[M-IS17] [JJ] 海底マンガン鉱床の科学：基礎から応用まで

[MIS17-P06] 伊豆小笠原弧における現世および過去の熱水起源マンガン酸化物の化学組成

*山岡 香子¹、臼井 朗^2,1 (1.産業技術総合研究所地質情報研究部門、2.高知大学海洋コア総合研究センター)

キーワード：マンガン酸化物、海底熱水活動

This study investigated Holocene and fossil hydrothermal manganese deposits in the Izu-Ogasawara arc. Mineralogically, these deposits comprise 10 Å and 7 Å manganate minerals, and the fossil samples showed higher 10 Å stabilities. Chemical compositions of the Holocene samples are typical of other hydrothermal manganese deposits, including low Fe/Mn ratios, low trace metals, and low rare earth elements. Although the fossil samples generally have similar chemical characteristics, they exhibit significant enrichment in Ni, Cu, Zn, Cd, Ba, REE, Tl, and Pb contents. Furthermore, the chondrite-normalized REE patterns showed more light REE enrichment trends. These chemical characteristics suggest post-depositional uptake of these metals from seawater.