eocene shoshonites etc. - Paleocene-Oligocene calc-alkaline intrusives - Miocene-Recent calc-alkaline volcanic (-plutonic) rocks

2: Paleogene? (Lut block) - Neogene intraplate subalkaline - alkaline rocks - Quaternary Afghanistan carbonatites etc. Alpine compression in subduction depth up to 200 km in Central Iran, at least, partly compensated, as proposed, by contemporaneous / younger Pg?-N-Q intraplate magmatism of Iran - Afghanistan - SouthEast Pamir (Pg-N?) and maybe Saudi Arabia carbonatites etc.

This work was made due to the State program of the Geological Institute RAS.

How to cite: Romanko, A., Imamverdiyev, N., Heidari, M., Rashidi, B., Malykh, M., Vikentev, I., and Poleshchuk, A.:  Intraplate Ca-rich and Ca-usual igneous rocks in Baluchestan, Iran associated with real carbonatites of Afghanistan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14434, https://doi.org/10.5194/egusphere-egu25-14434, 2025.

The process of magmatic melt intrusion into permeable zones of the lithosphere, as well as deformation of the permeable region of magmatic channels, is studied within the framework of two-speed thermohydrodynamics of viscous compressible media. The model has applications in the problem of evolution of magmatic systems in the lithospheric mantle and crust of cratons and the ocean-continent transition region. The mathematical model of two-speed hydrodynamics of high-temperature melts is thermodynamically consistent and takes into account such dissipative processes as phase viscosity, thermal conductivity, interphase friction, and surface effects in a heterophase medium. Taking into account the compressibility of the medium allows us to study heat and mass transfer in flows of heterophase melts with a high content of magmatic fluids. Numerical modeling of magmatic melt intrusion into vertical channels was performed for problems characterized by the following parameters: temperature of the two-phase medium 500-1200°C, melt viscosity 10¹-10⁶ P, velocities of the carrier phase and inclusions were 10^-3-10^-1 cm/s. The injected high-temperature heterophase magmatic flow was specified as non-uniform in terms of the content of the dispersed phase. This leads to the formation of two- and three-layer flows in the gravity field.

The process of introduction of a high-temperature heterophase medium into a permeable zone located at a lower temperature is shown in Figure 1. The introduced flow is characterized by a lower content of inclusions compared to their content in the channel. The development of instability of the intruded flow is caused by the initial heterogeneity at the boundary.

Figure 1. Dynamics of the introduction of a high-temperature heterophase substance into a vertical channel in a gravity field: the distribution of temperature (left) and volume content of dispersed phase particles (right) is shown for different moments in time.

The difference in the nature of the developed flow for melts with different viscosities is shown in Figure 2.

Figure 2. Distribution of temperature (left) and volume content of dispersed phase particles (right) during the introduction of a heterophase substance with different viscosities of the carrier phase (10-1, 100, 101, 102 P)

The work was carried out with the financial support of the Russian Science Foundation, grant No. 24-27-00411.

How to cite: Imomnazarov, S., Perepechko, Y., and Sorokin, K.: Dynamics of two-phase flows in magmatic channels, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17151, https://doi.org/10.5194/egusphere-egu25-17151, 2025.

Much debate exists concerning mechanisms of crustal material transfer from subducting slab to overlying mantle. Formation of mélange rocks by physical mixing of slab components within subduction plate interface is predicted to transfer their compositional signal to source of arc magmas by ascending as diapirs from slab-top. Despite being supported conceptually and through modeling, existence of these diapirs in global subduction architecture remains inconclusive. plate interface. Here we present a comprehensive study on eclogites with distinct pressure-temperature-protolith histories from a deeply buried mélange “package” in the Atbashi low-temperature (LT)- high-pressure (HP) metamorphic complex, Kyrgyzstan section of the South Tianshan Metamorphic Complex (STMC), southern Altaids. Recent studies in the Chinese section of the STMC disclose massive sediment accretion at ~80 km depth along the subduction interface, suggesting continuous refrigeration, by incoming cold material from the slab, and juxtaposition to the “cold nose” of mantle wedge. In addition, transient thermal excursion was revealed, in region, from strikingly concordant chemical zonation of garnet in coesite-bearing oceanic eclogites, disclosing the potential translation of ultra-high-pressure rocks (UHP) refrigerated slices near to a relatively hotter mantle wedge. In this study, field mapping, bulk-rock geochemistry, metamorphic petrology, Zr-in-rutile & Ti-in-quartz thermobarometers, thermodynamic modeling, rutile & zircon trace elements, and U-Pb chronology analyses have been conducted to provide the first tangible eclogitic rock evidence recording mélange diapir melting signal (MDP) and experiencing substantial thermal excursion in a well-preserved refrigerated subduction plate interface, as confirmed by the pervasive presence of lowtemperature eclogitic rocks. Additional multi-disciplinary data, especially those Late Carboniferous ones, are also compiled from regional various lithologies to fingerprint the temporal-spatial variations of mantle signal and crustal feedback during which the eclogitic mélange rocks contemporaneously formed and their fate during substantial thermal excursion. Available data provide insights into a model of mélange diapir melting in refrigerated subduction plate interface as substantiated in the STMC. Implications for such process with a momentous contribution in transferring crustal volatile from slab surface to arc lava, regulating terrestrial geochemical cycle, are thus discussed.

How to cite: Sang, M.: Implications for mélange diapir melting from HT eclogite in refrigerated subduction plate interface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17317, https://doi.org/10.5194/egusphere-egu25-17317, 2025.

 Triangular diagrams of pyrope compositions for minor elements – Mn, Na, Ti in wt%  are proposed to assess the diamond grade  of kimberlite pipes.

. Basing on group cluster analysis, diagrams are constructed for pyropes from high-diamondiferous (>1 ct/t) (Fig.1), poor and non-diamondiferous kimberlites (<0.1 ct/t) (Fig.2) of Yakutia and Angola. Oval areas correspond to peridotite, eclogitic, and websterite mantle paragenesis (Sobolev, 1971), the diameter of the analytical point is proportional to the CaO content. In highly diamondiferous kimberlites (Fig. 1), pyropes of peridotite dominating and eclogitic and websterite associations are equally present. Trends in their compositions overlap in the ratios of Na2O, MnO and TiO₂ in all CG

Pyropes of diamond-poorly kimberlites (Fig. 2) do not show such overlap, and for each of their CG they are isolated or have a predominance of one paragenesis over another.

Discussion. The presence of pyrope CGs from different deep sources indicates the hybridization of the proto-kimberlite melt, which assimilated the rocks of the peridotite, eclogite, and websterite "layers" of the mantle. This explains the high diamond content of kimberlites, which assimilated diamonds from these three deep sources. In poor diamondiferous kimberlites, pyropes of various paragenesis are extremely unevenly represented, which is due to the weak interaction of the melt with the "layers" of diamondiferous eclogites and websterites. The catalytic role of Ti, Na, and Mn in the process of diamond formation was pointed out by V.A. Milashev (Milashev, 1994) and J. Gurney (Gurney et al., 1994). Pyropes of highly diamondiferous kimberlites are characterized by a short TiO2 trend and a fairly long Na₂O trend (Fig. 1). Pyropes of poorly diamondiferous kimberlites, on the contrary, are distinguished by a long or unexpressed TiO₂ trend and a limited Na₂O (Fig. 2)

Conclusions. The revealed regularities in the distribution of impurity elements in pyropes from kimberlites of different degrees of diamond content are confirmed by diagrams with an MgO-MnO "diamond window", where most of the pyrope grains of highly diamondiferous pipes fall (Figs. 1 and 2). They can be used to assess the diamondiferous potential of kimberlites based on mineralogical and geochemical criteria.

• Dawson J.B., Stephens W.E. Statistical classification of garnets from kimberlites and xenoliths. J. Geol. 1975. Vol. 83. № 5. P. 589-607
• Grifin W.L., Ryan C.G. Trace elements in indicator minerals: Area selection and target evaluation in diamond exploration. J. Geochem. Explor. , Vol. 53, P. 311-357.
• Ivanov A. S. 2015. A New Criterion of Kimberlite Diamond Content. Proceedings of the XII All-Russian (with international participation) Fersman session. KSC RAS, Apatity, pp. 268-270,
• Milashev V.A. 1994. Environment and processes of formation of natural diamonds. "Nedra", St. Petersburg, 142 p.
• Sobolev N.V. 1994. On the mineralogical criteria of diamond content of kimberlites. 1971. №3. – P. 70-80 J. J. Gurney, R. O. Moore. Geochemical correlation between kimberlite minerals and Kalahari Craton diamonds, Journal. Russian Geology and Geophysics, pp. 12 – 24,

How to cite: Ivanov, A., Zinchenko, V., Ashchepkov, I., and Kostrovitsky, S.: Ca, Mn, Na admixtures in pyropes as indicator of the diamond grade in kimberlites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18578, https://doi.org/10.5194/egusphere-egu25-18578, 2025.

