Role of transpressive tectonic regime in configuration of Bibi-Maryam area in the north part of Sistan Suture Zone, eastern Iran

The sub-vertical fault planes with sub-horizontal slickenlines and correlation of these date with anisotropy of magnetic susceptibility indicates a predominantly transpressive regime including right lateral strike slip faults with reverse components in the Bibi-Maryam area. An assemblage of en-echelon and double plunge folds with slip indicators such as duplexes in their limbs confirms progressive transpressive deformation there. Accompanying hydrothermal alteration with transpression has created ideal conditions for reactivating shear fractures during late Cenozoic times that they record the last phase of tectonic activity. The sets of the shear fractures indicate an N025° direction of compression (σ1) that is compatible with the Plio-Quaternary stress; also the results of faults analysis show a N085° direction of compression (σ1) that is compatible with the middle-late Miocene in the area. Also, the granitoid bodies are exposed along faults that these faults are branches of the Nehbandan Fault System (NFS) in this area. Dextral transpressive regime activity along the NFS may have largely affected on the late Cenozoic exhumation of the granitoid bodies in the Bibi-Maryam area and thus Sistan suture zone. Field evidence indicates that exhumation of the granitoid bodies cannot have preceded Oligo-Miocen in this area.