Folding History in Laibid Metamorphic Rocks, Sanandaj-Sirjan Zone

Laibid (northwest Esfahan) metamorphic rocks are situated in complexly deformed sub zone of the Sanandaj-sirjan zone, in which bounding faults emplaced Permian metamorphosed, beside the younger Triassic-Jurassic metamorphic rocks. Structural study of these units reveals three deformation stages of a progressive deformation in this area. The first stage includes tight to isoclinal folds, the second stage includes open to close folds and the third one includes gentle to open folds. From the first to the third stage, fold's wavelength gradually become longer, so that their aspect ratio change respectively from tall and short, for the first stage, to broad, for the second stage, and to wide, for the third one. Superposition of these fold generations caused in coaxial interference patterns. It seems that during Late Jurassic, these three folding stages consequently formed and passively rotated in a continuous deformation condition, by gradually decreasing deformation depth. Dikes alternatively injected into the extensional fractures and through the axial plane foliation and gradually deformed in to the fold, boudin, folded boudin, and boudined fold.