Magmatic evolution of the Early Pliocene Etrusk stratovolcano, Eastern Anatolian Collision Zone, Turkey

Abstract

The Pliocene Etrusk stratovolcano, located in the northeast of Lake Van (Eastern Anatolia; Turkey), is one of the important volcanic centres in the Eastern Anatolian collision zone. Mt. Etrusk overlies a widespread volcanic plateau, consisting of basaltic and hawaiitic lavas formed by fissure eruptions between 4.9-4.5 Ma. These basic lavas contain a phenocryst phase consisting of olivine, plagioclase and clinopyroxene. Trace element ratio diagrams imply that these basic magmas were generated from a mantle that contained a clear subduction component that is related to the subducted sediments rather than fluids or altered oceanic crust. Results of the melting models on the basaltic plateau lavas indicate that there was a marked variation both in the mantle source mineralogy (i.e. the ratio of garnet peridotite to spinel peridotite in the source varies between 60/40% and 40/60%) and the degree of melting (i.e. F between 0.8-4%). This can be explained by a model in which magmas were generated by partial melting of both metasomatised lithospheric and deeper asthenospheric mantle sources in an extensional setting in response to the partial delamination of the lithospheric mantle of Eastern Anatolia and then mixed with each other during Pliocene times.