[S-CG55] Ocean Floor Geoscience

[SCG55-P02] Chemical characteristics of biogenic apatite in REE-rich mud around Minamitorishima Island based on LA-ICP-MS analysis

*Eisuke Yoshida¹, Daiki Terauchi¹, Kazutaka Yasukawa¹, Kazuhide Mimura², Kentaro Nakamura^1,3, Yasuhiro Kato^1,3 (1.School of Engineering, The University of Tokyo, 2.National Institute of Advanced Industrial Science and Technology, 3.ORCeNG, Chiba Institute of Technology)

Keywords:Minamitorishima Island, LA-ICP-MS analysis, biogenic apatite, REE-rich mud

Rare-earth elements (REEs) are indispensable for advanced electronic devices and environmentally friendly technologies, and their global demand is forecasted to increase significantly in the coming years. In this context, REE-rich mud, a type of deep-sea sediment enriched in REEs [1], has attracted attention as a promising new REE resource. Notably, extremely REE-rich mud has been discovered around Minamitorishima Island, Japan’s easternmost island [2], leading to extensive research on its distribution and origin [2,3]. For example, the REE-rich mud around Minamitorishima can be generally classified into five units (Units I to V) and three REE peak layers, based on multi-elemental chemostratigraphy of bulk chemical composition.
It is well known that the primary host mineral for REEs in REE-rich mud is biogenic apatite, which constitutes fish teeth and bone fragments. Previous studies applied laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze the local chemical composition of biogenic apatite grains that were extracted from several chemostratigraphic units, including REE peak layers, and conducted statistical analyses of the obtained data [4]. These studies revealed that the chemical composition of biogenic apatite in REE-rich mud around Minamitorishima is characterized by four geochemically independent components [4]. However, the chemical characteristics of biogenic apatite in relation to stratigraphic position and grain size have not yet been sufficiently examined.
To address this gap, this study aims to further characterize the geochemical features of biogenic apatite in REE-rich mud around Minamitorishima. We extracted numerous biogenic apatite grains from multiple layers in piston cores collected from this area and conducted LA-ICP-MS analysis to obtain local chemical compositions for major and trace elements. This presentation will report the results and discuss their implications.