Petrographical and geochemical features of the sarihan (Bayburt) pluton

Within the context of this thesis, the time of intrusion, source area, tectonic setting of the parental magma as well as the petrogenetic processes such as fractional crystallization and magma mixing are investigated based on the petrographic and geochemical characteristics of the Sarıhan Pluton. The Sarıhan Pluton outcrops as a circular shaped body in an area of approximately 20 km2 towards the south of Sarıhan Village (Bayburt). The pluton, which emplaced in the early Eocene (53 Ma) into the continental crust, generally consists of quartz diorite, tonalite, monzonite, quartz monzonite and granodiorite. The locally observed mafic microgranular enclaves (MMA) are monzodiorite in composition, while the aplite dykes consist of granites. Mineral textures such as poikilitic, monzonitic, anti-rapakivi and myrmekitic are common in the medium- and fine-grained rocks. Negative trends observed in major and trace element contents (MgO, Fe2O3, CaO, TiO2, P2O5, La, Sr, Eu, Nb, Y, Yb) with increasing SiO2 content imply that fractional crystallization (amphibole, plagioclase, Fe-Ti oxide, apatite) and magma mixing play an important role in the formation of compositional range in the pluton. The presence of MMAs supports magma mixing. The linear trends are compatible with the mixing of magmas coming from the same origin. The geochemical features mentioned above suggest the occurrence of basic rocks in the source area. The question of whether these source area rocks are located in the lower crust or subducted oceanic crust is still a matter of ongoing debate. Stratigraphic, sedimentological and structural data, as well as the short-term compression following the Late Cretaceous and the subsequent extensional regime in the middle Eocene suggest that the Sakarya Zone has had crust thickness in the early Eocene less than 45 km. All these highlight the models such as slab breakoff or mid-ocean ridge subduction that propose partial melting of basic rocks in oceanic lithosphere.