Abstract

The environmental impact of abandoned sulfide-bearing tailings mainly associated with the generation of highly acidic, toxic waters causes a widespread public concern. Meanwhile, a fundamental understanding of the relationship between the secondary mineralogy produced by pyrite dissolution and the wind erosion on these artificial deposits has remained elusive. Here we address this gap in knowledge by elucidating the factors that control the tailings surface erodible by wind. Chile has developed its mining industry for decades, mainly in the north of the country, where desert landscapes dominate. Many of the tailings have been abandoned to the weather. Two areas of study with different climates ranging from arid to semiarid were evaluated by mineralogy, chemistry and particle size. Using statistical analysis, we demonstrated that it is possible to establish distinct types of alterations, which differ in secondary mineralogy mainly, giving rise three clusters: feldspar-dominated (without secondary mineralization), goethite-dominated and jarosite-dominated (with presence of efflorescent salts). When observing these clusters in the field, different surfaces characterize by contrasting cohesion and wind erodibility potential. Although selected clusters in both deposits share a similar set of minerals, the particle size, amount of pyrite and its by-products vary from one site to another. In addition, the microscopic morphology of the pyrite grains from both the uppermost section and deeper levels of the tailings reveals greater oxidation/dissolution in semiarid climate over arid climate, as well as more spherical particles in the surface levels and elongated ones in depth. Together, these data evidence that pyrite alone, regardless of its content and particle size, does not generate acidic solutions leading to the precipitation of secondary phases. The extent of secondary mineralization is also linked to the climate (available humidity), tailing permeability and pH-neutralizing primary phases. Depending on these variables, different potentially erodible surfaces showing to a greater or lesser cohesion of particles and higher or lower contents of toxic metals, which, in turn, is the reason for these tailings to become a public health issue.