3.3.3. Evolution of East-Mediterranean subduction zones, Arabia-Eurasian collision and related magmatism

During Cretaceous and Tertiary times, evolution of the Aegean-Anatolian orogenic system was controlled by northward subduction of a system of oceanic basins and intervening ribbon-shaped continental fragments, flanking the Neotethys Ocean to the North (Okay and Tüysüz, 1999; Stampfli et al., 2001; Papanikolaou et al., 2004; Van Hinsbergen et al., 2005b). Starting in Mid-Cretaceous times, subduction of Neotethys commenced in the eastern Taurides sector and was completed during the Eocene, resulting in collision of Arabia with the Taurides orogenic wedge. In the western Taurides sector, subduction of Neotethys commenced during the Late Cretaceous and continues at present. In the Hellenides sector, subduction of Neotethys oceanic lithosphere commenced only at the Mio-Pliocene transition and continues at present (Makris and Yegorova, 2006). The Aegean-Taurides system represents a classical accretionary orogen that has progressed in its eastern parts to a continent-to-continent collisional setting whereas its western parts have remained in an ocean-continent collisional setting up to the present.

The subducting slab beneath the Aegean region, as imaged by seismic tomography, extends to a depth of about 1500 km and has a length of some 2400 km, reflecting the dimension of post-Jurassic lithospheric shortening (Bijwaard et al., 1998; Wortel and Spakman, 2000). The presence of this slab, which consists of alternating segments of oceanic lithosphere and continental lower crust and lithospheric mantle, indicates that no slab detachment has occurred in the Aegean region (Faccenna et al., 2003; Van Hinsbergen et al., 2005b). Seismic tomography indicates that also the Cyprus arc is associated with a deep-reaching subduction slab. However, the Hellenic and the Cyprus slabs appear to be separated by a vertical tear that extends from Rhodes into western Anatolia (De Boorder et al., 1998; Wortel and Spakman, 2000; Faccenna et al., 2006). Development of this slab-tear presumably facilitated the rapid SSW propagation of the Hellenic arc, involving sinistral shear along its SE flank that is marked by the Strabo and Pliny trenches (Ten Veen et al., 2005). Latest Miocene activation of the sinistral EAFZ apparently caused a disruption of the Cyprus arc subduction slab, its Pliocene detachment from the lithosphere and the extrusion of alkali basalts in SE Anatolia (Yurtmen et al., 2000). Similarly, the mid-Miocene and Pliocene magmatism of eastern Anatolia (Arger et al., 2000) is presumably related to detachment of the Neotethys slab within the subducted margin of the continental Arabia lithosphere and the subsequent activation to the NAFZ and EAFZ. This is compatible with tomographic data that show at depths of 600 km a foundered subduction slab that is separated from the lithosphere (De Boorder et al., 1998; Wortel and Spakman, 2000; Faccenna et al., 2006).

Slab detachment (or alternatively lithospheric delamination) can be held responsible for changes in the chemical signature of arc volcanism and an increase in heat flow, contributing to weakening of the lithosphere and its post-orogenic collapse (De Boorder et al., 1998).

TOPO-EUROPE intends to refine available tomographic images of the lithospheric and mantle structure of the Aegean-Anatolian region and to prepare a sequence of cross-sections and depth slices. Furthermore, the age and geochemical/isotopic signature of volcanics will be reviewed in terms of potential changes from subduction-related to slab detachment-related magma generation and of the timing of such changes. These data will serve as input for the modelling of first-order processes that governed the evolution of the Aegean-Anatolian area, with emphasis on its Neogene and Quaternary deformation. Special attention will be directed towards establishing a link between “deep” driving processes and the “shallow” geological response, aimed at predicting the near-surface response of the evolving system that can be compared with and tested against independent geological, geophysical and geodetic data. Of special interest is the assessment and modelling of processes that controlled the Pliocene-Quaternary rapid SSW advance of the Hellenic arc-trench system and the associated extension in the Aegean region. Did subduction resistance of the Erathostenes seamount impede southward advancement of the Cyprus arc? What is the mass balance between Plio-Quaternary compressional shortening in East Anatolia, lateral escape of Anatolia and expansion of the Aegean area?