Tectonic Setting, Emplacement and Petrological Сharacteristics of the Qazan Granitoids: Evidence for the Neo-Tethyan Subduction, Urumieh‒Dokhtar Magmatic Arc, Iran

Abstract

Abstract: The Qazan granitoid pluton (South of Kashan, Iran) is situated in the central part of the Urumieh–Dokhtar Magmatic Arc. The plutonic body includes in its composition granodiorite, quartzdiorite, tonalite, and monzogranite. Granodiorite is the most predominant rock unit, which is composed of quartz, plagioclase, K-feldspar, hornblende, and biotite as main mineral phases. The Qazan pluton intruded into the Eocene volcano-sedimentary and Qom formation units. The Qazan pluton consists of mafic microgranular enclaves ranging from a few centimeters to meters in size. The Qazan pluton rocks with SiO2 content of 57.37 to 66.89 (wt %) are metaluminous to weakly peraluminous with A/CNK ratios of (>1.1) and show calc-alkaline I-type affinity. Primitive mantle-normalized spidergrams show enrichment of large ion lithophile elements (Rb, Ba, Th, U), as well as depletion of high-field strength elements (Nb, Ti). Field research suggested the magma ascended mainly in the NE–SW and NE–SW faults direction. The Qazan granitoids were injected along the extensional shear zones relevant to the dextral transpressional replacements. Petrographic and geochemical characteristics in combination with geodynamic evidence, offer that host rocks and associated enclaves originated by interaction between lower crust‒derived felsic and mantle derived mafic magmas in an active continental margin arc environment, during the subduction of the Neotethyan oceanic plate under the Central Iran continental crust. © 2021, Pleiades Publishing, Inc.