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    Petrography, geochemistry, and provenance of Jurassic sandstones from the Sakarya Zone, NW Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2019) Sengun, Firat; Koralay, Osman Ersin
    The Jurassic sandstones exposed in the western part of the Sakarya Zone are yellowish to brown, moderate to well sorted, medium to coarse-grained, grain-supported, and cemented by calcareous and minor silica. Sandstones are mainly classified as litharenite, subarkose, and arkose according to the relative proportions of quartz, feldspar and rock fragments, and major element ratios. On the SiO2 variation diagram, Na2O and K2O show slight positive correlations, which could reflect abundance of sodic plagioclase and K-feldspar with quartz within high Si-content sandstones. Sandstones generally exhibit slight LREE enrichment with respect to HREEs. The REE plots are characteristic for sedimentary rocks derived from the upper continental crust. Combining the results of several provenance discrimination diagrams, elemental ratios (Th/Sc, Zr/Sc, La/Th), and REE contents in sandstones, they reveal that the sandstones originated from intermediate to felsic source rocks. Accordingly, the probable source of the Jurassic sandstones is the crystalline basement of the Sakarya Zone consisting of Devonian, Carboniferous, and Permian granitoids, and high-grade metamorphic basement rocks. The Jurassic sandstones mostly have characteristic features of passive continental margin basins. It can be noted that the sandstones may have been deposited in a marginal basin that began to open in Early Jurassic time. CIA and CIW values for the Jurassic sandstones suggest that the source area was subject to low to moderate chemical weathering under semihumid to semiarid climatic conditions.
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    Zircon U-Pb age and Hf isotopic composition of the Carboniferous Gonen granitoid in the western Sakarya Zone of Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2020) Sengun, Firat; Koralay, Osman Ersin; Kristoffersen, Magnus
    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 Gillen 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 epsilon(HT)(t) values (-3.2 to -8.3), indicating that the granitoid magma was derived from the recycling of ancient crustal materials. T-DM 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.
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    Zircon U-Pb age and Hf isotopic composition of the carboniferous gönen granitoid in the western sakarya zone of Turkey
    (TUBITAK, 2020) Şengün, Fırat; Koralay, Osman Ersin; Kristoffersen, Magnus
    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 ?Hf(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. © TÜBİTAK.