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    Early Variscan magmatism along the southern margin of Laurasia: geochemical and geochronological evidence from the Biga Peninsula, NW Turkey
    (Springer, 2017) Sengun, Firat; Koralay, O. Ersin
    Massive, fine-grained metavolcanic rocks of the CamlA +/- ca metamorphic unit exposed in the Biga Peninsula, northwestern Anatolia, have provided new Carboniferous ages and arc-related calc-alkaline petrogenesis constraints, suggesting that the Biga Peninsula was possibly involved in the Variscan orogeny. The metavolcanic rocks are mainly composed of metalava and metatuff and have the composition of andesite. Chondrite-normalized REE patterns from these rocks are fractionated (La-N/Yb-N 2.2 to 8.9). Europium anomalies are slightly variable (Eu/Eu* = 0.6 to 0.7) and generally negative (average Eu/Eu* = 0.68). The metavolcanic rocks have a distinct negative Nb anomaly and negative Sr, Hf, Ba, and Zr anomalies. These large negative anomalies indicate crustal involvement in their derivation. Tectonic discrimination diagrams show that all metavolcanic rocks formed within a volcanic arc setting. Zircon ages (LA-ICP-MS) of two samples yield 333.5 +/- 2.7 and 334.0 +/- 4.8 Ma. These ages are interpreted to be the time of protolith crystallization. This volcanic episode in the Biga Peninsula correlates with other Variscan age and style of magmatism and, by association with a collisional event leading to the amalgamation of tectonic units during the Variscan contractional orogenic event. Carboniferous calc-alkaline magmatism in the Sakarya Zone is ascribed to arc-magmatism as a result of northward subduction of Paleo-Tethys under the Laurasian margin. Geochemical and U-Pb zircon data indicate that the Sakarya Zone is strikingly similar to that of the Armorican terranes in central Europe. The Biga Peninsula shows a connection between the Sakarya Zone and the Armorican terranes.
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    P-T-t evolution of eclogite/blueschist facies metamorphism in Alanya Massif: time and space relations with HP event in Bitlis Massif, Turkey
    (Springer, 2016) Cetinkaplan, Mete; Pourteau, Amaury; Candan, Osman; Koralay, O. Ersin; Oberhaensli, Roland; Okay, Aral I.; Chen, Fukun
    The Alanya Massif, which is located to the south of central Taurides in Turkey, presents a typical nappe pile consisting of thrust sheets with contrasting metamorphic histories. In two thrust sheets, Sugozu and GundogmuAY nappes, HP metamorphism under eclogite (550-567 A degrees C/14-18 kbar) and blueschist facies (435-480 A degrees C/11-13 kbar) conditions have been recognized, respectively. Whereas the rest of the Massif underwent MP metamorphism under greenschist to amphibolite facies (525-555 A degrees C/6.5-7.5 kbar) conditions. Eclogite facies metamorphism in Sugozu nappe, which consists of homogeneous garnet-glaucophane-phengite schists with eclogite lenses is dated at 84.8 +/- A 0.8, 84.7 +/- A 1.5 and 82 +/- A 3 Ma (Santonian-Campanian) by 40Ar/39Ar phengite, U/Pb zircon and rutile dating methods, respectively. Similarly, phengites in GundogmuAY nappe representing an accretionary complex yield 82-80 Ma (Campanian) ages for blueschist facies metamorphism. During the exhumation, the retrograde overprint of the HP units under greenschist-amphibolite facies conditions and tectonic juxtaposition with the Barrovian units occurred during Campanian (75-78 Ma). Petrological and geochronological data clearly indicate a similar Late Cretaceous tectonometamorphic evolution for both Alanya (84-75 Ma) and Bitlis (84-72 Ma) Massifs. They form part of a single continental sliver (Alanya-Bitlis microcontinent), which was rifted from the southern part of the Anatolide-Tauride platform. The P-T-t coherence between two Massifs suggests that both Massifs have been derived from the closure of the same ocean (Alanya-Bitlis Ocean) located to the south of the Anatolide-Tauride block by a northward subduction. The boundary separating the autochthonous Tauride platform to the north from both the Alanya and Bitlis Massifs to the south represents a suture zone, the Pamphylian-Alanya-Bitlis suture.
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    Petrography and geochemistry of paragneisses in the Cine submassif of the Menderes Massif, western Anatolia
    (Tubitak Scientific & Technological Research Council Turkey, 2006) Senguen, Firat; Candan, Osman; Dora, O. Oezcan; Koralay, O. Ersin
    The Menderes Massif, which covers a large area in western Turkey, is made up of Pan-African basement rocks and a Palaeozoic to Early Tertiary cover sequence. The study area is located in the Dalama and Hallaclar (Aydin) area, in the northern and central parts of the Cine submassif of the Menderes Massif. The oldest units of the Pan-African basement are metaclastics, consisting of paragneisses and mica schists that gradually and conformably overlay paragneisses. Macroscopic appearances and mineralogical and textural data indicate that paragneisses can be subdivided into four subgroups. These are: ( 1) black spotted, ( 2) white spotted, ( 3) massive, grey-coloured and ( 4) massive, purple-coloured paragneisses. Geochemical data show that the spotted and purple-coloured paragneisses are characterized by high alumina content that is consistent with high sillimanite content. Paragneisses exposed in the eastern part of the Cine submassif were partly migmatized during the last stage of the polyphase Pan-African metamorphism. Based on comparison with relics of upper amphibolite to granulite (?) facies parageneses in the Pan-African basement of the Menderes Massif, we infer that the porphyroblasts in the black-spotted paragneisses are pseudomorphs after cordierite. Considering the inferred replacement of cordierite by sillimanite + garnet + biotite, it can be concluded that former high-temperature assemblages were overprinted by almandine-amphibolite facies metamorphism. Geochemical data obtained from paragneisses and mica schists reveal that the protoliths of this metaclastic sequence were derived from a cratonic provenance. The paragneisses are intruded by 550 Ma syn- to post-orogenic orthogneisses. Based on the well-preserved the original intrusive contact relationship with the orthogneisses and the youngest detrital zircon ages in paragneisses, it can be inferred that the time of deposition of their protolith is Late Proterozoic.