Abstract

• Padatgyaung-Myinmahti area is located 80km E from Nay Pyi Taw and lies at the eastern margin of the Shan Plateau. W -Sn-Mo mineralization is spatially associated with the biotite granite of Early Eocene age and low-grade metasediments of Carboniferous to Early Permian Mergui Group. The biotite granite is slightly weathered and intensively greisenized in some places. Quartz veins generally trendN-S and NE-SWwith steep dipping (80°-90°). Cassiterite is common in greisenized zone whereas wolframite and molybdenite is prevalent in quartz vein. Greisen is mainly composed of quartz and muscovite with rare fluorite. The quartz veins contain wolframite and molybdenite associated with the minor amount of galena, pyrite, chalcopyrite, sphalerite, arsenopyrite, bismuthinite, cassiterite, scheelite, bornite and covellite. Wolframite composition ranges from hubneritic to ferberitic composition. Geochemical data indicates that the granites are peraluminous and highly fractionated, and characterized by high SiO2and high A/CNK [molecular Al2O3/ (CaO+Na2O+K2O)] values(>1.1). The granite has tectonic affinities with WPG (within-plate granite) or post-orogenic setting. Trace element geochemistry, distinct negative anomalies of primitive-mantle normalized Ba, Sr, Ti, Nb and the positive Pb, Rb, Y anomalies reveal that distinct crustal sources have been involved in the formation of granite and associated W-Sn-Mo mineralization.