Carbonatite melts, while representing a small fraction of all magmas on Earths, are important features of the deep carbon cycle [1]. These melts are very reactive and quickly evolve during their ascent from a CO₂-rich (CO₂ higher 40 %) and SiO₂ poor (SiO₂ around 0 % wt) to compositions including more SiO₂ and relatively less CO₂ [2,3]. The physical properties of what is known as transitional melts (high CO₂ contents and SiO₂ content below 15% wt) at high pressure are not well constrained, although they are important for understanding the dynamics of carbonatite melt migration and chemical evolution. In this study we determined one high magnesium carbonatite with a ratio Ca/(Mg+Ca) ≈ 0.2 and one dolomite carbonatite with a ratio Ca/(Mg+Ca) ≈ 0.5. Both compositions have a 12 % SiO₂ content and 5 % wt H₂O content. We applied the in situ X-ray absorption method in combination with XCT-tomography in a Paris -Edinburgh press at the Psiché beamline of Soleil synchrotron to determine the density of melts [4]. We measured for each composition the melt density between 2 -4 GPa and 1200 K -1900 K and  complemented the in situ data with sink/float experiments at 4 GPa and temperature of 1700 K, using B₄C and forsterite markers. Both types of experiments showed that dolomite carbonatite melts (high Ca content) with 12 % SiO₂ have densities in the range of 2.9 – 3.05 g.cm^-3, closer to that of a forsterite than carbonatites with 0 % SiO₂ (indicating that even small amounts of SiO₂ tend to increase significantly the density compared to pure carbonatite melts [5]. The implications of this results for the mobility of transitional melts in the upper mantle will be discussed.

[1] Jones et al. (2013) Rev. Min. Geochem. 75, 289.

[2] Hammouda & Keshav (2015) Chem. Geol. 418, 171.

[3] Moussallam, et al. (2015) Chem. Geol. 418, 198.

[4] Ritter et al. (2020) EPSL 533, 116043.

[5] Massuyeau et al. (2023) Chem. Geol. 622, 121275.

How to cite: Clesi, V., Perillat, J.-P., Henry, L., Wood, M., Cardon, H., Klemme, S., Rohrbach, A., and Sanchez-Valle, C.: Density of high SiO2 carbonatite liquids in the upper mantle., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18840, https://doi.org/10.5194/egusphere-egu25-18840, 2025.

Abstract

This study presents an experimental simulation of interactions between two distinct lithologies, representing the contact zone between the asthenosphere and subcontinental lithosphere. These compositions were layered in the capsule (sandwich runs) and subjected to pressures and temperatures representative of two subcontinental mantle of 75 and 130 km, corresponding to Phanerozoic lithosphere thicknesses. The temperatures range from 900°C to 1450°C to simulate different metasomatic reactions and fusion processes in normal geothermal environments and anomalous conditions of high potential temperatures. The experiments were performed using a belt-type high-pressure-high-temperature apparatus, using toroidal pressure plates. Compositions were prepared from pure oxides, carbonates, and hydroxides.

The asthenospheric representative layer is a mixture of fertile lherzolite (MPY) enriched with 30% eclogite (GA1) and 0.75 wt.% CO₂. The lithospheric representative layer consists of NHD, a depleted lherzolite metasomatized with 0.8 wt.% H₂O and 0.17 wt.% K₂O. These compositions have been used in previous experimental studies, enabling direct comparison of our results with those from simpler compositional systems.

The results confirm that small amounts of C-O-H volatiles significantly lower the melting point of peridotite. Melting begins at 900°C at 2.5 GPa and at 1050°C at 4.5 GPa. Amphibole stability is observed up to 4.5 GPa, demonstrating the lithosphere's substantial capacity to retain water when interacting with enriched asthenospheric compositions, likely influenced by prior subduction events. Carbon remains dissolved in carbonate minerals at 4.5 GPa up to 1050°C. As the temperature increases, carbon transitions from being dissolved in the melt to the vapor phase. Liquid compositions are basanitic at low melt fractions and evolve to trachyandesitic above 1200°C.

This research focuses on metasomatic reactions involving fluids and melts generated under adiabatic decompression. Insights contribute to understanding magmatic processes at rift systems in supercontinent cycles, where ancient lithospheric plates accumulate volatiles. Additionally, this study advances the understanding of mantle geodynamics by examining water and carbon storage in mineral phases and the dehydration and decarbonation reactions observed experimentally.

Keywords: experimental petrology, mantle metasomatism, volatile geodynamics, high-pressure melts.

How to cite: Dornelles Kern Tolotti, C. and Vieira Conceição, R.: Experimental investigation of C-O-H volatile effects at the subcontinental lithosphere-asthenosphere boundary, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20349, https://doi.org/10.5194/egusphere-egu25-20349, 2025.

We report a three-dimensional, two-phase thermal-chemical-fluid dynamical model and its application to explore the evolution of magma bodies.  The model solves for velocity using a finite-element approach, and for transport using a control-volume scheme to ensure conservation of energy, mass and components.  Solid and melt phases are modelled as Stokes fluids with very different Newtonian viscosities.  Individual crystals in the solid matrix are incompressible, but the solid phase is compressible to account for changes in melt fraction.  The formulation captures compaction and convection of the solid matrix, and flow of melt via a Darcy-type formulation at low melt fraction, and a hindered-settling type approach at high melt fraction.  It also captures heat transport by conduction and advection, melt-solid phase change, and component transport and reaction.  A chemical model is used to calculate phase fraction and composition.  The numerical package sequentially solves for (1) melt and solid velocity (mass and momentum conservation); (2) enthalpy and component transport (energy and component conservation) and (3) phase fraction and composition (chemical model).  Material properties such as density and viscosity are coupled to solution fields such as melt fraction and composition to yield a highly non-linear system of coupled equations which are solved iteratively.

We apply the code to investigate convection and melt segregation processes in a cooling magma body.  Our findings suggest that convection is expected across a wide range of magma reservoir geometries, melt fraction and bulk composition.  The rate of cooling and crystallization is a primary control on whether convection is observed, with thin bodies cooling and crystallizing before convection becomes established.  In more slowly cooled bodies, convection and melt segregation interact to produce spatially complex and dynamically evolving variations in melt fraction and bulk composition, which often differ significantly from simple conceptual models that envisage accumulation of buoyant, evolved melt at the top of the reservoir and dense residual solid at the base.  The transition between convecting- and non-convecting behaviour is also heavily influenced by the relationship between solid phase shear viscosity and melt fraction.  The solid phase bulk viscosity, which is indistinguishable from shear viscosity in one-dimensional analysis, plays a key and distinct role in controlling the predicted magma reservoir dynamics.

How to cite: Hu, H., Salinas, P., and Jackson, M.: Convection, melt segregation and chemical differentiation in crustal magma reservoirs: Insights from 2- and 3D numerical models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4711, https://doi.org/10.5194/egusphere-egu25-4711, 2025.

The East Eifel Volcanic Field (EEVF) in western Germany comprises numerous scoria cones, maars, and lava domes, with recent geodetic measurements revealing uplift rates of up to ~2 mm/yr. Deep low-frequency earthquakes indicate ongoing magmatic processes and transcrustal melt pathways. To refine the understanding of the geometry and volume of potential magmatic structure, we present a 3D gravity and magnetic inversion of the uppermost crust beneath the EEVF.

Initially, synthetic forward modeling evaluated the detectability of magma bodies of varying sizes and depths, considering realistic density and susceptibility contrasts. We then applied advanced gravity data processing methods—namely terracing and clustering—to highlight subtle anomalies and improve interpretability prior to inversion. The subsequent inversion of the Bouguer gravity anomaly and total magnetic intensity data employed a flexible regularization scheme that balances smoothness and compactness, enabling realistic imaging of magmatic accumulations. As potential-field data alone is non-unique, we plan to incorporate results from local earthquake tomography provided by the ongoing Large-N seismic experiment in the Eifel. Notably, preliminary tomographic results suggest a cylindrical anomaly approximately 3 km in diameter extending from near-surface to ~10 km depth beneath the Laacher See. These seismic constraints will help reduce ambiguity in the final model by offering well-resolved information at shallow to mid-crustal depths and correlating known structures in both gravity and tomography. 

The resulting 3D model will illuminate the lateral and vertical extents of structures origination from magmatic processes beneath the EEVF, advancing our knowledge of its transcrustal magmatic system. This work will also inform future scientific drilling under the ICDP-EIFEL initiative, where new boreholes and monitoring efforts aim to clarify volcanic processes in this intraplate volcanic region.

How to cite: Sobh, M., Gabriel, G., Götze, H.-J., Strehlau, R., Fadel, I., Zhang, H., and Dahm, T.: Delineation of the geometries of magmatic structures beneath the East Eifel Volcanic Field (Germany) Using 3D Gravity and Magnetic Inversion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6602, https://doi.org/10.5194/egusphere-egu25-6602, 2025.

The volcanic rocks belonging to the Maden Complex are observed along the Southeastern Anatolian Orogenic Belt, and the study area covers the surroundings of Malatya (Türkiye). The Eocene (?) Maden Complex are represented by basalt and diabase dykes cutting them. The studied rocks have high Mg# (51.7-92) values. With increasing Zr ratios, positive trends are observed in CaO, TiO₂, Fe₂O₃, Ba and Sr values, and negative trends are observed in MgO, Al₂O₃, Ni, and Co values. Positive trends in CaO and Sr values ​​indicate the effect of plagioclases in fractional crystallization. Trends in TiO₂, Ni and Fe₂O₃ values ​​indicate fractional crystallization of olivine, pyroxene and Fe-Ti oxides. The Maden Complex have relatively low La/Yb (1.16-6.69) and Nb/La (0.20-1.45) ratios, indicating a lithospheric mantle/lithospheric-asthenospheric mantle origin. In the primitive mantle-normalised multi-element diagram, negative trends are observed in Rb, P, Nb and Ti elements, and positive trends in Sr and Ba values ​​of the rocks belonging to the Maden Complex. A nearly horizontal trend is observed in the chondrite-normalised multi-element diagram. The La_N/Lu_N (LREE/HREE) ratios among the light rare earth elements (LREE) and heavy rare earth elements (HREE) of the studied volcanic rocks range from 0.79 to 4.76, showing weak to moderate fractionation. The basalts and diabases belonging to the Maden Complex show insignificant negative Eu anomalies, and the Eu/Eu* values ​​vary between 0.81 and 1.06.  The Dy/Yb ratios of the studied volcanic rock samples vary between 1.49 and 1.87. These ratios indicate that these rocks were derived from a spinel-bearing lherzolite source representing shallow depths. Mineral chemistry analyses were performed on pyroxene and plagioclase minerals in the studied volcanic rocks. According to pyroxene minerals, the temperature (T) and pressure (P) values ​​of the rocks vary in the range of (1194-1442) and (2.8-20), respectively. According to plagioclase minerals, the T and P values ​​vary between (945-1049) and (26.6-55.7).

