Anomalous Gold Deposit Along se Europe Tethysian Margin: a Signature of Return-Induced Upper Mantle Flow around Hellenic Slab Edges

Relationship between ore genesis, plate tectonics and mantle dynamics are now well established as evidenced by the strong correlation between plate boundaries and ore deposit distribution. Magmatism and ore deposit spatial distribution in SE Europe, along Tethysian convergent margin, occur in relatively narrow belts that can be correlated to the history of subduction dynamics. In addition, epithermal gold and porphyry-type deposits appear in SE Europe in a short temporal window. In Aegean and western Turkey, deposits are associated with high potassium calco-alkaline volcanic complexes. Therefore, anomalous warmer (and probably weaker) domains should be present under specific zones of the overriding lithosphere, as suggested by seismic tomography. These hot and weak zones may also be related to particular processes associated with subduction (slab tearing or/and delamination). Herein, we propose a new interpretation in which heat is provided by asthenospheric return flow associated with the retreating Hellenic slab since at least 20 Ma. This flow comprises a toroidal component where streamlines are subparallel to the slab surface, in a horizontal plane and a poloidal component, down dip, in a vertical plane. Dynamic models of the subduction system and its surrounding flow are numerically investigated to constrain the temporal evolution of such a system versus thermal/rheological properties and geometries of the slab. The confrontation between compilation of available geophysical data (seismic tomography, seismic anisotropy and calculated mantle flow velocities), identification of Cu-Au mineralization distribution (from BRGM mineral deposits database) and the analysis of temporal and spatial constrains given by modeling, allows to identify one of the main dynamic processes responsible for shallow thermo-mechanical effects in the crust connecting i) relatively short-lived regional igneous and hydrothermal activities and ii) the formation of related mineralization.