Petrography, mineral chemistry, petrochemistry and petrology of the Reşadiye (Tokat, Turkey) area pliocene-quaternary volcanic rocks

In this study, the new petrographic, major and trace element abundances and mineral chemistry data of Pliocene-Quaternary aged volcanic rocks outcropping in limited areas in the south of the Eastern Pontides were reported. Petrographic observations reveal that the studied volcanic rocks contain plagioclase (An5-90) + clinopyroxene (Wo2-49 En19-67 Fs11-33) + hornblende (Mg# 0.51-0.79) + opaque minerals, while the mineralogic composition of the enclaves in volcanic rocks are plagioclase (An13-46) + hornblende (Mg# 0.55-0.63) ± biotite (Mg# 0.47-0.63) ± clinopyroxene (Wo41-42 En34 Fs23-24) + opaque minerals. Besides the microlithic-phorphyritic and fluidal textures composing general texture of the volcanic rocks, the sieved, corroded and zoned plagioclases, zoned and corroded clinopyroxenes and opacitized and zoned hornblendes that indicating disequilibrium crystallization are observed. MORB normalized trace element patterns of Pliocene-Quaternary aged volcanic rocks and reveal enrichment in LILE (Sr, K2O, Rb, Ba), Th and Ce and slightly depletion in Zr, Y, Nb, Ta and TiO2 and display OIB-like trace element patterns. The lack of important Eu anomaly (Eu/Eu*=0.78-1.03) indicate insignificant fractionation of plagioclase during the evolution of the magmas of Pliocene-Quaternary volcanic rocks. In the light of combined petrographic, mineral chemistry and petrochemical data, the studied Pliocene-Quaternary aged volcanics rocks were formed by mixture of the magmas derived from subcontinental lithospheric mantle source, previously enriched by subduction related fluids and/or melts in a post-collisional tectonic setting and the magmas having OIB-like character were evolved by the result of asthenospheric upwelling under effect of NAF system and undergone at polybaric crystallization conditions.