Project Title: Deformation processes of lateral slab tearing, from crust to mantle.

Supervisor: Benjamin Guillaume, Jean-Pierre Brun

Objectives: The Mediterranean has three “rollback subduction systems”, in the Aegean, Central Mediterranean and Alboran Sea. Each has an asymmetric structure that results from lateral slab tear along one arm of the rollback system, also documented by mantle tomography. This suggests that lateral slab tearing plays a major role in the dynamics of slab rollback. The project aims at elucidating the mechanisms of slab deformation in rollback subduction systems and its consequences at the Earth’s surface. Two complementary and interactive perspectives will be developed: 1) New concepts and tools to study deformation in the mantle on the basis of slab deformation displayed by tomographic models (using analogue models and numerical simulations) and 2) Tests of model inferences in the Betics-Alboran and Aegean systems and elsewhere (southern Andes), in terms of relations between deformation in the mantle and in the crust.

Expected Results: (1) mechanical constraints on slab deformation in terms of rheology (slab viscosity and viscosity contrasts between slab and upper mantle) and boundary conditions (modes of mechanical instability); and (2) comprehensive coupled deformation patterns of surface lithosphere (upper plate) and mantle (slab and surrounding upper mantle). Fieldwork in Betics and Aegean will document the kinematics and timing of the tearing process and together with tomographic models the relation between surface and deep deformations.

Academic secondment: UniRomaTre, Faccenna, 1 month, analogue modelling and application to interpretation of tomographic models. CSIC Barcelona, Garcia-Castellanos, 1 month, comparison between modelling of slab tearing in the Alboran sea, carried out in Rennes and Barcelona. UM, Gueydan, analysis and interpretation of uplift-subsidence and crustal and mantle deformation patterns in the Betics -Alboran Sea system. Industry secondment: g.o. logical, two times one month, to work on salt tectonics in Messinian deposits.

Links to other projects: Thematic link to ESR4,5,10, which all focus on slab deformation in roll-back systems.

Geological data will be shared with ESR1,5,7; methodological development for modelling compared with ESR 1,2,7,9.