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    Proterozoic ophiolites and mafic-ultramafic complexes marginal to the Istanbul Block: An exotic terrane of Avalonian affinity in NW Turkey
    (Elsevier, 2008) Bozkurt, Erdin; Winchester, John A.; Yiğitbaş, Erdinç; Ottley, Christopher J.
    Among the Proterozoic inliers in the Istanbul Block, the lowest structural levels are exposed in the Sunnice Massif, north of Bolu. Amphibolite-facies mafic and subordinate ultramafic rocks of the Cele meta-ophiolite underlie the greenschist-facies Ediacaran calc-alkaline Yellice metavolcanics, which are intruded by the similar to 565-576 Ma Dirgine granitoids. Homblende gneisses of the Cele meta-ophiolite comprise island arc metatholeiites and transitional to calc-alkaline metabasalts which, together with minor serpentinite are disposed in a broadly antiformal structure. The meta-ophiolitic rocks are therefore the oldest ophiolites in NW Turkey, and are themselves thrust on to a putative pre-existing continental margin, now represented by the metasedimentary migmatites of the Demirci gneisses, which may thus be the oldest rocks of the complex. The Istanbul Block is an exotic terrane. Unlike other western Turkish terranes, it lacks Variscan metamorphism: its different provenance, indicated by its geological record, faunal affinities, and inherited mid-Proterozoic isotopic dates, suggests a former link with Avalonian basement in England, NW Europe and the Maritime Provinces of Canada. Hence, together with other terranes now situated further east than the Avalonian terranes of NW Europe, the Istanbul Block may represent the easternmost extremities of Avalonia, which were detached during its end-Ordovician collision with the Bruno-Silesian Promontory on the SW margin of Baltica. Subsequent migration of the Istanbul Block to its present location occurred by eastward displacement by sinistral transpression along the southern margin of Baltica to a point east of the Dobrogea and south of the Scythian Platform, followed by collision with the Sakarya Block in the Mesozoic and Late Cretaceous southward displacement with the opening of the Black Sea basin. (C) 2008 Elsevier B.V. All rights reserved.
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    The geochemistry and setting of the Demirci paragneisses of the Sunnice Massif, NW Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2008) Yiğitbaş, Erdinç; Winchester, John A.; Ottley, Christopher J.
    The Demirci migmatitic quartzofeldspathic gneisses of the Sunnice Massif, exposed in the Istanbul Zone north of Bolu, have compositions that show them to be paragneisses, associated with subordinate para-amphibolites. They consist principally of metamorphosed, rather calcareous greywackes, with sediment derived from a continental arc source. They occur in the para-autochthon below a nappe pile (Cele meta-ophiolite), deformed and subjected to amphibolite facies metamorphism before the emplacement of late Neoproterozoic metavolcanic rocks later subjected to greenschist-facies metamorphism (Yellice volcanics). As they are overlain in sequence by nappes comprising sections of the Cele meta-ophiolite with ocean floor basalt and island arc tholeiite compositions respectively, the Demirci paragneisses may represent a section of the ancient continental basement on to which the meta-ophiolite was obducted during the Proterozoic.
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    The geochemistry and setting of the Demirci paragneisses of the Sünnice Massif, NW Turkey
    (2008) Yi?itbaş, Erdinç; Winchester, John A.; Ottley, Christopher J.
    The Demirci migmatitic quartzofeldspathic gneisses of the Sünnice Massif, exposed in the İstanbul Zone north of Bolu, have compositions that show them to be paragneisses, associated with subordinate para-amphibolites. They consist principally of metamorphosed, rather calcareous greywackes, with sediment derived from a continental arc source. They occur in the para-autochthon below a nappe pile (Çele meta-ophiolite), deformed and subjected to amphibolite facies metamorphism before the emplacement of late Neoproterozoic metavolcanic rocks later subjected to greenschist-facies metamorphism (Yellice volcanics). As they are overlain in sequence by nappes comprising sections of the Çele meta-ophiolite with ocean floor basalt and island arc tholeiite compositions respectively, the Demirci paragneisses may represent a section of the ancient continental basement on to which the meta-ophiolite was obducted during the Proterozoic. Copyright © TÜBİTAK.