Assessing the potential acid forming waste rocks in Kyaukpahto Gold Mine, Kawlin Township, Sagaing Region, Myanmar

Kyaukpahto gold mine located in the Kawlin Township, Sagaing Region of Myanmar is the first open pit and the largest gold mine of Myanmar. As the gold is exploited by open-pit mining, a large amount of waste rocks are disposed at waste dumps near the mine site. The metal sulfides such as pyrite, arsenopyrite, and chalcopyrite in the waste rocks are exposed to the surface, favoring the oxidation of these metal sulfides and generating acidic water. There is a possibility of AMD generation in the open pit and at the low grade ore dump. This work focuses on assessment of the potential acid-forming waste rocks and characterization of these waste rocks in Kyaukpahto gold mine. Waste rocks and water samples were taken from the open pit, low grade ore dump, and waste dumps and subjected to various tests and analyses such as NAG test, Paste pH test, Paste EC test, ANC test, XRF, XRD, and ICP-MS analyses. Based on the results of the chemical tests and analyses, waste rock samples collected from open pit and low grade ore dump are identified as PAF rocks which particularly concerned with the potential generation of acidic mine water. Two-step batch leaching test indicated that low pH value (pH 4) and elution of metal ions such as As, Al, Fe, Cu, Zn, and SO4^2-were observed with the high concentration from the samples. Elution of As is higher than other metal ions and this elution process will take place over a longer period than other metal ions. Thus, it is very critical to take appropriate measures against generation of AMD, such as controls on sulfides oxidation, and reduction of metals elution.