Seismic evidence for partial melting at the root of major hot spot plumes
Seismic evidence for partial melting at the root of major hot spot plumes
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DOI：
10.1126/science.aan0760
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发表时间：
2017-07
期刊：
影响因子：
56.9
通讯作者：
K. Yuan;B. Romanowicz
中科院分区：
文献类型：
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作者：
K. Yuan;B. Romanowicz
冰岛的熔融根主要的热点羽流是负责玄武岩海洋岛链，如夏威夷。Yuan和Romanowicz使用地震层析成像技术，从地震波中构建了地球内部的X射线图像，以显示冰岛热点羽流的根部部分熔融。部分熔融的区域位于地球的核幔边界附近，用地球物理方法成像一直是一个挑战。这种方法可能适用于具有类似熔融区域的其他热点或下地幔中的其他神秘区域。科学，本期第393页地震层析成像方法探测到冰岛地幔柱根部的部分熔融物质区域。超低速带是地震学在地幔底部探测到的具有极端物质性质的局部区域。它们在地幔动力学中的性质和作用知之甚少。我们使用在核幔边界衍射的剪切波从不同的方向照亮冰岛地幔柱的根。通过波形建模，我们检测到一个大的超低速区，并将其形状限制为轴对称到一个非常好的一阶。因此，我们将其归因于局部增厚，密度和热高于平均水平的层，反映动力学和羽根内的温度升高的部分熔融。这样的结构是很少的，相距甚远，他们可能是一些广泛的地幔柱的根部的特点，在下地幔的大型低剪切速度省断层成像。
Iceland's molten roots Major hot spot plumes are responsible for basaltic ocean island chains such as Hawaii. Yuan and Romanowicz used seismic tomography, which constructs an x-ray–like picture of Earth's interior from seismic waves, to show that the root of Iceland's hot spot plume is partially molten. The partially molten region is located near Earth's core-mantle boundary and has been challenging to image with geophysical methods. This approach may be applicable to other hot spots with similar areas of melts or other enigmatic regions in the lower mantle. Science, this issue p. 393 Seismic tomographic methods detect a region of partially molten material in the root of Iceland’s mantle plume. Ultralow-velocity zones are localized regions of extreme material properties detected seismologically at the base of Earth's mantle. Their nature and role in mantle dynamics are poorly understood. We used shear waves diffracted at the core-mantle boundary to illuminate the root of the Iceland plume from different directions. Through waveform modeling, we detected a large ultralow-velocity zone and constrained its shape to be axisymmetric to a very good first order. We thus attribute it to partial melting of a locally thickened, denser- and hotter-than-average layer, reflecting dynamics and elevated temperatures within the plume root. Such structures are few and far apart, and they may be characteristic of the roots of some of the broad mantle plumes tomographically imaged within the large low-shear-velocity provinces in the lower mantle.