Water is everywhere on the surface of Earth.  Water is also a key ingredient in geochemical processing of Earth.  Through plate tectonics water is cycled through the mantle and behaves as a flux for production of magmas.  The provenance of water on Earth appears straightforward.  Hydrogen and oxygen are the two commonest elements capable of forming molecules and so water is an expected species in the molecular cloud forming the solar system.  Water on Earth has been ascribed to late stage infall (comets and asteroids) although there are details that are only now being revealed.  Water can be characterised through its abundance, but also through isotopic compositions (D/H, 18O/16O, 17O/16O).

Our instrument of choice for carrying out these analyses is a large-radius secondary ion mass spectrometer, SHRIMP-SI, that was designed and built with water and oxygen isotopes specifically in mind.  The large radius allows high mass dispersion for separation of 16OH from 17O allowing coupled measurements of OH abundance and oxygen isotope compositions.  Much of the development of this instrument centered around excluding atmospheric water contamination, through differentially pumped chambers.  In rocks, water can be present from trace quantities to major contributions (>10 wt%) and so the detection system must be capable of a large dynamic range.  The charge-mode Faraday cup system was developed for this type of analysis.  Finally, the water background from mounting systems had to be controlled.  Epoxy mounts, thin sections, and even indium metal mounts can all show contamination.  Mounting of samples in molten BiSn allows a robust mounting material capable of being repolished and low inherent water background.

Our analytical work has followed two different routes: terrestrial geochemistry and solar system cosmochemistry.  Work in terrestrial samples has ranged from water concentrations in volcanic glasses through to low level water analyses in mantle and lower crustal melts.  But it is in the analysis of extraterrestrial samples where the coupled isotopes and water concentrations allow the greatest insight.  The low-level water concentrations in high-temperature objects like chondrules shows distinct three-oxygen isotope compositions and water concentrations.  

The ultimate question of where did water on Earth come from appears to have been solved through the recent sample return missions of Hayabusa 2 and Osiris REx.  These missions visited C-type asteroids, which were thought to be related to the carbonaceous chondrites.  But the C-type asteroids dominate the main asteroid belt and carbonaceous chondrites are quite rare.  Both Hayabusa 2 and Osiris REx recovered CI chondrite-like material, amongst the rarest subtype of carbonaceous chondrite.  The resolution of the abundance paradox comes down to the friability of the asteroid-return samples.  These materials simply do not survive atmospheric entry.  As such, it is likely that Earth received a large contribution of carbonaceous chondrite material during its formation and ongoing accretion of extraterrestrial material.

How to cite: Ireland, T.: The Provenance of Earth's Water, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7562, https://doi.org/10.5194/egusphere-egu25-7562, 2025.

The geological water cycle (or the deep water cycle) consists of water-rock interactions between the hydrosphere/atmosphere and lithosphere. This water plays a critical role in geological processes, for example, promoting melting and the formation of new continental crust, the mobilisation of economic metals, rock reactivity and rheology, and seismic activity. In the modern day, the most dominant form of the geological water cycle is the uptake of water in mantle-derived rocks in the oceans, and release of this water during subduction to melt overlying lithologies and form volcanic arcs. In the Archean, however, the geological water cycle is less well understood. This is particularly because (i) there are rare ophiolites from this timeframe, and lithologies responsible for water uptake and release may have been different and (ii) because the mode of tectonics is argued, meaning that the geodynamics and therefore conditions of water release are not well understood.

This presentation will focus on the processes of hydration and dehydration of ultramafic to mafic rocks from Archean greenstone belts (komatiites and komatiitic basalts). Geochemical evidence suggests that these rocks were initially hydrated on an Archean oceanic plateau after their eruption. During this process, they sequestered mobile elements such as boron from the seawater, and produced molecular H₂ by the oxidation of Fe, a possible source of energy for early chemosynthetic life. Most greenstone belts have been metamorphosed to greenschist-amphibolite facies, indicating that they experienced some form of burial during Earths earlier history. Phase equilibria modelling shows that if komatiites are buried to higher temperature conditions (>750 °C), the breakdown of hydrous phases could release significant quantities of water into the surrounding rocks, promoting fluid-fluxed melting of surrounding lithologies. In the case of the Barberton Greenstone Belt, which contains ~8 % komatiite and ~20% basalt by volume, fluid release from the komatiite into the basaltic lithology would promote wet melting of basalts to form tonalite-trondhjemite-granodiorite (TTG) series rocks, important constituents of Archean continental crust.  While not abundant in the geological record, the role of ultramafic rocks in the Archean geological water cycle is evident, as is their importance in ocean floor processes and the formation of the Earth’s first TTG crust.

How to cite: Tamblyn, R. and Hermann, J.: The Archean geological water cycle , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13998, https://doi.org/10.5194/egusphere-egu25-13998, 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.

Exposed slivers of mantle rocks are excellent archives for investigating mantle characteristics, post-magmatic alterations such as serpentinization and carbonation, and their role in the genesis of economically significant mineral deposits. The serpentinized harzburgite and dunite pods from the oldest part of the Dharwar Craton, namely, the Holenarsipur Greenstone Belt (HGB) represent a preserved section of Paleo- to Mesoarchean depleted mantle. In situ major and trace element composition of olivine, serpentine polymorphs (lizardite, antigorite, and chrysotile), and bastite reflecting progressive hydration events, resulting in differential assimilation of Fluid Mobile Elements (FME) during serpentinization. Olivine → lizardite breakdown marks high concentration FME (Ce, Rb, Sr, and Ba), whereas, lizardite → antigorite transition exhibits a lower FME (Rb, Sr, and Ba) budget suggesting higher temperatures. Late-stage chrysotile veins (Rb:~1.58 ppm, Sr:~7.36 ppm, and Ba:~5.41 ppm) and serpentinized orthopyroxene (Rb:~1.60 ppm, Sr:~4.30 ppm, and Ba:~5.47 ppm) act as a sink for FME. The LREE-enriched trace element pattern of bastite/orthopyroxene affirms metasomatic refertilization. Thus, the geochemical systematics suggest that HGB harzburgite represents a depleted mantle that has undergone multiple episodes of serpentinization and metasomatism, primarily driven by subduction-derived fluids, contributing to the geochemical heterogeneities of the Archean mantle. In addition, these findings highlight the replenishment of an Archean depleted mantle reservoir beneath the Western Dharwar Craton (WDC).

The carbon (δ¹³C_VPDB = avg. -2.20 ‰) and oxygen (δ¹⁸O_VSMOW = avg. 28.50 ‰) isotope studies of ultramafic hosted vein-type magnesite mineralization from the HGB suggest late-stage supergene enrichment at shallow to surface level conditions under ambient temperature (~35^oC). Precipitation of magnesite by the interaction of atmospheric carbon-enriched mineralizing fluid with weathered ultramafic rocks indicates the sequestration of atmospheric CO₂ during the carbonation of serpentinized mantle rocks in the HGB.

How to cite: G Panicker, A. and Mohan, M. R.: Fingerprinting serpentinization and carbonation of mantle rocks from the Paleo-to-Mesoarchean Holenarsipur Greenstone Belt, Western Dharwar Craton, Southern India: Implications on mantle metasomatism and supergene magnesite mineralization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3588, https://doi.org/10.5194/egusphere-egu25-3588, 2025.

How to cite: Yang, A. Y., Zhao, S., Zhang, S., Langmuir, C., Zhou, Z., Tamura, Y., Ma, J., Xu, Y., and Zhao, T.: The role of slab serpentinite and lower crust in deep water cycles: Insights from B-Sr isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5047, https://doi.org/10.5194/egusphere-egu25-5047, 2025.

Serpentinization, a low-temperature hydrothermal alteration of ultramafic rocks, strongly influences the physical and chemical properties of the oceanic lithosphere. Complete serpentinization significantly decreases the density, yield strength, and seismic velocities of ultramafic rocks, which may result in a great increase in volumes.  Serpentinites are enriched in H₂O, up to 13.5 wt%, and they contain much higher amounts of volatiles (such as carbon, sulfur, and nitrogen) compared to olivine. In particular, serpentine minerals can be stable at great depths, >150 km, suggesting that serpentinization may play an important role for the transferring of H₂O and other volatiles into great depths in subduction zones.

In spite of the significance of serpentinization, the proportions of serpentine in subduction zones still remain poorly constrained. Serpentinization kinetics are important parameters for quantifying the percentage of serpentine in subduction zones. The kinetic data obtained by Martin and Fyfe (1970) have been used to estimate the proportions of serpentine, <5% in subduction zones, which suggests that the distribution of serpentine in subduction zones is strongly affected by serpentinization kinetics. The kinetic data of Martin and Fyfe (1970) were derived from experiments using synthetic forsterite. In recent years, serpentinization experiments were performed using natural olivine, which has rates of serpentinization around 1-2 orders of slower compared to synthetic forsterite (Malvoisin et al., 2012; McCollom et al., 2016).

We have experimentally studied the kinetics of peridotite and olivine serpentinization at temperatures of 300-500 °C and pressures of 3.0-20 kbar. Compared to olivine, peridotite is serpentinized at much faster rates, reflecting the effect of pyroxene and spinel. At relatively high temperatures, e.g., 400-500 °C and 3.0 kbar, the kinetics of olivine serpentinization are sluggish, due to positive Gibbs energies of olivine serpentinization under such T-P conditions. In contrast, the kinetics of peridotite serpentinization under these T-P conditions are much faster. At 500 °C and 20 kbar, complete serpentinization can be achieved within a short period (e.g., 20 days). This suggests that the proportions of serpentine in subduction zones may be mainly controlled by the presence of H₂O rather than the rates of serpentinization. With the presence of enough H₂O, the percentage of serpentine in subduction zones may be much higher than previously proposed.

References:

Huang, R. F. et al. (2017) Journal of Geophysical Research: Solid Earth, 122, doi:10.1002/2017JB014231.

Huang, R. F. et al. (2023). Journal of Geophysical Research: Solid Earth, https:doi.org/10.1029/2022JB025218.

Malvoisin, B. et al. (2012). Journal of Geophysical Research: Solid Earth, 117(B4), B04102, doi: 10.1029/2011JB008842

Martin, B. & Fyfe, W. S. (1970). Chemical Geology, 6, 185‒202.

McCollom, T. M. et al. (2016). Geochimica et Cosmochimica Acta, 181, 175-200.

How to cite: Huang, R., Sun, W., Li, W., and Shang, X.: Effect of temperature, pressure, and chemical compositions of fluids on the rates of olivine and peridotite serpentinization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5559, https://doi.org/10.5194/egusphere-egu25-5559, 2025.

The global transition to a low-carbon energy future has ignited interest in hydrogen as a clean and versatile energy carrier. NW Saudi Arabia contains vast tracts of mantle-dominated Neoproterozoic ophiolites overlain by a sedimentary cover in the north, NE and east. Our research explores the untapped potential of Saudi Arabia’s ophiolite serpentinites as a possible source of hydrogen generation through serpentinization and related processes. H2 is commonly derived from serpentinization, which primarily involves the hydration of minerals rich in iron and magnesium (e.g., olivine), resulting in the formation of serpentine and H2. Serpentinites are formed by reaction between hydrothermal fluids and mantle rocks, and hydrogen and methane are released in extreme reducing conditions. Under strongly reducing conditions, the formation of magnetite generates hydrogen during serpentinization, following reactions such as: 3Fe2SiO4 + 2H2O = 2Fe3O4 +3SiO2 +2H2. We have conducted a comprehensive assessment of serpentinites in the Arabian Shield, employing the Geographic Information System (GIS) to locate Arabian ophiolites with the largest ultramafic segments. Ophiolites studied include Jabal Ess, Jabal Wask, Bi’r Tululah, and Jabal Tharwah. After ophiolite identification, we delineated fractures and measured fracture density to provide insight into the potential of serpentinite fractures on the amount of possible hydrogen seepage, or natural accumulation in case of an overlying seal. Our goal is to do spatial analysis that can be a guide to the most favourable environment for geologic H2 exploration; as such, this does not however, provide an estimate of the total H2 storage capacity. A complimentary H2 anomaly survey however, will ground-truth the results of this study.

Keywords: serpentinite, hydrogen, serpentinization, Ultramafic rocks, Arabia

How to cite: Saidy, K., Fawad, M., and Whattam, S.: Unlocking the H2 potential in Saudi Arabia: Exploring serpentinites as a source for H2 production, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7909, https://doi.org/10.5194/egusphere-egu25-7909, 2025.

In recent years, iron isotopes have found increasing applications across various fields of Earth Science, including cosmochemistry, geochemistry, and environmental sciences. Isotopic reference materials play a crucial role in advancing and refining non-traditional stable isotope systematics, ensuring accurate and precise isotope ratio analyses. Consequently, the direct comparison of data obtained from different laboratories is an essential prerequisite for developing reliable systematics

In the framework of the project “TEOREM - Deciphering Geological Processes using Terrestrial and Extraterrestrial ORE Minerals” (PRIN-MUR 2017AK8C32) and the project ITINERIS ISOTOPE VRE (IR0000032; PNRR; Next Generation EU), we developed the methodology for the Fe separation from different matrices, and the determination of Fe isotope ratios using High Resolution Multi-Collector Inductively Coupled Plasma Mass Spectrometer (HR-MC-ICPMS).

We investigated the iron isotopic composition of a new potential iron isotope reference material, IAEA-B5. Additionally, high-precision stable Fe isotope data for widely used international reference materials (JB-2, BHVO-2, BE-N, AGV-1, and RGM-1) were obtained using a HR-MC-ICPMS Neptune Plus at the Radiogenic and Unconventional Stable Isotopes Laboratory of IGG-CNR (Pisa, Italy).

The data obtained for selected igneous reference materials, ranging from basalts to andesite and rhyolite, show strong agreement with previously published values and remain within the stated analytical uncertainties. The newly certified iron isotope composition values for the IAEA-B5 standard, determined in our laboratory, are δ⁵⁶Fe = 0.105 ± 0.061 (2SD) and δ⁵⁷Fe = 0.147 ± 0.071 (2SD). These values are consistent with the averages of other basaltic reference materials.

How to cite: Vezzoni, S., Di Giuseppe, P., Rielli, A., Iannini Lelarge, S., Agostini, S., and Dini, A.: Iron isotopic analyses of geological reference materials on MC-ICP-MS: proposal for a new Fe isotope standard IAEA B5, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8541, https://doi.org/10.5194/egusphere-egu25-8541, 2025.

The U–Th–Pb system is a potential impactful tracer of fluid sources and pathways in the continental crust. Different rock types exhibit distinct U/Th/Pb ratios, and within a single rock, heterogeneities arise from different minerals having different U, Th and Pb contents. These differences result in distinct Pb isotope compositions over time, at the scale of mineral to whole rock. Fluids circulating in the continental crust thus inherit different Pb isotope ratios upon interaction with different rocks along their pathways. Feldspars dominate the granitic continental crust and typically contain tens of µg/g of Pb but negligible U or Th, and thus they retain their primary Pb isotope composition. However, feldspars are also readily altered by fluid–rock interaction processes, and they incorporate the Pb isotope composition of fluids with which they interact. Such modified feldspars can thus provide information on the nature of crustal fluids.

This concept is applied to feldspars in post-Variscan mantle-derived granitoids from the Aar Massif (central Swiss Alps). In this setting, fluids circulated during Permian and Mesozoic rifting, and during the (Miocene) Alpine orogeny. The combination of Pb–Sr–O–H isotope data in hydrothermal epidote revealed that Permian and Miocene fluids had external sources and exploited various pathways to infiltrate the granitoids. Triassic seawater infiltration was inferred from biotite Rb–Sr data.

Feldspar grains were separated from the granitoids, and subsequently leached to remove alteration minerals until they appeared transparent. Feldspar Pb isotope ratios were measured by solution MC-ICP-MS after acid digestion and ion exchange chromatography. The Pb isotope ratios in these leached feldspar fractions, reported here as ²⁰⁷Pb/²⁰⁶Pb ratios of 0.8249–0.8050 and ²⁰⁸Pb/²⁰⁶Pb ratios of 2.042–2.021 for direct comparison to LA-ICP-MS data of fluids, are more radiogenic than model values at the time of granitoid emplacement (ca. 300 Ma). This is attributed to post-magmatic processes resetting Pb isotope ratios of feldspars. This hypothesis is explored further by comparing the Pb isotope ratios of feldspars to that of Permian (²⁰⁷Pb/²⁰⁶Pb = 0.8326–0.8296; ²⁰⁸Pb/²⁰⁶Pb = 2.064–2.051) and Miocene fluids (²⁰⁷Pb/²⁰⁶Pb = 0.8118–0.7308; ²⁰⁸Pb/²⁰⁶Pb = 2.021–1.904), and to the Pb isotope evolution of the granitoids (whole rocks) from their emplacement until the present day.

The agreement of feldspar Pb isotope data with those of Permian and Miocene fluids suggests that the fluids altered the initial Pb isotope ratios of feldspars, imparting a more radiogenic composition. However, the overlap of feldspar Pb isotope data with the Pb isotope evolution of the granitoids suggests that the Pb isotope composition of feldspars includes components inherited by redistributing Pb mobilized from variably U-/Th-enriched phases within the granitoids themselves. This suggests that the local, fluid-induced heterogeneities in Pb isotope ratios within the studied feldspars result from fluid-induced redistribution of Pb originating from the granitoids themselves, rather than by fluid-mediated addition of externally derived Pb. This hypothesis has implications for our understanding of Pb sources and redistribution – with possible enrichment into ore deposits – in the granitic continental crust.

How to cite: Peverelli, V., Chew, D., Mezger, K., Wille, M., Berger, A., and Herwegh, M.: Lead isotopes in feldspars trace fluid circulation in deforming granitoids , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10459, https://doi.org/10.5194/egusphere-egu25-10459, 2025.

Garnet U-Pb dating by laser ablation – multicollector – inductively coupled plasma – mass spectrometry (LA-MC-ICPMS) in metamorphic rocks allows constraining the main stages of tectonic thickening during orogenesis. Dates obtained from garnet generally record prograde growth or the baric peak, attained during the tectonic stacking. This is of great importance because accessory minerals, such as zircon, usually analysed in metamorphic rocks date thermal peaks (or retrograde cooling) rather than prograde metamorphism and commonly constrains exhumation rather than tectonic thickening. In addition, the exact significance of the geochronological information obtained from these accessory minerals, however, is difficult to determine. Within this communication, we will explore the chronological differences between garnet and zircon from several metamorphic rocks, such as UHP gneisses, eclogites or granulites. This technique has the potential of providing time constraints of the earliest stages of continental collisions and of the dynamics of arc systems. These findings have a considerable impact on unravelling the timing of orogenic tectonothermal evolutions and supercontinent assemblies.

How to cite: Albert, R., Millonig, L. J., Beranoaguirre, A., Gerdes, A., Marschall, H. R., Moreno-Martín, D., Díez Fernández, R., Sánchez Martínez, S., and Arenas, R.: In-situ garnet U-Pb dating of metamorphic rocks: Exploring geochronological differences between garnet and accessory minerals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12008, https://doi.org/10.5194/egusphere-egu25-12008, 2025.

The Eo-Oligocene Adamello plutonic complex (Southern Alps) has been mapped and studied for over a century. The NW unit, Avio granodiorite, was recently reexamined by [1], who observed that magmatic biotite gave constant ³⁹Ar-⁴⁰Ar ages for four grainsizes between 71 and 1000 µm. We dated zircon [2] and micas from two plutonic masses in the E of the massif, near the crustal-scale Giudicarie Fault. The smallest unit, Sòstino, had been least well studied. It is the oldest pluton of the entire complex (c. 45 Ma zircon ages, [2]), intruded at about 10 km depth. Its biotite (38-39 Ma by Rb–Sr and K–Ar [3]) was sampled anew and studied in detail. We obtained electron microprobe element maps and analyzed two size fractions by ³⁹Ar-⁴⁰Ar stepheating. The "isochemical" [4] age is 38.81±0.03 Ma. In contrast to the size-independent ages of Avio biotites, the 125-250 µm sieve fraction is 0.5 Ma younger than the 250-500 µm fraction, and has a different Ca-Cl-K signature; both K contents are sub-stoichiometric. Two mica generations are inferred, with the smaller fraction lying on the high-Cl-low-age alteration trend of the large fraction. The microprobe maps confirm chloritization, Ti unmixing, local Ba enrichment, and patchy Fe/Mg heterogeneity. The neighbouring Corno Alto pluton has a higher age gap (c. 43 Ma zircon ages, [2]; 33-34 Ma Rb–Sr and K–Ar biotite ages [3]). We followed the same redundant petrochronological approach as for Sòstino. The biotite "isochemical" [4] age is 35.88±0.04 Ma. The fine grainsize is 2 Ma younger than the coarse one, its Ca-Cl-K signature is distinct, both K contents being substoichiometric. The two biotite generations are texturally very clearly identified by microprobe, with correspondingly evident Ti-Ba-Fe-Mg-K compositional differences. The larger age difference between size fractions, and the larger zircon-biotite age gap, are explained by the higher mass fraction of the secondary biotite generation in Corno Alto relative to Sostino. The fluid-controlled formation of secondary biotite may be related to the hydrothermal circulation surrounding the large, younger intrusions in the N and NW. The plutonic biotite samples are c. 20 Ma younger than the basement biotite ages near and far from the plutons.

[1] Mittempergher et al, J Geol Soc 179 (2022) 2021-101 – [2] Favaro S., Resentini A., Tiepolo M., Malusà M.G., Zanchetta S. (2024) Abstract EGU24-14975 – [3] Del Moro et al, Mem Soc Geol It 26 (1983) 285 – [4] Müller et al, Contrib Miner Petrol 144 (2002) 57-77

How to cite: Villa, I. M., Favaro, S., Malusà, M. G., Resentini, A., and Zanchetta, S.: Post-magmatic hygrochronology of plutonic micas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12066, https://doi.org/10.5194/egusphere-egu25-12066, 2025.

In situ geochronology using laser ablation is essential for integrating microstructural and chemical records of minerals with their geochronological information. The in situ method is especially important for potassic mica, which readily deforms, often define rock structures and fabrics, and are susceptible to chemical modification by reactive fluids. In situ ⁴⁰Ar/³⁹Ar geochronology of mica has been widely used for decades and in situ Rb/Sr geochronology has recently emerged as a prevalent method. In contrast, in situ K/Ca geochronology has been demonstrated, but the method has not been refined or utilized. Combined in situ K/Ca and Rb/Sr geochronology was developed at the Fipke Laboratory for Trace Element Research (University of British Columbia, Okanagan), allowing direct comparison of the two isotopic systems and exploring the potential of K/Ca dating. The methodology was tested using two-mica leucogranites and migmatitic paragneisses from the central Seve Nappe Complex (SNC), comprising remnants of Baltican continental crust in the Scandinavian Caledonides. The central SNC consists of continental crustal rocks hosting volumetrically-subordinate eclogites, peridotites, and pyroxenites. The crustal lithologies record partial melting beginning at c. 484-480 Ma, while the (ultra)mafic lithologies provide evidence for high-pressure metamorphism at c. 460-454 Ma, altogether reflecting subduction-exhumation cycles of the central SNC. Subsequent collision of the Baltican continent with Laurentia led to widespread deformation and metamorphism in the SNC, starting at c. 430-425 Ma. Continental anatexis produced the studied leucogranites and migmatitic paragneisses; these rocks comprise quartz, white mica, biotite, plagioclase, K-feldspar, and clinozoisite, with accessory apatite, monazite, xenotime, and zircon. The accessory phases were dated via in situ U-Pb geochronology to compare with in situ white mica and biotite K/Ca and Rb/Sr geochronology results. The dates yielded by apatite (424 ± 15 Ma, 428 ± 17 Ma), monazite (427 ± 2 Ma), and xenotime (426 ± 2 Ma) are all within uncertainty (pooled age of 426.5 ± 1.4 Ma) and record the timing of continental collision. Zircon provide a wider range of concordant U-Pb dates (473 ± 8 Ma to 419 ± 5 Ma). White mica and biotite Rb/Sr isochron dates from all four examined rocks (438 ± 5 Ma, 430 ± 4 Ma, 433 ± 4 Ma, 431 ± 5 Ma) are slightly older than the apatite/monazite/xenotime and youngest zircon U-Pb dates, but still record continental collision. The same mica volumes yielded older K/Ca isochron dates (484 ± 21 Ma, 482 ± 14 Ma, 486 ± 15 Ma, 486 ± 12 Ma), similar to the oldest concordant zircon U-Pb dates and the overall timing of partial melting in the broader central SNC crustal rocks. The different K/Ca and Rb/Sr dates indicate that these two isotopic systems are decoupled in the same mica volumes, controlled either by interactions of Ca and Sr with the mica lattice or by diffusion gradients influenced by bulk rock composition. The results presented herein demonstrate that the K/Ca isotopic system has the potential for retrieving older geologic histories in polymetamorphic terranes. Further detailed investigations and continued development of the methodology, including improved reference materials, are required.

How to cite: Barnes, C., Larson, K., Button, M., and Camacho, A.: Combined in situ K/Ca and Rb/Sr geochronology of potassic mica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14442, https://doi.org/10.5194/egusphere-egu25-14442, 2025.

Natural hydrogen, or white/gold hydrogen, can potentially be a key factor in the energy transition to mitigate climate change and many exploration efforts are underway in various part of the globe. Yet, in continental settings where its exploitation would be easiest, the hydrogen cycle is poorly constrained. Most of the hydrogen produced naturally is through the oxidation of Fe in silicates due to the hydration of iron-rich rocks at depth, either ultramafic rocks or banded iron formation (BIF). Nevertheless, the fluid responsible for the alteration of such rocks is usually assumed to be pure water, which is an oversimplification of fluid-rock interaction processes. Here I present the results of reaction path thermodynamic modeling of successive interactions of an initial meteoritic fluid with different rocks that would compose the upper crust in a continental setting, i.e., granites, quartzites, carbonates and evaporites, which is then reacted with ultramafic rocks.

Thermodynamic modeling was computed at 300 °C and 5 kbar using the DEW model and the EQ3/6 package. Meteoritic fluid (initial concentrations set at 10^-6 molal (mol/kg) of water for all dissolved elements, except Cl at 0.1 molal and 5 molal for evaporites) after the first interaction had higher dissolved Na, K, Fe, Al and Si after interacting with granites than the other three lithologies, although Si was also high after interaction with quartzites. Dissolved C, Ca and Mg were higher after interaction with carbonates and evaporites. These fluids were then reacted with 861 compositions of ultramafics spanning the entire range of Ol-Opx-Cpx compositions. Maximum serpentinization degree was always achieved for peridotite composition intermediate in Ol-Opx, reaching about 45-50 vol% for fluids that interacted with granites or quartzites, while only reaching 20-25 vol% for fluids having interacted with carbonates and almost no serpentinization for fluids having interacted with evaporites. Magnetite and H₂ content were coupled for all settings but were decoupled from serpentinization degree, with highest contents of H₂ produced for low dunitic initial peridotite compositions. The maximum amount of H₂ produced was 0.1 molal for fluids interacted with granites, quartzites and carbonates, an order of magnitude higher than for fluids that interacted with evaporites.

The above results highlight the vital importance of taking into account the actual chemistry of fluids that are responsible for the serpentinization of ultramafic bodies in continental settings. Especially, the presence of evaporites in sedimentary sequences, for example in the widely studied Pyrenees could hamper the natural production of hydrogen. Thus, further exploration of areas of economic importance for natural hydrogen production should carefully map the lithologies in contact with doing fault that are believed to be the carrier of surface fluid toward peridotite bodies at depth.

How to cite: Siron, G.: The impact of the upper crust composition on the production of natural hydrogen during serpentinization in continental settings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18059, https://doi.org/10.5194/egusphere-egu25-18059, 2025.

Serpentinization of ultramafic rocks results from relatively low-temperature metamorphic reactions and is associated with the generation of natural hydrogen. Ocean opening at magma-poor rifted margins occurs under relatively cold conditions and provides a window of opportunity for the emplacement of shallow peridotites, firstly beneath thinned continental crust in the hyperextended distal margin, and secondly in the subsequent oceanward exhumed mantle at the continent-ocean transition [COT] before oceanic spreading is established. The domain covering both the distal margin and the COT is substantial, and interpretation of seismic data suggests that a variable width band of about 100 km of exhumed mantle persists along both conjugate margins of the southern North Atlantic. This raises questions about how much hydrogen has been produced in the past, how much is currently accumulated under sedimentary successions and, finally, the current hydration state of the shallow mantle in order to assess its potential as an energy source to produce additional hydrogen via stimulation. The occurrence of serpentinization and hydrogen generation in the lherzolitic rocks at magma-poor margins depends on the presence of suitable thermodynamic conditions in terms of pressure and temperature, as well as access to water. The latter requires the embrittlement of the rifted margin crust, which also depends on the rheological properties of the mantle and continental rocks, the thermal regime, and the tectonic stresses. The sequence of mantle upwelling in the distal margin and the COT, and how it is related to the deposition of sedimentary layers is also of key importance, as sediment provides a blanket of low-permeability that may promote trapping and profoundly affects the patterns of hydrothermal circulation and so the temperature field. Temperature is a key factor as it modulates the thermodynamics of serpentinization, as well as the 120ºC isotherm, which is relevant to the limits of life that can lead to biological hydrogen consumption. Thus, extension rates in rifted margins strongly control the onset of magmatism and the serpentinization of the shallow mantle beneath the hyperextended thinned continental crust and the COT. By coupling a geodynamic model with thermodynamic calculations, we discuss the above effects, focusing on the sensitivity of serpentinization and molecular hydrogen generation in the distal margin and the COT to spreading rates as control factor. Simulations indicate that at full spreading rates of 15–20 mm.yr^-1 past hydrogen generation is likely to reach its optimal conditions, whereas spreading at 30 mm.yr^-1 has less opportunity for the presence of shallow serpentinized mantle and hydrogen production, marking the transition to faster spreading styles.

How to cite: García-Pintado, J. and Pérez-Gussinyé, M.: Tectonics, Serpentinization and Natural Hydrogen Generation at the Continent-Ocean Transition in Magma-poor Rifted Margins, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18575, https://doi.org/10.5194/egusphere-egu25-18575, 2025.

The hydrothermal alteration of the Fe²⁺- rich mantle peridotites (serpentinization) tectonically exhumed at the Earth’s surface is associated to the oxidation of Fe²⁺ to Fe³⁺ that in turns creates reducing conditions characterized by the formation of hydrogen, native metals and uncommon minerals like Fe–Ni alloys and sulfides. Opaque mineral assemblages in serpentinized peridotites offer key insights into these redox reactions, capturing changes in hydrogen/oxygen and sulfur fugacity, thus allowing to unravel the mechanisms governing fluid-rock interactions and their broader impact on geochemical cycles.

Oman Drilling Project Hole BA3A (International Continental Drilling Program) recovered ~300 meters of harzburgite, with subordinate dunite in the upper 180 meters. BA3A peridotites are intersected by minor gabbroic and clinopyroxenitic dikes. Alteration is pervasive and extensive, primarily focused around dikes and veins, where it forms distinct alteration halos. Serpentine is the dominant alteration mineral within the peridotites. The opaque mineral assemblage in Hole BA3A includes pentlandite ((FeNi)₉S₈), magnetite, awaruite (Ni₂Fe), heazlewoodite (Ni₃S₂), native copper, and covellite (CuS). Sulfide minerals are primarily located within the serpentine groundmass or serpentine veins and are rarely found within pyroxene. This spatial distribution suggests that most sulfides formed as secondary phases. In highly serpentinized samples, sulfides are often finely dispersed as grains smaller than 2 μm within the serpentine groundmass. Pentlandite, the most abundant sulfide mineral, is commonly associated with magnetite and awaruite, with minor occurrences of heazlewoodite. Magnetite is frequently observed within the cleavage planes of pentlandite, as narrow rims along its edges, or in association with awaruite as thin veins. Pentlandite is also closely associated with native copper. Covellite forms banded rims around pentlandite, native copper, and magnetite. Magnetite is widespread, occurring as intergrowths with pentlandite, as fine grains (<2 μm) in the centers of serpentine veins, as fine-grained veins cutting through the mesh texture, and as overgrowths in fully serpentinized samples. Thermodynamic modeling indicates that, except for covellite—formed at low aH₂ and high aH₂S—sulfides like pentlandite, heazlewoodite, native copper, and magnetite are stable under high aH₂ conditions. We propose that the observed Cu-bearing assemblages has formed at temperatures below 200°C under highly reducing conditions which is consistent with serpentinization.

How to cite: Eslami, A., Malvoisin, B., and Godard, M.: Opaque mineral assemblages indicate highly reducing conditions in Oman Drilling Project Hole BA3A, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18636, https://doi.org/10.5194/egusphere-egu25-18636, 2025.

       Mercury (Hg), a highly volatile metal, is capable of tracing volcanism through geological history as LIP events transiently emit large amounts of Hg. There are two indicators that make Hg a unique tool for geochemistry, the Hg to total organic carbon ratio (Hg/TOC) and mass-independent fractionation (Hg-MIF, defined as Δ¹⁹⁹Hg). Owing to the affinity of Hg to organic matter, anomalous high Hg/TOC ratios in sediments can better reveal large volcanic eruptions. The anomaly of Hg-MIF is mainly observed in Hg photoreactions, providing a fingerprints of specific reaction pathways of Hg. Volcanic Hg usually has Δ¹⁹⁹Hg ~ 0, but photochemical processes in the surface environment can alter this signal, resulting in positive Δ¹⁹⁹Hg in marine systems (e.g., seawater and marine sediments) and negative Δ¹⁹⁹Hg in terrestrial systems (e.g., soil and vegetation).

         Here, we examined the Hg records in Ediacaran cap carbonates in South China and Upper Cretaceous oceanic red beds (ORBs) in southern Tibet and the North Atlantic, to obtain their sedimentary material sources and the cause of the termination of Marinoan glaciation and Cretaceous oceanic anoxic events.

       (1) The cap carbonates show higher Hg concentrations (4.9 to 405 ppb), most of which are comparable to that observed in carbonates deposited during non-LIPs periods. The lack of Hg/TOC anomalies in these cap carbonates suggests that background volcanic activity, rather than a short-term large igneous province event, drove the Marinoan deglaciation. The cap carbonates show positive Δ¹⁹⁹Hg values (0.18 to 0.34 ‰) in slope settings and slightly negative to slightly positive Δ¹⁹⁹Hg values (0.16 to 0.11 ‰) in shelf settings, suggesting a binary mixing of seawater- and terrestrial-derived Hg in early Ediacaran Ocean. We infer that the accumulation of greenhouse gases, due to ongoing volcanic emissions of CO₂ and enhanced release of gas hydrates, triggered global warming. This warming led to melting of sea ice cover, enhanced terrestrial inputs, and large-scale dissolution of atmospheric CO₂ into seawater, driving widespread deposition of Ediacaran cap carbonates.

       (2) In southern Tibet and the North Atlantic, black/gray shales (typical deposition of oceanic anoxic events) show much higher Hg concentrations and Hg/TOC values than ORBs, indicating enhanced Hg flux to global oceans during time of black/gray shale deposition. Black/gray shales show lower Fe³⁺/Fe²⁺ and positive Δ¹⁹⁹Hg, suggesting a significant input of Hg into the anoxic/dysoxic ocean via atmospheric deposition. The isotope values are consistent with a volcanic source for this excess Hg. ORBs show high Fe³⁺/Fe²⁺ and negative shifts of Δ¹⁹⁹Hg, suggesting that the dominant source of Hg into the oxic oceans was via terrestrial runoff. These results suggest that volcanism was an important driver of the climate/ocean dynamics during the Late Cretaceous.

       To sum up, in addition to indicating short-strong volcanic activities, Hg can also trace the source of sedimentary materials under weak magmatism. Moreover, Hg offers a more accurate depiction of the interactions and exchanges among the Earth’s atmosphere-ocean-land system.

How to cite: Sun, R. and Yin, R.: Mercury Isotope Geochemistry in Ediacaran Cap Carbonates and Cretaceous Oceanic Red Beds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-167, https://doi.org/10.5194/egusphere-egu25-167, 2025.

