Abstract
The Gonen granitoid is exposed in the western Sakarya Zone and is overlain unconformably by a Jurassic succession. The medium to coarse-grained Gonen 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 Gonen 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 Gonen granitoid. Magmatic zircons have negative eHf 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 Gonen granitoid.
Highlights
Granites are principally produced by the partial melting of crustal rocks and are crucial components of continental regions and include important information about the nature of ancient continental crust, tectonic and petrogenetic processes occurring during continental growth, mantle–crust interaction, and contemporaneous ore deposits in distinct tectonic settings (e.g., Hawkesworth and Kemp, 2006; Kemp et al, 2007; Gill, 2010; Brown, 2013; Lu et al, 2017)
The Gönen granitoid is a small outcrop located in the western Sakarya Zone and unconformably overlain by Jurassic sedimentary rocks
TDM model ages (1811–1489 Ma) calculated from the Hf composition of zircon grains indicate that the age of recycled crust could be Mesoproterozoic/Paleoproterozoic
Summary
Granites are principally produced by the partial melting of crustal rocks and are crucial components of continental regions and include important information about the nature of ancient continental crust, tectonic and petrogenetic processes occurring during continental growth, mantle–crust interaction, and contemporaneous ore deposits in distinct tectonic settings (e.g., Hawkesworth and Kemp, 2006; Kemp et al, 2007; Gill, 2010; Brown, 2013; Lu et al, 2017). Classification, magma sources, the mechanism of crust–mantle interactions, and tectonic settings are among the most controversial issues for granite petrology. The U-Pb-Hf isotopic characteristics of zircon, occurring as an accessory phase in granitic rocks, can supply useful contributions to the solution of these conflicting issues. The purpose of this paper is to determine crystallization age and source region characteristics during partial melting
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