The Eocene Zigana Granitoid in the northern zone and the Middle-Upper Eocene Dolek and Saricicek Plutons in the southern zone of the Eastern Pontides (NE-Turkey) consist of different rock series ranging in composition from intermediate to felsic compositions containing from <1% to 9% of biotite. The biotites are Mg-rich (X-Fe = Fe2+/Fe2+ + Mg) = 0.28 - 0.49) in the southern zone plutons and Mg- to Fe-rich (X-Fe = Fe2+/Fe2+ + Mg) = 0.33 - 0.78) in the northern zone pluton. They coexist with K-feldspar, plagioclase, quartz, amphibole, pyroxene, low +/- titanium magnetite, minor ilmenite titanite. Biotites have been buffered by the Ni-NiO. The plutons equilibrated under low oxygen fugacities (LogfO(2)) ranging from -16.01 to -20.23 bars for Dolek and Saricicek, and -16.70 to -17.90 bars for Zigana.