The Balearic Promontory (BP) is a NE-SW oriented continental block located in the centre of the Western Mediterranean that corresponds to the northern prolongation of the Betic-Balearic front. The BP represents a unique case study, as it records two distinct compressive periods from the Alpine orogeny, as well as exhibits evidences of volcanism and back-arc extension related to the opening of the Western Mediterranean. Mallorca is the only island of the BP that preserves an almost complete Cenozoic sedimentary record, which encompasses a significant shift in the geodynamic evolution, evolving from northern derived deposits during the Paleogene (“Catalanide-Pyrenean”) to a southern source area during the Early Miocene (“Betic”). As both source areas currently correspond to marine basins, the Cenozoic detrital deposits therein represent the only remnants whose provenance study can contribute to decipher the hinterland tectonic evolution. Nevertheless, the majority of these deposits are carbonate-dominated, and thus, techniques such as detrital geochronology and thermochronology may prove useful in instances where traditional provenance analysis are challenging. The present study seeks to provide a new perspective on the provenance evolution of Mallorca for the first time from two different timings and settings. By using detrital zircon (DZ) double dating we characterized the Paleogene and Neogene provenance and exhumation history. Our findings suggest an evolution from predominantly Mesozoic-derived DZ during the Paleogene, to a mixed Mesozoic and late Palaeozoic DZ during the Neogene. The presence of only two Eocene ZHe ages in early Miocene DZ may suggest a gradual exhumation process within the hinterland rather than a fast dismantling related to the “Betic” compression. Furthermore, the identification of Oligo-Miocene aged zircons related with synsedimentary volcanism enabled us to establish a maximal depositional age (MDA) for some samples, thus providing a more precise chronostratigraphic constraint.

How to cite: Peris, S., Griera, A., Gómez-Gras, D., Roigé, M., Stockli, D., and Teixell, A.: Reconstructing the Cenozoic provenance evolution of Mallorca (Balearic Promontory):  insights from detrital zircon U-Pb and (U-Th)/He double-dating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-962, https://doi.org/10.5194/egusphere-egu25-962, 2025.

Quartz optically stimulated luminescence (OSL) sensitivity as well as some electron spin resonance (ESR) and cathodoluminescence (CL) signals have been empirically proposed as provenance indicators. Sensitivity is defined as luminescence emitted in response to a given dose per unit mass. While it is largely believed to be acquired by earth surface processes, recent studies bring evidence that sensitisation processes depend on source geology.
Here we combine OSL and thermoluminescence (TL), ESR and CL analyses to understand the mechanisms of quartz OSL sensitisation. We investigate granites and their derived sediments from catchments draining simple lithologies of known age that display contrasting OSL sensitisation behaviour both in nature and during irradiation and light exposure laboratory experiments. The sample displaying increased OSL sensitisation is characterised by TL emission at intermediate temperatures (150-250 °C), Ti-related signals in CL, and Ti and Ge lithium compensated signals in ESR. The insensitive samples either lack or exhibit very weak such characteristics and contain several times less amount of trace titanium measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).
We demonstrate that the OSL sensitisation results as an effect of the existence of certain defects and impurities in the quartz crystal in the parent rock, such as titanium and germanium. However, the degree of sensitisation reached in nature is significantly higher than in the laboratory.  As such, the existence of this precursor represents the potential for sensitisation, which can later be amplified by environmental factors during sedimentary history.

This study is funded by the European Research Council Consolidator Grant - PROGRESS, (ERC-CoG-101043356) awarded to Prof. Alida Timar-Gabor. 

How to cite: Constantin, D., Dave, A., Grecu, Ș., Kabacińska, Z., Antuzevics, A., Barla, A., Urdea, P., Ducea, M., and Timar-Gabor, A.: Tracing quartz provenance: a multi-disciplinary investigation of luminescence sensitisation mechanisms of quartz from granite source rocks and derived sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1479, https://doi.org/10.5194/egusphere-egu25-1479, 2025.

Provenance Characteristics and Tectonic Implication of the Laiyang Group in Lingshan Island of Riqingwei Basin

JIANG, Yushen and ZHOU, Yaoqi, China University of Petroleum (east)

Abstract: Lingshan Island is located on the suture zone of the Sulu orogenic belt and is an important research area of the Riqingwei Basin. There are turbidites of Laiyang Group of Lower Cretaceous, terrigenous clastic rocks of Qingshan Group and igneous rocks in Lingshan Island from top to bottom. There are significant debates about the sedimentary environment, sediment source, and provenance direction of the Laiyang Group sedimentary strata in the Lingshan Island. The stratigraphic features of Lingshan Island section are investigated in detail and analyzed by various methods, and the following conclusions are drawn:

(1) Analysis of the sandstone detrital components has shown that the predominant rock type in the study area is lithic feldspathic sandstone with overall low maturity, and the grain composition of sandstone shows that the source rocks may have the characteristics of volcanic rocks, granite and metamorphic rocks. The sedimentary source of the Laiyang Group sandstones in Lingshan Island is relatively close with a short transportation distance and fast sedimentation rate, and is mainly from the cutting of arc-island region, which is affected by tectonic uplift to some extent.

(2) The results of paleocurrent analysis show that the ancient water flow in Lingshan Island area is generally oriented in the northwest-southeast direction with an average azimuth of 160 °, suggesting that the sandstone deposits in the study area mainly come from the northern provenance.

(3) Analysis of the principal and trace elements in mudstone has revealed that, from bottom to top, there is a trend of change in properties of the source rock from felsic to intermediate, and a trend of decreasing weathering in the source area; The provenance mainly comes from felsic source area, and the overall chemical weathering and recycling degree is low. It is speculated that the clastic materials of mudstone directly come from the strong weathering and deposition of igneous rocks.

(4) Results of heavy mineral components analysis have shown that the sedimentary strata in the study area are influenced by source rocks such as acid magmatic rocks and metamorphic rocks to a certain extent, and from the change of heavy mineral characteristics in different horizons, it records the first-stage tectonic uplift movement.

Based on the above analysis results and the tectonic position of the study area, it can be concluded that the sedimentary strata of Laiyang Group in Lingshan Island area are influenced to some extent by source rocks such as acid magmatic rocks and metamorphic rocks, and the source rocks are mainly metamorphic sedimentary rocks, intermediate-acid volcanic rocks, metamorphic rocks and sedimentary rocks. The change of provenance reflects a period of tectonic uplift. The main source of provenance in Lingshan Island area is from the Sulu orogenic belt, which may be partly from metamorphic sedimentary rocks of Yangtze platform in the early stage and mainly from Sulu orogenic belt in the later stage.

How to cite: Jiang, Y. and Zhou, Y.: Provenance Characteristics and Tectonic Implication of the Laiyang Group in Lingshan Island of Riqingwei Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1981, https://doi.org/10.5194/egusphere-egu25-1981, 2025.

Detrital petrochronology is a powerful method of characterizing sediment and potentially sediment sources. The recently developed Tucker-1 decomposition method holds promise of using detrital petrochronology to identify both sediment-source characteristics and the proportions in which sources are present in sink samples even when sediment sources are unknown or unavailable for sampling. However, the correlation between endmember characteristics and lithological sources or proportions and sedimentary processes has not been established. Herein we present a case study of the recently developed Tucker-1 decomposition method to a multivariate geochemical data set from detrital zircons in till samples collected above the Cu-bearing Guichon Creek Batholith (GCB) in southern British Columbia, Canada. Data include a suite of eleven variables, including age, Ce anomaly, Ce_N/Nd_N, Dy_N/Yb_N, ΔFMQ, Eu anomaly, ΣHREE/ΣMREE, Hf, Th/U, Ti temperature, and Yb_N/Gd_N, from 12 samples from collected at a range of distances in the down ice-flow direction from the GCB.

We demonstrate that endmember modelling using the Tucker-1 decomposition method successfully deconvolves the multivariate data sets into two endmembers in which the geochemical distributions are consistent with derivation from either non-oxidized and relatively anhydrous (i.e., low ore potential, Source 1) or oxidized and hydrous (i.e., potential ore bodies, Source 2) igneous rocks. Furthermore, we demonstrate that the proportions of the Source 2 endmember decrease with increasing distance from the ore bodies, as expected due to downstream zircon mixing and dilution.

Finally, we attribute each of the zircon grains to either the Source 1 or 2 endmember based on maximization of the likelihood that their measured multivariate geochemistry was drawn from one or the other of the learned multivariate endmembers. We compared these grain attributions to the results of an independent Classification and Regression Tree (CART) analysis designed to characterize zircon grains as either “fertile” or “barren” with respect to copper based on their geochemistry. We find that there is ~80% overlap between the source attributions based on the CART analysis and the grain-source identification based on the Tucker-1 decomposition.

We conclude that the novel Tucker-1 decomposition approach provides a flexible, precise, and accurate method of characterizing multivariate sediment sources even when those sources are unknown. It thus provides a basis for future petrochronological interpretations with applied and pure geoscience applications. All of the analyses presented herein can be freely accessed through a web application (https://dzgrainalyzer.eoas.ubc.ca/) or open-source Julia code (https://github.com/MPF-Optimization-Laboratory/MatrixTensorFactor.jl).

How to cite: Saylor, J. E., Richardson, N., Graham, N., Lee, R. G., and Friedlander, M. P.: Endmember modelling of detrital zircon petrochronology data via multivariate Tucker-1 tensor decomposition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4081, https://doi.org/10.5194/egusphere-egu25-4081, 2025.

Thirty-three surface sediment samples were collected from the Hupo Basin including Hupo Bank, located offshore along the East Coast of Korea, to investigate the provenance of fine-grained sediments using geochemical elements, particularly focused on REEs compositions. Cluster analysis of the surface sediments identified three distinct groups: (1) the inner offshore area of the northwestern Hupo Bank, (2) the area extending from the inner offshore of the southwestern Hupo Basin to the eastern slope of the Hupo Bank, and (3) a single sediment deposit on the eastern slope of the Hupo Bank.

Additionally, the sediments from the southwestern Hupo Basin to the eastern slope of the Hupo Bank were further classified into two subgroups based on their UCC-normalized (Upper Continental Crust-normalized) REE patterns. A comprehensive analysis of the UCC-normalized REE patterns, combined with satellite imagery, suggested that most of the sediments on the northwestern Hupo Bank were predominantly supplied by small nearby streams during typhoon seasons. However, some sediments covered on southern Hupo Basin were likely transported from the southern area via the East Korea Warm Current during the heavy rainy season.

How to cite: Um, I.: Provenance and Transport Mechanisms of Fine-Grained Sediments in the Hupo Basin, Offshore East Coast of Korea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5457, https://doi.org/10.5194/egusphere-egu25-5457, 2025.

To address the controversial and insufficient understanding of the source, sedimentary architecture and reservoir quality differences of the Extension Formation in the Huachi area of the Ordos Basin. This paper is based on the analysis of heavy minerals and their assemblage characteristics, cathodoluminescence imaging of quartz grains, zircon U-Pb geochronology (LA-ICP-MS). It also combines the analyses and test data of core, logging, scanning electron microscope, cast thin section, high-pressure mercury injection (HPMI), constant-rate mercury injection (CRMI) and so on. This basic principles and methods of sedimentology, stratigraphic stratigraphy, sedimentary basin analysis and reservoir sedimentology have been applied to systematically study the relationship between the provenance directions, provenance types, sedimentary system spreading, sedimentary configuration, and reservoir quality in the Chang 3 member of the Yanchang Formation in the study area. The study shows that the Chang 3 of the Huachi area is located in the sedimentary centre of the lake basin, and is influenced by provenance from both the northeast and southwest directions, and is in a mixed-source area along the Qingcheng-Heshui area; The area develops a delta front subfacies, and underwater distributary channel is the main microfacies. The single sand body has three vertical combination modes: downcut superimposed type, superimposed contact type and mudstone separated type, and three lateral combination modes: side cut superimposed type, butt type and mudstone embedded type. The delta front in the study area has an evolutionary pattern of advanced accumulation and backward accumulation, and the single sandbody of the tangential and overlapping relationship developed in the late progradation stage has the best connectivity, with good pore throat structural characteristics and good reservoir quality. In conclusion, under the background of shallow water, low accommodation space, rapid uplift-slow curtain settlement tectonics, the direction, proximity, and type of the source of shallow-water delta are the key factors influencing the distribution of sedimentary micro-phase, and also the material basis for the sedimentary configuration and reservoir quality.

How to cite: Zhang, H.: study on shallow water delta provenance, sedimentary architecture and reservoir quality differences--a case of the Chang 3 member of Yanchang formation in Huachi area of Ordos Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5497, https://doi.org/10.5194/egusphere-egu25-5497, 2025.

Quartz is the most stable and abundant mineral in sedimentary rocks and remains stable during weathering and diagenetic processes [1], thus being a good provenance tracer. Traditional and advanced techniques to determine quartz origin, such as petrography and cathodo-luminescence and laser ablation spectrometry have obtained limited success.

The aim of the study is to implement a new protocol to analyze the oxygen isotopic signatures of single detrital grains of quartz, with primary application in source-to-sink studies, and to assess their role as a provenance fingerprint of different magmatic, metamorphic and sedimentary domains. While single grain approach is standard in detrital thermochronology [e.g. 2,3], it has not been applied on major minerals using classic isotopic tracers.

This new protocol is tested on modern sediments of Ganga-Brahmaputra rivers and turbidites from the Bengal Fan (IODP Expedition 354). Single grain isotopic fingerprint allows us to define oxygen isotopic signature of magmatic and metamorphic source rocks of different Himalayan tectonic domains (Greater Himalaya, Lesser Himalaya, Tethys Himalaya and Trans-Himalayan Batholiths) and to detect and quantify their relative contribution in Bengal turbidites and to highlight sediment mixing from specific sources thus enhancing provenance resolution with respect to bulk approaches.

Around 200 quartz grains in each sand sample from rivers draining exclusively a single Himalayan tectonic domain have been analyzed by ion microprobe LG-SIMS to better characterize their oxygen isotopic variability, thus providing a good fingerprint of the source rocks in the detrital record. Around 150 quartz grains from each Bengal Fan turbiditic sample have been analyzed to quantify the contribution of different Himalayan tectonic domains in Bengal Fan turbidites through time.

The new data, combined with data obtained with other bulk-sediment to single-mineral approaches, allow us to enhance provenance resolution and highlight the erosional evolution of the Himalayan-Tibetan orogen through time.

This new method can be profitably applied in any sediment-provenance study as a precious complement to traditional methods applied to the same quartz grains (luminescence, OH-defects, and petrographic characteristics) as well as classic techniques (e.g., petrography, heavy minerals, elemental geochemistry, isotope geochemistry) to discriminate detrital quartz derived from felsic igneous, metamorphic, or sedimentary sources.

Key words: Oxygen isotopes, Ion Probe LG-SIMS, Provenance analysis, Single-grain techniques, Himalayan orogen, Bengal fan

[1] Clayton, Jackson & Sridhar (1978), Geochimica et Cosmochimica Acta 42(10), 1517-1522.

[2] Blum, Rogers, Gleason, Najman, Cruz & Fox (2018), Scientific Reports 8(1), 7973.

[3] Chew, Najman, Mark, Barfod, Carter, Parrish, & Gemignani (2019), Bulletin of the Geological Society of America 131; 9-10.

How to cite: Limonta, M., France-Lanord, C., Galy, A., Gurenko, A., Bouden, N., and Garzanti, E.:  Single quartz δ18O: a new proxy in sediment provenance studies (Bengal Fan, IODP Expedition 354)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6282, https://doi.org/10.5194/egusphere-egu25-6282, 2025.

In northwestern Croatia, synorogenic clastic formations record important events in the evolution of the Dinarides, including the Dinaride-Alpine transitional area, a region characterized by considerable geological complexity resulting from a severe and long-lasting Mesozoic and Cenozoic deformational history. Our study concentrates on the provenance of Cretaceous sandstones which occur on Mt. Ivanščica, Mt. Medvednica, and Žumberak Mts, with the intent of providing new insights into the evolution of the orogen and possible paleogeographic connections with neighboring tectonic units. Uranium-lead ages of detrital zircon populations place new constraints on the nature of source terrains being exhumed and eroded during the early stage of convergence of the Adria plate margin. Construction of the nascent mountain belt in this stage involved obduction of Neotethyan ophiolites and inclusion of basement units within propagating nappe structures. Zircon age spectra of Early Cretaceous sandstones from Mt. Ivanščica reveal Permo-Triassic, Variscan, Caledonian and Pan-African populations, and one grain with concordant Middle/Late Jurassic age. In Late Cretaceous sandstones from Mt. Medvednica and Žumberak Mts the spectra are dominated by Variscan, Caledonian and Pan-African ages, but in different proportions. Permo-Triassic zircons are completely absent in Mt. Medvednica sandstones, and reflected by only one grain in Late Cretaceous Žumberak Mts sandstone. Permo-Triassic zircons with a mode at ~240 Ma were probably derived from volcano-sedimentary sequence outcropping in northwestern Croatia, while Variscan and pre-Variscan zircons could have been derived both from reworked igneous/metaigneous or sedimentary/metasedimentary sources. The absence of Permo-Triassic zircons in Late Cretaceous clastic sequences precludes the resedimentation of Early Cretaceous sandstones. Significant variations in the age spectra of Late Cretaceous zircon populations point to diverse catchment areas. These results hint towards change in predominant source rocks from Early to Late Cretaceous, as well as local variability during the Late Cretaceous. The presented work is supported by the Croatian Science Foundation project SECret (HRZZ IPS-2023-02-2683).

How to cite: Šuica, S., Lužar-Oberiter, B., Olić, I., and Zeh, A.: U-Pb ages of detrital zircons from synorogenic clastic sedimentary rocks in the Dinarides (Croatia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8608, https://doi.org/10.5194/egusphere-egu25-8608, 2025.

Ocean drill cores recovered by IODP Expedition 354 Bengal Fan (BF) shed light on the world’s largest source-to-sink (S2S) sedimentary system, providing insight into its geodynamic history during the Late Cenozoic. Here, we investigate Hf isotopic compositions of detrital zircon (DZ) grains (N = 1300) by laser ablation multi-collector ICP-MS in Miocene through Pleistocene age turbidites from the middle BF. Prominent DZ age populations in BF turbidites at ca. 25 Ma, 50 Ma and 120 Ma are a close match for modern DZ ages obtained from Brahmaputra River sands, suggesting strong ties to Tibetan sources within the paleo-Brahmaputra drainage area. Previous studies documented increased proportions of young U-Pb DZ age populations (< 300 Ma) in BF turbidites, showing they nearly double in abundance starting in the Late Pliocene (ca. 2.7 Ma). We obtained Hf isotope compositions on individual U-Pb dated DZ grains, with an emphasis on placing further constraints on the provenance of the < 300 Ma DZ age group. BF turbidite sands all contain DZ showing a wide range of hafnium isotopic compositions (ε_Hf   = +20 to -30); however, Pleistocene turbidites contain a higher proportion (by 2:1) of more negative ε_Hf DZ signatures compared to Miocene/Pliocene-age turbidites. This is reflected in the ε_Hf signatures of the ca. 25, 50 and 120 Ma DZ U-Pb age groups, which all trend more negative in Pleistocene turbidites compared with Miocene/Pliocene -age turbidites. The effect is most pronounced for the ca. 50 Ma DZ age group; comparison with published zircon U-Pb and zircon Hf isotope data from bedrock sources indicate that the ca. 50 Ma DZ age group is derived from the Gangdese or Bomi Chayu batholiths of the Lhasa Terrane, whilst the ca. 120 Ma DZ age group is primarily sourced from the Bomi Chayu batholith; the ≤25 Ma DZ age group carries the signature of sources in the Namche Barwa massif (eastern Himalayan syntaxis portion of the Brahmaputra drainage). We hypothesize that greater integration of the Lhasa Terrane into the Yarlung-Brahmaputra river drainage system changed the dynamics of paleo-sediment transport to the Bengal Fan starting in the Late Pliocene. A growing U-Pb age and Hf isotope database from modern Himalayan river sands will help place further constraints on sediment routing, tectonic and climatic influences in the Himalaya-Bengal Fan S2S system since the mid-Miocene when delivery of turbidite sands to the middle Bengal Fan rapidly intensified.

How to cite: Gleason, J., Najman, Y., Orme, D., Sundell, K., and Blum, M.: Himalayan source-to-sink dynamics and the detrital zircon Hf isotope record in Bengal Fan Turbidites (IODP Exp. 354), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13697, https://doi.org/10.5194/egusphere-egu25-13697, 2025.

The Ediacaran to Cambrian transition witnessed a key interval in the Earth’s history for biological revolution, environmental change and tectonic evolution. Wells and seismic data show that a Lower Cambrian thick siliciclastic rock succession occurs in the NW Yangtze Block, South China. The provenance and tectonic setting for the thick Cambrian sedimentary successions are very crucial for understanding the Ediacaran-Cambrian transition. Here, a Cambrian outcrop section (ca. 800-m-thick) in the middle Longmenshan fold-thrust belt, NW Yangtze Block, which is composed of mixed carbonate-siliciclastic strata, was investigated to constrain depositional ages, sedimentary environments, provenance and tectonic settings, through integrating field-based sedimentology, petrography, whole-rock element geochemistry, detrital zircon U-Pb dating, zircon trace elements and Hf isotopes, and carbonate stable C isotope data. The sedimentary succession is thought to accumulate during the Terreneunian to Epoch 2 time (i.e., Age 2 to Age 4, ca. 524-509 Ma) by comparison of our new carbonate stable C isotopic data and the global Cambrian δ¹³C curve and by the detrital zircon U-Pb age evidence (the youngest age peaks ranging from 538 to 518 Ma). The investigated strata have coarsening-upward trends and indicate complex, variable sedimentary environments (including slope-basin, deep-water shelf and fan delta settings) with hydrothermal inputs. Sandstones from the lower Qiongzhusi Formation have abundant volcanic lithic fragments and detrital zircons therein are dominated by Ediacaran to Cambrian ages. However, sandstones from the upper Canglangpu Formation consist of variable lithic fragments (including chert, metamorphic, volcanic and sedimentary clasts) and indicate diverse detrital zircon U-Pb ages (1000-500 Ma and minor 2600-2100 Ma). Both geochemical data of fine-grained sedimentary rocks and petrographic data of the sandstones reveal the deposits were relatively immature and were derived from proximal sources. Additionally, trace elements of the zircon grains with 650–500 Ma ages indicate a continental arc origin. All the results point to nearby arc-related source terranes for the Cambrian clastic records, rather than distant orogen sources as previously proposed. The geological and geochemical evidence, combining published geophysical data, imply the development of an early Cambrian orogen northwest to the study area. We suggest that the underestimated arc settings were formed in response to the subduction of the Proto-Tethys ocean beneath the NW Yangtze Block, which resulted in continental collision and uplift of northwest microterranes that provided siliciclastic sediments to fill the foreland basin southeastward.

How to cite: Gu, Z. and Jian, X.: Sedimentary provenance analysis unravels the Early Cambrian orogeny in the NW Yangtze Block, South China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13916, https://doi.org/10.5194/egusphere-egu25-13916, 2025.

The development of in-situ Lu-Hf LA–ICP–MS/MS geochronology has opened avenues to dating garnet, apatite, xenotime, calcite and epidote-group minerals. Of these phases, garnet and apatite are particularly relevant to provenance analysis, as both can be dated in situ by the U–Pb, Sm–Nd and Lu–Hf systems, are often present in sediments, and retain geochronological as well as geochemical information during erosion, transport and sedimentation. Garnet and apatite also have the benefit of forming in different geological settings to minerals more widely used in provenance analysis, such as zircon. Zircon usually forms during high-temperature processes such as anatexis and magmatic crystallisation, and has a bias towards more felsic rock compositions. Conversely, garnet is a dominantly metamorphic mineral, and usually retains information about the prograde (and sub-anatectic) history of metamorphic rocks, but may also form in hydrothermal settings, and is stable across a wide variety of lithological compositions. Apatite also forms in a wide variety of rock lithologies during metamorphism and magmatism, and therefore can represent more intermediate and mafic magmatic events which are not sampled by zircon. In situ Lu–Hf geochronology therefore provides an excellent tool to understand the timing and conditions of mountain building and magmatic events from the detrital record, but not without methodological and geological caveats and limitations. The application of the method itself, data handling and analytical interpretations will be presented and discussed.

How to cite: Tamblyn, R., Gillespie, J., and Simpson, A.: In-situ Lu-Hf for provenance analysis – a methodological perspective , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14070, https://doi.org/10.5194/egusphere-egu25-14070, 2025.

How to cite: Yang, H., Kim, K., Kim, H. J., Chae, Y.-U., Lim, H. S., and Joo, Y. J.: Sandstone petrography and geochemistry of the Icheonri Formation in southeast Korea: Implications for provenance and tectonic setting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14108, https://doi.org/10.5194/egusphere-egu25-14108, 2025.

Turbiditic sediments found in accretionary complexes (ACs), originally deposited in a trench environment, document processes and environmental conditions governing sediment production and deposition in a subducting continental margin, including tectonic setting and paleogeographic configuration. Along the East Asian continent, subduction of the Paleo-Pacific plate has continued since the late Paleozoic, resulting in the development of numerous ACs containing Paleozoic and Mesozoic sediments that now make up a large part of the Japanese Islands. The Ashio terrane, distributed in central Japan, consists of Upper Paleozoic-Jurassic pelagic and turbiditic sediments and is considered equivalent to the Mino-Tamba terrane, the AC covering a large area of the main island. This study examines the sandstone petrography and whole-rock geochemistry of turbiditic sandstone and shale of the Ashio terrane to interpret their provenance and tectonic history. The sandstones of the Ashio terrane, classified as lithic arkose to feldspathic litharenite, are sub-angular to sub-rounded and poorly sorted. The major framework grains are quartz, plagioclase, K-feldspar, and lithic fragments (metamorphic and sedimentary, including chert), with minor amounts of mica, garnet, and heavy minerals. In the Qt-F-L diagram of provenance tectonic setting, they are all interpreted to have been derived from a recycled orogen provenance. Based on the presence of chert grains, we hypothesize that at least part of the pre-Jurassic ACs was probably uplifted and exposed in the hinterland during deposition of the Ashio terrane sediment. Furthermore, the presence of easily weatherable feldspar and metamorphic lithic fragments suggests that not only the ACs sediment but also metamorphic and/or igneous rocks were exposed in the source area. The detrital garnet assemblages in the Ashio terrane sandstones are characterized by a pyrope-rich almandine garnet with low grossular content, reflecting their origin in granulite-facies metamorphic rocks. Such detrital garnets have been previously reported from Jurassic to Cretaceous sandstones of Japan with rare occurrences in Permian sandstones, suggesting that the Ashio terrane garnets were likely first-cycle detritus from a nearby high-grade metamorphic basement. Based on their rare earth element patterns, the source rock composition of the Ashio terrane sediments seems felsic and more fractionated than the upper continental crust (UCC), which is known to be similar to granodiorite. In the A-CN-K compositional space, the Ashio terrane sediments suggest weathering from granodioritic source rocks, and the scatter of the samples along the weathering trend indicates that non-steady-state weathering conditions in the source area. In a tectonic discrimination diagram based on chemistry, their composition resembles sediments derived from a passive continental margin, which is consistent with the sandstone modal composition. Previous studies of Cretaceous Japanese ACs suggested sediment recycling and supply from uplifted pre-existing ACs, supporting our interpretation of the Ashio terrane provenance. Additionally, the compositional difference between the sandstones of the Mino terrane (arkosic) and Ashio terrane (lithic) infer a heterogenous nature of depositional conditions in a subduction zone. These findings provide paleogeographic information and more comprehensive interpretations of the environmental conditions surrounding the subduction zone along the East Asian continental margin during the Mesozoic.

How to cite: Kim, K., Lee, Y. I., and Joo, Y. J.: Sandstone petrography and whole rock geochemistry of the Ashio terrane, a Jurassic accretionary complex in Japan: Implications for provenance and tectonic setting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14110, https://doi.org/10.5194/egusphere-egu25-14110, 2025.

Rutile belongs to the group of ultra-stable minerals during processes of the sedimentary cycle, along with zircon and tourmaline. While detrital zircon mostly derives from felsic igneous rocks and tourmaline is hardly datable, rutile is mainly sourced from metamorphic rocks and routinely datable by U−Pb chronology. Thus, combining detrital rutile age information with trace-element based discrimination of different metamorphic source rocks has a high potential to gain time-resolved insights into the geodynamic evolution of the hinterland. However, trace-element based approaches are so far limited to (i) bivariate discrimination of mafic and felsic metamorphic source rocks by considering Cr and Nb concentrations (Zack et al. 2004a; Meinhold et al. 2008; Triebold et al. 2007, 2012), (ii) temperature information by considering Zr concentrations (e.g., Zack et al. 2004b; Kohn 2020) and assuming the same pressure conditions for all detrital grains, (iii) identification of fluid alteration based on e.g., W, Sn, V, Sb, Cr, Nb, Fe (Agangi et al. 2020; Pereira et al. 2021; Pereira & Storey 2023); and (iv) identifying very specific sources like mafic low-temperature/high-pressure rocks by considering H₂O concentrations in combination with Zr, Nb, W, and Sn (Lueder et al. 2024).

Here we compiled a dataset of 2,335 rutile trace-element analyses (16 elements) from 110 metamorphic rock samples of a wide range of pressure−temperature conditions. Using a modified version of the original random forest algorithm (Breiman 2001) for dealing with the hierarchically structured data, we trained three multivariate discrimination models. Under the assumption of a metamorphic source, the first model discriminates felsic and mafic rutile with a classification success rate of >90 %, which is a strong improvement compared to Cr versus Nb plots (72−86 % success on the same dataset). The second and third models discriminate rutile from rocks that formed under low and high temperature/pressure gradients (≤ 350 °C/GPa versus >350 °C/GPa) for felsic (>91 % success) and mafic rocks (>93 % success), respectively. We are currently integrating the three models to achieve a simultaneous prediction of composition and temperature/pressure gradients of the metamorphic source rock, taking rutile provenance analysis to a new level.

How to cite: Schönig, J., Zack, T., Rösel, D., Marschall, H., von Eynatten, H., Lünsdorf, K., Lueder, M., Konrad-Schmolke, M., and Walters, J.: Chemical discrimination of rutile from different metamorphic source rocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14755, https://doi.org/10.5194/egusphere-egu25-14755, 2025.

Relief degradation and drainage evolution in the aftermath of major orogenies have been extensively studied for young mountain belts. For ancient orogenic settings such reconstructions often remain enigmatic with respect to, e.g., exhumation and erosion rates, sediment dispersal paths and sediment budgets as well as associated paleolandscapes and sediment routing systems. Sedimentary provenance analysis provides an essential tool to constrain these complex systems in space and time.

Here we present a multi-method provenance study from the Black Forest, the Palatinate Forest and the Vosges (SW Germany and NE France) that includies heavy mineral assemblage data from 100 sandstone samples as well as detrital zircon U-Pb geochronology and grain-size measurements from 40 selected samples. The samples cover approximately 10 to 15 Myrs from Zechstein to Upper Bundsandstein strata (Wuchiapingian to early Anisian). Additional data comprise detrital tourmaline and garnet geochemistry as well as detrital monazite geochronology.

The heavy mineral assemblages are rather uniform, dominated by the stable phases zircon, tourmaline and rutile (along with other TiO₂-polymorphs) and complemented by variable apatite content as well as minor monazite. Zircon U-Pb ages range from ~0.25 to 3.5 Ga, showing prominent Variscan (30%), Caledonian (23%) and Cadomian (28%) age components, along with older ages (19%). Grain-size data indicate an overall decrease of zircon size with increasing U-Pb age. The zircon age distributions suggest an increase of Cadomian and older ages at the expense of Variscan ages with decreasing stratigraphic age of the samples. This observation is independent of zircon grain size. It is interpreted to reflect a change from more local sources in Late Permian time to a significantly enlarged catchment area in the Early Triassic that includes tapping new source regions. This comes along with a homogenization of sediment composition across the entire drainage and depositional area in the late Olenekian to early Anisian. Our study serves as an example of heavy-mineral based fingerprints for regional-scale drainage basin widening due to relief planation in the aftermath of major orogenic phases. 

How to cite: von Eynatten, H., Sass, K., Dunkl, I., and Schönig, J.: Permo-Triassic sediment provenance and paleodrainage in Central to Western Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15518, https://doi.org/10.5194/egusphere-egu25-15518, 2025.

Provenance analysis is a critical connection between the sedimentary basin and the orogenic belt. Methods such as petrological analysis of clastic rocks, heavy mineral analysis, geochemical analysis, and isotopic dating methods are all based on core analysis. However, core analysis is expensive and limited in quantity.

Well logging data are easy to obtain and can reflect much information. Moreover, the logging data has longitudinal continuity, which can record the formation properties continuously. A new quantitative method for provenance analysis based on well logging data is proposed. The new method mainly relies on the assumption that terrigenous clastic rocks are the products of weathering, fragmentation, transport, and deposition of the original rocks in the provenance area, and the composition and combination of clastic minerals in the rocks can reflect the characteristics of the source area. Then, different clastic minerals have different physical properties, and logging responses, so clastic rocks from different provenances may have different logging responses. The difference in logging response can be used to analyze the source-sink system.

A case study is introduced. Jiyang Depression of the Bohai Bay Basin is a faulted lake basin in the Paleogene. The northern part of Dongying sag is the Chenjiazhuang uplift, and the western part is the Binxian uplift, both parts are important provenance areas. Sedimentary systems such as near-shore subaqueous fan and fan delta are widely developed in the steep slope zone of the faulted lacustrine basin. The logging and drilling lithology analysis shows that well A has a 50m conglomerate layer in Shahejie Formation. The logging data show that the logging response of the top 30m conglomerate layer is different from that of the bottom 20m conglomerate layer. The core analysis shows that the top conglomerate is dominated by granitic gneiss rock, while the bottom conglomerate is dominated by carbonate rock. two provenance systems are developed in Dongying Sag.

This method can achieve good results on coarse-grained sediments, but this method may be restricted to deposits mainly composed of fine sandstone, silty, and shale. In the future, multiple methods should be combined to improve the result of provenance analysis.

How to cite: Qiu, T.: A new method for provenance analysis in sedimentary basins based on logging data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15816, https://doi.org/10.5194/egusphere-egu25-15816, 2025.

Northern Calabria, situated at the southern end of the Italian Peninsula, is geologically complex due to its position at the convergence of the Eurasian and African plates. This complexity arises from significant deformation processes, including thrusting, folding, and extensive faulting associated with the closure of the Tethys Ocean and subsequent collisional and extensional tectonics. Thrusting during the Alpine orogeny resulted in a series of extensive nappe stacking, followed by structural reorganization and exhumation of these stacks during the Oligocene to Miocene, reflecting ongoing tectonic activity. Along the eastern margin of northern Calabria, fore-arc basins developed in response to the retreating subduction zone and evolution of the Calabrian arc. From north to south these are termed Rossano, Ciro, Crotone, and Catanzaro sub-basins. Analysing the stratigraphic record of these basins in terms of provenance shifts and changing drainage patters, will aid in further characterising the main exhumation phase of the northern Calabrian Massif, encompassing the Sila Massif and the Coastal Chain (Catena Costiera).

A multi-proxy provenance study was designed combining heavy mineral analysis (via semi-automated Raman spectroscopy), garnet chemistry (via electron microprobe), and apatite trace element analysis and U-Pb geochronology (both via LA-ICP-MS). A collection of siliciclastic samples spanning ~15 Ma from Aquitanian to Messinian in age from the four pre-mentioned sub-basins were selected for measurement. The results present a wide range of both high grade to low grade metamorphics and granitoids, with strong contrasts present spatially and temporally. A high contribution of high-pressure metamorphic phases like lawsonite, glaucophane, and kyanite was identified in samples from the Rossano basin. Paired with the presence of garnets from greenschist/blueschist-facies rocks and apatite derived from mafic igneous rocks, sourcing is likely from Liguride units currently exposed in northern and western regions of northern Calabria (e.g. Catena Costiera, northern Crati valley). Occurrence of andalusite in the Serravallian/ Tortonian samples of the Ciro and Crotone basins points to sourcing directly from the Sila Massif plutonic rocks and/or its high-temperature metamorphic rims. Furthermore, large proportions of Ca-rich garnets in Crotone, and the oldest sample from Ciro, suggest metasomatic host-rocks also reflect this sourcing pattern. Apatite geochronology from Crotone shows one singular significant peak around 300 Ma, referring to the Variscan orogeny and further underlining a significant input from Sila granitoid rocks. The shift in sediment sourcing patterns from the lower to middle Miocene in the Rossano, Ciro, and Crotone basins indicate the exhumation of the Calabrian arc, along with its subsequent increasing and then decreasing relief, played a pivotal role in controlling the timing and direction of sediment transport.

How to cite: Feil, S., von Eynatten, H., Chew, D., Schönig, J., Dunkl, I., Caracciolo, L., and Muto, F.: Provenance and drainage evolution of the Northern Calabria forearc, southern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18573, https://doi.org/10.5194/egusphere-egu25-18573, 2025.

The collision between Europe and Alcapa (a segment of Adria) led to the formation and subsequent erosion of high-pressure rocks in the Carpathian and Alpine arcs. Metamorphic rutile, which forms under relatively high pressures, is a reliable indicator of subduction environment during orogeny. To enhance our understanding of the Alpine Tethys Ocean's closure in the Western Carpathians, U-Pb geochronology was performed on detrital rutile from medium-grained sandstones within the Magura and Silesian Nappes.

