Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 2
Efficient handling of climate change issues in order to mitigate its negative impact of the flora and fauna of the earth, or on the pace of industrialization, is a big challenge in every disposition around the world. Amongst the many options available, geological storage of CO2 in the basalt formations is proving to be a promising one due to its large and pervasive occurrence, to facilitate stable carbonation of the sequestered CO2, and with ready access to the basalt deposits for operational requirements. Laboratory testing and a few field implementations showed that carbon dioxide injected in basalts would form stable carbonate minerals, keeping the substance in place for thousands of years.
This work applies the machine learning applications aimed at the classification of different facies in basalts, particularly flow tops and flow interiors, towards the selection of a sequestration site based on their relevant petrophysical characteristics.
After the facies were identified, several rock physics models were run with an outlook of predicting the elastic properties of basalt. Based on our results, we found the Differential Effective Medium (DEM) model enables the most accurate prediction with the least error as compared to Self-Consistent Approximation and Kuster-Toksӧz model. This finding provides a foundation for using the DEM model to create an initial reservoir matrix, which can be applied to simulate geomechanical changes upon CO2 injection in Basalt. Additionally, facies classification aids in delineating zone boundaries within basalt flows, allowing for the selection of optimal injection sites based on their petrophysical properties.
How to cite: Nagarkoti, N., Kumar, T., Panwar, N., and Sharma, R.: Determination of Lithofacies and Elastic Behavior Modeling in Columbian River Basalt Group (CRBG) Formations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17658, https://doi.org/10.5194/egusphere-egu25-17658, 2025.
Electrical image logs can intuitively reflect the development status and characteristics of dissolution pores, which is of significant importance for the development of oil and gas resources. However, traditional methods for identifying pores in electrical image logs are not only cumbersome and labor-intensive but also incapable of distinguishing between different types of pores. Moreover, the strong heterogeneity and dissolution effects in carbonate reservoirs result in significant variations in pore size and complex, diverse pore morphologies, making it difficult to extract pore parameters. To address these issues and challenges, this paper proposes a semantic segmentation model, FILnet, designed using computer vision technology and deep learning frameworks. This model aims to achieve intelligent recognition and segmentation annotation of pores of different scales in the wellbore region of electrical image logs. The data selection process involved using a sliding window to choose electrical log images containing dissolution pores and caves. Image processing techniques were then applied to complete and augment the images, thereby enhancing data diversity. Furthermore, a dual-attribute dataset was created using dynamic and static images from electrical image logs to assist the model in learning the semantic features of pores. Finally, the proposed model was compared with traditional pore identification methods, such as threshold segmentation. The results showed that FILnet demonstrated significant performance advantages on the dual dataset, with a mean intersection over union (MIoU) of 85.42% and a pixel accuracy (PA) of 90.54%. Compared to traditional pore identification methods, the deep learning semantic segmentation approach not only achieves recognition of different types of pores but also improves identification accuracy. This indicates that the network model and data processing methods proposed in this paper are effective and can achieve intelligent recognition and accurate segmentation of pores in electrical image logs.
How to cite: Zhuolin, L., Guoyin, Z., and Yifan, G.: Intelligent Pore Recognition Method for Carbonate Rock Electrical Image Logs Based on Deep Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4896, https://doi.org/10.5194/egusphere-egu25-4896, 2025.
The Central High Atlas in Morocco is characterized by complex geological structures shaped by tectonic and magmatic processes. Gravimetry, a geophysical technique sensitive to subsurface density variations, plays a crucial role in exploring and understanding these features. This study provides a bibliometric analysis of global research on the application of gravimetry, with a specific focus on its use in the Central High Atlas.
The main objectives of this study are to identify global research trends and applications of gravimetry in the study of geological structures, analyze key contributors, scientific collaborations, and dominant themes in gravimetric research, and compare findings from studies conducted in the Central High Atlas with those from other regions worldwide.
A bibliometric analysis was conducted using data from Scopus and Web of Science databases. Keywords such as "gravimetry," "Central High Atlas," and "geological structure" were employed to extract relevant studies. The analysis utilized the R-bibliometrix package and VOSviewer software to map collaboration networks, visualize thematic clusters, and analyze global research trends over time.
The results reveal a significant increase in gravimetric studies over the last two decades, reflecting growing interest in its applications in mountainous regions like the Central High Atlas. The findings highlight deep-seated geological structures, active fault systems, and the relationship between gravimetric anomalies and tectonic processes. Moreover, a comparative analysis shows that studies in Morocco focus heavily on tectonic and magmatic processes, while research in other countries often emphasizes technological advancements and methodological innovations.
This bibliometric study underscores the importance of gravimetry as a tool for exploring complex geological structures in the Central High Atlas. It also highlights the need for stronger international collaborations and interdisciplinary research to advance gravimetric methodologies and foster knowledge exchange across regions.
How to cite: Assoussi, S., Hahou, Y., Khalifa, M., Saadaoui, F., and Oujane, B.: Gravimetric Investigation and Analysis of Tectonic Features and Mineralization Zones in the Central High Atlas (Morocco)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20105, https://doi.org/10.5194/egusphere-egu25-20105, 2025.
This study evaluates the contributions of geophysics and remote sensing to structural mapping in the Central High Atlas region of Morocco. A bibliometric analysis was conducted using data collected from databases such as Scopus and Web of Science. Keywords related to geophysics, aeromagnetic, remote sensing, structural mapping, and the Central High Atlas were used to systematically identify relevant research articles. Analytical techniques, including citation analysis, co-authorship analysis, keyword analysis, and network analysis (using VOSviewer), were applied to explore research trends, collaborations, and key focus areas.
