The contact-metamorphosed Mesozoic rocks of the Shimanto Belt at the northern part of the Akaishi Mountains are studied in detail. Two zones, i.e. Biotite and Cordierite Zones, are distinguished for pelitic rocks. The latter is further separated into two zones, Cordierite I and II Zones.Recognition of the Cordierite I and II Zones is based on whether or not chlorite occurs in contact with white mica in the presence of cordierite.The area where chlorite occurs in contact with white mica is defined as Cordierite I Zone whereas chlorite not with white mica is Cordierite II Zone.The following reactions are proposed for each isograd on the basis of chemical, modal and paragenetic study of metamorphic minerals.(1) Formation of biotite at biotite isograd.celadonite molecule of white mica+chloritebiotite+muscovite+quartz+H2O(2) Formation of cordierite at the first cordierite isograd. chlorite+ A12O3+quartzcordierite+H2O(3) Formation of cordierite at the second cordierite isograd. celadonite molecule of white mica+chloritecordierite+biotite+quartz+H2OIn the high grade part of Cordierite II Zone, garnet commonly occurs. This part is called "Garnet Zone" in this paper. The appearance of garnet is controlled by the difference of bulk chemical composition of host rocks, i.e. garnet occurs in metapelite rich in MnO, high in (Mn+Mg+Fe+2)/(Mn+Mg+Fe+2+Al) ratio and low in Mg/Fe+z ratio. The following reactions are considered for the formation of garnet, although it is not clear which is more realistic. chlorite+quartzgarnet+H20 celadonite molecule of white mica+chloritegarnet+biotite+quartz+H20 In either case chlorite rich in Mno must have participated in the reaction.The zone of garnet+potassium feldspar which has been reported by previous studies is not recognized.