Deep Serpentinization and high-pressure abiotic methanogenesis – DeepSeep
The goal of this project is to understand the geological processes responsible for the generation, migration and consumption of deep abiotic hydrocarbons, in particular methane (CH4), formed by alteration of ultramafic rocks at high-pressure conditions.
Alteration of ultramafic rocks is a well-known source of H2 and abiotic CH4 in oceanic settings (e.g. mid-ocean ridges) and in shallow (T< 150 °C) hydrothermal systems on-land. Similar processes may be responsible for the generation of abiotic CH4 on other planets, e.g. Mars, and for the production of pre-biotic organic compounds at the origin of life. At high-pressure conditions, below the biosphere, the possibility for abiotic CH4 to form may have important consequences on the mobility of C from the mantle towards shallower reservoirs on Earth and beyond, as well as on melting and seismicity. However, although laboratory studies suggest CH4 to be stable down to upper mantle conditions, the natural processes responsible for its generation and their manifestations have been largely overlooked. Key issues still remain unanswered and bias our understanding of long-term Earth and planetary processes: (i) What are the geological conditions for deep abiotic methanogenesis? (ii) What are the mechanisms, signatures and markers of deep abiotic CH4 formation? (iii) What are the fluxes of deep abiotic CH4 and how do they migrate towards shallower reservoirs? This proposal aims at answering these questions by defining geological mechanisms and fluxes of deep abiotic CH4 from the record of exhumed high-pressure ultramafic rocks.
The original and synergistic combination of field geology and state-of-the-art analytical techniques down to the nanoscale together with modern theoretical simulations will be used, for the first time, to establish mechanisms, signatures and fluxes of natural deep, abiotic CH4 on Earth, with long-term implications for C cycling, geobiology and planetary exploration, as well as for climate change.
Monsieur Alberto Vitale Brovarone (Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IMPMC Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie
Help of the ANR 149,253 euros
Beginning and duration of the scientific project: December 2017 - 18 Months