日本地球惑星科学連合2018年大会

講演情報

[EE] 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-GC45] Volatile Cycles in the Deep Earth - from Subduction Zone to Hot Spot

2018年5月21日(月) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ: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)、羽生 毅(海洋研究開発機構 地球内部物質循環研究分野)、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)

[SGC45-P02] Origin of Helium and CO2 Gas from Natural Carbonated Waters in the North-Eastern Area of South Korea.

*YONG CHEON LEE1CHAN HO JEONG1YU JIN LEE1JUN SIK PARK1SONG MIN OU1 (1.Daejeon Univ.)

キーワード:carbonated waters, CO2 gas, δ13C , 3He/4He ratio

Many carbonated springs are found in Mesozoic granitoids and surrounding rocks in South Korea. Their presence is mainly restricted to the Kangwon and Kyungpook provinces. Discharge of many carbonated waters is mainly related to the geologic structures, i.e., the geologic boundaries, fault and dykes that could be a pathway for the rising of deep-seated CO2 gas.

The composition of carbonated waters can be classified into three chemical types; Ca-HCO3 water, Ca(Na)-HCO3 water, and Na-HCO3 water. Most of the carbonated waters are characterized a high CO2 concentration (PCO2 0.12 atm to 5.21 atm), a slightly acid pH (5.19 to 6.47), and high ion concentration.

Oxygen and hydrogen isotope data indicates that the carbonated waters are of meteoric origin. δ13C data of –6.6 to –0.3‰ suggest that the CO2 gas in carbonated waters is mainly derived from a deep-seated source, but is partly mixed with CO2 derived from carbonate rocks. The 3He/4He ratios of carbonated waters range from 1.51x10-6 to 8.38x10-6. The data are mainly plotted along the air-mantle mixing line on the 3He/4He versus 4He/20Ne diagram. These data strongly supported the deep-seated origin of CO2 gas by δ13C data.