The findings highlight notable research trends in the application of geophysics and remote sensing, identifying key contributors, influential institutions, and pivotal publications in this domain. Research gaps and opportunities for further investigation were also uncovered. Visualization of research networks provided insights into collaboration patterns and thematic focus areas.
This study underscores the importance of geophysics and remote sensing in enhancing the understanding of the Central High Atlas's structural geology. It offers a foundation for future research, emphasizing the need for interdisciplinary collaboration and advanced methodologies to address existing research gaps and further explore the region's geological complexities.
How to cite: Saadaoui, F., Hahou, Y., Ousaid, L., Assoussi, S., and Oujane, B.: Geophysical and Remote Sensing Contributions to Understanding Geological Structures in the Central High Atlas (Morocco): A Review and Analytical Study., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20168, https://doi.org/10.5194/egusphere-egu25-20168, 2025.
Predicting earthquakes remains one of the most profound challenges in seismology and a long-standing aspiration for humanity. Among the array of potential precursors, changes in the Earth’s magnetic field have emerged as a promising yet contentious avenue of research (e.g., De Santis et al., 2015). With advancements in satellite technology, especially with the advent of the European Space Agency’s Swarm mission, we now have the unprecedented ability to measure the magnetic field with extraordinary precision, unlocking exciting opportunities for earthquake forecasting.
In this study, we leverage data from Swarm satellites to investigate whether magnetic anomalies can serve as reliable precursors to earthquakes. Our approach integrates two complementary methodologies: a) global statistical analysis: We applied superposed epoch and spatial techniques to several years of global earthquake data, correlating it with Swarm's magnetic field measurements (De Santis et al., 2019; Marchetti et al., 2022); b) tectonic case study: We focused on major earthquakes occurring from 2014 to 2023 within the tectonically active Alpine-Himalayan belt (Alimoradi et al., 2024).
To analyze these events, we employed an advanced automated algorithm (De Santis et al., 2017) to detect magnetic anomalies in satellite data recorded up to 90 days prior to global earthquakes and up to 10 days before events in the Alpine-Himalayan region. The findings revealed compelling evidence of clear magnetic anomalies preceding earthquakes. Notably, in the Alpine-Himalayan case study, we observed a striking correlation between earthquake magnitude and the duration and intensity of these anomalies: larger earthquakes were associated with stronger and more prolonged signals.
Our predictive framework demonstrated remarkable performance, achieving an accuracy of 79%, a precision of 88%, and a hit rate of 84%. These results underscore the transformative potential of satellite-based magnetic field analysis, paving the way for an operational earthquake prediction system. Such a system could serve as a powerful tool for mitigating the devastating impacts of earthquakes and safeguarding communities worldwide.
The work has been developed in the framework of the following projects: UNITARY- Pianeta Dinamico (funds from MUR), SPACE IT UP (PNRR), Limadou Scienza + (ASI) and FURTHER (INGV).
References
Alimoradi, H., Rahimi, H., De Santis, A. Successful Tests on Detecting Pre-Earthquake Magnetic Field Signals from Space, Remote Sensing, 16(16), 2985, 2024.
De Santis et al., Geospace perturbations induced by the Earth: the state of the art and future trends, Phys. & Chem. Earth, 85-86, 17-33, 2015.
De Santis A. et al., Potential earthquake precursory pattern from space: the 2015 Nepal event as seen by magnetic Swarm satellites, Earth and Planetary Science Letters, 461, 119-126, 2017.
De Santis A. et al. Precursory worldwide signatures of earthquake occurrences on Swarm satellite data, Scientific Reports, 9:20287, 2019.
Marchetti D., De Santis A., Campuzano S.A., et al. Worldwide Statistical Correlation of eight years of Swarm satellite data with M5.5+ earthquakes, Remote Sensing, 14 (11), 2649, 2022.
How to cite: De Santis, A., Campuzano, S. A., Cianchini, G., Alimoradi, H., Perrone, L., and Rahimi, H.: Harnessing Swarm Satellite Magnetic Data to Revolutionize Earthquake Prediction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11991, https://doi.org/10.5194/egusphere-egu25-11991, 2025.
This study examines field-aligned currents (FACs) and polar electrojet (PEJ) characteristics during the extreme May 2024 geomagnetic storms across dawn, dusk, daytime, and nighttime in both hemispheres. FAC and PEJ intensities were up to 9 times greater than usual, with equatorward FACs reaching -44º Magnetic Latitude. Maximum FACs and PEJ are larger at dawn than dusk in the Northern Hemisphere but larger at dusk than at dawn in the Southern Hemisphere. Dawn and duskside FACs correlate best with Dst or solar wind dynamic pressure (Pd) in both hemispheres. On the dayside (nightside), most FACs in both hemispheres are primarily correlated with Pd (merging electric field, Em or Pd). The PEJs correlate largely with Dst and partly with Em and Pd. Duskside (nighttime) currents are located at lower latitudes than dawnside (daytime), and northern currents are positioned more poleward than southern currents. The latitudes of peak FACs are most strongly correlated with Dst or Pd in both hemispheres. However, in the northern daytime sector, they are primarily influenced by Em. The latitudes of peak PEJ show the strongest correlation with Dst or Pd in both hemispheres, except on the northern dawnside, where they are primarily influenced by Em. The qualitative relationships between peak current density, corresponding latitude, solar wind parameters, and the Dst index are derived.
How to cite: Wang, H., Lühr, H., and Cheng, Q.: Local Time and Hemispheric Asymmetries of Field-aligned Currents and Polar Electrojet During May 2024 Superstorm Periods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-396, https://doi.org/10.5194/egusphere-egu25-396, 2025.
