Petrography, Geochemistry and Geocronology study of of Mesozoic Volcanism in Abarkoh Region, Sanandaj-Sirjan Zone

The study area is located near Abarkoh city and in Sanandaj –Sirjan zone. The volcanic activity of this region is in the form of dacite and rhyolite domes and lava flow and in the petrographic studies includes coarse plagioclase, quartz and hornblende. The volcanic rocks are considered as the separate units interlayered with calcareous sedimentary units. Geochemical classification confirms the rhyolitic and dacitic composition of the volcanic unites and show their belonging to the calc-alkaline magmatic series, which is the characteristic of the subduction tectonic setting. Significant characteristics observed in spider and multi-element diagrams, such as their enrichment in LREE, high LREE / HREE ratio, Nb and Ti trough, and enrichment of Pb, Rb and Th elements demonstrate the continental crustal contribution to the development of the volcanics and their formation in the subduction environment in the active continental margin setting. Tectonic setting diagrams confirm this idea and determined a continental arc setting for the volcanic rocks of the area. The dating studies on zircon minerals yield the age of about 17.7.2 ± 7.6 ma equivalent to Jurassic for this part of the Sanandaj-Sirjan zone, which matches with the subduction stage of the Neotethyan Ocean below the central Iran zone.