Petrology and Ar/Ar chronology of Erdembaba and Kuyucak volcanics exposed along the North Anatolian Fault Zone (Eastern Pontides, NE Turkey): Implications for the late Cenozoic geodynamic evolution of Eastern Mediterranean region

Abstract

The Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt (EPOB), which geographically corresponds to the northeastern part of Turkey, is still controversial due to lack of systematic geological, geochemical and chronological data. This paper provides new geochemical and chronological data from the Kuyucak and Erdembaba volcanics exposed along the North Anatolian Fault Zone, which is one of the most seismically-active intracontinental strike-slip fault systems on the globe, in the Reoadiye (Tokat) area that is situated in the southern part of the EPOB. Kuyucak volcanics consist predominantly of basaltic rocks including mainly olivine, augite and plagioclase. Erdembaba volcanics comprise mainly dacite and minor trachydacite-trachyandesite that are composed mainly of augite, plagioclase, hornblende and rarely biotite. The Geochemical properties of the Erdembaba volcanic define small amounts of magma mixing events and it follow a linear trend from a primitive end member through to upper crustal evolution. The 40Ar/39Ar age determinations of whole rock of volcanic rock samples yielded the ages ranging from 1.33 to 6.31 Ma (late Miocene- Pleistocene). Both groups display an enrichment in LIL and LREE elements relative to HFS and HREE elements, strong negative Nb and Ti anomalies. All geochemical and Ar/Ar chronological data indicate that the late Miocene Kuyucak volcanic rocks, which are characterized by low concentrations of SiO2 (<50 wt.%), were generated by mantlederived magmas that underwent contamination processes during their transfer to the surface. Whereas, Erdembaba volcanic rocks including high concentrations of SiO2 were derived from partial melting of the plunging continental crust beneath the Eurasian plate in Pliocene, after closure of Neotethys ocean that was situated in the southern part of the EPOB.