Unravelling biotic versus abiotic processes in the development of large sulfuric-acid karsts

D. Laurent (1) , G. Barré (2, 3) , C. Durlet (4) , P. Cartigny (5) , Cédric Carpentier (1) , G. Paris (6) , Pauline Collon (1) , J. Pironon (1) , E.C. Gaucher (7, 3)

1 GeoRessources
2 Département de géologie et de génie géologique, Université Laval, 1065 avenue de la Médecine, Québec, Canada, G1V
3 TotalEnergies, Scientific and Technical Center Jean Féger, Pau
4 BGS - Biogéosciences [UMR 6282]
5 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
6 CRPG - Centre de Recherches Pétrographiques et Géochimiques
7 UNIBE - Universität Bern / University of Bern

In carbonate rocks, natural production of sulfuric acid can form karstic cavities. Where both epigenic and hypogenic speleogeneses have taken place, these processes are challenging to constrain, especially if there is more than one source of sulfur involved. Thanks to an innovative approach coupling geomorphology with measurements of multiple sulfur, oxygen, and strontium isotopes, our study of two French Pyrenean caves quantifies the relative influence of both microbial and thermochemical processes implied in sulfuric-acid production. Multiple sulfur isotopes reveal that sulfate speleothems derived from a mixing of microbial H2S in hydrothermal water and fossil thermochemical H2S previously trapped within the cave host rock. We quantify the percentages of biotic and abiotic sulfuric-acid speleogeneses that have taken place in these caves, paving the way for similar studies of other sulfuric-acid caves where usually only microbial activity has been considered.

Domaines: Sciences de l'environnement

D. Laurent, G. Barré, C. Durlet, P. Cartigny, Cédric Carpentier, et al.. Unravelling biotic versus abiotic processes in the development of large sulfuric-acid karsts. Geology, 2023, pp.G50658. ⟨10.1130/G50658.1⟩. ⟨hal-03951725⟩