-Abaad skarn centeral Iran, is studied to better understand the evolution of the skarn. Trioctahedral, Ca-mica occurs locally in aluminous contact marbles around Hassan-Abaad granitoid stock. Rare clintonite-Na margarite solid solution have been observed, where margarite itself formed after plagioclase. Coexisting mineral phases are calcite, clinopyroxene, spinel, garnet, forstrite, vesuvianite, wollastonite. Tow reaction between the observed phases result in clintonite formation in this zone (Fo + Cpx + Cc + Sp + H2O = Cli + CO2 and Cpx + Cc + Sp + H2O = Cli + Fo + CO2). Phase relations restricts the stability field of clintonite to relatively low chemical potential of CO2 and/ or high chemical potential of H2O. Generation of clintonite is probably related to circulation of F-rich fluids through carbonate bodies. The main source for F is introusive plutonic and relaeted hydrothermal fluid. plagioclase breakdown to margarite can explain deplation of Na2O, K2O and SiO2.The model of clintonite formation and evolution of Hassan-Abaad skarn is that the mineral assemblage in this area is experienced crystallization in an open system with F flow in releation with crystallization in a close system. In this area clintonite is formed between 620-650?C.