Ductile deformation during carbonation of serpentinized peridotite

• Published in: Nature Communications
• Main Authors: Menzel, Manuel D., Urai, Janos L., Ukar, Estibalitz, Hirth, Greg, Schwedt, Alexander, Kovács, András, Kibkalo, Lidia, Kelemen, Peter B.
• Other Authors: National Science Foundation (US), European Research Council, Japan Society for the Promotion of Science
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Nature Publishing Group 2022
• Subjects: Oman; Carbon; Carbon dioxide; Carbonic acid; Feedback mechanism; Fluid flow; Magnesite; Mineralization
• Online Access: http://hdl.handle.net/10261/356156; https://doi.org/10.1038/s41467-022-31049-1

Carbonated serpentinites (listvenites) in the Samail Ophiolite, Oman, record mineralization of 1–2 Gt of CO, but the mechanisms providing permeability for continued reactive fluid flow are unclear. Based on samples of the Oman Drilling Project, here we show that listvenites with a penetrative foliation have abundant microstructures indicating that the carbonation reaction occurred during deformation. Folded magnesite veins mark the onset of carbonation, followed by deformation during carbonate growth. Undeformed magnesite and quartz overgrowths indicate that deformation stopped before the reaction was completed. We propose deformation by dilatant granular flow and dissolution-precipitation assisted the reaction, while deformation in turn was localized in the weak reacting mass. Lithostatic pore pressures promoted this process, creating dilatant porosity for CO transport and solid volume increase. This feedback mechanism may be common in serpentinite-bearing fault zones and the mantle wedge overlying subduction zones, allowing massive carbonation of mantle rocks. We thank Michael Kettermann and Yumiko Harigane for sampling onboard Chikyu. Werner Kraus and Jonatan Schmidt are thanked for thin section preparation and technical assistance, and we thank Wolf Achim Kahl for conducting the micro-CT measurements. We are grateful to the Oman Public Authority of Mining for support to conduct fieldwork and sample export. MDM and JLU acknowledge funding by the German Research Foundation (DFG grant UR 64/20-1). This research used samples and data provided by the Oman Drilling Project. The Oman Drilling Project (OmanDP) has been possible through co-mingled funds from the International Continental Scientific Drilling Project (ICDP), the Sloan Foundation—Deep Carbon Observatory (Grant 2014-3-01), the US National Science Foundation (NSF-EAR-1516300), NASA —Astrobiology Institute (NNA15BB02A), the German Research Foundation (DFG: KO 1723/21-1), the Japanese Society for the Promotion of Science (JSPS no:16H06347; and KAKENHI ...