New Findings From Sub-Ophiolite Metamorphic Rocks in Northwestern Anatolia (Gediz-Kutahya)

Abstract

The stratigraphically lowest part of the investigated area consists of metapelites, metapsammites and metarudites of Middle-Upper Triassic age, and is named as Ikibasli Formation. Ciceklikaya Formation which comprises of dolomitic limestones of Jura age conformably overlies Ikibasli Formation. All these Mesozoic aged units are tectonically overthrusted by the Muratdagi Melange with a low-angle. Muratdagi Melange composed of Neotethyan ophiolitic rocks is represented by ultramafic rocks and a melange (volcanic-sedimantary rocks) in the study area. Sub-ophiolite metamorphic rocks are tectonically located between the ultramafics and melange of ophiolites of Western Anatolia in Alp-Himalaya belt. Sub-ophiolite metamorphic rocks which form under the ophiolitic rocks and have a maximum 100 meter thicknes are represented by amphibolitic rocks in the Northwestern Anatolia. Sub-ophiolite metamorphic rocks form in the period of subduction of an oceanic litosphere in the subduction zone. The ages obtained from these rocks enable us to determine the age of a subduction of an oceanic litosphere and consequently to determine the closure age of Neotethyan Ocean. For this aim, 40Ar/39Ar age analysis was performed on hornblendes of metamorphic rocks and the plateau age of 100.7 +/- 1.3ma was determined.