Surface waveform tomography of the Turkish-Iranian plateau

Abstract

The Middle East is a tectonically complex region consisting of terrains as diverse as Precambrian shields and young orogens. The dominant tectonic feature is the Turkish-Iranian plateau, a recently elevated, seismically active region along the Zagros-Bitlis suture, which results from the collision of the Arabian Plate with Eurasia. In this study, we use surface waveform tomography to elucidate the upper-mantle shear wave velocity structure beneath the Turkish-Iranian plateau and adjacent regions. The main large-scale feature in the tomographic model is a low shear wave velocity anomaly in the uppermost mantle beneath the plateau. This low-velocity feature correlates with a long-wavelength free-air gravity anomaly and with recent volcanism whose geochemistry has a lower lithospheric mantle signature. Seismology, gravity and volcanism all suggest the presence of a thin lithosphere and warm upper mantle beneath the Turkish-Iranian plateau. The upper-mantle low shear wave velocity zone, the high free-air gravity and the deep lithospheric source depth for the basaltic volcanism are all consistent with a partial delamination of the lithosphere as a result of earlier lithospheric thickening resulting from the continental collision.