Twelve samples were collected along a transect in the Magura Nappe, with an additional three samples from the Silesian Nappe serving as a reference. An additional profile of three samples was collected from the Altengbach-Formation of the Rhenodanubian Flysch in the Greifensteiner-Decke for comparison. From each sandstone, approximately 200 rutile grains were extracted, and about half were selected for detailed analysis. The dated rutile grains exhibit significant variation in age and physical characteristics, indicating multiple source origins.

In the Magura transect the most prominent age peaks align with the Variscan (c. 400–280 Ma) and Alpine (c. 160–90 Ma) tectonic events, both of which are well-represented except oldest dated sample. Notably in the Magura transect, four distinct Alpine maxima were identified in the rutile dataset. Among these, the two dominant peaks at 137–126 Ma and 115–105 Ma appear in most samples. Two additional samples, deposited during the Eocene–Oligocene and the Late Cretaceous–Paleocene, reveal the youngest age peak at 94–90 Ma. A peak at 193–184 Ma is observed in these two samples and in another sandstone dated between the Paleocene and Eocene.

The Silesian samples consistently exhibit a prominent Variscan peak. Only the sample deposited in the Oligocene reflects Alpine tectonic events, with one dominant peak at 95 Ma and two minor peaks at 26 Ma and 180 Ma.

In the Altlengbach-Formation the Alpine peaks appear in the two youngest samples, whereas the Variscan peaks are prominent in all samples. The oldest sample is Lower Cretaceous whhereas the other two are Upper Cretaceous–Paleocene.

For the Carpathian samples, we tentatively propose that key tectonic events include the Jurassic subduction of the Meliata Ocean (~180–155 Ma) and the Cretaceous nappes stacking and exhumation of the Veporic and Gemeric megaunits (140–90 Ma). The widespread presence of Alpine-age rutile in all but the oldest sandstone indicates an open sedimentary pathway from the southern and central Alcapa to a basin located north of the alleged Oravic (Czorsztyn) continental sliver within the Alpine Tethys Ocean. The absence of Alpine ages in the oldest sandstone may reflect either a physical barrier separating the basin from the orogen or the unavailability of rutile-bearing rocks at the surface during that time.

More broadly, we suggest that the synorogenic deposits of the Outer Western Carpathians contain detritus derived from previously subducted, exhumed, and imbricated oceanic and continental crustal domains. Age peaks in the ~180–105 Ma range are probably related to the closure of the Neotethys Ocean (Meliata branch), while the youngest peak at 94–90 Ma possibly corresponds to the subduction of the Alpine Tethys beneath Alcapa.

Research is funded by the NSC, Poland, project no. 2021/43/B/ST10/02312.

How to cite: de Doliwa Zieliński, L., Bazarnik, J., Kooijman, E., Kośmińska, K., Potočný, T., Mazur, S., and Majka, J.: Tracing Alpine Tethys Closure: Insights from Detrital Rutile Geochronology in the Outer Western Carpathians and Eastern Alps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18697, https://doi.org/10.5194/egusphere-egu25-18697, 2025.

Detrital zircon geochronology is becoming increasingly popular in provenance studies relying on the growing availability of accurate techniques and extensive datasets. This large amount of data is currently employed in ancient settings to describe source-to-sink scenarios deriving tectonic and (eventually) climatic implications. The study of modern sediments of African river systems offers the opportunity to observe how the zircon signal is propagated along these vast sediment highways and how the mere interpretation the zircon signal in the deep sea may lead to a significant misfit of interpretations in the source-to-sink system.
One of the factors linking major river systems is the highly segmented nature of sediment transport. Even though this phenomenon is currently enhanced by effect of dams, geomorphic barriers prove to be highly effective. In Niger River, for example, the exclusively Archean-Paleoproterozoic age signal from Leo-Man Shield in Guinea is unable to cross the natural barrier of sand dunes of the Inner Delta. Similarly, old zircons characterising the sands of the Victoria Nile and Albert Nile sink in Lake Victoria and the Sudd marshes. The recent evolution of the Zambezi River demonstrates that zircon geochronology alone is insufficient for depicting the routing system. Paired observations of bulk petrography, elemental, and isotope geochemistry effectively reveals that provenance signals are extremely segment along the river course.
Undoubtedly, the high durability of zircon through sedimentary cycles is effective in indicating the major episodes of crustal growth at continental scale. However, it simultaneously highlights the pitfall of not considering recycling as one of the main features for zircon provenance. In the Orange River, the Pan-African age cluster is dominant from the headwaters all the way to the mouth and transported by ocean currents as far as Angola. This occurs even though the Pan-African basement is only minimally exposed in the catchment, whereas zircon signal is stored in the Karoo Supergroup sandstones.

How to cite: Pastore, G., Garzanti, E., Vermeesch, P., Resentini, A., and Vezzoli, G.: Detrital zircons in modern African rivers: does the Sink truly reflect the Source?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18786, https://doi.org/10.5194/egusphere-egu25-18786, 2025.

The metasedimentary Legoupil Formation, located at Cape Legoupil and the Schmidt Peninsula, antarctica could give a hint for the tectonic evolution of Antarctic Peninsula. In this contribution, we constrain the sedimentary provenance of the Legoupil Formation through geochemistry and detrital zircon U-Pb geochronology. The petrography and geochemical features indicate that the provenance of the Legoupil Formation could be felsic rocks. Detrital zircon grains record a steady supply of Permian and Ordovician material into the Legoupil Formation. The youngest concordant zircon ages of 262 Ma suggest that the depositional time of Legoupil Formation is no older than Late Permian. The detrital zircon age spectrum of Legoupil Formation suggests that the Legoupil Formation sediments should be derived from regional sources endemic to western Gondwana prior to its breakup.

How to cite: Cui, Y. and Wang, X.: Early Triassic Legoupil Formation in Schmidt Peninsula, Antarctic Peninsula, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20283, https://doi.org/10.5194/egusphere-egu25-20283, 2025.

Purpose: The Bonan Sag is located in the Bohai Bay Basin in eastern China, where the chlorite content is high in the lower part of the fourth member of the Shahejie Formation. In this paper, the genesis of chlorite in the study area was analyzed by means of casting thin section observation, scanning electron microscope, EPMA and LA-ICP-MS, and its influence on reservoir was discussed.

Experimental samples and analysis methods: In this paper, several samples of Well H1 and Well H2 in the lower part of the fourth member of Shahejie Formation in Bonan sag are selected. Firstly, the morphology and size of chlorite in the sample were observed and described in detail by casting thin sections and scanning electron microscopy. Then, the thin sections were polished, and the different forms of chlorite were subjected to electron probe and laser ablation with the assistance of scanning electron microscopy. The elemental composition of chlorite was measured and analyzed.

Result: Well H1 is mostly coated chlorite, attached to the edge of the particles, inhibiting the secondary enlargement and cementation of quartz and other particles, which is conducive to pore development. The H2 well is mostly rose-like chlorite, which is mainly filled in the middle of the pores, plugging the pores and reducing the porosity and permeability of the reservoir.

The Fe/(Fe + Mg) values of chlorite are generally 0.3-0.7, but they can be clearly divided into two categories: one category has an average value of 0.37, which is significantly smaller than the standard chlorite, and most of them are coated chlorite (relatively rich in Si); the average value of the other type is 0.66, which is significantly larger than that of the standard chlorite, often showing a rose-like (relatively rich in Fe).

Conclusion: The content of quartz and feldspar in well H1 is high, which is coated chlorite rich in Si. It is formed by the dissolution of feldspar and quartz during diagenesis, which has a positive effect on reservoir physical properties. The content of magmatic rock debris and metamorphic rock debris in well H2 is higher, which is Fe-rich in rose chlorite. It is formed by the alteration of magmatic rock and metamorphic rock debris during diagenesis, which has a negative effect on reservoir physical properties.

Keywords: Bonan Sag; Tight sandstone; Reservoir; Chlorite genesis;

How to cite: Zhang, H., Liu, G., Liu, K., Chen, J., and Wang, S.: The genesis of chlorite in tight sandstone reservoirs and its influence on reservoir properties: A case study of the lower fourth member of Shahejie Formation in Bonan Sag, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-25, https://doi.org/10.5194/egusphere-egu25-25, 2025.

Focusing on the shale oil reservoirs of the second member of the Kongdian Formation in Cangdong Sag, eastern China, this study explores the origin and distribution of analcime, aligns the fluid evolution stage with different analcime types, and constructs a new micron-scale water-rock reaction sequence. The study identifies six types of analcime based on occurrence characteristics (occurring as laminae, lens, fracture filling, bioshell filling, vein marginal crystal and cement). The above six types of analcime is further classified into hydrothermal fluid origin analcime (HFOA: include analcime cement, vein marginal crystal, lens, fracture filling and bioshell filling) and connate fluid origin analcime (CFOA: analcime laminae) based on major elemental indicators (Si/Al and 10K/(10K + Na)). HFOA has lower ∑REE (rare earth element) and strong positive correlation between ∑REE and LILEs (large ionic lithophilic elements); while CFOA has higher ∑REE and weak positive correlation between ∑REE and LILEs. Different analcime types correlate with varying fluid properties and transport stages. HFOA forms during magmatic hydrothermal fluid (MHF) upwelling. After the MHF entering and mixing with the lake water, thermal repulsions between the crystal particles made it move to form fine grained sedimentary layer, the connate fluid trapped in pores directly precipitate to form CFOA, or form CFOA by modifying clay minerals and feldspars. Through this study, we systematically analyzed the fluid evolution and activity characteristics of the faulted lake basin by using analcime distributed in micron-scale laminae and fractures, hoping to provide new perspectives for the study of diagenetic processes in sedimentary basins.

How to cite: Wang, J., Liang, C., Cao, Y., and Liu, K.: Fluid evolution and tracing at micron-scale of shales in faulted lake basin: A new perspective based on analcime, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-189, https://doi.org/10.5194/egusphere-egu25-189, 2025.

Late Archean Banded Iron Formations (BIFs) serve as exceptional reservoirs of primordial aquatic precipitates, offering a valuable window into the ancient ocean water chemistry and biogeochemical cycles that operated prior to the Great Oxygenation Event (GOE) around 2.4 Ga. It is generally believed that the primordial mineralogy of these BIFs was dramatically modified to Fe-oxides (magnetite and/or hematite) during subsequent hydrothermal and metamorphic episodes. While the earlier consensus does not clearly support an authigenic to early diagenetic origin for magnetite, some experimental studies suggest its stability within microbially influenced primary authigenic to early diagenetic environments. Despite being affected by several post-diagenetic alteration events, the central part of the Chitradurga Schist Belt (CSB) in the Western Dharwar Craton (WDC), particularly around the Chitradurga district, adequately preserves a wide array of primary mineral assemblages, with locally developed dispersed magnetite grains. Detailed petrographic observations supported by SEM-EDS analysis of the cherty Banded Iron Formation (BIF), stratigraphically positioned atop the shallow-water unstable shelf association of the Vanivilas Formation within the Chitradurga Group (3.0–2.6 Ga), offer a valuable opportunity to investigate the origin of these magnetite grains, their association with primary mineral assemblages, and their diagenetic modifications.

The primary mineral assemblages are present as submicron-scale lump-like structures (10–50 µm) embedded within silica (SiO₂) matrix, intervened by a network of silica-filled shrinkage cracks. Based on mineralogy and texture, three microfacies have been identified: a) silicate-carbonate-phosphate-bearing green lumpy microfacies (greenalite + siderite + apatite ± magnetite), b) silicate-oxide-bearing red lumpy microfacies (greenalite + hematite ± siderite), and c) silicate-sulphide-bearing black lumpy microfacies (greenalite + pyrite). Magnetite occasionally appears as a primary lump-forming mineral in the first microfacies, whereas in the second variety, it develops along the periphery of associated Fe³⁺-bearing mineral phases. The coexistence of euhedral-shaped, submicron-sized magnetite (1–5 µm) within these primary lumps, along with greenalite, suggests their origin through the reduction of a primary Fe³⁺-bearing oxy-hydroxide phase, formed in near-surface `oases' of O₂-rich seawater through cyanobacterial oxidation of hydrothermally sourced Fe²⁺. The reduction of this Fe³⁺-bearing oxy-hydroxide phase to form a metastable Fe²⁺-bearing hydrous green clay (greenalite) and more stable magnetite can occur either during settling through the water column or during authigenic to early diagenetic stages via dissimilatory iron reduction (DIR) at the sediment-water interface.

The possibility of DIR is further supported by textural evidence within silicate-oxide-bearing microfacies, where subhedral to anhedral magnetite is present along the periphery of these Fe³⁺-bearing lumps. The presence of Fe³⁺-bearing phases in the core reflects the signature of an incomplete reaction involving Fe³⁺ oxy-hydroxides and organic matter to form magnetite. Our findings reevaluate the debate over the origin of magnetite in Late Archean BIFs, suggesting that magnetite can form within biologically influenced microenvironments, even during authigenesis and/or early diagenetic stages.

How to cite: Bose, S., Sen, A., Samanta, P., and Mukhopadhyay, S.: Possible origin of authigenic to early diagenetic magnetite through ‘Dissimilatory Iron Reduction’ (DIR) within Late Archean Banded Iron Formation from Chitradurga Schist Belt (CSB), Western Dharwar Craton (WDC), India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-671, https://doi.org/10.5194/egusphere-egu25-671, 2025.

This study investigates sedimentary and hydrothermal uranium (U) mineralization in the Neoproterozoic Cave-Temple Arenite Member of the Kerur Formation, Badami Group, Karnataka, within the South Indian Shield (SIS). The studied succession comprises three fluvio-alluvial depositional cycles, with the middle cycle recording evidence of marine sedimentation. Uranium enrichment occurs across the fluvial sediments of the 1^st and 2^nd cycles, as well as the marine sediments of the 2^nd cycle. The higher grade of mineralization, however, is restricted to the lowermost fluvio-alluvial segment of the 1^st cycle, where significant hydrothermal enrichment is evident.

Three distinct modes of U-mineralization have been identified. The first one (the primary mode) represents syn-depositional, microbially induced sedimentary uranium accumulation within organic matter (OM)-rich clay laminae of marine shales, siltstones, and fine sandstones of the 2^nd cycle. This mode is characterized by microcrystalline uranium-(calcium)-phosphosilicate (UPS) phases, often intermingled with uranium titanates, and is associated with microcrystalline sedimentary pyrites, often clustered as framboidal aggregates, and kerogenous OM. Provenance analyses and petrography of U-bearing sedimentary rocks suggest U-sourcing from the Archean-Palaeoproterozoic granitic and felsic basement rock suites of the Dharwar Craton. A positive correlation (r = +0.8, ρ < 0.01; n = 26) is observed between bulk rock OM content (TOC%) and uranium enrichment in the primary mode. Micro-RAMAN spectroscopy confirms the association of UPS phases and sedimentary pyrites with OM-rich matrices and clay-rich organic laminae, while the carbon and sulfur isotopic analyses of the bulk reinforce the biogenicity of the host sediment. The enrichment of redox-sensitive trace elements like V, Mo, Cu, Co, Ni, and As within the clay- and OM-rich sedimentary rocks further indicates the presence of active redox cycling along with biogeochemical and paleoproductivity processes during the syn-to-meta-depositional phases.

The remaining two modes correspond to secondary, post-depositional hydrothermal uranium enrichment within the fluvial sandstones of the 1^st cycle and the fluvio-marine sedimentary rocks of the 2^nd cycle. These modes manifest as uranium phosphosilicate and uranium silicate phases, associated with hydrothermal pyrites in fractures, micro-veinlets, or intergranular patches. Unlike the primary, syn-sedimentary mode, the hydrothermal mineralization does not show any distinct correlation between uranium concentration and TOC%. Isocon mass balance further suggests that uranium, iron, and high field strength elements (HFSEs) were mobilized from these sediments hosting the primary mode, likely facilitated by organometallic ligands, such as siderophores associated with OM, during the epigenetic hydrothermal process under oxygenated hydrothermal conditions. Mobilized uranium was subsequently trapped by pyrites in hydrothermal fractures, forming the secondary modes of U-mineralization.

This dual mechanism highlights an initial microbially mediated, OM-induced uranium accumulation, acting as a vast, low-grade source for later hydrothermal remobilization and enrichment. The findings emphasize the interplay of depositional environments, microbial activity, and hydrothermal remobilization of biogenic accumulation in uranium mineralization, with implications for sediment-hosted uranium exploration.

How to cite: Sen, A., Pal, D. C., Samanta, P., Stüeken, E. E., Bose, S., Ghosh, N., and Mukhopadhyay, S.: Role of syn-sedimentary biogenic and epigenetic hydrothermal uranium enrichment in the formation of sediment-hosted uranium mineralization: evidence from the Neoproterozoic Badami Group, Southern India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-682, https://doi.org/10.5194/egusphere-egu25-682, 2025.

The Proterozoic millimeter-sized ministromatolites have been recognized for their potential biological origin, yet concrete biotic proof has been elusive, which has sparked debates about their possible chemical origins. Recently, unique ministromatolites were identified in a microbial dolostone layer within the Mesoproterozoic Wumishan Formation at Lingyuan in Northern China. Examination of thin sections of these ministromatolites has uncovered a wealth of coccoidal microfossils, measuring 10 to 30 micrometers in size. Petrofabric analysis indicates that these ministromatolites underwent three episodes of diagenetic silicification, with the microfossils being exclusively preserved in early diagenetic chert. This finding supports the hypothesis that silicification occurring concurrently with mat development is crucial for the exceptional preservation of microfossils, which suggests that the scarcity of microfossils in most Precambrian carbonate stromatolites may be attributed to the absence of hydrochemical conditions conducive to early silicification. While chemically-formed fibrous carbonate minerals predominate in these ministromatolites, the abundance of microfossils suggests that the contribution of microorganisms to the formation of ministromatolites was previously underestimated. Consequently, this study proposes that Mesoproterozoic ministromatolites are not merely chemical byproducts but rather intricate mixtures of both biological and chemical components.

How to cite: Wang, T. and Xiong, W.: Fossil evidence provides new insights into the origin of the Mesoproterozoic ministromatolites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-845, https://doi.org/10.5194/egusphere-egu25-845, 2025.

Dolomite formation remains one of the most intriguing puzzles in sedimentary geology, often referred to as the “dolomite problem” . Growing evidence suggests that microbial mediation plays a critical role in overcoming kinetic barriers to dolomite precipitation. This study explores the potential of dolomite crystal morphology as a diagnostic tool for identifying microbial contributions, integrating findings from laboratory simulations and sedimentary records.

Controlled experiments reveal that microbial processes produce distinct proto-dolomite crystal morphologies under varying environmental conditions. Cyanobacterium Leptolyngbya boryana induces proto-dolomite precipitation in brackish water, forming characteristic “double-spherical” crystals with hollow interiors and organic inclusions. In contrast, the halophilic bacterium Vibrio harveyi promotes the formation of single-spherical proto-dolomite crystals with unique "pinhole" features on their surfaces, indicative of microbial residue. These results highlight the species-specific influence of microbes on crystal morphology and the critical role of environmental conditions such as Mg/Ca ratios in shaping these mineralization pathways. Sedimentary dolomites from the SG-1 borehole in the Qaidam Basin (NE Tibetan Plateau) predominantly exhibit single-spherical morphologies with surface pinholes, closely resembling those produced by Vibrio harveyi in the laboratory. Although cyanobacterial fossils are present in the sediments, the observed dolomite features strongly suggest that halophilic bacteria were the primary mediators of dolomite precipitation in this system.

This study demonstrates that dolomite crystal morphology can serve as a proxy for microbial mediation in carbonate systems. By integrating experimental and sedimentary evidence, these findings advance our understanding of biogenic dolomite genesis and provide insights into reconstructing paleoenvironmental and biogeochemical conditions.

How to cite: Zhao, Y., Han, Z., Han, C., Wang, Z., and Gao, X.: Dolomite Crystal Morphology as an Effective Indicator of Microbial Origins: Evidence from Experimental Simulations and Sedimentary Records, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1153, https://doi.org/10.5194/egusphere-egu25-1153, 2025.

  Authigenic calcite abundantly forms during various diagenesis stages of shales. It meticulously records information on diagenetic fluid (organic/inorganic) migration and fluid-rock interactions, is important for understanding the burial diagenetic evolution, tectonic history, burial history, hydrocarbon generation and accumulation in sedimentary basins. During early burial diagenesis, the sulfate-methane transition zone maintains high porewater alkalinity through anaerobic oxidation of methane, promoting calcite nodule formation. Upon entering the hydrocarbon generation window, periodic opening and closing of fractures occur at lamina interfaces due to overpressure from hydrocarbon phase transitions and crystallization forces. In these fractures, calcite solubility decreases with fluid pressure reduction, leading to fibrous vein precipitation under strong overpressure conditions and bladed or equant crystal formation under weak overpressure conditions. Recrystallization processes controlled by the Ostwald mechanism. Additionally, authigenic calcite preserves characteristics reflecting multiple sources and distinct evolution stages, resulting in notable isotope fractionation features, the carbon isotope features represent cumulative results of various processes. Utilizing physical and numerical simulations based on burial conditions aids in analyzing authigenic calcite genesis and reconstructing the diagenetic environment in which it formed.

How to cite: Wang, Y., Cao, Y., Wang, J., and Liang, C.: Characterization and genesis of authigenic calcite in multiple diagenetic stages of shales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2823, https://doi.org/10.5194/egusphere-egu25-2823, 2025.

The co-evolution of life and minerals has profoundly shaped Earth's biological and geological history, with skeletal biomineralization emerging in eukaryotes over 800 Ma. Chitin, a key organic scaffold in modern biomineralization, was previously identified in fossils as old as the Cambrian (~505 Ma). Here, we extend this record by demonstrating the presence of fossilized chitin in 1-Ga acritarch-like fossils from the Lakhanda Lagerstätte, Siberia. These large spherical fossils (100–200 µm) align with the characteristics of acritarchs, organic-walled microfossils interpreted as cysts of planktonic protists. Spectroscopic analyses using nano-infrared spectroscopy of acritarch-like fossils showed molecular features diagnostic of chitin, including amide I and II bands and polysaccharide-related bands. These findings push back the timeline for chitin utilization in protists by 500 Ma, demonstrating its role in early biomineralization processes. This discovery highlights the significance of chitin in early protist evolution and its role in shaping biomineralization pathways. It also underscores the potential of advanced spectroscopy techniques to reveal the chemical and biological signatures of ancient life with unprecedented precision.

How to cite: Mehta, N., Bekker, A., Waeytens, J., Podkovyrov, V., Conrad, L., Baert, K., and Bonneville, S.: Chitin detected in 1.0 Ga old acritarch-like fossils from Lakhanda Lagerstätte and its implication for skeleton biomineralization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3102, https://doi.org/10.5194/egusphere-egu25-3102, 2025.

Late Cretaceous Kawagarh Formation, from Hazara Basin of northern Pakistan, exhibit extensive diagenesis including dolomitization, which significantly impacts its reservoir potential. In this study we investigated the processes that drove dolomitization in Kawagarh Formation through integration of petrographic analysis and carbon-oxygen isotope geochemistry. Thin sections optical microscopy revealed various dolomite textures, including planar-euhedral and non-planar-anhedral crystals, as well as evidence of recrystallization and porosity enhancement. Multiple textural indicated the multiple phases of dolomitization associated with variable diagenetic conditions.

Carbon (δ¹³C ) and oxygen (δ¹⁸O) isotope analysis of dolomite showed the distinct geochemical signatures indicative of dolomitizing fluid sources. These isotopes suggested a mixed origin, involving marine and meteoric fluids, with potential contributions from hypersaline brines during burial diagenesis. The spatial and isotopic variability suggested that dolomitization was influenced by tectonic activity and stratigraphic controls, which resulted in highly heterogeneous in porosity and permeability.

The findings from this study provided new insights into the diagenetic history of the Kawagarh Formation and enriched our conception of dolomitization mechanisms in analogous settings. The study highlighted the critical role of integrated petrographic and isotopic approaches in unraveling complex diagenetic processes, with implications for reservoir characterization and hydrocarbon exploration.

How to cite: Rehman, S. U., Munawar, M. J., and Ahsan, N.: Geochemical and Petrographic characterization of dolomitized carbonates in Kawagarh Formation, Northern Pakistan , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3153, https://doi.org/10.5194/egusphere-egu25-3153, 2025.

The reconstruction of the burial depth experienced by sedimentary successions before their uplift is crucial for various geological applications, such as thermal history analysis, subsidence reconstruction in sedimentary basins, reservoir quality prediction and, more in general, the tectonic evolution of fold-and-thrust belts. A commonly used method for addressing this problem in clastic sequences is low-temperature thermochronology (LTT), including techniques such as (U-Th)/He and fission-track analysis (AFT) on apatite grains, or organic matter maturity indices. However, these methods have two main limitations: 1) they are T-dependent, requiring knowledge or, more commonly, assumptions about the geothermal gradient for the studied sedimentary sequence over the considered time span, which can be challenging for deep-time analysis; and 2) these techniques are most effective at temperature higher than 60°-80° for (U-Th)/He and 120° for AFT. This means that for regions with a normal geothermal gradient of 30°C/km or lower (e.g., foreland basins), low-T thermochronology is less reliable for determining burial depth of less than 2-4 km experienced by rocks before exhumation.

In this contribution we aim to address these limitations by filling the “blind window” of LTT and avoiding uncertainties related to the past geothermal gradient. We do this by using the degree of compaction in sand-sized clastic rocks (COPL-CEPL indexes analysis) as a proxy to estimate the minimum burial depth experienced by exhumed clastic sequences. We apply a compaction-driven approach coupled with diagenetic modelling to estimate the burial depth of clastic units exposed in the eastern Tertiary Piedmont Basin (TPB) which occupies an episutural position on the tectonic junction between the Alps and the Northern Apennines collisional belts. Due to its complex tectonic setting, the studied sedimentary succession has undergone a largely unknown post-depositional history, making it possible to test several regional burial/exhumation scenarios for the Eocene-lower Miocene sequence. Our results suggests that the eastern part of the TPB underwent to more burial than previously expected; this implies that it continued to subside and accumulate sediment until the end of the Miocene, with uplift and erosion likely beginning at the end of Miocene due to the combined effects of Northern Apennines contractional tectonic phase and the Messinian Salinity Crisis. Overall, this case of study demonstrates that the quantitative study of the degree of compaction coupled with diagenetic modelling can be a reliable tool for maximum burial reconstruction in the depth-temperature window where current low-T thermochronological methods hardly work.

How to cite: Stendardi, F., Tamburelli, S., and Di Giulio, A.: Reconstructing the burial history of uplifted clastic sequences using compactional indices and diagenetic modeling (a northern Italy case of study) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3679, https://doi.org/10.5194/egusphere-egu25-3679, 2025.

This study explores the formation of anthropogenic conglomeratic rock caused by the lithification of fluvial sediment through calcium leaching from historical paper mill sludge (PMS) deposits near Penicuik, Scotland. Calcium-rich waste generated by historic paper mill activities accumulated along the stream bank, resulting in localized cementation of sediment. Field observations identified lithified stream bed deposits beneath the PMS heaps, where natural sedimentary clasts were bound by calcium carbonate (CaCO₃). Microstructural analysis using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) revealed that the cementing material is predominantly calcite. This was further corroborated by X-ray Diffraction (XRD), confirming a calcite-rich mineralogical composition. Stable isotope analysis (δ¹³C and δ¹⁸O) suggested a mixed carbon source, with approximately 40% derived from atmospheric CO₂ and 60% from lithogenic origins, highlighting complex geochemical processes. The results demonstrate that calcium ions (Ca²⁺) leached from PMS dissolved into pore water, subsequently migrating into adjacent fluvial sediments. This facilitated the precipitation of calcite, binding sediment grains into a cohesive structure and forming an anthropogenic conglomerate. This process mimics natural lithification mechanisms but occurs at the Earth's surface over significantly shorter timescales, bridging natural and anthropogenic geological systems. This anthropogenic lithification challenges conventional sedimentary rock classifications and has broader implications for waste management, pollutant immobilization, and carbon sequestration. By illustrating the interaction of industrial waste with natural sedimentary environments, the study emphasizes human influence on geological processes and provides insights into the evolving role of industrial byproducts in shaping modern sedimentary systems.

How to cite: Alam, M. J. and MacDonald, J. M.: Leaching of Legacy Paper mill Sludge promotes Lithification through cementation of fluvial sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4473, https://doi.org/10.5194/egusphere-egu25-4473, 2025.

Circulation of silica-bearing hydrothermal fluids along faults affects petrophysical and mechanical properties of fault-related rocks by modifying their texture and mineralogy, with strong implications on geofluid storage and seismicity in the shallow crust. However, in the subsurface, it is extremely difficult to predict the geometry of silicified rock volumes along and around fault zones as well as their petrophysical properties and, therefore, outcrop analogues can provide important insights. The Kornos-Aghios Ioannis Fault (KAIF) on Lemnos Island (Greece) is a silicified extensional fault system active at shallow depth (<1 km) that is well exposed over 10 km length and juxtaposes volcanic rocks against turbidite sandstones. In this study, we investigate the distribution, petrophysics and mineralogy of silicified rocks along two across-fault transects through a multi-analytical approach that combines data from X-ray diffraction analysis, Hg-intrusion porosimeter, digital image analysis, X-ray micro-computed tomography and unsteady-state gas permeameter. The permeability of silicified fault cores (i.e. breccias, cataclasites, ultracataclasites), characterized by quartz contents >70 wt. %, decayed of 3 orders of magnitude (from 10⁰ to 10^-3 mD) with respect to pristine host rocks as pore space was occluded by silica cements. In fault damage zones, porosity of massively silicified sandstones strongly varies in the range 2-13% because of the presence of dissolution intragranular and intercrystalline pores whose formation is strongly controlled by the mineralogy (i.e. microcrystalline silica, sulphides and feldspars are preferentially dissolved). However, permeability of these massively silicified rocks remains low (<0.01 mD), regardless of their porosity, due to the low connectivity of the pore network. In the silicified volume characterized by reduced permeability, that extends 100’s of meters from the master fault plane being locally greater than the damage zone, the permeability drop produced by cementation is partially counterbalanced by higher fracture density and connectivity because of increased rock brittleness (UCS increases up to 30% compared to pristine host rocks). Moreover, all the samples analyzed show that porosity values are sensitive to pressure and strongly decrease with increasing confining pressure (up to 17 MPa). Our results show that hydrothermal silicification along faults may strongly degrade the reservoir quality in the surrounding area (100’s of meters from the master fault plane) where its effect is only locally counterbalanced by an excess permeability produced by dissolution, fractures and subsidiary faults. However, the intensity and extension of silicification are heterogeneous along-fault strike and fault segments not affected by hydrothermal silicification can interrupt the along-strike continuity of low-permeability silicified fault rocks.

How to cite: Berio, L., Balsamo, F., Storti, F., Bezerra, F. H., Brito, M. F., and Rodrigues, M. A. F.: The impact of fault-controlled hydrothermal silicification on the petrophysical properties of sandstones: insights from the Kornos-Aghios Ioannis Normal Fault (Lemnos Island, Greece), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4528, https://doi.org/10.5194/egusphere-egu25-4528, 2025.

Carbonates are ubiquitous in Earth surface systems, such as sediments and cements. Contents of minor cations in carbonates can be considered as proxies of environment of formation involving stages of nucleation, growth and transformation. Thermodynamic models of carbonate solid solutions can help with this, also setting reference levels for kinetics and for interpreting the measurable variations of their composition (R_d values of metals) in time (growth rate) and in space (zoning). This message is illustrated on a few topics from my past studies facilitated by GEMS codes (https://gems.web.psi.ch).

Authigenic rhodochrosites in anoxic sediments of Baltic Sea deeps [1]. A (Mn, Ca, Mg, Sr, Ba, Fe)CO₃ solid solution model was refined using the sediment profiles data and Gibbs Energy Minimization (GEM) “dual thermodynamic” (DualTG) approach to estimate all binary regular interaction parameters, consistent with the  predictions in (Lippmann 1980). In the underlying thermodynamic model, porewater pH, pe, alkalinity, dissolved Mn, Fe, and S levels were controlled by equilibrium with rhodochrosite-mackinawite-greigite mineral buffer. The model matched well the observed porewater- and carbonate composition, predicting its non-linear response to variations in Mn loading, alkalinity and salinity of the sediment-porewater system.

Eu^III coprecipitation in calcite under widely different conditions (R_d datasets for high pCO₂; normal seawater; high-pH solutions) [2]. No binary solid solution with any of seven Eu^III endmember candidates could reproduce all three datasets. This was only possible with a ternary EuH(CO₃)₂ – EuO(OH) – CaCO₃ ideal solid solution constructed with DualTG approach, and consistent with TRLFS data.

Sr in calcite and Ca in strontianite [3]. (Ca,Sr)CO₃ solid solution system with non-isostructural endmembers was investigated in a stepwise approach from atomistic to thermodynamic modelling. Binary solid solution phases with calcite- or aragonite structure have nearly symmetric moderate non-ideality. However, calculations of equilibria including both phases resulted in strongly asymmetric ‘‘miscibility gap” with ~0.3% Sr in calcite and ~3.0% Ca in strontianite. The same picture was obtained using a DQF binary solid solution model in GEM calculations of Lippmann diagrams.

Growth rate dependence of uptake of divalent ions (R_d) in calcite [4]. These facts cannot be explained by equilibrium aqueous – solid solution partitioning, and need to consider intricate relations between speciation, particle growth, adsorption, surface entrapment, and solid solution formation. Two existing Growth Surface Entrapment- (Watson 2004) and Surface Reaction Kinetics (DePaolo 2011) models could be merged into a simple Unified Uptake Kinetics equation implemented and used in GEMS.

These studies benefited from DualTG calculations that use capabilities of GEM to compute chemical potentials of elements in (meta)stable systems [5]. Aspects of DualTG “streamlining” to obtain saturation index SI of solid solutions are discussed.

References

[1] Kulik D.A., Kersten M., Heiser, U., Neumann T. (2000): Aquat. Geochem. 6, 147-199.

[2] Curti E., Kulik D.A., Tits J. (2005): Geoch. Cosmoch. Acta 69, 1721-1737.

[3] Kulik D.A., Vinograd V.L., Paulsen N., Winkler B. (2010): Phys. Chem. Earth 35, 217-232.

[4] Thien B.M.J., Kulik D.A., Curti E. (2014): Appl. Geochem. 41, 135-150.

[5] Kulik D.A. (2006): Chem. Geol. 225, 189 – 212.

How to cite: Kulik, D.: Carbonates as (meta)stable solid solutions: Thermodynamic and kinetic insights , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6064, https://doi.org/10.5194/egusphere-egu25-6064, 2025.

Jurassic Shaximiao Formation is an important tight gas reservoir in southwest Sichuan. In this study, thin section identification, scanning electron microscopy (SEM), X-ray diffraction (XRD), Cathodolumines- cence(CL), electron probe analysis, fluid inclusions and isotopic analysis were used to investigate the characteristics of the reservoir and the influence of diagenesis on the reservoir. And the following research results are obtained.First, the reservoir rock types of Shaximiao Formation in this area are primarily feldspathic sandstone and lithic feldspathic sandstone and secondarily lithic sandstone and feldspathic lithic sandstone. Second, the reservoir performance of feldspathic sandstones is much better than that of lithic sandstones. Feldspathic sandstones are mainly vertically distributed in the first and second sub-members of the second Member of Shaximiao Formation and laterally the most developed in the eastern area.Third, the reservoir Spaces in southwest Sichuan are mainly primary intergranular pores and secondary intergranular pores. Compaction plays a dominant role in the reduction of porosity, and due to the protective effect of chlorite coating, the porosity in southwest Sichuan is reduced by 23.45%. Cementation played a secondary role in the reduction of porosity, which reduced the porosity of southwest Sichuan by 12.4% respectively. On the contrary, dissolution plays a positive role in the increase of porosity, which increases the porosity of southwest Sichuan by 4.52%.In conclusion, Compaction and cementation lead to reservoir densification in Shaximiaoformation. Chlorite cementation protects the primary porosity to a certain extent, and dissolution is the main factor to increase the porosity.

How to cite: Li, J. and Qiu, L.: The influence of sandstone diagenesis on reservoir of Shaximiao Formation in southwest Sichuan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6530, https://doi.org/10.5194/egusphere-egu25-6530, 2025.

