LATE CRETACEOUS ARC MAGMATISM IN THE SOUTHERN CENTRAL PONTIDES: CONSTRAINTS FOR THE CLOSURE OF THE NORTHERN NEOTETHYAN BRANCHES

Abstract

In the southern Central Pontides in northern Turkey the remnants of two Neotethyan oceanic basins, currently represented by the Intra-Pontide and the Izmir-Ankara-Erzincan sutures, and the interposing continental microplate (i.e., the Sakarya Composite Terrane) are completely dissected by the North Anatolian Shear Zone (NASZ). Within the resulting kilometre-scale, strike-slip fault-bounded blocks, several Late Cretaceous arc-type magmatic units have been detected. In this paper, we present new geochemical data from one of these magmatic units, the Yerkuyu Unit, that forms an ENE-WSW trending 30-km long and 10-km wide lens-shaped body surrounded by the splays of the NASZ. The studied igneous lithologies have a subduction-related magmatic geochemical signature matching with another lozenge-shaped magmatic block of the Tafano Unit. However, the tectono-magmatic characterization indicates that the Tafano Unit magmatism developed within a continental arc tectonic setting, while the volcanic rocks of the Yerkuyu Unit derived from oceanic arc magmatism. This finding indicates that the subducted oceanic lithosphere of the İzmirAnkara-Erzincan branch of the Neotethys Ocean produced oceanic volcanic arcs close to the subduction zone (i.e., the Yerkuyu Unit) and beneath the Sakarya continental microplate (i.e., the Tafano Unit).