HR: 0800h
AN: V51C-1499    [Abstracts]
TI: Hydrothermal plumes at the Myojinsho submarine caldera, the Shicito-Iwojima Ridge, Izu-Bonin Arc
AU: * OKAMURA, K
EM: okamurak@scl.koto-u.ac.jp
AF: ICR, Kyoto University, Gokasho Uji, Kyoto, 611-0011 Japan
AU: TOKI, T
EM: toki@ori.u-tokyo.ac.jp
AF: ORI, University of Tokyo, 1-15-1, Minamidai, Nakano, Tokyo, 164-8639 Japan
AU: KIM, S
EM: shkim@kordi.re.kr
AF: Korea Ocean Research & Development Institute, 1270 Sadong Ansan, Kyunggido, 425-744 Korea, Republic of
AU: URA, T
EM: ura@iis.u-tokyo.ac.jp
AF: IIS, University of Tokyo, 4-6-1, Komaba, Meguro, Tokyo, 153-8505 Japan
AU: TAMAKI, K
EM: tamaki@geosys.t.u-tokyo.ac.jp
AF: Faculty of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo, 113-8656 Japan
AU: Nagahashi, K
V51C-1499 AF: Mitsui Engineering and Shipbuilding Co., Ltd, Tama, Tamano, Okayama, 706-0012 Japan
AB: For the purpose of locating hydrothermaly active site, water column anomalies of manganese concentrations were searched in the Myojinsho submarine caldera (31°53'N, 139°57'E), the Shichito-Iwojima Ridge, Izu-Bonin Arc, during KAIREI (JAMSTEC) KR05-11 cruise in August 2005. An in-situ manganese analyzer GAMOS and CTD attached on autonomous underwater vehicle (AUV) r2D4 (IIS, Univ. Tokyo) were used for the plume survey. We could find manganese anomalies inside the caldera by intensive progressive ascent and descent observations (Prog-AD), similar movement with tow-yo by CTD rosette sampler, using AUV r2D4. The manganese anomalies have four maxima at 630m, 680m, 750m and 850m in depth with maximum concentration of 250 nM manganese. These high manganese enrichment is considered to be due to contribution of hydrothermal manganese. The slope of seawater density at 300 - 700m and 700 - 1,100m in depth is 0.033 and 0.001g/cm3 per meter, respectively. It changed rapidly in the point of 700m in depth, so it is difficult for hydrothermal plume from deep site (>700m) to go up to 700m in depth or more. The shallow plumes (630m and 680m in depth), therefore, come from shallower site than deep plumes (750m and 850m in depth).
DE: 4835 Marine inorganic chemistry (1050)
DE: 4875 Trace elements (0489)
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8440 Calderas
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005