Methane-hydrogen-rich fluid migration may trigger seismic failure in subduction zones at forearc depths

Francesco Giuntoli (1) , Luca Menegon (2) , Guillaume Siron (1) , Flavio Cognigni (3) , Hugues Leroux (4) , Roberto Compagnoni (5) , Marco Rossi (3) , Alberto Vitale Brovarone (1, 6)

1 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
2 OsloMet - Oslo Metropolitan University
3 UNIROMA - Università degli Studi di Roma "La Sapienza" = Sapienza University [Rome]
4 UMET - Unité Matériaux et Transformations - UMR 8207
5 UNITO - Università degli studi di Torino = University of Turin
6 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie

Metamorphic fluids, faults, and shear zones are carriers of carbon from the deep Earth to shallower reservoirs. Some of these fluids are reduced and transport energy sources, like H2 and light hydrocarbons. Mechanisms and pathways capable of transporting these deep energy sources towards shallower reservoirs remain unidentified. Here we present geological evidence of failure of mechanically strong rocks due to the accumulation of CH4-H2-rich fluids at deep forearc depths, which ultimately reached supralithostatic pore fluid pressure. These fluids originated from adjacent reduction of carbonates by H2-rich fluids during serpentinization at eclogite-to-blueschist-facies conditions. Thermodynamic modeling predicts that the production and accumulation of CH4-H2-rich aqueous fluids can produce fluid overpressure more easily than carbon-poor and CO2-rich aqueous fluids. This study provides evidence for the migration of deep Earth energy sources along tectonic discontinuities, and suggests causal relationships with brittle failure of hard rock types that may trigger seismic activity at forearc depths.

Domaines: Sciences de la Terre

Francesco Giuntoli, Luca Menegon, Guillaume Siron, Flavio Cognigni, Hugues Leroux, et al.. Methane-hydrogen-rich fluid migration may trigger seismic failure in subduction zones at forearc depths. Nature Communications, 2024, Nature Communications, 15 (1), ⟨10.1038/s41467-023-44641-w⟩. ⟨hal-04445674⟩