Mid-Cimmerian, Early Alpine and Late Cenozoic orogenic events in the Shotur Kuh metamorphic complex, Great Kavir block, NE Iran

Abstract

The Shotur Kuh complex, exposed in the NE part of the Great Kavir block, is composed of amphibolite facies metaigneous rocks and micaschist, and of lower-grade Permian–Miocene cover sequences that experienced four main deformation phases and at least two metamorphic events. The D1 deformation phase is associated with a prograde metamorphism that in the basement reached amphibolite facies conditions. This Barrovian-type metamorphism with field gradient of 20–22 °C/km was related to collision-induced crustal thickening. The D2 event corresponds to post-collisional exhumational upflow of middle crust, resulting in updoming of the basement core and its top-to-the-Northwest unroofing along a low-angle detachment shear zone at the basement/cover boundary. The D1 and D2 events are considered as Mid-Cimmerian in age because they also affected the Upper Triassic–Lower Jurassic Shemshak Formation and are sealed by the Middle Jurassic conglomerates. The D3 folding event, characterised by NE–SW shortening, also affected the Cretaceous limestones, and it is sealed by Paleocene conglomerates. Considering the Late Cretaceous age of this deformation, it is related to the Late Cimmerian–Early Alpine orogeny that resulted from the Cenozoic closure of the Neo-Tethys oceanic tract(s) and convergence between the Arabian and Eurasian plates. The D4 folding event, characterised by NW–SE shortening, also affected the Miocene conglomerates, suggesting its Miocene or post-Miocene age. This deformation event is associated with Late Cenozoic convergence between Arabia and Eurasia, and it could be combined with a left-lateral activity along the Great Kavir fault-bounding system.