Upper mantleSwave velocity structure of the East Anatolian-Caucasus region

Abstract

Geodynamic processes occurring in the upper mantle such as slab break off and lithosphere delamination often result in high rates of lithospheric deformation and rapid tectonic uplift of large areas. The continent-continent collision zone between Arabia and Eurasia has been widely studied in this context, but several different viable geodynamic models exist to explain the uplift and deformation of the Anatolian Plateau and the Caucasus Mountains. We have imaged the uppermost mantle shear wave velocity structure of the East Anatolian-Caucasus region using surface wave tomography to better understand the regional tectonic activity since the onset of the collision between the Arabian and Eurasian Plates. Furthermore, we used our tomographic models to better understand the processes, which are responsible for the formation of the 2 km high plateau and the widespread volcanism in eastern Turkey, as well as reactivation of deformation and deep seismicity in the eastern Greater Caucasus. Our model of regional upper mantle shear wave velocity structure supports subduction of the northern and southern branches of Neo-Tethys lithosphere between Eurasia and Gondwana and suggests a possible underthrusting of the Kura Basin lithosphere beneath the Greater Caucasus.

Petrogenesis of mafic collision zone magmatism: The Armenian sector of the Turkish–Iranian Plateau

“…Most papers infer Eocene break-off of a north-dipping slab beneath the Pontides (e.g., Keskin et al, 2008;Sosson et al, 2010) which implies that the Pontide slab had no role in Pliocene-Quaternary magmatism. In contrast, a much later Miocene break-off of a north-dipping Pontide slab beneath the Lesser Caucasus (close to the Sevan-Akera Suture Zone), as suggested by recent seismic data (Skolbeltsyn et al, 2014), would be penecontemporaneous with break-off beneath the more southerly Bitlis Suture and should result in a very wide zone of asthenospheric upwelling which might better explain the Late Miocene onset of collision magmatism in Eastern Anatolia, Armenia and Georgia.…”

“…1) covers~1.5 × 10 6 km 2 across Eastern Turkey, Iran, Armenia, Georgia and Azerbaijan. Arabia collided with this region in the Late Eocene-Oligocene (~35-25 Ma) before a proposed Middle-Late Miocene (~15-10 Ma) break-off of the northdipping southern Neo-Tethys oceanic slab beneath the Bitlis and Zagros sutures (Keskin, 2003;Allen and Armstrong, 2008;Zor, 2008;van Hunen and Allen, 2011;McQuarrie and van Hinsbergen, 2013;Skolbeltsyn et al, 2014). Late Oligocene to Early Miocene marine carbonates cover much of the western margin of the present plateau (Morley et al, 2009), implying that plateau growth significantly postdates initial collision.…”

“…Most tectonic models for the region include a Mesozoic to Early Cenozoic north-dipping northern Neo-Tethys subduction zone beneath the Pontides in Northern Turkey and the Arc of the Lesser Caucasus in Armenia (e.g., Adamia et al, 1981;Rolland et al, 2009Rolland et al, , 2011Rolland et al, , 2012Dilek et al, 2010;Sosson et al, 2010;Hässig et al, 2013;Skolbeltsyn et al, 2014). Authors have suggested that the northern Neo-Tethyan or 'Pontide' slab broke off during the Eocene (e.g., Keskin et al, 2008), but Skolbeltsyn et al (2014) argued for a more recent (Miocene) break-off based on surface wave tomography results. This implies near-simultaneous break-off of the northern (Pontide) and southern Neo-Tethyan (Bitlis) slabs which may also have implications for collision magmatism in Eastern Anatolia and Armenia and will be discussed in Section 6.4.…”

“…The timing of break-off processes beneath Eastern Anatolia and the Caucasus in the Late Cenozoic is not well understood (e.g., Skolbeltsyn et al, 2014). Most papers infer Eocene break-off of a north-dipping slab beneath the Pontides (e.g., Keskin et al, 2008;Sosson et al, 2010) which implies that the Pontide slab had no role in Pliocene-Quaternary magmatism.…”

Crustal S-wave structure around the Lake Van region (eastern Turkey) from interstation Rayleigh wave phase velocity analyses

“…The crustal structures of eastern Turkey were studied by numerous authors using different geophysical methods in addition to the ETSE project (Mindevalli and Mitchell, 1989;Hearn and Ni, 1994;Çınar, 1998;Maggi and Priestly, 2005;Barazangi et al, 2006;Gans et al, 2009;Mutlu and Karabulut, 2011;Ateş et al, 2012;Bakırcı et al, 2012;Vanacore et al, 2013;Tezel et al, 2013;Toker, 2014;Komut, 2014;Skobeltsyn et al, 2014;Çınar and Alkan, 2015;Delph et al, 2015a;Türkoğlu et al, 2015). Hearn and Ni (1994) obtained a Pn velocity distribution for most of the Turkish-Iranian Plateau of as low as 7.9 km/s.…”