Earthquake-driven influx of organic matter enhances authigenic carbonate formation in hadal trenches

Shallow marine carbonates are recognized as key agents in deep carbon cycling. However, the formation and burial of carbonates below the carbonate compensation depth still remain poorly understood. Here, we investigate carbonates from the > 7000 m water-depth Japan Trench hadal zone and find widespread authigenic calcium carbonate buried in these ultra-deep sediments. Stable and radiocarbon isotope depletions in the authigenic carbonates indicate an organic carbon (OC) source, likely primarily delivered by deep-sea landslides. Isotopic modeling suggests that subduction of these OC-derived carbonates can impart negative δ13C signatures to fluids released in the NE Japan subduction zone. The OC-derived carbonate flux in the Japan Trench is estimated to reach ~ 28.6 Tg C Myr–1. We propose that earthquake-driven organic matter influx into the hadal zone may have facilitated sustained carbonate production. Thus, OC-derived authigenic carbonates in hadal trenches represent an underappreciated carbon sink and a potential mechanism for transferring OC into the deep Earth. Earthquake-driven organic matter influx into hadal zones facilitates sustained organic carbon-derived carbonate production. The formation of these authigenic carbonates represents both an underappreciated carbon sink and a potential mechanism for transferring OC into the deep Earth.