Deformation flow analysis and symmetry of Goushti shear zone, Sanandaj-Sirjan metamorphic belt, Iran

Abstract

Finite strain and vorticity analyses were carried out in the deformed conglomerate and micro-conglomerate of Goushti shear zone in the Sanandaj-Sirjan metamorphic belt (Zagros Mountains Iran). These deformed rocks are bounded between two NE and SW major thrust faults. Finite strain measurements on three principal planes of strain ellipsoid show the higher amounts of strain ratios near the major thrust faults. Strain ellipsoid shape (K-value) and strain intensity (D-value) of the Flinn diagram reveal more prolate shape of strain ellipsoid and more amount of strain intensity around the major thrust faults. According to the amounts of natural logarithmic strain (ε), mylonite and protomylonite rocks have been formed in lower and higher distances from the main basal and dorsal faults respectively. Kinematic vorticity (Wm) analysis reveals an important strain partitioning in the Goushti shear zone. Results show simple shear dominant deformation near the major thrust faults and pure shear dominant deformation far from them. The amounts of shortening were determined between 0.37 and 0.62 which shows shortening between 38 to 63%. According to the angle between lineation and intersection of the foliation and shear zone boundary (χ), triclinic symmetry was determined for the shear zone.