Hydrogeochemistry and Contamination of Trace Elements in Cu-Porphyry Mine Tailings: A Case Study from the Sarcheshmeh Mine,SE Iran |
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| Authors: | Mehdi Khorasanipour Afsar Eslami |
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| Affiliation: | 1. Depatment of Geology, Shahid Bahonar University of Kerman, Kerman-Pajohesh Square, 76135-133, Kerman, Iran
2. Research and Development Division, Sarcheshmeh Copper Complex, Kerman, Iran
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| Abstract: | Geochemical and hydrochemical investigations were performed to understand the contamination potential of the Sarcheshmeh mine tailings. The geochemical mobility for the tailings is as follows: Cu > Cd > Co > Zn > Ni > Mn > S > Cr > Sn > As > Se > Fe = Bi > Sb = Pb = Mo. Highly mobile and contaminant elements (Cd, Cu, Zn, Mn, Co, Ni, S, and Cr), which significantly correlated with each other, were mainly concentrated in the surface evaporative layer of the old, weathered tailings, due to the high evaporation rate, which causes subsurface water to migrate upward via capillary action. The contamination potential associated with the tailings is controlled by: (1) dissolution of secondary evaporative soluble phases, especially after rainfall on the old weathered tailings, accompanied by low pH and high contamination loads of Al, Cd, Co, Mg, Cr, Cu, Mn, Ni, S, Se, and Zn; (2) processing of the Cu-porphyry ore under alkaline conditions, which is responsible for the high Mo (mean of 2.55 mg/L) and very low values of other contaminants in fresh tailings in the decantation pond; (3) low mobility of As, Fe, Pb, Sb, Mo, and Sn due to natural adsorption and co-precipitation in the tailings oxidizing zone. Speciation modeling showed that sulfate complexes (MSO4 +, M(SO4)(aq), M(SO4) 2 ?2 , and M(SO4) 2 ? ) and free metal species (M+2 and M+3) are the dominant forms of dissolved cations in the acidic waters associated with the weathered tailings. In the alkaline and highly alkaline waters, trace element speciation was controlled by various hydroxide complexes, such as M(OH)+, M(OH) 3 ? , M3(OH) 4 +2 , M2(OH) 3 + , M(OH)2(aq), M(OH) 4 ?2 , Me(OH) 2 + , Me(OH) 4 ? , Me(OH) 2 + , Me(OH)3(aq), and Me(OH) 4 ? (where M represents bivalent and Me represents trivalent cations). The speciation pattern of As, Mo, and Se is mainly dominated by oxy-anion forms. The obtained results can be used as a basis for environmental management of the Cu-porphyry mine tailings. |
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