Inferring Earth’s discontinuous chemical layering from the 660-kilometer boundary topography
Inferring Earth’s discontinuous chemical layering from the 660-kilometer boundary topography
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DOI：
10.1126/science.aav0822
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发表时间：
2019-02
期刊：
影响因子：
56.9
通讯作者：
Wenbo Wu;S. Ni;J. Irving
中科院分区：
文献类型：
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作者：
Wenbo Wu;S. Ni;J. Irving
地球内部具有不同物理性质的岩石之间的边界来自晶体结构的变化或化学成分的变化。Wu等人研究了地球上地幔和下地幔之间边界的粗糙度，认为这是由于矿物结构的变化而形成的（见Houser的观点）。令他们惊讶的是，在某些地方，边界具有小尺度的粗糙度，需要边界上方和下方的化学差异。这一观测结果提供了部分阻塞地幔环流的证据，导致上地幔和下地幔之间的一些化学差异。《科学》，本期第736页;另见第696页地球上地幔和下地幔之间的粗略边界表明地幔循环部分受阻。固体地球中某些界面的地形或深度变化可以为我们的地球内部动力学提供重要的见解。虽然地球上下地幔之间660公里边界的中长期地形变化得到了很好的研究，但小尺度测量更具挑战性。我们发现了一个令人惊讶的数量地形在短长度尺度沿着660公里的边界在某些地区使用散射P 'P'地震波。我们的观测需要在短尺度粗糙度高的区域进行化学分层。相比之下，我们没有看到这样的小规模地形沿着410公里的边界在上地幔。我们的发现支持上地幔和下地幔之间部分阻塞或不完善的循环的概念。
Inferring blocked mantle convection The boundaries between rocks with different physical properties in Earth's interior come from either a change in crystal structure or a change in chemical composition. Wu et al. examined the roughness of the boundary between Earth's upper and lower mantle, thought to form from a change in mineral structure (see the Perspective by Houser). To their surprise, in some locations, the boundary has small-scale roughness that requires some chemical difference above and below the boundary. This observation provides evidence of partially blocked mantle circulation that leads to some chemical differences between the upper and lower mantle. Science, this issue p. 736; see also p. 696 A rough boundary between Earth’s upper and lower mantle suggests partially blocked mantle circulation. Topography, or depth variation, of certain interfaces in the solid Earth can provide important insights into the dynamics of our planet interior. Although the intermediate- and long-range topographic variation of the 660-kilometer boundary between Earth’s upper and lower mantle is well studied, small-scale measurements are far more challenging. We found a surprising amount of topography at short length scale along the 660-kilometer boundary in certain regions using scattered P'P' seismic waves. Our observations required chemical layering in regions with high short-scale roughness. By contrast, we did not see such small-scale topography along the 410-kilometer boundary in the upper mantle. Our findings support the concept of partially blocked or imperfect circulation between the upper and lower mantle.