The ⁸⁷Sr/⁸⁶Sr_(i) values ​​of the studied volcanic rocks vary between 0.703514 and 0.704958, ¹⁴³Nd/¹⁴⁴Nd_(i) values ​​vary between 0.512861 and 0.512897, and they exhibit a sequence close to the MORB field in the ⁸⁷Sr/⁸⁶Sr_(i) versus ¹⁴³Nd/¹⁴⁴Nd_(i) variation diagram. ƐNd_(t) values ​​range from 5.6 to 6.3, and T_DM(Ga) values ​​vary between 0.45 and 0.83. ²⁰⁶Pb/²⁰⁴Pb_(i) values ​​vary between 18.42267 and 19.39642, ²⁰⁷Pb/²⁰⁴Pb_(i) values ​​vary from 15.54136 to 15.62174, ²⁰⁸Pb/²⁰⁴Pb_(i) values ​​range from 38.40535 to 39.04312. The ²⁰⁷Pb/²⁰⁴Pb_(i) diagram versus ²⁰⁶Pb/²⁰⁴Pb_(i) also shows a sequence close to the MORB field. In light of all data, it is thought that the volcanic rocks of the Maden Complex are derived from a magma source representing shallow depths of MORB origin. This study was supported by the TUBITAK project numbered 123Y070.

Key Words; Geochemistry, Maden Complex,  Mineral chemistry, Sr-Nd-Pb isotopes

How to cite: Sar, A., Rizeli, M. E., Ertürk, M. A., and Yılmaz, İ.: Petrogenesis of the Maden Complex Volcanic Rocks in the Southeastern Anatolian Orogenic Belt (Malatya- Eastern Türkiye): insight from whole-rock geochemistry, mineral chemistry, and Sr-Nd-Pb isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8091, https://doi.org/10.5194/egusphere-egu25-8091, 2025.

The Guleman ophiolite is a part of the Southeast Anatolian Orogenic Belt (SAOB) ophiolites. The Guleman ophiolite, which is located to the northeast of Maden and covers an area of 200 square km east of the Hazar Lake, is situated 50 km southeast of Elazığ, and it is one of the important ophiolitic massifs in the SAOB. The Guleman ophiolite formed in the southern branch of the Neo-Tethys ocean and was emplaced beneath the Anatolide-Tauride platform. It is usually in tectonic contact with the other units, and some of it has been intruded by Late Cretaceous granitic rocks and is covered by younger sediments. The Guleman Ophiolite is composed of serpentinised mantle tectonites, ultramafic-mafic cumulates, isolated gabbro and sheeted (diabasic) dykes. The mantle section of Guleman ophiolite mainly consists of serpentinised harzburgites and dunites with significant, economically level podiform chromitites. The serpentinised mantle peridotites consist of relicts of olivine and orthopyroxene, serpentine minerals and Cr-spinel ± carbonate minerals. Petrographic study of serpentinised peridotites shows that the rocks consist predominantly of lizardite and portlandite serpentines and olivine and have the opaque mineral assemblage of magnesioferrite+spinel developed during serpentinisation of the rock. Carbonate-bearing veins were observed in the serpentinite. The typical pseudomorphic textures consist of meshes and bastites. There are two types of alteration mineralogy and textural relationships. Firstly, lizardite mesh-textured vein networks with relict olivine cores, and secondly, bastite texture with serpentinisation of orthopyroxene. Mesh-textured serpentine veins with fresh olivine cores occur in all samples, while bastite texture occurs in harzburgite samples. The XRD pattern shows that the main constituents of the sample were the lizardite (Mg₃(Si₂O₅)(OH)₄) and portlandite (the calcium analogue of brucite) Ca(OH)₂ minerals, which have various microstructure features. This study was supported by the TUBITAK project numbered 124Y011.

Key Words: Guleman Ophiolite, Serpantinisation, Petrography, XRD, Türkiye

How to cite: Ertürk, M. A., Rizeli, M. E., Sar, A., Beyarslan, M., and Aysal, N.: Serpentinisation of Guleman Ophiolite in the Southeast Anatolian Orogenic Belt (Türkiye) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8093, https://doi.org/10.5194/egusphere-egu25-8093, 2025.

Simulating the chemical evolution of magmatic systems can be done with thermodynamic equilibrium modelling and recently developed melting models do quite a good job of predicting observations and reproducing experiments for a wide range of compositions. Yet, it remains a significant computational challenge as some of the most recent melting models include 11 oxides along with pressure and temperature, which makes this a 13-dimensional Gibbs energy optimisation problem. We recently developed the open-source parallel software package MAGEMin [1], along with an easy-to-use Julia interface (MAGEMin_C.jl [2]). Over the last year, we also developed a web-based graphical user interface, MAGEMinApp [3], with which users can easily compute pseudo-sections, do fractional crystallization experiments, or predict seismic velocities.

However, despite the progress, each point-wise thermodynamic calculation still takes 10-50 milliseconds (depending on the complexity of the system). This is too slow if one wishes to directly couple thermodynamic and thermo-mechanical simulations of the magmatic system, as those may require 1000’s-100’000s of calculations per timestep.

An alternative approach is to develop simplified parameterizations from the complete thermodynamic models (e.g., using machine learning tools). That, however, requires recalibration for different scenarios, and gives up some of the predictive power of the models, such as the chemistry of the stable mineral assemblage or seismic velocities, unless the system was trained on that.

We therefore developed a new approach in which we dynamically update a database of precomputed points that only performs new thermodynamic calculations for points that do not yet exist in the database. We only store the minimum required information per point, with which we can reconstruct all derived thermodynamic quantities without having to redo the minimization. This significantly reduces the computational effort and allows coupling thermodynamic simulations with thermo-mechanical simulations in a self-consistent manner.  We illustrate the power of the method with 2D/3D thermo-kinematic simulations of magmatic systems, as well as by reactive two-phase flow calculations applied to small-scale magma transfer processes in lower crustal migmatites.

[1] https://github.com/ComputationalThermodynamics/MAGEMin

[2] https://github.com/ComputationalThermodynamics/MAGEMin_C.jl

[3] https://github.com/ComputationalThermodynamics/MAGEMinApp.jl

How to cite: Kaus, B., Riel, N., Dominguez, H., Frasunkiewicz, J., Aellig, P., and Moulas, E.: Fully coupled petrological/thermo-mechanical models of magmatic systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8624, https://doi.org/10.5194/egusphere-egu25-8624, 2025.

The modern view of magmatic systems includes transport and storage of melt at depths within the solid crust. An important process that directly controls the thermo-physical properties of magmatic systems is the chemical differentiation of the melt. Calculating the thermodynamic properties of the melt during its transport through the system is a well-known computational bottleneck in most multi-phase transport algorithms.

We present a Multi-Layer-Perceptron (MLP) surrogate model for fast prediction of thermodynamic properties of silicate melts in arc settings. The MLP takes a bulk rock composition of nine major oxides (SiO2-Al2O3-CaO-MgO-FeO-TiO2-NaO-K2O-H2O), temperature, and pressure as input variables and returns the melt fraction, composition, as well as the melt and system density. The surrogate model’s ability to predict thermodynamic properties is tested for data it has not seen during the training process. Results indicate that the MLP generalizes well within the range of the database. The melt fraction and components (i.e., major oxide concentration in the melt) are predicted with a root-mean square error (RMSE) of less than 1 wt-% and the densities with an average RMSE of ca. 5 kg/m3. 

The synthetic data set for training and testing the model has been generated with MAGEMin, a parallelized Gibbs energy minimization software (Riel et al., 2022). MAGEMin features adaptive mesh refinement (AMR) capabilities. This functionality allows for high resolution phase diagrams at important reaction lines with a minimum amount of computational points. Our synthetic database consists of 360’000 MAGEMin minimization points. As input parameters to MAGEMin we used anhydrous compositions from arc settings provided by the GEOROC database (Lehnert et al., 2000) varying 43-60 wt-% SiO2 and a pressure-temperature range of 650-1000°C and 1.0-10.0 kbar.

Predicting melt properties with the surrogate model is a point-wise operation which takes only a fraction of a second for hundreds of thousands of points. This functionality opens the door for accelerating mineral equilibria calculations within the framework of high-performance computing transport algorithms. We discuss possible application of the surrogate model within the framework of modern geodynamic algorithm architectures.

References:

Lehnert, K., Su, Y., Langmuir, C. H., Sarbas, B., & Nohl, U. (2000). A global geochemical database structure for rocks. Geochemistry, Geophysics, Geosystems, 1(5).

Riel, N., Kaus, B. J., Green, E. C. R., & Berlie, N. (2022). MAGEMin, an efficient Gibbs energy minimizer: application to igneous systems. Geochemistry, Geophysics, Geosystems, 23(7), e2022GC010427.

How to cite: Candioti, L. G., Nathwani, C. L., and Chelle-Michou, C.: A neural network-based surrogate model to accelerate mineral phase equilibria calculations for silicate melts in arc settings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8644, https://doi.org/10.5194/egusphere-egu25-8644, 2025.

