Seismic imaging of melt in a displaced Hawaiian plume
Seismic imaging of melt in a displaced Hawaiian plume
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DOI：
10.1038/ngeo1878
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发表时间：
2013-08
影响因子：
18.3
通讯作者：
C. Rychert;G. Laske;N. Harmon;P. Shearer
中科院分区：
文献类型：
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作者：
C. Rychert;G. Laske;N. Harmon;P. Shearer
夏威夷群岛是热点火山作用的典型例子：当太平洋板块移动穿过固定的地幔柱时，岛链逐渐形成。然而，一些观测结果与热定义板块下方的简单垂直上升流不一致，并且地幔柱-板块相互作用的性质存在争议。在这里，我们使用S到P的地震接收器功能，使用陆地和海底地震仪的网络测量，图像位于夏威夷下110至155公里的熔融富集区的基础。我们发现，这个熔体丰富的区域是最深的100公里以西的夏威夷，这意味着羽撞击在板块在这里，并导致熔融在更深的地幔，而不是直接在下面的岛屿。我们推断，羽流要么在夏威夷西部下方自然垂直上升，要么在岛屿形成时在岛屿下方产生的成分耗尽的根部使其向西偏转。夏威夷羽流的偏移增加了垂直上升到地表的固定羽流的经典模型的复杂性，并表明板内火山下的地幔熔融可能是由岛屿下预先存在的结构引导的。
The Hawaiian Islands are the classic example of hotspot volcanism: the island chain formed progressively as the Pacific plate moved across a fixed mantle plume. However, some observations are inconsistent with simple, vertical upwelling beneath a thermally defined plate and the nature of plume-plate interaction is debated. Here we use S-to-P seismic receiver functions, measured using a network of land and seafloor seismometers, to image the base of a melt-rich zone located 110 to 155 km beneath Hawaii. We find that this melt-rich zone is deepest 100 km west of Hawaii, implying that the plume impinges on the plate here and causes melting at greater depths in the mantle, rather than directly beneath the island. We infer that the plume either naturally upwells vertically beneath western Hawaii, or that it is instead deflected westwards by a compositionally depleted root that was generated beneath the island as it formed. The offset of the Hawaiian plume adds complexity to the classical model of a fixed plume that ascends vertically to the surface, and suggests that mantle melts beneath intraplate volcanoes may be guided by pre-existing structures beneath the islands.