THE CONSECUTIVE CLOSURE PHASES OF THE IAPETUS, RHEIC AND PALAEO-TETHYS IN THE ISTANBUL ZONE: U-PB AGES FROM CROSS-CUTTING DYKES
We offer field and U-Pb age data linked to variously oriented dykes cross-cutting some of these units. The Demirci paragneiss is intruded by N800E trending dacite dykes (485.7±3.6 Ma) and N150W trending dacite dykes (443.0±5.4 Ma) with a collisional tectonic setting; N60E trending basaltic andesite dykes (301±1.6 Ma), N750E trending granite dykes (262.9±3.4 Ma), N800W trending andesite dykes (261.4±1.7 Ma) with subduction signatures. The Yellice meta-volcanics are intruded by N400-500E trending basalt dykes (268.2±2.4 Ma) with a subduction signature. N180E trending basaltic andesite dykes (318±16 Ma) with a subduction signature crosscut the Yılanlı Formation.
The Cambro-Ordovician and Ordovician-Silurian ages suggest events linked to the Caledonian Orogeny, first and second closure phases of the Tersseyre-Tornquist Sea- a branch of the Iapetus. The Ordovician-Silurian age is also in agreement with interbedded volcanoclastics rocks of andesitic and trachytic compositions in the sandstone-siltstone of the Gözdağ Formation having a lower age of Darriwilian and an upper age of Telychian. The Upper Carboniferous ages are related to the Variscan Orogeny-late closure phase of the Rheic, and the Permian ages are associated with the Hercynian Orogeny-initial closure phase of Palaeo-Tethys.