[M-ZZ41] 海底マンガン鉱床の科学：基礎から応用まで

[MZZ41-04] 南太平洋環流域の堆積物に含まれるマンガン鉱物塊の鉱物学的・地球化学的特徴について

*浦本 豪一郎^1,2、諸野 祐樹²、富岡 尚敬²、若木 重行²、中田 亮一²、和穎 朗太³、上杉 健太朗⁴、竹内 晃久⁴、星野 真人⁴、鈴木 芳生^4,5、光延 聖⁶、白石 史人⁷、菅 大暉⁷、武市 泰男⁸、高橋 嘉夫⁵、稲垣 史生² (1.高知大学、2.海洋研究開発機構、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、8.高エネルギー加速器研究機構)

キーワード：マンガン鉱物塊、遠洋性粘土、南太平洋環流域

Manganese mineral deposits widely occur on the seafloor of abyssal plains as nodules consisting of manganese, iron and various trace metal elements. Accumulation of the vast mineral deposits play important roles in the global manganese cycle. However, no clear picture has yet emerged as to the nature of these minerals in entirely oxic deep-sea 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 in oxic pelagic clay sediments of the SPG over 100 million years. Three-dimensional micro-texture and elemental composition analyses using electron microscopy, mass-spectrometry and synchrotron-based spectroscopy approaches revealed that most Mn-microparticles are poorly crystalline ferromanganese minerals that contain various trace metals and carbon species, indicating that Mn-microparticles are possibly derived from the oxidation and precipitation of dissolved manganese in deep-sea water.
[1] D’Hondt, S., Inagaki, F., Zarikian, C. A., Abrams, L. J., Dubois, N., Engelhardt, T., Evans, H., Ferdelman, T., Gribsholt, B., Harris, R. N., Hoppie, B. W., Hyun, J.-H., Kallmeyer, J., Kim. J., Lynch, J. E., McKinley, C. C., Mitsunobu, S., Morono, Y., Murray, R. W., Pockalny, R., Sauvage, J., Shimono, T., Shiraishi, F., Smith, D. C.,
Smith-Duque, C., Spivack, A. J., Steinsbu, B. O., Suzuki, Y., Szpak, M., Toffin, L., Uramoto, G., Yamaguchi, T. Y., Zhang, G., Zhang, X.-H., and Ziebis, W. Presence of oxygen and aerobic communities from seafloor to basement in deep-sea sediment. Nature Geosciences, 8(4), 299-304, 2015.