Mineralogical and geochemical characterization of the tailings from the former lead-zinc flotation plant of Boquira mine, Brazil

A mine and a Pb-Zn flotation plant operated in the Northeast of Brazil until 1993 and about 4.5 million tons of untreated tailings were disposed of in a dam. The chemical analyses of the tailings indicate that the major constituents are Fe, Si, Mg, and Ca. The toxic metals(oids) content are: Pb 1.3%, Zn 1.3%, Cu 135 mg/kg, Cd 127 mg/kg, and As 5 mg/kg. The mineralogical analysis shows that the major phase is composed of minerals from the amphibole group, more specifically cummingtonite, actinolite, and tremolite, which are all fibrous silicates defined as asbestos. Electron probe microanalysis and synchrotron-based X-ray absorption spectroscopy show sulfide mineral weathering. The Pb bearing compounds in the tailings are a mixture of cerussite and anglesite. The leaching tests show strong leaching of Cd, Pb, and Zn. It indicates they might be a relevant source of toxic metals and fibers that can have a significant effect on the local population's health due to water and air contamination.