Abstract
Pelitic metamorphic rocks from Pranburi have mineral assemblage of Grt+Sil+/-Crd+Bt with rare andalusite. The presence of tourmaline showing two growth stages and retrograde dumortierite suggest that intrusion of the tourmaline-bearing leucogranite that crosscut the foliation of metamorphic rocks may have caused the retrograde metamorphism by infiltration of boron-bearing fluid. Metagranite from Hua Hin has Grt+Sil+Bt assemblage. The peak metamorphic condition of these two areas probably exceeded the stability limit of Ms+Qtz. The metamorphic grade increases from Hub Kapong at the NW, where Bt+Ms assemblage is found, to Pranburi at the SE. Because of the strong retrograde metamorphism, age determination utilizing zircon and monazite would be important to constrain the timing of metamorphism.
