Modeling olivine CPO evolution with complex deformation histories: Implications for the interpretation of seismic anisotropy in the mantle
Modeling olivine CPO evolution with complex deformation histories: Implications for the interpretation of seismic anisotropy in the mantle
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DOI：
10.1002/2015gc005964
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发表时间：
2015-10
期刊：
影响因子：
3.7
通讯作者：
Y. Boneh;L. Morales;É. Kaminski;P. Skemer
中科院分区：
文献类型：
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作者：
Y. Boneh;L. Morales;É. Kaminski;P. Skemer
将地震各向异性与地幔流动联系起来需要对橄榄石晶体择优取向（CPO）的发展和演化有详细的了解。最近的实验和现场研究表明，橄榄石CPO演化强烈依赖于综合变形历史，这可能会导致相应的地震各向异性应如何解释的差异。在这项研究中，两个广泛使用的CPO演化的数值模型-D-雷克斯和VPSC-进行评估，以进一步研究变形历史对橄榄石结构和地震各向异性的影响。在以前的实验工作的基础上，模型开始与几个不同的CPO模拟独特的变形历史。值得注意的是，与预先存在的CPO相比，在没有预先存在的纹理的情况下生成的CPO，模型的演化方式不同。此外，在每个模型中的CPO作为应变的函数不同地演变。数值模拟与Boneh和Skemer（2014）的实验室实验进行了比较。一般来说，D-雷克斯和VPSC模型能够重现实验观察到的CPO，尽管模型显著高估了CPO的强度，并且在某些情况下产生与实验观察到的不同的CPO。根据与实验的比较，D-雷克斯的推荐参数为：M* = 10，λ* = 5，χ = 0.3，VPSC的推荐参数为：α = 10-100。数值模拟证实，CPO演化橄榄石是高度敏感的初始CPO的细节，即使在应变大于2。这些观察结果意味着，有一个很长的瞬态间隔CPO重新排列，必须仔细考虑在复杂的构造环境中的地震各向异性的建模或解释。
Relating seismic anisotropy to mantle flow requires detailed understanding of the development and evolution of olivine crystallographic preferred orientation (CPO). Recent experimental and field studies have shown that olivine CPO evolution depends strongly on the integrated deformation history, which may lead to differences in how the corresponding seismic anisotropy should be interpreted. In this study, two widely used numerical models for CPO evolution—D‐Rex and VPSC—are evaluated to further examine the effect of deformation history on olivine texture and seismic anisotropy. Building on previous experimental work, models are initiated with several different CPOs to simulate unique deformation histories. Significantly, models initiated with a preexisting CPO evolve differently than the CPOs generated without preexisting texture. Moreover, the CPO in each model evolves differently as a function of strain. Numerical simulations are compared to laboratory experiments by Boneh and Skemer (2014). In general, the D‐Rex and VPSC models are able to reproduce the experimentally observed CPOs, although the models significantly over‐estimate the strength of the CPO and in some instances produce different CPO from what is observed experimentally. Based on comparison with experiments, recommended parameters for D‐Rex are: M* = 10, λ* = 5, and χ = 0.3, and for VPSC: α = 10–100. Numerical modeling confirms that CPO evolution in olivine is highly sensitive to the details of the initial CPO, even at strains greater than 2. These observations imply that there is a long transient interval of CPO realignment which must be considered carefully in the modeling or interpretation of seismic anisotropy in complex tectonic settings.