https://doi.org/10.5194/se-2020-54 Preprint. Discussion started: 23 April 2020 c Author(s) 2020. CC BY 4.0 License. Tracking geothermal anomalies along a crustal fault using (U-Th)/He apatite thermochronology and REE analyses, the example of the Têt fault (Pyrenees, France) Gaétan MILESI1, Patrick MONIÉ1, Philippe MÜNCH1, Roger SOLIVA1, Audrey TAILLEFER1, Olivier BRUGUIER1, 5 Mathieu BELLANGER2, Michaël BONNO1, Céline MARTIN1 1Géosciences Montpellier, Université de Montpellier, CNRS, Université des Antilles, Campus Triolet, CC060, Place Eugène Bataillon, 34095 Montpellier Cedex05 France 2TLS Geothermics, 92 chemin de Gabardie, 31200 Toulouse France Correspondence to: Gaétan Milesi (
[email protected]) 10 Abstract. The Têt fault is a crustal scale major fault in the eastern Pyrenees along which 29 hot springs emerge mainly within the footwall damage zone of the fault. In this study, (U-Th)/He apatite (AHe) thermochronology is used in combination with REE analyses to investigate the imprint of hydrothermal activity nearby two main hot spring clusters and in between in an attempt to better define the geometry and intensity of the recent thermal anomalies along the fault and to compare them with previous results from numerical modelling. This study displays 99 new AHe ages and 63 REE analyses on samples collected 15 in the hanging wall (18 to 43 Ma) and footwall (8 to 26 Ma) of the Têt fault. In the footwall, the results reveal AHe age resetting and apatite REE depletion due to hydrothermal circulation along the Têt fault damage zone, nearby the actual hot springs (Thuès-les-Bains and St-Thomas) but also in areas lacking actual geothermal surface manifestation.