The cause of igneous activity in the Anatolia-Iranian region is not clear. This is broadly associated with Arabia-Eurasian convergence, but it could be due to subduction of continental crust, delamination of upper plate lithosphere or lower crust, or asthenospheric decompression accompanying post-collisional relaxation. We used regional synthesis to investigate likely causes. Three maps showing spatial and temporal extent of magmatism for Paleogene, Neogene, and Quaternary times were compiled from published literature. The maps reveal the record of magmatism left by the subduction of Neo-Tethys ocean crust beneath the Eurasian plate prior to collision between Arabian and the Eurasian continental lithospheres. We first tested the idea that subduction was responsible for igneous activity using variations of K with depth to the subduction zone. Because Anatolia-Iran lacks a dipping seismic zone, we plotted K vs distance to plate boundary for Quaternary igneous rocks NE of the Zagros and N of the Bitlis sutures. There is no correlation of K vs distance, implying that the igneous rocks north of both suture zones do not behave like magmas associated with an active subduction zone. This result bolsters geodetic observations suggesting that the current convergence of the Arabian plate is accommodated across the width of the Iranian block (Reilinger et al. 2006) characterized as a diffused plate boundary. Quaternary plutonic rocks from the Greater Caucasus, where convergence velocity diminishes to zero, suggests that an active plate boundary is forming north of the Caucasus-Kopeh Dagh mountains coinciding with the initiation of subduction at the Apsheron-Balkhan sill in the South Caspian Basin (Hollingsworth et al. 2010).

Hollingsworth, J., et al. (2010) Oroclinal bending, distributed thrust and strike-slip faulting, and the accommodation of Arabia–Eurasia convergence in NE Iran since the Oligocene, Geophys. J. Int., 181, 1214-1246

Reilinger, R., et al. (2006), GPS constraints on continental deformation in the Africa-Arabia-Eurasia continental collision zone and implications for the dynamics of plate interactions, J. Geophys. Res., 111, B05411