Gas compositions and helium isotopic ratios of fluid samples around Kueishantao, NE offshore Taiwan and its tectonic implications

Tsanyao Frank Yang, Tefang Faith Lan, Hsiao Fen Lee, Ching Chou Fu, Pei Chuan Chuang, Ching Hua Lo, Cheng Hong Chen, Chen Tung Arthur Chen, Chao Shing Lee

研究成果: 雜誌貢獻期刊論文同行評審

81 引文 斯高帕斯(Scopus)

摘要

Kueishantao is a Holocene volcanic islet (<7,000 yrs) located at NE offshore Taiwan, and tectonically is part of western extension of the Okinawa Trough. Magmatic activities are considered very active around this area on the basis of the fact that on-land fumaroles and submarine hydrothermal systems are prevailing currently. Representative bubble gas samples from submarine hydrothermal vents were collected for gas composition and helium isotope analysis. The gases show similar compositions of low temperatre fumaroles in the world, i.e., with high CO2 and H2S but low SO2 and HCl contents. They exhibit consistent high 3He/4He ratios (7.3-8.4 RA, where RA is the 3He/4He ratio of air), probably the highest 3He/4He values of gases ever reported in active hydrothermal areas of the western Pacific region. Meanwhile, seawater samples around Kueishantao and other fluid samples from I-Lan Plain, the land area closest to the Kueishantao and also the southernmost part of the Okinawa Trough, show a significant excess of 3He compositions as well. This indicates that the mantle component plays an important role for their gas sources, and implies that the mantle fluids may have invaded into I-Lan Plain. The westward opening of the Okinawa Trough may have caused thinning of the continental crust and produced deep normal faults and hence, the primordial 3He is able to degas from mantle source region without significant crust contamination.

原文???core.languages.en_GB???
頁(從 - 到)469-480
頁數12
期刊GEOCHEMICAL JOURNAL
39
發行號5
DOIs
出版狀態已出版 - 2005

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