日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-GC 固体地球化学

[S-GC40] Volatile Cycles in the Deep Earth - from Subduction Zone to Hot Spot

2019年5月29日(水) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:角野 浩史(東京大学大学院総合文化研究科広域科学専攻相関基礎科学系)、羽生 毅(海洋研究開発機構 地球内部物質循環研究分野)、佐野 有司(東京大学大気海洋研究所海洋地球システム研究系)、Gray E Bebout(Lehigh University)

[SGC40-P08] Helium isotopes in Tachibana Bay and Shimabara Bay, Nagasaki

*Ma. Teresa Escobar1Yama Tomonaga2Hajime Obata1Shigenobu Takeda3Naoto Takahata1Yuji Sano1 (1.Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwanoha, Kashiwa, Chiba, Japan、2.Eawag,, Swiss Federal Institute of Aquatic Science and Technology, Department of Water Resources and Drinking Water, Überlandstrasse 133 CH-8600 ,Dübendorf, Switzerland、3.Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan)

キーワード:Helium Isotopes, Hydrothermal vents, Tachibana Bay

Noble gases are powerful tracers to study physical transport processes in aquatic system. Moreover, helium isotopes have been shown to be very useful to infer the origin of fluids. Shimabara Peninsula is located on western side of the Beppu-Shimabara graben in Kyushu, SW Japan. In the region, there are some hot springs and groundwaters which indicate magmatic helium with high 3He/4He ratio. Although some researchers report helium isotopic ratio on land, there is no data in the sea.

The surrounding bays around Shimabara Peninsula in Nagasaki were recently studied for the existence of hydrothermal springs and vents. Physico-chemical properties characteristic of hydrothermal activity were detected on the seafloor. For this study, we use helium isotopes to detect the occurrence of hydrothermal springs on the seafloor in both Tachibana Bay and Shimabara Bay. Samples were collected using a CTD-CMS system and analyzed using a Noble Gas Mass Spectrometer. Our data supplements the discovery of hydrothermal venting along known faults on the seafloor. We present the results of noble gas measurements conducted on water samples and discuss the relationship between our observations and the tectonic setup of the surrounding region.