TAVŞANLI ZONE: THE NORTHERN SUBDUCTED MARGIN OF THE ANATOLIDETAURIDE BLOCK

Indexed In

Volume 142 / 2011

Authors:

Aral I. OKAY

Keywords:

Tavşanlı Zone, blueschist, ophiolite, northwest Turkey, subduction

Abstract:

The Tavşanlı Zone constitutes the northern margin of the Anatolide-Tauride Block that has undergone high pressure-low temperature metamorphism during the Cretaceous. It is bounded in the north by the İzmir-Ankara suture and in the south by the rocks of the Afyon Zone. The Tavşanlı Zone is subdivided into four tectonic units. At the base there is the Orhaneli Group, which shows a regular stratigraphic succession that has underdone metamorphism at ~24 kbar pressure and 430-500 °C temperature during the Late Cretaceous (~80 Ma). From the base upward the Orhaneli Group consists of micaschist, marble and metabasite-metachertphyllite, and is tectonically overlain by ophiolitic mélange or directly by ophiolite. The ophiolitic mélange consists of basalt, chert, pelagic shale and limestone, and has undergone an incipient blueschist facies metamorphism. The ophiolite constitutes the topmost member of the tectonic stack. It consists mainly of peridotite (>%90) with minor gabbro and pyroxenite, and is cut by isolated diabase dykes. In the western part of the Tavþanlý Zone all these tectonic units are intruded by Lower to Middle Eocene granodiorites, and in the eastern part of the Tavþanlý Zone the blueschists and ophiolite are overlain by Lower Eocene marine limestones. The northern margin of the Anatolide-Tauride Block was buried in an intra-oceanic subduction zone during the Campanian and Paleocene underwent HP/LT metamorphism. The blueschists were exhumed during ongoing subduction and prior to continental collision through a thrust fault at the base and a normal fault at the top. In terms of tectonic setting and the timing of the geological events, the Tavşanlı Zone exhibits close similarities to the Semail ophiolite and the underlying blueschists.