Characteristics and geochemistry of Precambrian ophiolites and related volcanics from the Istanbul-Zonguldak Unit, Northwestern Anatolia, Turkey: following the missing chain of the Precambrian South European suture zone to the east

Abstract

The Precambrian metamorphic basement of the Istanbul-Zonguldak Unit (IZU), NW Anatolia, Turkey, is represented by the Sunnice Group, composed essentially of four different metamorphic assemblages: (1) Cele metaophiolite, (2) Yellice metavolcanics, (3) Demirci metamorphics, and (4) Dirgine metagranite. The field relations and structural characteristics of these units were studied and representative geochemical analyses of Cele metaophiolite and related volcanics were obtained from the Sunnice, Almacik, and Arrnutlu areas. Collectively, the results are interpreted as the Cele Magmatic suite displaying disrupted components of a complete suprasubduction ophiolite. The Yellice metavolcanic sequence contains fragments of both an intra oceanic island arc and a back-arc basin association built on the ophiolite. The Demirci metamorphics, represent reworked continental fragments forming the base of the metamorphic massifs. These three different metamorphic units were intruded, after their amalgamation, by the Dirgine granitic pluton dated at 570-590 Ma [Geol. Mag. 136 (5) (1999) 579; Int. J. Earth Sci. (Geol. Rundsch) 91 (3) (2002) 469]. The metamorphic tectonic units and the metagranite are collectively overlain by a thick Lower Ordovician to Carboniferous sedimentary cover known as the Istanbul-Zonguldak succession. The collisional event which led to the amalgamation of the different tectonic entities is partly penecontemporaneous with the Pan-African orogeny supporting the view that the basement of the IZU formed a link between the Pan-African and Trans-European suture zones. (C) 2004 Elsevier B.V. All rights reserved.