Abstract

• The study area is situated in 27 Kilometers northeast of Myitkyina. The Nyaung Bin Tha area is built up of plutonic and volcanic units. The plutonic rocks exposed in the study area are peridotites, gabbro, granodiorite, and dolerite. The volcanic and volcaniclastic rocks include basalt, andesite, dacite, rhyolite and volcanic tuff. Almost all plutonic rocks are medium- to coarse-grained, and exhibit hypidiomorphic granular texture. Porphyritic textures, perthitic texture and myrmekitic textures are also recognized in these rocks. Ocellar texture is also observed in the samples taken from dolerite dyke. Plagioclase feldspar shows conspicuous zoning and twinning. Pyroxenes, in gabbro, occur as phenocrysts and display sector-zoned and each sector show oscillatory zoning. In basalt it shows resorbed and embayed texture, coroner or keleptic rim. Chloritization, seritization, epidotization and serpentinization are common hydrothermal alteration occurred in the study area.