In his 1897 article, Friedrich Wilhelm Ostwald wrote that “during departure from any state, and the transition to a more stable one, not the under given circumstances most stable state is reached, but the nearest one“. The word “nearest” essentially gave rise to the widespread interpretation that during a phase transition not the thermodynamically most stable but a metastable phase forms first, which is usually referred to as Ostwald’s step rule. It is considered a general rule rather than strict physical law, although its precise physical basis seems not fully understood on a mechanistic level, despite its potential importance for mineral formation under Earth’s surface conditions.

While Ostwald’s step rule is commonly explained through the classical nucleation theory, there are several inconsistencies that are not explained by this theory. One is that a transition to the stable phase cannot be forced by strongly increasing the driving force (supersaturation), and also adding seed crystals may not help. This conundrum particularly applies to the two most abundant minerals in Earth’s sedimentary record, dolomite and quartz (Meister et al., 2014), which are observed not to precipitate directly from aqueous solution as long as the solution remains supersaturated with respect to one of their metastable polymorphs.

Here, an alternative concept is proposed that would be consistent with Ostwald’s (1897) original formulation and with several observations from natural environments and laboratory experiments. The difference lies in the translation of the word “nearest”, not in a thermodynamic sense as “having a similar Gibbs energy”, but kinetically as “having the smallest energy barrier”. In the latter case, Ostwald’s step rule would become an actual physical law, equivalent to the Arrhenius law. This goes along with the concept that not the thermodynamic barrier of nucleation but some kinetic barrier, not affected by supersaturation, is responsible for the efficient inhibition of the phase. Inhibition (giving rise to Ostwald’s step rule) would then not be a matter of nucleation but of growth.

Meister et al. (2014) Early diagenetic quartz formation at a deep iron oxidation front in the Eastern Equatorial Pacific. GCA 137, 188–207.

How to cite: Meister, P.:  Ostwald’s step rule: rule of thumb or strict physical law?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6901, https://doi.org/10.5194/egusphere-egu25-6901, 2025.

Two areas in Sweden are currently being investigated by the Swedish geological survey as possible sites for geological storage of CO₂. One of them is in the Baltic Basin south of Gotland, where Cambrian sandstone from the Faludden Member (Borgholm Formation) has been recognized as a suitable storage reservoir. The Faludden reservoir is a well-sorted, fine- and medium-grained quartz arenite with high porosity and permeability. Here, we report new results obtained from scanning electron microscope analyses of the secondary mineralogy of the Faludden sandstone and implications for its CO₂ storage potential. Our study shows that there are several phases of secondary mineralization in the sandstone, which to a varying degree affects the interaction with injection and storage of CO₂. The results provide information on the diagenetic history of the reservoir and assessment of depth-related P-T mineralizations. The most common secondary mineralization is a patchy carbonate cement. The patches, embedding several detrital grains, are round to irregular with individual diameters of up to 5 mm. The carbonate is mostly dolomite with microscale variations towards more Mn- and Fe-rich compositions. Calcite is also present, especially in connection to occasional microfractures. In general, patchy cementation is favorable for CO₂ storage since it can prevent compaction, while still allowing a relatively high porosity and permeability. Quartz cement in the Faludden sandstone is limited to scattered occurrences of fringed overgrowths at the edges of detrital quartz grains. However, we observe that the amount of secondary quartz is increasing with depth in the Baltic Basin. Subcropping lower Cambrian sandstone beds, such as the När and Viklau sandstone members are often more or less completely cemented with quartz. Thus, the process of secondary quartz mineralization is an important factor to consider when assessing the optimal depth range for CO₂ storage in the basin. Other secondary minerals in the Faludden sandstone include pyrite, apatite, iron(titanium)oxides and small amounts of clay minerals (illite and kaolinite). In some samples there is evidence of dissolution of both quartz cement and dolomite, introducing a secondary microporosity. This study confirms that the sandstone from the Faludden Member is a suitable reservoir rock for CO₂ storage. A thorough understanding of geological processes, including reservoir diagenesis, is essential for predicting the physiochemical interactions between the injected CO₂ and the reservoir rock.

How to cite: Lindgren, P., Erlström, M., and Lindström, S.: Impact of diagenesis on the suitability of reservoir rocks for CO2 storage - Examples from a Cambrian sandstone in the Baltic Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10495, https://doi.org/10.5194/egusphere-egu25-10495, 2025.

Introduction

Carbonate concretions form at shallow burial depths (Raiswell, 1971), with most bicarbonate ions derived from the anaerobic oxidation of organic matter (Claypool and Kaplan, 1974). Specifically, spherical carbonate concretions are proposed to grow concentrically through the diffusion-driven outward migration of the carbonate supersaturation front (Yoshida et al., 2018). Consequently, the center-to-edge isotopic and geochemical profiles of spherical carbonate concretions provide valuable records of pore-water evolution. Zoned spherical concretions, which exhibit distinct zonation, can potentially preserve traces of multiple diagenetic processes. This presents a unique opportunity to reconstruct the temporal and spatial evolution of the pore-water environment at higher resolution. This study presents a detailed analysis of zoned spherical concretions from the Miocene marine sediments of the Atsuta Formation, Japan, to elucidate their formation processes.

Results and Discussion

Well-preserved zoned spherical concretions from the Atsuta Formation are subdivided into two distinct zones: a spherical nucleus (Inner-Concretion) and an outer crust (Outer-Concretion) (Fig. 1). Its spherical shape and the presence of fossilized mud shrimp claws at the center suggest a concentric growth mode. Both the Inner- and Outer-Concretion are inferred to have formed rapidly at shallow burial depths, based on the following evidence:

• Fossilized fecal pellets and mud shrimp claws were found in both the Inner- and Outer-Concretions, exhibiting no signs of compaction.
• The carbonate content was 83.0 ± 0.5 wt% in the Inner-Concretion and 79.4 ± 0.1 wt% in the Outer-Concretion, indicating precipitation within porous sediments prior to significant compaction.
• The average stable oxygen isotope ratios (δ¹⁸O) were +0.63 ± 0.77‰ (n = 76) in the Inner-Concretion and +0.92 ± 0.48‰ (n = 44) in the Outer-Concretion, suggesting the absence of isotopic fractionation effects related to burial depth.

Detailed measurements of stable carbon isotope ratios (δ¹³C) (n = 129) revealed characteristic trends in each zone, with abrupt changes at their boundaries. The δ¹³C values in the Inner-Concretion steadily increased from -15‰ near the center to +10‰ toward the edge, reflecting isotopic fractionation associated with enhanced methanogenesis. In contrast, δ¹³C in the Outer-Concretion was approximately -15‰ and relatively constant. The presence of pyrite throughout the concretion suggests that at least the Outer-Concretion formed within the sulfate reduction zone.

These findings collectively indicate a shift in dominant organic matter degradation processes from methanogenesis to sulfate reduction, a trend that deviates from the classical geochemical sequence of sedimentary environments (Berner, 1981). A plausible hypothesis is that methanogenesis occurred entirely within the sulfate reduction zone, potentially as a localized microenvironment around organic matter during the formation of the Inner-Concretion.

How to cite: Praet, A., Yoshida, H., Muramiya, Y., Kano, A., Kido, T., Katsuta, N., and Umemura, A.: Zoned spherical concretions from Atsuta Formation, Japan: a record of rapid geochemical shifts in early diagenesis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11167, https://doi.org/10.5194/egusphere-egu25-11167, 2025.

The Groningen gas field, Europe’s largest onshore gas reservoir, has undergone extensive compaction due to prolonged gas extraction, leading to surface subsidence and seismicity. Understanding the diagenetic processes controlling reservoir quality is essential for managing these risks. This study investigates the role of dolomitization and associated diagenetic alterations in shaping the petrophysical and geomechanical properties of the Rotliegend sandstones. Detailed petrographic analysis, incorporating optical and scanning electron microscopy, reveals that early dolomite cementation significantly reduced primary porosity while preserving intergranular volume (IGV) and enhancing mechanical stability by inhibiting grain rearrangement and compaction during burial. Dolomite cementation was particularly prominent in zones proximal to mudstone interbeds, indicating its strong depositional and diagenetic control. Authigenic clays, including illite, smectite, and chlorite, were found to inhibit late-stage quartz cementation, preserving reservoir quality in specific zones. Burial depth and prolonged thermal exposure intensified quartz overgrowths and illite development, particularly in deeper sections of the reservoir. Clustering patterns among authigenic minerals revealed strong positive and negative associations: Illite, illite-smectite, and chlorite frequently co-occur in fine-grained sandstones, particularly in northern wells, where their abundance reduces pore space and permeability. Conversely, high dolomite content negatively correlates with clay minerals and quartz cement, reflecting the inhibitory role of early dolomitization on subsequent diagenetic mineral development. Quartz cementation plays a minor role in compaction due to shallow burial conditions and the presence of clay rims around grains, which limited growth of quartz cements. Mechanical compaction primarily affected sandstones lacking dolomite, where authigenic clay content and quartz cementation are higher, correlating with higher porosity and permeability than sandstones that are dolomitized. This study highlights the interplay between depositional setting, diagenetic timing, and burial history in shaping reservoir quality and stability. By linking petrographic trends to geomechanical behavior, these findings provide critical insights into mitigating subsurface risks associated with gas extraction in Groningen and analogous reservoirs worldwide.

How to cite: Mulder, S. and Miocic, J.: The Role of Dolomitization and Clay Rims in Shaping Sandstone Evolution: Insights from the Groningen Gas Field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12855, https://doi.org/10.5194/egusphere-egu25-12855, 2025.

Calcite, the most abundant carbonate mineral in Earth’s crust, is at the heart of many environmental and technological processes. As part of the geological carbonate-silicate cycle, calcite dissolution and precipitation are central for the regulation of atmospheric carbon dioxide levels on geological timescales. Moreover, calcite is involved in buffering of sea- and freshwater pH values and biomineralization of marine organisms. Important technological applications of calcite are the use in concrete and as a storage material for anthropogenic carbon. Since most processes on calcite take place in an aqueous environment, they are governed by the structure and properties of the calcite-water interface. Consequently, there has been a large body of research establishing a detailed understanding of the interface between the most-stable calcite (10.4) surface and water. This includes the development of so-called surface complexation models describing the surface speciation and properties of the calcite-water interface in thermodynamic equilibrium with aqueous solutions of varying composition. An important part of these models is the description of the species at the interface, which heavily depends on the protonation and deprotonation of surface-bound water and interfacial carbonate groups. However, the de-/protonation of calcite is difficult to quantify experimentally due to calcite dissolution and carbonate buffering. Here, we apply interface-sensitive vibrational sum frequency generation (SFG) spectroscopy to directly assess the water species present at the calcite-water interface at high pH. With SFG spectroscopy, we can measure the vibrational spectrum of interfacial species, providing insights into the molecular organization and chemical environment at the interface. We aim to quantify the change of hydroxyl species present at the interface with increasing pH to quantify the deprotonation constant of surface-bound water contributing to the development of more-accurate surface complexation models.

How to cite: Dickbreder, T., Heberling, F., and Backus, E.: Investigating the Water Organization at the Calcite (10.4)-Water Interface at High pH, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13621, https://doi.org/10.5194/egusphere-egu25-13621, 2025.

Marine carbonates are archives of geochemical proxies, such as e.g. Sr and U-Pb isotopes, which potentially can be utilized in the reconstruction of past climate conditions, ancient seawater composition and/or their alteration during burial and fluid interaction, if interpreted accurately. The ability to confidently reconstruct environmental conditions in the past times is of great importance since they can be linked with changes in the biosphere. For example, the Ediacaran-Cambrian transition was a period where significant evolutionary change modified the biosphere towards appearance of extant animal clades and the establishment of metazoan-dominated ecosystems. Any contribution towards an intact, continuous record of environmental conditions through multiple proxies will help to understand better the timing, nature and sequence of events that preceded or accompanied such changes in biodiversity. However, carbonate rocks are susceptible to numerous post-depositional processes (such as: oxidative weathering, diagenesis, burial, lithification, deformation, dissolution and reprecipitation), which may alter the geochemical record. Additionally, detrital components may increase the complexity of the geochemical signature and the carbonate composition, particularly in shallow marine settings with variable continental run-off.

Thus, we have to understand and identify the presence or absence of such processes, before extracting meaningful geological information from these archives. Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA-ICP-MS), is a tool that offers spatial resolution when performing geochemical analyses, which may help to interpret the geochemical data more confidently. In this work, we combine observations from Sr and U-Pb isotopic systematics supported by trace element abundances to identify domains that are indicative of post-depositional processes, over protracted time and variable in their extent. The sample material is taken from drill cores in Namibia, obtained within the frame of the GRIND project, which aims to investigate the late Edicaran period. Situated in the south of Namibia, the Gariep belt was geologically active during the Pan African orogenesis and possibly affected by the Atlantic Ocean opening.  

How to cite: Paul, A. N., Gerdes, A., Cantine, M., and Ovtcharova, M.: Progress in the evaluation of U-Pb dates of late Ediacaran carbonate rock from drill cores through simultaneous Sr isotope analysis (Laser Ablation – Split Stream – Inductively Coupled Plasma – Mass Spectrometry), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15410, https://doi.org/10.5194/egusphere-egu25-15410, 2025.

Within syn-rift basinal settings, the juxtaposition of rift-related clastic deposits in the hanging wall of basin-bounding normal faults against a footwall of crystalline basement is a recurrent structural setting where plays for hydrocarbon exploration or carbon storage can be found. Here, fault-controlled fluid flow can significantly influence and change the petrophysical properties of the fault zone and host rocks over time by means of mineralization and cementation, ultimately controlling fluid pathways. Investigating the timing and extent of fluid flow along major faults permits us to better understand the host rock properties and if these can potentially be favourable for subsurface extraction and storage.

Here, we present a detailed investigation of the timing and paragenesis of fluid flow along the well exposed Helmsdale Fault in NE Scotland. The Helmsdale Fault is a major tectonic feature that bounds the western side of the Inner Moray Firth Basin, which developed during rifting in the Late Jurassic. The hanging wall consists of the Late Jurassic (Kimmeridgian-Tithonian) Helmsdale Boulder Beds that are made of alternating debris flow to fault scarp deposits, whereas the footwall is composed of the Helmsdale Granite (Silurian-Devonian). There is ample evidence of paleo-fluid flow along the Helmsdale Fault in the form of calcite cementation and widespread calcite veining in both the hanging wall and in the footwall, locally making up to 5 m thick fault cores of stacked crack-seal veins. U-Pb calcite dating of fossils, veins and cements shows an initial fluid flow event that quickly follows diagenesis in the hanging wall and spans from 147 to 113 Ma, followed by a later reactivation of the fault system between 86-60 Ma. The spatial distribution of the dated calcite veins shows a clear localization over time of fluid flow along the main faults within the footwall.

Carbonate stable isotope analysis, combined with the salinity of the fluid inclusions in the calcite veins, has revealed a marine fluid composition of the calcite vein network over time, irrespective of the structural domain within the fault zone. Furthermore, clumped isotope thermometry shows a gradual temperature increase towards the footwall (35 to 65 °C), but fluid inclusion microthermometry on secondary fluid inclusions also reveals that these fluids could originally have been much hotter (up to c. 80 °C). The variability in the data suggests that two fluid pathways were active at different moments in time, with one being locally sourced in the hanging wall sediments, and the second percolating upwards along the main faults within the Helmsdale Granite. Occurrence of calcite veins derived from meteoric fluids is documented in the youngest dated vein network (60 Ma) and likely related to the later stages of regional uplift.

Our results suggest that the evolution over time of the petrophysical properties of the hanging wall with progressive mineralization and cementation exert a critical control on future fluid pathways as well as localization and style of subsequent fault deformation.

How to cite: Demurtas, M., Sharp, I., Pasqualetto, L., Krüger, Y. S., Drost, K., Meckler, A. N., and Rotevatn, A.: Fluid flow history and paragenesis along a syn-rift basin bounding fault: the Helmsdale Fault (NE Scotland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15488, https://doi.org/10.5194/egusphere-egu25-15488, 2025.

Sediment archives are invaluable for reconstructing past environmental conditions. Clastic sediments are formed through physical processes, such as weathering of rocks, during which minerals are released from the parent material, transported, and eventually deposited. However, both transport and depositional processes—such as abrasion, mixing, or chemical dissolution—can alter the original signals preserved in the sediment. Water plays a central role in these transformations by promoting processes like dissolution and recrystallization of minerals. This is particularly relevant for sediments deposited in stagnant waters such as lakes or marine basins. Similarly, infiltration of surface water flows into sediments, enhances chemical reactions and facilitates the transformation of minerals. Fine-grained sediments, such as sands or clays, are especially reactive due to their large specific surface area, which increases their interaction with fluids.

To determine the original composition, isotopic signatures, or depositional and source age of the sediment and the contained minerals, it is crucial to know whether, and to what extent, chemical alterations have occurred during and after the deposition. A critical factor in the analysis is whether the sediment layer represents a closed or open system. In closed systems, the original chemical signatures are preserved, as no significant element exchange occurs with the surrounding environment. In contrast, in open systems, interactions with water can lead to the loss or accumulation of elements, which can alter the sediment's original composition at the time of deposition, making it difficult to interpret its geochemical and mineralogical history.

In a comprehensive mineralogical and geochemical study combined with field observations, we analyzed solids and eluates of 250 sediment samples from the Miocene the Northern Alpine Foreland basin. Additionally, we separated and analyzed the mineral chemistry of over 30 samples (also clay fraction) using SEM. We examined the mineral textures with high-resolution microscopy. Furthermore, we performed extensive leaching experiments to study the mobilization behavior of the contained elements under “open system conditions”.

The results of this study revealed the following: 1) A significant proportion of the minerals in the sediments are newly formed. 2) Experiments showed that processes like dissolution and precipitation can proceed very quickly (within hours to days), depending on factors such as pH, Eh and concentration of dissolved elements. However, these processes can be halted when the sediment runs dry or when chemical equilibrium in the system is achieved. 3) In open-system sediment profiles, water infiltration causes the leaching of elements that are transported to deeper stratigraphic layers, where they precipitate and form new mineral phases.

A key observation is the elution behavior of arsenic: In sediments known to represent open systems, arsenate is not mobilized in the elution tests, because it is fixed in the mineral phases or is already desorbed during the water exchange. In closed systems, elevated arsenic concentrations in the eluate indicate that these sediments have not undergone significant post-depositional water exchanges. The analysis demonstrated that arsenic is predominantly adsorbed on phyllosilicates. Accordingly, an elution test is a reliable indicator of water exchange in sediments after their deposit.

How to cite: Aßbichler, D., Weichselgartner, N., Diesner, N., Kayalar, M., Otte, C., Kellner, M., Henning, H., and Tautenhahn, S.: Arsenic — an indicator for post-depositional water exchange in sediments at neutral to alkaline conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16523, https://doi.org/10.5194/egusphere-egu25-16523, 2025.

Diagenetic processes alter petrophysical properties, such as porosity and permeability, of clastic sediments. An understanding of these processes is therefore pivotal for any reservoir quality assessments. Thermal exposure is among the crucial factors influencing diagenesis and can vary significantly in widespread formations, e.g. due to regional variations of the burial history. Especially quartz overgrowth is controlled by temperature and we here demonstrate the effect of spatial thermal exposure variability on the degree of cementation. Our field example is from the aeolian Jurassic Etjo sandstone that was buried by the Lower Cretaceous Paraná-Etendeka Large Igneous Province in Namibia and we show data from outcrops lying >100 km apart from each other – named Waterberg, Mt. Etjo, and Gamsberg. 

Our petrographic analysis shows significant differences in the degree of compaction and cementation between the localities (Salomon et al., 2024). Waterberg samples have a mean quartz cement volume of 6.5 % and intergranular volume (IGV) of 23.7 %. Mt. Etjo samples have a higher quartz cement volume (15.4 %), but lower IGV (19.7 %). As Waterberg samples had an on average 72 % larger nucleation surface area available for quartz cement growth than samples from Mt. Etjo, we argue that the latter locality has experienced a higher thermal exposure. This is supported by a kaolinite-to-illite transformation that only occurs at Mt. Etjo. We attribute the temperature differences to the localities’ position underneath the volcanic cover with Mt. Etjo being closer to the volcanic center than Waterberg. Gamsberg samples have a very high mean IGV of 30.7 % and very high mean quartz cement volumes of 24.3 %. Here, two quartz growth generations are evident and separated by an exhumation period of the sandstone. The origin of the first generation is yet unclear, whereas the second one is also attributed to the Etendeka burial. 

Our case study serves as a prime example for the variability in diagenetic character within a sandstone formation, depending on its geographic position. It underscores the importance of understanding spatial variabilities in the burial/temperature history when predicting the diagenetic properties of a reservoir rock. 

Reference: Salomon, E., Stollhofen, H., Caracciolo, L., Bonnell, L.M., Lander, R.H., Kittel, M., 2024. Burial of a sand sea: Heterogeneous compaction and cementation of the jurassic Etjo Formation, Namibia and what it tells. Marine and Petroleum Geology, 168, 107044.

How to cite: Salomon, E., Stollhofen, H., Caracciolo, L., Bonnell, L. M., and Lander, R. H.: Heterogeneous cementation and compaction in a sandstone and the role of temperature – an example from the Etjo Formation, Namibia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16554, https://doi.org/10.5194/egusphere-egu25-16554, 2025.

Carbonate concretions accompanied by elemental sulfur are found in many upper Miocene marine successions across the Mediterranean area (e.g. SE-Spain, Sicily, Apennine, Cyprus). Most of these rocks are characterized by molds of evaporitic minerals (mostly gypsum) suggesting an early (syngenetic) or late (epigenetic) diagenetic origin. In contrast to these findings, a case study from the Ripa dello Zolfo area in northern Italy lacks evidence of carbonate and sulfur replacement of preexisting sulfate minerals. An integrated approach including sedimentological, petrographical, stable isotope (carbon, oxygen, and multiple sulfur isotopes), and lipid biomarker analyses was used for the study of three main lithofacies: a) laminated lithofacies representing aphotic carbonate stromatolites enclosing fossils of filamentous sulfide-oxidizing bacteria; b) brecciated lithofacies deriving from the brecciation of carbonate stromatolites by mud injections; c) sulfur-bearing lithofacies deriving from the precipitation of thin laminae of elemental sulfur at or close to the sediment-water interface. The δ¹³C and δ¹⁸O values of authigenic carbonate minerals and δ¹³C of lipid biomarkers indicate that the initial formation of the laminated lithofacies was favored by organoclastic sulfate reduction in the shallow subsurface close to the sediment-water interface, producing sulfide that sustained dense microbial mats of sulfide-oxidizing bacteria at the seafloor. Calcification of the mats and consequent formation of stromatolites were possibly favored by nitrate-driven sulfide oxidation at the seafloor. The subsequent brecciation of the stromatolites was apparently the consequence of sulfate-driven anaerobic oxidation of methane (SD-AOM) in an underlying sulfate-methane transition zone (SMTZ). Focused fluid flow from a deeper zone was not only causing the brecciation of the stromatolites, but also delivered bicarbonate ions for the subsequent precipitation of additional, ¹³C-depleted calcite (δ¹³C values as low as -52‰). Along with bicarbonate, also hydrogen sulfide was produced by SD-AOM within an SMTZ in a zone below the stromatolites and was transported upwards. The oxidation of hydrogen sulfide at or close to the seafloor promoted the formation of elemental sulfur characterized by δ³⁴S and Δ³³S values close to coeval seawater sulfate. This study highlights that a multi-proxy approach has great potential for the reconstruction of spatially and temporarily separated biogeochemical processes in the shallow subsurface or at the seafloor (i.e., anaerobic oxidation of methane, sulfate reduction, sulfide oxidation) – processes that may induce the syngenetic formation of authigenic carbonate and sulfur deposits in marine sediments.

How to cite: Natalicchio, M., Birgel, D., Giunti, S., Guibourdenche, L., Pellegrino, L., Aloisi, G., Peckmann, J., and Dela Pierre, F.: Authigenic carbonate and native sulfur formation in Messinian (upper Miocene) marine sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17405, https://doi.org/10.5194/egusphere-egu25-17405, 2025.

Mediterranean sediments have registered some of the most exceptional Ba records in marine basins. Although Organic Rich Layers (ORLs) are less well studied, both sapropels and ORLs are characterized by marked increases in Ba content in response to productivity oscillations, as demonstrated by numerous data sets and sediment records. During sapropel deposition, barite was abundantly produced in the water column due to increased productivity and associated microbial processes involved in organic matter degradation. In this scenario, bacterial activity and extracellular polymeric substances (EPS) have been shown to be the main control of barite precipitation in the water column, which is further supported by experimental work and observations from microenvironments of intense organic matter mineralization in the ocean water column. Once accumulated in marine sediments, barite tends to be well preserved in both eastern and western Mediterranean basins, where the availability of sulphate in pore waters prevented dissolution. Thus, differences in barite abundance in sapropels compared to ORLs support differences in productivity rates, and also differences in primary producers and microbial processes. Indeed, differences in productivity types between modern eastern and western basins also support that such differences over time may have led to spatial differences in barite formation. The general decline in productivity, and hence microbial activity, across the Mediterranean basins during the Holocene is indicated by the remarkably low Ba content in recent sediments. Dissolution of barite through the water column is also important in modern environments and is still poorly understood in the past. Overall, a better understanding of the microbial processes involved in barite production and the factors controlling its preservation is required to further constrain the information captured by Ba proxies.

How to cite: Martinez-Ruiz, F., Monedero-Contreras, R., Monasterio-Guillot, L., Paytan, A., and Vasconcelos, C.: Controls on barite precipitation and preservation in Mediterranean sediments: from sapropel deposition to modern sedimentation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17872, https://doi.org/10.5194/egusphere-egu25-17872, 2025.

Early Eocene limestones in Tunisia exhibit notable variations in facies and thickness, indicative of a depositional environment primarily within a platform setting. Most planktonic-rich microfacies are deposited in slope-basin areas conducive to preserving organic matter. This study focuses on the Bou Dabbous Formation, a known source-rock explored in various wells across Tunisia. It aims to evaluate its potential as a tight reservoir through a comprehensive analysis of core samples from two outcrop analogs: Oued Kasseb (OK) and Ragoubet Tassera (TS) sections in northwestern Tunisia.

Rock-Eval pyrolysis of 42 samples revealed variable organic richness, with higher Total Organic Carbon (TOC) in the OK section (max TOC = 2.75 wt.%) compared to the TS section (max TOC = 1.11 wt.%). Tmax values ranged from 433°C to 454°C, indicating a predominantly mature to marginally mature stage of hydrocarbon generation. Hydrogen Index (HI) values classified the organic matter primarily as Type II, with some Type II/III, suggesting a planktonic marine origin under anoxic to suboxic conditions.

Inorganic analysis, including XRF and XRD analyses, showed significant lithological variations between massive limestone and marly limestone layers. Major oxides such as MgO and SiO₂ varied notably, with silica-rich layers prominent in the TS section and magnesian limestones in the OK section. Trace elements like Sr and S highlighted diagenetic processes and variations in paleoclimate, suggesting semi-humid conditions during deposition. The presence of pyrite, influenced by anoxic conditions and diagenesis, further supports these findings. The complex diagenetic processes affecting the Bou Dabbous limestones impact their petrophysical properties, including fractures, silicification, and cementation.

The region's significant tectonic activity has resulted in a complex fracture network, as observed in field studies and thin-section analyses. These fractures, partially filled with calcite and asphaltene, are attributed to compaction and tectonic stresses. Stylolites, formed by chemical compaction and bitumen-filled fractures, indicate the circulation of acidic solutions related to petroleum generation processes. These processes altered the primary pore system by either enhancing reservoir properties (such as fracturing and oxidation) or reducing and destroying porosity through cementation, mechanical and chemical compaction, and the precipitation of asphaltene, phosphate, and pyrite. This emphasizes the complexity of diagenetic controls on the porosity evolution. The brittleness index (BI) for the Bou Dabbous Formation, determined based on carbonate fractions, detrital content, and TOC percentages, was high, ranging from 0.84 to 0.98. This suggests a high fracturing sensitivity among the studied area's rocks.

Overall, the findings indicate that the Bou Dabbous limestones have potential as a tight reservoir with favorable conditions for unconventional hydrocarbon exploration, influenced by its significant organic content, mature hydrocarbon generation, and brittleness characteristics. These results underscore the formation's importance in regional petroleum exploration and development. Further investigations should be conducted on borehole cuttings, along with rigorous fracturing simulations, to realistically evaluate the potential of the Bou Dabbous Formation in Tunisia as an unconventional hydrocarbon reservoir within the explored petroleum system.

How to cite: Arfaoui, I., Omar, H., Singh, A., Rachdi, M., Montacer, M., Baudin, F., Collin, F., and Boulvain, F.: Tight Reservoir Potential of the Early Eocene Bou Dabbous Formation in Northwestern Tunisia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18386, https://doi.org/10.5194/egusphere-egu25-18386, 2025.

In addition to the widely acknowledged marine ferromanganese deposits, i.e., polymetallic nodules and cobalt-rich crusts, Fe-Mn (oxyhydr)oxides ubiquitously precipitate as micronodules in the oxic aquatic environments. Due to their micrometer-scale or even smaller size, ferromanganese micronodules have received limited attention until they were found to be one of the important rare earth elements and yttrium (REY)-holding phases in the deep-sea REY-rich mud, and noteworthily estimated to preserved a ~1.28-7.62 Tt Mn budget, exceeding that of nodules and crusts by at least two orders of magnitude. Combined with the increasing demands for critical elements in high-tech industries, the economic and scientific potential of micronodules, which could strongly scavenge trace elements from ambient environments, deserve to be revised.

In our study, Fe-Mn micronodules were hand-picked from surface sediments of the North-Western (NW) Pacific and the North-Eastern (NE) Pacific Clarion-Clipperton Fracture Zone (CCFZ) for morphological and in-situ geochemical analyses with field-emission scanning electron microscope (SEM), electron probe microanalyzer (EPMA) and laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS). The characteristic microbial-like mineralization structures, including the irregular aggregates of rod microbial-like particulates, biofilm, and the phalanxes of ellipsoid microorganisms, were commonly observed in micronodules. Their Mn/Fe ratios most frequently fall in the range of < 10 (46.1%), with a maximum value (reaching 698) that is much higher than the published EMPA data of polymetallic nodules. Unlike the continuous variation of elemental contents in nodules, the concentrations of some elements in micronodules, such as Al, Ca, K, Co, Ni, Cu, Sr, Mo and REYs other than Ce, showed a mutative tendency, being slowed down or even reversed, with the increase of Mn/Fe ratio in the ranges of Mn/Fe < 10 and Mn/Fe > 10. Whereas, the declining tendencies in Ce contents and Ce anomaly remained generally stable.

Considering the loose structure of Fe-Mn (oxyhydr)oxides, and after multiple comparisons, Mn/Fe < 5 is used here to distinguish hydrogenetic and mixed hydrogenetic-early diagenetic type (grouped into hydrogenetic type hereafter) from diagenetic type. Amounts of geochemical data of hydrogenetic Fe-Mn deposits (including micronodules, (macro)nodules and crusts) were collected. Comparative analyses reveal that both the hydrogenetic crusts (n = 289) and nodules (n = 159) have weaker positive Ce anomalies (avg. 2.23 and 2.97, respectively) than our hydrogenetic micronodules (n = 204, avg. 6.27). Combined with the similar Ce content in all three hydrogenetic ferromanganese deposit types, and the lower concentrations of other REYs in hydrogenetic micronodules, the migration of REYs (except for Ce) from micronodules to porewater is indicated.

All these findings demonstrated that the precipitation and aggregation of micronodules were predominantly controlled by the redox state of ambient pore water, even in surface sediments, and were largely influenced by microbial activities. The potential of ferromanganese micronodules to serve as a buffer in the enrichment of REYs and critical elements in pelagic sediments and an archive of the ambient redox conditions enhanced their value of further comprehensive and in-depth studies.

How to cite: Zhang, H., Dong, Y., Peng, Y., Zhou, J., and Chu, F.: Characteristics of ferromanganese micronodules in surface sediments of the tropical North Pacific Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19852, https://doi.org/10.5194/egusphere-egu25-19852, 2025.

The growing awareness of the relationships between minerals and microorganisms has deeply impacted the geosciences in the last decades. Microorganisms have been recognized to play a critical role in element cycles, resulting in the precipitation of minerals and in the formation of peculiar rocks (e.g. stromatolites and thrombolites) that punctuate the geological record. Moreover, the Earth history was characterized by episodes of massive accumulation of mineralized remains of microorganisms on the ocean floors, resulting in the formation of biogenous oozes that represent natural archives of past climatic and oceanographic variability. Finally, the rapid growth of minerals can act as a trap for microorganisms that can be perfectly preserved within the crystal lattice or fluid inclusions for millions of years. Such strict connections between the geosphere and the biosphere are mostly unknown to the general audience, although the impact of microbial (microorganisms) and nanoscopic (viruses) life on our society is emerging more and more. The project “Minerals & Microbes, a possible relationship: GEOMICROBIology for dummies” aims at showing the microbial life enclosed in minerals and rocks. Improving people awareness about the role of microorganisms in shaping the Earth will contribute to understand the importance of life as a “geological force”. The project GEOMICROBI aspires to raise such awareness throughout imaging (mostly by SEM high-definition photomicrographs) the "invisible life" hidden within minerals and rocks. Main target of the project is the creation of a photographic exhibition accompanied by informative conferences on the theme "Minerals & Microorganisms". This poster is intended to attract the attention of the international sedimentological community showing the first results of this dissemination initiative on mineral-microorganism interactions.

How to cite: Pellegrino, L., Natalicchio, M., Carnevale, G., Cavagna, S., Dela Pierre, F., Lozar, F., Nallino, E., Pastero, L., Varese, C., and Walter, J. D.: Minerals & microorganisms, a possible relationship: an awareness project of GEOMICROBIology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20419, https://doi.org/10.5194/egusphere-egu25-20419, 2025.

Polycyclic aromatic hydrocarbons (PAHs) are a group of toxic organic pollutants that originate from the incomplete combustion of organic matter. Due to lipophilic and hydrophobic properties, PAHs tend to be adsorbed by soil particles. Source apportionment of soil-bound PAHs contributes to controlling emissions and protecting the ecological environment. This research investigated source and distribution characteristics of PAHs in soils from Campania region of Italy, especially the natural sources. The total PAH concentrations ranged from N.D. to 4191 ng/g soil (dry weight). The data do not follow either a normal or lognormal distribution, but rather absolutely the multifractal distribution. Spatially distributed PAHs have experienced different degrees of superposition on the basis of multifractal spectrums curves with asymmetric upper convex. In addition, multifractal spectrum curves are all in a right hook shape, representing that low-values are dominant in the Campania area. The local singularity analysis shows an enrichment phenomenon that is not identified by the spatial interpolation method. The singularity values of PAHs were significantly correlated with TOC, but not significant with pH and population density. As opposed to concentrations, singularity indexes mainly reflecting the influence of soil properties. The fractal method was successfully used to separate the natural sources from the anthropogenic contributions of PAHs. Our results indicate that PAHs mixing distributions may be decomposed into natural background, anthropogenic background, and point source pollution. The background field was attributed to the thermal effects of geological processes, whereas anthropogenic anomaly was associated with anthropogenic activities. In sum, our study provides evidence of natural sources evidence that volcanic events have key effects on the distribution of PAHs, and shows that anthropogenic sources of PAHs are related to regional industrialization and urbanization status.

How to cite: Shi, C. and Qu, C.: Decoupling natural and anthropogenic polycyclic aromatic hydrocarbons in the soil environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2421, https://doi.org/10.5194/egusphere-egu25-2421, 2025.

The geochemical background/baseline is a key parameter for assessing environmental contamination and identifying potential risks to ecosystems and human health. However, the determination of these values requires careful handling of geochemical data. In practice, the geochemical background of chemical elements can be determined by both empirical and geostatistical methods. In addition, depending on the sampling scale and the area's natural landscape-geochemical characteristics, especially in biogeochemical provinces, the use of a single approach can lead to bias. Therefore, combining both approaches and incorporating several methods of geochemical data processing and spatial clustering is needed to unveil the hidden patterns and delineate representative areas, where separate processes and factors (natural and anthropogenic) condition the contents and distribution of chemical elements. In addition, adding auxiliary information related to the geological setting, soil types and potential sources of contamination can ensure the refinement of the data processing and increase the reliability of the estimated background/baseline values. This study aims to determine the geochemical background/baseline of arsenic (As) in the Lori region (Armenia) by dividing the soil data set into homogeneous subsamples using an algorithm combining data transformation, hot spot analysis (Local Moran I), univariate outlier detection and concept of normal distribution. The results of the study showed that the application of the Local Moran I index allows to identify clusters of samples (of high-high (HH) values, low-low (LL) values and not-significant (NS) values) that have a clear spatial separation. The boxplots of the As contents in the identified subsamples showed that outliers and extreme values are presented. After the elimination of these values, normal distribution was confirmed (Shapiro-Wilk test). The median value of As was 13 mg/kg, 16 mg/kg and 24 mg/kg for LL, NS and HH values, respectively. Meanwhile, the 95 percentile of the LL and NS values were 16 mg/kg and 21.4 mg/kg, respectively. The cluster of HH values spatially covers an area known for its natural mineralization, mining sites and Cu smelter, implying some level of anthropogenic quantities of As which is superimposed on the natural contents. Therefore, the estimated value for this area can be considered as a geochemical baseline rather than a geochemical background. The results of this study showed that in the case of biogeochemical provinces where natural mineralization and anthropogenic activities are presented, several background/baseline values can be determined. The algorithm proposed in this study can be used for other elements and serve as a justified approach to separate homogeneous subsamples and delineate areas for the application of these reference values.