In November 2023, the ESA Swarm constellation mission celebrated 10 years in orbit, offering one of the best-ever surveys of the topside ionosphere. Among its achievements, it has been recently demonstrated that Swarm data can be used to derive space-based geomagnetic activity indices, like the standard ground-based geomagnetic indices, monitoring magnetic storm and magnetospheric substorm activity. Given the fact that the official ground-based index for the substorm activity (i.e., the Auroral Electrojet – AE index) is constructed by data from 12 ground stations, solely in the northern hemisphere, it can be said that this index is predominantly northern, while the Swarm-derived AE index may be more representative of a global state, since it is based on measurements from both hemispheres. Recently, many novel concepts originated in time series analysis based on information theory have been developed, partly motivated by specific research questions linked to various domains of geosciences, including space physics. Here, we apply information theory approaches (i.e., Hurst exponent and a variety of entropy measures) to analyze the Swarm-derived magnetic indices around intense magnetic storms. We show the applicability of information theory to study the dynamical complexity of the upper atmosphere, through highlighting the temporal transition from the quiet-time to the storm-time magnetosphere around the May 2024 superstorm, which may prove significant for space weather studies. Our results suggest that the spaceborne indices have the capacity to capture the same dynamics and behaviors, with regards to their informational content, as the traditionally used ground-based ones. A few studies have addressed the question of whether the auroras are symmetric between the northern and southern hemispheres. Therefore, the possibility to have different Swarm-derived AE indices for the northern and southern hemispheres respectively, may provide, under appropriate time series analysis techniques based on information theoretic approaches, an opportunity to further confirm the recent findings on interhemispheric asymmetry. Here, we also provide evidence for interhemispheric energy asymmetry based on the analyses of Swarm-derived auroral indices AE North and AE South.
How to cite: Papadimitriou, C., Balasis, G., Boutsi, Z., and Giannakis, O.: Dynamical Complexity in Swarm-derived Storm and Substorm Indices Using Information Theory: Implications for Interhemispheric Asymmetry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6137, https://doi.org/10.5194/egusphere-egu25-6137, 2025.
The Congo craton is an early Archaean through Paleoproterozoic basement block in Central Africa. It consists of a vast heterogenous granulitic complex extending over 1200 km between the Lomami River (24°E) and the Atlantic coast in Angola. The well-exposed domains of the Congo craton are the Kasaï block, Tanzania block, West-Nile complex, and Ntem-Chailu complex. The latter represents the northwestern edge of the craton in southern Cameroon. The Memve'ele area belongs to the Ntem Complex, where recent investigations have highlighted various lithologies, including TTG gneiss and intensely sheared and folded charnockitic and granitic gneiss, pervasively intruded by younger monzogranite. This region provides a critical window into the complex tectonic evolution of one of Earth's oldest continental blocks. Both TTG and granitic gneiss are riddled with folded or sheared leucogranitic veins, suggesting a local origin through melting and dynamic recrystallization. This study presents a comprehensive investigation of the highly sheared Memve’ele mylonitic corridor. Through detailed field mapping, systematic kinematic analysis, and meticulous petrographic and microstructural studies, we aim to unravel the multiple deformation events that have shaped this region. U-Pb zircon geochronology was employed to precisely constrain the timing of these processes and to correlate them with regional tectonic events. The ultimate goal of this research is to better understand the broader geodynamic implications of these findings for the evolution of the Congo Craton. Initial results reveal that the Memve’ele area has undergone a complex polyphase deformation history, involving at least four distinct events. The early ductile deformation (D1) resulted in the development of a pervasive foliation and associated structures. Subsequent ductile-brittle deformation (D2) overprinted the earlier structures, while later brittle deformation events (D3 and D4) further modified the rock fabric. The studied mylonites yield Mesoarchean ages of 2927 ± 52 Ma. The presence of a sinistral shear zone within the area suggests that the region was subjected to significant shear stresses, likely related to regional tectonic processes such as continental collision or crustal extension. These findings have important implications for understanding the tectonic evolution of the Congo Craton and may provide insights into the potential for mineral exploration in the region.
How to cite: Takodjou Wambo, J. D., Ganno, S., Nzenti, J. P., and Asimow, P. D.: Archean shear tectonics in the Congo craton: insights from Petro-structural characterization and U-Pb geochronology of the Memve’ele mylonite, Southern Cameroon, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20667, https://doi.org/10.5194/egusphere-egu25-20667, 2025.
We present high-resolution ocean bottom node (OBN) seismic data of the Dongfang 1-1 structure in the Yinggehai Basin of the South China Sea, which hosts China's largest offshore gas reservoir. The OBN seismic data reveals more continuous and detailed reflections compared to conventional seismic data, highlighting the internal structure and formation mechanism of a diapir-like structure. The seismic images show a tapered conical structure characterized by a concentric distribution of fractures, with a significant increase in fracture intensity and connectivity towards the center. These fractures, particularly the sub-vertical ones, are interpreted as natural hydraulic fractures formed due to intense overpressurization in the Lower Miocene strata, with formation pressure coefficients up to 2.2. The fractures are believed to have originated from thermogenic hydrocarbon gas generation and inorganic CO2 production. The throughgoing fractures that traverse the entire Neogene succession, including the thick Upper Miocene sealing mudrocks, provide crucial pathways for deep gas-bearing fluids to charge the Pliocene sandstone reservoir. The study underscores the importance of natural hydraulic fractures in bypassing thick sealing sequences and conduiting fluids in deep overpressured environments. Moreover, our results may provide guidance for accurate geological interpretations of mud diapir-like structures in conventional seismic images in many other sedimentary basins.
