New Insıght ınto a Subductıon-Related Orogen: A Reappraısal of the Geotectonıc Framework and Evolutıon of the Middle and West Parts of the Southeast Anatolıan Orogenıc BELT (Türkiye)

Abstract

The geotectonic framework and the evolutionary history of the Southeast Anatolian Orogenic Belt are closely related to the assemblage of eastern and western Gondwana and the subsequent events from the opening of the southern branch of the Neo-Tethys to the final collision.  The first geotectonic event is the subduction of the Proto-Tethys under the northern Gondwana during the Ediacaran and accordingly the formation of igneous rocks within the lower units of Bitlis-Pütürge Massifs. The first orogeny affecting the region was the Cadomian orogeny.  The southern branch of the Neo-Tethys began to open between the Arabian Plate (North of Gondwana) and today's southeastern Anatolian metamorphic massifs in the Late Triassic, and oceanic spreading continued until the Late Cretaceous. The ophiolites and an intra-oceanic arc were formed during the Late Cretaceous (92 to 82Ma and 84–72 Ma respectively) in a SSZ tectonic environment formed by the northward subducting South Branch of Neo-Tethys ocean crust. The Arabian Platform entered the subduction zone and as a result ophiolites thrust on the Arabian Plate margin, the metamorphic massifs were fragmented and migrated to the South onto the ophiolites and arc magmatics in the Maastrichtian. Despite the collision, the continental subduction continued and a break-off of subducted slab was formed. A widespread marine transgression is realized onto the Arabian Platform and ophiolites from Latest Cretaceous to Early Miocene to the South of the Bitlis-Pütürge metamorphics. The remnant of the ocean continued untill Late Miocene to the North of the Bitlis-Pütürge massifs as marine basins with different depths and morphological characteristics. The magma formed by the partial melting of the mantle wedge, the rising deep asthenosphere mantle and the continental crust forms Maden arc over the ophiolites and the Bitlis-Pütürge Massifs in the Middle Eocene. Behind the Maden arc, shallow-deep marine carbonates and clastics were deposited in a back-arc basin (Kırkgeçit basin). The closure which started in the Late Eocene and ended in the Late Miocene enabled Southeast Anatolian Orogenic Belt to take its actual position.