Deformation microthermometry in the Toutak gneiss dome based on petrofabric characteristics of quartz crystal, Sanandaj-Sirjan metamorphic belt, Iran

Gneissic domes are evidence of vertical movements in both compressional and extensional tectonic regimes in orogenic systems. These domes are evidence of mutual interaction between gravitational and tectonic forces in the continental crust. Gneissic domes have unique structures in deformed regions. These domes include a complex of deformed metamorphic rocks and intrusive masses covered with the upper layers of the crust. The Toutak gneissic dome is located in the high-pressure-low-temperature Sanandaj-Sirjan metamorphic belt and is an example of gneissic domes in the Zagros orogenic system. The purpose of this research is to determine the deformation temperature based on the petrofabric characteristics of quartz minerals in the mylonite rocks exposed in the Toutak gneissic dome. The temperature obtained from the quartz c-axis pattern shows the temperature range from 260±50 to 565±50 °C for the deformation. The asymmetry of quartz c-axis patterns indicates the occurrence of dextral shear during the deformation.