Geochemical features and petrogenesis of Gökçeada volcanism, Çanakkale, NW Turkey

Abstract

Gökçeada Island, which is situated west of Biga Peninsula, has widespread magmatism withvariable ages. Lower-Middle Eocene Dağiçitepe volcanics are the oldest volcanic unit in theisland and consist of lavas, tuff-tuffites. They are influenced by alteration and almost all minerals,except quartz, are transformed into other minerals. Lower Oligocene Gökçeada andesitic lava/domes exhibiting hypocrystalline porphyric texture, are the products of NE-SW trending domes/cryptodomes. The phenocrysts assemblages consist of plagioclase, hornblende, clinopyroxene ±biotite and quartz. Middle Miocene Eşelek volcanics, which occur as lavas and pyroclastic rocks,exhibit hypocrystalline porphyric and intersertal textures. They are composed of plagioclase,hornblende and clinopyroxene crystals. Rhyolitic Dağiçitepe volcanics and andesitic Gökçeadalava/domes have calc-alkaline, andesitic Eşelek volcanics have tholeiitic character. They havegeochemical features similar to subduction-related magmas. Lower-Middle Eocene Dağiçitepevolcanics are the products of syn-collisional magmas that have undergone processes of crustalcontamination due to thickened crust. Whereas, Lower Oligocene Gökçeada andesitic lava/domes arethe products of post-collisional magmas and were derived from metasomatized lithospheric mantle.Middle Miocene Eşelek volcanics were also derived from lithospheric mantle but, the mantle sourcegenerating Eşelek volcanics were relatively depleted over time. Geochemical data demonstrate thedecreasing role of subduction signature and crustal contamination during the genesis and evolutionof Gökçeada volcanics from Lower-Middle Eocene to Middle Miocene.