Driving the upper plate surface deformation by slab rollback and mantle flow

- Asthenospheric flow modulates the surface strain in collisional-subduction domains.
- The suction exerted by slab rollback can dominate on extrusion mechanisms.
- Subduction and mantle flow drive the surface strain of the Tethyan collisional belts.

The relative contribution of crustal and mantle processes to surface deformation at convergent plate margins is still controversial. Conflicting models involving either extrusion mechanisms or slab rollback, in particular, were proposed to explain the surface strain and kinematics across the Tethyan convergent domain. Here, we present new high-resolution 3D thermo-mechanical numerical joint models of continental collision, oceanic subduction and slab tearing, which for the first time allow self-consistent reproduction of first-order Tethyan tectonic structures such as back-arc rifting and large-scale strike-slip faults accommodating continental escape. These models suggest that mantle flow due to slab rollback and tearing can modulate the surface strain and kinematics by locally enhancing trench retreat and dragging the upper plate from below. These results highlight the active role of the asthenospheric flow in driving the surface strain, not only by modulating the vertical stresses and producing dynamic topography but also through sub-horizontal motion. We discuss the implications of these findings based on observations across the Aegean-Anatolian and eastern Indian-Eurasian domains, though similar considerations may as well apply to other settings.

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