Content area
Full Text
Received Nov 25, 2016; Revised Mar 8, 2017; Accepted Apr 23, 2017
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.
1. Introduction
Studying hydrothermal fluid flow through fault zones is important to understand thermal perturbations of the Earth’s crust and can provide strong constraints on deep geothermal exploration. The fault-related geothermal systems which are currently studied [1, 2] focus on magmatic types (e.g., Bouillante [3]), rifts (e.g., East African Rift [4, 5]), or continental grabens (e.g., Soultz-sous-Forêts [6]). Nonmagmatic hydrothermal systems in continental contexts involving high relief and hot springs [7] are rarely studied [8]. Further, processes acting in this kind of hydrothermal systems are essentially explored by numerical models [9, 10] (e.g., the Dixie Valley geothermal field 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 upflow, as proved by the emergence of hot springs adjacent to normal fault scarps, and associated reliefs [17]. Based on numerical studies, conceptual models suggest that meteoric water infiltrates 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 groundwater recharge [19], inducing both a hydraulic gradient and thermal disturbance, exert a significant role on hydrothermal circulation. Petrophysical and thermal properties, especially permeability [23], play a critical role in the establishment of a fluid circulation pattern and thus in the building of possible thermal anomalies [11, 24]. Without magmatic activity, the mantle-derived crustal heat is responsible for the meteoric fluid warming. During their transfer in the crust, hot fluids alter rocks and become mineralized. Because of the decompression and cooler conditions in surface, mineralized fluids precipitate as alteration deposits (including quartz and carbonates sinter or travertine [25]) which may be used as evidence of hydrothermal circulations [26].
Faults are often mentioned as important structures providing strong permeability anisotropy in the Earth crust [15, 27]. The variability of brittle fault zones permeability has been widely discussed these last twenty years [27]. Depending on the stratigraphic column and displacements scale [28], faults juxtapose compartments which may be...