Determination of Carbonate Minerals Responsible for Alkaline Mine Drainage at Xikuangshan Antimony Mine, China: Using Thermodynamic Chemical Equilibrium Model

Minerals responsible for mine water quality at the Xikuangshan antimony mine were identified and characterized by a computer-assisted thermodynamic chemical equilibrium model. A total of 30 samples were collected and analyzed for major cations and anions. The Eh-pH diagrams identified Fe₂O₃ as the dominant iron species, while SO₄^2- was the dominant sulfide species, which indicates acid production. The major acid producing minerals undergoing oxidation were identified to be pyrite, pyrrhotite, arsenopyrite and siderite. Other secondary sulfide minerals that contributed to SO₄^2- concentration in the groundwater were gypsum and epsomite. Calcite and dolomite were the main buffering carbonate minerals. Identification of the specific acid producing and consuming minerals occurred in the mine area is critical to determine an effective water management plan.