Professor Jorge Loredo (Professor of Mining and Environmental Exploration, School of Mines, Energy and Materials - University of Oviedo, Spain)

“The mercury deposits of Asturias and their environmental implications”

Asturias (NW Spain) is regarded as an important mercury metallogenic province where ore deposits are located within the so-called “Cantabrian Zone”, the foreland of the Variscan Chain of NW Iberia; an important mineralogic characteric of these Hg deposits is the presence of arsenic in theform of orpiment, realgar and As-rich pyrite. Mercury mining has been an important activity in the region to the point of becoming the third world producer during the 1960-70s, when average production was in the order of 15,000 flasks per year. Metallurgical activity to extract Hg from these ores was also carried out at some mine sites. On the 1970’s all Hg mines of the district were abandoned without the application of any environmental action to avoid the releasing of metals to the environment. Currently, the legacy of the Hg mining activities developed in the district remains on site, in the form of rests of the mining and industrial installations (shafts, roasting furnaces, chimneys, etc.) and significant quantities of mining and metallurgical wastes stored in spoil heaps. As a result of this legacy polluted surface waters, sediments and soils are frequent in the area of the mine sites.