Sessions of interest for the InterRidge community at EGU 2020

The following sessions of interest for the InterRidge community will be organized at the EGU (European Geosciences Union) 2020 General Assembly in Vienna on 3-8 May 2020. Plese submit your abstracts before the 15 January 2020 at 13:00 CET.

Session TS8.1

Oceanic and continental transform faults: towards a multi-disciplinary approach

Transform faults form major active plate boundaries and are intrinsic features of plate tectonics and plate accretion. Submarine transforms are likely to be fundamental pathways for fluid circulation in depth, thus significantly contributing to the exchange between the lithosphere and the hydrosphere. This implies serpentinization and weathering that affect the mechanical properties in the deformation zone. An open question is the influence of the elemental exchange between the crust and ocean water on these processes, as well as the interactions with the biosphere, both at the surface and at depth. Continental transforms and strike-slip faults are often a site of major earthquakes, representing major hazards for the population. Here too, the role of weathering in the deformation zone is still unconstrained. Both types of faults are still poorly known in terms of structure, rheology and deformation. These features are seismically active zones, with large earthquakes often being recorded on the largest faults. Yet, little is known about the rupture process, seismic cyclicity and active deformation of transform faults. Recent works have shown that fracture zones, supposedly inactive features, can be reactivated and be the site of large earthquakes and deformation. Additional open questions are the way transform faults deform under far-field stresses, such as plate kinematic changes, and under more local stresses, what are the time constants of the processes and what are the primary controls of the tectonic and magmatic styles of the response. The tectonic and magmatic response of large offset transforms, particularly, is still largely unknown.

This session aims to present recent results on studies of these large features, especially on the rheology, deformation patterns, rupture processes, fluid circulation and physical properties of transform faults. We welcome observational studies on strike-slip and transform faults, both continental and oceanic, on fracture zones and on transform continental margins (structural geology and tectonics, geophysical imaging of the crust and lithosphere, petrology and geochemistry, seismology, fluid circulation and rock alteration, geodesy) as well as modelling studies, both analogue and numerical. Cross-disciplinary approaches are encouraged. The submission of abstracts divulging on-going international projects (drilling sites, seismic reflection imaging along strike-slip faults) are also welcome.

This session is promoted by the Oceanic Transform Faults working group of InterRidge and is a bridge between oceanic and continental transforms and a multi-disciplinary approach.

Convener: João Duarte
Co-conveners: Marcia Maia

Session OS4.6

Using and acquiring time-series data to enhance the knowledge of key oceanic processes and their interactions

Time-series sensor data or repeated observation and sampling of Essential Ocean Variables, acquired at fixed-point observatories or using mobile platforms and research vessels, are essential to understand oceanic processes from the surface to the oceanic sub-bottom. In this session, we welcome presentations that demonstrate the use of such monitoring results to address physical, chemical, biological and geological processes in the water column and at the seafloor. Multidisciplinarity, the use of several sets of complementary data, and an emphasis on the interactions between the hydrosphere, biosphere and geosphere are particularly welcome. We also welcome presentations on new ocean monitoring experiments, and on innovative technologies for marine observatories. This session is sponsored by the European Multidisciplinary Seafloor and water column Observatory - European Research Infrastructure Consortium (EMSO-ERIC).

Co-sponsored by EMSO ERIC
Convener: Eric Delory | Co-conveners: Mathilde Cannat, Andrew Gates, Katsiaryna Pabortsava

Session TS14.1

Celebrating the 100th birth anniversary of Marie Tharp: Seafloor mapping and ocean plate tectonics

The pioneering seafloor mapping and visualization by Marie Tharp played a key role in the acceptance of the plate tectonic theory. Her physiographic maps, published with B. Heezen, covered the Earth’s oceans and revealed with astonishing accuracy the submarine landscape. She exposed the topography of a seafloor that turned out not to be flat, displaying instead features such as seamounts and volcanic chains, trenches, mid-ocean ridges, and transform faults. Marie Tharp co-authored the first papers describing the major fracture zones in the Central Atlantic (Chain, Romanche, Vema), and her work directly contributed to the recognition of the role of mid-ocean ridges in plate tectonics and oceanic accretion.

To honour Marie Tharp’s profound and lasting contribution to plate tectonics and marine goesciences, this session seeks contributions addressing plate tectonics in the oceans, based primarily on information from seafloor mapping, including regular or high resolution bathymetry, seafloor imagery (sonar or optical) at all scales, geophysical imaging of the seafloor, in addition to satellite altimetry, and in situ observations (robots or submersibles). Results of seafloor sampling, seismic imaging, seismicity studies or in-situ monitoring are also very welcome. Contributions may address the role of faults, seafloor volcanism, magmatism, and hydrothermal circulations, in the construction and evolution of the ocean crust and lithosphere from mid-ocean ridges and transform faults, to mid-plate domains and subductions. We seek contributions at all scales, from regional studies to a global scope, as that pioneered by Marie Tharp.

Co-organized by GD6
Convener: Mathilde Cannat | Co-conveners: Susanne Buiter, Javier Escartin

Session GMPV2.7

Magmatic processes at divergent plate boundaries in space and time.

Divergent plate boundaries represent the most important interfaces between the Earth’s crust and mantle, and its surface with the hydro- and atmosphere. The continuous spreading of plates leads to decompression of the mantle and ultimately melting. Melt evolution and ascent and eruption of magmas along mid-ocean ridges and backarc spreading centres provide a unique means to improve the understanding of the elemental flux through the thin oceanic crust and the impact of the melting regime on hydrothermal activity driving heat transfer and growth of the oceanic crust. Plate tectonic parameters such as rate of spreading, segmentation or interaction with mantle melting anomalies will result in temporal and spatial changes of magma composition. In the case of backarc spreading centres the addition of subduction zone components triggers additional complexity to the crustal structure and temporal and spatial changes of magma composition. Throughout geological history, major changes in the heat budget of the Earth are likely to impact on the physical and chemical fluxes through spreading centres including the hydrothermal circulation. This is also of economic interest since many sulfide deposits mined onland today originally formed along submarine divergent plate margins. The discrepancy in size of sulfide deposits currently mined and found at the seafloor rises the question whether this is an artefact of incomplete exploration or a result of fundamental changes in the elemental cycling through time.

This session aims to bring together geochemical, geodynamic, geophysical, microbiological and hydrothermal contributions from the modern seafloor and to Archaean greenstone belts in an attempt to trace the evolution of divergent plate boundaries in space and through time.

Convener: Philipp Brandl | Co-convener: Christoph Beier