Petrogenesis of adakitic Plio-Quaternary post collision rocks, north of Sahand volcano (NW of Iran)


Department of Earth Sciences, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran


The study area is situated in the south of Sahand volcano in the northwest of Iran. The volcanic rocks in this area are part of young activity of Sahand volcano, erupted as flow lavas and tuff or tephra units consisting of ash, punce, lapilli, agglomerate and volcanic breccia which overlay the Pliocene sedimentary units. The r composition of rocks is predominantly dacite with porphyry texture with fine grain matrix and glassy and trachyte textures. Geochemical data show that the subalkaline dacite rocks is adakitic composition and are characterized by high amount of Sr, LREE, LILE and high ratios of Na2O/K2O with differentiated pattern of REE, low ratios of HREE and Y. Depletion in Nb, Ti and HREE and enrichment in LILE and LREE are all evidences of subduction adakitic magmatism. The adakitic rocks in the study area were probably formed by slab break off and melting of oceanic isolated crust. Post collisional magmatism related to the Neotethyan subduction caused the formation of adakitic magmatic rocks in the south of Sahand and the northernmost of the Uromieh-Dokhtar magmatic zone.