How to cite: Tepanosyan, G., Poghosyan, Z., Gevorgyan, A., Davtyan, K., and Sahakyan, L.: Determination of geochemical background/baseline values in a biogeochemical province (a case study of the Lori region, Armenia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6105, https://doi.org/10.5194/egusphere-egu25-6105, 2025.

Many environmental and geological phenomena are inherently complex, shaped by the interplay of physical, chemical, biological, and anthropogenic factors. These interactions often result in spatial asymmetries, where high and low values exhibit distinct statistical behaviors. For instance, a contaminant field may simultaneously reflect natural and anthropogenic sources, producing unique spatial patterns that challenge conventional analysis.

Despite significant advancements in geostatistics, multivariate spatial models remain limited. The linear model of coregionalization (LCM) dominates the field but assumes symmetrical dependencies and Gaussian behavior. These assumptions restrict its ability to capture the structural complexity of multivariate spatial data, potentially obscuring meaningful relationships or introducing misleading correlations.

This presentation introduces a stochastic methodology for simulating non-Gaussian multivariate random fields using a non-linear model of coregionalization (N-LCM). The proposed approach accounts for rank asymmetry (differing spatial dependencies for low and high values) and directional asymmetry (variations in spatial dependence across directions). It supports multiple dependencies between variables, allowing some to exhibit Gaussian behavior while others display non-Gaussian characteristics. Pseudo-admissible N-LCMs are approximated through spectral decomposition, with negative eigenvalues replaced by zero.

The methodology leverages an adapted Generalized Fast Fourier Transform Moving Average (G-FFTMA) algorithm for multivariate non-Gaussian geostatistical simulations, offering a flexible and efficient framework for analyzing and simulating complex datasets. Synthetic examples demonstrate the method’s ability to uncover meaningful spatial patterns. Additionally, a real-world case study highlights the duality between natural contamination and anthropogenic emissions from a smelter in Quebec, Canada. This case study emphasizes the methodology’s capability to analyze geochemical processes influenced by human activities and environmental interactions.

This research advances geostatistics and multivariate analysis, providing new insights into geological and environmental processes at the Earth’s surface.

How to cite: Lauzon, D., Hörning, S., and Bárdossy, A.: A Novel Framework for Stochastic Simulation of Multivariate Non-Gaussian Random Fields in Environmental and Geological Studies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7198, https://doi.org/10.5194/egusphere-egu25-7198, 2025.

It has been revealed that significant disparities in both the organic matter source and hydrocarbon generation characteristics of lacustrine sedimentary environments, causing challenges in the assessment of continental shale oil prospects  . Lacustrine-sourced shale oil resources in China exhibits notable longitudinal and vertical heterogeneity, which poses a substantial challenge in objectively assessing geological resources and shale oil prospects, especially in a region characterized by overall low thermal evolution . Advanced pyrolysis or bulk kinetic experiments are invaluable tools to refine the understanding of petroleum generation timing . Nevertheless, such experiments are expensive and time-consuming and hence cannot be executed on extensive sets of samples to capture the overall lateral and vertical variability that a source formation may inherit  .In this study, we proposed a new method to rapidly evaluate the hydrocarbon generation characteristics of lacustrine source rocks utilizing anomalies in the Rock-Eval pyrolysis parameter Tmax across various lacustrine shales.

The workflow is depicted as flows: The analysis workflow starts with the selection of samples with TOC exceeding 1 wt.%, given the economic exploration potential of these shales. Subsequently, these samples are categorized into low and high maturity profiles based on the measured vitrinite reflectance (Ro). The two maturity profiles are further classified into low and high Tmax classes using machine learning data analysis. The kmeans clustering method in the Python library scikit-learn was utilized to classify different Tmax values to specific classes  . In certain instances, a third cluster or class may be necessary, depending on the data structure. Samples in the “low Tmax” class typically exhibit high Production Index (PI = S₁/(S₁+S₂)) while the Hydrogen Index (HI: = S₂/TOC*100) values decrease with increasing maturity. In contrast, the “high Tmax” class maintains consistently high HI and low PI at different maturity levels. This analysis workflow facilitates the identification of distinct hydrocarbon generation characteristics for source rocks at different maturity levels based on the Tmax values.

Overall, the “low Tmax” class shows characteristics of early hydrocarbon generation, low activation energy, and wide hydrocarbon generation windows, while the “high Tmax” class shows characteristics of late hydrocarbon generation, high activation energy, and narrow hydrocarbon generation windows. Notably, these diverse hydrocarbon generation characteristics are mainly related to the composition of the primary organic matter, a correlation that can be confirmed through organic petrographical observations.

This analysis workflow is validated with three examples. There are a great data pool of Tmax，and it is recommended to shift the focus towards source rocks that host organic matter favorable for early oil generation. This involves identifying rocks with low Tmax values and hence low activation energy, as they are indicative of conditions conducive to the initiation of oil generation. When it comes to in-situ heating, The exact prediction of hydrocarbon generation processes enables a more precise calculation of current geological recoverable resources. This study has important guiding significance for oil and gas exploration.

Fig. 1. Workflow for determining hydrocarbon generation characteristics of source rocks by a classification according to T_max variability.

How to cite: Liu, S., Liu, S., Misch, D., Shi, X., Bian, C., Zhao, W., and Zhu, R.: A new approach to evaluate hydrocarbon generation characteristics by pyrolysis Tmax in lacustrine shale oil plays, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7643, https://doi.org/10.5194/egusphere-egu25-7643, 2025.

The traditional kinetic model reflects the impact of fixed pressure on hydrocarbon generation in thermal simulation experiments, but the pressure in experiments differs from the overpressure in formation, affecting the evaluation of hydrocarbon generation. In this study, a new parallel first-order reaction kinetic model for hydrocarbon generation in relation to formation overpressure retardation is proposed and its application is illustrated.

According to the impact of pressure on activation energy (E) and pre-exponential factor (A), the pressure factor is introduced into the Arrhenius formula:

k=A·exp(p/a)·exp⁡(-(n⋅p+E)/RT)

Where k is the reaction rate at 1 bar, R is the universal gas constant, T is the absolute temperature (K), p is pressure (MPa), a and n are the impact factors of pressure on A and E respectively.

By calculating n and a, the new model can simulate hydrocarbon generation under any temperature and pressure and is no longer limited by experimental conditions.

Sample from Baiyun Depression in the Pearl River Mouth Basin were selected to carry out a gold-tube thermal simulation, and the kinetic parameters of natural gas generation were calculated by using the new model. Since the traditional model reflects the impact of experimental pressure, the new model calculates the kinetic parameters without the impact of pressure, therefore, the average activation energy (Ea) calculated by the traditional model is greater than that of the new model, and the impact of pressure is reflected by impact factors (n and a)(Fig. 1).

Figure 1 Comparison of kinetic parameters of natural gas generation calculated by traditional model and new model

The new model reflects the inhibition effect of overpressure on natural gas generation (Fig. 2). According to the information on fluid inclusions, The kerogen began to generate mass gas at 23 Ma. The calculation results of the traditional model show that kerogen starts to enter the large-scale gas generation stage at 32 Ma, which is inconsistent with the time of overpressure formation. When the formation pressure coefficient is 1.8, the mass hydrocarbon generation time calculated by the new model is about 24 Ma, which is more consistent with the geological reality. The new model proves that natural gas generation is retarded under the impact of overpressure.

Figure 2 Comparison of the conversion rate of natural gas of the traditional model and the model in relation to overpressure under geological conditions.The black line reflecting the influence of pressure under experimental conditions; the blue line is the history of natural gas generation without the impact of overpressure; the orange line is the history of hydrocarbon generation under formation overpressure.

How to cite: Jiang, J. and Li, J.: Overpressure retardation of hydrocarbon generation: a new kinetic model considering the effects of pressure and its application, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8179, https://doi.org/10.5194/egusphere-egu25-8179, 2025.

Qinghai Province, in northwest China's low-density population areas, is known for its high-altitude landscape and abundant surface water. This study investigates 48 sediment samples from 19 quintessential plateau lakes distributed in the Qilian Mountains, Qaidam Basin, Yellow River source regions, and Yangtze River source regions of Qinghai Province, focusing on 7 potentially toxic elements (PTEs ) and 16 priority polycyclic aromatic hydrocarbons (PAHs). Compared to other plateau lake sediments domestically and internationally, concentrations of PTEs ( Ni, Zn, Pb, Cu, Cr, Co, and As) and PAHs (Nap, Acy, Ace, Flu, Phe, Ant, Fla, Pyr, BaA, Chr, BbF, BkF, BaP, IcdP, DahA, and BghiP) in the studied sediment samples were relatively low. Spatial distribution characteristics of PTEs and PAHs contents show that the similar trend between the four regions was like that: Qaidam Basin> Yangtze River source>Yellow River source> Qilian Mountains. Additionally, positive matrix factorization (PMF) and species sensitivity distributions (SSD) are employed  to assess pollution source levels and ecological risks in the study lake regions,respectively.The study reveals that the total average concentrations of PTEs and PAHs in the sediments of the 19 Qinghai lakes were individually 132.93 mg/g and 27.64 ng/g,  which were quite low compared to lake sediments in other plateau regions both domestically and internationally. PMF analysis identified fisheries, animal husbandry, mining, rock weathering, and agriculture as PTE sources.While oil leakage, combustion, and auto emissions were identified as PAH sources. It is found that SSD-based health risk assessment shows the risks was far below the acceptable threshold (0.1). However, the highest risks were concentrated mainly in the downstream areas of the estuaries and near tourist and agricultural sites, such as the studied sites in Keluke Lake (Qaidam Basin), Eling Lake (Yellow River source region), and Tuosu Lake (Qaidam Basin). Notably, Cu, As, and Phe exhibited higher ecological risk indices. In general, despite the current research indicating low and negligible health risks posed by PTEs and PAHs in these plateau lakes, it is necessary to keep monitoring and controlling to prevent any escalation of ecological risks in the fragile lake environment.

How to cite: Sun, W., Zhang, J., Wang, W., and Qu, C.: Sources apportionment and ecological risk assessment of potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of plateau Lakes of Qinghai Province, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10689, https://doi.org/10.5194/egusphere-egu25-10689, 2025.

We investigate the intricate patterns associated with space-time dynamics displayed by (i) surface topography (Z) and (ii) reaction rates (R) resulting from direct nano-scale imaging of calcite-water interfaces subject to dissolution. The analysis rests on a space-time variogram modeling approach. The latter has been suggested as promising in unveiling major patterns exhibited by hydrogeological quantities across large scale aquifer systems. Transferability of the associated theoretical and operational framework to interpret nano-scale geochemical scenarios is here assessed for the first time. We do so upon taking advantage of recent high-resolution experiments attained through Atomic Force Microscopy (AFM) and targeting the evolution of the interface between a calcite crystal and water as driven by mineral dissolution processes. Upon relying on the ensuing large data-set, key variability patterns are identified through (i) efficient sampling of the spatial domain via quasi-random Sobol sequences and (ii) the use of a Harmonic Covariance Estimator (HCE) to model the space-time variogram of Z. The resulting (sample) space-time variogram exhibits visibly periodic oscillations at specific spatial and temporal lags. These patterns highlight the interaction taking place between the spatial structure and temporal dynamics in hydrogeological processes. We also explore the theoretical bases of the relationship between the variograms of Z and R. Corresponding results offer valuable insights into the spatial and temporal correlation of calcite dissolution dynamics. Our findings enable one to link space-time dynamics of crystal topography and the ensuing dissolution rates to corresponding traits of space-time variograms. Hence, they constitute the basis for potential applications associated with the possibility of providing estimates of the way these complex processes evolve at nano-scale resolutions, thus driving chemical weathering of minerals constituting the Earth’s interior.

How to cite: Varouchakis, E., Recalcati, C., Ceresa, L., Riva, M., and Guadagnini, A.: Geostastical modeling of space-time dynamics calcite dissolution at the nanoscale, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12283, https://doi.org/10.5194/egusphere-egu25-12283, 2025.

The Muyira sector is one of ten sectors of the Nyanza district in the Amayaga region of Rwanda. Amayaga region is part of the country's drought-prone areas, with high groundwater dependence. Most inhabitants in the area depend on groundwater for drinking and domestic purposes. Therefore, a hydrogeochemical characterization and assessment of groundwater quality in the study area was carried out using a combined application of hydrochemical models, multivariate statistical techniques, and GIS-based ordinary kriging interpolation on seven (7) borehole water samples. This study aimed to determine the concentrations and spatial distribution of various ions, groundwater quality issues, and the geochemical processes contributing to groundwater chemistry. The abundance of major cations in the groundwater is in the order Na⁺ > Ca²⁺ > K⁺ > Mg²⁺, whereas that of the major anions varies in the order HCO₃⁻ > SO₄²⁻ > Cl⁻. Ca-Mg-Na-HCO₃ water type is common in the area, possibly due to the dissolution of magnesite and silicate minerals in the basement rocks. Also, results indicate weak acids (i.e., HCO₃⁻) dominance over strong acids (i.e., SO₄²⁻ and Cl⁻). Ion exchange reactions and magnesite and silicate minerals weathering primarily control the area's groundwater chemistry. The results of the Pollution Index for Groundwater (0.29-0.55) and Groundwater Quality Index (29.14-53.68) indicate groundwater in the area is suitable for drinking. The sodium percentage (36.88–78.20%, mean of 57.83%), magnesium ratios (13.90–94.66, mean of 35.70), and sodium adsorption ratio (4.63–16.92, mean of 11.78) suggests that groundwater in the study area is suitable for irrigation purposes.

How to cite: Ngendahayo, E., Impuhwezayo, M., Nkurunziza, E., and Nsengiyumva, J. N.: Hydrogeochemical characterization and assessment of groundwater quality in Muyira Sector, Rwanda., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12634, https://doi.org/10.5194/egusphere-egu25-12634, 2025.

To investigate particulate material dynamics,  48 soil, river bottom sediment, and river suspended particulate matter (SPM) samples were collected using a stratified sampling method in the Koppány River Basin, Hungary. Samples were analyzed via inductively coupled plasma mass spectrometry for the concentration of 44 elements, encompassing heavy metals, "light" metals, and rare earth elements. Multivariate statistical methods, particularly hierarchical cluster analysis and principal component analysis (PCA) were applied to identify patterns and drivers of material distribution across the catchment.

The PCA results revealed distinct partitioning of particulate material sources and transport behaviors. The first principal component (PC1) distinguished SPM samples from soil and sediment samples, underscoring the contrasting geochemical signatures of material mobilized during different flow conditions. The second principal component (PC2) separated SPM samples collected during low flow conditions from those collected during high flow conditions, reflecting hydrological influences on particulate transport and source contributions. Notably, spatial differences between the upper and lower parts of the catchment were found to be less significant than the temporal dynamics driven by flow conditions.

These preliminary findings highlight the pivotal role of hydrology in governing the geochemical composition of suspended materials and provide insights into sediment dynamics in hilly river basins. The study demonstrates the utility of multivariate approaches in disentangling complex interactions between geological and hydrological processes in catchment systems.

How to cite: Kardos, M. K., Jolánkai, Z., and Clement, A.: Applying fingerprinting methods on multielement measurements to track sediment transport in a small erosion-prone hilly catchment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12894, https://doi.org/10.5194/egusphere-egu25-12894, 2025.

Environmental risks are often linked to contamination processes driven by various chemical stressors introduced into the environment from specific sources. These sources may be anthropogenic, stemming from human activities, or natural, associated with the geolithological context and geological weathering processes. It is crucial to distinguish between chemical anomalies resulting from anthropogenic inputs and those arising from the inherent compositional characteristics of the natural environment, which may not be remediable. This differentiation is essential for establishing reliable and practical remediation objectives.

When anthropogenic activities release waste products into the environment in airborne, liquid, or solid forms, these materials typically possess distinct chemical compositions. Such compositions frequently involve associations of substances that can disrupt environmental equilibria. This study employed both univariate and multivariate statistical techniques to analyze geochemical data from over 7,000 topsoil samples collected in the Campania region of Southern Italy. The objective was to develop an operational model for assessing environmental risks by identifying their sources. The database encompasses the concentrations of 52 chemical elements for each sample, with data georeferenced to facilitate spatial analysis, delineate geochemical patterns, and correlate anomalies with known human or natural sources.

The complex geological setting of the Campania region, combined with the diverse sources of anthropogenic contamination, rendered Principal Component Analysis (PCA) an especially effective method for identifying element associations that predominantly influence the variability of the geochemical data. PCA was conducted using a selection of 21 variables, resulting in the identification of four significant principal components (PCs) that account for the majority of the observed data variability:

- PC1 (42% of total variance), characterized by Th, Be, As, U, V, and Bi.

- PC2 (16% of total variance), characterized by Sb, Zn, Hg, Pb, Sn, and Cd.

- PC3 (10% of total variance), characterized by Mn, Ni, Cr, and Co.

- PC4 (9% of total variance), characterized by Ba, Cu, and Sr.

The scores of the components for each sample were spatially plotted and classified to enhance their interpretability. The legend for the component scores was centered at zero, indicating the minimal contribution of the covered areas to overall component variability; higher absolute values identified areas where the featured elemental association was more significant.

The analysis effectively differentiated soils predominantly influenced by natural contributions, such as loose materials from the volcanic centers of Campania (e.g., Mt. Roccamonfina, Campi Flegrei, and Mt. Somma-Vesuvius) (PC1 and PC4) and weathering products from the region's siliciclastic deposits (PC3). Furthermore, the PCA found areas subjected to considerable anthropogenic pressure concerning the association of Sb, Zn, Hg, Pb, Sn, and Cd (PC2). These findings underscore the effectiveness of multivariate analysis, particularly PCA, in discriminating between geogenic and anthropogenic processes and, further, in distinguishing among various anthropogenic sources. This methodological approach offers valuable insights for managing environmental risks and prioritizing remediation efforts.

How to cite: Iannone, A., Zhang, C., Guarino, A., De Falco, A., Pacifico, L. R., and Albanese, S.: The application of Principal Component Analysis to reveal the contributions of various natural and anthropogenic sources to the chemical composition of soil., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16437, https://doi.org/10.5194/egusphere-egu25-16437, 2025.

Soils result from physical, chemical, and biological processes that affect rocks and their weathered products. In historical times, natural processes have also been widely influenced by human activity (such as industrial production, motor vehicle mobility, waste disposal, and agricultural practices). Consequently, soils represent a reservoir of chemical elements and compounds with extreme spatial variability across Earth's surface.

Defining the distribution of chemical elements and their anomalies and understanding the nature of factors controlling their spatial variability is essential for those committed to environmental issues management, especially when effects on ecosystems and living beings must be addressed, targeting the development of remedial actions.

In recent years, with the rapid data volume growth, effective methods are required for data analytics for large geochemical datasets. Spatial machine learning technologies have been proven to have the potential to reveal hidden patterns based on geochemical information. In this study, a spatial clustering technique of Getis-Ord Gi* statistic was performed on 21 characterizing elements using more than 7000 topsoil samples (~ 7300) proceeding from the Campania region territory in southern Italy.

The analysis found spatial clusters of significantly high (hot spots) and low values (cold spots) for the selected elements, showing a strong correlation with the geological features of the study area, particularly volcanic and siliciclastic units.

Volcanic units were associated with high concentrations of elements such as As, Ba, Be, Bi, Cu, Sr, Th, Tl, U, and V, while siliciclastic units were associated with high values of Co, Cr, Ni, and Mn. Additionally, the high concentration of Cd, Hg, Pb, Sb, Sn and Zn showed a clear association with the region's main urban and industrial centres.

The results highlight the power of spatial clustering techniques in discriminating geogenic from anthropogenic processes and identifying hidden spatial patterns, thus offering valuable insights for environmental studies and management.

How to cite: Albanese, S., Iannone, A., Zhang, C., Guarino, A., De Falco, A., and Pacifico, L. R.: Hotspot analysis for discriminating geochemical anomalies in the soil of an intensely anthropized volcanic region in Italy., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17328, https://doi.org/10.5194/egusphere-egu25-17328, 2025.

The interaction between the unique geochemical characteristics of the soils and the social, environmental, climatic and biodiversity factors give distinctive properties to the wines of a specific area, defining the terroir of a wine. While climatic, ecological, and social aspects remain relatively stable within the limited extension of terroirs, soil geochemistry can change notably. Variations in soil geochemistry play a significant role as they influence vine health, grape quality and, ultimately, the flavour profile of the wine. This study aims to highlight the chemical and granulometric differences occurring in the Taurasi terroir (Southern Italy) to improve its management and enhance the diverse flavours and aromas of the wines. The Taurasi terroir encompasses an area of 245 km², within which soils belong to three different geochemical domains (clay, volcanic, and carbonate soils). Chemical elements affecting colour and aroma (Cu, Fe), taste (Na, K), metabolism and photosynthesis (B, Mn, Zn), or potentially toxic elements for vines (Al, As) were analysed in 100 topsoil samples distributed across the three geochemical domains. Additionally, granulometry and organic carbon content were also analysed to assess soil's ability to retain water and microbial populations. Results revealed significant compositional differences among the three geochemical domains that inevitably reflect in wine characteristics. Except for Mn, volcanic soils were enriched in all analysed elements, while carbonate soils were depleted. Following the order of volcanic soils – clay soils – carbonate soils, the average concentrations of analysed elements were as follows: As (16 - 7 - 3 mg/kg); Al (5.5 - 3.2 - 1.8 %); B (24 - 10 - 6 mg/kg); Cu (78 - 52 - 28 mg/kg); Fe (3.2 - 2.7 - 1.8 %); K (1.6 - 0.7 - 0.4 %); Mn (950 - 1470 - 820); Na (0.6 - 0.05 - 0.05 %); Zn (105 - 62 – 58 mg/kg). From a granulometric perspective, volcanic soils were coarse-grained, followed by carbonate and clay soils. The average granulometry for the three geochemical domains is as follows: volcanic soils (72% sand, 13% silt, 5% clay); carbonate soils (26% sand, 58% silt, 16% clay); clay soils (5% sand, 13% silt, 72% clay). Average organic carbon values were also favourable for volcanic soils (4.5%), followed by carbonate soils (3.2%) and clay soils (1.4%). These results show that significant compositional and granulometric differences within the Taurasi terroir are reflected in the expression of grapes and wines produced. Therefore, this study provides key tools for micro-zoning terroirs to enhance diverse flavour, colour, and aroma expressions within the same terroir.

How to cite: Cicchella, D., Ambrosino, M., Guagliardi, I., and Albanese, S.: Harnessing soil geochemistry and granulometry for optimal terroir management and wine profiling: insights from the Taurasi terroir of southern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17982, https://doi.org/10.5194/egusphere-egu25-17982, 2025.

The hyperaccumulation behaviour of PTEs is observed in many edible plants. However, the role of soil geochemistry and the human health risks associated with the uptake of PTEs by hyperaccumulator plants remain poorly understood. This study analyses 10 topsoil and Brassica rapa samples collected from volcanic and clay soils, comparing the contents of As, Cd, Hg and Pb and assessing their relative health risks. To account for geochemical variations in volcanic and clay soils, samples were collected from two Italian regions (Sicily and Campania) characterized by different geological settings. The results indicate that volcanic soils exhibit higher concentrations of PTEs than clay soils, with Hg levels exceeding precautionary limits established by EU soil quality standards. Notably, Campania shows the highest concentrations of PTEs in soils, attributable to evolved magmatic products with tephritic-phonolitic composition. In clay soils, Sicilian samples reveal significant enrichment in Cd, while As, Hg and Pb are more concentrated in Campanian clays. Soil quality standards are not exceeded in clay soils. Regarding plant tissues, concentrations of Cd, Hg and Pb in edible organs (stems and leaves) exceed FAO-WHO standards in most samples from volcanic soils, with values up to 3, 8, and 14 times higher than the standards. Plants grown in clay soils show lower concentrations of PTEs than those grown in volcanic soils; only one Sicilian sample exhibits concentrations of Cd, Hg, and Pb 4, 1.5, and 6 times above FAO-WHO standards, respectively. The bioconcentration factor (BCF) and translocation factor (TF) confirm the hyperaccumulating behaviour of Brassica rapa, with concentrations of PTEs in roots and stems sometimes exceeding those present in the soil. Risk analysis revealed that total cancer risk and target hazard quotient are unacceptable for adults and children who consume Brassica rapa from volcanic soils. Both parameters generally show acceptable values in clay soils, with alarming levels only for high consumption rates. Finally, although Sicilian soils are generally impoverished in PTEs, Brassica rapa samples from this region exhibit higher levels than those from Campania. Therefore, while soil geochemistry is a crucial factor in metal absorption by Brassica rapa, other parameters (e.g., climatic, environmental, and biological) also play a significant role.

How to cite: Ambrosino, M., Puglia, G. D., Di Salvo, E. M., Saini, S., Cicero, N., and Cicchella, D.: The role of soil geochemistry in the absorption of potentially toxic elements (PTEs) by edible hyperaccumulator plants: the case of Brassica rapa in volcanic and clay soils., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18176, https://doi.org/10.5194/egusphere-egu25-18176, 2025.

The Sarno River Basin (SRB) is among the most polluted in Europe, with contamination deriving from industrial activities, including tanneries and canneries, as well as intensive agriculture and dense urbanization. It is located in the Campania region in Southern Italy, in the southwestern portion of the Campania Plain, between the Somma–Vesuvius volcanic complex to the west and the Lattari Mountains carbonate reliefs to the south.

The SRB is characterized by the presence of high concentrations of some priority organic pollutants, deriving from their use in various processes linked to human activities (e.g., agriculture, industry, mining, vehicular traffic). The soils of the basin, predominantly fine-grained alluvial and volcanic deposits, provide an ideal matrix for the retention of these pollutants, further enhanced by the high organic matter content.

Organochlorine pesticides (OCPs) are synthetic organic compounds extensively utilized in agriculture as insecticides and fungicides during the mid-20th century and, subordinately, in the medical field. These chemicals are among the most common soil contaminants, especially in highly industrialized and anthropized areas; they show a high environmental persistence and are generally characterized by a marked tendency towards bioaccumulation and biomagnification along trophic chains due to their lipophilic character.

The study aims to assess the geochemical-environmental conditions of the SRB, through GIS-based maps and univariate statistical analysis, also establishing the nature of their potential emission sources. For the purpose, over an area of about 500 km² a total of 42 topsoil samples were collected to be analyzed to determine the concentration levels of 24 OCPs.

To investigate the distribution pattern of concentrations, the compounds were grouped into six classes:

• I) dichloro-diphenyl-trichloroethane (DDT) and its isomers and metabolites (DDE, DDD), whose Ʃ₆DDTs concentrations represent on average 68.7% of the total OCPs and ranges from a minimum of 0.021 µg/kg to a maximum of 339 µg/kg;
• II) hexachlorocyclohexane (HCH) isomers (α, β, γ, δ), with Ʃ₄HCHs representing 2.64% and ranging from 0.013 µg/kg to 7.84 µg/kg;
• III) aldrin, dieldrin, and endrin, whose Ʃ₃Drins varies from 0.010 µg/kg to 71.7 µg/kg and constitutes the 6.61%;
• IV) heptachlor, chlordane (α, γ), and nonachlor (cis, trans), constituting on average 1.39% with Ʃ₅Chlors from 0.016 µg/kg to 0.94 µg/kg;
• V) Endosulfan (α, β), and Endosulfan sulfate, whose Ʃ₃Endos varies from 0.010 µg/kg to 19.3 µg/kg and represents 14.5%;
• VI) mirex, methoxychlor and hexachlorobenzene, constituting 6.18%, with total values from 0.010 µg/kg to 7.01 µg/kg.

Because some OCPs tend to degrade over time and the technical pesticides (i.e., DDT, HCH, chlordane, endosulfan) consist of precise percentage of the different molecules, the ratio between the parent compound and its metabolites can be used as pollution sources indicators. This helps identify whether the concentrations are attributable to fresh or historical use of these substances. The analyzed isomeric ratios showed that, although most OCPs are banned, recent applications of pesticide mixtures still contribute to high soil concentrations in some parts of the study area.

How to cite: Guarino, A., Iannone, A., De Falco, A., and Albanese, S.: Environmental Distribution and Source Analysis of Organochlorine Pesticides in the Soils of the Sarno River Basin, Southern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18593, https://doi.org/10.5194/egusphere-egu25-18593, 2025.

       The 21st century is the era of big data, where scientific research under the new paradigm of data and model-driven knowledge discovery has become the new trend in the scientific field. Under the framework of the international  science project "Deep-time Digital Earth" (DDE), the research team led by Dr. Wang Tao has constructed the OnePetrology database for magmatic rocks. This database adopts a three-in-one approach of "data + mapping + research," based on the magmatic rock knowledge system, with samples as the core,  with self-developed tools to build a magmatic rock database system that integrates big data aggregation and mapping analysis functions.

      The OnePetrology database system includes backend services (cloud), a website (Web), and a scientific research work platform (desktop). The data mainly comes from publicly published literature, tests conducted by the research team, laboratory test data, etc. The data types include basic information on magmatic rock rock types, occurrences, spatial locations, as well as geochronology, geochemistry, (Sr-Nd-Hf-Pb-O) isotopes, and non-traditional (or emerging) isotope data, involving global important orogenic belts, cratons, and some oceans (ocean drilling data).

    The database has preliminarily completed the framework construction and has incorporated a portion of the data, initially forming methods and processes for data aggregation. Currently, there are two ways to contribute data: first, volunteers enter data in the data "data submission portal" set up for this purpose.  The database system has currently built 22 thematic databases and welcomes more disciplinary experts to come to the magmatic rock database to build their own thematic databases.

      The core idea of the database's functionality is to combine big data and software tools for scientific research and exploration. Taking the website as an example, it provides data filtering tools and mapping analysis tools. Data filtering tools include spatial filtering and attribute filtering: spatial filtering can pull cross-sections (set radius), rectangles, custom polygons, global tectonic units, global cratons, China and neighboring areas' main tectonic units, and other search methods, while attribute filtering can set search conditions, value ranges, and fuzzy queries for all fields. Spatial filtering and attribute queries can be used separately or in combination, with query results displayed in table form, spatial distribution maps, and mapping functions. The mapping functions currently built in the database include TAS, Pearce, SiO2-K2O, ACNK-CNK, 2D Density, Heatmap, Profile, etc., each supporting secondary filtering and grouping, facilitating users to quickly discover data patterns.  Currently, online analysis can provide processing capabilities for about 20,000 samples (assuming average desktop computing capabilities). If you need to process larger data volumes, please download the desktop software from the homepage of the website (https://dde.igeodata.org).

     In summary, the DDE OnePetrology magmatic rock database has preliminarily constructed the capabilities for magmatic rock data aggregation and mapping analysis, with other planned functions being built step by step. We warmly welcome more interested experts to participate in the construction and use of the magmatic rock database and to offer your valuable suggestions.

How to cite: Ding, Y., Wang, T., Tong, Y., and wang, C.: An easy way to build database and analyze data using OnePeterology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20237, https://doi.org/10.5194/egusphere-egu25-20237, 2025.

Statistical models are a frequently used tool in hydrology, especially when it comes to estimating design floods, i.e. flood events that used to design flood protection systems or reservoirs. The often complex hydrological data, which are affected by e.g. missing values, extremes or time-varying processes, require sophisticated statistical models that take these challenges into account. As a scientist, developing such models can be a lot of fun and provide interesting insights. After months of thinking about the best model under certain statistical assumptions, proving asymptotic theorems and testing the model with synthetic data, you are happy and proud to have developed a new model. This model will hopefully be widely used in future research. The next step is to apply the model to a large real data set. The results look good on average. The results will be shared with practitioners, because of course you want the model to be useful for science and practice. And then: the phone call. You are told that your results are not plausible for a certain catchment area. And in general, the new model is not needed in practice because there is an established model. This example describes such a case and discusses ways of dealing with it. It is intended to illustrate the importance of communication between science and practice and a general understanding between both sides.

How to cite: Fischer, S.: When practical considerations impact your scientific model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1620, https://doi.org/10.5194/egusphere-egu25-1620, 2025.

In the early 1990's, fractals and chaos were hot. In 1987, James Gleick had published "Chaos: Making a New Science", popularizing non-linear dynamics. Hydrologists played an important role in the development of fractal theory. Hurst had discovered that sequences of dry and wet years for the Nile showed very long memory effects. Instead of the chance of a dry year following a dry year being 50%, Hurst found that there were surprisingly many long series of dry or wet years. Seven fat years, seven lean years, as it is noted in Genesis. Scott Tyler found fractals in soils ("Fractal processes in soil water retention"). At Cornell, where we were at the time, David Turcotte described "Fractals in geology and geophysics". A few years later, Ignacio Rodríguez-Iturbe and Andrea Rinaldo would publish "Fractal River Basins: Chance and Self-Organization". In short, fractals were exciting scientific gold.

A fractal is not just an obscure mathematical object but something that can actually be found everywhere in nature. Early on, a paper was published in Nature with the title "Fractal viscous fingering in clay slurries" by Van Damme, Obrecht, Levitz, Gatineau, and Laroche. They "only" did an experiment on a fractal embedded in 2D; we should be able to do one better and find the fractal dimension of the surface of cracking clay embedded in 3D. So out we went, collected some clay, mixed it with water in a cement mixer, siliconed together a shallow "aquarium", and poured in the slurry. To observe the cracking of the drying slurry, a video camera was mounted above the experiment, looking down and taking time-lapse images. To access the views from the sides, mirrors were installed at 45 degrees at each of the four sides. Lights made sure the camera captured high quality images. The whole set-up was enclosed in a frame with dark cloth to ensure that lighting was always the same.  We already had some box-counting code ready to calculate the fractal dimension of the surface, called the Minkowski–Bouligand dimension. One variable needed some extra attention, namely the boundary between the clay slurry and the glass sides. If the clay would cling to the sides, it would be difficult to understand the effects that this boundary condition had on the outcome of the experiment. Moreover, the cracks may not have become visible in the mirrors when the sides were covered with mud. So, instead, it was decided to make the sides hydrophobic with some mineral oil. This ensured that when the clay would start to shrink, it would come loose from the sides. Now, all we had to do was wait. It took only a week or so before the consolidated slurry started to shrink and to come loose from the sides. After that, the clay continued shrink for many weeks. This is how we learned that the fractal dimension of a shrinking brick of clay is (very close) to 3.0. 

How to cite: van de Giesen, N. and Selker, J.: The Minkowski–Bouligand dimension of a clay brick, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1660, https://doi.org/10.5194/egusphere-egu25-1660, 2025.

In 2018, we found exciting new results in landform evolution modeling by coupling the two simplest models of fluvial erosion and hillslope processes. While the stream-power incision model is the simplest model for detachment-limited fluvial erosion, the diffusion equation is the simplest description of hillslope processes at long timescales. Both processes were added at each grid cell without an explicit separation between channels and hillslopes because fluvial erosion automatically becomes dominant at large catchment sizes and negligible at small catchment sizes.

We found that increasing diffusion reduces the relief at small scales (individual hillslopes), but even increases the large-scale relief (entire catchments). As an immediate effect, the hillslopes become less steep. In turn, however, we observed that the network of the clearly incised valleys, which indicates dominance of fluvial erosion over diffusion, became smaller. So a smaller set of fluvially dominated grid cells had to erode the material entering from the hillslopes. To maintain a morphological equilibrium with a given uplift rate, the rivers had to steepen over long time. This steepening even overcompensated the immediate decrease in relief of the hillslopes.

This result was counterintuitive at first, but we were happy to find a reasonable explanation. So we even prepared a short manuscript for a prestigious  journal. We just did not submit it because we wanted to explain the effect quantitatively from the physical parameters of the model. From these theoretical considerations, we found that our numerical results did not only depend on the model parameters, but also on the spatial resolution of the model and noticed that this scaling problem was already discussed in a few published studies. Beyond the scaling problem, we also realized that applying the concept of detachment-limited fluvial erosion to the sediment brought from the hillslopes into the rivers is quite unrealistic. A later study including fluvial sediment transport and a model for hillslope processes that avoids scaling problems did not predict any increase in large-scale relief. So we finally realized that our original findings were mainly the result of a specific combination of models that should not be coupled this way and are not  as relevant for landform evolution as we thought.

