Cimmerian evolution of the Central Iranian basement: Evidence from metamorphic units of the Kashmar–Kerman Tectonic Zone

Abstract

The Kashmar–Kerman Tectonic Zone (KKTZ) is an arcuate zone located between the Tabas and Yazd blocks in Central Iran. Detailed structural analysis and mapping of the metamorphic basement rocks of the KKTZ on the Boneh-Shurow, Tashk, Saghand and Sarkuh Metamorphic Complexes, as well as 40Ar/39Ar cooling ages on the Boneh-Shurow Metamorphic Complex indicate three deformation stages in the tectonometamorphic evolution of the KKTZ during the Cimmerian orogeny. The D1–1 event corresponds to continental accretion through the progressive formation of dextral shear zones, which is equivalent to an Early Cimmerian event during Late Triassic–Early Jurassic times. The D1–2 event is characterized by top-to-NE normal shear zones due to syn-collisional exhumation within the KKTZ and is considered to be a Mid-Cimmerian Middle Jurassic event at ca. 168Ma. The progressive regional compressional deformation is continued by the D2–1 and D2–2 events through formation of reverse shear zones and faults, with their SW movement. The progressive D2 event is considered to be Late Cimmerian and has taken place during Early Cretaceous. It is proposed that the mapped long-lived dextral shear zones within the KKTZ acted as block bounding faults between the Tabas and Yazd blocks in Central Iran.