Research Article Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France) Audrey Taillefer, 1 Roger Soliva, 1 Laurent Guillou-Frottier, 2 Elisabeth Le Goff, 3 Guillaume Martin, 4 and Michel Seranne 1 1 G´ eosciences Montpellier, UMR 5243, Universit´ e de Montpellier, CNRS, Place Eug` ene Bataillon, 34095 Montpellier Cedex 5, France 2 BRGM, ISTO, UMR 7327, 3 av. C. Guillemin, BP 36009, 45060 Orl´ eans Cedex 2, France 3 BRGM Occitanie-Site de Montpellier (Direction R´ egionale), 1039 rue de Pinville, 34000 Montpellier, France 4 Calle Austria 2181, Asuncion, Paraguay Correspondence should be addressed to Audrey Taillefer; audrey.taillefer@gm.univ-montp2.fr 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. Tis 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. Te way faults control upward fuid fow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyr´ en´ ees, an alignment of twenty-nine hot springs (29 ∘ C to 73 ∘ C), along the normal Tˆ et fault, ofers 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 Tˆ et fault footwall. Te 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 Tˆ et 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 fow. Meteoric fuids, infltrated 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 fuid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions. 1. Introduction Studying hydrothermal fuid fow through fault zones is important to understand thermal perturbations of the Earth’s crust and can provide strong constraints on deep geothermal exploration. Te fault-related geothermal systems which are currently studied [1, 2] focus on magmatic types (e.g., Bouillante [3]), rifs (e.g., East African Rif [4, 5]), or conti- nental grabens (e.g., Soultz-sous-Forˆ ets [6]). Nonmagmatic hydrothermal systems in continental contexts involving high relief and hot springs [7] are rarely studied [8]. Further, pro- cesses acting in this kind of hydrothermal systems are essen- tially explored by numerical models [9, 10] (e.g., the Dixie Valley geothermal feld in Nevada [11–13]), and integrative geological studies as proposed in this paper are few in number [7, 14–16]. Faults have been involved in controlling water upfow, as proved by the emergence of hot springs adjacent to normal fault scarps, and associated reliefs [17]. Based on numeri- cal studies, conceptual models suggest that meteoric water infltrates from the top of the ranges to kilometric depths, before rising up to the surface through permeable zones. Topography [18–20], buoyancy forces [21, 22], and ground- water recharge [19], inducing both a hydraulic gradient and thermal disturbance, exert a signifcant role on hydrothermal circulation. Petrophysical and thermal properties, especially permeability [23], play a critical role in the establishment of a fuid circulation pattern and thus in the building of possible Hindawi Geofluids Volume 2017, Article ID 8190109, 19 pages https://doi.org/10.1155/2017/8190109