Genesis of adakitic magmatism in Sahand region, Eastern Azarbaijan


1 Department of Geology, Islamic Azad University, Shabestar Branch, Shabestar, Iran

2 Department of Geology, Faculty of Sciences, University of Tabriz, Tabriz, Iran


We present new whole rock geochemical data for the Sahand dacite and rhyolite rocks lying in the south of Tabriz, and formed during the Oligo-Miocene period, when the collision between the Arabian and the Eurasian plates occurred following the subduction of Neo-Tethys ocean during the Cenozoic. The investigated rocks were emplaced into the late Cretaceous and Eocene sedimentary, volcano-clastic and volcanic rocks. The dacite and rhyolite rocks are characterized by low Y and high Sr concentrations and highly fractionated LREE/HREE patterns, the common characteristics of slab melt-derived adakites. Geochemical studies indicate that lava flows belong to calc-alkaline magmatic series and their parent magmas have not been subjected to extensive fractionated. The highly enrichment of LREE compared to HREE, high contents of LILE relative to HFSE and significant anomalies of Nb, P and Ti suggest a subduction-related volcanism. In the trace and major elements correlation diagrams, the Sahand samples are plotted in the field of high-Si adakite. Also, the Sahand adakites show higher MgO and Mg# contents. Which is interpreted as reflecting interactions between the ascending adakitic magma and the overlying mantle wedge. These rocks belong to the post-collisional arcs. In this tectonic setting, magma ascent is controlled by strike-slip faulting and associated pull-apart extensional tectonic.