Dynamics of Plateau Growth: Geodynamic Modeling of the East AnatolianPlateau Uplift Through Double Subduction Processes

Abstract

The Turkish–Iranian Plateau was formed by the collision between the Arabian andEurasian plates, commencing along the Bitlis-Zagros suture in the Late Eocene (~30-35 Ma). This region, commonly partitioned into the East Anatolian Plateau and theIranian Plateau, is associated with significant differences in terms of lithosphericstructure despite an overall average of ~2 km. The geodynamic evolution of EastAnatolia is represented by a double subduction system, where the two branches ofNeo-Tethys were subducting beneath Eurasia, constantly accumulating accretionarymaterial that forms the bulk of the plateau today (i.e., East Anatolian AccretionaryComplex). Seismic evidence demonstrates that the region has unusually thin MOHO(~35 km around Lake Van region) while the whole area is formed mostly by oceanic(accretionary) material and is underlain by no or very thin mantle lithosphere. Theuplift of East Anatolia is attributed to slab break-off and slab peelback (delamination),combined with crustal shortening. However, the intricate plate dynamics arising fromsuch a double subduction system, controlling plateau formation remains unclear.Here, we conducted 2D numerical experiments and comparative model sets indicatethat, in a double subduction system like Eastern Anatolia, the mechanisms of slabbreak-off and peelback heavily depend on the rheology of the subducting plates andthe coupling between the overlying and subducting plate along the trenches. In casesof strong coupling between subducting and overlying plates, we observed anamalgamation of the two subducting plates as they converge, potentially resulting ina break-off as a single blob, depending on plate rheology. Conversely, in models withweaker coupling along the trenches, peelback along the northern slab creates a thinlithosphere along the accretionary prism, such as in the evolution of the EasternAnatolian Plateau. Our results highlight the important interaction between thesubduction systems where rheological constraints of the lithosphere, among othermodel parameters, exert a first-order control for plateau formation.