Discovered the origin of the acidity of the Tinto River
25-03-2014

Based on the studies developed within the IPBSL project (Iberian Pyrite Belt Subsurface Life Detection) by the research group of the Center for Astrobiology, it is shown that the origin of the acidic waters of the Rio Tinto is mainly due to the interaction of underground aquifers with different geological units that contain significant amounts of massive metal sulfides. The result is published in the journal Earth and Planetary Science Letters.

The Iberian Pyrite Belt is a geological structure that extends through the southwest region of the Iberian Peninsula. It is an area very rich in all kinds of minerals, mainly pyrite. In fact, it is an area of ​​intensive mining for at least 5,000 years. In addition, mining is carried out in the open and in the province of Huelva there are more than 200 mines, almost all of them out of operation.

To the north of the province of Huelva, in the heart of the mining region, locate some of the largest mining operations. This circumstance has drastically modified the terrain creating a landscape with an extraterrestrial aspect. In this area the Tinto River is born, a river of waters dyed red due to the high concentration of iron oxides, which gives it its name. The waters of the river also have a high acidity.

Until a few years ago the origin of the acidity of the waters of the Tinto River was unknown and it was thought that it was the result of the intensive mining exploitation. Although at least since 2008 it had already been suggested that the origin of the acidity of the river was due to the biooxidation of massive sulfides, the absence of a precise determination of the location of this source of acidity in the subsoil did not finish the debate.

However, now it has been possible to demonstrate from the geophysical and geochemical studies developed within the IPBSL project (Iberian Pyrite Belt Subsurface Life Detection) by the research group of the Center for Astrobiology (CAB, CSIC- INTA) that the origin of the acidic waters of the Tinto River is fundamentally due to the interaction of subterranean aquifers with different geological units that contain important quantities of massive metallic sulfides. The work is published in the journal Earth and Planetary Science Letters.

This project has allowed obtaining samples of the subsoil of the Pyrite Belt up to a depth of 620 meters, specifically from the area known as Peña del Hierro, where the birth of the Tinto River is located. The resistivity data and the electromagnetic soundings in the Río Tinto aquifer to these depths have revealed the locations of the acidity sources, supporting the presence of two different geological units located in the other Varisco del Carbonífero orogeny. These units contain massive sulfides and & nbsp; they act as the aquifer of the acidic waters of the Rio Tinto. This result is in accordance with the geological record of the Rio Tinto fluvial system in the last 6 million years.

Ricardo Amils, Professor of Microbiology at the Autonomous University of Madrid and leader of the CAB research group in Rio Tinto, he comments "these results imply that the mining activity has a very limited influence on the generation of the acid waters of the Rio Tinto, contrary to what is currently established, which has implications of undoubted environmental interest". For his part, David Fernández-Remolar, CAB Researcher, adds "the multidisciplinary analysis of them will allow us to know the metabolisms of the microorganisms involved in these processes."

More information

Scientific article : " Identification of the subsurface sílfide bodies responsible for acidity in Río Tinto source water, Spain , David Gómez-Ortiz, David C. Fernández-Remolar, Ángel Granda, Cecilio Quesada, Teresa Granda, Olga Prieto-Ballesteros, Antonio Molina and Ricardo Amils. Earth and Planetary Science Letters 2014, 391, 36-41. DOI: 10.1016 / j.epsl.2014.01.022

Contact

Ricardo Amils Pibernat , Center for Astrobiology (CSIC-INTA), Department of Planetology and Habitability; and Molecular Biology Center (CSIC-UAM)

David C. Fernández-Remolar , Center for Astrobiology (CSIC-INTA), Department of Planetology and Habitability

Scientific Culture Unit of the CAB: Luis Cuesta

 

Fuente: UCC-CAB

 

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