South Pacific mantle plumes imaged by seismic observation on islands and seafloor
South Pacific mantle plumes imaged by seismic observation on islands and seafloor
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DOI：
10.1029/2009gc002533
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发表时间：
2009-11
期刊：
影响因子：
3.7
通讯作者：
D. Suetsugu;T. Isse;S. Tanaka;M. Obayashi;H. Shiobara;H. Sugioka;T. Kanazawa;Y. Fukao;G. Barruol;D. Reymond
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文献类型：
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作者：
D. Suetsugu;T. Isse;S. Tanaka;M. Obayashi;H. Shiobara;H. Sugioka;T. Kanazawa;Y. Fukao;G. Barruol;D. Reymond
南太平洋地区的特点是被称为南太平洋超级井的大面积升高的海底。该地区集中了在白垩纪中期（90-120 Ma）经历过大规模喷发的中板块火山。这些特征表明在南太平洋下方存在大规模的地幔柱，称为南太平洋超级地幔柱。然而，超级羽流的几何形状、起源深度、温度和组成仍然存在争议，主要是因为缺乏记录南太平洋地幔结构的地震学数据。由于地处偏远的海洋环境，该地区的地震台站很少。为了获得更好的超级地幔柱的地震图像，我们在南太平洋的海洋岛屿和海底部署了临时宽带地震仪，这使得该地区地幔结构的最高空间分辨率成为可能。从这一新的地震数据获得的地震图像表明，超大尺度的低速异常（直径约1000公里）位于地幔底部至深度1000公里处，表明超级羽流的存在，而其上方则存在小尺度的低速异常（直径约100公里）。将地震图像与最近基于实验室和数值实验的地幔对流研究进行比较表明，超级羽流可能是一个热的、化学性质不同的地幔穹窿，而小尺度异常可能是穹窿顶部产生的狭窄羽流。该模型可以解释南太平洋热点的各种特征，如海底膨胀、短寿命热点链和大规模火山喷发的周期性。
The South Pacific region is characterized by a broadly elevated seafloor known as the South Pacific superswell. This region has a concentration of midplate volcanoes that experienced massive eruptions in the mid‐Cretaceous period (90–120 Ma). These characteristics suggest the presence of a large‐scale mantle plume beneath the South Pacific, called the South Pacific superplume. The geometry, origin depth, temperature, and composition of the superplume remain controversial, however, mainly due to the lack of seismological data that documents the mantle structure beneath the South Pacific. Seismic stations are sparse in the area due to its remote ocean environment. To obtain a better seismic image of the superplume, we deployed temporary broadband seismographs on oceanic islands and the seafloor in the South Pacific, which made possible the highest spatial resolution that has ever been achieved for the mantle structure beneath the region. The seismic image obtained from this new seismic data indicates that large‐scale low‐velocity anomalies (on the order of 1000 km in diameter), indicative of the superplume, are located from the bottom of the mantle to a depth of 1000 km, and small‐scale low‐velocity anomalies (on the order of 100 km in diameter) are present above it. A comparison of the seismic image with recent mantle convection studies based upon laboratory and numerical experiments suggests that the superplume may be a hot and chemically distinct mantle dome, and that the small‐scale anomalies may be narrow plumes generated from the top of the dome. This model may explain various characteristics of hot spots in the South Pacific, such as the seafloor swell, short‐lived hot spot chains, and the periodicity of massive eruptions.