[M-IS22] [JJ] 地球掘削科学

[MIS22-P13] 南太平洋環流域の堆積物に含まれる微小金属粒の鉱物学的・地球化学的特徴について（IODP Exp. 329）

*浦本 豪一郎^1,2、諸野 祐樹¹、富岡 尚敬¹、若木 重行¹、和穎 朗太³、上杉 建太朗⁴、竹内 晃久⁴、星野 真人⁴、鈴木 芳生^4,5、光延 聖⁶、菅 大暉⁷、宮本 千尋⁵、高橋 嘉夫⁵、稲垣 史生¹ (1.海洋研究開発機構、2.高知大学、3.農業・食品産業技術総合研究機構、4.高輝度光科学研究センター、5.東京大学、6.愛媛大学、7.広島大学)

キーワード：微小鉱物粒、遠洋性粘土、南太平洋環流域

Ferromanganese minerals widely occur on the seafloor of abyssal plains as nodules consisting of manganese, iron and various trace metal elements. Accumulation and dissolution of the vast mineral deposits play important roles in the global element cycle. However, no clear picture has yet emerged as to the nature of these mineral deposits in deep subseafloor oxic sediments. During the Integrated Ocean Drilling Program (IODP) Expedition 329, we drilled the entire sedimentary sequence at 6 sites in the ultra-oligotrophic region of the South Pacific Gyre (SPG), where dissolved O₂ and aerobic microbial communities are present from the seafloor to the sediment-basement interface [1]. We observed abundant micrometer-scale particles of ferromanganese minerals (Mn-microparticles) in oxic pelagic clay sediments of the SPG over 100 million years. Three-dimensional micro-texture and elemental composition analyses using mass-spectrometric, flow cytometry and synchrotron-based approaches revealed that most Mn-microparticles are poorly crystalline ferromanganese minerals that consist of various trace metals and carbon species, indicating that Mn-microparticles are possibly derived from the past hydrothermal activity and widespread buried in the open-ocean gyre.

[1] D’Hondt et al., Presence of oxygen and aerobic communities from seafloor to basement in deep-sea sediment. Nature Geosciences, 8(4), 299-304, 2015.