Active Silica Diagenesis in the Deepest Hadal Trench Sediments
Min Luo, Weiding Li, Sonja Geilert, Andrew W. Dale, Zijun Song, Duofu Chen
Abstract
Abstract Porewater dissolved silicic acid (DSi) concentrations and stable Si isotope compositions (δ 30 Si) together with biogenic silica (bSiO 2 ) contents of sediments in five sediment cores collected from the southern Mariana Trench are presented. These data suggest the occurrence of bSiO 2 dissolution and concomitant authigenic clay formation in three bSiO 2 ‐bearing cores. A reaction‐transport model constrained by the measured geochemical data was applied to quantify the rates of Si turnover. Model results predicted the greatest rates of both bSiO 2 dissolution and authigenic clay formation at the trench axis core that displayed low bSiO 2 contents and abundant detrital materials, suggesting that detrital materials may be a limiting factor for bSiO 2 diagenesis. Model results further predicted that ∼40%–70% of DSi generated by bSiO 2 dissolution is consumed by authigenic clay formation. This is the first study that demonstrates active silica diagenesis in the hadal realm and has implications for understanding benthic Si cycling in deep‐sea settings.