Petrology, geochemistry and geochronology of SW Mayamey granitoids

Granitoid plutons of SW Mayamey (60 Km east of Shahrood), located at the most northern margin of the central Iran structural zone, have granite composition (in general) and calk alkaline and peralouminous nature. In spite of coverage of these granitoids by Late Triassic – Early Jurassic sedimentary rocks, Late Neoproterozoic host gneiss are exposed in limited areas. These granitoids invaded by two series of the Late Neoproterozoic and middle Jurassic diabasic dikes. Although post – Liass, Pre- Dogger, younger than Jurassic and older than Cretaceous ages are considered for these granitoids, but for the first time U–Pb age dating on separated zircons indicates Late Neoproterozoic age (Late Ediacaran) (545±10 Ma) for them and they are a part of very ancient basement rocks of Iran. The studied rocks are similar Band -e-Hezar Chah, Sefid Sang, Delbar, Shotor Kuh, Reza Abad and Do Chah granitoids in age. Mayamey granitoids are resulted from partial melting of metapelites and metagraywackes, and they belong to S-type granioids. SW Mayamey granitoids were generated in a collisional tectonic setting in the Late Neoproterozoic, in relation to closing of intracontinental back arc basin and then metamorphism of the associated rocks from greenschist facies to amphibolite and rarely granulite facies, which finally companied with s-type granitization