Imaging the 2–D crust and upper mantle structure of the Iranian plateau resolved by potential field and seismic data

Abstract

In this study, the crust and upper mantle density distribution across the Iranian plateau along a ~1500 km profile are investigated using an integrated modeling of potential field data (gravity, geoid and topography) and by assuming local isostatic equilibrium. Our profile is initiated in Arabian platform and running through the main geological structures of Iran including Zagros orogen, Sanandaj – Sirjan Zone (SSZ), Urumieh – Dokhtar Magmatic Arc (UDMA), Central Iran (CI) block, Tabas/Lut blocks, and East Iranian Range (EIR). In the second step, in order to verify the integrated model, the 1–D S–wave absolute velocities for the crust and upper mantle beneath 21 seismic stations which partially covered the density profile are obtained using the joint inversion of P–receiver function (PRF) and surface–wave dispersion data. Our results indicate a thick crust (~60 km) beneath the SSZ and UDMA which thinning toward the east and experienced its minimum value (~40 km) beneath the central Iran, as well as Tabas/Lut blocks. Moreover, a thick lithosphere (>150 km) is observed under the Zagros, SSZ and parts of the UDMA, whereas a thinner lithosphere (~120 km on average in velocity model) is presented under the most of our profile. Both density and velocity models indicate a lithospheric thinning toward the CI block which imply the slab breakoff or lithospheric delamination followed by the upwelling of the asthenosphere in the Neogene. The presence of a relative fast structure in the crust beneath the Tabas block which is coinciding with a shallow high velocity body in the uppermost mantle elucidates a signature of former oceanic crust, which disappeared after the collision of Lut and Afghan continental blocks and E-directed subduction of Neotethys under the Afghan microcontinent either in post-Albian or middle Eocene times.