Homogeneous magnesium isotopic composition of seawater: an excellent geostandard for Mg isotope analysis
Homogeneous magnesium isotopic composition of seawater: an excellent geostandard for Mg isotope analysis
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DOI：
10.1002/rcm.5172
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发表时间：
2011-10-15
影响因子：
2
通讯作者：
Sun, Weidong
中科院分区：
文献类型：
--
作者：
Ling, Ming-Xing;Sedaghatpour, Fatemeh;Sun, Weidong
采用多收集器电感耦合等离子体质谱法（MC-ICP-MS）测定了墨西哥湾40个海水样品和夏威夷西南部1个海水样品的镁（Mg）同位素组成，探讨了海水中镁同位素的均匀性。Mg同位素组成的结果表明,从墨西哥湾的海水均匀,垂直和水平地,平均值δMg-26 = -0.832 + / - 0.068和δMg-25 = -0.432 + / - 0.053 (n = 40 2 sd)——相同的海水从夏威夷(平均Mg-26 = -0.829 + / - 0.037和δMg-25 = -0.427 + / - 0.033)和全球海水的平均文献值(δMg-26 = -0.83 + / - 0.11和δMg-25 = -0.43 + / - 0.06, n = 49岁2 sd)。总体而言，全球海水Mg同位素组成均匀，δ Mg-26 = -0.83 +/- 0.09, δ Mg-25 = -0.43 +/- 0.06 （2SD, n = 90）。海水镁同位素组成主要受河水输入、碳酸盐沉淀和海洋热液相互作用的控制。海水中均匀的Mg同位素组成表明海洋中Mg同位素存在稳态收支，这与Mg的长停留时间（类似于13 Ma）相一致。考虑到海水均质性好、储量大、易于获取和处理进行同位素分析，且同位素组成接近自然变化范围的中间值，在高精度Mg同位素分析中排除分析伪影是一种很好的精度评估地质标准。版权所有：John Wiley & Sons， Ltd。
The magnesium (Mg) isotopic compositions of 40 seawater samples from the Gulf of Mexico and of one seawater sample from the southwest Hawaii area were determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) to investigate the homogeneity of Mg isotopes in seawater. The results indicate that the Mg isotopic composition of seawater from the Gulf of Mexico is homogeneous, both vertically and horizontally, with average values for delta Mg-26 = -0.832 +/- 0.068 and delta Mg-25 = -0.432 +/- 0.053 (n = 40, 2SD) - identical to those of seawater from Hawaii (average delta Mg-26 = -0.829 +/- 0.037 and delta Mg-25 = -0.427 +/- 0.033) and to the average literature values of seawater worldwide (delta Mg-26 = -0.83 +/- 0.11 and delta Mg-25 = -0.43 +/- 0.06, n = 49, 2SD). Collectively, global seawater has a homogeneous Mg isotopic composition with delta Mg-26 = -0.83 +/- 0.09 and delta Mg-25 = -0.43 +/- 0.06 (2SD, n = 90).The magnesium isotopic composition of seawater is principally controlled by river water input, carbonate precipitation and oceanic hydrothermal interactions. The homogeneous Mg isotopic composition of seawater indicates a steady-state budget in terms of Mg isotopes in oceans, consistent with a long Mg residence time (similar to 13 Ma). Considering that seawater is homogeneous, readily available in large amounts, can be easily accessed and processed for isotopic analysis, and has an isotopic composition near the middle of the natural range of variation, it is an excellent geostandard for accuracy assessment to rule out analytical artifacts during high-precision Mg isotopic analysis. Copyright (C) 2011 John Wiley & Sons, Ltd.