Re-Os isotope dating of molybdenite from Shangalon Cu-Au deposit in the Wunto-Popa magmatic arc, Myanmar and its geological significance

The Shangalon copper-gold deposit is located in the northern segment of the Wunto-Popa magmatic arc in Myanmar. The research on this deposit is limited, and there is a lack of high-precision isotopic geochronological data regarding its ore-forming geological background and deposit genesis. In this study, five molybdenite samples from typical ores were selected to determine the mineralization age using the Re-Os isochron dating method. The obtained model ages range from 38.3±0.6 to 38.5±0.5 million years ago (Ma), with a weighted average age of 38.4±0.2 Ma. The corresponding isochron age is 38.0±1.6 Ma (MSWD=0.17). Both ages are in good agreement within the error range, indicating that the mineralization timing of the Shangalon copper-gold deposit is in the Eocene epoch. This age data corresponds well with the zircon U-Pb ages of 38 to 40 million years for the mineralized syenogranite and granodiorite in the mining area, suggesting a close relationship between the Shangalon Cu-Au-Mo mineralization and Eocene syenogranite-granodiorite intrusions, which are products of Eocene magmatic activity. The Re contents of molybdenite samples from the Shangalon copper-gold deposit range from 82.4 to 111.2 μg·g^－1, with an average value of 98.88 μg·g^－1, indicating a mixed source from the crust and mantle for the mineralizing fluids. Based on a comprehensive analysis of the regional metallogenic dynamics, it is suggested that the Eocene copper-gold mineralization in the Shangalon region possibly formed as a result of the fragmentation and faulting of the Neo-Tethys oceanic plate, triggered by the collision between the Indian and Eurasian continents, leading to upwelling of the asthenosphere and partial melting of the lower crust.