How to cite: Meng, Q., Yang, B., Guo, Z., and Hao, F.: Architecture of a mud diapir-like structure: insights from ocean-bottom-node seismic data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6417, https://doi.org/10.5194/egusphere-egu25-6417, 2025.
The development of continental rift basins is often accompanied by multiple episodes of volcanic activity. The impact of these volcanic eruptions on the sedimentary filling process of the basin is a geological problem worth considering. This relationship is not only the premise for reasonably explaining the binary filling characteristics and development of sequences of volcanic rocks and sedimentary rocks in rift basins but also the key geological basis for the prediction of volcanic and sedimentary rock reservoirs in rift basins. On the basis of a large amount of three-dimensional seismic data, logging data and lithology data, we estimated the volcanic eruption period, volcanic rock mass and spatial shape of the Changling faulted depression in the Songliao Basin. We then studied the spatial distribution characteristics of lithofacies and sedimentary facies in the basin. Finally, we assessed the influence of volcanic eruptions on the type of sedimentary filling, the distribution of sedimentary facies and the spatial stacking of sedimentary strata. This study revealed that during the rapid rifting stage (Yingcheng Formation depositional period), the Changling faulted depression developed mainly fan delta, braided river delta and lacustrine sedimentary systems and experienced four phases of volcanic eruptions. The lithology, scale and spatial distribution of volcanoes were directly related to the activity and location of the basement faults in this area, reflecting the control that basement fault activity had on the volcanic eruptions. Moreover, the stacking form and eruption scale of volcanic rocks played a substantial role in the paleogeomorphology of the basin, which in turn affected the form of the source channel of the basin, causing changes in the sedimentary facies type and spatial distribution and changes in the spatial overlapping pattern of the sedimentary sequence. Moreover, volcanic eruptions provided different sources of debris to the continental lake basin. The differences in location and delivery methods of these materials complicate the rock structure and reservoir properties of the basin sandstone.
How to cite: Wang, H., Zhang, H., and Liu, A.: Influence of volcanic eruptions on the sedimentary filling of a continental rift basin — A case study of the Yingcheng Formation in the Changling faulted depression in the Songliao Basin, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4049, https://doi.org/10.5194/egusphere-egu25-4049, 2025.
The differences in the tectonic interpretation of ophiolite suites have become a major issue of the debate in the tectonic reconstruction of an ancient orogenic belt, especially when it comes to subduction polarity. In this regard, the Sanjiang Paleo-Tethyan Orogenic Belt in the southeastern Tibetan Plateau provides an excellent case study. The Sanjiang Paleo-Tethyan Orogenic Belt in the northern, eastern, and southeastern Tibet is bounded by the western Jinshajiang‒Garzê‒Litang suture to the north and the Shuanghu‒Changning‒Menglian suture to the south and west. The southern Jinshajiang Suture separates the Zhongzha Block to the east and the eastern Qiangtang Block to the west. The tectonic nature of the NNW-trending southern Jinshajiang ophiolitic mélange remaining controversial. A detailed linear traverse mapping was c across the southern Jinshajiang ophiolitic mélange, with a focus on pillow lavas and the structural relationship between the lavas and their country rock (Paleozoic sedimentary rocks). The results of a field study, in conjunction with new geochronological data and geochemical data, have enabled the identification of the Zhongdian continental back-arc basin. This basin was filled with a flysch succession and at least two horizons of pillow basalt from 267 to 254 Ma. The fining- and thinning-upward nature of the sedimentary succession, widespread syndepositional folds and syndepositional breccias, and submarine channel sediments, as well as intensive basaltic volcanism suggest that this back-arc basin generated in a typical extensional environment. The inversion of the back-arc basin was completed within a relatively short period of one million years (254~253 Ma), resulting in the development of overturned folds of the flysch succession and a latest Permian to Early Triassic back-arc foreland basin in front of the folded belt. Whole-rock geochemical data for the basalts and coeval gabbros suggest that the petrogenetic process of the basalts in the back-arc basin is likely comparable to that of basalt in a rift system as well, which is a lithospheric extension induced uplift of lithospheric mantle and asthenosphere and allowing decompression partial melting of the mantle peridotite. The late stage pillow basalts exhibit a stronger arc signature than the earlier massive basalt and diabase. The Zhongdian back-arc basin is considered to be an extinct continental and arc-type back-arc basins, which are characterized by thick crust, shallow bathymetry, and may not evolve into “normal” oceans. The formation and inversion of the Zhongdian back-arc basin are believed to have been caused by rollback and subsequent break-off of the subducted oceanic slab. During the inversion, the crust shortening occurred predominantly in the back-arc basin, while the southwestern shoulder of the back-arc basin, which was weakly deformed, was shifted north-eastward for ~30 km. The formation process of the Zhongdian back-arc basin is comparable to that of a typical continental rift system, the asymmetric architecture of which has mostly been inherited by the structures formed during the basin inversion. The southern Jinshajiang ophiolitic mélange is representative of the inverted Zhongdian back-arc basin, which is a short-lived, partially mature oceanic basin.
How to cite: Xin, D., Yang, T., Xue, C., Jiang, L., and Xiang, K.: Formation and inversion of a short-lived continental back-arc basin in Southeastern Tibet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3894, https://doi.org/10.5194/egusphere-egu25-3894, 2025.
