Noble gas and carbon isotopes in Mariana Trough basalt glasses |
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| Institution: | 1. Key Laboratory of Submarine Geosciences, State Oceanic Administration, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China;2. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;3. Shanghai Jiao Tong University, School of Oceanography, Shanghai 200240, China;4. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geoscience, Wuhan 430074, China;1. CGEO-UNAM; Campus Juriquilla, Juriquilla, Querétaro 76320, Mexico;2. Centro de Investigación y de Estudios Avanzados del I.P.N., P.O. Box l 1-798, Querétaro 76001, Mexico;3. Instituto de Geología-UNAM; Distrito Federal, 04510, Mexico |
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| Abstract: | Noble gas elemental and isotopic compositions have been measured as well as the abundance of C and its isotopic ratios in 11 glasses from submarine pillow basalts collected from the Mariana Trough. The 3He/4He ratios of 8.22 and 8.51 Ratm of samples dredged from the central Mariana Trough (～18°N) agree well with that of the Mid-Ocean Ridge Basalt (MORB) glasses (8.4±0.3 Ratm), whereas a mean ratio of 8.06±0.35 Ratm in samples from the northern Mariana Trough (～20°N) is slightly lower than those of MORB. One sample shows apparent excess of 20Ne and 21Ne relative to atmospheric Ne, suggesting incorporation of solar-type Ne in the magma source. There is a positive correlation between 3He/4He and 40Ar/36Ar ratios, which may be explained by mixing between MORB-type and atmospheric noble gases. Excess 129Xe is observed in the sample which also shows 20Ne and 21Ne excesses. Observed δ13C values of ～20°N samples vary from ?3.76‰ to ?2.80‰, and appear higher than those of MORB, and the corresponding CO2/3He ratios are higher than those of MARA samples at ～18°N, suggesting C contribution from the subducted slab. |
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