Petrographical, geochemical and petrological investigation of eocene volcanic rocks from the mescitli (Gümüşhane) and surrounding area

In this study, petrographical, geochemical and petrological characteristics of Eocene volcanic rocks from the Mescitli (Gümüşhane) and surrounding area were determined, and the evolution and origin of volcanic rocks were investigated. Liassic Hamurkesen Formation made of the basement in the South Zone of the Eastern Pontides. Dogger-Malm-Early Creataceous aged Berdiga Formation overlies with conformity those of this unit. Berdiga Formation are unconformably overlain by Early Creataceous Mescitli Formation. All of these units are unconformably overlain by Eocene Alibaba Formation. The youngest unit in the study area is Quaternary alluviums. Studied Eocene volcanic rocks are basaltic andesite, andesite, basaltic trachy andesite, trachy andesite, dacite and rhyolite in composition, and consists of mainly plagioclase, quartz, hornblende, augite and biotite minerals. Eocene Mescitli volcanites show calc-alkaline affinities and have low to medium K contents. They are enriched in large ion lithophile and light rare earth elements, with pronounced depleted of high field strength elements. The chondrite-normalized REE patterns (LaN/LuN=1-19) show low to medium enrichment, indicating similar sources for the rock suite. The main solidification processes involved in the evolution of the volcanics consist of fractional crystallization with minor amounts of crustal contamination ± magma mixing. All evidence supports the conclusion that the parental magma of the rocks probably derived from an enriched subcontinental lithospheric mantle, previously metasomatized by fluids. Key Words: Eastern Pontides, Eocene, Geochemistry, Mescitli Volcanics, Petrography, Petrology, Torul.