11:15 AM - 11:30 AM
[MIS17-03] Surface layer Nd isotopic composition of Fe-Mn crusts collected from the Takuyo-Daigo Seamount and its relationship with ambient seawater
Keywords:ferromanganese (Fe-Mn) crust, Nd isotopic composition, seawater, Takuyo-Daigo Seamount, remotely operated vehicle (ROV)
The Fe-Mn crust samples were collected during three cruises: RV Natsushima NT09-02, RV Kairei KR15-E01, and RV Kairei KR16-01.
The topmost surface (<1 mm thick) sample was leached with either 2.5 M HCl or 1M HCl with H2O2. Nd was separated and purified from the leachate. Subsequently, the Nd isotopic composition was determined with the Neptune Plus housed at JAMSTEC, Yokosuka.
We found that the depth profile of ferromanganese crusts is similar to the vertical seawater profile reported for TPS 24 271-1 station. This fact indicates the surface layers of the Fe-Mn crust reliably reflect seawater values. We also found that our epsilon Nd surface layer profile is consistent with previously reported data for the northern Pacific Ocean. This implies that the seawater Nd isotopic distribution in the northwest to central Pacific is horizontally fairly homogenous below 1000 m and might have been so for about 0.1 to 0.2 Ma.