Bathymetry of marginal sea basins is commonly deeper than the half-space cooling prediction for large oceans, but what controls this pattern is poorly understood. Here, based on abundant seismic sections with increasingly available databases, we perform an enhanced approach that specifically corrects for post-spreading cooling to reassess thermal subsidence across the Southwest Subbasin (SWSB) and the broader South China Sea (SCS) basin. We attribute the current excessive subsidence of the SCS basin primarily as a response to the post-spreading cooling process, which has global applicability to other marginal sea basins and accounts for at least 86% of the observed depth anomaly. Additionally, the mode of magma supply during seafloor spreading plays a crucial role in shaping reconstructed shallower bathymetry of the SCS basin relative to predictions from the half-space cooling model. A stronger magma supply deriving from the regional subduction system can explain the relatively shallow depth developed during the opening of the SCS compared to large oceans. In contrast, a westward decayed magma supply, driven by localized rift propagation induced by the inherited pre-Cenozoic heterogeneous lithospheric structure of South China, attributes to subsidence discrepancies among sub-basins and within the SWSB.
The sediment-corrected depth of most marginal seas is, on average, more than 500 m deeper than that of large oceans, with maximum anomalies ranging from -0.95 to -2.70 km (in 0.5° bins). The sediment-corrected depths exhibit statistically poor correlations with the spreading rate, indicating that the thermal evolution of marginal seas is not primarily controlled by the spreading rate, unlike large oceans. Neither can this anomaly be fully explained by dynamic topography driven by large-scale mantle convection or by localized variations in the degrees and patterns of subduction systems, although the latter may be an important factor influencing the bathymetry of still-active marginal seas. We interpret at least 44.5% of these anomalies as a result of long-term post-spreading thermal subsidence in inactive marginal seas, with magmatic processes influencing bathymetry during oceanic plate formation. We propose that the post-spreading secular cooling, together with the variable mode of magma supply and potential dynamic subsidence processes driven by subducting slabs, play pivotal roles in the formation of the topographic anomalies within the oceanic basins of marginal seas.
How to cite: Fang, P. and Ding, W.: Reconciling bathymetric anomalies of marginal sea basins through magmatic and cooling processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2072, https://doi.org/10.5194/egusphere-egu25-2072, 2025.
The Precambrian history of the Indian continent centers around several Archean cratonic nuclei, e.g. the Singhbhum Craton, the Bundelkhand Craton and the Aravalli Craton in the north; the Bastar Craton in the central-east, and the Dharwad Craton in the south. Apart from a group of less disturbed and unmetamorphosed Meso- to Neoproterozoic platformal sedimentary packages resting over deformed and metamorphosed Archean to Paleoproterozoic basement, several Neoproterozoic orogenic belts occur at the margins of these Archean cratonic blocks. These craton-margin orogenic belts are the areas of intense deformation and multiple phases of deep- to intermediate depth, and hence constitute the sites of major records of crustal-scale material recycling through plate movements. They occur on the east, south and west of the Archean cratonic clusters (conjugate north and south Indian cratonic blocks). Though major deep-crustal deformation and metamorphism in these craton-margin orogenic belts can be tracked mostly up to the earliest Neoproterozoic, exhumation-related reactivation seems to be more common in these belt around ca. 800–750 Ma.
In this study, we shall highlight the east and west Indian marginal belts. We shall present the new data showing conditions of metamorphic pulses and their age from the rocks of the Mercara Shear Zone, marking the south-western boundary of the Archean (>3000 Ma) Dharwar craton. The results indicate at least four events; (1) ~2900 Ma; basin formation with supply from craton, (2) 2900–2700 Ma; age of prograde metamorphism, (3) 2700–2500 Ma, age of charnockite magmatism during Dharwar Orogeny with metamorphic peak, and (4) final reactivation at 830–730 Ma marking exhumation of deep crust during retrograde metamorphism along the crustal scale shear zone (stretching lineation and S-C fabric formation as last deformation event. We shall also review our group’s recent published data on the pressure-temperature-deformation-fluid-age histories during the orogenic reactivation of the western boundary, and the Chilka Domain of the northern Eastern Ghats Belt. Together we shall try to collate data showing the idea of a near-synchronous orogenic reactivation surrounding Indian cratonic cluster during middle to late Tonian Period with various preceding age gaps.
How to cite: Das, K., Bose, S., Ganguly, P., and Chatterjee, A.: Circum-Indian craton-margin orogenic reactivation during ca. 800-700 Ma: Tectonometamorphic characterization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14725, https://doi.org/10.5194/egusphere-egu25-14725, 2025.
The Kaliguman Shear Zone (KSZ) in northwestern India marks the boundary between the South Delhi Fold Belt to the west and the Aravalli Fold Belt to the east. Structural analysis reveals a narrow, high-strain zone characterized by the development of mica schist along this boundary. The principal structural orientation trends in the NE-SW direction. Strain analysis indicates that the rocks in this zone formed under transpressional deformation conditions.
The metamorphic history of the KSZ is well-preserved in the mica schists, which predominantly contain garnet and staurolite. Petrological and textural studies have helped establish the relative crystallization sequence of mineral phases during the metamorphic events. Examination of garnet porphyroblasts reveals a complex deformation pattern, reflecting pre-, syn-, and post-tectonic events associated with fabric formation. Geothermobarometric analysis indicates that the mica schists underwent amphibolite facies metamorphism. Phase equilibria analysis, supported by PT pseudosections, shows peak metamorphic conditions at approximately 590±10 °C and 4.7 kbar. Garnet isopleth plots suggest increasing pressure and temperature during metamorphism, which is consistent with the inferred PT path. Variations in the modal abundance of index minerals further corroborate this evolutionary trajectory. These findings support a model of crustal thickening for the KSZ. The textural control monazite age data from the mica schists confirms that the shear zone was formed during the early Neoproterozoic. The study provides valuable insights into the tectonic evolution of the contact between the Delhi and Aravalli Fold Belts, highlighting the role of shear zones in accommodating deformation and facilitating metamorphic processes during Neoproterozoic orogenic events.
