Determination of the geochemical background in a metal mining site: example of the mining district of Linares (South Spain)

The study region is situated in the mining district of Linares (province of Jaén, South Spain) and it is characterised by the presence of important seams of galena. The mining, minerallurgic and metallurgic activities in the area, as well as the local geological (metallogenetic) conditions, are important sources of heavy metals in the environment, resulting in considerable soil contamination.The study area occupies a surface area of 126 km2, divided into grid squares of 1 km2 for soil sampling, in order to characterise the geochemical background of this abandoned mining region. The soil samples were analysed for total concentrations of 32 elements; the discussion focuses on eight in particular (Cu, Pb, Zn, Ag, As, Cd, Sb and Mn), these being the main elements associated with human activity. The mean contents of all these elements exceed the Clarke comparison values for trace elements in acid igneous rocks. The total concentrations of Pb, Ag, As, Cd and Sb are especially high. In this very complex zone, on the basis of cluster analysis and of field observations, the local background contents of each geological substrate are defined, distinguishing the different types of activity that took place in the zone and different degrees of intensity.