Abstract

• The study area is bounded by the latitude 23° 22' to 23° 30' N and the longitude 94° 00' to 94° 03' E, in one inch topographic map 84-I/3. It is located about 17 miles (27 km) NW of Kalemyo, Sagaing Region and Tiddim Township of Northern Chin Hills. In this area, Mwetaung Hill lies prominently on the eastern flank of the northern Chin Hills. It conspicuosly high hill protruding from the alluvial plain is wholly built up of ultramafic rocks tectonically bounded by the highly folded Pane Chaung Group to the west. The most ultramafic rocks of the study area are completely serpentinized. Serpentinization is a widespread process in ophiolitic mantle. In study area serpentinites or serpentinized ultramafic rocks are classified into three typesof serpentinites: massive serpentinite, sheared serpentinite and cross-fibre serpentinite, based on their physical appearances and microscopic study.into type 1, type 5 and type 8. Degree of serpentinization for the study area is early to advanced stage. Serpentinite textures such as mesh texture, ribbon texture and bladed mat are found. Magnetite is present in minor amounts in all types of the rocks. Their nature and textures are important for the determination of the degree of serpentinization. Serpentinites derived from ophiolite peridotites is probably equilibrated at low temperature below about 500°C. The time of serpentinization in the study area is Early Cretaceous because it is related to the time of emplacement of the ultramafic body.