Geodynamic evolution of the Aegean: constraints from the Plio-Pleistocene volcanism of the Volos-Evia area

The Plio-Pleistocene lava flows and domes of the Volos-Evia area were erupted between 3.4 and 0.5 Ma ago on the western continuation of the North Anatolian Fault, in a back-arc position with respect to the active arc. They are mainly high-K calc-alkaline trachyandesites. Based on their Sr-Nd-Pb isotopic compositions, the mantle source of the Volos-Evia area lavas is similar to that of a large volcanic belt that developed north of the Pelagonian-Attic-Cycladic-Menderes massifs, encompassing a 35 Ma timespan and widespread over a large area from NW Greece-Macedonia to the Aegean-western Anatolia. In contrast, southern Aegean arc rocks have a similar subduction fingerprint but distinctly lower Sr and higher Nd isotopic compositions. The geochemical and isotopic differences between southern and northern Aegean rocks may be ascribed to the different nature of the mantle wedge: depleted asthenosphere under the the southern Aegean, and lithosphere northward. The lack of an asthenospheric mantle wedge below the northern Aegean fits with the hypothesis of an almost horizontal subduction of the African slab. In the mantle reference frame the African slab is moving out of the mantle, and a slab-driven suction flow of the underlying mantle may be responsible for the recent development of a thin asthenospheric layer in the southern Aegean mantle wedge.