Akademik Veri Yönetim Sistemi
BULLETIN OF THE MINERAL RESEARCH AND EXPLORATION, cilt.161, ss.81-99, 2020 (ESCI)
Gokceada Island, which is situated west of Biga Peninsula, has widespread magmatism with variable ages. Lower-Middle Eocene Dagicitepe volcanics are the oldest volcanic unit in the island and consist of lavas, tuff-tunes. They are influenced by alteration and almost all minerals, except quartz, are transformed into other minerals. Lower Oligocene Gokceada 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 Eselek volcanics, which occur as lavas and pyroclastic rocks, exhibit hypocrystalline porphyric and intersertal textures. They are composed of plagioclase, hornblende and clinopyroxene crystals. Rhyolitic Dagicitepe volcanics and andesitic Gokceada lava/domes have calc-alkaline, andesitic Eselek volcanics have tholeiitic character. They have geochemical features similar to subduction-related magmas. Lower-Middle Eocene Dagicitepe volcanics are the products of syn-collisional magmas that have undergone processes of crustal contamination due to thickened crust. Whereas, Lower Oligocene Gokceada andesitic lava/domes are the products of post-collisional magmas and were derived from metasomatized lithospheric mantle. Middle Miocene Eselek volcanics were also derived from lithospheric mantle but, the mantle source generating Eselek volcanics were relatively depleted over time. Geochemical data demonstrate the decreasing role of subduction signature and crustal contamination during the genesis and evolution of Gokyeada volcanics from Lower-Middle Eocene to Middle Miocene.