The temporal evolution of the active margin along the Southeast Anatolian Orogenic Belt (SE Turkey): Evidence from U–Pb, Ar–Ar and fission track chronology

Abstract

The Southeast Anatolian Orogenic Belt (SAOB) resulted from the north-dipping subduction of the southern Neotethyan oceanic lithosphere in late Mesozoic and early Cenozoic. However, the timing and the rate of the continental collision are still under debate. Here, we present new U–Pb, Ar–Ar and Fission Track ages from the I-type calc-alkaline granitoids (Esence, Doğanşehir and Baskil) cutting the Göksun, İspendere and Kömürhan ophiolites and also the Malatya–Keban metamorphics representing the Tauride active continental margin along the SAOB. In this study, high- to low-temperature thermochronological methods, applied to the granitoids, are used to understand the temporal and geodynamic evolution of the Tauride active continental margin and continental collision between Tauride and Arabian platforms in the frame of the Neotethyan convergence during Cretaceous and Miocene. The U–Pb zircon ages range from 83 to 88Ma for the Baskil and from 81 to 83Ma for the Esence granitoids. The 39Ar–40Ar ages indicate that these late Cretaceous granitoids cooled below 300°C in 6–10Ma. The formation ages and the timing of the gradual cooling of the late Cretaceous granitoids are similar to metamorphism age and the timing of the exhumation of the HP/LT Bitlis metamorphics during this stage. The combined field, geochemistry and geo-thermochronological data suggest that the first continental collision event occurred between Bitlis–Pütürge micro-continents to the south and Tauride platform to the north in an oblique subduction zone between 84 and 74Ma. The granitoids continued uplifting during early-middle Eocene together with the exhumation of HP/UHT Berit metaophiolite in an extensional regime related to the opening of the Maden back-arc basin. This period also let the intrusion of the Doğanşehir arc magmatism, intruding the Pütürge and Malatya–Keban metamorphics, Berit metaophiolite, and Maden Complex. The Eocene Doğanşehir granitoid has similar U–Pb and 39Ar–40Ar ages, suggesting a fast cooling. The apatite fission track (AFT) ages for all granitoid bodies suggest that they were mainly cooled or uplifted in two episodes, where the first one is in the Eocene in an extensional setting. The AFT data marked the final continental collision between the Taurides and the Arabian platform first in Oligocene and the break-off of the subducted slab and the delamination process caused fast uplift of the Eastern Anatolia during middle to late Miocene.