LITHOSPHERIC DELAMINATION IN AN OROGENIC SETTING: AN EXAMPLE FROM THE EASTERN ANATOLIA COLLISION ZONE

We examine the role of mantle lithosphere delamination beneath Eastern Anatolia where lithospheric thinning, plateau formation, volcanism and syn-convergent crustal extension have been all suggested. The evolution of delaminating lithosphere (i.e., a peeling away of mantle lithosphere from the crust) is modeled using SOPALE, a geodynamic code that treats the thermomechanical evolution of heterogeneous media. We focus on several observables in the experiments: Surface topography, Moho topography, and crustal structure/deformation rates. A range of convergence rates are imposed during delamination to see the control of lithospheric shortening on surface topography crustal deformation. The models suggest that delamination causes zones of surface uplift (and heating) and subsidence above the mantle lithosphere gap. The subsidence is overwhelmed and an elevated plateau develops in the presence of large-scale plate convergence. In the experiments, contemporaneous delamination and plate shortening at 3 cm/yr produces plateau uplift (in a confined zone of ~600 km) that is consistent with the present day surface topography of Eastern Anatolia along a profile at 42°E. The removal of mantle lithosphere induces distinct regions of contraction/thickening and extension/thinning of the crust. Based on our strain rate calculations, the latter occurs even within a regime of plate shortening, which may explain the development of a ~ 200 km zone of extension in the midst of the Eastern Anatolia at the Arabia-Eurasia convergent plate boundary. The results apply directly to Eastern Anatolia, but may be used to understand similar styles of anomalous topography and syn-convergent extension at the Apennines-Tyrrhenian, Himalayas, Andes and Alboran Sea/Rif-Betics.