Abstract

• The ModiTaung area is located 370 km to the north of Yangon. The segment of gold mineralization is of interest as it is the first reported gold deposits of slate-hosted mesothermal quartz-gold veins (orogenic gold deposit) in Myanmar. This slate belt consists of the argillaceous rocks namely Mergui Group (Late Palaeozoic age) and which is largely intruded by many plutons. The deposit is hosted within three major vein systems. They are made up of several veins which are spatially grouped into their respective systems. Vein textures are mostly of three types; book-andribbon texture, laminated to stylolitic texture and massive texture. Mineralized shear veins tend to follow three trends within brittle-ductile regimes and occur at the centre of the shear zone (C vein) or oblique to the shear zone boundary. Book and ribbon vein textures provide evidence that mineralization took place during D2 within NNE trending shear zones. Pyrite chemistry indicates two main episodes of gold mineralization: syngenetic gold precipitation in Py1 and an epigenetic gold mineralization in Py2 and Py3. Py1 is interpreted to be of syngenetic/diagenetic origin because of its higher Ag, Ni, V contents and the ratio Au/Ag is less than 1. Py2 and Py3 are of hydrothermal origin as they have low levels of Ni, V, and Ag with Co/Ni ratio and Au/Ag more than 1. Evidence of pulsed hydrothermal mineralizing fluids is also consistent with the presence of cobalt and nickel zoned micro-bands in the pyrite structure.gold in Py1 could have been remobilized by circulation of later magmatic and metamorphic fluids and concentrated elsewhere enhancing the gold content in later generations of pyrite (Py2 and Py3).