Understanding how melt is extracted and makes its way toward volcanoes is a fundamental problem in magma dynamics. Geological observations of ophiolites show tabular dunite channels, which are commonly considered to be reactive channels for melt migration. The reaction-infiltration instability has been identified as an important mechanism responsible for the formation of these high-porosity melt channels in the upper mantle. To better understand this mechanism, we have extended previous linear analysis and performed non-linear numerical simulations in a compacting, chemically reactive porous medium.

Strong interactions between compaction and dissolution lead to two interesting unstable features: (1) high-porosity channels and (2) compaction-dissolution waves. The channeling instability that grows monotonically comes from the positive feedback between chemical reaction and melt percolation. The oscillatory compaction-dissolution waves show a checkerboard pattern that migrates upwards in the melting region, driven by the nonlinear feedback between compaction and reaction. These instabilities are controlled by two key dimensionless parameters: the stiffness, which characterizes the system's ability to compact, and the Damköhler number, which describes the relative importance of reaction to advection. The stiffness is strongly affected by the compaction length, which may either follow an inverse power-law dependence on porosity or only a weak dependence on porosity. Here we present a regime diagram with a range of stiffness and Damköhler number values and show that compaction-dissolution waves are favoured in systems with smaller compaction length and lower stiffness relative to high-porosity channels.

The parameter regimes predicted by linear theory align well with the non-linear numerical simulation results. Simulations also show strong interactions between melt channels and oscillatory waves, where the melt channels are focused in the upper domain and porosity waves are in the lower part. The relationships between high-porosity channels and compaction-dissolution waves in this study may shed new light on the geochemical and petrological observations related to magma migration in the mantle.

How to cite: Huang, M., Rudge, J., and Rees Jones, D.: Channels or waves: controls on melt migration through the upper mantle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8875, https://doi.org/10.5194/egusphere-egu25-8875, 2025.

Owing to their abundance and relative availability on Earth's seafloor, mid-ocean ridge basalts (MORBs) have a well-defined chemical element budget, reflected by the low standard deviation associated with typical normal MORB (N-MORB) composition [1]. However, the exact mechanisms leading to magma differentiation and MORB generation remain debated, hindering our ability to evaluate MORB parental magma composition. In this study, we leverage the predictive power of the BDD21 numerical framework [2, 3] to obtain a representative trace element budget of parental MORB magma and assess its ability to fractionate into the N-MORB composition. Utilising revised parameterisations for mineralogy, melting, and partitioning, we couple BDD21 with numerical simulations of a MOR system driven by seafloor spreading in which we track the evolution of partial melting, mineral modal abundances, and concentrations of incompatible elements. Parental magma compositions are determined once simulations reach a steady state, and magma chamber replenishment models are employed to predict the trace element budget of the erupted liquid. We explore a range of geophysical and geochemical parameters to evaluate their effect on computed trace element concentrations and use the Bayesian inference framework BayesBay (https://github.com/fmagrini/bayes-bay) to invert for the set of parameters that best reproduces the N-MORB composition. Previous magma chamber replenishment models [4] are extended to account for multiple crystallisation events and melt-crystal interaction. Modelling outcomes suggest that petrologically constrained fractionation of parental magma compositions obtained through BDD21 yields glass compositions compatible with the N-MORB budget. Nevertheless, our results show a systematic underestimation of Sr concentration, indicating the presence of recycled oceanic crust in the MORB source region.

[1] Gale, A., Dalton, C. A., Langmuir, C. H., Su, Y., & Schilling, J. G. (2013). The mean composition of ocean ridge basalts. Geochemistry, Geophysics, Geosystems, 14(3), 489-518.

[2] Ball, P. W., Duvernay, T., & Davies, D. R. (2022). A coupled geochemical‐geodynamic approach for predicting mantle melting in space and time. Geochemistry, Geophysics, Geosystems, 23(4), e2022GC010421.

[3] Duvernay, T., Jiang, S., Ball, P. W., & Davies, D. R. (2024). Coupled geodynamical‐geochemical perspectives on the generation and composition of mid‐ocean ridge basalts. Geochemistry, Geophysics, Geosystems, 25(2), e2023GC011288.

[4] St C. O’Neill, H., & Jenner, F. E. (2012). The global pattern of trace-element distributions in ocean floor basalts. Nature, 491(7426), 698-704.

How to cite: Duvernay, T., Jiang, S., and Magrini, F.: Coupled Geodynamical-Geochemical Perspectives on the Generation and Composition of Mid-Ocean Ridge Basalts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15139, https://doi.org/10.5194/egusphere-egu25-15139, 2025.

The Changbaishan volcano (CBV) located on the border of China and North Korea, is one of the most dangerous active volcanoes on Earth. The CBV has experienced two “unrest periods” since 2000C.E. with uplift, increased ³He/⁴He ratio gas emissions and increased seismicity frequencies. During the intermediate “rest period”, subsidence occurred particularly on the eastern part of the Tianchi caldera. Whereas the magmatic system beneath the volcano is likely responsible for the surface deformation, several factors can significantly influence the surface deformation field such as the geometry, physical properties, and connection between separate magma or mush chambers. The mechanism of uplift surface at CBV is interpreted as magma recharge and the mechanism of subsidence is still under debate. Previous geophysical investigations and satellite data indicate that a shallow magma chamber might exist at 5 km depth, and the shallow magma chamber plays an important role in producing the surface deformation field. Understanding the magmatic system beneath CBV will improve the assessment of the risk of CBV.

Here, we utilized a new approach to construct a 3D thermo-mechanical model of the magmatic system beneath CBV developed on the basis of seismic velocity data collected during the “rest period”. We compare model output with InSAR data of the same period, to analyze the mechanism of the surface velocity field during the “rest period”. We test the influence of the shallow magma chamber at 5km, the connection of the magma system and physical properties of the magma chamber and surrounding host rock. Our results are consistent with there being four interconnected magma chambers beneath the CBV compared with InSAR observation. They support that a shallow magma chamber exists at 5km depth. This shallow magma chamber depth causes a convection field, and the convection field induced a downward flow at CBV area. Magma channels connecting the different magma batches play an important role in producing the uprise velocity to the surface. The higher temperature of the magma channels, the lower viscosity of the surrounding host rock and the higher density contrast with the surrounding host rock can increase the uprise velocity magnitude.

How to cite: Liu, H., Yang, J., zhao, L., Kaus, B., Spang, A., and Sun, B.: Numerical simulations of the influence of the magmatic system beneath Changbaishan volcano on surface deformation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16021, https://doi.org/10.5194/egusphere-egu25-16021, 2025.

Magnetite-apatite (MtAp) deposits, also known as iron-oxide-apatite or Kiruna-type deposits, are critical sources of high-grade iron ore and rare earth elements (REE), essential for industrial applications and the global transition to green energy. The formation of MtAp deposits is commonly attributed to the immiscibility between iron oxide phosphate liquids and silicate magma (FeP–Si). Recent studies have shown that light rare earth elements preferentially partition into the iron-phosphorus melt, explaining the enrichment of light rare earth elements in MtAp deposits. While there is good evidence of an origin involving sub-volcanic intrusion to volcanic extrusion of an Fe-enriched orthomagmatic melt, the exact formation mechanisms remain controversial.

This study focuses on the El Laco deposit in northern Chile, adopting the hypothesis that spontaneous magma unmixing has indeed occurred within an El Laco-type subvolcanic magma body. The research aims to explore the formation mechanisms of magnetite-apatite (MtAp) deposits by investigating the role of iron-rich magmatic melts. Using a one-dimensional (1D) three-phase mechanical model based on existing theoretical frameworks, we simulated the separation and accumulation of immiscible iron-rich melts within an increasingly crystalline parent magma. The model reproduces the previously proposed transition from droplet settling to porous drainage mode and quantifies the relative efficiency of both modes of phase separation. We also perform a scaling analysis to define porous, mush, and suspension flow regimes and construct a regime diagram for three-phase flow. The results show that the separation efficiency of immiscible iron-rich melts reaches its maximum under intermediate crystallinity conditions. Furthermore, the model-derived accumulation rate of iron-rich melts can be used to estimate the time required to accumulate immiscible melt sufficient to form magnetite deposits of a given scale. Our findings support the physical viability of the liquid immiscibility hypothesis in the genesis of MtAp deposits and provide new insights into the formation mechanisms of other valuable deposits associated with immiscible melts, such as the segregation of Ni-Cu-Co-enriched sulphide melts in orthomagmatic Cu-Ni-sulphide deposits and metal-enriched magmatic brines in porphyry copper systems.

How to cite: Chai, T. and Keller, T.: Three-phase flow modelling of immiscible melt segregation in the genesis of magnetite-apatite deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18413, https://doi.org/10.5194/egusphere-egu25-18413, 2025.

Deciphering magmatic system dynamics is inherently challenging due to the lack of direct observations of subsurface processes. Numerical modelling serves as a key tool to interpret indirect evidence from petrological and geochemical analyses of igneous rocks. At the heart of magma dynamics lies the interplay between complex multiphase fluid mechanics and multicomponent thermochemistry. Accurate modelling of these systems requires determining stable phase assemblages, which involves computationally demanding Gibbs free energy minimisation across high-dimensional compositional spaces with dozens of end-members. Current algorithms often lack the robustness and efficiency required for real-time integration into coupled thermos-chemical-mechanical models.

Traditional approaches to coupled modelling have frequently employed highly simplified phase relationships, such as single-phase loops, or relied on precomputed lookup tables to avoid the computational cost of real-time phase equilibrium calculations. These methods, however, impose significant limitations. This work introduces an alternative—a petrological model that generates multi-dimensional pseudo-phase diagrams in P-T-X space using pseudo-component end-members. Inspired by ideal solution thermodynamics, this approach eliminates the need for computationally expensive energy minimisation, overly simplistic phase representations, or cumbersome lookup tables. Instead, it employs a computationally efficient Newton method to solve a constrained nonlinear system.

