Why magnesium isotope fractionation is absent from basaltic melts under thermal gradients in natural settings
Why magnesium isotope fractionation is absent from basaltic melts under thermal gradients in natural settings
复制标题
为什么在自然环境下的热梯度下玄武岩熔体不存在镁同位素分馏
DOI：
10.1017/s0016756819001304
复制
发表时间：
2019-11
影响因子：
2.3
通讯作者：
Liu Jianzhong
中科院分区：
文献类型：
--
作者：
Xu Yingkui;Zhu Dan;Li Xiongyao;Liu Jianzhong
摘要实验室实验表明，硅酸盐熔体中的热梯度会导致同位素分馏，这就是所谓的里克特效应。然而，令人困惑的是，里克特效应还没有在自然样品中记录，因为热梯度通常存在于天然火成岩系统中。为了解决这一矛盾，进行了理论分析和计算。我们发现，里希特效应，通常在实验中看到的完全熔融的硅酸盐，不能应用于自然系统，因为天然火成岩样品更有可能形成部分熔融的岩浆和矿物的存在增加了复杂性的同位素的行为。在这项研究中，我们考虑了两个相关的扩散速率动力学同位素效应，起源于化学扩散，这是缺乏与完全熔融样品的实验。我们对镁同位素进行了详细的计算，结果表明镁同位素的Richter效应被动力学同位素效应所缓冲，镁同位素分馏的总值可以为零甚至不可测。我们的研究提供了一个新的认识同位素的行为过程中的冷却和固化的天然岩浆系统。
Abstract Laboratory experiments have shown that thermal gradients in silicate melts can lead to isotopic fractionation; this is known as the Richter effect. However, it is perplexing that the Richter effect has not been documented in natural samples as thermal gradients commonly exist within natural igneous systems. To resolve this discrepancy, theoretical analysis and calculations were undertaken. We found that the Richter effect, commonly seen in experiments with wholly molten silicates, cannot be applied to natural systems because natural igneous samples are more likely to be formed out of partially molten magma and the presence of minerals adds complexity to the behaviour of the isotope. In this study, we consider two related diffusion-rate kinetic isotope effects that originate from chemical diffusion, which are absent from experiments with wholly molten samples. We performed detailed calculations for magnesium isotopes, and the results indicated that the Richter effect for magnesium isotopes is buffered by kinetic isotope effects and the total value of magnesium isotope fractionation can be zero or even undetectable. Our study provides a new understanding of isotopic behaviour during the processes of cooling and solidification in natural magmatic systems.
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影响因子：
3.9
作者：
R. Latypov
通讯作者：
R. Latypov
DOI：
10.2973/odp.proc.sr.176.011.2002
发表时间：
2002
期刊：
--
影响因子：
--
作者：
Y. Niu;T. Gilmore;S. Mackie;A. Greig;W. Bach
通讯作者：
Y. Niu;T. Gilmore;S. Mackie;A. Greig;W. Bach
影响因子：
8.6
作者：
Lacks, Daniel J.;Goel, Gaurav;Lundstrom, Craig C.
通讯作者：
Lundstrom, Craig C.
影响因子：
--
作者：
F. Teng
通讯作者：
F. Teng
影响因子：
5
作者：
F. Richter;E. Watson;R. Mendybaev;F. Teng;P. Janney
通讯作者：
F. Richter;E. Watson;R. Mendybaev;F. Teng;P. Janney