Petrographical and Geochemical Features of Late Cretaceous Calcalkaline Volcanics Around Taşlıyayla (Çaykara, Trabzon, NE Turkey)

Late Cretaceous era is characterized by densely volcanic and granitic activities in the Eastern Pontides that is northeast part of the Sakarya Zone. In this era, thick pile of volcanic-volano-clastic rocks occurred during the activities of acidic and basic volcanic cycles. In this study, preliminary geochemical results of Late Cretaceous aged volcanic rocks that were cut by the plutons of Çaykara Intrusive Complex (Trabzon) are presented. Investigated rocks are cut by both Late Cretaceous and Eocene aged plutonic rocks; therefore, they are altered in some of the locations. They are yellowish- greenish-blackish in hand specimens and show aphanitic textures. They show microlithic porphphyric (including plagioclase porphyries) and intersertal textures under microscope. Euhedral and subhedral plagioclase crystals are anorthite 35 to 55 in composition. From the results of chemical analysis, the volcanic rocks are basalt, basaltic andesite, andesite and dacite in composition and their Mg# is ranging 30 to 65. In the primitive mantle normalized trace element diagram, the samples display negative Nb, P and Ti and positive Pb anomalies. In general, large ion lithophile (LIL) elements enriched compared to the high field strength (HFSE) elements in the same diagram. In chondrite normalized rare earth elements diagram, (La/Lu)N ratios are ranging from 4 to 15. While some samples are shown slightly negative Eu anomaly, some others show slightly positive anomaly. When the samples are plotted in tectonic discrimination diagrams, they fall in island arc volcanic fields. The main solidification processes involved in the evolution of the volcanics consist of fractional crystallization, crustal contamination ± magma mixing. In the light of all evidence supports the conclusion that the parental magma(s) of the Late Cretaceous volcanics probably derived from an enriched lithospheric mantle, previously metasomatized by subduction