This example illustrates many of the pitfalls of numerical modeling beyond purely technical issues. In particular, combining models that are widely used and make sense individually may still cause unexpected problems.

How to cite: Hergarten, S. and Robl, J.: Landslides and hillslope erosion increase relief, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5035, https://doi.org/10.5194/egusphere-egu25-5035, 2025.

In this presentation, I will discuss my research into the simple climate model Hector, which calculates temperature change based on the impact of various climate scenarios. More specifically, I will discuss how an artistic-led approach through (un)voluntary-caused computational bugs can help document the model's logic and socio-political implications. I will describe methods for collective 'debugging' to produce transdisciplinary knowledge (beyond solely scientific inquiry) to foster conversation about the potential and limits of current climate infrastructure to foster concrete climate actions. This research investigates the field of climate science through artistic practice, software and infrastructure studies, and participatory methods. To expand on the role of bugs in my investigation, I will elaborate on concrete examples of differences in perception of 'error' in the fields of arts and science, looking at case studies where mistakes or glitches have been valorised and mobilised through artistic practice to grapple with, appropriate, and/or repurpose scientific instruments.

How to cite: Legrand, G.: (Re)(De)bugging tragedies with Hector, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5091, https://doi.org/10.5194/egusphere-egu25-5091, 2025.

"Doesn't this look a bit strange?" 

It began with an innocent question during one of our Master's colloquia. And it could have ended there. "We were just following an approach from the literature". And who could argue against following the literature?

But it bugged me. During a long train ride, I began to think about the issue again. 10 hours and many papers later, I was only more confused: was it really that obvious, and why had no one picked up on it before? But sometimes the most obvious things are the most wicked, and after a few conversations with knowledgeable colleagues, I was sure we were in for an unexpected surprise. 

A commonly used approach to defining heat extremes is as exceedances of percentile-based thresholds that follow the seasonal cycle. Such relative extremes are then expected to be evenly distributed throughout the year. For example, over the 30-year period 1961-1990, we expect three (or 10%) of January 1s to exceed a 90th percentile threshold defined for the same period - and the same for all other days of the year. In a recent study, we show that there are many cases where this does not hold, not even close (Brunner and Voigt 2024).

Here, we tell the story of how this blunder spread in the literature out of the desire to improve extreme thresholds. We show that seemingly innocent changes can sometimes have unintended consequences and that taking the time to check the obvious can help avoid mistakes in science. 

Brunner L. and Voigt A. (2024): Pitfalls in diagnosing temperature extremes, Nature Communications, https://doi.org/10.1038/s41467-024-46349-x

How to cite: Brunner, L., Meindl, M., and Voigt, A.: Improving extreme temperature definitions until they are wrong, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5951, https://doi.org/10.5194/egusphere-egu25-5951, 2025.

When economists estimate the expected economic damages from current-day CO₂ emissions, they usually calculate the social cost of carbon – that is, the aggregated damage caused by the emission of an additional ton of CO₂. Several cost-benefit integrated assessment models (IAMs) are built to assess this quantity, and among them is the META model. This model is built specifically to assess the effects of tipping points on the social cost of carbon, and it usually operates stochastically. When integrating a deterministic, but small carbon cycle tipping point into the model, however, the social cost of carbon seems to explode: a few gigatons of additional emissions almost double the impact estimates of CO₂ emissions! Well, maybe. In fact, these results are a pure artifact of two things: 1) the way in which social cost of carbon estimates are calculated with IAMs; and 2) the way that tipping points are implemented in the META model. And, of course, 3): a lack of initial thoughtfulness on behalf of myself. A thorough look into this issue shows that, as expected, a marginal change in emissions leads to a marginal change in damage estimates. While that result is rather boring, the previous blunder can actually be instructive about the scarcely-known methods used to obtain economic impact estimates of climate change.

How to cite: Schaumann, F.: Drastic increase in economic damages caused by a marginal increase in CO2 emissions?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9145, https://doi.org/10.5194/egusphere-egu25-9145, 2025.

Historically, large areas across the globe have been affected by deforestation or irrigation expansion. The replacement of forests with agricultural land and increased water availability in irrigated croplands altered the land’s surface properties, leading to influences of biogeophysical changes on near-surface temperature. From limited observations and mostly idealized simulations, we know that sufficiently large alterations of land surface properties can theoretically lead to systematic temperature and precipitation changes outside and even far from the altered areas. Not only the advection of temperature anomalies, but also changes in circulation and ocean feedbacks have been shown to be potential drivers of such non-local responses in single and multi-model studies.

We tested the robustness of non-local temperature signals to internal variability in the fully coupled Community Earth System Model 2 (CESM2) simulations of the historical period (1850 – 2014) with all forcings vs. all-but-land-use-change forcings. Doing so, we first found seemingly robust non-local temperature effects of land use change on the global and regional scale. But when accounting for the sampling of internal variability in the model using a large initial condition ensemble, the global scale signal was found to be indistinguishable from noise. Only regionally in some hotspots, we found robust and historically important non-local temperature signals. Through increasingly rigorous analysis, we reached a partly negative and unexpected but important finding, which may have implications for future assessments of comparably weak or spatially heterogeneous forcings to the Earth system.

How to cite: Jäger, F., Sieber, P., Simpson, I., Lawrence, D., Lawrence, P., and Seneviratne, S. I.: How robust are modeled non-local temperature effects of historical land use changes really?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10285, https://doi.org/10.5194/egusphere-egu25-10285, 2025.

Failures are only common in science, and hydrological modelling is no exception. However, we modellers usually do not like to talk about our mistakes or our overly optimistic expectations and, thus, “negative” results usually do not get published. While there are examples where model failures indicated issues with the observational data, in this presentation the focus is on modelling studies, where some more (realistic) thinking could have helped to avoid disappointments. Examples include the unnecessary comparison of numerically identical model variants, naively optimistic expectations about increasing the physical basis of bucket-type models and excessively hopeful assumptions about the value of data.

How to cite: Seibert, J., Clerc-Schwarzenbach, F., van Meerveld, I., and Vis, M.: Think twice – pitfalls in hydrological modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10615, https://doi.org/10.5194/egusphere-egu25-10615, 2025.

The idea of invisible ship tracks for the study of aerosol-cloud interactions sounds promising: We have been studying the effects of aerosols on clouds for many years, among others by investigating the bright lines of clouds left in low marine clouds by ships. However, only a small fraction of ships leaves behind visible tracks. This means we can only study aerosol-cloud interactions under certain meteorological conditions, biasing our understanding. Instead, by studying all clouds polluted by ships ('invisible ship tracks') with a methodology we developed, we should be able to get a full picture of aerosol-cloud interactions. A number of interesting and impactful results have come out of this research, along with several setbacks and corrections to initial results. Here, we examine them in order, showing how correcting for one identified bias can introduce two new ones. Unexpected glitches arise from sources as varied as: choices regarding ship track definition, retrieval geometry, specific weather systems biasing results, and mathematical subtleties. What can we conclude after four years of progress on this methodology? While some results still stand, others had to be significantly corrected. This makes us see invisible ship tracks as an example of research that is closer to a method of 'tinkering' than to a 'magnificent discovery'.

How to cite: Manshausen, P., Tippett, A., Gryspeerdt, E., and Stier, P.: Two steps forward, one step back: four years of progress and setbacks on invisible ship tracks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11357, https://doi.org/10.5194/egusphere-egu25-11357, 2025.

Earth system models are important tools used to understand our climate system and project possible changes in our climate due to anthropogenic and natural forcings. Human errors can occur in the development of Earth System models, i.e., bugs, giving an unphysical representation of our climate. A way to identify and solve bugs is to apply physical concepts. Here, we present an experience that occurred in the development of the ICOsahedral Non-hydrostatic model (ICON) as a kilometer-scale Earth System model, in which physically understanding a bug in the surface energy budget fixed land precipitation. 

In a simulation of ICON, referred to as ICON-bug, precipitation over tropical land continuously decreased across the simulation. This led to a ratio of land-ocean precipitation in the tropics of less than 0.7, which, otherwise, should be more than 0.86. As part of the possible explanations, the surface energy budget over land was targeted as a culprit. This idea relies on the influence of the interaction between soil moisture, surface heat fluxes, and winds to generate circulation favoring precipitation over dry land surfaces (Hohenegger and Stevens 2018). Indeed, the surface energy budget over dry surfaces in the ICON-bug showed an error in sensible heat flux. The sensible heat flux transmitted to the atmosphere was 70% of what was calculated for the surface module. Fixing this error closed the surface energy budget and increased land precipitation over the tropics, leading to a ratio of land-ocean precipitation of 0.94, close to observations. 

How to cite: Segura, H., Hohenegger, C., Schnur, R., and Stevens, B.: Physical understanding of bugs to improve the representation of the climate system  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12720, https://doi.org/10.5194/egusphere-egu25-12720, 2025.

Whenever you study a phenomenon of mm to a few cm-scale in the laboratory which involves an interface, the question of surface tension arises. Surface tension is due to the fact that molecules prefer to stay with their own kind. Therefore, the creation of an interface between two fluids requires energy, and this influences the dynamics around the interface.

Surface tension can be a blessing: it produces the round shape of rain drops or the nice bubble shapes of colorful liquid in a lava lamp. It allows objects with a higher density to float on a liquid (such as an insect on water, or a silicone plate on sugar syrup). It can generate flow up a capillary.

However, it can also be a curse in the case of thermal convection. Purely thermal convection  develops when a plane layer of fluid is heated from below and cooled from above. The engine of motion is the thermal buoyancy of the fluid. This is what is happening in a planetary mantle on scales of hundreds to thousands kilometers. This is also what is happening in a closed box in the laboratory. But as soon as an interface exists, either between an upper and a lower experimental mantle, or in the case of a free surface at the top of the fluid layer, surface tension effects can become important. For exemple, the variation of surface tension with temperature was responsible for the beautiful honey-comb patterns imaged by Benard (1901) in the first systematic study of thermal convection with a free-surface. Surface tension is also going to act against the initiation of subduction (which acts to break the surface). 

We shall review in this presentation the signatures of surface tension in a convective context, and the different ways to minimize and/or remove the effects of surface tension in convection experiments, such as using miscible liquids, or a layer of experimental « sticky air ».

How to cite: Davaille, A.: Analog studies of mantle convection: the curse of surface tension (or not) ?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15059, https://doi.org/10.5194/egusphere-egu25-15059, 2025.

In hydrology we measure and follow the water. What if there is too much or too little? It happens a lot. As a field hydrologist, I frequently have to determine the location of a measurement, the time to take the measurement, the location to set up a field experiment, or the amount of a tracer to inject to study a hydrological system. However, this is a very bumpy road, as variability is often not in favor of my decisions because the distribution is wider than expected, bimodal instead of unimodal, or the probability of an event is theoretically small, but still an extreme event occurs during our experiment. I will showcase some examples to demonstrate what I mean and what I experienced, as well as how frequently the PhD students or Postdocs have suffered as a result of my decisions or of the unexpected variability: Climatic variability resulted in a winter without snow, just as new sensors were already deployed. Or the winter snowpack was extremely high, preventing any work at high altitudes in the Alps until mid of July, thereby reducing our field season by half. An ecohydological study to observe the effects of drought in a forest with a rainout shelter was ineffective because it occurred during an extremely dry year, making the control just as dry as our drought treatment. The automatic water sampler was set-up to collect stream water samples, but it was washed away four weeks later by the 50-year flood. The calculated amount of artificial tracer was either way too low, because the transit times of the system were much longer than expected, or it was far too high, resulting in colored streams or samples that had to be diluted by a factor of 100 due to much faster transit times Finally, and most expensively, we installed many trenches along forest roads to measure subsurface stormflow but after three years, we abandoned the measurements because we never measured a drop of water coming out of the trenches, as the bedrock permeability was much higher due to many high permeable fissures that prevented the formation of subsurface stormflow.  These experiments or observations failed because of unexpected variability in input, system properties or a lack of technical variability in the equipment. I will reflect on residual risk of failure in fieldwork related to that crux and discus approaches to reduce this risk.

How to cite: Weiler, M.: The crux with variability: too much or too little, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15457, https://doi.org/10.5194/egusphere-egu25-15457, 2025.

The emergence of global km-scale climate models allows us to study Earth's climate and its changes with unprecedented local detail. However, this step change in spatial resolution to grid spacings of 10 km or less also brings new challenges to the numerical methods used in the models, the storage of model output, and the processing of the output data into actionable climate information. The latest versions of the ICON-Sapphire model developed in the frame of the NextGEMS project address these challenges by running on an icosahedral grid while outputting data on the so-called HEALPix grid. Both grids are unstructured grids, which avoids, for example, the issue of longitude convergence. In addition, HEALPix allows data to be stored in a hierarchy of resolutions at different discrete zoom levels, making it easier for users to handle the data.  

The transition from the native 10 km grid to the output grid is made by a simple but very fast nearest-neighbour remapping. An advantage of this simple remapping approach is that the output fields are not distorted, i.e. the atmospheric states in the output remain self-consistent. As HEALPix only provides discrete zoom levels in the setup of the run, it was decided to remap to the closest available resolution of 12 km rather than to the next finer resolution of 6 km. This decision was made to avoid artificially increasing the number of grid points and to avoid creating duplicates through the nearest neighbour remapping.

As a consequence of this approach, wave-like patterns can emerge due to the Moiré effect that can result from the interaction of two grids. We find these patterns when looking at certain derived precipitation extremes, such as the annual maximum daily precipitation, the 10-year return level of hourly precipitation, or the frequency of dry days. At first, we interpreted these patterns as a plotting issue, as the figures might have too low resolution to cope with the high-resolution global plot (aliasing) leading to a Moiré pattern.

However, zooming in on the affected regions and closer examination of the data revealed that the pattern is in fact in the data. Further investigation with synthetic data confirmed the suspicion that the Moiré pattern was indeed caused by the remapping of the native 10 km icosahedral grid to the slightly coarser 12 km HEALPix grid. We hypothesise that precipitation is particularly affected by this issue, as it typically contains many grid cells with zero precipitation, with local clusters of non-zero values at the 15-minutely output interval. Yet, we cannot exclude the possibility that other variables are also affected.

As a consequence, if remapping is required, it is recommended to first remap from the native resolution to a finer resolution grid. As a next step, the conservative nature of the HEALPix hierarchy can be used to compute the coarser level. In this way it is likely to be possible to avoid aliasing and still keep the amount of output data the same.

How to cite: Poschlod, B., Brunner, L., Blanz, B., and Kluft, L.: Output regridding can lead to Moiré pattern in km-scale global climate model data from ICON, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15826, https://doi.org/10.5194/egusphere-egu25-15826, 2025.

Plastic pollution is a global issue, across all environmental compartments. Rivers connect the terrestrial with the marine environment, and they transport various materials, among these plastic pollution. Rivers not only transport plastic, but also accumulate and store it, especially on riverbanks. In fact, plastic deposition and accumulation on riverbanks is a common occurrence. However, our understanding of why plastic is deposited on a certain riverbank is rather limited. Riverbanks along all major Dutch rivers have been monitored for plastic and other litter twice a year by citizen scientists, in some locations since 2018. This provides an extensive dataset on plastic accumulation, and we used these data with the aim of understanding the factors determining plastic concentration/accumulation variability over time and space. We tested multiple riverbank characteristics, such as vegetation, riverbank slope, population density, etc., hypothesized to be related to plastic litter. After having exhausted a long list of auxiliary data and analysis strategies, we found no significant results. Ultimately, we had a close look at ten consistent hotspots of macroplastic litter, along the Meuse, and Waal river. And once again, they seem to have nothing in common. But, there is a pattern, because some riverbanks have consistently very high densities of plastic litter so it does not seem completely random. We have been looking to explain spatial variability, whereas we might have to look at temporal consistency, and we shall not give up our efforts to bring order to this chaos.

How to cite: Hauk, R., Teuling, A. J., van Emmerik, T. H. M., and van der Ploeg, M.: What river plastic hotspots do not have in common, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17676, https://doi.org/10.5194/egusphere-egu25-17676, 2025.

Grande Dixence, the tallest gravity dam in the world, is located in the Swiss Alps on the Dixence River with a catchment area of 4 km² at a towering elevation of 2000m. The lake serves as a collecting point of melt water from 35 glaciers and reaches full capacity by late September, subsequently draining during winter and dropping to lowest levels in April. For a reservoir as large as the Grande Dixence, the variation in hydrological load can be expected to induce changes in crustal stress. The goal of this study was to harness the loading effect of the time-varying level of reservoir load as a source of known stress to investigate the variation in seismic velocity of the bedrock due to changes induced in crustal stress and strain rates. 22 seismic nodes were thus deployed along the banks of the reservoir which were operational from mid-August to mid-September, corresponding to the time period when the lake level reaches its maximum. Of the 22 nodes, 18 were deployed in closely spaced patches of six in order to carry out coherent stacking and to increase the signal-to-noise ratio, besides one group of three nodes and one single node. Measurement quality appears satisfactory: small local earthquakes are recorded well, and the probabilistic power spectral densities (PPSDs) computed for data quality validation evidence the ambient noise levels to be well within the global noise limits. However, the recorded noise is unexpectedly complex and, at periods shorter than 1 second, varies strongly by location. The 0.5--5s (0.2--2 Hz) period band at lakes generally records a diurnally varying noise level, often associated with lake generated microseism. Diurnal variations around 1 second of period are observed in our study as well. The amplitude of ambient noise level around 1 second of period is observed to be highest when the lake level changes, along with the prominent diurnal variation. A similar variation is observed in the seismic velocity variation (dv/v) computed from cross-correlated and auto-correlated ambient noise filtered between 0.5--1 Hz, with dv/v exhibiting a drop with rising lake level. These results provide preliminary evidence for possible change in crustal stress state with changing hydrological load. Future direction of this study consists of analytically modeling the results to quantify the influence of thermobarometric parameters on PPSDs and dv/v, and deconvolve it from the lake induced variations.

How to cite: Uthaman, M., Ermert, L., Ling, A., Junker, J., Ghisleni, C., and Obermann, A.: Temporal variation of ambient noise at the Grande Dixence reservoir recorded by a nodal deployment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17811, https://doi.org/10.5194/egusphere-egu25-17811, 2025.

Rivers play an important role in the global distribution of plastic pollution throughout the geosphere. Quantifying and understanding river plastic pollution is still an emerging field, which has advanced considerably thanks to broad efforts from science, practice, and society. Much progress in this field has been achieved through learning from failures, negative results, and unexpected outcomes. In this presentation we will provide several examples of serendipity and stupidity that has led to new insights, theories, methods, and completely new research lines. We will share what we learned from rivers flowing in the wrong direction, sensors that disappear, equipment blocked by invasive plants, and dealing with suspicious local authorities. Pushing the science sometimes requires an opportunistic approach, embracing surprises and chaos you may face along the way.

How to cite: van Emmerik, T. and the WUR-HWM River Plastic Team: Advancing river plastic research through serendipity and stupidity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18185, https://doi.org/10.5194/egusphere-egu25-18185, 2025.

With the advent of parallel programming in the late 1990s. A port of the than available Max Planck Institutes for Meteorology spectral atmospheric model echam5 to MPI and OpenMP was done. For testing and validation of the hybrid parallelization a coherence algorithm was developed. The implementation has been incorporated into todays NWP and climate model ICON as well. The coherence algoritm consists of several stages: first one MPI rank is running the serial model against an n-task MPI parallelized model. During runtime the state vector is checked for binary-identity. If successfull a m-task MPI version can be compared to an m-task MPI version for high processor counts. The same schema can be used OpenMP parallelization. ONe MPI task runs the model serial using one OpenMP thread and a second MPI task runs k OpenMP threads. Again, the results are compared for binary-identity. As the testing needs to be done automatically, bit-identity is important for testing not necessarily for production.

The tesing revealed plenty of problems during the initial parallelization work of echam5 and showed constant appearing problems in the ICON development phase.

However, far in a couple of century long simulation the bit-identity was just by accident found to be broken: the search of the cause started!

How to cite: Kornblueh, L.: MPI and OpenMP coherence testing and vaildation: the hybris of testing non-deterministic model code, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18400, https://doi.org/10.5194/egusphere-egu25-18400, 2025.

Addressing positive publication bias and clearing out the file drawer has been at the core of the Journal of Trial and Error since its conception. Publishing the trial-and-error components of science is advantageous in numerous ways, as already pointed out in the description of this panel: errors can lead to unexpected insights and warning others about dead ends can prevent wasted time and other resources. Besides those advantages, publishing negative and null results facilitates conducting robust meta-analyses. In addition, predictive machine learning models benefit from training on data from all types of research rather than just data from studies with positive, exciting results; already researchers are reporting that models trained on published data are overly optimistic.

Besides publishing negative and null results as well as methodological failures, the Journal of Trial and Error couples each published study with a reflection article. The purpose of these reflection articles is to have a philosopher, sociologist or domain expert reflect on what exactly went wrong. This helps contextualize the failure, helping to pinpoint the systematic factors at play as well as helping the authors and other scientists to draw lessons from the reported research struggles which can be applied to improve future research.

Publishing failure brings with it some practical challenges: convincing authors to submit manuscripts detailing their trial-and-error; instructing peer reviewers on how to conduct peer review for the types of articles; differentiating between interesting … and uninformative, sloppy science; and determining the best formats to publish various failure-related outcomes in. Authors are still hesitant to publish their research struggles due to reputational concerns and time constraints. In addition, authors often fear that peer reviewers will be more critical of articles describing research failures compared to articles reporting positive results. To counteract this (perceived) tendency of peer reviewers to be more critical of research without positive results, we provide specific instructions to peer reviewers to only assess the quality of the study without taking into account the outcome. This then also ensures that we only publish research that adheres to the standards of the field rather than sloppy science. Whether submitted research provides informative insights is assed by the editor-in-chief and the handling editor.

Finally, we are constantly evaluating and innovating the types of articles we publish. Various types of errors and failures benefit from differing ways of reporting. For example, recently we introduced serendipity anecdotes, a format where scientists can anecdotally describe instances serendipity which occurred during their research. This format allows researchers to focus on the conditions which allowed for the serendipitous discovery rather than the research itself.    

How to cite: Gaillard, S.: Publishing BUGS: Insights from the Journal of Trial and Error, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18981, https://doi.org/10.5194/egusphere-egu25-18981, 2025.

It is common to perform two-dimensional simulations of mantle convection in spherical geometry. These have commonly been performed in axisymmetric geometry, i.e. (r, theta) coordinates, but subsequently we (Hernlund and Tackley, PEPI 2008) proposed using (r, phi) spherical annulus geometry and demonstrated its usefulness for low-viscosity-contrast calculations. 

When performing scaling studies in this geometry, however, strange results that did not match what is expected from Cartesian-geometry calculations were obtained when high-viscosity features (such as slabs) were present. It turns out that this is because the geometrical restriction forces deformation that is not present in 3 dimensions. Specifically, in a 2-D spherical approximation, a downwelling is forced to contract in the plane-perpendicular direction, requiring it to extend in the two in-plane directions. In other words, it is "squeezed" in the plane-perpendicular direction.  If the downwelling has a high viscosity, as a cold slab does, then it resists this forced deformation, sinking much more slowly than in three dimensions, in which it could sink with no deformation. This can cause unrealistic behaviour and scaling relationships for high viscosity contrasts. 

This problem can be solved by subtracting the geometrically-forced deformation ("squeezing") from the strain-rate tensor when calculating the stress tensor. Specifically, components of in-plane and plane-normal strain rate that are required by and proportional to the vertical (radial) velocity are subtracted, a procedure that is here termed "anti-squeeze". It is demonstrated here that this "anti-squeeze" correction results in sinking rates and scaling relationships that are similar to those in 3-D geometry whereas without it, abnormal and physically unrealistic results can be obtained for high viscosity contrasts. This correction has been used for 2-D geometries in the code StagYY (Tackley, PEPI 2008; Hernlund and Tackley, PEPI 2008) since 2010.

How to cite: Tackley, P.:  Adventures in Modelling Mantle Convection in a Two-Dimensional Spherical Annulus and Discovering the Need for "Anti-Squeeze”, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19890, https://doi.org/10.5194/egusphere-egu25-19890, 2025.

The science question: how can we use hydrological process knowledge to understand the timing and magnitude of seasonal streamflow in snow-influenced catchments.

What was known: in general, catchments with colder climates have later and larger seasonal streamflow peaks, because more snow tends to accumulate in colder catchments, and it melts later because the time when melt can occur is later in the year in colder climates. Numerical models with fine space and time resolution were able to resolve these phenomena, but there was no theory which directly linked long term climate to seasonal streamflow.

In 2009 I published a very simple deterministic theory of snow pack evolution. I tested it against snow observations at 6 locations in the western USA and it apparently worked well (although I later discovered that I'd been lucky).

In 2015 I used the snowmelt derived from this deterministic theory to predict timing and magnitude of seasonal streamflow. It did poorly, and revealed untested assumptions in my theory. I tried making the theory slightly more complicated by considering within-catchment variation in climate. This did not help.

In 2016 I created a stochastic version of the theory (a weakness identified in 2015), and then also considered the within-catchment variation in climate. It did better at reproducing measured snow storage, but did not help in understanding seasonal streamflow.

My next step will be to consider all forms of liquid water input, i.e. not just snowmelt but also rainfall.

What survived: I will continue to use the stochastic version of the theory as it is clearly an improvement. I will continue to examine whether within-catchment climate variability is important, but it seems unlikely after two negative results. But whether introducing liquid water input will be sufficient, who can say? I will also try to examine in more detail how it is that the finely-resolved numerical models can do an adequate job, but the theory cannot - it is in this gap that the answer probably lies.  However the models are very complicated, and it is not easy to get a good understanding of exactly what they are doing, even though we know which equations the are implementing.

How to cite: Woods, R.: Some Perfectly Reasonable Ideas that Didn’t Work: Snow Hydrology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20057, https://doi.org/10.5194/egusphere-egu25-20057, 2025.

Climate models are not only numerical representations of scientific understanding but also human-written software, inherently subject to coding errors. While these errors may appear minor, they can have significant and unforeseen effects on the outcomes of complex, coupled models. Despite existing robust testing and documentation practices in many modeling centers, bugs’ broader implications are underexplored in the climate science literature.

We investigate a sea ice bug in the coupled atmosphere-ocean-sea ice model ICON, tracing its origin, effects, and implications. The bug stemmed from an incorrectly set logical flag, which caused the ocean to bypass friction from sea ice, leading to unrealistic surface velocities, especially in the presence of ocean eddies. We introduce a concise and visual approach to communicating bugs and conceptualize this case as part of a novel class of resolution-dependent bugs - long-standing bugs that emerge during the transition to high-resolution models, where kilometer-scale features are resolved.

By documenting this case, we highlight the broader relevance of addressing bugs and advocate for universal adoption of transparent bug documentation practices. This documentation complements the robust workflows already employed by many modeling centers and ensures lessons from individual cases benefit the wider climate modeling community.

How to cite: Gärtner, J., Proske, U., Brüggemann, N., Gutjahr, O., Haak, H., Putrasahan, D., and Wieners, K.-H.: A case for open communication of bugs in climate models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20866, https://doi.org/10.5194/egusphere-egu25-20866, 2025.

Steroidal compounds are crucial biomolecules in nature, governing diverse biological functions and serving as indicators of organic matter origin, depositional environmental history, and facilitating geological correlations in the petroleum geochemistry (Moldowan et al., 1985; Volkman, 2003). Nevertheless, different organisms can generate identical steroidal compounds, so confident identifications of sources can be enhanced by stable isotope analysis. Prior studies have demonstrated the utility of molecular-average d¹³C to improve interpretations of the phylogenetic and environmental origins of steroidal compounds (Freeman et al., 1990). However, there are challenges and limitations associated with interpretation of d¹³C values of steroids in geochemical contexts, including post-depositional alteration and the influence of different abiotic and biotic processes. In addition, d¹³C values of steroidal compounds from different sources might overlap (Piper and Thevis, 2022).

We will present results of a novel Orbitrap-based analytical method for measuring multiple stable-isotope properties of steroidal compounds, including the intramolecular distributions of single and multiple ¹³C and D substitutions, with the aim of providing more reliable constraints of sources, environments and alteration histories. Unlike traditional bulk carbon isotope analysis, site-specific and multiply substituted carbon isotope analysis focuses on specific carbon positions or groups of positions within organic molecules, enabling detection of variations in carbon cycling, metabolic pathways, and microbial processes that may not be evident from bulk measurements alone. A first proof of concept study focuses on forensic discrimination of isotopic structures of natural and synthetic steroids in human subjects for the purpose of sports doping applications. Preliminary results reveal differences in the measured site-specific ¹³C, D and clumped isotope of various isotopologues derived from natural and synthetic steroids despite the similarity in their molecular average isotope values.

References

Freeman, K.H., et al., 1990. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons. Nature343, 254-256.

Moldowan, J.M., et al., 1985. Relationship Between Petroleum Composition and Depositional Environment of Petroleum Source Rocks. AAPG Bull.69, 1255-1268.

Piper, T., Thevis, M., 2022. Investigations in carbon isotope ratios of seized testosterone and boldenone preparations. Drug Test. Anal.14, 514-518.

Volkman, J., 2003. Sterols in microorganisms. Appl. Microbiol. Biotechnol.60, 495-506.

How to cite: Shawar, L., Piper, T., and Eiler, J.: Site-Specific δ13C, D and Clumped Isotope Analysis of Steroidal Compounds for Forensic and Geochemical Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1492, https://doi.org/10.5194/egusphere-egu25-1492, 2025.

The so-called crucial field is an agricultural test project west of Copenhagen since 2001, where various fertilizers (such as cattle manure, mineral fertilizer and organic household waste) have been applied on different sub-plots to study their long-term effects. Moreover, some sub-plots have been 'retired' and received only minimal fertilization after 2012. To investigate the numerous effects on C and N isotopes, I am analyzing stored fertilizer, soil and grain samples. The main points of investigation are

1. how the isotopic composition of the soil and the grain changes depending on the fertilizer treatment over time (caused by the fertilizer delta values or alternated soil processes due to fertilization);

2. how the isotopic delta values of the fertilizers themselves have changed since the beginning of the experiment and

3. how long the soil isotopic delta values take to reach pre-experimental values after 'retirement'.

In addition, it is intended to do GHG-flux measurements to investigate emissions of the sub-plots and  examine whether high emissions can be linked to high delta values in the soil. 

How to cite: loy, B.: The isotopic timeline of an agricultural field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3148, https://doi.org/10.5194/egusphere-egu25-3148, 2025.

An evaluation of the susceptibility of different N management systems to nitrogen (N) losses into the environment requires either the in-situ determination of the individual components of the nitrogen balance or the determination of the recovery of fertilizer N in plants and soil. For both aspects, ¹⁵N methods are essential as the ¹⁵N gas flux method (¹⁵NGF) is the only widespread in-situ method for the determination of dinitrogen (N₂) emissions, and ¹⁵N labelled fertilizers can be used to assess the allocation of fertilizer N to plants and soil.

To evaluate the influence of management history on N losses, we quantified N loss pathways (NH₃, N₂O, N₂, NO₃^- leaching), total N balance and ¹⁵N recovery in soil and plants of two adjacent sites over a two-year cropping sequence. One site was under integrated farming (IF) and the other under organic farming (OF) with frequent legume cultivation and occasional fertilizer input.

Though integrated farming had resulted in significantly higher pH, soil organic C and N content, the emissions of ammonia, dinitrogen and nitrous oxide after cattle slurry application as well as nitrate leaching were low and not significantly different. High ¹⁵N recovery rates in plants and soil agreed well with the low directly measured N losses. Integrating the directly measured losses into the ¹⁵N balance resulted in high overall recoveries of 84 to 100%. Conversely, unrecovered ¹⁵N was on a low level, but higher for OF (12%) than for IF (6%).

Our results confirm that ¹⁵N labelled fertilizers and their recovery can be used as an indicator for N losses, but the spatial variability is high, complicating statistically significant findings. Consideration of N₂ fluxes using the ¹⁵NGF method could not close the ¹⁵N balance, indicating that unaccounted N losses have occurred. Since the directly measured N losses were not significantly different, unaccounted losses could be due to N₂ emissions as their quantification was limited to two weeks after fertilizer application.

Overall, integrated farming history reduced the vulnerability towards N loss, but continuous methods for determination of N₂ emissions, such as isotopomer measurements, need to be tested concomitantly, and uncertainty of ¹⁵N recovery in plants and soil needs to be reduced by more sophisticated sample mixing approaches.

How to cite: Wolf, B., Khan, F., Franco Luesma, S., Hartmann, F., Dannenmann, M., Gasche, R., Scheer, C., Gattinger, A., Niether, W., and Kiese, R.: Role of 15N methods for assessing the susceptibility of agricultural N management systems to environmental N losses, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3735, https://doi.org/10.5194/egusphere-egu25-3735, 2025.

Soil acidification caused by atmospheric sulfur (S) deposition may have a significant impact on plant carbon (C) assimilation and allocation, thereby altering soil organic C (SOC) dynamics. However, it remains largely unknown for how plants allocate photosynthetic C among belowground functional sinks and whether they can leverage these limited C resources to adapt abiotic stresses. We conducted a ¹³CO₂ pulse-labelling experiment in a grassland field to investigate the effects of simulated soil acidification by S addition on photosynthetic C allocation and analyzed the trade-offs among plant belowground functional sinks. We also elucidated the contribution of belowground C allocation to SOC formation. We found that soil acidification decreased the absolute amount of excess ¹³C allocated to both shoots and soils, possibly due to less photosynthetic C assimilation and aboveground biomass production. In contrast, S addition partially increased the excess ¹³C allocated to roots, indicating that a greater proportion of C was allocated to root biomass construction to combat acidification stress. The excess ¹³C in roots related negatively to soil ¹³C but positively to both root biomass and non-structural carbohydrates (NSC), suggesting a possible trade-off relationship in belowground ¹³C allocation between rhizodeposition and root growth. Our research confirms that under soil acidification stress, less photosynthetic C in roots was converted into rhizodeposition C entering the soil, while more was invested in root growth, respiration, and storage to improve their survival and ability to resist environmental stress. Although with lower excess ¹³C allocated to both shoots and soils, soil acidification had no effect on SOC stocks, possibly due to less SOC decomposition accompanied with suppressed microbial activity. These results provide an invaluable insight into plant C allocation strategy and its impact on belowground C dynamics under soil acidification stress.

How to cite: Shang, Y., Wang, R., and Jiang, Y.: Belowground carbon allocation response to soil acidification stress in a meadow grassland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4195, https://doi.org/10.5194/egusphere-egu25-4195, 2025.

The dual nature of tree-ring cellulose hydrogen isotope composition (δ²H) as a hydroclimatic and physiological proxy offers unique opportunities for palaeoclimatic research (Vitali et al. 2022, 2023), yet its application in long-term studies remains limited. Building on recent advances in tree-ring stable isotope research, we analyse the Alpine Holocene Tree-Ring Triple Isotope Record (AHTTRIR, Arosio et al. 2022), a comprehensive dataset spanning 9,000 years of δ²H, δ¹⁸O and δ¹³C measurements from high-altitude Alpine conifer trees. This study focuses on developing novel methodological approaches for δ²H analysis, applying species-specific values to establish the first multi-millennial δ²H chronology, and comparing it with δ¹⁸O chronology from the same dataset, which is known to contain hydroclimatic signals (Arosio et al. 2025). Despite the inherent complexity of δ²H signals and associated methodological challenges, analysis of approximately 7790 δ²H measurements from the AHTTRIR dataset shows that δ²H contains valuable information on both hydroclimatic variability and tree physiological responses. Through comparison with δ¹⁸O data, we show that δ²H provides complementary insights into plant metabolic processes, including storage mobilisation and stress adaptation mechanisms that could occur due to biotic or abiotic events affecting tree vitality, like damage to needles after insect attacks or frost. This dual-isotope approach, incorporating corrections for species- and age-specific effects, allows the separation of climatic signals from physiological responses over millennial timescales. Comparison with independent Alpine paleoclimate proxies and regional records strengthens our understanding of long-term hydroclimatic dynamics and their impact on tree metabolism throughout the Holocene. These results emphasise the importance of preserving long-term trends in isotope data, while highlighting the need for expanded tree-ring isotope research across different species and geographical regions. The establishment of this pioneering δ²H chronology advances our ability to reconstruct past climate variability while providing crucial insights into ecosystem responses to long-term environmental change.

