Tracing the Hawaiian Mantle Plume by Converted Seismic Waves
Tracing the Hawaiian Mantle Plume by Converted Seismic Waves
复制标题
通过转换的地震波追踪夏威夷地幔柱
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
R. Kind
中科院分区：
文献类型：
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作者：
X. Yuan;Xueqing Li;I. Wölbern;R. Kind
热点和海山链属于全球板块构造的基本组成部分。夏威夷-皇帝海山链被认为是当海洋岩石圈不断地通过位于夏威夷群岛下面的固定地幔柱时形成的。热的浮力物质从一个固定的狭窄干内的很深的地方上升到表面，穿透移动的岩石圈，形成火山海山和岛屿。我们利用地震转换波研究了地幔柱引起的从地表到地幔过渡带深部的地震速度异常。我们应用剪切波（S）接收函数技术来绘制岩石圈厚度图。我们发现，从夏威夷岛（厚度约100 km）沿着岛链到考艾岛（厚度约60 km），岩石圈逐渐减薄，宽度约300 km。在这个区域，我们的数据有利于复兴模型，其中羽返回岩石圈的条件接近洋脊。P-S转换波的分析表明，在夏威夷岛中部130-140 km深处还有一个非常低的S波速度带。在P-S转换中我们还看到，上地幔过渡带在夏威夷岛西南方向约40 km处变薄。我们将这些观测结果解释为夏威夷羽流导管在软流圈和地幔过渡带中的局部效应，温度超过300 °C。过渡带厚度的巨大变化表明夏威夷地幔柱的下地幔起源。
Hotspots and seamount chains belong to the fundamental components of the global plate tectonics. The Hawaii-Emperor seamount chain is believed to have been created when the oceanic lithosphere continuously passed over a stationary mantle plume located under the Hawaiian islands. Hot buoyant material rises from great depth within a fixed narrow stem to the surface, penetrating the moving lithosphere and creating the volcanic seamounts and islands. We use teleseismic converted waves to look at the seismic velocity anomalies caused by the mantle plume from surface down to depths of the mantle transition zone. We applied the shear-wave (S) receiver function technique to map the thickness of the lithosphere. We found a gradual lithospheric thinning from the island of Hawaii (∼100 km thickness) along the island chain to Kauai (∼60 km thickness) with a width of about 300 km. In this zone our data favour the rejuvenation model, in which the plume returns the lithosphere to conditions close to the ocean ridge. The analysis of the P-to-S converted waves indicates an additional zone of very low S-wave velocity starting at a depth of 130–140 km beneath the central part of the island of Hawaii. We also see in the P-to-S conversions that the upper mantle transition zone is thinned by up to ∼40 km to the southwest of the island of Hawaii. We interpret these observations as localized effects of the Hawaiian plume conduit in the asthenosphere and the mantle transition zone with an excess temperature of 300 °C. The large variation in the transition zone thickness suggests a lower mantle origin of the Hawaiian plume.