The modes of propagation of the North Anatolian Fault and the mechanical nature of the Aeagean lithosphere
Résumé
The Aegean lithosphere has been extended in a wide rift to metamorphic core complex (MCC) mode for the last 30 Myr. This supposes that the crust and lithosphere was warm and weak. However, in the last 5 Myr, this supposed weak lithosphere has been cut across by the propagation of the North Anatolian Fault (NAF) in the Aegean system. To a large community, the propagation of the NAF contradicts the weakness of the Aegean lithosphere, and it is difficult to reconcile the formation of the MCCs with the presence of the fault. Based on the comparison of simplified numerical models with today's strain-rate field in the North Aegean Sea and in continental Greece, this contribution proposes a conceptual model in which the North Aegean lithosphere has been made strong in response to the formation of the Aegean metamorphic core complexes. In the first place, we present the results of a 2D thermo-mechanical models of MCC, which we validate through large dataset of P-T-t path and field observations. This model shows that during the formation of the domes, the weak lower crust has been sucked from beneath the North Aegean sea up to the Cyclades and Rhodope and that in the post extension phase, the Aegean lithosphere is much stronger than before at the current location of the NAF. In the second place, we design 3D simplified mechanical models of the propagation of the NAF and perform a parametric studies in which we vary the coupling between the upper crust and the mantle by varying the nature of the lower crust in half of the model. This coupling affects the localization of the deformation in the mantle lithosphere and the timing of the progressive localization of the fault in the crust.