Arosio Tito, Malin Ziehmer, Kurt Nicolussi, Christian Schluechter, Andrea Thurner, Andreas Österreicher, Peter Nyfeler, and Markus Christian Leuenberger,. 2022. “Alpine Holocene Triple Tree Ring Isotope Record.” PANGAEA, 2022. https://doi.pangaea.de/10.1594/PANGAEA.941604.

Arosio T, Leuenberger M., Nicolussi K, Esper J, Krusic P, Bebchuk T, Tegel W, Hafner A, Kirdyanov A, Schlüchter C, Reinig F, Muschitiello F and Büntgen U. 2025. “Tree-ring stable isotopes reveal a Holocene-long drying trend for central Europe”. In Revision to Science Advances

Vitali, Valentina, Elisabet Martínez-Sancho, K. Treydte, Laia Andreu-Hayles, Isabel Dorado-Liñán, Emilia Gutierrez, Gerhard Helle, Markus Leuenberger, Neil J. Loader, and Katja T. Rinne-Garmston. 2022. “The Unknown Third–Hydrogen Isotopes in Tree-Ring Cellulose across Europe.” Science of the Total Environment 813:152281.

Vitali, Valentina, Richard L. Peters, Marco M. Lehmann, Markus Leuenberger, Kerstin Treydte, Ulf Büntgen, Philipp Schuler, and Matthias Saurer. 2023. “Tree-Ring Isotopes from the Swiss Alps Reveal Non-Climatic Fingerprints of Cyclic Insect Population Outbreaks over the Past 700 Years.” Tree Physiology 43 (5): 706–21.

How to cite: Arosio, T., Leuenberger, M., Nicolussi, K., and Saurer, M.: The dual nature of the hydrogen stable isotopes in tree-rings of the Holocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5149, https://doi.org/10.5194/egusphere-egu25-5149, 2025.

Pollution of surface and shallow groundwater by nitrate (NO₃^-) is a global concern resulting in deterioration of drinking water quality. Stable isotopes of NO₃^- (δ¹⁵N and δ¹⁸O) can be used to trace its sources which have distinct N and O isotopic signatures. The isotopic values can also be used to identify areas of natural remediation through biogeochemical processes such as denitrification. Conversion of aqueous NO₃^- to N₂O headspace gas by Ti(III) reduction is a new method for analysis of NO₃^- stable isotopes. Previous literature introduces the analytical procedure but provides limited guidelines for instrument set-up and operation. Here, we present an automated purge and trap isotope ratio mass spectrometer (P&T-IRMS) combined with the Ti(III) reduction method for analysis of δ¹⁵N and δ¹⁸O in NO₃^-. The P&T-IRMS base analytical precision was ±0.3‰ and ±0.2‰ for δ¹⁵N and δ¹⁸O, respectively. Isotopic values were quantified down to an N₂O gas concentration of 1 µl L^-1 for δ¹⁵N and 2 µl L^-1 for δ¹⁸O. The target NO₃^--N concentration needed for accurate measurements was 0.2 mg L^-1. Comparison of δ¹⁵N and δ¹⁸O measured using the P&T-IRMS by Ti(III) reduction with EA-IRMS values showed high accuracy. The measurement precision (SD) and uncertainties (u) for our KNO₃^- internal standard were ±0.2 (±0.6) and ±0.2 (±0.9) for δ¹⁵N and δ¹⁸O, respectively. The P&T-IRMS and Ti(III) reduction method set-up showed low quantification limits and acceptable accuracy and precision in line with other well-established methods for analysis of NO₃^- stable isotopes. The provided guidelines will assist laboratories which utilize IRMS headspace gas instrumentation with the process of IRMS set-up and operation and establishment of an independent analytical procedure for the Ti(III) reduction method. 

How to cite: Gcakasi, M. N., Stumpp, C., and Watzinger, A.: Establishment of a purge and trap continuous flow isotope ratio mass spectrometer system for analysis of stable nitrate isotopes (δ15N and δ18O) in water samples by Ti(III) reduction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5412, https://doi.org/10.5194/egusphere-egu25-5412, 2025.

The C¹⁸O¹⁶O/C¹⁶O¹⁶O fractionation during photosynthesis (Δ¹⁸O_A) carries rich information about plant physiology and environmental conditions, which is crucial for plant physiological, ecological, and biogeochemical studies. Δ¹⁸O_A is mainly determined by the isotopic fractionation during diffusion and the CO₂-leaf water oxygen exchange reaction. Therefore, Δ¹⁸O_A is believed to relate to leaf physiological parameters such as the evaporative ¹⁸O enrichment of leaf water (Δ_e), CO₂ influx and efflux. Based on current mechanistic understanding of Δ¹⁸O_A, oxygen isotope composition of atmospheric CO₂ (δ_a) can be used to estimate global gross primary productivity and to separate photosynthetic and respiratory CO₂ fluxes at the ecosystem scale. However, there is uncertainty about the key physiological factors responsible for changes in Δ¹⁸O_A and whether there is a difference in Δ¹⁸O_A between C₃ and C₄ plants.

In this study, we investigated the response of Δ¹⁸O_A to short-term changes in CO₂ levels in three C₃ species (Helianthus annuus, Vigna unguiculata and Triticum aestivum) and one C₄ species (Cleistogenes squarrosa) grown under different levels of vapour pressure deficit (VPD) and nitrogen supply. Utilising a new mass-balance equation that distinguishes metabolic (mitochondrial and photo-respiratory CO₂) and purely diffusive (retro-diffusive CO₂) CO₂ fluxes, we assessed the effect of the gross CO₂ efflux from leaves.

We found a significant CO₂ effect on Δ¹⁸O_A for C. squarrosa, but not for the C₃ species. Δ¹⁸O_A was not significantly correlated with Δ_e of the C₃ species, and Δ¹⁸O_A of C₄ species was not sensitive to changes in Δ_e driven by VPD. The gross CO₂ efflux and Δ¹⁸O_A were significantly correlated for both C₃ and C₄ species, demonstrating its role in regulating Δ¹⁸O_A. We also found that the C₃ species had significantly higher Δ¹⁸O_A than the C₄ species, due to the lower ratio of intercellular to atmospheric CO₂ (C_i/C_a) in the latter. Our study reveals the distinct difference in Δ¹⁸O_A between C₃ and C₄ species and the remarkable relationship between Δ¹⁸O_A and physiological parameters, which provides new insights into how Δ¹⁸O_A can be used to infer carbon cycle processes from leaf to ecosystem scales.

How to cite: Gong, X., Huang, S. M., Yu, Y. Z., and Schnyder, H.: Photosynthetic C18OO fractionation is related to within- and between-species variations in photosynthetic traits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5413, https://doi.org/10.5194/egusphere-egu25-5413, 2025.

Explosive volcanic eruptions are capable of producing large amounts of ash, that affect the surrounding ecosystems. Once the ash comes in contact with seawater, the metal salts coating the ash particles quickly dissolve, releasing essential trace metals into the environment. Moderate ash exposure increases the concentrations of several essential metals in the coral host tissue and their algal endosymbionts. As a result, the photosythetic activity of algal symbionts increases, leading to healthier corals and suggesting that ash has a fertilizing effect on symbiotic corals. This study aims to investigate how the duration of ash exposure and the ash concentration affect the photophysiological state of corals and whether metal concentrations and stable isotope ratios can provide insight into the underlying biological processes.

Microcolonies of the scleractinian coral Stylophora pistillata were grown under controlled laboratory conditions, including pH, temperature and irradiance. The corals were divided into various tanks under four different conditions: a control group without ash exposure and three ash-exposure treatments (3.75 g ash/week for three weeks, 7.5 g ash/week for three weeks and  7.5 g ash/week for six weeks). These conditions were chosen to evaluate the effects of different amounts of ash and exposure durations on coral responses. Throughout the experiment, various photophysiological parameters were monitored, including photosynthesis and respiration rates, as well as the photosynthetic efficiency (measured by e.g. relative electron transfer rate and F_v/F_m). At the end of the experiment, Cu, Fe, and Zn concentrations and isotopic compositions (δ⁵⁶Fe, δ⁶⁵Cu and δ⁶⁶Zn) were measured on the symbionts and tissues of three nubbins per tank.

Volcanic ash exposure enhanced the coral photosynthetic activity, although trace metal concentrations and isotope ratios didn’t change between the exposure conditions. The effect was also independent of the intensity or duration of exposure. However, δ⁶⁵Cu levels in the coral host correlated almost perfectly with the photosynthetic parameters; corals with lighter δ⁶⁵Cu demonstrated better photosynthetic performance. We propose that the δ⁶⁵Cu serves as an indicator of the photochemical efficiency and may be linked to the antioxidant capacity of the coral host to mitigate oxidative stress, with stress likely increasing with long-term exposure. Understanding physiologically-induced metallomic responses following ash exposure improves the understanding of ecosystem resilience and collapse.

How to cite: Förster, F., Sauzéat, L., Ferrier-Pagès, C., Reynaud, S., and Sheldrake, T.: δ65Cu as biomarker for the photophysiological state of a symbiotic coral , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5914, https://doi.org/10.5194/egusphere-egu25-5914, 2025.

The stable oxygen (O) and carbon (C) isotope composition of bulk carbonate in sediments is widely used for paleoenvironmental reconstructions. This approach, however, does often not consider seasonal variability in environmental conditions. Although, this can be overcome by the consideration of the specific composition of ostracod shells which have a relatively short and variable life history, this approach has not been consequently applied in the past. Only few studies investigated the potential of ostracodes in high-resolution (e.g. seasonal) paleoenvironmental reconstructions, based on their stable isotope composition, so far.

Seasonal meteorological conditions in tropical areas such as the Caribbean region are broadly divided into dry and rainy seasons with often profound effects on hydrological and ecological conditions. How this hydrological seasonality is archived by ostracode stable isotopes (δ¹⁸O, δ¹³C) is largely still unclear. The present study uses variations in lake water isotopes (δ¹⁸O, δ²H) and δ¹³C_DIC together with the hydrochemical composition (major and trace elements) of the hyperhaline Lago Enriquillo. Water samples and living ostracodes were taken during March and September (i.e. dry and rainy season) in 2022. The C and O isotopic composition of single ostracode valves of different ostracode species (Cyprideis similis, C. edentata, Perissocytheridea cribrosa, Thalassocypria cf. sarbui) were analysed. These species provide differences in their temporal-spatial distribution but are generally restricted to the upper 8 m water depth of the lake. Both types of life cycles (permanent and seasonally restricted) are shown by the ostracodes species.

Questions that are addressed in this study include: Does the water isotopic composition reflect significant differences between the dry and the rainy season? What are the sources and sinks of water for the lake? Do ostracode δ¹⁸O and δ¹³C values reflect the composition of water and dissolved DIC in the lake? How does ostracode ecology (i.e. habitat preferences, life cycle) affects their isotope signatures?

Our results show a low intra-annual variation in δ¹⁸O and pronounced local variability of δ¹³C_DIC values of the lake water. Ostracode δ¹⁸O and δ¹³C signatures reflect the lake water composition. The individual species display differences in their isotopic composition and variation ranges. δ¹⁸O results agree with the low intra-annual variation of the lake water and display a pronounced gradient with increasing values towards areas with reduced influence of inflows. δ¹³C values of ostracodes, on the other hand, show strong local differences between and even heterogeneity within samples sites.

Results imply that the lake water was buffered against seasonal hydrological variations during the sampling period, but reveals large spatial variations associated with e.g. strong contrast between inflows and the lake reservoir. The deduction of paleoenvironmental conditions of Lago Enriquillo based on stable isotopes of fossil ostracodes requires therefore consideration of multiple species. The ostracode proxy information then may help to deduce past changes in the lake water cycle.

How to cite: Wrozyna, C., Berndt, C., Reuter, M., Böttcher, M. E., Schröder, B., Garcia Cocco, E., and Haberzettl, T.: Seasonal dynamics of modern ostracod stable isotope (δ18O, δ13C) compositions in a large tropical lake (Lago Enriquillo, Dominican Republic) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6283, https://doi.org/10.5194/egusphere-egu25-6283, 2025.

A quantitative understanding of ¹⁸O fractionation mechanisms in plants is highly desirable for effective utilization of the δ¹⁸O signatures of plant cellulose (δ¹⁸O_cel) in diverse climatic and ecological applications. According to the isotope theory, biochemical fractionation associated with oxygen isotopic exchange represents a critical control of δ¹⁸O_cel. Biochemical fractionation operates in both autotrophic (i.e., leaf) and heterotrophic (i.e., stem/trunk) organs, with the current δ¹⁸O_cel model assuming that its effect amounts to c. 27‰ in both types of organs. However, with respect to the autotrophic fractionation factor (ε_{bio_A}), calculations of the deviations of the δ¹⁸O enrichment of sucrose (Δ¹⁸O_ls) from that of water (Δ¹⁸O_lw) in a bulk leaf, -- as performed in many previous studies, -- have led to a wide range of ε_{bio_A} estimates (i.e., from 22.4 to 34‰) across different species. Such a bulk-leaf based estimation method, however, does not provide a precise quantification of ε_{bio_A}. This is because the oxygen exchange-determined intrinsic relationship between Δ¹⁸O_ls and Δ¹⁸O_lw, namely Δ¹⁸O_ls = Δ¹⁸O_lw + ε_{bio_A}, is not expected to hold at the bulk leaf level owing to complications arising from within-leaf heterogeneity that is commonly present in Δ¹⁸O_lw and sucrose synthesis rate (r_suc).

Here, based on explicit consideration of potential within-leaf heterogeneity in r_suc, as well as of spatial variation characteristics of Δ¹⁸O_lw as informed by the Farquhar-Gan model, we suggest that the isotopic relationship between bulk Δ¹⁸O_ls and Δ¹⁸O_lw should instead be expressed as the following: Δ¹⁸O_ls = β*Δ¹⁸O_lw + ε_{bio_A}, with β being a composite variable highly relevant to spatial variation of r_suc across the leaf. Further analysis demonstrates that β can be markedly larger or smaller than unity depending on whether r_suc progressively increases or decreases along the leaf length. With the derivation of this new equation delineating bulk leaf isotopic relationships, we propose a regression approach via which ε_{bio_A} can be robustly quantified as the intercept of a linear relationship between Δ¹⁸O_ls and Δ¹⁸O_lw. We subsequently applied such a regression method under highly controlled experimental settings to determine ε_{bio_A} in diverse plant species under different growth temperatures. The application of this new method allowed us to successfully constrain the estimate of ε_{bio_A} at 25°C to a narrow range of 26.4‰ ± 1.5 per mil across a range of plant species, closely aligning with the traditionally assumed value of 27‰. Additionally, a significantly inverse relationship of ε_{bio_A} with temperature was revealed from our experiment. Further comparisons will be made between our revealed temperature dependence of ε_{bio_A} with that of the heterotrophic factor ε_{bio_H} as reported in Sternberg and Ellsworth (2011). Our study represents a step forward in constraining isotope parameters in the δ¹⁸O_cel model, which has important implications for isotope-based paleoclimatic reconstruction and ecophysiological applications.

How to cite: Wen, W., Tang, X., and Song, X.: Towards a refined method for estimating 18O autotrophic fractionation during sucrose synthesis in a bulk leaf, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7605, https://doi.org/10.5194/egusphere-egu25-7605, 2025.

In the last few decades, the Mediterranean area has been extensively impacted by prolonged and intense droughts and heat waves. These events, combined with heavily landscape management, ongoing for thousands of years in the region, have been affecting the ecosystems’ resources such as water availability and nutrient cycles. Mediterranean vegetation responds differently to natural and human-induced changes and within the same species, different compartments (e.g. leaves, branches and roots) may exhibit diverse responses to these stressors, providing valuable bioindicators. Stable isotopes, particularly carbon (C) and nitrogen (N), have become widely used as effective tools to study plant responses to environmental gradients such as plant water-use efficiency, nitrogen-use strategies and ecosystem functioning.

Within ITINERIS (Italian integrated environmental research infrastructures system) project, we present preliminary findings comparing d¹³C and d¹⁵N values in soil and vegetation samples from coastal urban and peri-urban parks along a latitudinal gradient in Italy. To evaluate the relationships between isotopic signatures and environmental changes, soil and vegetation samples were collected in three ICOS (Integrated Carbon Observation System) stations located along the coastal latitudinal transect (Pisa, Rome and Naples). Holm oak (Quercus ilex) was selected as a potential bioindicator of environmental changes and anthropogenic disturbances due to its abundant presence at all three sites. Soil and plant compartments (e.g., leaves of different ages, branches, pollen, fine roots) were collected and analysed at the start and end of the growing season to investigate the response of Mediterranean species down to organ level to a thermo-pluviometric gradient.

The main findings of this study have highlighted differences in C and N concentrations and isotope compositions across the latitudinal gradient and seasons. Capodimonte (Naples), the most southern site, reveals an enrichment in d¹³C and d¹⁵N in leaves compatible not only with a response to hot and dry climate, but also to a much higher degree of anthropization. Castel Porziano (Rome) exhibits a similar trend but lower d¹⁵N and N concentration. San Rossore (Pisa), the northernmost site is subject to less water stress during summer season, resulting in more diluted d¹³C and d¹⁵N values. The leaves in the fall showed higher d¹³C and N concentration compared to spring. Branches were about 1 ‰ enriched in ¹³C compared to leaves due to post-photosynthetic isotope fractionations. Further analyses are underway on other plant compounds, including pollen, to identify the most suitable bioindicators of Mediterranean species’ response to climate change and human impact, with potential applications in the region’s management and conservation strategies.

How to cite: Tunno, I., Scartazza, A., Micali, M., Calfapietra, C., Guidolotti, G., and Papale, D.: Carbon and Nitrogen stable isotopes comparison in urban ecosystems along a Mediterranean latitudinal transect, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8622, https://doi.org/10.5194/egusphere-egu25-8622, 2025.

Temporal variability of tree-ring cellulose δ²H (δ²H_ring-cel) can be a unique tool for understanding tree physiology and climate. However, we do not fully understand the drivers of temporal variability in δ²H_ring-cel. Investigating seasonal δ²H_ring-cel in boreal forests is particularly challenging. Previous studies on intra-annual tree-ring δ¹⁸Ohave shown that tree-ring isotope variability can result from the combined but opposing effects of source water and leaf assimilates, a dynamic likely relevant for δ²H_ring-cel as well. To be able to use δ²H_ring-cel as a standalone and reliable bioindicator, it is important to understand the variable hydrogen isotope fractionation between source water and tree rings. Our study aimed to provide context to this variability in a natural forest by being the first study to trace intra-annual δ²H_ring-cel to the δ²H of its sources and drought indices.

The δ²H of source water, leaf water and carbohydrate pools (i.e. water-soluble carbohydrates, starch) were analysed from five pine (Pinus sylvestris) trees during 2019 at Hyytiälä forest, Finland. Their δ²H were used to model continuous δ²H of source water (δ²H_source) and leaf sugars (δ²H_leaf-sug). Modelled and measured δ²H_leaf-sug matched moderately for 2019, and the model was applied to predict δ²H_leaf-sug during 2018. Intra-annual δ²H_ring-cel were analysed in these two years at a resolution of 5-10 timepoints per year, and they were allocated to xylogenetic timepoints. They were then compared to time-integrated δ²H_source, δ²H_leaf-sug, net assimilation rate, evapotranspiration and drought indicators.

Carbohydrate δ²H was significantly different among leaves, branches and stems. δ²H_ring-cel had strong time-integrated relationships to modelled δ²H_source, net leaf assimilation rate and evapotranspiration, but the direction of their relationships was different between years. At monthly resolution, water-soluble carbohydrate δ²H measured from one year-old needles had a strong, positive relationship to δ²H_ring-cel. Similarly, the modelled δ²H_leaf-sug, had strong positive relationships to δ²H_ring-cel, which were robust between years. δ²H_ring-cel also had strong relationships to Standardized Soil Moisture Index (SSMI). 

We show that the role of δ²H_leaf-sug superseded the role of δ²H_source in intra-annual δ²H_ring-cel, because δ²H_leaf-sug had a consistent relationship to intra-annual δ²H_ring-cel in both years while δ²H_source did not. This clearly supports the growing body of evidence that δ²H_ring-cel is strongly mediated by physiological processes. Our results show promise for δ²H_ring-cel functioning as a bioindicator of soil drought related physiological stress signals in long-term tree ring chronologies. 

How to cite: Angove, C., Lehmann, M., Saurer, M., Tang, Y., Sahlstedt, E., Young, G., Treydte, K., Szejner, P., Leppä, K., Schiestl-Aalto, P., Wiesenberg, G., and Rinne-Garmston, K.: Intra-annual tree-ring cellulose δ2H as an indicator of drought, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9771, https://doi.org/10.5194/egusphere-egu25-9771, 2025.

Dissolved oxygen (DO) is one of the most fundamental health indicators of aqueous ecosystems. Beyond climate change and habitat modifications, excessive nutrient and pollutant inputs can significantly degrade this critical water quality parameter. Eutrophication, for instance, can drive harmful algal blooms, oxygen depletion and biodiversity loss.

In our study, we present seasonal data on DO concentrations and its oxygen stable isotope ratios (δ¹⁸O_DO*) from five campaigns along the Danube River in 2023 and 2024, complemented by particulate organic carbon (POC) data as a biomass indicator. Our results highlight dynamic seasonal patterns. Photosynthesis dominated in spring and summer, while respiration and atmospheric equilibration prevailed in fall and winter. Notable hotspots were identified in the middle and lower Danube, with DO peaks of 0.35 mmol/L and 0.40 mmol/L, accompanied by δ¹⁸O_DO* enrichments of +9.8 ‰* and +12.5 ‰* and POC concentrations of 0.25 mmol/L and 0.24 mmol/L. These regions, characterized by reduced river gradient und resulting lower flow velocities and turbulence, suggest enhanced primary producer activity. Notably, nutrient levels remained low, with nitrate under 0.29 mmol/L and phosphate largely undetectable, indicating minimal anthropogenic influence—likely due to environmental improvements and reduced industrial impacts in the catchment. All DO levels were within safe ecological ranges (> 0.06 mmol/L), ruling out hypoxia or harmful algal blooms.

How to cite: Maier, J., Visser, A.-N., Schubert, C. M., Wander, S. T., and Barth, J. A. C.: Seasonal Dynamics of Dissolved Oxygen in the Danube River: The Role of Primary Producers and Slope, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9857, https://doi.org/10.5194/egusphere-egu25-9857, 2025.

Intra-annual variations of oxygen isotope composition (δ¹⁸O) in tree rings offer insights into tree ecophysiology and how trees respond to climate. In this study, we focused on the interplay between the δ¹⁸O from source-water, leaf-water and photosynthates to understand how seasonal trends are integrated in tree rings. We conducted a seasonal analysis of Pinus sylvestris in Finland. Our findings reveal a significant reduction in the seasonal variability and trends of δ¹⁸O from needle-water to tree rings. This dampening effect on the seasonal trends is due to the opposing seasonal patterns: source-water δ¹⁸O increases from early spring to late summer, while the evaporative enrichment of ¹⁸O recorded in the δ¹⁸O of photosynthates at the leaf level decreases over the same period. Additionally, oxygen isotope exchange between source water and phloem sugars during wood formation  contributes to the dampening of the evaporative δ¹⁸O signals in tree rings. These findings enhance our understanding of how δ¹⁸O integrates into tree rings, particularly the seasonal signals preserved along the tree growing season. This study offers new perspectives on how intra-annual δ¹⁸O proxies capture seasonal environmental variations over time, which is crucial for refining climate reconstructions and improving our knowledge of tree physiological responses to climate.

How to cite: Szejner, P., Tang, Y., Angove, C., Schiestl-Aalto, P., Sahlstedt, E., Young, G., Daniel B, N., Ansgar, K., Saurer, M., and Rinne-Garmston, K. T.: Opposing seasonal trends in source water and sugar dampen intra-annual variability in tree rings oxygen isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10355, https://doi.org/10.5194/egusphere-egu25-10355, 2025.

Biochar as an alternative filter to activated charcoal was tested for the removal of tetrachloroethene (PCE) and Naphthalene (NAP) from contaminated groundwater by means of sorption and biodegradation in batch and column experiments. Microbial communities were extracted from the aqueous and solid phases and analysed using 16S rRNA gene amplicon sequencing. Microbial biomass and its carbon isotope composition were determined using microbial phospholipid fatty acids (¹³C-PLFA) analysis. This approach enabled a quantitative and functional observation of the microbial community besides identifying the relevant bacteria.

Molecular biological analyses of the PCE experiments confirmed that organo-halide respiration bacteria (OHRB) established after inoculation both in the batch and throughout the columns. PLFA analysis revealed that microorganisms and also those groups that can be assigned to the PCE-degrading organisms preferentially colonize biochar, while activated charcoal is avoided possibly due to the higher PCE sorption capacity of the activated charcoal and hence lower bioavailability of PCE. The carbon isotope value of the microorganisms (¹³C PLFA) indicates the use of biochar as a carbon source and/or the presence of strongly isotope-fractionating biochemical processes such as methanogenesis / methane oxidation. The microbial communities were influenced by the factor char and its physical/chemical properties. It is therefore advisable to choose the filter material not only on the basis of the sorption capacity, but above all on the synergy effects that leads to a permanently active microbial community and an extension of the filter life due to the continuous and complete degradation.

The living microbial biomass in the aerobic naphthalene columns was a factor of 4 higher than in the anaerobic PCE columns. The distribution of microorganisms was similar to that in the PCE degradation experiments; i.e. greater colonization of the biochar filters compared to the activated charcoal filters. Furthermore, the microorganisms responded to naphthalene supply with increased microbial biomass and naphthalene incorporation. Once the naphthalene addition was stopped, the microorganisms were able to convert sorbed naphthalene (in the presence of ethanol). This ability is a strong indicator of the sustainability and self-cleaning potential of the colonized biochars. However, high levels of colonization and biofilm development may increase the risk of clogging negatively impacting filter system sustainability. The insights gained from this study are crucial for advancing global efforts in groundwater remediation and sustainable environmental management.

How to cite: Watzinger, A., Leitner, S., Stumpp, C., Soja, G., and Keiblinger, K.: Carbon stable isotope analysis in groundwater remediation – The role of microbial biofilm communities and biochar in PCE and NAP degradation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10869, https://doi.org/10.5194/egusphere-egu25-10869, 2025.

How to cite: Barker, S., Preece, C., Berstan, R., and Seed, M.: Analysis of dissolved nitrate stable isotopes using the one-step Ti (III) reduction method and Elementar EnvirovisION System , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11009, https://doi.org/10.5194/egusphere-egu25-11009, 2025.

Double carbonates of the norsethite-family (Ba(Mg,Mn,Fe)[CO₃]₂) are used as crystal chemical and geochemical analogues for the prominent rock-forming mineral dolomite (CaMg[CO₃]₂) and the less common kutnahorite (CaMn[CO₃]₂). Selected family members have been observed to occur in low- and high-temperature natural systems, like Baltic Sea sediments or different types of ore deposits. For most of the norsethite-members, neither the thermodynamic nor the reaction kinetic properties are well constrained or even known, so far.

In the present study, the dissolution behaviour of double and triple carbonate members of the norsethite family were dissolved in CO₂-saturated solutions at 25°C and 1 atm total pressure. The carbonates were synthesized at high P and T and characterized as described by Liang et al. (2021, 2025) and Böttcher et al. (2022). Free-drift batch-type reactors were used. Both, the congruent and incongruent parts of the dissolution process were investigated and the partitioning of metals and stable carbon isotopes was followed. At the end of the experiment, carbonate solid-solutions were precipitated by letting CO₂ to degas.

The dissolution in aqueous solutions was found to be initially congruent with respect to metal stoichiometry. The solution composition was interpreted using PHREEQC. Extrapolation of experimental congruent reaction parts give the solubility product and the free energy of formation of the respective carbonate and the time-dependent reaction path allows for the extraction of dissolution kinetic parameters. The development of ¹³C contents of dissolved inorganic carbon represent an experimental verification of carbonate dissolution in a system open with respect to a CO₂ gas phase (sensu Garrels & Christ, 1965 and Deines et al., 1974).

These new experimental results form a base to include these phases into modelling codes for natural or underground CO₂-storage systems.

How to cite: Böttcher, M. E., Haršányi, A. S., Dellwig, O., Grathoff, G., Schmiedinger, I., and Liang, W.: Thermodynamic stability and reactivity of dolomite-analogues from the norsethite-family: Carbon isotope and metal release during experimental dissolution at 25°C and 1 atm total pressure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12689, https://doi.org/10.5194/egusphere-egu25-12689, 2025.

The hydrogen (δ²H) and oxygen (δ¹⁸O) isotopic signatures of tree rings depend on that of the environmental water sources, such as precipitation and soil water, taken up by trees (i.e., "source water"). Analyzing δ²H and δ¹⁸O of tree rings is thus a promising approach for reconstructing the spatio-temporal origins of tree water sources. However, such reconstructions remain rare, likely due to methodological challenges, including the analysis of hydrogen isotopes in tree rings and the availability of historical source water isotope data.

In this study, we present a first attempt to reconstruct the temporal origins of water used by trees during the 20th century (1901–1995) with annually resolved tree-ring δ¹⁸O time series. The reconstruction is based on a δ¹⁸O chronology of whole wood, sampled from the latewood of spruce (Picea abies) at Bettlachstock, Switzerland. Our choice of site and species reflects a conservative approach, as a transfer function linking δ¹⁸O of tree-ring cellulose to the δ¹⁸O of source waters (e.g., stem xylem water and soil solutions) was recently established over a 17-year period (2006–2022) at the same site. After accounting for the isotopic offset between whole wood and cellulose, we estimated δ¹⁸O values of soil solution (80 cm depth) and stem xylem water during the growing season (May–September) using a linear transfer function. Further, using modeled precipitation δ¹⁸O data and the estimated δ¹⁸O of soil solution and xylem water, we deduced interannual variations in the seasonal origin index (SOI) of soil solution and xylem water during the 20th century.

Our results show that the reconstructed δ¹⁸O values and SOI of xylem water were higher than those of soil solutions, suggesting a greater contribution of summer water to xylem water than to soil solutions. Interestingly, while conditions from 1900 to 1970 remained relatively stable, we observed abrupt increases in SOI for both soil solutions and stem xylem water between 1970 and 1995. These recent changes were not due to an increase in summer precipitation amount but may be linked to shifts in seasonal precipitation patterns, causing a relative increase in the contribution of summer precipitation in tree water sources.

Despite these findings, uncertainties in precipitation isotope data and transfer functions need further investigation to draw more definitive conclusions. We hope this study will stimulate discussion on the advances and limitations of using tree-ring isotopes to reconstruct historical water sources.

How to cite: Holloway-Phillips, M., Diao, H., Bernhard, F., Wieland, A., Floriancic, M., Waldner, P., Treydte, K., Saurer, M., von Arx, G., Gessler, A., Meusburger, K., and Lehmann, M.: Tree-ring isotope-based 20th century reconstructions of the seasonal origin of water sourced by trees: Advances and limitations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12734, https://doi.org/10.5194/egusphere-egu25-12734, 2025.

Cavity Ring-Down Spectroscopy (CRDS) has emerged as a critical tool for measuring water isotopes in climate, environmental, and hydrological research. Key features of CRDS analyzers, such as the L2130-i and L2140-i, include high precision, minimal drift, and field deployability. However, the precision and accuracy requirements of water isotope measurements vary by application. For example, paleoclimate studies demand the highest precision (on par with IRMS), while other applications prioritize rapid analysis of large sample sets over precision.

In this study, we present updated methodological recommendations for water isotope analysis using CRDS, tailored to different precision, accuracy, and throughput requirements. We evaluated a range of analytical and data processing methods using the WICO 2024 sample set. This set, provided by the IAEA, includes six water samples with δ¹⁸O values ranging from -22‰ to +1‰ and δ²H values spanning from -163‰ to +17‰. The samples were analyzed on a Picarro L2130-i instrument in both Standard and Express mode [1]. Data were processed using the analyzer's built-in ChemCorrect software and the open-source FLIIMP software [2], which enables advanced data correction techniques such as drift and memory correction.

Our findings highlight the trade-offs between precision and throughput for different use cases and underscore the importance of selecting appropriate analysis and processing methods based on specific research needs.

References

[1] Galili, N. et al. (2025). Cavity Ring-Down Spectroscopy Performance and Procedures for High-Throughput δ¹⁸O and δ²H Measurement in Water Using “Express” Mode. Applied Spectroscopy.

[2] Sodemann, H. et al. (2023). FLIIMP - a community software for the processing, calibration, and reporting of liquid water isotope measurements on cavity ring-down spectrometers. MethodsX, 11, 102297.

How to cite: Hofmann, M., Woźniak, J., and Drori, K.: Methodological Recommendations for Water Isotope Measurements Using CRDS: Balancing Throughput and Precision, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13667, https://doi.org/10.5194/egusphere-egu25-13667, 2025.

Previous nitrogen isotope studies of bulk proteins extracted from ancient Atlantic cod (Gadus morhua) tissues document a 1-2‰ decrease in δ¹⁵N values over the last couple of centuries (Harris, 2011; Lueders-Dumont et al., 2018). Due to the nature of the nitrogen isotope signal in bulk proteins, this isotopic shift may be attributed to a decrease in trophic level and/or a change in baseline nitrogen in the Gulf of Maine over this time period. Here, we analyze the  δ¹⁵N composition of individual amino acids from ancient cod bone collagen to tease out the relative importance of shifts in trophic level vs baseline nitrogen sources to cod diets through time. Preliminary data indicate that  δ¹⁵N values of phenylalanine (“source” amino acid) extracted from cod bone collagen became more depleted in δ¹⁵N over the last 500 years and into the modern record. These shifts in δ¹⁵N_Phe are in agreement with those found in δ¹⁵N_Phe of deep-sea corals (Sherwood et al., 2011) and bivalves (Whitney et al., 2019) from the Gulf of Maine over the last 100 years. The fact that similar trends are seen in three different species occupying different ecological niches suggests the shift in source nitrogen may reflect broad changes in hydrographic conditions in the Gulf of Maine. More work is needed to corroborate these preliminary findings and is currently underway. 

How to cite: Turtle, S., Johnson, B., and Dostie, P.: δ15N of Amino Acids in Ancient Cod Bone Collagen Track Shifts in Baseline Nitrogen & Cod Trophic Levels in the Gulf of Maine for the Past 4,400 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14238, https://doi.org/10.5194/egusphere-egu25-14238, 2025.

Cavity ringdown spectroscopy (CRDS) is a well-established technique used for measuring a large variety of gaseous species which are known to absorb light radiation at specific wavelengths, e.g., CO₂, CH₂, C₂H₄, water vapors, etc. In the field of environmental and geochemical research, CRDS is commonly used to determine the isotopic ratios of light isotope families, like hydrogen, carbon, oxygen, etc. Similarly, laser ablation (LA) is a solid sample introduction method which is used in conjunction with a variery of spectrometric and spectroscopic techniques and works by focusing a laser beam (of various wavelengths, pulse width and energy) onto the sample surface to convert minute amounts of the solid into fine aerosol, or gaseous phase.

Hyphenating the two techniques is a recent addition to the earth sciences tool set [1,2]. While still in its infancy, LA CRDS is a promising technique for fast, highly accurate and spatially resolved stable isotope measurements. In this contribution we look at the figures of merit of the technique when measuring δ¹³C, comparing different types of lasers (pulsed nanosecond solid state 213 nm wavelength, and continuously emitting infrared CO₂ laser) on both organic (wood, cellulose, plastics, and plant derived material) as well as inorganic matrices (soils, CaCO₃) which are critical proxies for environmental and climatic studies. We also investigate the impact of increased spatial resolution (i.e., tens of micron spot sizes) on the accuracy and precision of the analysis.

[1] Stremtan, C., Wozniak, J., Puscas, C. M., and Tamas, T.: Laser Ablation – Cavity Ring Down Spectrometry, a new method for the in-situ analysis of δ13C of organic and inorganic carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17192, https://doi.org/10.5194/egusphere-egu24-17192, 2024.

[2] E. Malegiannaki, P. Bohleber, D. Zannoni, C. Stremtan, A. Petteni, B. Stenni, C. Barbante, B.M. Vinther, V. Gkinis, Towards high-resolution water isotope analysis in ice cores using laser ablation - cavity ring-down spectroscopy, Anal. (2024) 5843–5855. https://doi.org/10.1039/d4an01054j.

How to cite: Stremtan, C., Wožniak, J., Pușcaș, M., and Hofmann, M.: Spatially resolved δ13C measurements of solid samples via Laser Ablation Cavity Ringdown Spectroscopy (LA CRDS) – a new tool for environmental research, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14870, https://doi.org/10.5194/egusphere-egu25-14870, 2025.

