Identification of Two Different Phases of Metamorphosed Granitoid in Kuh-Sefid Tootak Anticline Based on U-Pb Age Dating

Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, these rocks are divided into two groups of "augen geneiss " and "metagranitoid". During the course of previous studies, these two rock groups had been attributed to a magmatic phase in Mesozoic, which experienced different degrees of deformation. In this study we proceed to determine the age of these two granitoid rock groups based on U-Pb age dating method applied on Zircon minerals. As a result, the age of orthogneiss rocks is 514±24 million years old and they belong to Cambrian, as metagranitoid rocks are 173±9 million years old and attributed to Middle Jurassic. Based on geological and structural evidences, the magmatism occurred in Cambrian was related to tension tectonics in Late Precambrian to Early Paleozoic, while the magmatism in Middle Jurassic associated with dextral transpression tectonics in the studied area.