Geochemical characteristics of the Eocene Karataş volcanics (Northeast Sivas, Turkey) in the İzmir-Ankara-Erzincan Suture Zone

Abstract

Karataş volcanics, is the product of Eocene volcanics crop out in the form of two belts alongthe northern and southern boundaries of the İzmir-Ankara-Erzincan Suture Zone. According togeochemical data, these volcanics have alkaline basic-intermediate character and consist of basaltictrachyandesite, trachyandesite and trachyte. This volcanic activity has been controlled by fractionalcrystallization and crustal contamination from basaltic trachyandesite to trachyte. Orientation of thesamples towards amphibole area on the Rb/Sr - Ba/Rb ratio diagrams, dispersion of the Zr/Ba ratios(0.08 - 0.33) in the lithospheric mantle range, increase in the Ba/Rb ratio, decreases in the MgO, Niand Cr contents point out that this volcanism originated from enriched lithospheric mantle ratherthan asthenospheric mantle. Geochemical data show that this enriched lithospheric mantle materialis upper continental crustal material, main part of enrichment resulted by the subduction relatedfluids and also the contribution of the sedimentary materials. This situation may be explained that;the melts, derived from N-MORB or OIB bearing material ascended into the continental crust in apre-collisional period and were reactivated by extensional tectonic and/or delamination processesduring the post-collisional period, possibly caused the partial melting within the upper continentalcrust and produced the Karataş volcanics.