biostudies-literatureUnknown11(1)Moine BNTrace amounts of water dissolved in minerals affect density, viscosity and melting behaviour of the Earth's mantle and play an important role in global tectonics, magmatism and volatile cycle. Water concentrations and the ratios of hydrogen isotopes in the mantle give insight into these processes, as well as into the origin of terrestrial water. Here we show the presence of molecular H<sub>2</sub> in minerals (omphacites) from eclogites from the Kaapvaal and Siberian cratons. These omphacites contain both high amounts of H<sub>2</sub> (70 to 460 wt. ppm) and OH. Furthermore, their ∂D values increase with dehydration, suggesting a positive H isotope fractionation factor between minerals and H<sub>2</sub>-bearing fluid, contrary to what is expected in case of isotopic exchange between mineraNature communications3604https://www.ebi.ac.uk/biostudies/studies/S-EPMC7367874biostudies-literatureMolecular hydrogen in minerals as a clue to interpret ∂D variations in the mantle.PMC7367874Korsakov AVRadu IBCottin JYBolfan-Casanova NGolovin AVMoine BNCostin GOleinikov OBDeloule EIonov DAfalseMolecular hydrogen in minerals as a clue to interpret ∂D variations in the mantle.Trace amounts of water dissolved in minerals affect density, viscosity and melting behaviour of the Earth's mantle and play an important role in global tectonics, magmatism and volatile cycle. Water concentrations and the ratios of hydrogen isotopes in the mantle give insight into these processes, as well as into the origin of terrestrial water. Here we show the presence of molecular H<sub>2</sub> in minerals (omphacites) from eclogites from the Kaapvaal and Siberian cratons. These omphacites contain both high amounts of H<sub>2</sub> (70 to 460 wt. ppm) and OH. Furthermore, their ∂D values increase with dehydration, suggesting a positive H isotope fractionation factor between minerals and H<sub>2</sub>-bearing fluid, contrary to what is expected in case of isotopic exchange between minera2020-01-01T00:00:00Z2020 Jul2025-04-22T19:33:04.781Z2021-02-21T04:48:01ZS-EPMC73678743268111310.1038/s41467-020-17442-8