Calibration of the model using standard machine learning techniques allows it to closely approximate key petrological trends, such as fractional crystallisation, observed in experimental data and full thermodynamic calculations. Once calibrated, the model efficiently tracks the dynamic evolution of major mineral and melt phases, including their compositions, across extensive P-T-X ranges. The calibration process further identifies the principal axes of variability, typically reducing the system to 5-6 dominant pseudo-components associated with major liquidus phases. This dimensional reduction significantly simplifies the system’s complexity compared to full thermodynamic models while retaining essential petrological insights.

How to cite: Keller, T.: Efficient Modelling of Magmatic Systems: A Pseudo-Component Approach to Phase Equilibria in Coupled Simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18794, https://doi.org/10.5194/egusphere-egu25-18794, 2025.

Venus is believed to be deformed in a stagnant-lid, episodic-lid, or a plutonic-squishy-lid regime with mantle convection occurring beneath a unified lithosphere [1-3]. Its surface age, estimated at 240–800 Ma from impact crater records [4], suggests either a catastrophic resurfacing event involving rapid lithospheric recycling [5] or continuous, regionally tectonic and volcanic processes [6]. Here we raise a key question how strain localization occurs on Venus: do Venusian faults show evidence of multi-stage activation capable of leading to large-scale lithospheric deformation, and is it possible to use this to unravel the tectonic history of Venus?

To address this, we focused our investigation on the equatorial chasmata system in Eastern Aphrodite Terra, Venus, whose origin continues to be a subject of scientific debate. This study documents that the troughs consistently exhibit asymmetric cross-sectional profiles, with steeper slopes intersected by large-scale faults trending subparallel to the trough axis. These shear zones dip at low angles and occasionally form terraces along the slope profile, exposing sections of the shear planes. The shear planes are radar-smooth and exhibit radar emissivities distinct from the adjacent hanging wall and footwall. We propose that these fault planes be coated with melt films, which in some cases display flow features along downslope trajectories.

The formation of these melt films is explored in the context of frictional melting during co-seismic faulting. Frictional melting may be enhanced on Venus due to its elevated ambient temperatures and the likely water-free, mafic composition of its rocks. However, multi-incremental friction-induced melting is unlikely to result in significant strain localization, and the volume of melt generated even under Venusian conditions is insufficient to be resolved in the available SAR imagery. Instead, we hypothesize that the fault planes act as conduits for transporting magma from shallow subsurface reservoirs to the surface. Volcanic centers and edifices near the steep chasmata slopes and within corona interiors are potential sources for shallow subsurface melt reservoirs. Melt veneers along the fault planes may reduce friction coefficients, facilitating normal faulting at shallow dip angles.

The overall morphology of the troughs suggests that the faults were initially formed as thrust faults and later reactivated. Evidence of their youthfulness is provided by fresh hummocky landslide deposits originating from the steep hanging wall scarps, which partially obscure the exposed fault planes. They were likely triggered by fault-induced seismicity, suggesting that faulting on Venus is seismogenic. Seismic moments for the studied shear zones have been calculated to support fault activation.

References

[1] Solomatov, V. S., & Moresi, L. N. (1996). J. Geophys. Res. Planets, 101(E2), 4737–4753. [2] Turcotte, D. L. (1993). J. Geophys. Res. Planets, 98(E9), 17061–17068. [3] Lourenço, D. L., Rozel, A. B., Ballmer, M. D., & Tackley, P. J. (2020). Geochem. Geophys. Geosyst., 21:e2019GC008756. [4] Le Feuvre, M., & Wieczorek, M. A. (2011). Icarus, 214(1), 1–20. [5] Armann, M., & Tackley, P. J. (2012). J. Geophys. Res. Planets, 117(E12), E12003. [6] Bjonnes, E. E., Hansen, V. L., James, B., & Swenson, J. B. (2012). Icarus, 217(2), 451–461.

How to cite: Karagoz, O., Kenkmann, T., and Gurau, M.: Fault-melt interaction and its implications for Venusian Tectonic regimes in Aphrodite Terra, Venus, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-235, https://doi.org/10.5194/egusphere-egu25-235, 2025.

Wrinkle ridges (WRs) are among the most prevalent tectonic landforms observed on terrestrial planetary bodies, characterized by highly variable relief. They are interpreted as folds overlying blind thrusts, which can reach reliefs of 100’s meters and widths of several 10’s kilometers. The formation and subsurface characteristics of WRs is still debated with unresolved questions, including: i) geometry and likely structural style of associated blind faults, ii) fault depth, iii) number and role of faults, iv) amount of shortening. Several modelling methods have been proposed, however, none of them completely describe the entire spectrum of observations related to WRs morphometry and kinematics.

In this work, we conduct a 2D to 3D geometrical and kinematic reconstruction of a set of globally distributed WRs by applying Trishear and Fault-Parallel-Flow integrated forward kinematic modelling. The methodology allows to model complex fault geometries by assuming area conservation and plane-strain deformation, to determine the fault geometry and kinematics that best fits the observed topography and the measured outcropping faults dip angles.

Our results demonstrate the reliability of the trishear method to model planetary WRs and provide an improvement in understanding Mars’ lithospheric mechanical stratigraphy and WRs kinematics. We demonstrate how the wrinkly and complex nature of WRs can be related to the presence of multiple faults, which accommodate shortening differently. We suggest the presence of a heterogeneous stratigraphy composed of alternations of weaker and friction detachments which promote fault activity characterized by sequential deformation of backthrusts, synthetic thrusts.

The results of the trishear kinematic modelling indicate correlations of the main morphometric parameters of WRs with the geometry and kinematics of the faults. WRs characterized by a higher relief are driven by larger amounts of horizontal along-fault slip, while the broader the width of the main crest, the deeper and more spaced are the faults below the crest (i.e., master fault and possible backthrust). The location of the hinge zone of the main crest, corresponds to the fault dip change at depth.

How to cite: Carboni, F.: Martian wrinkle ridges morphometry and kinematics correlation from Trishear Forward Modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-441, https://doi.org/10.5194/egusphere-egu25-441, 2025.

The magma ocean (MO) phase typically describes the early stage of rocky planets, during which the entire planet is molten due to heat generated by accretion processes. In the case of short-period exoplanets inside the runaway greenhouse limit, this phase may last Gyrs, until the inventory of major greenhouse gasses, such as H2O and H2, is exhausted. The internal evolution of these planets is influenced by various factors, including the exchange of volatiles between the molten planetary interior and the atmosphere. This exchange significantly impacts planetary climate, exoplanet bulk densities, surface conditions, and long-term geodynamic activity by controlling greenhouse effects, surface water stability, and atmospheric composition. This research focuses on modeling this interaction under different redox conditions. Using a coupled computational framework of the planetary interior and atmosphere, we study the detailed evolution of the magma ocean phase, aiming to understand the crystallization sequence and the atmospheric composition in equilibrium with long-lived magma ocean. 

How to cite: Sastre, M., Lichtenberg, T., Bower, D., Nicholls, H., and Kamp, I.: Impact of varying redox states on crystallization and atmospheric composition of rocky exoplanets., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-459, https://doi.org/10.5194/egusphere-egu25-459, 2025.

It is broadly known that magmatic processes play a key role in cooling planetary interiors. While most studies have analyzed the influence of extrusive magmatism (e.g. Armann and Tackley, 2012, Moore and Webb, 2013), recent investigations have shown that intrusive magmatism could also be very efficient for cooling Earth-like planets (e.g. Rozel et al., 2017, Lourenço et al., 2020). Nevertheless, a systematic investigation of the role that the magmatic styles play in the evolution of different terrestrial planets has never been done. We study the effect of the magmatic style on the thermal evolution of Mercury-, Venus-, Mars-, and Moon-like planets, focusing on the magmatism endmembers i.e. ‘fully extrusive’ (Io-like heat pipe model, Moore and Webb, 2013) and the ‘fully intrusive’ (plutonic-squishy lid model, Lourenço et al., 2020).

We use the geodynamical code GAIA in a 2D spherical annulus geometry (Hüttig et al., 2013, Fleury et al., 2024). Our models assume a homogeneous distribution of the heat sources, a depth- and temperature-dependent viscosity (Karato et al., 1986) that follows an Arrhenius law for dry diffusion creep (Karato & Wu, 1993), pressure- and temperature-dependent thermal conductivity and expansivity (Tosi et al., 2013), a time-dependent core cooling (Steinbach & Yuen, 1994), and a melting curve parametrization derived for the Earth’s interior (Stixrude et al., 2009). Apart from surface and core temperature, mantle and core density, planet, and core radius, and initial concentration of radioactive elements, we keep the model parameters similar for all bodies. This choice was made to minimize the differences between models due to the particular conditions of each planet, allowing us to focus our analysis on the influence of intrusive vs. extrusive magmatism rather than each planet’s evolution.

Melting occurs when the mantle temperature exceeds the solidus. For all bodies, we compute partial melting considering latent heat consumption. We extract the melt either to the intrusive melt depth of 50 km for the fully intrusive cases or to the surface for the fully extrusive cases. We delimit the area of buoyant melt from which melts can be extracted by the lithosphere thickness (to avoid re-melting the hot intrusions) and the density crossover at 11 GPa (Ohtani et al., 1995).

