Geochemical Journal, Vol. 51 (No. 1), pp. e1-e7, 2017
Hiroshi Amakawa,1* Akira Usui,2 Koichi Iijima1 and Katsuhiko Suzuki1
1Project Team for Development of New-generation Research Protocol for Submarine Resources, Japan Agency for Marine-Earth Science Technology (JAMSTEC), 2-15, Natsushima-cho, Yokosuka-shi, Kanagawa 237-0061, Japan
2Department of Geology, Kochi University, 2-5-1, Akebono-cho, Kochi-shi, Kochi 780-8520, Japan
(Received October 5, 2016; Accepted December 10, 2016; Online published January 13, 2017)
The neodymium (Nd) isotopic composition of the surface layers of eleven ferromanganese crust samples collected from the Takuyo-Daigo Seamount (northwest Pacific Ocean) was determined. This is the first systematic study of the Nd isotopic composition of ferromanganese crusts collected by remotely operated vehicles (ROVs) from a single seamount over water depths of 1000–5400 m, representing intermediate to deep water masses in the ocean. We found that the depth profile of ferromanganese crusts is similar to the vertical seawater profile reported for a station close to the seamount. This similarity suggests that Nd in the surface layer of the ferromanganese crust is directly supplied by ambient seawater and reflects the oceanic water mass structure in the region. These samples are suitable for determining time-series Nd isotopic data to study past ocean circulation of intermediate to deep water masses in the northern Pacific.
Key words: ferromanganese (Fe-Mn) crust, Nd isotopic composition, seawater, Takuyo-Daigo Seamount, remotely operated vehicle (ROV)