Periodic Reporting for period 3 - DeepSeep (Deep Serpentinization, H2, and high-pressure abiotic CH4)
Période du rapport: 2024-06-01 au 2025-11-30
More than 90% of the total Earth's carbon is stored at depth. However, our understanding on how this carbon is recycled and affects life on out planet remains largely unconstrained. Among the most important carbon-bearing molecules, methane (CH4) is important because it has a much higher global warming potential with respect to carbon dioxide (CO2). However, the cycling of deep methane inside the Earth has received, surprisingly, little attention. DeepSeep focus on the production and cycling of deep methane produced through the process called "serpentinization", whereby the most abundant rocks on Earth – mantle rocks – react with water to produce a new mineral called serpentine. This process is special because it produces another fundamental fluid phase called molecular hydrogen, or dihydrogen (H2), which is nowadays central in green energy strategies. When serpentinization produces dihydrogen, carbon is converted to methane. The resulting geological fluids, rich in dihydrogen and methane, are among the least explored fluids of deep Earth processes, even though they may have disproportionate effects of global carbon cycling and may have played a key role in the emergence of life on our planet and potentially elsewhere.
DeepSeep aims at identifying the processes, chemical features, and fluxes of dihydrogen and methane produced through the process of serpentinization in the deep Earth today and in deep time, and how these fluids may have contributed to deep subsurface biosphere processes on Earth and potentially beyond.
DeepSeep aims at identifying the processes, chemical features, and fluxes of dihydrogen and methane produced through the process of serpentinization in the deep Earth today and in deep time, and how these fluids may have contributed to deep subsurface biosphere processes on Earth and potentially beyond.
The first 54 months of DeepSeep research have fully satisfied the proposed planning and milestones.
WP1: Three key field campaigns were done in Corsica, Vermont, and Mongolia. Minor field activities were also done. Owing to COVID restrictions, some major field campaigns are postponed to 2024. The field work done so far has provided geological constraints and samples for laboratory analyses. More than 700 kilograms fo rocks have been collected so far for laboratory analyses. Additional samples have been obtained from international collaborators including samples from Japan, New Zealand, USA, China, and many others. The collected field data have allowed identifying a number of CH4 production and migration sites. Several papers have already been published and at least 6 additional ones will be finalized by the end of the project.
WP2: Sample characterization and the setup of the DeepSeep laboratory have been the main and most time-consuming activities during the first reporting period. The team has characterized more than 400 samples at the microscale (purchased optical and electron microscopes). Fluid inclusion characterization has already provided a large dataset on more than 200 samples from different localities. The presence of CH4 and H2 is confirmed in most of them. The setup of instrumentation and analytical protocols for fluid extraction and analysis were successfully concluded in November 2022 and 2023 has provided substantial data collection on natural samples. One paper has been submitted presenting more than 80 fluid inclusion extcraction results, and a second one will be submitted early 2026. Two other manuscripts are in preparation.
WP3: Numerical models aiming at predicting H2 and CH4 production through serpentinization have been completed. One article has been already published, and two additional papers will be submitted soon.
Dissemination: the dissemination of DeepSeep results has started and already includes 20 papers published in international journals, including three papers in Nature Communications. Four manuscripts are currently under review. ten other manuscripts are in preparation. Several abstracts have been presented at international conferences during the first half of the project. Outreach activities have also been done, including radio interview and presentations at national science outreach festivals.
WP1: Three key field campaigns were done in Corsica, Vermont, and Mongolia. Minor field activities were also done. Owing to COVID restrictions, some major field campaigns are postponed to 2024. The field work done so far has provided geological constraints and samples for laboratory analyses. More than 700 kilograms fo rocks have been collected so far for laboratory analyses. Additional samples have been obtained from international collaborators including samples from Japan, New Zealand, USA, China, and many others. The collected field data have allowed identifying a number of CH4 production and migration sites. Several papers have already been published and at least 6 additional ones will be finalized by the end of the project.
WP2: Sample characterization and the setup of the DeepSeep laboratory have been the main and most time-consuming activities during the first reporting period. The team has characterized more than 400 samples at the microscale (purchased optical and electron microscopes). Fluid inclusion characterization has already provided a large dataset on more than 200 samples from different localities. The presence of CH4 and H2 is confirmed in most of them. The setup of instrumentation and analytical protocols for fluid extraction and analysis were successfully concluded in November 2022 and 2023 has provided substantial data collection on natural samples. One paper has been submitted presenting more than 80 fluid inclusion extcraction results, and a second one will be submitted early 2026. Two other manuscripts are in preparation.
WP3: Numerical models aiming at predicting H2 and CH4 production through serpentinization have been completed. One article has been already published, and two additional papers will be submitted soon.
Dissemination: the dissemination of DeepSeep results has started and already includes 20 papers published in international journals, including three papers in Nature Communications. Four manuscripts are currently under review. ten other manuscripts are in preparation. Several abstracts have been presented at international conferences during the first half of the project. Outreach activities have also been done, including radio interview and presentations at national science outreach festivals.
The results obtained during the first three reporting periods largely satisfy the expected DeepSeep outcomes. The final months will serve to finalize the last datasets and publications. Five main successful field campaign have allowed identifying ideal case studies demonstrating the global (time and space) significance of the target processes. The sample characterization performed so far could confirm fundamental high-risk/high-gain research hypotheses, such as the widespread occurrence of deep serpentinization, and the systematic presence of dihydrogen and methane in these rocks. The second half of the project will mark a fundamental step towards another important objective, which is the chemical characterization of deep methane. The setup of the analytical protocols for this key objective of the project have already started during the first reporting period. During 2023, a first, large part of the dataset has been acquired. 2024 will represent a key step in the finalization and interpretation of the dataset.