Evolution of the Central Iranian basement

Abstract

Most of the Infracambrian–Lower Paleozoic sedimentary rocks occurring in Iran cover a crystalline basement. In Central Iran, and the Saghand region along the Chapedony and Poshte Badam faults, the basement complexes show structural vestiges of Precambrian deformational, depositional, erosional, metamorphic and magmatic events. In this region, the basement complexes contain the Chapedony, Poshte Badam, Boneh Shurow and Tashk formations. The prevailing metamorphism, from low grade to high grade, is pre-Pan African Orogeny (i.e. from 2400 to 570 Ma). The presence of greenstone belts, a paleo-suture zone and ophiolitic rocks (i.e. from 2100 to 1500 Ma) around the high-grade metamorphic rocks of the Chapedony Formation, provide evidence that cratonization forming the Iranian basement occurred during the Paleo- and Mesoproterozoic. After formation of the basement complexes, metamorphism of the Precambrian formations and establishment of the Arabo–Iranian coherent platform at the end of Pan African Orogeny, Central Iran broke up during a Neoproterozoic–Early Cambrian extensional tectonic regime. Infracambrian–Phanerozoic sedimentary rocks were then deposited on the basement complexes. The Iranian basement complexes are extensively overprinted by Pan African Orogeny and younger igneous events.