Decoupling of chemical and isotopic exchange during magma mixing
Decoupling of chemical and isotopic exchange during magma mixing
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DOI：
10.1038/344235a0
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发表时间：
1990-03
期刊：
影响因子：
64.8
通讯作者：
Charles E. Lesher
中科院分区：
文献类型：
--
作者：
Charles E. Lesher
当不同化学和同位素组成的硅酸盐岩浆接触时，它们的平衡受扩散动力学的控制。在这里，我提出的实验数据表明，碱性和酸性硅酸盐熔体之间，同位素交换进行得比化学均匀化快得多。此外，不同的同位素系统（在这种情况下，锶和钕）表现出不同的平衡速率。在交换过程中达到的瞬态组成状态显着偏离预期的结果为二元混合的两个端员1。这种复杂性必须在解释岩浆混合事件的努力中得到承认，例如涉及基性岩浆对（酸性）大陆地壳的部分熔融。在这种情况下，化学性质不同的岩浆的密切混合受到它们不同粘度的阻碍，但它们确实通过扩散选择性地交换质量。
WHEN silicate magmas of different chemical and isotopie compositions are brought into contact, their equilibration is governed by the kinetics of diffusion. Here I present experimental data showing that, between a basic and an acidic silicate melt, isotopic exchange proceeds much more quickly than chemical homogenization. Moreover, different isotopic systems (in this case, strontium and neodymium) exhibit different rates of equilibration. The transient compositional states reached in the exchange process depart markedly from the results expected for binary mixing of the two end-members1. This complexity must be acknowledged in efforts to unravel episodes of magma mixing, such as involving partial melting of (acidic) continental crust by basic magma. In such cases, the intimate mixing of chemically dissimilar magmas is hindered by their different viscosities, but they do selectively exchange mass by diffusion.