New seismic imaging of some tectonic zones in the Iranian Plateau

Abstract

The Iranian Plateau is characterized by diverse tectonic domains, including the continental collisions (e.g. the Zagros and Alborz Mountains) and oceanic plate subduction (e.g. Makransubduction zone). To derive a detailed image of the crust–mantle (Moho) and lithosphere–asthenosphere (LAB) boundaries in some tectonically units of the Iranian Plateau, we used a large number of S receiver functions obtained from teleseismic events recorded at 68 national permanent stations (19 broadband and 49 short period stations). The S receiver functions clearly imaged the base of the crust and lithosphere and their variations within the different tectonic zones of the Iranian Plateau. Our new seismic images show a significant variation of the lithospheric thickness in the different geological features. The most complex structure was detected beneath the Zagros Mountains where the Arabian Plate is believed to underthrust beneath centralIran. We found the thickest crust under the Sanandaj-Sirjan metamorphic zone (SSZ)which proposes the overthrusting of the crust of central Iran into the Zagros crust along the main Zagros thrust (MZT), in agreement with the results of Paul et al., (2010). Furthermore, our results clearly show a shallow LAB at about 80-90 km depth beneath the Alborz, the central domain (CD) and central Iranian micro plate (CIMP) zones. Based on our results, the Arabian LAB, beneath the Zagros fold and thrust belt (ZFTB), SSZ and the Urumieh-Dokhtar magmatic assemblage (UDMA) is 200 km and may contain a dipping structure at depths ranging from 100 beneath the ZFTBto 150 km beneath the SSZ and the UDMA. This dipping structure interpreted as the presence of remnants of the fossil Neo-Tethys subduction. The location of the boundary between the Arabian and central Iranian lithospheres is beneath the UDMA, which is shifted northeastward relative to the surficial expression of the MZT.