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Geofluids
Volume 2017, Article ID 8190109, 19 pages
https://doi.org/10.1155/2017/8190109
Research Article

Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France)

1Géosciences Montpellier, UMR 5243, Université de Montpellier, CNRS, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
2BRGM, ISTO, UMR 7327, 3 av. C. Guillemin, BP 36009, 45060 Orléans Cedex 2, France
3BRGM Occitanie-Site de Montpellier (Direction Régionale), 1039 rue de Pinville, 34000 Montpellier, France
4Calle Austria 2181, Asuncion, Paraguay

Correspondence should be addressed to Audrey Taillefer; rf.2ptnom-vinu.mg@refelliat.yerdua

Received 25 November 2016; Revised 8 March 2017; Accepted 23 April 2017; Published 2 August 2017

Academic Editor: Mark Tingay

Copyright © 2017 Audrey Taillefer et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The way faults control upward fluid flow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyrénées, an alignment of twenty-nine hot springs (29°C to 73°C), along the normal Têt fault, offers the opportunity to study this process. Using an integrated multiscale geological approach including mapping, remote sensing, and macro- and microscopic analyses of fault zones, we show that emergence is always located in crystalline rocks at gneiss-metasediments contacts, mostly in the Têt fault footwall. The hot springs distribution is related to high topographic reliefs, which are associated with fault throw and segmentation. In more detail, emergence localizes either (1) in brittle fault damage zones at the intersection between the Têt fault and subsidiary faults or (2) in ductile faults where dissolution cavities are observed along foliations, allowing juxtaposition of metasediments. Using these observations and 2D simple numerical simulation, we propose a hydrogeological model of upward hydrothermal flow. Meteoric fluids, infiltrated at high elevation in the fault footwall relief, get warmer at depth because of the geothermal gradient. Topography-related hydraulic gradient and buoyancy forces cause hot fluid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions.