Stress regime change from Miocene to pliocene -Quaternary and its relationship with structures and dykes emplacement in thd Salafchegan area Oroumiyeh -Dokhtar magmatic belt

Paleostress analysis using fault-slip data and trajectory of dykes in the Salafchegan area, west of Qom Province, has improved our knowledge on tectonic regime changes in the late Cenozoic in this portion of Oroumiyeh-Dokhtar magmatic belt. Stress trajectories drawn on the base of dykes show two direction of maximum principal stress along N-S and NE-SW. although fault-slip data analysis of 150 slickensides by MIM method proved the change of stress regime from Miocene to Pliocene in the study area. Additionally, the faulted and sheared anticline of Kharab-Sarahroud is an asymmetric Z-shape fold that cut by NE-SW left lateral strike slip faults. According to right-lateral transpression is was the active tectonic setting in the Oroumiyeh-Dokhtar belt from Miocene to present. The study area is laid between two main faults including Indes right-lateral strike slip fault to the north and Khorheh-Kahak thrust system to the south. Due to contribution of Oligocene-Miocene rock units, folding of Kharab-Sarahroud anticline has occurred in Miocene and perhaps Pliocene; when the first stress regime was active. Then by clockwise rotation stress axes, the fold was sheared and rotated to find Z-shape geometry. Finally NE-SW left-lateral faults cut the fold in Quaternary.