[M-ZZ41] Marine manganese deposits: from basic to applied sciences

[MZZ41-P04] Vertical profile of neodymium isotopic composition in the oceanic region close to the Takuyo-Daigo Seamount

*Hiroshi Amakawa¹, Yusuke Fukami¹, Junji Torimoto¹, Tatsuo Nozaki², Koichi Iijima², Akira Usui³, Katsuhiko Suzuki² (1.Japan Agency for Marine-Earth Science Technology Research and Development (R&D) Center for Submarine Resources, 2.Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, 3.Marine Core Research Center, Kochi University)

Keywords:ferromanganese crust, Nd isotopic composition, seawater, Takuyo-Daigo Seamount, remotely operated vehicle

Ferromanganese crusts, which are chemical precipitates occurring on the ocean floor and seamount, are known to be rich in lanthanides including neodymium (Nd). The major source of lanthanides in the surface layer ferromanganese crust is ambient seawater. However, whether the lanthanides in ferromanganese crusts are supplied from ambient seawater or from the whole water column above ferromanganese crusts were not clearly presented. To identify the source of lanthanides (Nd) in the surface layer of ferromanganese crusts, the vertical profile of seawater Nd isotopic composition was determined for a location near the Takuyo-Daigo Seamount (21°59.2´N, 153°56.0´E) in the northwest Pacific Ocean. The data were compared with those of the surface layer ferromanganese crust obtained from the Takuyo-Daigo Seamount by remotely operated vehicles (ROVs), whose sampling depths ranged from 965 m to 5385 m. The seawater Nd isotopic composition profile was similar to the surface layer Nd isotopic composition of ferromanganese crusts within analytical errors. This confirms that Nd in the surface layer of ferromanganese crusts is supplied directly by ambient seawater.