For all studied bodies, the convection pattern is characterized by stronger mantle plumes and more vigorous mantle flow for the fully intrusive cases than for the fully extrusive cases. Throughout the evolution of all planet-like models, cases with intrusions present thinner and warmer lithospheres, cooler mantle and CMB temperatures, higher melt production, shallower melting depths with cooler melt temperatures, and higher surface and CMB heat fluxes. Limiting the melt production in the interior by the density crossover greatly impacts the planetary cooling of bodies with high mantle pressures such as Venus, for which an intrusive magmatism style allows for more efficient cooling of the interior while having a warm and thin lithosphere.

Our study provides the first detailed investigation of the effects of intrusive vs. extrusive magmatism on the global evolution of rocky planets, in a comparative planetology sense.

How to cite: Herrera, C., Plesa, A.-C., Maia, J., and Breuer, D.: Effects of magmatic styles on the thermal evolution of planetary interiors, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-862, https://doi.org/10.5194/egusphere-egu25-862, 2025.

Earth’s tectonic history is punctuated by several cycles of supercontinent assembly and breakup that profoundly influenced the lithospheric structure; however, the roles of the various factors controlling continental strength and deformation during the cycles remain debated. The effective elastic thickness (T_e) reflects the lithosphere’s long-term, depth-integrated strength and is useful for deciphering the complex evolution of continents. In this study, we estimate a new global map of continental T_e projected onto a  grid by inverting the cross-spectral properties (admittance and coherence) between Bouguer gravity and topography data obtained from a continuous wavelet transform. Continental T_e ranges from <5 to ~140 km, with a mean and standard deviation of 50 and 33 km, respectively. Based on a gaussian mixture model-based cluster analysis, we delineate tectonically active provinces, stable Archean cratons and transitional lithosphere. We find an obvious positive correlation between T_e and lithospheric thickness obtained from calibrated upper mantle surface wave tomography models. Further comparing the T_e distribution with orogenic age data shows that T_e exhibits a clear time dependence where the strength is governed by the time since the last orogeny. Based on plate cooling models, we indicate that continental T_e corresponds approximately to the depth of the 300±150℃ isotherm. These results favour a diffusive (cooling) model that considerably influences the strength of the continental lithosphere, despite the complex relation between T_e and the thermal, compositional and rheological structure.

How to cite: Lu, Z., Li, J., Audet, P., and Li, C.-F.: Strength of continental lithosphere governed by the time since the last orogeny, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1455, https://doi.org/10.5194/egusphere-egu25-1455, 2025.

The excess abundance of highly siderophile elements (HSEs), as inferred for the terrestrial planets and the Moon, is thought to record a 'late veneer' of impacts after the giant impact phase of planet formation. Estimates for total mass accretion during this period typically assume all HSEs delivered remain entrained in the mantle. Here, we present an analytical discussion of the fate of liquid metal diapirs in both a magma pond and a solid mantle, and show that metals from impactors larger than approximately 1km will sink to Earth's core, leaving no HSE signature in the mantle. However, by considering a collisional size distribution, we show that to deliver sufficient mass in small impactors to account for Earth's HSEs, there will be an implausibly large mass delivered by larger bodies, the metallic fraction of which lost to Earth's core. There is therefore a contradiction between observed concentrations of HSEs, the geodynamics of metal entrainment, and estimates of total mass accretion during the late veneer. To resolve this paradox, and avoid such a mass accretion catastrophe, our results suggest that large impactors must contribute to observed HSE signatures. For these HSEs to be entrained in the mantle, either some mechanism(s) must efficiently disrupt impactor core material into ≤0.01mm fragments, or alternatively Earth accreted a significant mass fraction of oxidised (carbonaceous chondrite-like) material during the late veneer. Estimates of total mass accretion accordingly remain unconstrained, given uncertainty in both the efficiency of impactor core fragmentation, and the chemical composition of the late veneer.

How to cite: Anslow, R., Landeau, M., Bonsor, A., Itcovitz, J., and Shorttle, O.: The efficient delivery of highly-siderophile elements to the core creates a mass accretion catastrophe for the Earth, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3091, https://doi.org/10.5194/egusphere-egu25-3091, 2025.

The behavior of SiO₂ analogs (GeO₂ and SnO₂) under extreme pressure conditions provides critical insights into the structural evolution of oxide materials in planetary interiors. In this study, we investigate the ramp compression of GeO₂ and SnO₂ to ultra-high pressures exceeding 500 GPa, revealing novel high-pressure phases and structural transitions. Using advanced in situ X-ray diffraction techniques, we characterize these high-pressure phase transformations under conditions relevant to the deep interiors of large rocky planets. Our findings significantly enhance our understanding of the high-pressure behavior of SiO₂ and its analogs, with important implications for modeling the deep interiors of super-Earths and other large rocky planets. Finally, our results underscore the vital role of analog materials in exploring the fundamental physics of oxide systems under extreme conditions.

How to cite: Kim, D.: Dynamic Compression of Planetary Analog Materials: Insights into the Interiors of Large Rocky Planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3397, https://doi.org/10.5194/egusphere-egu25-3397, 2025.

Heat flux at the Earth’s core-mantle boundary (CMB) partially controls the outer core dynamics and its associated geodynamo. On the mantle side, spatial and temporal variations in this flux are, in turn, controlled by details of mantle convection. Previous simulations of mantle dynamics showed that CMB heat flux may be locally negative, i.e., in these regions heat flows from the mantle to the core. Here, we investigate the conditions needed to generate such patches of negative CMB heat flux. For this, we perform a series of high-resolution numerical simulations of thermo-chemical convection in spherical annulus geometry using the code StagYY. The compositional initial condition consists in a thin basal layer of chemically denser material (alos referred to as primordial material), which subsequently evolves into piles of hot, primordial material, modelling the large low shear-wave velocity provinces (LLSVPs) observed on global seismic tomography maps. We more specifically explore the influence of two key parameters that promote temperature increase within the piles of primordial material: the excess internal heating within these piles ; and the temperature-dependence of thermal conductivity. We quantify the size and amplitude of negative heat flux patches depending on these parameters. 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 within piles of dense material. However, these parameters also alter the piles stability, such that there is no straightforward relationship between them and the size and amplitude of the negative heat flux patches. Finally, we discuss possible consequences of our findings for core dynamics and geodynamo.

How to cite: Deschamps, F., Guerrero, J., and Amit, H.: Local patches of negative core-mantle boundary heat flux : insights from numerical models of thermo-chemical convection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3892, https://doi.org/10.5194/egusphere-egu25-3892, 2025.

Grain size is one of the primary influencing factors for mantle viscosity. Larger grains lead to increased diffusion creep viscosity and vice-versa. Grain size is a thermally activated process, so with higher temperature grains grow. Increasing temperature lowers the mantle viscosity but the associated grain size would potentially increase the viscosity.  The net result of this counterbalancing effect of grain size evolution and temperature in the lower mantle remains limited. In this study, we use the self-consistent two-dimensional finite volume StagYY to investigate the evolving grain size and its impact on average mantle viscosity. We compare a model with constant grain size to models with evolving grain size along with dynamic recrystallization and analyze the effect of grain size. 

Using grain size evolution parameters for olivine in the upper mantle and bridgmanite-ferropericlase in the lower mantle shows comparable results with previous literature. In this model, the upper mantle primarily undergoes deformation through dislocation creep, while the lower mantle is dominated by diffusion creep. Despite this, the average viscosity of the lower mantle calculated using the evolving grain size model does not significantly differ from that of a constant grain size model. This suggests that grain size variations exert a limited impact on the average viscosity of the lower mantle, which is predominantly influenced by temperature. This limitation arises because of the slow grain growth of the bridgmanite-ferropericlase assemblage due to Zenner pinning. Such slow grain growth is insufficient to counteract the temperature-dependent viscosity effects. In the early Earth, the Zenner pinning effect could be absent due to single phase crystallization from the magma ocean. Without a secondary phase, bridgmanite could grow significantly larger grains. To investigate the impact of faster grain growth, we applied olivine grain growth parameters to the lower mantle. This hypothetical scenario resulted in the formation of exceptionally large grains (~10,000 μm) and delayed the onset of lid-breaking events in our models. It is possible that in the early Earth, the lid-breaking event was delayed due to strong grain size dependent viscosity. However, once whole-mantle convection began, increased lower mantle stress promoted dislocation creep in the presence of these large grains. In such cases, the lower mantle becomes largely independent of grain size, particularly in the present-day Earth scenario.

How to cite: Golabek, G. J., Paul, J., Rozel, A. B., Tackley, P. J., Katsura, T., and Fei, H.: Importance of grain size-dependent viscosity for the early and present-day Earth, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4197, https://doi.org/10.5194/egusphere-egu25-4197, 2025.

The discovery of exoplanets has uncovered a vast spectrum of planetary types, from enormous gas giants to smaller, rocky worlds akin to Earth. Among these, super-Earths are prevalent and are believed to exhibit a range of tectonic regimes. A portion of these have ultra-short periods and orbit their stars in mere hours to days, resulting in synchronous rotation with their host star. This establishes a surface temperature dichotomy like that seen on LHS 3844b, a bare-rock super-Earth with a radius approximately 1.3 times that of Earth, where temperatures reach 1040 K at the point receiving the most intense sunlight on the dayside and drop close to 0 K on the nightside.

We use StagYY to model mantle convection on LHS 3844b in a 2D spherical-annulus geometry. Our models incorporate a temperature-dependent yield stress that captures both near-surface and deep lithospheric rheological variations, rather than assuming a fixed effective yield stress as in previous studies. We represent the effects of various temperature-dependent microphysical processes by varying the temperature dependence of the yield stress slope. The yield stress components in our models are systematically varied to examine their impact on tectonic style and mantle dynamics.

