Potential environmental impact at Sao Domingos mining district (Iberian Pyrite Belt, SW Iberian Peninsula): evidence from a chemical and mineralogical characterization

摘要

Sao Domingos like other long-term activity mines of the Iberian Pyrite Belt (IPB) dating back to pre-Roman times, is supposed to produce considerable amounts of mining wastes which cause significant downstream negative environment impact related to the acid mine drainage (AMD) production and high content of potentially toxic metals and metalloids in Chanza and Guadiana Rivers. The AMD production of a given mining waste depends on the ratio of its acid production to neutralizing phases. In this work, a chemical and mineralogical characterization of the sulphide-rich wastes from Sao Domingos has been developed to discriminate which residues are the main sources of AMD generation. A total of 47 representative samples of the different residue types were collected to estimate their possible contamination hazards through detailed studies of (1) for a mineralogical characterization: reflected-light optical microscope, scanning electron microscope (SEM) and XRD analysis; and (2) for a chemical characterization: bulk-rock analysis. AMD prediction by the standard acid-base accounting method (ABA) was used in order to determine the acidification potential of each residue type. This study also offers an estimation of the contribution of toxic elements to thernenvironment, being thus, a base for future remediation actions at Sao Domingos and other abandoned massive sulphide mines within the IPB.