Hydrochemical characterisation of water quality in the Sarcheshmeh copper complex, SE Iran

Hydrochemical investigations were conducted to identify variations in surface water chemistry in different parts of the Sarcheshmeh copper complex. Twenty-three water samples from mine drainage, stream water, processing water of the concentrator plant and tailings dam water were collected to understand processes that control the elements’ mobility. Changes in trace metal concentrations and variation of major ions show two distinct water types: (a) neutral mine drainage (NMD) associated with the Sarcheshmeh mine waters containing lower trace metal, SO₄ ²⁻ concentrations and neutral pH values, and (b) acid mine drainage (AMD) with waters from tailings impoundments and waste rock dumps corresponding to higher trace metals (Fe, Cu, Zn, Mo) and major anions (SO₄ ²⁻ and Cl⁻) than the first type with typically acidic pH contents. As a result of Cu–Mo sulphides flotation process under alkaline conditions, high pH values, high Mo concentration and low contamination loads of Al, Mn, Fe, Cu and Cd were observed in reject waters from the concentrator plant. Sulphide oxidation (especially pyrite), dissolution–precipitation of the secondary minerals and discharge of the reject waters from concentrator plant were some of the most important factors that influence water quality at the tailings impoundments. The results of PHREEQC speciation and solubility modelling indicated supersaturation of the waters in the tailings impoundments with respect to hydronium jarosite, schwertmannite and gypsum.