Time evolution of chemical exchanges during mixing of rhyolitic and basaltic melts
Time evolution of chemical exchanges during mixing of rhyolitic and basaltic melts
复制标题
流纹岩和玄武岩熔体混合过程中化学交换的时间演化
DOI：
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发表时间：
2013
影响因子：
3.5
通讯作者：
Donald Bruce Dingwell
中科院分区：
文献类型：
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作者：
D. Morgavi;D. Perugini;C. P. Campos;W. Ertel;Donald Bruce Dingwell
我们介绍了使用天然玄武岩和流纹岩熔体进行的第一组混沌混合实验。混合过程是由最近开发的一种设备触发的，该设备在熔体中产生混乱的流线，模拟自然界中岩浆混合的发展过程。在受控混沌动力学条件下进行了时间序列混合实验，研究了熔体之间的物理动力学和化学交换的相互作用。用电子探针和激光烧蚀电感耦合等离子体质谱详细研究了常量元素和微量元素的变化。通过计算浓度变化随时间的减小来估计各元素在混合过程中的迁移率。常量元素方差和痕量元素方差均呈指数衰减，指数函数的指数值表示元素的迁移率。我们的结果证实并量化了不同的化学元素在熔体中如何以不同的速度均匀。在许多已发表的元素间图中，元素在混合系统中的不同迁移率被认为是化学元素关联度高度可变(线性、非线性或分散)的原因。具有相似迁移率的元素往往是线性相关的，而随着迁移率差异的增加，地块逐渐变得更加非线性和/或分散。这项研究的结果表明，浓度变化的衰减实际上是一个强有力的工具，可以获得对硅酸盐熔体混合过程中化学交换的新见解。浓度变化是控制化学元素流动性的所有可能因素(如粘度、成分和流体动力状态)的影响的一种表达，因此可以作为一种额外的岩石学工具来解决岩浆混合过程的巨大复杂性。
We present the first set of chaotic mixing experiments performed using natural basaltic and rhyolitic melts. The mixing process is triggered by a recently developed apparatus that generates chaotic streamlines in the melts, mimicking the development of magma mixing in nature. The study of the interplay of physical dynamics and chemical exchanges between melts is carried out performing time series mixing experiments under controlled chaotic dynamic conditions. The variation of major and trace elements is studied in detail by electron microprobe and Laser Ablation ICP-MS. The mobility of each element during mixing is estimated by calculating the decrease in the concentration variance in time. Both major and trace element variances decay exponentially, with the value of exponent of the exponential function quantifying the element mobility. Our results confirm and quantify how different chemical elements homogenize in the melt at differing rates. The differential mobility of elements in the mixing system is considered to be responsible for the highly variable degree of correlation (linear, nonlinear, or scattered) of chemical elements in many published inter-elemental plots. Elements with similar mobility tend to be linearly correlated, whereas, as the difference in mobility increases, the plots become progressively more nonlinear and/or scattered. The results from this study indicate that the decay of concentration variance is in fact a robust tool for obtaining new insights into chemical exchanges during mixing of silicate melts. Concentration variance is (in a single measure) an expression of the influence of all possible factors (e.g., viscosity, composition, and fluid dynamic regime) controlling the mobility of chemical elements and thus can be an additional petrologic tool to address the great complexity characterizing magma mixing processes.