Abstract:

The Gönen granitoid is exposed in the western Sakarya Zone and is overlain unconformably by a Jurassic succession. The medium to coarse-grained Gönen granitoid has mineral assemblage of K-feldspar, plagioclase, quartz, muscovite, and biotite. Accessory phases are apatite and zircon. In this study, zircon U-Pb age is combined with Lu-Hf isotopes, which are presented to reveal the magma source and possible petrogenetic processes that took place during the formation of the parental magma for the Gönen granitoid. U-Pb dating of magmatic zircons yielded a concordia age of 336.3 ± 2.9 Ma referring to the early Carboniferous crystallization age of the Gönen granitoid. Magmatic zircons have negative εHf(t) values (-3.2 to -8.3), indicating that the granitoid magma was derived from the recycling of ancient crustal materials. TDM model ages vary in the range of 1489-1811 Ma, indicating that the crustal material involved during the early Carboniferous partial melting could be extracted from the mantle or added to the basement of the Sakarya Zone in the Mesoproterozoic/Paleoproterozoic times. Geochronological and Lu-Hf findings point to a collisional setting rather than ongoing subduction during the formation of the early Carboniferous Gönen granitoid.

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