Study and investigation of petrology and petrogenesis of Plioquaternary volcanic rocks of northwest Iran (East Azerbaijan, West and Ardabil provinces)

Plio-Quaternary volcanic units are located in different regions of Azerbaijan in the north-west of Iran. Field observations show the placement of volcanic materials in connection with linear geo-structural structures such as fractures and main faults and the axis of young folds. The studied rocks include basalt, basaltic andesite, trachyandesite, trachyte, dacite, rhyodacite and rhyolite, which are from the calc-alkaline and alkaline magma series with high potassium. Young basaltic lavas are composed of basalt, olivine-basalt, tephrite, which belong to the alkaline magma series. The studied samples show enrichment in K, Ba, Rb, Th, U, Cs. Investigating the chemical behavior of chromium, nickel, cobalt, Ti, V and MgO against SiO2 indicates the pollution process. LREE enrichment and HREE depletion indicate that the magma of these rocks originated from the asthenosphere mantle with a garnet source and a low relative melting degree. The positive anomalies of Cs, U, Ba, Rb, and K and the low negative anomalies of Ta, Nb, and Eu in the basaltic samples can be interpreted as crustal contamination. Examining the effects of AFC shows that the contamination process played an important role in the formation of magmas. Medium acidic volcanic units are cut by lamprophyre dykes in some areas.  Examining the tectonic structures of the samples indicates volcanic arcs after the collision.