Caracterización geoambiental de balsas de lodos mineros mediante tomografía eléctrica

Abstract

The mining of copper from sulphide ores, besides the metal production, generates large amounts of mine tailings that are deposited, e.g. in impoundments. Furthermore, due to natural leaching from these impoundments, contamination of the environment close to the deposits often occurs. In order to characterize the internal structure and groundwater flow of abandoned mine ponds in the Iberian Pyritic Belt, an electrical resistivity tomography study has been carried out. Two different mine ponds have been studied: the Monte Romero mine pond reveals a homogeneous internal structure with a maximum infilling thickness of about 4.5 metres; the La Nava mine pond has a more heterogeneous internal structure with an infilling thickness ranging from 15 to 20 metres. In both cases, the resistivity contrast between the infilling and the shales constituting the base of the pond is high enough to clearly define the bottom pond boundary. Whereas the Monte Romero mine pond is nearly fully saturated in water, the La Nava one shows a low resistivity area that defines the groundwater flow scheme inside the pond. The low resistivity values (lower than 5 ohm · m) obtained for the mine pond infilling are explained by the high concentration of pyrite in the tailings and the occurrence of acidic waters. No metal rich water fluxes outside the pond have been observed, indicating a good isolation of the two studied mine ponds