Keywords: Kaliguman Shear Zone, Aravalli, Delhi Fold Belt, Neoproterozoic, NW India
How to cite: Mondal, S., Roy, A., and Chatterjee, S.: Neoproterozoic Tectonics of the Kaliguman Shear Zone: Implications for the Delhi-Aravalli Fold Belt Contact, NW India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1504, https://doi.org/10.5194/egusphere-egu25-1504, 2025.
In northwest India, the South Delhi Fold Belt (SDFB) is a NE-SW trending region of the Neoproterozoic age, consisting of poly-deformed and poly-metamorphosed rocks. To the west lies the Marwar Craton, and the boundary between them is defined by a crustal-scale shear zone, dated to 810 Ma, known as the Phulad Shear Zone (PSZ). The syn-tectonic Phulad Granite, which runs along the PSZ, played a key role in stitching together the Marwar Craton and the SDFB during the 810 Ma tectonic event. Approximately 30 km to the east of the PSZ, a quartz monzonite pluton, emplaced within the calc-silicates of the SDFB, is observed. This study focuses on the meso- and micro-structures, as well as the geochemistry of the quartz monzonite, to better understand its emplacement conditions and the tectonic processes at that time.
In the field, the quartz monzonite exhibits a saccharoidal texture with a crude foliation, defined by the alignment of feldspar grains. The foliation in the monzonite has a mean orientation of 14°/67° E. The quartz monzonite is primarily composed of k-feldspar and plagioclase feldspar, with minor amounts of quartz, amphibole, and titanite. Microstructural analysis reveals features indicative of sub-magmatic, high-temperature deformation, suggesting that the rock underwent solid-state deformation. These microstructural characteristics of the quartz monzonite suggest a syn-magmatic deformation event. The foliation in the monzonite is broadly parallel to the mylonitic foliation in PSZ, further supporting the idea of a syn-tectonic emplacement. The geochemical study of the quartz monzonite displays a syn-collisional granite-type geochemical signature with a distinctly negative REE pattern. The REE pattern features suggest that garnet played a significant role in the petrogenesis. By integrating micro and meso-structural analyses with geochemical data, we infer that the emplacement of the quartz monzonite coincided with the development of the PSZ and the intrusion of the Phulad Granite. Despite the temporal overlap, the quartz monzonite and the Phulad Granite display significant geochemical differences, denoting distinct petrogenetic processes. Based on the integration of all available data, we propose that the quartz monzonite was emplaced during the 810 Ma collisional event, resulting from the partial melting of garnet-bearing mafic crust. While both quartz monzonite and Phulad Granite likely share a common source, the depth of melting was different. The greater depth of melting in the eastern portion suggests an eastward subduction of the Marwar Craton during this tectonic event.
How to cite: Ghosh, D. D. and Chatterjee, S. M.: Neoproterozoic magmatism in NW India and its implication for crustal evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5552, https://doi.org/10.5194/egusphere-egu25-5552, 2025.
Monazite has the potential to place temporal constraints on the crustal melting in high-grade metamorphic rocks like granulites and migmatites. Melt loss in granulite-grade metamorphic rocks plays a key role in progressively depleting LREE in the residue and enhancing the dissolution of monazite during heating to the metamorphic peak. Newly formed monazite are therefore more abundant in leucosomes than the residue. Higher degree of partial melting and subsequent melt loss, therefore, poses a major hindrance to constraining the mobility of these elements in the micro-domain scale, particularly during the early stage of melting at amphibolite to granulite facies transition. To overcome such an issue and to understand the behavior of this mineral during the onset of granulite facies metamorphism, metamorphic rocks that have reached the P-T conditions culminating at the aforesaid transition should be targeted. Considering this, the present study has been carried out on charnockite from the northern Eastern Ghats Belt, India which underwent such transition (M2) following crystallization during an earlier granulite facies metamorphic event (M1). The rock is composed of plagioclase (Pl), K-feldspar (Kfs), quartz, orthopyroxene, biotite, and garnet with apatite, allanite, and monazite as accessory phases. The rock has well-developed gneissic foliation, demarcated by alternate biotite +garnet-rich and quartzofeldspathic layers. While both the feldspars show grain boundary migration recrystallization, quartz grains are deformed by sub-grain rotation recrystallization. Garnet is porphyroblastic and post-kinematic as it overgrows the matrix biotite. The former phase is closely associated with cuspate Kfs and quartz grains which developed as a result of incipient dehydration melting of moderately fluorine rich biotite during the aforesaid transition. Monazite grains are coarse (up to 200 µm across), mostly elliptical and either partially or completely replaced by the reaction rim of apatite+ thorite with an external corona of allanite in the biotite+garnet-rich layers. In case of partial replacement, the oscillatory-zoned relict monazite core is preserved. Th-rich patches are present in such cores. Interestingly, the coronitic assemblage overgrows the matrix biotite is always associated with porphyroblastic garnet. On the contrary, corona-free monazite grains are abundant in quartzofeldspathic layers. Spot dates from the oscillatory-zoned relict monazite core yield a weighted mean age of 960±6 Ma. Th-rich patches, showing prominent huttonite substitution, yield a weighted mean age of 938±7 Ma. Integrating monazite textural and age data, we interpret that the ca. 960 Ma represents the crystallization age of the charnockite magma which coincides with the M1 metamorphic event of the Eastern Ghats Province (EGP). The ca. 938 Ma, additionally, corresponds to the age of the M2 event when biotite dehydration melting occurred and porphyroblastic garnet was formed. Based on the textural evidence and mineral phase chemical data, we propose that the replacement of primary monazite occurred via coupled dissolution precipitation process in the presence of incipient melt originated during biotite dehydration melting. Such melt was fluorine rich and helped to mobilize REEs by forming REE-fluoride complexes and was incorporated in allanite corona. Monazite grains in quartzofeldspathic layers must have escaped the melting reaction and the melt-induced element mobility.