Parameterisation of the brittle component is based on the proposition that temperature-dependent frictional weakening plays a factor in the tectonic regimes of Earth and Venus. On Earth, where low surface temperatures create a geothermal gradient that keeps much of the crust below 400°C, frictional heating can reduce the friction coefficient at high slip velocities. In contrast, Venus’ elevated surface temperatures maintain a higher friction coefficient, which helps suppress plate tectonics. In deeper lithospheric regions, elevated temperatures favour ductile deformation, which would normally weaken the lithosphere. However, these higher temperatures can also promote grain growth, counteracting dynamic strain localisation and thereby strengthening the rock.

We find that hemispheric temperature differences strongly influence lithospheric strength and deformation on LHS 3844b: the colder nightside allows brittle failure to persist over greater depths, whilst the hotter dayside promotes ductile flow at shallower depths due to a much thinner lithosphere. Importantly, we find that an increased temperature dependence of the ductile yield stress amplifies the hemispheric contrast in the planet's tectonic behaviour.

How to cite: Zarebski, A., Ballmer, M., Meier, T., and Manjon Cabeza Cordoba, A.: Effects of Temperature-Dependent Lithospheric Yield Stress on Ultra-Short Period super-Earth LHS 3844b, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4391, https://doi.org/10.5194/egusphere-egu25-4391, 2025.

The solid surfaces of airless bodies continuously evolve due to bombardment by objects from space and solar wind.  We see evidence of this evolution in the differences in colour between surfaces known to be younger (such as freshly excavated crater rays) and older surfaces.  In a recent publication [1], we presented a new complete catalogue of the Moon’s rayed craters with diameters of 5 km and greater between ±50 degrees of the equator. In ongoing work, we are creating a catalogue of the rayed craters with diameters 2 km and greater on the asteroid 4Vesta. We use these catalogues and a model of impact gardening to examine how quickly the surfaces of large rocky bodies like the Moon and smaller rocky bodies like the asteroid 4Vesta evolve over timescales of years to billions of years.

Here, we present the results of the quantitative analysis of the maturity and composition of the lunar rayed crater population through the lense of diverse remote sensing datasets. Perhaps unsurprisingly, we find that the most charismatic rays have the least nanophase iron (also denoted ‘npFe’; i.e., they are the least mature). More compelling, however, is that the most charismatic rays include diverse and distinguishable mineralogical contrasts, for example, rays in both plagioclase, olivine, and FeO abundances. Further, regardless of whether the mineralogical contrast is high or low (i.e., a dark or bright ray), maturity is suppressed. As rays degrade, they appear more thermophysically and mineralogically homogenous; however, faint thermophysical and mineralogical contrasts can persist longer than it takes regolith to saturate with nanophase iron and disappear into the optically mature background. We demonstrate that comparative analysis of rayed crater populations can help us distinguish the timescale for various space weathering thresholds, such as the destruction of a thermophysical ray, the saturation of nanophase iron, and the homogenisation of mineralogical contrasts.

[1] Ghent, R. R., Costello, E. S., & Parker, A. H. (2024). The Population of Young Craters on the Moon: New Catalog and Spatial and Temporal Analysis. The Planetary Science Journal, 5(4), 89. 

How to cite: Costello, E., Ghent, R., and Tai Udovicic, C.: Colour and Time: The Evolution of Crater Rays on the Moon and the Asteroid 4Vesta, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4563, https://doi.org/10.5194/egusphere-egu25-4563, 2025.

Magma ocean is expected to exist on the dayside surface of tide-locked planets if surface temperature exceeds the melting temperature of typical crust. The strength of ocean circulation is important for horizontal heat transport that may could be observed by JWST. In most previous studies of lava planets, the system is typically assumed to be vigorously convecting and isentropic. This implies a magma ocean depth reaching 10-100 km, determined by adiabat and melting curves. However, ocean circulation was not included in the previous studies. In this study, we simulate ocean circulation on tidally locked lava worlds using more realistic 2D and 3D models developed by ourselves. Our simulation results show that under small internal heat source, the maximum zonal current speed ranges from 0.1 to 1.0 m/s and the magma ocean depth is 100-1000 m, being more than 100 times shallower than that predicted in a fully convecting system. The ocean depth is mainly determined by global ocean circulation rather than by the adiabat and melting curves. We further demonstrate that ocean heat transport strength is consistently smaller than the stellar insolation by 1–2 orders of magnitude. Consequently, the impact of ocean circulation on the thermal phase curve of tide-locked lava worlds should be  small in observations.

How to cite: Yang, J., Lai, Y., and Kang, W.: Ocean Circulation on Tide-locked Lava Worlds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5097, https://doi.org/10.5194/egusphere-egu25-5097, 2025.

Even though surface water is essential for Earth's habitability, the estimates of total amount of water (at the surface and in the deep interior) throughout Earth's evolution vary from 5-15 ocean masses (OM) based on magma ocean solidification models [Hamano et al., 2013] to 1.2-3.3 OM based on petrological studies [Hirschmann, 2006]. Previous numerical models of coupled surface-mantle system have estimated a lower bound of 9-12 OM [Nakagawa et al., 2018]. Experiments have shown that water lowers the melting temperature, density and viscosity of rocks and it is also required for the generation of felsic magmas. In this work, we use global convection models [Tackley, 2008] spanning the age of the Earth to elucidate the effect of water on mantle dynamics in terms of planetary cooling, surface mobility and production of continental crust.

Our models self-consistently generate oceanic and continental (Archean TTGs) crust while considering both plutonic and volcanic magmatism and incorporate a composite rheology for the upper mantle. Pressure-, temperature-, and composition-dependent water solubility maps calculated with Perple_X [Connolly, 2009] control the ingassing and outgassing of water between the mantle and the surface [Jain et al., 2022]. Irrespective of the initial water content used, our models exhibit mobile-lid regime (high surface mobility with subduction) throughout the 4.5 Gyr with episodes of short-lived plutonic-squishy-lid regime (low surface mobility with delamination or dripping) in the Hadean. These models are also consistent with the cooling history of the Earth inferred from petrological observations [Herzberg et al., 2010]. A strong positive correlation is observed between continental crust production and the total amount of water available, with the former's cumulative mass increasing by roughly three times when water in the planetary system is raised from 1 OM to 10 OM.

Models that consider a reduction in the density of crustal and mantle materials in the presence of water exhibit mobile-lid regime for the initial 200 Myr. Afterwards, the mobility stays low as the hydrated oceanic crust is less dense and does not subduct. It thickens over time and eventually collapses as global resurfacing events. Mantle stays comparatively warm and a much lower amount of continental crust is produced. This motivated us to make the following improvements to achieve more realistic models. First, mantle minerals only in the top 5 km of the computational domain (as opposed to 10 km considered previously) are ingassed with water. Second, instead of fully saturating the rocks based on their solubility maps, they are partially saturated to control the input of surface water into the lithosphere. Third, different partition coefficients for water are considered: 0.01 for pyrolite to basalt melting and 0.25 for basalt to TTG melting. These changes help in increasing the surface mobility, cooling down the planet and producing more continental crust. These trends are further amplified in models that additionally consider a viscosity reduction of mantle materials in the presence of water.

How to cite: Jain, C. and Sobolev, S.: Influence of water on global mantle dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5822, https://doi.org/10.5194/egusphere-egu25-5822, 2025.

Ocean on the Earth is a key feature, which is likely responsible for the onset and further operation of plate tectonics as well as for the origin of life. Geochemical data suggests that ocean existed on the Earth already since at least the middle Hadean time. Recent studies also infer that after the solidification of the magma ocean, mean concentration of water in the Earth’s mantle could have been up to few 1000 ppm and that extraction of part of it formed the surface ocean. However, a clear understanding of this process is still lacking.

Here, we report results of modelling of Earth’s evolution during its first 1.5 Gyr with a focus on water cycle and generation of the continental crust. We use geodynamic code StagYY in 2D spherical annulus geometry that generates both basaltic and felsic melts, includes cooling of the core and uses an advanced treatment of water. We also included the effect of water on density of crustal and mantle materials based on experimental data and thermodynamic calculations.

Our models start just after solidification of magma ocean with assumed initial mantle potential temperature of 1900K and core temperature of 5000K. We run models with different initial mean water content in the mantle reaching up to 1500 ppm. In all the models, most of the water is initially concentrated in the mantle transition zone (MTZ), because of its higher water storage capacity. Due to the lower density of the water-containing materials, this leads to Rayleigh–Taylor instabilities and hot and “wet” mantle plumes rapidly rise to the surface. As a result, a large amount of mantle water is outgassed forming the surface ocean in just a few million years. Simultaneously, a significant amount of continental crust is produced. Masses of the produced ocean and continental crust depend on the initial concentration of water in the mantle. For instance, for the initial mean water concentration of 1000 ppm, ocean mass of about 1.5 times recent ocean masses (OM) and continental crust of about 0.7 times present-day continental crust mass (CCM) is produced during 7 Myr. Water outgassing from the mantle dominates during the first 100 Myr till ocean mass reaches about 2 OM. Afterwards, the outgassing by plumes and in-gassing by subduction are mostly balanced with a tendency of the surface ocean mass to decrease with time during the 1.5 Gyr.

Interestingly, in all models, MTZ behaves as a buffer for water cycle and despite it’s high water storage capacity, it’s mean water content mostly remains below 400 ppm, rising to up to 1500 ppm only for the short time periods when a number of cold slabs are resting in MTZ. We will show results from a set of models and compare the model-predicted trace elements ratios with the recent geochemical data.

