Mn-micronodules from the sediments of the Clarion-Clipperton zone (Pacific Ocean): Origin, elemental source, and Fe-Cu-Zn-isotope composition

Mn- micronodules and nodules of the Clarion-Clipperton zone (Pacific Ocean) are composed 10 Å 7 phyllomanganates, δ-MnO2. The Mn-micronodules built fine concentric growth layers three types (1, 2a, 2b) according to their Mn/Fe ratio Ni, Cu, Co content. Applying previously developped geochemical discrimination approaches we found that were diagenetic precipitates a result suboxic diagenesis, whereas paired Mn-nodules diagenetic‑hydrogenetic formations. most common (type 2) within suboxic-diagenetic, rare 1) mixed hydrogenetic precipitates. formation seems be fluctuation oxic-suboxic front in sediment since Last Glacial Period (LGP). migration close seawater/sediment boundary during LGP has likely resulted reduction Mn4+ other elements upward diffusion. Post-LGP deepening seemingly led re-oxidation Mn2+ pore waters Mn-micronodule precipitation. quantitative re-mobilization seawater-derived Cesolid phase (positive Ce anomaly) its subsequent sequestration by positive anomaly Ce-deficient water. This deficiency was recorded (negative or no anomaly). source bottom seawater. processes major control on Fe-Cu-Zn isotope composition nodules. Measured Fe-isotope can equally explained Considering our mineralogical data would suggest rather than Mn-micronodules: sedimentary Fe sediment, fractionation Fe-isotopes produces an isotopically light dissolved pool, which leads both (−0.63 −0.27‰). preferential scavenging 63Cu from seawater Mn-Fe-oxyhydroxides accounts for Cu-isotope hydrogenetic-diagenetic (+0.21 − +0.35‰), is lighter identical oxidative dissolution Cu-containing minerals, release heavy Cuaq2+ record this pool Mn-micronodules. have Zn-isotope (+0.75 +0.87‰) heavier interpreted equilibrium partitioning between adsorbed Zn: sorption 66Zn Fe-Mn-oxyhydroxides surfaces. Preferential adsorption Zn Mn-nodules. lack robust assessment abundance volume unit insufficient prevents meaningful estimation resource potential.