The Occurrence of Cd and Tl in the Sphalerite from El Losar del Barco Mine (Ávila, Spain): a Potential Environmental Hazard.

Abstract

Sphalerite is the chief ore of zinc in all sulfide-rich base metal deposits. A broad range of trace and minor elements, some of them highly toxic (notably Cd, but also, Tl, As, Hg, etc), can occur in this mineral, often at levels that may pose an environmental hazard in abandoned ore dumps and mine tailings. Sphalerite is generally considered less reactive than pyrite but dissolution rates for the two minerals may neverthless be comparable. Unlike pyrite, sphalerite may even continue dissolving in a nonoxidizing conditions (Acero et al., 2007), increasing, therefore, the risk of toxic element release into the environment. T he Santa Manolita mine in El Losar del Barco (Ávila, Spain) is a small mining exploitation, abandoned several decades ago. In this area some waste rock piles, where sphalerite is a very abundant mineral, and vestiges of the mineral processing plant are still visible. This deposit is characterised by Pb-Ag (galena) and Zn (sphalerite) hydrothermal-type mineralization in quartz veins embedded in biotitic granite with high silicification (Mapa Geológico y Minero de Castilla y León, 1997). The aim of this work is to characterise the sphalerite from this mining area to identify its toxic element content and to assess if this mineral is responsible for the contamination detected in a research study in progress in this area.