Hydrothermal systems at ultraslow-spreading mid-ocean ridges remain poorly characterized, particularly where sedimentary and ultramafic influences intersect. Here we present geochemical analyses of vent fluids collected in 2024 from the Jøtul hydrothermal field on the northern Knipovich Ridge. Major element concentrations, dissolved gases, and thermodynamic modeling are used to investigate fluid-rock interactions. The fluids exhibit exceptionally high CH4 concentrations, that exceed those at the Guaymas Basin, and display characteristics typical of sediment-hosted hydrothermal systems, indicating thermal decomposition of organic matter in clastic sediments. In contrast, high H2 (>15 mM) and low H2S concentrations are more typical of ultramafic-hosted fluids, while geological evidence indicates that the vent field lies atop a detachment fault. Thermodynamic modeling suggests that these high H2/H2S ratios may result solely from degradation of organic matter followed by abiotic CH4 oxidation at ~400 °C, rather than from reactions with ultramafic rocks. These results expand the known diversity of sediment-hosted vent fluid compositions and highlight fluid-sediment interaction as an underestimated source of carbon and hydrogen.
Diehl A., Anagnostou E., Monien P., Pape T., Meckel E.-M., Römer M., Mezri L., Bach W., Monien D., Hansen C., Röhler A., Streuff K., Palinkas S.S., Marcon Y., Barrenechea Angeles I., Kleint C., Knutsen S. and Bohrmann G. (2026) High H2 production in sediment-hosted hydrothermal fluids at an ultraslow spreading mid-ocean ridge. Communications Earth & Environment 7(1). 10.1038/s43247-025-02962-2
@article{Diehl2026,
Title = {High H2 production in sediment-hosted hydrothermal fluids at an ultraslow spreading mid-ocean ridge},
Author = {Diehl, Alexander and Anagnostou, Eirini and Monien, Patrick and Pape, Thomas and Meckel, Eva-Maria and Römer, Miriam and Mezri, Leila and Bach, Wolfgang and Monien, Donata and Hansen, Christian and Röhler, Aaron and Streuff, Katharina and Palinkas, Sabina Strmic and Marcon, Yann and Barrenechea Angeles, Ines and Kleint, Charlotte and Knutsen, Stig‑Morten and Bohrmann, Gerhard},
Editor = {},
Journal = {Communications Earth & Environment},
Year = {2026},
Volume = {7},
Doi = {10.1038/s43247-025-02962-2},
Abstract = {Hydrothermal systems at ultraslow-spreading mid-ocean ridges remain poorly characterized, particularly where sedimentary and ultramafic influences intersect. Here we present geochemical analyses of vent fluids collected in 2024 from the Jøtul hydrothermal field on the northern Knipovich Ridge. Major element concentrations, dissolved gases, and thermodynamic modeling are used to investigate fluid-rock interactions. The fluids exhibit exceptionally high CH4 concentrations, that exceed those at the Guaymas Basin, and display characteristics typical of sediment-hosted hydrothermal systems, indicating thermal decomposition of organic matter in clastic sediments. In contrast, high H2 (>15 mM) and low H2S concentrations are more typical of ultramafic-hosted fluids, while geological evidence indicates that the vent field lies atop a detachment fault. Thermodynamic modeling suggests that these high H2/H2S ratios may result solely from degradation of organic matter followed by abiotic CH4 oxidation at ~400 °C, rather than from reactions with ultramafic rocks. These results expand the known diversity of sediment-hosted vent fluid compositions and highlight fluid-sediment interaction as an underestimated source of carbon and hydrogen.},
}
TY - JOUR
AU - Diehl, Alexander
AU - Anagnostou, Eirini
AU - Monien, Patrick
AU - Pape, Thomas
AU - Meckel, Eva-Maria
AU - Römer, Miriam
AU - Mezri, Leila
AU - Bach, Wolfgang
AU - Monien, Donata
AU - Hansen, Christian
AU - Röhler, Aaron
AU - Streuff, Katharina
AU - Palinkas, Sabina Strmic
AU - Marcon, Yann
AU - Barrenechea Angeles, Ines
AU - Kleint, Charlotte
AU - Knutsen, Stig‑Morten
AU - Bohrmann, Gerhard
TI - High H2 production in sediment-hosted hydrothermal fluids at an ultraslow spreading mid-ocean ridge
T2 - Communications Earth & Environment
PY - 2026
VL - 7
DO - 10.1038/s43247-025-02962-2
AB - Hydrothermal systems at ultraslow-spreading mid-ocean ridges remain poorly characterized, particularly where sedimentary and ultramafic influences intersect. Here we present geochemical analyses of vent fluids collected in 2024 from the Jøtul hydrothermal field on the northern Knipovich Ridge. Major element concentrations, dissolved gases, and thermodynamic modeling are used to investigate fluid-rock interactions. The fluids exhibit exceptionally high CH4 concentrations, that exceed those at the Guaymas Basin, and display characteristics typical of sediment-hosted hydrothermal systems, indicating thermal decomposition of organic matter in clastic sediments. In contrast, high H2 (>15 mM) and low H2S concentrations are more typical of ultramafic-hosted fluids, while geological evidence indicates that the vent field lies atop a detachment fault. Thermodynamic modeling suggests that these high H2/H2S ratios may result solely from degradation of organic matter followed by abiotic CH4 oxidation at ~400 °C, rather than from reactions with ultramafic rocks. These results expand the known diversity of sediment-hosted vent fluid compositions and highlight fluid-sediment interaction as an underestimated source of carbon and hydrogen.
ER -
