Tectonic significance and petrological features of oceanic uniits composing Kocali complex (Adiyaman)

Evidence of continental rifting and subduction to form the S Neotethys is found within the Koçali Complex. This complex is a folded, thrust-imbricated succession that includes lavas, volcaniclastic sediments, pelagic carbonates, radiolarites and manganiferous deposits with ophiolitic units. Interbedded ribbon cherts of Koçali volcanic-sedimentary series contain radiolarians of Late Triassic to Late Jurassic age. The lower part of the succession of Mid?-Late Triassic age (Tarasa Formation) is dominated by enriched mid-ocean ridge basalt (E-MORB). The overlying Late Triassic to Mid-Jurassic interval (Konak Formation) is characterised by intercalations of ocean island basalt and E-MORB. Considering the structural position, the basalts erupted within the outer part of a continent–ocean transition zone. Continental rifting probably occurred during the Late Triassic (Carnian–Norian). Early to Mid-Jurassic lavas and volcaniclastic sediments indicates volcanism probably after continental rifting. In addition, the Karadut Complex is a broken formation that is located at a relatively low structural position just above the Arabian foreland. After continental rifting, MORB and ophiolitic rocks formed within the S Neotethys further to north which developed between Bitlis-Pütürge microplatelet and Arabian platform. These ophiolites, are a remnant of Late Cretaceous subduction zone (SSZ) oceanic lithosphere, defined as Koçali ophiolite. The Koçali Ophiolite developed within S Neotethis, is a part of Peri-Arabian ophiolite belt which contains, Kızıldağ (Turkey), Troodos (Cyprus), Baer-Bassit (Syria) and Semail (Oman) ophiolites situated in the east Mediterranean region. The internal structure, petrology and geochemistry of Koçali Complex makes a magmatic progress from island arc tholeiites (IAT) to boninitic composition and late phase (gabro dyke) IAT composition. Smilar structural feature and geochemical trend of coeval Kızıldağ, Trodos and Baer-Bassit ophiolites indicates that this multi-staged SSZ magmatism is common in most of the Tethys ophiolites. Geochemistry of crustal units of Koçali ophiolite reflects a multi-staged evolution of SSZ magmatism in the Tethys subduction and exhibits the activeness of this multi-staged magmatism within a fore-arc tectonic setting in S Neotethys ocean during Late Cretaceous simultaneously. This Tethys subduction is accord with the early arc volcanism in the Eocene-Oligocene Izu-Bonin Mariana system. Tectonic emplacement of Koçali ophiolite onto the Arabian platform took place by earliest Maastrichtian time. Regional interpretation is try to made by comparing the continental rifting examples of Triassic time which monitored in the eastern Mediterranean region and elsewhere, with subra-subduction zone (SSZ) oceanic lithosphere residuals.