Özet:

In the Dağbaşı (Araklı-Trabzon) area, the Northern Zone of Eastern Pontide, petrographical, geochemical and petrological features of Late Cretaceous volcanics are investigated. Late Cretaceous volcanites are dacite and rhyolite in composition. As phenocrysts contain plagioclase, quartz, alkaline feldspar, biotite and hornblende. These volcanites show microgranuler porphyric, sferolitic and glomeraphyric textures. This volcanics have calc-alkaline in charecter, and low-medium K2O contents. Increasing in SiO2 versus Fe2O3*, Al2O3, P2O5, MgO, TiO2, Y and Zr contents show negative correlation, suggesting significant plagioclase, hornblende, biotite and Fe-Ti oxide fractionation during the evolution of Late Cretaceous volcanites. These volcanites enriched LIL elements but depleted HFS elements at the N-type MORB normalized trace element diagrams. Negative Nb and Ti anomalies indicate that subduction component and/or crustal contamination in their generation. (La/Lu)N values are between 3.20 and 6.75, show negative Eu anomalies (Eu/Eu*)=0.59-0.66. The concave REE patterns show hornblende fractional crystallizations. Based on tectonic discriminations diagrams, all samples show calc-alkaline basalt features. The whole data indicate that the Dağbaşı (Trabzon) volcanics evolved by the fractional crystallization and magma mixing±contamination of a parental magma derived from lower crust an/or upper mantle. 

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