Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG56] Ocean Floor Geosciences

Sun. May 26, 2019 10:45 AM - 12:15 PM A05 (TOKYO BAY MAKUHARI HALL)

convener:Kyoko Okino(Atmosphere and Ocean Research Institute, The University of Tokyo), Chairperson:Keishiro Azami, Erika Tanaka

11:30 AM - 11:45 AM

[SCG56-10] Extended lateral correlation of deep-sea sediments around the Minamitorishima EEZ based on downhole variation of bulk chemical composition

*Erika Tanaka1, Kentaro Nakamura1, Kazutaka Yasukawa1,2, Koichiro Fujinaga2, Koichi Iijima3, Shiki Machida2, Yasuhiro Kato1,2 (1.School of Engineering, The University of Tokyo, 2.ORCeNG, Chiba Institute of Technology, 3.JAMSTEC)

Keywords:REY-rich mud, chemostratigraphy, Minamitorishima Island, pelagic clay

Deep-sea sediments extremely enriched in rare-earth elements and yttrium (REY), showing up to 8,000 ppm of total REY concentration (ΣREY), exist within the Japanese exclusive economic zone (EEZ) near Minamitorishima Island in the western North Pacific Ocean [1, 2]. These deposits have stimulated interest as a new and highly promising mineral resource for REY. However, the number, occurrence depth and maximum ΣREY content of these REY-enriched layers appear to be quite variable, which makes it difficult to directly compare REY content peaks in different cores, and to investigate the geological factors controlling their formation and distribution.

Based on a careful consideration of a large geochemical dataset, we have recently recognized that deep-sea sediments within the Minamitorishima EEZ can be divided into nine types of stratigraphic layers, including three distinct REY peaks, with characteristic chemical compositions [3]. These layers deposited in a specific sequence and have lateral continuity in the Minamitorishima EEZ [3], which enables us to correlate the REY peaks in different cores.

In this study, we newly applied the chemostratigraphy to the piston core samples around the Minamitorishima EEZ collected by the MR16-07 cruise. The multi-elemental analysis suggests that the chemostratigraphy spreads out of the Minamitorishima EEZ and reaches at least ~500 km southeast of Minamitorishima Island.


[1] Iijima et al. (2016) Geochemical Journal, 50, 557–573.

[2] Takaya et al. (2018) Scientific Reports, 8, 1–8.

[3] Tanaka et al., submitted to Ore Geology Reviews.