Geometry and Kinematics of the Qom-Zefreh Fault System and its Significence in Transpression Tectonics

The Qom-Zefreh fault system has almost 220 km length cutting the Urumieh-Dokhtar magmatic belt in central part of Iran. According to orientation and mechanisms, it could be divided in three segments of; northwest, central and southeast. Geometry and orientation of reverse faults, and folds in the Qom-Zefreh fault system and shear kinematic indicatores including Natanz slice, reflect a strike-slip displacement to the Qom-Zefreh fault. En-echelon form of the fault segments and dextral displacement resulted in a positive flower structure in two districts of south Kashan and south Ardestan. In comparison, two depressions of north Kashan depression in northwest against the south Zefreh-Gavkhoni depression in the southeast locate at the extension areas of this strike-slip fault system. Lenticular intrusive bodies including Vash granite, reflects local extension along some segments of this strike-slip fault system. The Qom-Zefreh fault is evaluated as one of the basement faults of central Iran which was reactivated by the convergent tectonics of the Neo-Tethys. Obvious displacement of most recent alluvial fans along the Qom-Zefreh fault implies high potential to seismological activity.