GEOCHRONOLOGY OF Sn MINERALIZATION IN MYANMAR: METALLOGENIC IMPLICATIONS

Abstract

Abstract Myanmar, the third largest global tin supplier, is an important component of the Southeast Asian tin province. We have conducted laser ablation-inductively coupled plasma-mass spectrometry U-Pb dating of cassiterite, wolframite, and zircon and Re-Os dating of molybdenite from six primary and two placer Sn deposits in Myanmar. A combination of our geochronological data with previous studies revealed that three episodes of Sn mineralization in the Western tin belt of Southeast Asia formed during the closure of multiple Tethys oceans, namely the Late Triassic (~218 Ma) mineralization in a collisional setting after closure of the Paleo-Tethys, the Early Cretaceous (~124–107 Ma) mineralization during subduction of the Meso-Tethys, and the Late Cretaceous to Eocene (~90–42 Ma) mineralization related to the Neo-Tethys subduction. Recurrent Sn mineralization is recorded not only in the Western tin belt but also in the Central and Eastern tin belts in Southeast Asia. Compilation of currently available cassiterite U-Pb ages from all over the world revealed that durations of regional Sn mineralization events are typically in the range of ~5–30 m.y., whereas the Neo-Tethys subduction in Southeast Asia generated prolonged Sn mineralization lasting up to ~50 m.y. The Southeast Asian tin province, as a whole, has the longest cumulative episodes of mineralization, compared to other Sn provinces. The Sn mineralization ceased in the late Eocene when the tectonic setting changed from Neo-Tethys subduction to dextral motion along a series of strike-slip faults and extrusion of the Indochina block in Southeast Asia.