Thermobarometry and tectonic setting of Precambrian metamorphic basement of Central Iran in the Lakh Bargheshi area (southwest of Bardaskan, Khorasan Razavi)


1 Department of Geology, Faculty of Sciences, Imam Khomeini International University, Qazvin, Iran

2 گروه زمین شناسی دانشگده علوم پایه دانشگاه بین المللی امام خمینی


Precambrian basement of Central Iran in Lakh Bargheshi area from SW Bardaskan mainly consists of metapelite, metabasite and mylonitic gneiss and has been invaded by Lakh Bargheshi granitic body with the age of Ediacaran-Cambrian. Metapelites mostly are Garnet schist type and encompass mineralogical paragenesis of garnet + biotite + muscovite + quartz + feldspar. Metabasites contain of garnet amphibolite and garnet-epidote amphibolite and show mineralogical paragenesis of amphibole + feldspar + garnet ± quartz ± epidote± whitemica ±rutile ± sphene ±ilmenite. Metamorphic conditions that obtained by Thermocalc software, petrogenetic grids and conventional thermobarometries are compatible for both metapelitic and metabasitic units and include pressure between 7.1 until 12.3 Kb and temperature between 482 until 661°C that nearly are equivalent of high pressure amphibolite and epidote amphibolite facieses that are dominant in the lower continental crust. Epidote and garnet-bearing granitic body of Lakh Bargheshi and host metapelites and metabasites probably representing thickened continental arc induced by Prototethys subduction beneath Iran plate.