Cenozoic geodynamic evolution of the Aegean

Abstract

now Institut des Sciences de la Terre d'OrléansInternational audienceThe Aegean region is a concentrate of the main geodynamic processes that shaped the Mediterranean region: oceanic and continental subduction, mountain building, high-pressure and low-temperature metamorphism, backarc extension, post-orogenic collapse, metamorphic core complexes, gneiss domes are the ingredients of a complex evolution that started at the end of the Cretaceous with the closure of the Tethyan ocean along the Vardar suture zone. Using available plate kinematic, geophysical, petrological and structural data, we present a synthetic tectonic map of the whole region encompassing the Balkans, Western Turkey, the Aegean Sea, the Hellenic Arc, the Mediterranean Ridge and continental Greece and we build a lithospheric-scale N-S cross-section from Crete to the Rhodope massif. We then describe the tectonic evolution of this cross-section with a series of reconstructions from ~70 Ma to the Present. We follow on the hypothesis that a single subduction has been active throughout most of the Mesozoic and the entire Cenozoic, and we show that the geological record is compatible with this hypothesis. The reconstructions show that continental subduction (Apulian and Pelagonian continental blocks) did not induce slab break-off in this case. Using this evolution, we discuss the mechanisms leading to the exhumation of metamorphic rocks and the subsequent formation of extensional metamorphic domes in the backarc region during slab retreat. The tectonic histories of the two regions showing large-scale extension, the Rhodope and the Cyclades are then compared. The respective contributions to slab retreat, post-orogenic extension and lower crust partial melting of changes in kinematic boundary conditions and in nature of subducting material, from continental to oceanic, are discussed

Kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern Mediterranean region since the late Cretaceous

“…Blueschists unit in the Cyclades with the Vari detachment in Syros and the SCSZ in Ios defining, respectively, the top and the base of the subduction channel or the extrusion wedge Ring et al, , 2010Brun and Faccenna, 2008;Huet et al, 2009;Jolivet and Brun, 2010].…”

“…~9 kbar, 550-570 °C) followed by a greenschist-facies retrograde metamorphism observed in the Andros, Tinos and Kea islands, in Lavrion (figure 6) [Altherr et al, 1982; Bröcker et al, 2004;Jolivet and Brun, 2010;Grasemann et al, 2012;Huet et al, 2014;Scheffer et al, 2015] and in the Olympos, Ossa and Pelion tectonic windows [Schermer, 1993;Lips et al, 1999;Lacassin et al, 2007]. In the lower Miocene, HT-MP metamorphism (i.e.…”

“…The latter was partly accreted to the Pelagonian nappe contributing to the building of the Hellenides, while its buried part underwent early Eocene HP-LT metamorphism recorded in the Cycladic Blueschists unit and the Cycladic basement [Bonneau and Kienast, 1982;Bonneau, 1984;Wijbrans and McDougall, 1988;Tomaschek et al, 2003;Lagos et al, 2007]. These units were then progressively exhumed up to the end of the Eocene in the Cyclades and in the Olympos, Ossa and Pelion tectonic windows as a synorogenic extrusion wedge bounded by the Vari detachment on top (in Syros) and the SCSZ at the base (in Ios) (figure 9) Ring et al, , 2010Brun and Faccenna, 2008;Huet et al, 2009;Jolivet and Brun, 2010].…”

“…Concomitantly with the southward retreat of the subduction zone, the lower part of the thickened Rhodope crust was strongly heated allowing the development of Paleocene MT-MP metamorphism associated with migmatites (figure 9) [Burg et al, 1996;Mposkos, 1998;Jolivet and Brun, 2010].…”

“…Tethyan active margin and do not specifically focus on the smaller-scale eastern Mediterranean region, where subduction, collision, obduction, slab roll-back and tearing processes have occurred since the Mesozoic [Le Pichon and Angelier, 1979;Şengör and Yilmaz, 1981;Jolivet and Faccenna, 2000;Jolivet et al, 2003;Faccenna et al, 2006Faccenna et al, , 2013Brun and Faccenna, 2008;Ring et al, 2010;Brun and Sokoutis, 2010;Jolivet and Brun, 2010]. Detailed kinematic reconstructions…”