How to cite: Sobolev, S. and Jain, C.: Models of water cycle and continental crust formation on Earth during Hadean and Eo-Archean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5969, https://doi.org/10.5194/egusphere-egu25-5969, 2025.

The origin and exact nature of the large low seismic provinces (LLSVPs) located beneath Africa and the Pacific are still open questions and highly debated. As these structures are assumed to be at their respective locations for at least a few hundred million years, a thermochemical nature seems highly likely.
We use a 2D double-diffusive mantle convection model to numerically investigate the temporal and spatial stability of thermochemical piles for various rheological parameters. We compare results of the commonly investigated depth dependence of the viscosity (due to pressure and composition) with the effect of the yield stress and variable thermal expansivity. We find that increasing the top or bottom viscosity yields temporally and spatially more stable piles. Similarly, a decreased thermal expansivity with depth also results in slower entrainment of the high compositional material and thus more stable piles. Additionally, the appropriate combination of parameters can counterbalance destabilizing properties such that, for example, structures containing melt can also be long-lived and spatially stable, which would otherwise be quickly entrained due to the low viscosity of melt.
Furthermore, we studied the effect of rheological parameters on the stability of plumes and investigated the location of plumes with respect to thermochemical piles. Our results show a mutual dependency of the plumes and piles. Typically, large plumes are anchored by piles and located in the pile center. However, strong thermal plumes in the ambient mantle can pull along high compositional material. This can lead to the deformation of piles. During this process, or the merging of piles due to strong slabs, plumes are observed at the edges of piles, existing there for several million years before striving to the center of a pile.

How to cite: Sitte, H. W., Weber, C., Stein, C., and Hansen, U.: Numerical Study on Rheological Parameters Affecting the Stability of Thermochemical Piles and Plumes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6256, https://doi.org/10.5194/egusphere-egu25-6256, 2025.

Mineral phase transitions can either hinder or accelerate mantle flow. In the present day Earth, the formation of the bridgmanite + ferropericlase assemblage from ringwoodite at 660 km depth has been found to cause weak and intermittent layering of mantle convection. However, for the higher temperatures in Earth’s past or on other planets, different phase transitions might have governed mantle dynamics and shaped mantle structure. 

Here, we apply a recently developed entropy formulation in mantle convection models with plate-like behavior to investigate the effect of phase transitions on changes in convection style throughout Earth's history. We have extended this method to include chemical heterogeneity, and we have implemented and tested the approach in the geodynamics software ASPECT. Our benchmark results show that this multicomponent entropy averaging method effectively captures the system's thermodynamic effects. Furthermore, we apply the entropy formulation in 2-D and 3-D geodynamic models, incorporating thermodynamic properties computed by HeFESTo. Our models reveal the impact of the endothermic transition from wadsleyite to garnet (majorite) and ferropericlase (occurring between 420–600 km depth and over the 2000–2500 K temperature range) in a mantle with potential temperatures hotter than 1700 K, which impedes rising mantle plumes. 

When encountering this phase transition, the plume conduits tilt significantly, and the plume heads spread out laterally. This change in plume morphology accumulates hot material in the transition zone, spawning secondary plumes.  Partial melt generated within these hot, stalling plumes may lead to chemical differentiation as plume material spreads laterally. On a larger scale, the phase transition can reduce the mass flux of plumes by ~90%. The stalling of plumes creates a long-lasting global hot layer and impedes mass exchange between lower and upper mantle, resulting in global thermal and chemical heterogeneity.

Our models reveal a systematic change in convection style during planetary secular cooling. The wadsleyite to garnet (majorite) + ferropericlase phase transformation only occurs at high temperatures and therefore layering of plumes becomes less frequent and eventually stops as the mantle cools down. This indicates that mantle convection may have been partially layered early in Earth's history, or may be layered today in terrestrial planets with a hotter mantle. As the mantle potential temperature decreases and layering ceases, we observe an increase of surface mobility, suggesting that such a change in convection patterns also affects plate tectonics.

How to cite: Li, R., Dannberg, J., Gassmöller, R., Lithgow-Bertelloni, C., Stixrude, L., and Myhill, R.: How Phase Transitions Impact Changes in Mantle Convection Style Throughout Earth’s History: From Stalled Plumes to Surface Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6598, https://doi.org/10.5194/egusphere-egu25-6598, 2025.

The isotopic compositions of lavas from mantle plumes provide evidence for deep mantle heterogeneities and have been associated with primordial mantle material. However, little is understood about how such material formed during the early stages of planetary evolution. Its origin is typically linked to processes such as the sedimentation of iron-rich phases and crystallization in a primordial magma ocean, or, alternatively, to impacts during the later stages of planetary formation. These processes operated under varying temperature and pressure conditions, likely leading to a depth-dependent composition. Regardless of how it originated, this primordial material is thought to contain higher concentrations of radioactive elements compared to the upper mantle. We aim to address a critical question: how does a compositionally stratified mantle evolve over time under convective motions. These motions reshape the boundaries of chemically distinct domains and promote mixing. Therefore, it is crucial to understand the conditions that allow primordial material to persist at the mantle's base over long timescales, particularly in relation to differences in density and heat production between various mantle components.

To investigate this question, we conducted an in-depth experimental study of convection in a stratified system consisting of two fluids with distinct intrinsic densities and heat production rates. We derived scaling laws that connect the dynamical characteristics of convection to the key dimensionless numbers. These scaling laws, coupled with plausible physical parameters, are then applied to extrapolate the results to planetary mantle convection. We illustrate our approach with a diagram relating the effective partitioning coefficients of iron and that of heat producing elements to the lifetime of the stratified mantle.

How to cite: Limare, A. and Boukare, C.-E.: Dynamics of heat producing elements rich domains in rocky planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8040, https://doi.org/10.5194/egusphere-egu25-8040, 2025.

Nitrogen (N) is the most abundant element in Earth's modern atmosphere, but is extremely depleted in the silicate crust and mantle. The volatile inventory of the bulk silicate Earth shows a well-established N deficit compared to CI chondrites, the primitive meteorites representative of the solar composition. However, it remains unclear whether the formation of the iron-rich core, early atmospheric loss, or a combination of both was responsible for this depletion, partly due to the large extrapolation from low-pressure experiments. Here, we study the effect of core formation on the inventory of nitrogen in a terrestrial magma ocean using laser-heated diamond anvil cells. Under core-forming conditions relevant to Earth-sized planets, we find that N is siderophile (iron-loving), making the core its largest reservoir, notwithstanding that the simultaneous dissolution of oxygen in the core lowers that of nitrogen. A combined core-mantle-atmosphere coevolution model, however, cannot account for the observed N anomaly in the silicate Earth via its core sequestration and/or atmospheric loss during accretion, unless Earth's building blocks had experienced vaporisation processes akin to those accountable for the volatile signatures found in CV-CO chondrites. The terrestrial volatile pattern requires severe N depletion (>99%) on precursor bodies but limited atmospheric loss (<5%), prior and posterior to their accretion to the proto-Earth. We argue that early vapour loss/depletion on Earth's building blocks is the key to establishing our planet's volatile budget.

How to cite: Huang, D., Siebert, J., Sossi, P., Kubik, E., Avice, G., and Murakami, M.: Provenance of Earth’s volatile building blocks inferred from the behaviour of nitrogen during core formation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8161, https://doi.org/10.5194/egusphere-egu25-8161, 2025.

As Earth’s magma ocean solidified, chemical fractionation and physical separation of silicate melt and crystal produced chemical heterogeneity, potentially resulting in the compositional stratification of Earth’s deep mantle. A stratified deep mantle would have prevented advective flux of heat or material between the deep Earth (basal magma ocean (BMO) and core) and the shallow mantle. Therefore, the thermochemical evolution of the Earth hinges on the evolution of the stratified deep mantle. How does this region evolve, especially considering that it is likely underlaid by a radioactively heated BMO and a cooling core? To what extent and in what form would heterogeneity introduced by magma ocean differentiation be preserved in Earth’s mantle over time?

We explored these questions through numerical experiments simulating the evolution of a compositionally stratified, initially solid layer underlaid by a volumetrically heated liquid layer. We model percolation as well as convection driven by density perturbations related to thermal expansion, composition (iron), and melt fraction, using pressure-dependent melting temperatures and density perturbations appropriate for Earth’s deep mantle. We explore a variety of heating rates, stratifications, and material properties.

We find that the evolution of a stratified deep mantle may proceed in two regimes, depending on the competition between the timescales of (1) melt segregation and (2) mantle stirring driven by thermochemical convection.

If stirring is efficient relative to melt segregation, bottom-heating will drive homogenization of a stratified region as heat added to deep material leads to density reduction through partial melting. In this regime, the timescale of homogenization is determined by the time it takes to deliver the energy necessary to reduce the density of the entire deep mantle to match that at the top of the stratified region. Density reduction can be achieved either by thermal expansion or melting; homogenization driven by melting-related density decrease will occur much more rapidly than homogenization driven by thermal expansion. The Earth’s solid mantle following deep mantle homogenization likely had multiple compositionally distinct layers (not including any BMO), which then would have proceeded to mix by entrainment.

If melt segregation is efficient relative to stirring, bottom-heating will still produce partial melt, which will be dense due to the incompatibility of iron and will percolate to the BMO. This process drains incompatible components from the deep mantle to the BMO, with the depleted low-density residue rising in diapirs until the deep mantle is homogenized through depletion. In this case, the Earth is left with a mantle which is more uniform and more depleted than in the stirring-dominated regime, and a thicker BMO.

How to cite: Lark, L., Boukaré, C.-E., Badro, J., and Samuel, H.: Homogenization of Earth’s mantle after magma ocean solidification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8385, https://doi.org/10.5194/egusphere-egu25-8385, 2025.