The Metallogeny of Myanmar

Myanmar (Burma) is one of the largest countries in SE Asia and is known to be rich in tin, tungsten, copper, gold, gemstones, zinc, lead, oil, gas and coal (e.g. Chhibber, 1934). It contains at least three ‘world class’ deposits of differing commodities and genesis: Bawdwin (lead–zinc); Monywa (copper) and Mawchi (tin–tungsten). The country’s complex geology reflects a collisional history stretching from the Jurassic–Cretaceous to at least Late Eocene sited at the eastern end of the Indian–Asian suture. It is due to this long and multiple geological and tectonic story that Myanmar has one of the most diverse and richly endowed collections of natural resources in SE Asia: simply, the distribution of ore deposits can be directly related to the tectonic history. Whereas there is some recent history of exploration and exploitation of mineral deposits within Myanmar (largely in the shape of UN-sponsored programmes in the 1970s and 1980s, and subsequent work by smaller western juniors), as a jurisdiction it remains poorly understood and hugely underdeveloped with regards its natural resources – due in the most part to the prevailing political climate. As the country emerges from several decades of isolation, we believe it is timely to both review and apply more modern techniques to better understand the metallogenesis of this fascinating country. Broadly, Myanmar can be divided into four principal metallotects: the Magmatic Arc, containing pre-collisional subduction-related granites with associated epithermal Cu–Au mineralisation; the Slate Belt, with multiple post-collisional S-type crustal melt granites that host significant Sn–W mineralisation (part of the SE Asia Tin Granite belts), and also host to a number of mesothermal gold deposits; the Shan Plateau limestones with notable VMS-type lead-zinc deposits; and the Mogok Metamorphic Belt, where (U)HT metamorphism resulted in world-class ruby and corundum-bearing marbles. Additionally, (U)HP metamorphism along the Jade Mines Belt in the North resulted in jadeitic pyroxene and associated serpentinisation of ophiolitic ultramafic rocks within the suture itself. At Oxford we are taking a multi-disciplined approach to better understand this geological history and relate it to the metallogenic endowment: geochemical, structural, field relations, and metamorphic. We have built a GIS database of known mineral deposits, recorded outcrops and mining activity, and this allows us to directly relate these to the underlying geology. We have, and are continuing to, make a number of key mine visits to observe these deposits on the ground. Finally, by the targeted use of U–Pb dating, metamorphic modelling, and granite geochemistry we hope to better constrain the larger tectonic picture and tie this into the regional geology. Chhibber, H.L. 1934. The Mineral Resources of Burma. Macmillan and Co, London