Tellurium stable isotope composition in the surface layer of ferromanganese crusts from two seamounts in the Northwest Pacific Ocean

We present the first report of the concentrations and stable isotope compositions of Te in the surface layer of ferromanganese crusts collected from the slope of two seamounts in the Northwest Pacific Ocean, Takuyo-Daigo and Takuyo-Daisan, which cover water depths from 1000 to 5500 m. The Te concentration in the surface layer of the ferromanganese crusts sharply decreases with increasing depth at shallow regions, but this decrease becomes more gradual at deeper regions. The Te isotope composition exhibits two trends that become (1) lighter with increasing water depth at shallow depths and (2) heavier with increasing water depth at greater depths. These profiles are the same for the two seamounts and indicate two types of correlations between the concentration and isotope composition with water depth. The turning points are located at approximately 2000 m for Takuyo-Daigo and 3200 m for Takuyo-Daisan, which likely correspond to different oxygen minimum zones. Co-precipitation processes with Fe and oxidation involving Mn may be responsible for the variation of Te concentration and isotope composition with water depth. These processes are also related to a change of the dissolved oxygen concentration in ambient seawater. The Te isotope compositions in ferromanganese crusts may therefore serve as a potential proxy for changes of the oxygen minimum zone of paleoceans. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study presents the concentrations and stable isotope compositions of Te in ferromanganese crusts collected from the slope of two seamounts in the Northwest Pacific Ocean. The Te concentration decreases sharply with depth at shallow regions, while the Te isotope composition exhibits two trends depending on water depth. These variations may be related to co-precipitation processes with Fe and oxidation involving Mn, as well as changes in dissolved oxygen concentration in seawater. The Te isotope compositions in ferromanganese crusts could potentially be used as a proxy for changes in the oxygen minimum zone of paleoceans.