U concentration and 234U/238U of seawater from the Okinawa Trough and Indian Ocean using MC-ICPMS with SEM protocols
U concentration and 234U/238U of seawater from the Okinawa Trough and Indian Ocean using MC-ICPMS with SEM protocols
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DOI：
10.1016/j.marchem.2017.08.001
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发表时间：
2017-11
期刊：
影响因子：
3
通讯作者：
Lisheng Wang;Zhibang Ma;Zhilei Sun;Yejian Wang;Xuefeng Wang;Hai Cheng;Jule Xiao
中科院分区：
文献类型：
--
作者：
Lisheng Wang;Zhibang Ma;Zhilei Sun;Yejian Wang;Xuefeng Wang;Hai Cheng;Jule Xiao
冲绳海槽是在大陆岩石圈内伸展形成的弧后盆地，是东中国海与太平洋之间最重要的洋盆之一。为了限制海水的铀含量和234U/238U，用MC-ICPMS测量了冲绳海槽5个深度的垂直海水剖面，其中2个来自印度洋，1个来自南中国海。该方法使我们能够提供最可靠的海水中铀同位素测量，并大大减少了样本量。结果表明，冲绳海槽海水剖面铀含量为3.153~3.235σ，平均值为3.186±0.040(2σ，n=0.37)，印度洋为3.255~3.283σ，平均值为3.272±0.018(2 ppb，n=0.19)，南中国海区为3.253~3.271，平均值为3.263g±0.018(2 ppb，n=0.018)。同样，我们得到了冲绳海槽、印度洋和南海的δ~(234)U值分别为146.1±11.2、145.1±11.4和145.8±00.5‰，平均值为145.7±01.0‰，在误差范围内与以前的报道吻合良好。对于冲绳海槽的2毫升样本，它给出的平均δ234U为145.8±11.0‰，与在95%可信水平内观察到的7毫升海水的观测结果相同。这些结果表明，δ234U在冲绳海槽中的分布是均匀的，并遵循U保守行为。我们还获得了中国南海西沙群岛Acropora珊瑚的δ~(234)U平均值为146.9±22.1‰(2σ，n=9.6)。这些结果与外海无明显差异，为研究东中国海的环境变化提供了重要的地球化学信息。
The Okinawa Trough, a back-arc basin formed by extension within the continental lithosphere, is one of the most significant ocean basins between the East China Sea and the Pacific Ocean. In an attempt to constrain the U content and the234U/238U of seawater, five depths vertical seawater profiles from the Okinawa Trough, two from the Indian Ocean and one from the South China Sea were investigated by MC-ICPMS. The method allows us to contribute most reliable uranium isotopic measurement in seawater and greatly reduces sample size. Results showed that the U contents of seawater profiles for Okinawa Trough were from 3.153 to 3.235 ppb, with an average value of 3.186 ± 0.040 (2σ, n = 37), Indian Ocean were from 3.255 to 3.283 ppb with a mean value of 3.272 ± 0.018 (2σ, n = 19), and South China Sea were from 3.253 to 3.271 averaging 3.263 ± 0.018 (2σ, n = 3) ppb. Similarly, we obtained δ234U values of 146.1 ± 1.2, 145.1 ± 1.4, and 145.8 ± 0.5‰ for Okinawa Trough, Indian Ocean and South China Sea, with a mean of 145.7 ± 1.0‰, in good agreement with previous reports within the error limits. With two-ml samples in the Okinawa Trough, it gives a mean δ234U of 145.8 ± 1.0‰ which is identical to that observed for 7-ml seawater within the 95% confidence level. These results suggest that the distribution of δ234U is homogeneous in the Okinawa Trough and followed U conservative behavior. We also obtained average δ234U values of 146.9 ± 2.1‰ (2σ, n = 6) for Acropora coral from the Xisha Islands in the South China Sea. All results show no marked differences with the open ocean and provide significant geochemical information for the study of environmental change in the East China Sea.