New evidence of the Oligocene- Miocene closure of Neo-Tethys from the NWSanandaj- Sirjan zone, Iran

In the view of global plate tectonic reconstruction, Iran is a part of the Alpine-Himalayan folded range which is formed in relation to closure of the Tethys Ocean between two huge continents of Gondwana and Eurasia. There have been many studies concerning the formation and closure times of the Neo-Tethys, therefore different opinions have been presented in this regards. In the previous studies, the ages of closure of the Neotethys and collision of Arabian and Iranian continents have been considered to be from the Late Cretaceous to the Neogene. Based on the U/Pb zircon data from the leucosome of the mac migmatites, and the 206Pb/238U age for migmatization processes in the Takht-e-Soleyman metamorphic complex, it is determined to be about ca. 24-32 Ma (corrected for 204Pb) and 25-29 Ma (corrected for 207Pb), corresponding to the Neotethys continental collision. In this regards, it can probably consider the extensive magmatic activities in the area in relation to Neogene extensional phases corresponding to the crustal thinning followed by the continental collision. The isotopic K-Ar data on shists from the Zarehshoran area, U-Th/He data on apatites from the Mahneshan area and 4 0Ar –39Ar isotopic ages on muscovite from pelitic shists from the previous studies support uplifting of the Takht-e-Soleyman metamorphic basement ca. 20 Ma (Early Miocene). Shortening of the crust and deepening of the Zagros thrust fault (probably to Moho depth) are more evidences for Miocene continental collision.