Abstract

• Tin-tungsten mineralization in the Mawchi Sn-W region, Myanmar, is predominantly confined to an Eocene granite and Carboniferous to Early Permian sedimentary and metasedimentary rocks. Apart from the other deposits of the region, stannite-kesterite is the major tin mineral of the Mosakhee, where Sn-W bearing quartz veins cut the metasediments sub-vertically. Stannite kesterite and wolframite, the major ore minerals of the Mosakhee, are associated with galena, sphalerite, hematite, raspite, cassiterite, and pyrite. The homogenization temperature (Th) of vein quartz ranges between 215 and 300 ˚C, corresponding to salinities of less than 10 wt% NaCl equiv. The calculated temperature from the stannite-kesterite and sphalerite pair also coincides with the vein-filling temperatures resulting from fluid inclusion microthermometry. The δ34S values of stannite (3.6 - 4‰) and galena (4.6 - 6‰) indicate the homogeneous sulfur source. The δ34S values of galena are heavier than those of the Mawchi deposit, implying a likely different sulfur source derived from the country rocks. A brief account of oxygen isotope reveals that δ18OH2O calculation of ore fluid at 280 ˚C is 2.9‰ to 4.8‰, suggesting the ore fluid is mainly composed of meteoric water.