40Ar-39Ar ages and petrogenesis of middle Eocene post-collisional volcanic rocks along the Izmir-Ankara-Erzincan suture zone, NE Turkey

•Two different middle Eocene volcanic episodes studied in terms of petrology and geochronology.•Relationship of mantle metasomatism and alkaline volcanism revealed.•Magma genesis in post-collisional setting controlled by melting of veined metasomatized peridotitic mantle.•Assimilation, fractional crystallization and magma mixing coevally operated during magmatism.