How to cite: Ganguly, P., Banerjee, A., and Das, K.: Behavior of monazite during incipient dehydration melting of charnockite at the northern Eastern Ghats Belt, India: Insights on the mobility of REE at amphibolite-granulite facies transition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11645, https://doi.org/10.5194/egusphere-egu25-11645, 2025.
The South Delhi Fold Belt (SDFB) within the northwestern Indian Shield is a Proterozoic NE-SW trending fold belt. The western boundary of the SDFB is defined by the Phulad Shear Zone, formed during a transpression regime around 820-810Ma. Granite rocks of ~1Ga have been documented from the western part of the fold belt and are linked with the formation of the Rodinia Supercontinent. These granites are closely associated with gabbroic rocks. The present study focuses on the geochemistry of these granites and the mafic rocks, as well as their field structure and petrography.
The granites and the mafic rocks are confined to a narrow linear belt along the western part of the fold belt. Detailed field studiesreveal that the foliations in the granites, mafic and mylonites within PSZ share a common stress regime and are broadly synchronous. Geochemically these granites are ferroan, calc-alkalic, metaluminous to weakly peraluminous and their classification in granite discrimination diagrams confirms A-type and within plate granite. The mafic rocks exhibit a compositional range fromtholeiitic to calc-alkaline, with atrace element ratio resembling enriched mid-oceanic ridge basalt (E-MORB) type magma. The tectonic discrimination diagram suggestsrift-relatedmagmatism. Geochemical analysis of these bimodal magmatic compositions in the SDFB, encompassing both mafic rocks and A-type granites are typically associated with areas experiencing extensional tectonics, particularly rift-related magmatism. Integrating field structures, petrography and geochemistry of these granite and the mafic rocks suggests that the ~1Ga granite and the associated mafic rocks formed in an extensional regime and are not directly linked to the collisional assembly of the Rodinia Supercontinent.
How to cite: Manna, A., Chatterjee, S. M., Roy, A., and Sarkar, A. K.: Geochemistry of ~1Ga granite and associated mafic rocks from the South Delhi Fold Belt, NW India, and its tectonic significance, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19572, https://doi.org/10.5194/egusphere-egu25-19572, 2025.
In highly populated urban areas such as Tehran, with over 17 million inhabitants, identifying active faults is essential to hazard and risk management. Tehran is located in central Alborz within the Arabia-Eurasia collision zone. The region is the manifestation of interplay between structural systems of the western and eastern Alborz. The study area focuses on the Lavizan and Babaei fault-related fold structures as the main Quaternary features of the Tehran piedmont. Tehran's rapid urbanization in the past few decades has made it impossible to access fault traces and the associated geomorphic features in the field. This research is the first study which uses photogrammetric methods to extract detailed 3D data and digital terrain model (DTM) from archival imaging. Historical aerial photographs were acquired from 1955-1965, before the city's development. A DTM with a spatial resolution of about 86 centimeters, an orthophoto-mosaic, and a three-dimensional model were created employing photogrammetric methods. The geomorphic analysis of the model reveals lateral unidirectional eastwards growth of the Lavizan and Babaei structures during Pleistocene and Holocene. The presence of wind gaps developed from water gaps, and sharp fault scarps in the upper Pleistocene and Holocene geomorphic surfaces testify this lateral propagation. This study presents a typical example for a long-lasting tectonic activity and its Holocene continuation on the E-W fault-related fold structures, which directly affect urban areas in the Iranian metropolitan.
How to cite: Alizadeh, P., Shabanian, E., and Masoumi, Z.: Investigation of the Growth of Active Faults in the Tehran Metropolitan Employing Historical Aerial Photos and Photogrammetric Techniques, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6123, https://doi.org/10.5194/egusphere-egu25-6123, 2025.
Slip characteristics of tectonic faults are highly correlated with earthquake risks. However, the stress conditions in-situ are not static, because tides and seismic waves produce dynamic stress disturbances. The effect of fluids also needs to be considered. The fault slip evolution considering both, stress perturbation and fluid pressure is poorly investigated in the laboratory.
We performed direct shear tests on saw-cut granite joints using a shear box device with external syringe pump. The lower part of the specimen was driven by constant load point velocity, and static/dynamic normal loads were applied to the upper part. LVDTs recorded horizontal and vertical movements: fault slip and vertical dilatancy, respectively. The impact of two factors are studied in the experiment: pore fluid pressure and applied normal stress oscillation amplitude.
In conclusion, static pore fluid pressure reduces effective normal stress and shear stiffness of the sheared fault. Under constant normal stress, the reduction in fault shear stiffness caused by fluids synchronously competes with the reduction in critical stiffness (Kc) as the effective normal stress decreases. The stick-slip events are most intensive under low fluid pressure and high normal stress. Under oscillating normal stress, as the normal stress oscillation amplitude increases, the overall fault shear strength weakens continuously. Frictional strengthening and aseismic slips always occur in the normal stress loading stage. Normal stress unloading leads to multi-step stick-slip behavior of the sheared fault. The fault normal deformation is controlled by both normal loading/unloading and asperity overriding. Increasing pore pressure and superimposed normal stress magnitudes lead to more dramatic shear stress changes, but the degree of seismic slip is reduced.
