Melt-rich lithosphere-asthenosphere boundary inferred from petit-spot volcanoes
Melt-rich lithosphere-asthenosphere boundary inferred from petit-spot volcanoes
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DOI：
10.1130/g35944.1
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发表时间：
2014-11
期刊：
影响因子：
5.8
通讯作者：
J. Yamamoto;J. Korenaga;N. Hirano;H. Kagi
中科院分区：
文献类型：
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作者：
J. Yamamoto;J. Korenaga;N. Hirano;H. Kagi
在古老的大洋岩石圈上发现了年轻的玄武岩丘，即小点火山。根据其地球化学特征，它们可能起源于软流圈的部分熔融。然而，没有关于小斑点形成的深度物源的直接信息。在这里，我们报告了新的地质温压数据的稀有地幔捕虏体发现的小斑点熔岩表现出的地热远高于预期的约。140 Ma的海底，形成了小斑点。如此异常高温的地热表明岩石圈-软流圈边界（LAB）附近的熔体孔隙度一定高达百分之几。通过连续的熔体补充，这种高熔体孔隙率是可能的。由外隆地形引起的超压使熔体沿着LAB水平迁移，并维持熔体连续供应给小点岩浆作用。鉴于海洋盆地的一般年龄-深度关系，富熔体边界区域也可能是一个全球性特征。
Young basaltic knolls have been discovered on the old oceanic lithosphere, namely petit-spot volcanoes. Based on their geochemical signatures, they have presumably originated from partial melts in the asthenosphere. However, there is no direct information on the depth provenance of petit-spot formation. Here we report new geothermobarometric data of rare mantle xenoliths discovered from petit-spot lavas exhibiting a geotherm much hotter than expected for the ca. 140 Ma seafloor on which petit-spots were formed. Such an anomalously hot geotherm indicates that melt porosity around the lithosphere-asthenosphere boundary (LAB) must be as high as a few percent. Such high melt porosity would be possible by continuous melt replenishment. Excess pressure induced by the outer-rise topography enables horizontal melt migration along the LAB and sustains a continuous melt supply to petit-spot magmatism. Given the general age-depth relationship of ocean basins, a melt-rich boundary region could also be a global feature.