Epigenic vs. hypogenic speleogenesis governed by H2S/CO2 hydrothermal input and Quaternary icefield dynamics (NE French Pyrenees)

• Published in: Geomorphology
• Main Authors: Laurent, Dimitri, Durlet, Christophe, Barré, Guillaume, Sorriaux, Patrick, Audra, Philippe, Cartigny, Pierre, CARPENTIER, Cédric, Paris, Guillaume, Collon, Pauline, Rigaudier, Thomas, Pironon, Jacques, Gaucher, Eric
• Other Authors: GeoRessources, Institut national des sciences de l'Univers (INSU - CNRS)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Biogéosciences UMR 6282 Dijon (BGS), Centre National de la Recherche Scientifique (CNRS)-Université de Bourgogne (UB)-AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement, TOTAL-Scientific and Technical Center Jean Féger (CSTJF), TOTAL FINA ELF, Laboratoire des Fluides Complexes et leurs Réservoirs (LFCR), Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-TOTAL FINA ELF, Laboratoire de Polytech Nice-Sophia (Polytech'Lab), Université Nice Sophia Antipolis (. - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine (UL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: Pyrenees; Thermal water geochemistry; Multiple sulfur isotopes; Hypogene sulfuric and carbonic acid speleogenesis; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; Carbonic acid
• Online Access: https://hal.univ-lorraine.fr/hal-03246189; https://hal.univ-lorraine.fr/hal-03246189/document; https://hal.univ-lorraine.fr/hal-03246189/file/2021Pap_LaurentD_Geomorph_Version_Auteur.pdf; https://doi.org/10.1016/j.geomorph.2021.107769

International audience Hypogenic caves, linked to carbonate rock dissolution due to CO 2-and H 2 S-rich ascending deep waters, represent more than 10% of karstic networks worldwide; a proportion that increases as these systems are better constrained. However, interaction between hypogenic and epigenic processes is still poorly understood, especially since the subsequent invasion of surface water often obliterates the morphological and mineral markers of hypogenic activities. The Ariège Valley (French Pyrenean foothills) hosts significant karstic networks epigenically reworked by several episodes of glacier meltwater penetration during the successive coverage of Quaternary icefields. Among these karstic systems, the Vapeur and Ermite caves were probably initiated by a hypogenic component during the Miocene. In particular, multipleS , Sr, H, C, and O isotopes of thermo-mineral waters and calcite-sulfate speleothems confirm that hydrothermal fluids reached the caves, and subsequently interacted with Quaternary glacial epigenic phases. Deep fluids conveyed CO 2 and H 2 S, both produced from the thermochemical reduction of Triassic evaporites at depth. H 2 S oxidation and CO 2 hydration in the cave atmosphere, above the water table, created sulfuric and carbonic acids responsible for an intense karstification. Interpretation of isotopic data, together with a geomorphological, mineralogical and textural study of cave minerals, allow us to propose a speleogenetic model in which the respective impact of epigenic and hypogenic processes was driven by base-level changes during successive Quaternary glacial/interglacial epochs: (i) during glacial periods, invasion of glacier meltwater within the karst led to the dilution of the hydrothermal water, and was responsible for an "epigenic mechanical-dominant" speleogenesis through water-related abrasion; (ii) interglacial epochs were marked by base-level drops and the establishment of a vadose domain in caves, favoring the widening of karstic conduits through carbonic and ...