Quaternary Syn-collision volcanism in north of the Sanandaj-Sirjan zone, magmatism within an active orogenic plateau


تهران- میدات آزادی- خیابان معراج- سازمان زمین شناسی کشور


The Quaternary volcanism from north of Sanandaj-Sirjan zone, in the west of Iran is a part of widespread series of the Quaternary syn-collisional magmatism in the Turkish- Iranian high plateau. This plateau is a part of the active Arabian-Eurasian collision zone. The basic lavas (basanites, hawaiites and alkali basalts) were erupted with main trend (NW-SE) of the Bitlis-Zagros Suture. Most of the basic lavas from the study area (Qorveh-Bijar region) show enrichment in the large ion lithophile elements (LILE, e.g., Rb, Ba, Sr) and light rare earth elements (LREE), the Takab basaltic rocks have lower LREE. The La/Nb ranging for all of the lavas is >1. Sr- Nd isotope ratios of these basalts reflect mantle source characteristics. The negative Nb anomaly and fractionation of LILE in these rocks may be depending on fractionation of minerals (Amphibole, Rutile) in the source. The geochemical characteristics suggest that, these rocks could be developed from small melting of thick Eurasia lithospheric mantle underneath the Turkish-Iranian plateau. The lithosphere delamination or slab break-off mechanisms in the study area with this thickness (~150-200 km) from metasomatised lithospheric mantle could not be the causes for partial melting of this mantle and finally ascent the magma in the study area. The generation of the Kurdistan lava is related to the melting of metasomatized mantle beneath this area which is an indication of subduction of Tethys underneath Eurasia prior to collision.