Serpentinisation, fluid flow, hydrogen and methane production at magma-poor margins: an example from the West Iberia margin

• Applicant: Professorin Dr. Marta Perez-Gussinye
• Subject Area: Geophysics ; Palaeontology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 396827560

• Final Report Year: 2023

Final Report Abstract

Within this project we have proven that a heuristic data-assimilation approach can be used to simulate with accuracy the deformation and temperature history of rifted margins at fault-block scale. This had led to new understanding regarding the relationship between brittle and ductile deformation, detachment formation and serpentinisation. In the future, this will be important, not only to understand the tectonics during rifting, but also to simulate hydrothermal flow in the geological past, in connection with the search of minerals and natural hydrogen, as we transition to a new carbon-neutral economy. We have dynamically simulated the processes that lead to break-up and the exhumation of the mantle at the continent-ocean transition of magma-poor margins. We have gained insight on the relationship between faulting, serpentinisation and hydrogen production. We found that hydrogen production fluctuates in geological time, with peak production coinciding with the emergence of new faults which cut into fresh mantle rocks. By extrapolating the hydrogen production at the West Iberia-Newfoundland margins to the magma-poor margins of the North Atlantic, we found that the accumulated H2 production could have been as high as ∼4.3 × 10^18 mol (∼8.6 × 10^12 metric tons) prior to opening of the North Atlantic Ocean, at a rate of ∼1.4 ×10^17 mol/Myr. This is one quarter of the total predicted flux produced by the global system of midocean ridges, thus highlighting the significance of H2 generation at magma-poor margins in global H2 fluxes, to hydrogenothropic microbial life, and, perhaps, as a potential energy source. By modelling tectonics at fault-block scale we found out that detachment faults that are observed in the distal sections of magma-poor margins, are not formed in the brittle field, as assumed for the last 20 years, but they are a composite structure, where the deepest fault segments are shear zones that operate in the ductile deformation field. This explains the pattern of mantle serpentinisation observed under the thinned crust at magma-poor margins. We have found that the hydrogen production at the continent-ocean transitions of magma-poor margins is significant and on the order of that at ultra-slow spreading ridges, but occurs at the low temperature end for serpentinization where micro-organisms can thrive.

Publications

• Magmatic sill formation during dike opening. Geology, 50(4), 407-411.
  Liu, Zhonglan & Buck, W. Roger
  
• Lateral coexistence of ductile and brittle deformation shapes magma-poor distal margins: An example from the West Iberia-Newfoundland margins. Earth and Planetary Science Letters, 578, 117288.
  Liu, Zhonglan; Pérez-Gussinyé, Marta; Rüpke, Lars; Muldashev, Iskander A.; Minshull, Timothy A. & Bayrakci, Gaye
  
• Numerical Modeling of Rifting: An Overviewx. Continental Rifted Margins 1, 265-307. Wiley.
  Pérez‐Gussinyé, Marta & Liu, Zhonglan
  
• Mantle serpentinization and associated hydrogen flux at North Atlantic magma-poor rifted margins. Geology, 51(3), 284-289.
  Liu, Zhonglan; Perez-Gussinye, Marta; García-Pintado, Javier; Mezri, Leila & Bach, Wolfgang