Eybek graniti (Biga yarimadasi, KB Anadolu) üzerine: Yeni jeokimya verileri işiǧinda yeni bir deǧerlendirme

The Tertiary magmatic activity in NW Anatolia postdates the continental collision between the Sakarya and Tauride-Anatolide continental fragments during the Late Cretaceous to Early Tertiary period. This magmatism produced mainly granitic plutons and andesitic volcanic rocks. The Eybek granite, which crops out in Biga Peninsula, is one of the representative plutons, and is Late Oligocene-Early Miocene (21-26 Ma) in age. It is an epizone granite which was emplaced into the shallow levels in the crust (∼1.5 km). Eybek granite formed contact metamorphism around its periphery. Magmatic temperature is calculated as 728-775 °C. The Eybek granite shows close relationships with dioritic hypabyssal rocks and andesitic-dacitic volcanic rocks in space and time, and may be considered a "subvolcanic pluton". It is formed from four types of rocks on the basis of their petrographic, geochemical and petrological aspects; granite, granodiorite-quartz diorite, mozonite-quartz monzonite and cataclastic granodiorite. Geochemically, it is metaluminous and subalkaline in nature and has medium to high-K calc-alkaline compositions. They show enrichment in large-ion lithophile elements (LILE) and depletion in Nb, Ta, P and Ti indicating a subduction zone-related magmatic signature for their origin. Trace element, REE compositions, interelement ratios and isotope data indicate collectively that the Eybek granite originated from hybrid magma(s) including mantle and crustal components. The geological evolution of NW Turkey indicates that the Eybek granite developed during a particularly critical time span between the slab beak-off event (Middle-Late Eocene) and exhumation of the Kazdaǧ core complex.