Pulsated Global Hydrogen and Methane Flux at Mid-Ocean Ridges Driven by Pangea Breakup

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Merdith, Andrew S., del Real, Pablo García., Daniel, Isabelle, Andreani, Muriel, Wright, Nicky M., Coltice, Nicolas
• Other Authors: Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: serpentinization; mantle; seafloor spreading; slow-spreading ridges; pangea; hydrogen; [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Arctic; Indian
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03710132; https://hal-insu.archives-ouvertes.fr/insu-03710132/document; https://hal-insu.archives-ouvertes.fr/insu-03710132/file/Geochem%20Geophys%20Geosyst%20-%202020%20-%20Merdith%20-%20Pulsated%20Global%20Hydrogen%20and%20Methane%20Flux%20at%20Mid%25u2010Ocean%20Ridges%20Driven%20by%20Pangea.pdf; https://doi.org/10.1029/2019GC008869

International audience Molecular hydrogen production occurs through the serpentinization of mantle peridotite exhumed at mid-ocean ridges. Hydrogen is considered essential to sustain microbial life in the subsurface; however, estimates of hydrogen flux through geological time are unknown. Here we present a model of the primary, abiotic production of molecular hydrogen from the serpentinization of oceanic lithosphere using full-plate tectonic reconstructions for the last 200 Ma. We find significant variability in hydrogen fluxes (1-70 • 10 16 mol/Ma or 0.2-14.1 • 10 5 Mt/a), which are a function of the sensitivity of evolving ocean basins to spreading rates and can be correlated with the opening of key ocean basins during the breakup of Pangea. We suggest that the primary driver of this hydrogen flux is the continental reconfiguration during Pangea breakup, as this produces ocean basins more conducive to exhuming and exposing mantle peridotite at slow and ultraslow spreading ridges. Consequently, present-day flux estimates are ~7 • 10 17 mol/Ma (1.4 • 10 6 Mt/a), driven primarily by the slow and ultraslow spreading ridges in the Atlantic, Indian, and Arctic oceans. As methane has also been sampled alongside hydrogen at hydrothermal vents, we estimate the methane flux using methane-to-hydrogen ratios from present-day hydrothermal vent fluids. These ratios suggest that methane flux ranges between 10 and 100% of the total hydrogen flux, although as the release of methane from these systems is still poorly understood, we suggest a lower estimate, equivalent to around 7-12 • 10 16 mol/Ma (1.1-1.9 • 10 7 Mt/Ma) of methane.