The effects of stress on reactions in the Earth: Sometimes rather mean, usually normal, always important
The effects of stress on reactions in the Earth: Sometimes rather mean, usually normal, always important
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压力对地球反应的影响：有时相当恶劣，通常正常，总是重要
DOI：
10.1111/jmg.12299
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发表时间：
2018
影响因子：
3.4
通讯作者：
Wheeler J
中科院分区：
文献类型：
--
作者：
Wheeler J
压力影响着地球上各个层面的化学过程，但其影响的程度尚有争议。在这里，我给出了一个新的综合理论，描述了应力对化学的影响，详细阐述了材料科学的工作，这是建立在基本热力学定律之上的，并展示了它在地球科学中的意义。存在独立但兼容的关系来描述(1)界面和(2)颗粒内部发生的事情。(1)应力在地球上的主要化学效应是由于沿晶粒界面和不同取向界面之间的正应力变化。对于涉及扩散的反应，这些变化对矿物稳定性的影响大致相当于（摩尔体积）/（反应过程中摩尔体积变化）×（应力变化）的压力变化。体积比通常较大，因此正应力变化的影响总是很重要，因为所有受应力的岩石都有支持不同正应力的界面。在一个受压力的系统中没有全局的化学平衡，因此反应动力学有助于持续的演化，直到应力放松：这种演化可能包括由扩散蠕变和压力溶解引起的变形，可能伴随着新的矿物生长。这些影响与预测涉及流体的反应条件有关，例如蛇纹岩的形成和分解（与地球的挥发性循环有关），以及其他反应，例如环纹岩的分解（与了解660公里地幔不连续有关）。(2)在受应力的固溶体颗粒中，不可能定义所有化学成分的化学势，因为必须指定一种化学成分为“不动”。可以定义“可移动”组分（如交换矢量）的化学势。它取决于“偏摩尔应变”，这是一个二级张量，定义了单位细胞几何形状随组成的变化。在立方晶体中，局部摩尔应变是各向同性的，可移动组分的化学势取决于平均应力。在其他晶体体系中，偏摩尔应变是各向异性的，化学势取决于“加权”平均应力；应力的方向和大小都有影响。我提出“化学古地层测量法”——通过化学方法测量过去压力水平的可能性。实例表明，数百MPa到GPa的应力变化需要产生2%的成分变化，但高应力和/或精确的化学分析将允许该建议进行测试。夹杂物和位错周围的高应力可以作为目标。因此，颗粒内部的加权平均应力的影响相对较小，尽管在解释化学变化方面可能有价值；界面处的正应力在化学过程中起主要作用，其影响十分显著。
Stress affects chemical processes on all scales in the Earth but the magnitude of its effect is debated. Here, I give a new synthesis of the theory that describes the effects of stress on chemistry, elaborating upon work in Materials Science which is built from fundamental thermodynamic laws, and show its significance in Earth Science. There are separate but compatible relationships describing what happens (1) at interfaces and (2) within grains. (1) The main chemical effects of stress in the Earth are due to variations in normal stress along grain interfaces and between interfaces with different orientations. For reactions involving diffusion these variations give effects on mineral stability broadly equivalent to pressure changes of (molar volume)/(molar volume change during reaction) × (stress variation). The volume ratio is generally large and so the effects of normal stress variations are always important since all stressed rocks have interfaces supporting different normal stresses. There is no global chemical equilibrium in a stressed system, so reaction kinetics contribute to ongoing evolution until stresses relax: this evolution can include deformation by diffusion creep and pressure solution, possibly with new mineral growth. These effects are relevant for predicting the conditions for reactions involving fluids, such as serpentinite formation and breakdown (relevant for the Earth's volatile cycles) and for other reactions such as ringwoodite breakdown (relevant for understanding the 660 km mantle discontinuity). (2) Within stressed solid solution grains it is not possible to define chemical potentials of all chemical components since one has to be specified as “immobile.” The chemical potential of a “mobile” component such as an exchange vector can be defined. It depends on the “partial molar strain,” a second rank tensor defining the variation in unit cell geometry with composition. In cubic crystals the partial molar strain is isotropic and the chemical potential of a mobile component depends on mean stress. In other crystal systems the partial molar strain is anisotropic and the chemical potential depends on a “weighted” mean stress; orientation as well as magnitude of stress has an influence. I propose “chemical palaeopiezometry”—the possibility of measuring past stress levels via chemistry. Examples show that stress variations in hundreds of MPa to GPa are required to produce 2% variations in composition but high stresses and/or precise chemical analyses will allow this proposal to be tested. High stresses around inclusions and dislocations could be targeted. So, the weighted mean stress inside grains has an effect which is relatively minor although potentially valuable in explaining chemical variations; the normal stress at interfaces plays the main role in chemical processes and its effects are of significant magnitude.
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影响因子：
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作者：
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DOI：
--
发表时间：
2005
期刊：
影响因子：
--
作者：
J. C. Slattery;D. Lagoudas
通讯作者：
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影响因子：
5
作者：
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受力固体相对于相变的平衡及其地质应用。
DOI：
--
发表时间：
1974
期刊：
影响因子：
--
作者：
P. Robin
通讯作者：
P. Robin