Zircon U-Pb age and Hf isotopic composition of the Carboniferous Gönen granitoid in the western Sakarya Zone of Turkey

Abstract

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