Geochemical appraisal of mine discharge and tailing at Malanjkhand copper mine, India

The Malanjkhand copper deposit, which is the largest open cast copper mine in Asia, is located in central India. The detailed hydrogeochemical study indicates that mine discharges are mostly highly acidic (pH 3.4–6.1) with very high concentration of Cu (9.2–60.8 mg/L). Water releases from the tailing pond is also acidic in nature (pH 2.39–2.48) and contains high concentration of Cu (15.6–65.2 mg/L). The water quality of the mine discharges and tailing is mainly affected by the oxidation of chalcopyrite, which presents abundantly in the host rock along with minor amount of pyrite. The blue coloured secondary mineral that precipitates along the course of the mine effluents is dominated by amorphous copper hydroxysulfate. Alpersite, gypsum, epsomite and hexahydrite occur as efflorescent salts during the summer time, and store very high concentration of metals. Alpersite contains Zn (285-391 mg/kg), Ni (62-78 mg/kg) and Cu (7.8-10.9%) whereas epsomite contains Zn (132-160 mg/kg), Ni (35-43 mg/kg) and Cu (3465-4184 mg/kg). Among the trace elements in tailing, Cu has the highest concentration ranges (98.2–4492 mg/kg) followed by Mn (131.4–760 mg/kg), Zn (54.3–241 mg/kg), Ni (25.7–170.3 mg/kg), Pb (12.5–46.4 mg/kg) and Cd (0.72–1.48 mg/kg). Tailing rich with efflorescent salt has maximum concentration of metals as well as maximum potential for releasing metals into the aqueous system.