Unsolved problems in the lowermost mantle
Unsolved problems in the lowermost mantle
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DOI：
10.1029/2006gl025691
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发表时间：
2006-06
影响因子：
5.2
通讯作者：
K. Hirose;S. Karato;V. Cormier;J. Brodholt;D. Yuen
中科院分区：
文献类型：
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作者：
K. Hirose;S. Karato;V. Cormier;J. Brodholt;D. Yuen
D″层的许多特征可以归因于最近发现的MgSiO3后钙钛矿相，而没有化学不均匀性。它们包括D″顶部的尖锐不连续性、地震各向异性的区域变化和陡峭的克拉珀龙斜坡。然而，一些特征仍然无法解释。与第一原理计算相比，地震学推断的速度跳跃太大，并且不连续性的尖锐性可能需要化学边界。除了从钙钛矿到后钙钛矿的相变之外，化学不均匀性也可能发挥重要作用。相变和化学不均匀性以及随之而来的物理性质的变化，如流变学和热导率，可能在定义D″层的动态稳定性方面发挥竞争作用。揭示相变和化学异常之间的相对作用是研究D″在地球热化学演化中作用的一个突出挑战。
Many characteristics of D″ layer may be attributed to the recently discovered MgSiO3 post‐perovskite phase without chemical heterogeneities. They include a sharp discontinuity at the top of D″, regional variation in seismic anisotropy, and a steep Clapeyron slope. However, some features remain unexplained. The seismically inferred velocity jump is too large in comparison to first principles calculations, and the sharpness of the discontinuity may require a chemical boundary. Chemical heterogeneity may play an important role in addition to the phase transformation from perovskite to post‐perovskite. Phase transformation and chemical heterogeneity and the attendant changes in physical properties, such as rheology and thermal conductivity, are likely to play competing roles in defining the dynamical stability of the D″ layer. Revealing the relative roles between phase transition and chemical anomalies is an outstanding challenge in the study of the role of D″ in thermal‐chemical evolution of the Earth.