Abstarct: The Abbasabad volcano-sedimentary belt in the east of Shahrood includes a sequence of basaltic-andesitic rocks and related pyroclastics along with interlaxyers of sedimentary rocks with Eocene age, which is located in the northeastern edge of Central Iran structural zone. Compositional range of volcanic rocks includes olivine basalt, trachybasalt, trachy andesybasalt, trachyandesite and andesite with hyallomicrolitic porphyry, microlitic porphyry, glomeroporphyry, trachitic and sieve textures. The main minerals of the rocks are clinopyroxene and plagioclase and their’s minor minerals are olivine and amphibole. Pyroxene and plagioclase compositions range from diopside to augite (Wo43-48 En37-45 Fs10-19) and andesine to bytownite (An84.33-An28.14) respectively and Fe-Ti oxides are titanomagnetite and magnetite. Clinopyroxene compositions and whole rock chemistry indicate calc- alkaline-alkaline nature, high oxygen fugacity and basaltic composition of the mantle derived magma in an extensional intra-arc setting from partial melting of an OIB mantle source. Application of geothermobarometry calculations on clinopyroxene indicate a temperature range of 1100-1150 Cº in pressures of 2-15 Kb for crystallization of the magma in 3 magma chambers in mantle-crust boundary (45 Km depths), middle crust (27-30 Km depths) and upper crust (12-15 Km depths).