22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Hydrogeochemical study of epiperidotitic springs of the ultramafic outcrop of Ronda peridotites (South of Spain)

24 Sep 2019, 16:00
1h
Trade Fairs and Congress Center (FYCMA)

Trade Fairs and Congress Center (FYCMA)

Av. de José Ortega y Gasset, 201 29006 Malaga, Spain
Poster Topic 5 - Tools, methods and models to study groundwater Poster with refreshments

Speaker

Dr Iñaki Vadillo-Pérez (Grupo de Hidrogeología, Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga)

Description

At the Malaga province (South of Spain) it is found the largest outcrop of peridotites (Lerzholites) on Earth. They are divided into three large Sierras: Sierra Bermeja, Sierra Alpujata and Sierra de Aguas. Although it is not considered an aquifer system due to its hydraulic behavior, there are hundreds of springs that drain the infiltration of rain and, to a lesser extent, snow. Some of these springs are considered hyperalkaline because they reach pH above 10 and are subject to study because of the unusual hydrochemical characteristics (pH between 10-12, high concentrations of Si, CH4 fluxes and certain thermalism, among others). In this work we will focus on the so-called epiperidotitic springs, that is, those whose pH is less than 10 and, therefore, have had less contact with the rock and circulate in a more open-semi-open system than that of the springs of pH greater than 10. Various water-rock interaction processes are proposed that explain different water families taking into account the hydrogeochemical parameters and the two large outcrops of Peridotites: Sierra Alpujata and Sierra Bermeja. Thus, a greater correlation between the contents of Si and Cr in Sierra Alpujata than in Sierra Bermeja is observed. The correlation between the pH and the saturation indices of minerals related to the serpentinization (Chrysotile, Nesqueonite and Brucite) is positive and high, which confirms an incipient serpentinization of some of the epiperidotitic springs. These two parameters (pH and saturation indexes) show an inverse correlation with PCO2, which indicates that there are waters that have circulated in a semi-open environment. The isotopic signal of dissolved inorganic carbon (δ13CDIC) is inversely related to most hydrogeochemical parameters. Waters with values closer to the atmospheric δ13CCO213CCO2 ~ -9 ‰) are waters of recent infiltration, with shorter transit time and less water-rock interaction, so their mineralization is low.

Primary authors

Dr Iñaki Vadillo-Pérez (Grupo de Hidrogeología, Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga) Dr Pablo Jiménez-Gavilán (University of Málaga) Mrs Rocio Scapini-Gallardo (Grupo de Hidrogeología, Facultad de Ciencias, Universidad de Málaga) Prof. José Benavente Herrera (Institut de l’Eau, Université de Grenade, Grenade, Espagne) Dr Begoña Urresti-Estala (University of Málaga)

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