Oligocene Magmatism in the Zagros Thrust Zone (Sahneh-Marivan Area): Evidences for the Second Neotethyan Subduction Occurrence in the Paleogene


At the southwest of Sanandaj (Sahneh-Marivan area), in the Zagros thrust zone, with NW-SE direction, some major intrusive bodies with basic to intermediate composition and minor acidic veins are intruded in the Cretaceous-Paleocene formations, causing contact metamorphism up to albite- epidote or pyroxene hornfels facieses. In addition to intrusive bodies there are minor outcrop of basic volcanic rocks. In southwestern margin of intrusive bodies some dismembered ophiolitic complex are outcropped along the Zagros thrust faults. The intrusive bodies and associated volcanic rocks are of Oligocene age. Chemical composition, especially the behavior of major, trace and rare elements indicate that these intrusions and related volcanic rocks are calc-alkaline to tholeiitic and generated from a heterogeneous mantle in an active margin. Age, chemical composition and tectonic setting of these rocks may indicate that after the breakdown of Neotethyan oceanic crust in the Late Cretaceous, the southwestern part of the oceanic crust was subducted beneath the northeast part of it, and Oligocene magmatism is outcome of such an event. If these inferences are rational, the final collision of Arabian and Iranian plates must be occurring in the end of Oligocene and the beginning of Miocene