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Spatial and temporal variability in Hawaiian hotspot volcanism induced by small-scale convection

机译：小尺度对流引起的夏威夷热点火山的时空变化

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Volcanism far from plate boundaries is often attributed to an underlying mantle plume1-6. However, enigmatic observations of Hawaiian volcanism, such as variations in the volume of erupted volcanic material through time7,8, a geographical asymmetry in the geochemistry of the lavas9-18 and secondary volcanism that occurs far away from the hotspot15-20, cannot be explained by the classical mantle plume concept. Here we present a numerical model of mantle plume upwelling beneath Hawaii. We find that small-scale convection in the ambient mantle can erode the base of the lithosphere, creating a washboard topography on the underside of the plate. As the plate migrates over the upwelling plume, the plume interacts with alternating thicker and thinner sections of lithosphere to generate temporal variations in the flux of erupted volcanic material. The pre-existing washboard topography also causes the plume to spread and melt asymmetrically. In our simulations, this asymmetry in mantle flow generates an asymmetry in the chemistry of the erupted lavas. Finally, a more vigorous type of small-scale convection develops within the spreading plume, generating localized zones of upwelling well away from the hotspot. The associated magmatism is fed by chemically distinct material originating from the edges of the plume conduit. Our results show that shallow processes have an important influence on the character of volcanism fed by deep-rooted mantle plumes.
机译：远离板块边界的火山作用通常归因于潜在的地幔柱1-6。但是，无法解释夏威夷火山的神秘现象，例如火山喷发物质的体积随时间的变化7、8，熔岩地球化学上的地理不对称性9-18和远离热点15-20的次生火山活动。由经典的地幔羽概念。在这里，我们提供了一个位于夏威夷下面的地幔柱上升流的数值模型。我们发现周围地幔中的小规模对流会侵蚀岩石圈的底部，从而在板的底面形成搓板形。当板块在上升的羽流上迁移时，羽流与岩石圈的变厚和变薄部分相互作用，从而在火山喷发物的通量中产生时间变化。预先存在的搓衣板形貌也会导致羽流不对称地扩散和融化。在我们的模拟中，地幔流动的这种不对称性在喷发的熔岩的化学反应中产生了不对称性。最终，在扩散羽流中形成了更剧烈的小尺度对流形式，产生了远离热点的上升流的局部区域。相关的岩浆作用是由来自羽状管道边缘的化学上不同的物质提供的。我们的研究结果表明，浅层过程对根深蒂固的地幔柱带动的火山作用具有重要影响。

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