抄録
The interaction between a significant dissolved Mn pool in the oxygen minimum zone and the deeper oxygenated water facilitates the formation of Mn oxides at their interface. Yet, whether such interaction is the direct cause of ferromanganese (Fe-Mn) encrustation remains elusive. Marine Fe-Mn crusts enrich metals including those with high affinity for Mn oxides (e.g., Ce), which provide insights into the origin of Mn oxides. We determine the close association of Ce (~80%) with Mn oxides in marine Fe-Mn deposits and present the Ce isotope data (δ142Ce) in Fe-Mn crusts and seawater from the Pacific Ocean (up to 6,000 m depth) to bridge Mn and Ce cycles. We identify (i) a heterogeneous seawater δ142Ce profile linked to the Mn cycles, and (ii) the crust δ142Ce as an integrated signal of Ce scavenged along the path from the precipitation to the deposition locations of Mn oxides. We find little evidence of sinking Mn oxides in Fe-Mn crusts. Instead, consistent isotopic fractionation between Fe-Mn crusts and the surrounding seawater reflects Ce scavenging by locally formed Mn oxides. Our finding reveals that marine Fe-Mn encrustation is driven by active oxidation and deposition of Mn acros
