Porphyry and Hydrothermal Cu-Au Deposits: A Global Perspective

The Monywa project comprises two main zones of chalcocite blanket ore 6 km apart, the Letpadaung and Kyisintaung deposits, which together constitute a global resource of around 1 Gt @ 0.41% Cu, most of which is amenable to cheap SX/EW treatment. Projected production rates are quoted as initially building up to around 100 000 t of copper per annum in two stages. These deposits are on the southern margin of the Tethyan Belt, but are related to the same subduction zone as the western Asia-Pacific deposits in Indonesia. The Monywa project is currently being evaluated and developed jointly by the Myanmar Government and Ivanhoe Myanmar Holdings Ltd.
The copper mineralisation is of high sulphidation style and occurs predominantly within chalcocite bearing breccia bodies. The mineralisation is hosted in late Tertiary dacite intrusions and acid pyroclastics located along a northerly trending volcanic arc which bisects the Inner Burman Tertiary Basin. The breccia bodies appear to have been initiated in the uppermost portions of sub-volcanic dacite intrusions that were highly enriched in volatiles, copper and sulphur. Chalcocite is the dominant ore mineral and occurs as fracture coatings, disseminations and breccia matrix. The gold content of the copper ore is negligible. Low sulphidation epithermal quartz veins to the north and east of the breccia bodies contain sub-economic levels of silver and gold.