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Friday Earth Sciences Talk

Speaker and topic: Dr Alissa Kotowksi,'Up close and personal with a subduction channel: Subduction, underplating, and return flow recorded in the Cycladic Blueschist Unit exposed on Syros Island (Cyclades, Greece)'

Subduction zones are fundamental drivers of Plate Tectonics, localize strain at the lithosphere-scale over millions of years, and host deformation transients such as megathrust earthquakes and slow slip events. However, the geometry and internal structure of the deep interface (~30-70 km) is poorly resolved by remote sensing techniques like seismic tomography, which limits our understanding of deep subduction dynamics.

I will synthesize structural, metamorphic, and geochronologic data from exhumed metamorphic rocks exposed on Syros Island (Cyclades, Greece) to reconstruct the tectono-metamorphic history during Eocene subduction and exhumation in the Aegean. I will argue that subduction of structurally distinct coherent units occurred contemporaneously with exhumation of previously accreted tectonic slices, in a subduction channel, or conveyor-belt fashion. Distributed, ductile return flow along the top of a refrigerating slab achieved ~80% of rock exhumation from peak depths of ~50-60 km to crustal depths of ~20 km. This work provides the spatial and temporal resolution of subduction tectono-metamorphism that is needed to quantify interface thermal structure, timescales of accretion, evolving interface strength, and exhumation rates.

With the Friday Earth Sciences Talks (FEST) we intend to bring the departments of Earth Sciences and Physical Geography together. The aim is to present (mostly) Utrecht-based Earth Sciences in an accessible way in order i) to stay familiar with each other’s work across disciplines and ii) to help (in particular MSc.) students in their orientation on possible graduation specialisations and future careers. Alumni are also invited.