Abstract

• According to field and petrological characters, the metasedimentary rocks of the study area consist of slate, phyllite intercalated with quartz mica schist and quartzite. The mineral assemblages of the Bilin area had been subjected to two types of metamorphism; regional metamorphism reinforced by local contact metamorphism. Regional metamorphism of pelitic rocks gave rise to the formation of slate and phyllite intercalated quartz mica schist. Generally, the grade of metamorphism increases gradually towards the west. The regional metamorphism was superimposed by contact metamorphism by the emplacement of igneous intrusion especially biotite granite and diorite intrusion. Furthermore, the presences of spotted phyllites are the indication of the existence of contact metamorphism. The grain size becomes coarser with increasing in grade of metamorphism such as in slate, phyllite and schist. According to the mineral assemblages, the regional metamorphism of the study area had taken place within the “Greenschist facies”. Greenschist facies results from low temperature and pressure condition and the formation of some minerals indicate a temperature of approximately 250˚C to 400˚C and depth of about 2kb to 4kb. The metamorphic rocks of the study area belong to the Mergui Group. The metamorphism of the study area probably took place Post Carboniferous in age.