Intrusion of the Kalaybar nepheline syenite into the Cretaceous pelitic and calcareous sediments has produced a thermal aureole up to 1km thick. Six mineralogical zones are developed in the pelitic rocks with minerals such as cordierite, K feldspar, sillimanite and corundum. Chemically suitable rocks are partially melted in response to the heat from the pluton. Five mineralogical zones are developed in the calc-silicate rocks with minerals such as tremolite, diopside, garnet, scapolite, wollastonie and vesuvianite. A petrogenetic grid was used for pelitic rocks to put constraints on pressure of metamorphism. Intersection of the reaction curves on the grid indicates a pressure of ca. 3 kbar for the contact metamorphism in the Kalaybar aureole. Calculation of the positions of the reaction curves for the calc-silicate rocks assuming unit activity for all phases, and plotting them on T-X_CO2 diagrams shows that the X_CO2 is about 0.2 and it is almost independent of pressure. Calculation of the position of the reaction curves assuming dilution of the phases due to solid-solution gives the similar results indicating that the actual composition of the fluid had a X_CO2 about 0.2 during peak metamorphic condition. The temperature was 700-750°C for sillimanite zone in pelites and 600-700°C for wollastonite-vesuvianite zone in the calc-silicates.