Modeling the evolution of lithospheric delamination under the Eastern Anatolia by testing various rheological and compositional properties

Abstract:

The East Anatolian plateau is a distinct geological region bordered by the Arabian continental plate to the south and the Eurasian plate to the north. Existing geological evidence suggests that ~ 2 km of uplift along the plateau occurred since the 13 Ma in conjunction with the Arabia-Eurasia collision. Previous geodynamic models suggest that the high plateau is compensated by thick lithosphere under the plateau; however seismological and petrological studies imply that significant portions of the lithosphere have been removed beneath all of present day East Anatolia. As such, the plateau may instead be supported by hot mantle after the delamination of the northern branch of the Neotethys slab and following break-off under the accretionary complex. We use geodynamical models to test the applicability of delamination and break-off hypothesis to the geodynamic evolution of Eastern Anatolia. By using thermo-mechanical numerical experiments, we investigate the influence of lower crust rheology/composition, plate convergence velocity, Moho temperature variation and strain weakening in the crust that represent model constraints on the lithospheric evolution from ocean subduction to delamination. Model predictions for the surface topography, crustal thickness, and Moho temperature evolution as well as delaminating hinge migration have been tested against geophysical and geological observations for Eastern Anatolia. Our findings indicate that wider orogenic crust delaminates from the mantle lithosphere, –with 2 km of surface uplift and 50 km of crustal thickening- when felsic granulite lower crustal rheology is used without any plate velocity. Lithospheric delamination is more subdued with mafic granulite, diabase and wet peridodite lower crustal rheologies because there is more coupling between the crust and the mantle lithosphere and at the hinge location crustal thickening exceeds 54 km. Furthermore, a higher plate convergence velocity promotes faster slab steepening of the delaminating slab and its break-off, while there is less lithospheric delamination. The surface uplift of 5 km occurs with 5 cm/year convergence velocity. Our results provide useful insights into the understanding of rheological, thermal and boundary effects in the lithospheric delamination process for East Anatolia.