How to cite: Tao, K., Konietzky, H., and Dang, W.: Seismic fault slip affected by pore pressure and cyclic normal stress – deduced by lab investigations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2323, https://doi.org/10.5194/egusphere-egu25-2323, 2025.
The collision of the Indian and Eurasian plates ~ 55 Ma formed the Himalaya, one of the youngest mountain belts. This convergence led to two significant metamorphic stages: M1, which occurs under high pressure and low temperature in a thick crust, and M2, resulting from crustal thinning in a high-temperature, low-pressure environment, evolved the gneissic domes. This study provides the first apatite fission track (AFT) and zircon fission track (ZFT) thermochronological record from one of such gneissic domes in the NW Himalaya viz., the Gianbul Dome (GD). The dome is bounded by two extensional shear zones, namely the South Tibetan Detachment System (STDS) dipping towards NE and the Khanjar Shear Zone (KSZ) dipping towards SW. The AFT cooling ages range from 14.2 ± 1.2 to 5.7 ± 1.1 Ma, and ZFT ages range from 22.8 ± 2.2 to 14.6 ± 0.9 Ma. The ZFT ages remain almost constant across the dome, suggesting thermal relaxation during this period, while the AFT ages are young towards the extensional shear zones of KSZ and STDS. The fission-track data, in combination with the published Ar-Ar and (U-Th)/He cooling ages, has been modeled using a thermo-kinematic inverse and forward model to analyze the processes that led to the exhumation of the dome. Various scenarios like river incision, lithology, deformation along faults like Main Himalayan Thrust, Main Central Thrust, STDS, glacier control, and erosion control over exhumation have been tested. Our results suggest that the extension of normal fault is the primary mechanism for the exhumation of the GD. The extension happened in two phases: (a) during the initial normal sense movement along the STDS when the reverse sense of shear was switched to the usual sense of shear during the early Miocene, and (b) during the Late Miocene. The initial phase of extension is a well-recognized phenomenon in the Himalayan orogen that has been explained through models like channel flow or ductile wedge extrusion. However, the first report of extensional activity along the STDS during the Late Miocene allows us to test whether it is a local phenomenon or a regional event that happened in the brittle stage. Thus, we compiled all the published geochronological and thermochronological data of all the prevailing gneissic domes in the Himalayas from west to east and ran the 3D thermokinematic model to assess the exhumation path of the rocks and brittle stage deformation history. Our results suggest that two phases of extension happened in the entire arc of the Himalayan orogen. The first phase facilitated the southwest migration of ductile materials of rocks from mid-crustal depths accompanying the extension because of gravitation, favoring the channel flow concept. The second phase of extensional collapse happened during ~7-3 Ma ago in the brittle stage. We hypothesize that a drop in gravitational potential energy led to the reactivation of extensional faults along the Himalayan arc. Thus, we propose that extensional collapse in the collisional mountain belts is a cyclic phenomenon that happens to attain a stable, steady state of the orogens.
How to cite: Patel, R. K., Adlakha, V., Mukherjee, K., Pundir, S., Pradhan, P., and Patel, R. C.: Extensional collapse of the Himalayan orogen in the Late Miocene., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1368, https://doi.org/10.5194/egusphere-egu25-1368, 2025.
This study explores the application of Fracture-Induced Electromagnetic Radiation (FEMR) for stress analysis in the Ramon Crater, a tectonically “stable” region in southern Israel. FEMR, an innovative geophysical method, detects electromagnetic pulses emitted during micro-fracturing events to infer stress orientations. Unlike traditional seismic techniques, FEMR is sensitive to subtle stress changes, making it suitable for regions with limited seismicity. Field measurements were conducted at nine locations using the ANGEL-M device, capturing high-sensitivity electromagnetic signals to determine the stress azimuth. The results revealed a dominant mean stress azimuth of 308°, aligning closely with the acute bisector of two principal joint sets in the region, WNW-ESE and NNW-SSE. These orientations correspond to historical compressional stress from the Syrian Arc Stress (SAS) regime and more recent extensional stress from the Dead Sea Stress (DSS) field. The superimposition of these regimes has created a complex tectonic environment, evidenced by features such as joint sets, fault planes, and basaltic dikes. FEMR measurements correlate with these geological indicators, confirming the technique’s ability to detect regional stress directions and their evolution over time. In the past decade, the method of FEMR has progressively gained impetus as a viable, non-invasive, cost-effective, real-time geophysical tool for stress analysis in various parts of the world. Its range lies in delineating tectonically active zones, landslide-prone weak slip planes, highlighting stress accumulation in mines and tunnels, etc. This study highlights FEMR’s viability for stress field analysis, especially in stable tectonic zones. Its ability to capture micro-crack activity and subtle stress shifts offers a detailed understanding of how tectonic forces shape regional geodynamics. While FEMR enhances stress detection capabilities, careful calibration with geological models is essential to differentiate transient stress changes from long-term tectonic trends. This research advances FEMR’s application in geophysical studies, particularly for monitoring stress fields in regions influenced by ancient and ongoing tectonic forces.
How to cite: Das, S. and Frid, V.: The Fracture Induced Electromagnetic Radiation (FEMR) technique as a tool for stress mapping: A case study of the Ramon Crater, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9651, https://doi.org/10.5194/egusphere-egu25-9651, 2025.
