The award recognizes Dr. Dubosq pioneering nanogeology research, advancing our understanding of plastic deformation in minerals using innovative 2D and 3D analytical techniques in tectonics and structural geology.
Stephan Mueller Medal Lecture by Heidrun Kopp.
The award recognizes Prof. Kopp innovative research and groundbreaking discoveries in convergent margin systems, large earthquake processes, active fault slip, magmatic arc systems and geohazards.
Tectonic-scale geological phenomena are fundamentally controlled by nanoscale physiochemical mineral processes. Understanding these processes across multiple length scales is crucial for determining how mass and stress are transferred during tectonism. Minerals exhibit complex structure-property relationships that govern their mechanical and chemical behaviour, yet these relationships have been historically underexplored in Earth sciences. Advances in nanotechnology and instrumentation, including techniques such as high-resolution electron backscatter diffraction, electron channeling contrast imaging, transmission electron microscopy, and atom probe tomography, now enable unprecedented investigations of nanoscale features in geomaterials. The correlative approach has given rise to the emerging field of nanogeology, which helps bridge the gap between nanoscale and tectonic-scale processes. Recent nanoscale investigations have demonstrated the fundamental role of structural defects and element mobility in controlling the mechanical properties and deformation behaviour of minerals in the brittle-ductile regime. For example, detailed microanalyses of garnet reveal a novel precipitation hardening mechanism where Fe diffused along grain boundaries of recrystallized garnet, nucleating Fe-rich nanoclusters. These clusters act as barriers to dislocation migration, resulting in localized strain hardening. This process provides a potential mechanism for mechanical strengthening in the lower continental crustsubsequently influencing large scale geodynamic processes. Similar investigations of pyrite, a critical metal-bearing sulfide mineral, reveal nanoscale fluid inclusions that facilitate the diffusion of trace elements into crystalline defects, such as dislocations, inhibiting their movement, and leading to mineral hardening. Such findings are particularly significant, as the brittle-to-ductile behaviour of sulfides has been directly linked to the upgrading of critical metal deposits. These discoveries highlight the dynamic interplay between nanoscale element mobility and the rheology of minerals, and by consequence, larger mass transfer dynamics. Moreover, deformation-driven element redistribution raises questions about the reliability of deformed minerals as petrological tools. For instance, the deformation of zircon may compromise its use as a robust geochronometer, whereas the deformation of garnet may influence its reliability as a thermobarometer. A deeper understanding of element mobility in the presence of defects is essential for accurately interpreting geochemical data and reconstructing tectonic histories. Overall, these breakthroughs highlight the pivotal role of nanoscale processes in shaping tectonic phenomena, emphasizing the need for a multi-scale approach to understanding Earth's dynamic behaviour.
How to cite: Dubosq, R., Schneider, D., Rogowitz, A., and Gault, B.: Scaling up: Nanoscale insights into tectonic phenomena , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4567, https://doi.org/10.5194/egusphere-egu25-4567, 2025.
Understanding the physical processes and interactions that govern the dynamics of the seafloor is key to unraveling the fundamental mechanisms of the marine lithosphere and its boundaries. These processes not only shape the ocean floor but also influence a variety of geohazards that pose significant risks to coastal communities.
One of the greatest challenges in marine geosciences is to identify the locations and underlying causes of marine geohazards. To achieve this, we need a multidisciplinary approach and comprehensive, multi-sensor geophysical measurements that integrate observations of the seafloor conditions and the complex interactions of sub-seafloor processes that lead to these events. This includes a detailed understanding of the physical, chemical, and mechanical factors that drive natural hazards including earthquakes, tsunamis, and volcanic eruptions. Seafloor processes, from tectonic movements to crustal deformation to magmatic activity, are central to understanding how these phenomena occur.
Recent advancements in marine geophysical research, particularly in seafloor geodesy, ocean bottom array seismology, and micro-bathymetry have allowed for the quantification of seafloor processes and their dynamic changes under tectonic stress. The majority of large (magnitude Mw>8.5) earthquakes occur in subduction zones. The associated surface deformation is concentrated at the seafloor and is often coupled with the triggering of tsunamis. The seabed therefore harbors information about tectonic stress and elastic deformation. This information is crucial for early warning concepts and can be methodically analyzed using seafloor geodesy in conjunction with seismic and earthquake studies. The plate boundary offshore northern Chile is one of the seismically most active regions on the globe and is the site of comprehensive multi-sensor seafloor monitoring. The integrated data analysis revealed co-seismic stress changes and aftershock activation of extensional faulting of the upper continental plate, indicative of active subduction erosion during the co-seismic and post-seismic phase. One of the most striking findings is the correlation of the seismogenic up-dip limit with a pronounced decrease in plate boundary reflectivity. High-resolution in-situ strain measurements from seafloor geodetic arrays monitor the tectonic stress build-up across the subduction zone, which is characterized by very low rates during the interseismic phase. Tectonic stress build-up across a plate boundary was also monitored along the offshore segment of the North Anatolian Fault Zone in the Sea of Marmara, revealing a significant slip on this fully locked segment.
Looking ahead, marine geophysical research is poised to expand significantly, addressing new challenges and utilizing new technologies and methods across disciplines. The next generation of seabed monitoring systems will use real-time data analysis and underwater acoustic communication in autonomous ‘smart’ networks for targeted monitoring. On a broader scope, the utilization of existing telecommunication systems has the potential to profoundly change solid earth monitoring. These observations may also elucidate potential preparatory phases of major subduction earthquakes, detect landslides on coastal slopes, and monitor largely unknown submarine volcanic activity. Operational real-time access will reduce earthquake and tsunami early warning delays significantly.
How to cite: Kopp, H.: The Dynamic Seafloor: Enhancing Our Knowledge of Seafloor Processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4841, https://doi.org/10.5194/egusphere-egu25-4841, 2025.
