Water-Rock Interaction Ascribed To Hyperalkaline Mineral Waters In The Cabeco De Vide Serpentinized Ultramafic Intrusive Massif (Central Portugal)

The conceptual model of Cabeco de Vide mineral waters, issuing at the contact metamorphism zone developed by the local mafic/ultramafic pluton, is described. These mineral waters discharge with a temperature between 17 and 20 degrees C, show a very alkaline pH (up to 11.8), and have: Na-Cl/Ca-OH facies; dry residuum approximate to 200 mg/L; C-total < 3.0 mg/L; and extremely low Mg2+ and silica concentrations (< 0.3 and 6.5 mg/L, respectively). CH4 isotopic composition (-24.4 parts per thousand < delta C-13-CH4 < -14.0 parts per thousand and 285 parts per thousand < delta H-2-CH4 < -218 parts per thousand) falls in the range of typical abiotic gas. In the case of Cabeco de Vide mineral waters, the understanding of the resource will help to preserve the mineral water quality, creating public interest. (C) 2017 The Authors. Published by Elsevier B.V. 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.