PT Condition of deformation in Azna mylonitic granite (Sanandaj-Sirjan zone), based on Quartz and Feldspar microstructures

The study area consists of deformed and sheared granite – gneiss rock units, located in the northwest of Azna in Lurestan province as a part of Sanandaj-Sirjan metamorphic. Azna mylonitic granite (zircon U–Pb age: 568 ± 11 Ma) has a wrapped lens shape, extended in a NW-SE direction with a width of 1.5 km and a length of over 18 km. The average strike of mylonitic foliation varies from NW-SE in the central and western part to NE-SW trend in the south eastern part of study area and the dip of mylonitic foliation varies from 30-70 degrees to the northeast and south east, respectively. The pitch angle of stretching lineation is about 40 degrees from northwest and wide spread value in the south eastern part. The architecture of the variation of mylonitic foliation and lineation resemble a large asymmetric drag fold that is consistent with the dextral shearing. In this study, 34 thin sections have been prepared perpendicular to foliation and parallel to stretching lineation in different part of study area to study of quartz and feldspar microstructures in order to estimate the temperature and pressure of deformation. Quartz microstructures changes from BLG to mainly SGR-GBM dynamic recrystallization with increasing in temperature and decreasing of strain rate and Feldspar crystal plastic deformation maximum reach to SGR dynamic recrystallization These evidences of Quartz and Feldspar crystal plastic deformation beside together represent 500-600°C temperature of ductile deformation and medium grade of mylonitization during dextral transpressional shearing.