title: Microbial and diagenetic steps leading to the mineralisation of Great Salt Lake microbialites.
abstract: Microbialites are widespread in modern and fossil hypersaline environments, where they provide a unique sedimentary archive. Authigenic mineral precipitation in modern microbialites results from a complex interplay between microbial metabolisms, organic matrices and environmental parameters. Here, we combined mineralogical and microscopic analyses with measurements of metabolic activity in order to characterise the mineralisation of microbial mats forming microbialites in the Great Salt Lake (Utah, USA). Our results show that the mineralisation process takes place in three steps progressing along geochemical gradients produced through microbial activity. First, a poorly crystallized Mg-Si phase precipitates on alveolar extracellular organic matrix due to a rise of the pH in the zone of active oxygenic photosynthesis. Second, aragonite patches nucleate in close proximity to sulfate reduction hotspots, as a result of the degradation of cyanobacteria and extracellular organic matrix mediated by, among others, sulfate reducing bacteria. A final step consists of partial replacement of aragonite by dolomite, possibly in neutral to slightly acidic porewater. This might occur due to dissolution-precipitation reactions when the most recalcitrant part of the organic matrix is degraded. The mineralisation pathways proposed here provide pivotal insight for the interpretation of microbial processes in past hypersaline environments.
authors.affiliation: Ensegid Bordeaux INP, G&E, EA 4592, F-33600, Pessac, France.|Université Bordeaux Montaigne, G&E, EA 4592,F-33600, Pessac, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Pace
authors.affiliation: Ensegid Bordeaux INP, G&E, EA 4592, F-33600, Pessac, France.|Université Bordeaux Montaigne, G&E, EA 4592,F-33600, Pessac, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Bourillot
authors.affiliation: Laboratoire Biogéosciences UMR 6282 UBFC/CNRS, Univ. Bourgogne Franche-Comté, 6 boulevard Gabriel, Dijon 21000, France.
authors.forename: Anthony
authors.initials: A
authors.lastname: Bouton
authors.affiliation: Laboratoire Biogéosciences UMR 6282 UBFC/CNRS, Univ. Bourgogne Franche-Comté, 6 boulevard Gabriel, Dijon 21000, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Vennin
authors.affiliation: Ensegid Bordeaux INP, G&E, EA 4592, F-33600, Pessac, France.
authors.forename: Serge
authors.initials: S
authors.lastname: Galaup
authors.affiliation: Laboratoire Biogéosciences UMR 6282 UBFC/CNRS, Univ. Bourgogne Franche-Comté, 6 boulevard Gabriel, Dijon 21000, France.
authors.forename: Irina
authors.initials: I
authors.lastname: Bundeleva
authors.affiliation: Université de Poitiers, UMR 6269 CNRS, HYDRASA, 40 avenue du Recteur Pineau, 86022 Poitiers, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Patrier
authors.affiliation: Department of Geological Sciences, Stockholm University, Svante Arrhenius väg 8, Stockholm, 06269, Sweden.
authors.forename: Christophe
authors.initials: C
authors.lastname: Dupraz
authors.affiliation: Laboratoire Biogéosciences UMR 6282 UBFC/CNRS, Univ. Bourgogne Franche-Comté, 6 boulevard Gabriel, Dijon 21000, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Thomazo
authors.affiliation: Laboratoire Domaines Océaniques, Université de Bretagne Occidentale, UMR 6538 CNRS, 29280 Plouzané, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Sansjofre
authors.affiliation: Atmosphere and Ocean Research Institute, Department of Earth and Planetary Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8564, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yokoyama
authors.affiliation: Ensegid Bordeaux INP, G&E, EA 4592, F-33600, Pessac, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Franceschi
authors.affiliation: I2M, ENSAM, UMR 5285 CNRS, Esplanade des Arts et Métiers, 33405 Talence, France.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Anguy
authors.affiliation: Ensegid Bordeaux INP, G&E, EA 4592, F-33600, Pessac, France.
authors.forename: Léa
authors.initials: L
authors.lastname: Pigot
authors.affiliation: Total, CSTJF, Avenue Larribau, 64018 Pau, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Virgone
authors.affiliation: Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, CT 06340, USA.
authors.forename: Pieter T
authors.initials: PT
authors.lastname: Visscher
mesh_terms: D055598:Chemical Phenomena; D000458:Cyanobacteria / Q000737:chemistry / Q000378:metabolism*; D019015:Geologic Sediments / Q000382:microbiology*; D007287:Inorganic Chemicals / Q000378:metabolism*; D060106:Lakes / Q000382:microbiology*; D008903:Minerals / Q000378:metabolism*; D009930:Organic Chemicals / Q000378:metabolism*; D014589:Utah
chemical_list: D007287:Inorganic Chemicals; D008903:Minerals; D009930:Organic Chemicals