Petrology and Tectonic Setting of Sahand Tertiary Volcanic Rocks (South of Tabriz)

Abstract In south of Tabriz, the Tertiary volcanic rocks have exposed in Oligocene-Miocene sedimentary deposits. The Sahand volcano is located in the NW of Iran. The volcano is stratovolcano and is dominated by pyroclastic materials and lava flows in the Miocene-Quaternary. The last eruptions included subvolcanic and volcanic domes with dacitic to rhyolitic composition. These rocks have petrological features including sieve texture and zoning in plagioclases. Common features in the young subvolcanic and volcanic rocks of the Sahand are abundance of plagioclase and amphibole, enrichment of Ba, Rb and Sr and negative Nb and Y anomalies in primitive mantle normalized multi element diagrams and enrichment of LREE relative to HREE in chondrite-normalized REE patterns. These characteristics and the location of the rocks studied in the Y-Sr/Y diagram implying adakitic composition for these rocks. Adakitic rocks of the Sahand are high SiO2 Adakitic rocks. These rocks have been derived from partial melts of garnet-bearing crustal sources (thickened lower continental crust or oceanic crust) and underwent magmatic evolution during their ascent. The formation of  studied rocks have been related to the Arabian-Eurasia collision zone.