Predicting the physiological responses of tree species under future hydroclimate scenarios is essential for understanding and mitigating the impacts of anthropogenic climate change. Here, we present our work on reconstructing the intraseasonal physiological responses of one of the longest living tree species on Earth – Great Basin bristlecone pine (Pinus longaeva, Pinaceae). This species is infamous for its tree ring chronologies that can extend beyond 5,000 years, yet the key physiological traits that will determine its ability to tolerate warmer, drier conditions in the future remain to be characterized. Moreover, the extent to which localized changes in topoclimate and seasonal water availability will impact overall growth performance and survival is also uncertain. To address this, we collected needle samples from trees along an elevation gradient near Great Basin National Park, NV, USA. Using the unique phyllotaxy of this species, we isolated annual needle samples corresponding to five distinct growth years (2018 – 2022). We then developed a novel method for quantifying intraseasonal variation in carbon isotope discrimination and intrinsic water use efficiency by using fine-scale, sequential measurements of needle δ¹³C in-situ via laser ablation isotope ratio mass spectrometry. We obtained an average of 25 individual δ¹³C measurements along the lengths of each needle sample, which were all consistent with whole-needle δ¹³C values measured via traditional elemental analyzer isotope ratio mass spectrometry. However, these sequential δ¹³C values varied in excess of 1 ‰ (VPDB) along the lengths of each needle sample, likely reflecting intraseasonal changes in water availability through the time in which individual needles were being constructed. Paired with our previous measurements of annual ring width, stomatal density, and needle length from trees at this site, we discuss how this new method provides a more comprehensive understanding of the role of intraseasonal variation in water availability on the overall physiological performance of this species in the past as well as under future hydroclimate scenarios.

How to cite: Weitz, A., Puscas, C. M., Stremtan, C. C., Salerno, A., and Bunn, A.: High-resolution insights into the seasonal physiological responses of Great Basin bristlecone pine (Pinus longaeva) through in-situ δ13C LA-IRMS, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15848, https://doi.org/10.5194/egusphere-egu25-15848, 2025.

Laser spectroscopy-based gas isotope analysers (LSIA) are cheaper in acquisition and maintenance but still lack the accuracy and precision available through isotope ratio mass spectrometry (IRMS). One of the applications where LSIA are particularly advantageous are online measurements that follow gas release over time. This is even more the case in labelling experiments, where requirements regarding isotope ratio precision are lower. Yet, experiments that implement such setups remain relatively rare.

Here, we present a simple, low-cost setup that conducts automated isotope ratio measurements in gases released from various materials. The setup consists of a LSIA instrument (Picarro G2201-i or G5131-i) which is connected to up to 16 measurement chambers using a VICI selector valve actuated by a Raspberry Pi which also records the measurement data and valve position. An auxiliary pump equipped with a needle valve is placed in parallel to the LSIA to regulate the total flow rate to 500 mL min^-1. Each chamber is connected to the analyser for 10 minutes, before switching to the next chamber. We therefore allow the target gas (CO₂, CH₄, or N₂O) to accumulate over 150 minutes between measurements in each chamber. During the measurement, chamber air is pulled to the analyser and replaced by ambient air. The analyte concentration therefore decreases during the measurement time, which allows us to calculate the source isotope value through the Keeling plot method. At the end of the measurement, the analyte concentration and isotope ratio is near ambient air, such that the chamber is reset for the next cycle.

We present and compare three different experiments that used this approach. First, we studied phloem transport rates in Beech trees. For this, we pulse-labelled branches with ¹³CO₂ and followed the release of ¹³CO₂ from stem respiration at different heights over time. Second, we studied the conversion of ¹³C-acetate label injected into intact peat cores into CO₂ and CH₄. We quantified the fractions of label recovered as CO₂ and CH₄ as well as the timing of label-derived gas emissions as a function of injection depths. Finally, we adjusted this setup for measurements of natural abundance isotope ratios in soil N₂O emissions to study N₂O source processes from permafrost soils. Our presentation will compare these implementations and report on the experience gained during their setup.

How to cite: Kohl, L., Koskinen, M., Polvinen, T., Salmon, Y., Biasi, C., Pihlatie, M., Laurén, A., Zhuang, X., Paljakka, T., and Znamínko, M.: A simple setup for online laser spectroscopy gas isotope analysers in online chamber systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18101, https://doi.org/10.5194/egusphere-egu25-18101, 2025.

Marine ecosystems play a critical role in global photosynthetic carbon fixation, with approximately 5.36 Pg C exported annually via the biological pump. Macroalgae alone sequester around 200 million tons of CO₂ annually, though these estimations are largely based on indirect calculations. Hydrogen isotope (δ²H) analyses offer a promising avenue to refine such estimates while advancing our understanding of macroalgal carbon and energy metabolism.

Stable isotope studies have been instrumental in ecological and biogeochemical research, yet the application of δ²H analyses to marine algae remains limited. Most prior studies have focused on salinity-driven δ²H variations in algae, overlooking the potential of δ²H to reveal key biochemical processes. Recent findings suggest that δ²H values of organic molecules are significantly influenced by biosynthetic fractionation (²H-ε_bio), governed by the interplay between photosynthetic (²H-ε_λ) and post-photosynthetic (²H-ε_Η) processes. This metabolic signal, previously observed in terrestrial plants, is strongly modulated by the photosynthetic carbohydrate supply rate, impacting δ²H variability in organic compounds.

The giant kelp Macrocystis pyrifera provides an ideal model system to investigate these processes in marine environments. Unlike terrestrial plants, M. pyrifera offers a simplified isotopic system due to: (i) access to water with stable δ²H values, (ii) exclusion of evaporative ²H-fractionation, and (iii) a primitive vascular system that minimizes isotopic exchange across its structure. These unique features allow us to isolate and examine the variability of ²H-ε_λ under different light conditions, shedding light on the metabolic processes underlying δ²H variability in marine photoautotrophs.

This study highlights the potential of δ²H analyses to bridge the gap between isotopic and biochemical research in marine systems. By focusing on M. pyrifera, we aim to provide critical insights into the drivers of δ²H variability and their broader implications for understanding marine carbon dynamics and the role of macroalgae in global biogeochemical cycles. This work lays the groundwork for advancing isotopic methodologies and applying them to ecological and palaeoenvironmental studies in marine ecosystems.

How to cite: Cormier, M.-A., Steller, D., Salik, M. A., Lehmann, M., Al Sid Cheikh, M., and Gagnon, P.: Unravelling Hydrogen Isotope Fractionation in Marine Macroalgae: Insights from Macrocystis pyrifera, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18571, https://doi.org/10.5194/egusphere-egu25-18571, 2025.

The composition of heavy and light carbon isotopes in tree rings is influenced by the water supply during the time the tree ring was formed due to stomata opening and therefore the ability of the tree to favor lighter isotopes, since the absorbed carbon is used for tree ring formation. This allows calculating the Intrinsic Water Use Efficiency (iWUE) as an indicator for drought stress. With about 1400 samples (tree-rings) from 15 trees from Southwestern Germany, with three individual trees of European beech, Sessile oak, Norway spruce, Scots pine and Douglas Fir respectively, we created cross-dated time series Delta13C isotope ratio and annual growth (using ring width). Our sites included both good and bad site conditions. We linked our data with climate time series for the study area as independent variables. The variety of variables allowed us to determine, to what extent independent factors influence growth and iWUE as well as interactions between the individual factors and their cumulative effects. Statistical methods and time series analyses were used to quantify the complex relationships between water availability, competitive pressure, climatic conditions, and tree growth. This approach combines various fields of terrestrial ecosystem research on individual plant level.

First results show diverse reactions to drought depending on species and location. We found growth and iWUE to be highly dependent on the climate for all species, whereas correlations between these variables imply a tree´s strategy to cope with drought conditions. The correlations differ between individual trees of the same species meaning that location may play a greater role in its significance than previously assumed, conditional on the species. Further investigations could support hydrologically focused forest management with respect to understanding the impacts of climate change on forest ecosystems.

Therefore, an upscaling approach would allow for the depiction of iWUE on catchment level. By reconstructing past environmental conditions based on tree rings, valuable information can be obtained, contributing to the development of strategies for adapting forest stands to future climate conditions. For a deeper understanding and practical conclusions, the neighborhood relationships and competition should be quantified over the entire lifetime of an analyzed tree, since not all irregularities in isotope composition were captured.

How to cite: Keutner, P., Neumann, M., and Müller, E.-V.: Combining carbon isotopes with tree ring analysis – insights into water use efficiency and drought stress , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18733, https://doi.org/10.5194/egusphere-egu25-18733, 2025.

The Laacher See (Lake Laach), the largest volcanic lake in Germany, resulted from a massive phreatomagmatic eruption in the Eifel Region ~13,000 years ago. The enclosed lake within a small catchment is still affected by the underlying volcanic activity, providing a unique natural laboratory for investigating the sources and sinks of high dissolved carbon concentrations and associated element cycles in natural chemical gradients. The lake is continuously affected by magmatic CO₂ degassing. A large number of moffettes are distributed not only along the lake shore but also at different depths of the lake, whereby gas seeps can still be found at the deepest point of the lake at 51 m. Here, seasonal investigations of the water column and porewaters from several sediment short cores and a 6 m long core at a reference site show for the first time that the sediment package is an active and special biogeochemical reactor outlining a unique type of diagenesis under the boundary conditions of high dissolved inorganic carbon. With the help of an underwater drone equipped with a temperature & depth sensor, the water column was accurately sampled at regular depth intervals. Additionally, the fingerprinting of surrounding groundwaters as potential water and elemental sources, allows for a first assessment of the cycling of dissolved carbon, water, major and trace elements. Stable H and O isotope signatures provide insight into the water sources and the seasonal water balance of the lake. The C isotopic composition of dissolved inorganic carbon (DIC) indicates its sources and fate, and explains signatures reported for authigenic sedimentary carbonates, e.g. siderite. Sulfate is consumed by microbial sulfate reduction in the upper few centimeters of the sediments, and the SO₄ isotopic signature from the lake water is close to that of the moffette solution indicating similar influence of these benthic processes. The examination of porewaters from a ca. 7-meter-wide pockmark provides evidence of enhanced diagenesis under high DIC fluxes potentially affecting metal accumulation and liberation from sediments.

How to cite: Roeser, P., Jentsch, A., Albers, S., Knornschild, N., Heumann, G., de Batist, M., Brehme, M., März, C., and Böttcher, M.: Sources and sinks of water and elements in the high-CO2 volcanic Laacher See, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18841, https://doi.org/10.5194/egusphere-egu25-18841, 2025.

Conventional isotope applications in plant ecophysiology measure isotope ratios (e.g. δ²H, δ¹³C) of whole molecules. However, it is well established that isotope abundance varies AMONG the CH groups of metabolites (isotopomers), because they are biochemically distinct. This variation reflects enzyme isotope fractionations and encodes metabolic information, but it is unclear how these fractionations get transferred into signals that can be recovered from archives of plant material.

Here, we will describe physical and biochemical mechanisms of hydrogen isotope fractionation in plants and compare their magnitudes. Based on observations for hydrogen isotope transfer in plants, we present a model for the extraction of H isotope signals from plant archives.

Plant responses to increasing CO₂ are critical for plant productivity and as climate feedbacks. As CO₂ is the substrate for photosynthesis, plants should benefit from increasing CO₂, but the magnitude of this “CO₂ fertilization” disagrees with biomass estimates. Photorespiration is a side reaction of photosynthesis that reduces C assimilation in most vegetation, therefore its response under climate change is critical for the future C cycle. Photorespiration should be reduced by increasing CO₂ yet exacerbated by rising T, but its response is not well captured in models, adding large uncertainty to C cycle predictions.

To retrieve ecophysiological signals from plant archives, we use manipulation experiments to develop proxies for plant C fluxes, based on intramolecular abundance variation of ²H and ¹³C, detected by NMR. We then retrieve these proxies from archives such as tree-ring series, to derive metabolic responses over long time scales, and to improve global vegetation models.

Here we will describe progress in tracking isotopomer signals from controlled experiments to plant archives, and results on long-term trends of photorespiration in response to increasing atmospheric CO₂ for two globally important ecosystems. In Sphagnum species, we link trends in photorespiration to the C sink of boreal peatlands. In the tropical tree species Toona ciliata, we describe long-term trends in photosynthetic efficiency.

As intrinsic quantities, isotope data are well suited to report on metabolic shifts, but not about fluxes in absolute numbers. Therefore we use isotopomer data as input for the LPJ-GUESS Ecosystem Model, to translate isotopomer-derived changes in photorespiration into trends in ecosystem C fluxes.

References:

Augusti A. et al (2008) Chem. Geol. 252, 1-8, doi 10.1016/j.chemgeo.2008.01.011

Ehlers I. et al (2015) PNAS 112, 15585-15590 doi 10.1073/pnas.1504493112

Walker AP. et al (2021) New Phytol 229, 2413-2445 doi 10.1111/nph.16866

Serk H. et al (2021) Scientific Reports 11, 24517 doi 10.1038/s41598-021-02953-1

Zwartsenberg SA. et al (2025) New Phytol in press.

How to cite: Schleucher, J., Haddad, L., Yin, X., Zuidema, P., Zwartsenberg, S., Öquist, M., Marshall, J., and Smith, B.: Plants in changing climate: Linking isotope effects, manipulation experiments, plant archives and modelling to derive long-term ecophysiogical signals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19505, https://doi.org/10.5194/egusphere-egu25-19505, 2025.

The western Black Sea Shelf where the Danube is discharging into the Black Sea is especially sensitive to river-induced eutrophication, which peaked in the 1980s and 1990s due to human-induced nutrient input and is decreasing since the mid-1990s due to ongoing mitigation measures. The scarcity of information on Danube nutrient loads prior to the 1960s complicates the assessment of earlier nutrient input and thus to define pristine conditions to provide a reference for nutrient reduction goals. In this study, we aimed to trace modern and historical nitrogen sources to the western Black Sea Shelf during the last ~5,000 years with special focus on the past 100 years, using sedimentary records of TOC, TIC, nitrogen, and δ15N.

Our results demonstrate that the balance of riverine nitrogen discharge into the Black Sea on the one hand, and nitrogen fixation in the pelagic on the other hand is generally determined by climate effects. Specifically, this balance of riverine N input and N fixation is not only controlled by the amount of nutrients discharged by rivers, but also by the freshwater itself, which controls the intensity of thermohaline stratification and thereby the intensity of nutrient recycling from the deep basin back into the euphotic epipelagic. Our results show a gradient from the nearshore sediment directly at the Danube Delta, where riverine N is dominant to offshore sediment in 80 m water depth, where pelagic N fixation was dominant in the past. Our results based on stable isotopes also demonstrate the increased deposition of nitrogen from human activities in all stations across the shelf and the concomitant changes in deposition rates of organic matter as indication for perturbations in the epipelagic community due to the human-induced eutrophication. Finally, our stable isotope data indicate that human-induced eutrophication can be traced back to the 12^th century AD, which raises the question which point in time is a feasible reference for nutrient reduction goals as the Danube was not pristine since at least 800 years.

How to cite: Neumann, A., Dähnke, K., and Sanders, T.: Reconstructing changes in nitrogen input to the Danube-influenced Black Sea Shelf during the Holocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19649, https://doi.org/10.5194/egusphere-egu25-19649, 2025.

Iron-manganese (oxy)hydroxide precipitates (Fe-Mn concretions) occur at the ocean and sea floors all over the world, typically in regions with low sedimentation rates. In shallow water environments like the Baltic Sea, Fe-Mn concretions form in areas where bottom currents prevent active sediment accumulation. The shallow brackish conditions and periodical saltwater inflows from the North Sea make the Baltic Sea a unique environment for concretion formation. Fe-Mn concretions in the Baltic Sea also grow much faster than oceanic concretions, resulting in different mineralogical, chemical, and isotopic compositions compared to deep-sea nodules. One of the areas in the Baltic Sea where Fe-Mn concretions are widespread is the Gulf of Finland, where the concretions form where Late Pleistocene glaciolacustrine varved clays, glacial till, or crystalline bedrock is exposed on the seafloor. 

Due to redox-driven precipitation processes, the spherical or disc-like Fe-Mn concretions forming symmetrically around a nucleus are composed of alternating Fe- and Mn-rich layers. In addition, crust-like concretions can grow in areas with higher background sedimentation rates. During their formation, Fe-Mn concretions record the geochemical status of the sedimentary environment, making them potential archives of the geological history of sedimentary basins. Following the Last Glacial Maximum, the Baltic Sea basin has been through multiple phases of fresh and saltwater conditions before the establishment of the modern brackish Baltic Sea. The Fe-Mn concretions in the Baltic Sea have potentially recorded those changes in their chemical and stable isotopic composition, helping us to understand their formation mechanisms and growth phases through layer-by-layer sampling of the concretions from the centre outwards. 

This study examines the morphological, chemical, stable isotopic and mineralogical properties of the Fe-Mn concretions in the Baltic Sea, Gulf of Finland seafloor and has an overarching aim to assess the complex geological processes controlling the formation of concretions, as well as get a closer look at the growing phases through the finer sampling of their layered structure, which could offer a new perspective on the timing of formation of these concretions relative to the development of the Baltic sea and the Gulf of Finland.

How to cite: Ojap, J. M., Liira, M., Lepland, A., Böttcher, M. E., Suuroja, S., Somelar, P., and Kirsimäe, K.: Insights into the genesis and geological significance of iron-manganese precipitates in the Baltic Sea, Gulf of Finland seafloor, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19711, https://doi.org/10.5194/egusphere-egu25-19711, 2025.

High-resolution records of centennial climate variability are crucial considering the scarcity and overall short length of instrumental meteorological data in many regions of the world. The application of stable isotopic analysis in tree rings has emerged as a robust methodological tool for elucidating the intricate complexities of environmental history. This presentation will travel from high latitudes in North America to the Tropical Andes in South America to show how tree-ring stable isotopes can be used to reconstruct climate variability and atmospheric patterns across the Americas, as well as changes in Sea Surface Temperatures (SST). Stable oxygen isotopes (δ¹⁸O) measured in tree rings from white spruce trees from the Northwest Territories of Canada record similar large-scale climate patterns as modelled precipitation δ¹⁸O from a general circulation model (NASA GISS ModelE2 isotopically-equipped). Trees from the species Polylepis tarapacana growing at high elevation (~5,000 m a.s.l) at the South American Altiplano were used to reconstruct annual precipitation variability, which is driven by the South American Summer Monsoon, over the last 300 years. This newly developed tree-ring δ¹⁸O chronology revealed a robust hydroclimatic teleconnection showing interannual (2–5 years) and decadal (~11 years) periodicities consistent with records of Altiplano precipitation, central tropical Pacific SST, Andean ice core δ¹⁸O and tropical Pacific coral δ¹⁸O. Furthermore, new tree species of the genus Polyelpis growing in the inner tropics were discovered and found to have significant sensitivity to local and regional hydroclimate variability, showing a close link to tropical Pacific SST and El Niño–Southern Oscillation. Overall, our findings point out the importance of developing longer stable isotopes tree-ring records to overcome the inherent difficulties to reconstruct global hydroclimate variability.

How to cite: Andreu-Hayles, L., Rodríguez-Morata, C., Rodriguez-Caton, M., Boucher, E., Christie, D. A., Crispín-DelaCruz, D. B., D'Arrigo, R., Daux, V., Ferrero, E., Field, R. D., Gennaretti, F., Hermoso, I., Lavergne, A., Morales, M., Oelker, R., Requena, E. J., Ticse-Otarola, G., Varuolo-Clarke, A. M., Villalba, R., and Vuille, M.: Revealing past climate variability using tree rings and stable isotopes from tropical and boreal regions in the Americas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19720, https://doi.org/10.5194/egusphere-egu25-19720, 2025.

How to cite: Znamínko, M., Kohl, L., Trubnikova, T., Bahn, M., and Biasi, C.:  Isotopic composition of N2O emissions from a permafrost peatland: a laboratory study using three different analytical techniques  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19824, https://doi.org/10.5194/egusphere-egu25-19824, 2025.

Accumulation of carbon and nitrogen in freshwater wetlands is affected by climatic change. Elevated temperatures and changes in precipitation patterns may lead to degradation and thinning of peat deposits resulting from higher rates of biogenic emissions of greenhouse gases. Higher atmospheric concentrations of greenhouse gases, mainly CO₂, CH₄, and N₂O, may then accelerate global warming. A number of recent studies have addressed the relationship between increasing deposition of reactive nitrogen (N_r, predominantly ammonium and nitrate)and stability of the N stock in peat. Under high atmospheric N_r inputs, peatlands may become a net source of N, rather than a net sink. Nitrogen inventories in ombrotrophic bogs may be influenced by biological N₂-fixation (BNF), the conversion of atmospheric molecular N₂ by diazotrophic microorganisms to bioavailable NH₄⁺. Because a high energy is required to break the triple bond in the N₂ molecule, microbial N₂-fixation may shut off when other N_r sources are available. To verify this assumption, we studied four Sphagnum-dominated peat bogs in the Czech Republic differing in N_r deposition by a factor of two. We hypothesized that the more N_r-polluted sites in the north, Velke jerabi jezero (VJ) and Cerny potok (CP), would exhibit lower BNF rates than the less polluted sites in the south, Cervene blato (CB) and Zdarecka slat (ZS). At the end of laboratory incubations of waterlogged peat in a ¹⁵N₂ atmosphere (t = 2-7 days), samples of living Sphagnum exhibited an increase in d¹⁵N values from about -3 ‰ typical of all sites to 27, 259, and 266 ‰ at VJ, CP and ZS, respectively. No significant change in d¹⁵N values was recorded at CB. At VJ, the estimated BNF rates reached 840 ng N per gram Sphagnum per day. At CP and ZS these rates were about 10 times higher. Microbial analysis revealed higher activity of diazotrophs at VJ than at CB. At VJ, autotrophic cyanobacterial diazotrophs of the Nosctocaceae family comprised 4.2 %, while at CB they were below 0.1 %. Repeated sampling at CP and ZS in spring and summer showed complex temporal trends in d¹⁵N shifts during ¹⁵N₂ moss incubations. At CP, the d¹⁵N shift and BNF rates were larger in summer, whereas at ZS, a larger d¹⁵N shift and higher BNF rates were observed in spring. Vertical trends in d¹⁵N values at the end of the ¹⁵N₂ incubations were also complicated. Out of four peat sampling depths (0, 10, 20 and 30 cm), the highest positive d¹⁵N shifts during incubation experiments were found 20 cm below surface at CP (561 ‰; spring) and 10 cm below surface at ZS (805 ‰; summer). Collectively, our data indicate that atmospheric N_r inputs were not the main control of BNF in the studied Central European peat bogs. Also large within-site and seasonal variability in BNF was observed. Other site characteristics, such as phosphorus availability, NH₄⁺/NO₃^- ratios, and moisture conditions served as important BNF drivers.

How to cite: Novak, M., Cejkova, B., Barta, J., Santruckova, H., Jackova, I., Stepanova, M., Buzek, F., Curik, J., and Veselovsky, F.: Biological nitrogen fixation at four Sphagnum-dominated peatlands in the Bohemian Massif: Spatial and temporal variability based on 15N2 moss incubation experiments and microbial community analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20120, https://doi.org/10.5194/egusphere-egu25-20120, 2025.

Nitrous oxide (N₂O) is a potent greenhouse gas and a significant contributor to global warming and ozone layer depletion. It is primarily emitted from soils through microbial processes such as nitrification and denitrification and shows spatial and temporal variations driven by environmental factors such as the availability of nitrogen (e.g., in the form of fertilizers), organic carbon, soil moisture, temperature and oxygen levels. However, estimates on the relative contribution of different N₂O producing pathways are frequently uncertain and knowledge on how environmental factors influence N₂O emissions dynamics is still limited. Therefore, closing these knowledge gaps is crucial for improving mitigation strategies.

This study aims to analyze the patterns of N₂O emissions across diverse forest and agricultural soils, taking geographic variations into account, and to determine the relative contributions of the primary N₂O producing and consuming pathways specific to each soil type.

Batch experiments were conducted using four agricultural soils and four forest soils from sites of the ICOS (https://www.icos-cp.eu) and FLUXNET (https://fluxnet.org/about/) networks. Agricultural soils were obtained in France, Belgium, Italy and Switzerland, while forest soils were obtained in Finland, Sweden, Belgium and Italy. These soils exhibited a range of intrinsic characteristics, such as texture, organic matter content and type, and nitrogen sources. The incubations took place in complete darkness at a constant temperature of 22 ºC for approximately 30 hours after rewetting dry soil. Each soil type was tested with five replicates across five time points (i.e., 25 reactors for soil type). For each reactor we measured the production of N₂O and its isotopic composition including the δ¹⁵N-N₂O_bulk, δ¹⁸O-N₂O_bulk, and site preference δ¹⁵N-N₂O_SP (i.e., the intramolecular distribution of N isotopes, since the N₂O molecule has an asymmetric linear structure [N-N-O]). Additionally, the isotopic compositions of nitrate and ammonium from soil KCl extracts are being analyzed (δ¹⁵N-NO₃^-, δ¹⁸O-NO₃^-, δ¹⁵N-NH₄⁺) and microbiological characterization is also being performed.

Preliminary results revealed significantly higher N₂O production in agricultural soils compared to forest soils during the 30-hour incubation period, with rates reaching up to 130 μg N-N₂O/kg/h in agricultural soils and only 0.3 μg N-N₂O/kg/h in forest soils. Notable differences were also observed among the four tested soils within each category (agricultural or forest). These differences might be mainly attributed to differences in the nitrogen and organic carbon content as well as the texture. The isotopic analysis of N₂O suggests that denitrification is the primary process driving N₂O emissions in the studied soils, with nitrification also contributing to varying extents depending on the soil type.

Ongoing isotopic analyses of nitrate and ammonium in soil KCl extracts alongside microbial characterization, will provide deeper insights into the dominant processes driving N₂O emissions in each soil type and the key environmental factors influencing them.

How to cite: Margalef-Marti, R., Mattana, S., López-Sánchez, C., Carrey, R., Palau, J., Otero, N., Tallec, T., Heinesch, B., Feigenwinter, I., Turco, F., Rautakoski, H., Lohila, A., Peichl, M., Guerreri, R., Jansens, I., Poblador, S., Magliulio, E., Vitale, L., Lewicka-Szczebak, D., and Ribas, A.: Unraveling N2O production pathways in agricultural and forest soils using stable isotope analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20270, https://doi.org/10.5194/egusphere-egu25-20270, 2025.

Mountain grasslands are currently experiencing significant changes in land use and climate, with an increased frequency of extreme droughts anticipated in the near future. Understanding the drought responses of carbon (C) allocation—a critical process in the C cycle—remains limited. In this study, we conducted an experimental summer drought on traditionally managed hay meadows and traced the fate of recent assimilates into leaf and root sucrose. We applied ¹³CO₂ pulses at peak drought and tracked the labeled carbon into individual positions of glucose using liquid chromatography coupled with ultrahigh-resolution mass spectrometry.

Our findings revealed that drought conditions decreased total C uptake and led to a reduction in above-ground carbohydrate storage pools. The turnover of the leaf sugar pool, determined through position-specific carbon enrichment, was significantly reduced compared to the control treatment. Interestingly, below-ground C allocation to root sucrose was enhanced by drought, but the position-specific carbon enrichment was less affected, suggesting the involvement of other carbon sources.

These results demonstrate that position-specific isotope distribution provides a novel understanding of plant carbon allocation, offering new insights into the resilience and adaptation of mountain grasslands to drought stress.

How to cite: Gleixner, G.: Unveiling Carbon Allocation Dynamics in Mountain Grasslands Under Drought Stress Using Position-Specific Isotope Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20366, https://doi.org/10.5194/egusphere-egu25-20366, 2025.

d²⁶Mg values and ⁸⁷Sr/⁸⁶Sr ratios are used as tracers of calcite and dolomite formation in the late Miocene Lake Bira. Mg and Sr isotope ratios were analyzed in freshwaters and brines that currently feed the Sea of Galilee (the modern remnant of Lake Bira) and in limestones and dolostones comprising the Bira Formation. d²⁶Mg and ⁸⁷Sr/⁸⁶Sr ratios of the Sea of Galilee waters (~0.89‰, ~0.7075) are consistent with the mixing of mainly carbonate and basaltic waters with subsurface Ca-chloride brines (e.g., Tiberias Spa). The d²⁶Mg values in the limestones and dolostone of the Bira Formation range from ~ -1.0 to ~ -3.5‰. and -2.8 to -1.8 ‰, respectively. The d²⁶Mg values in Lake Bira waters at that time were between ~-2 ‰ to ~1 ‰, as calculated from the fractionation factors between water and either calcite or dolomite (-2 ‰ and -0.75 ‰, respectively). Isotope mixing calculations suggest that waters with positive d²⁶Mg values (estimated as ~1.2 ‰) were added to the lake. We suggest that these waters were Ca-chloride brines that were formed in the late Miocene Jordan Valley by interaction between evaporated seawater and the local limestones. These brines deposited the contemporaneous thick sequences of salt (halite) and gypsum in the Jordan Valley to the east of the lake. Dolomitization of the limestones increased the d²⁶Mg of the brines during their re-circulation through the surrounding aquifers due to Rayleigh fractionation, The dolomitization process was accompanied by the production of a Ca-chloride solution.

Limestone formation required enhanced freshwater input; a process accompanied by increasing hydrological head that induced an enhanced inflow of the Ca-chloride brine with high d²⁶Mg to the lake. Dolomite formation was associated with the weakening of the hydrological head, and diminishing flow of the brine to the lake.

The formation of dolomites in the lacustrine environment of Lake Bira and the contemporaneous deposition of gypsum in the nearby Jordan Valley provides a model for dolomitization in marginal environments (e.g., lagoons and subkhas), where the Mg is exchanging with Ca during the dolomitization process and the excess Ca taking the sulfate to form gypsum.

How to cite: Lazar, B., Halicz, L., Karasiński, J., Shaked Gelband, D., Starinsky, A., and Stein, M.: Environmental conditions for dolomite formation in the Late Miocene Lake Bira – Clues from Mg and Sr isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20485, https://doi.org/10.5194/egusphere-egu25-20485, 2025.

Quantitative provenance analysis studies are instrumental in understanding the tectonic and climatic processes that are shaping Earth`s landscape. Although the most abundant mineral in the sedimentary system is quartz, almost all studies in provenance analysis investigate accessory minerals. Quartz contains various defects, intrinsic (mainly O related defects) or due to impurities. Some of these defects remain unchanged under ionizing radiation exposure while others are being transformed. Some of these defects are paramagnetic (e.g.  E’, an unpaired electron at an oxygen vacancy site (≡Si·), peroxy intrinsic defect centers (≡Si-O-O⋅), nonbridging oxygen NBOHC, (≡Si–O⋅), Al related paramagnetic defects such as Al-hole, [AlO₄]⁰, titanium impurity defects such as [TiO₄/M⁺]⁰ where M⁺ is a cation, germanium defects ([GeO₄]⁰, [GeO₄/ M⁺] etc.) while others have the ability to emit light upon stimulation and were identified and characterised by techniques such as photoluminescence or cathodoluminescence (nonbridging oxygen, NBOHC, ≡Si–O⋅, oxygen deficiency center, ODC,  ≡Si-Si≡ etc.).  Based on the dynamics of radiation sensitive defects under irradiation, quartz can record the amount of ionizing radiation it has been exposed to since a resetting event. As such, quartz is successfully used for dating materials by thermoluminescence (TL) or optically stimulated luminescence (OSL) as well as by electron spin paramagnetic (EPR). Here we present multi-spectroscopic investigations (TL, OSL, EPR as well as hyperspectral resolved cathodoluminescence based on scanning electron microscopy) on quartz grains extracted from independently dated old to young quartz-bearing continental crustal sources, metamorphosed rocks versus their unmetamorphosed equivalents, as well as intrusive versus volcanic rocks and their derived sediments throughout the world. These investigations aim to prove that point defects in quartz have the capacity to carry genetic information and their modifications can provide evidence for antiquity, metamorphism (or lack thereof) as well as knowledge on transport, or recycling.

How to cite: Timar-Gabor, A.: Towards reading provenance from ubiquitous quartz by multi-spectroscopic investigations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-451, https://doi.org/10.5194/egusphere-egu25-451, 2025.

The toxicity of arsenic and its detrimental impact on human health have driven extensive research into effective removal methods (Smedley and Kinniburgh, 2002). Arsenate AsO₄^3- can be efficiently sequestered from aqueous solutions by inducing the precipitation of mimetite (Pb₅(AsO₄)₃Cl), a stable and sparingly soluble phase with an apatite-like structure (Magalhães & Silva, 2003; Bajda et al., 2007; Bajda, 2010). This study introduces a novel application of lead-modified zeolite for arsenate removal, leveraging mimetite precipitation for efficient and environmentally sustainable water treatment. Pb bound to the zeolite surface exhibits optimal binding strength: strong enough to prevent the release of lead into water, yet weak enough to facilitate its reaction with arsenate and chloride ions present in solution.

This reaction led to the precipitation of mimetite directly on the surface of zeolite aggregates, ensuring efficient arsenic removal:

5Pb²⁺_{desorbed from zeolite} + 3AsO₄^3-_{contamination} + Cl^-_{supplied extra} = Pb₅(AsO₄)₃Cl _{precipitated on zeolite}

The source of lead was a lead-modified natural clinoptilolite (ZEOCEM, Bystré, Slovak Republic), originally in its Ca form but transformed to Na-clinoptilolite after a 24-hour reaction in 2 M NaCl solution. This sodium form of clinoptilolite was then prepared by sorption of Pb²⁺ from solution, followed by intensive washing to remove excess Pb and desorption of loosely bound ions. 800 mg of Na-clinoptilolite was reacted with 40 mL of solution containing 4000 mg Pb/L at pH 4 for 24 hours, followed by washing with redistilled water and centrifugation (seven times) until Pb was below the detection limit of the Atomic Absorption Spectroscopy (AAS) method. The Pb-modified zeolite thus obtained, containing about 70 g of bound Pb per kg of zeolite, was subsequently reacted with arsenate solutions (500 mg of Pb-zeolite in 40 mL of solution containing 50 mg As(V)/L) in the presence of chloride ions (20 mg Cl/L) at pH 2 and 7 for up to 7 days.

At pH 7, arsenate levels decreased below the detection limit within 24 hours, while at pH 2, 95% of arsenate was removed. X–Ray Powder Diffraction (XRPD) and Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS) analyses confirmed the formation of mimetite, which precipitated on the zeolite aggregates, forming incrustations of distinct needle-like crystals up to 2 μm in length. Induced precipitation of mimetite produces a highly stable crystalline product, suggesting its potential for effective arsenate sequestration. This approach, with further testing in complex systems, holds significant promise for scalable and cost-effective arsenate remediation in contaminated waters.

References:

Bajda, T., Szmit, E., & Manecki, M. "Removal of As (V) from solutions by precipitation of mimetite Pb₅(AsO₄)₃Cl." Environmental Engineering, (2007): 119-124.

Bajda, T. “Solubility of mimetite Pb₅(AsO₄)₃Cl at 5–55 C.” Environmental Chemistry 7(3) (2010): 268-278

Magalhães, M. C. F., and Silva, M. C. M. „Stability of lead (II) arsenates.” Monatshefte fuer Chemie/Chemical Monthly, 134, (2003):735-743.

Smedley, P. L., and Kinniburgh, D.G. "A review of the source, behaviour and distribution of arsenic in natural waters." Applied geochemistry 17.5 (2002): 517-568.

How to cite: Stępień, E., Manecki, M., and Bajda, T.: Lead-modified zeolite for arsenate removal via mimetite (Pb5(AsO4)3Cl) precipitation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-895, https://doi.org/10.5194/egusphere-egu25-895, 2025.

The presence of pollutant dyes in water bodies poses a significant concern that adversely impacts both human health and environmental integrity. Numerous methodologies and materials exist for the extraction of these contaminants from aqueous solutions and their subsequent utilization. Adsorption processes utilizing zeolite minerals and various modified forms are frequently employed.

The unmodified forms of zeolite minerals are inadequate for dye removal from aqueous solutions; consequently, the properties of zeolite can be enhanced through the application of various surfactants. Nevertheless, the organic surfactants utilized in enhancing zeolite efficacy are also contaminants, and further research is being conducted to eliminate these pollutants from aqueous environments. Furthermore, only organic surfactants and a limited number of distinct active substances have been utilized to enhance the dye removal efficacy of zeolites. While zeolite minerals modified with inorganic active substances such as NaCl, Na2CO3 and Na2SO4 have been utilized in various applications, the dye removal efficacy of zeolites modified with these inorganic salts has not been previously investigated.