Geodynamic evolution of the Sanandaj-Sirjan Zone, Zagros Orogen, Iran

Abstract

The Sanandaj-Sirjan Zone is a metamorphic–magmatic belt, associated with the Zagros Orogen and part of the Alpine-Himalayan orogenic system in Iran. Stratigraphic, metamorphic, magmatic, and tectonic evidence presented here indicates that the Sanandaj-Sirjan Zone, the Central Iranian Microcontinent, and the North West Iranian Plate were a part of the Arabian plate until the Late Permian, when they separated during the opening of the Neotethys. Later subduction of the Neotethys oceanic crust beneath the Sanandaj-Sirjan Zone resulted in the complete closure of the Paleotethys Ocean in the Early Upper Triassic. The following extensional regime (related to slab roll-back) caused separation of the Sanandaj-Sirjan block, Central Iran Microcontinent, and North West Iranian Plate during the Upper Triassic to Lower Jurassic. The separation of these continental blocks caused sedimentation differences during that time. The North Tabriz and Nain-Baft Faults are probably the boundary between the Sanandaj-Sirjan Zone and Central Iran. The basin between the Sanandaj-Sirjan Zone and the Central Iranian block (the Iranian Microcontinent and North West Iranian Plate) closed in the Late Cretaceous. After that, these terranes experienced similar geological evolution, especially from the Oligocene to the Miocene.