Magma generation by slab steepening and breakoff beneath a subduction-accretion complex: An alternative model for collision-related volcanism in Eastern Anatolia, Turkey

Eastern Anatolia is regarded as one of the best examples of continental collision, represented by a 2 km high plateau. It displays shallow and diffuse seismicity, indicating that the crust is still being actively deformed. Perhaps the most striking aspect of Eastern Anatolia is the volume and compositional variability of collision-related volcanic products erupted during the Neogene and Quaternary time. A number of models have been proposed for the genesis of this volcanism in the region. However, recent geophysical studies have revealed that a mantle lithosphere is almost completely absent beneath a greater portion of the region, which makes us question the validity of the previous models. In this paper, we propose a new model for magma genesis: slab steepening and breakoff beneath a large subduction-accretion complex. This model holds that a northward subducting oceanic lithosphere beneath the Eastern Anatolia Accretionary Prism gets steepened and eventually detached from the continental lithosphere of the Bitlis-Poturge Massif, following the continent-accretionary complex collision. This brings the asthenospheric mantle in contact with the accretionary complex at shallow depths (e.g., around 50 km), resulting in rapid regional uplift and extensive melting which leads to collisional volcanism.