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首页> 外文期刊>Geochemistry, geophysics, geosystems >Receiver function imaging of the mantle transition zone beneath the South China Block
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Receiver function imaging of the mantle transition zone beneath the South China Block

机译:华南地块下方地幔过渡带的受体函数成像

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摘要

Upper mantle discontinuities are influenced by convection-related thermal heterogeneities arising in complex geodynamic settings. Slab rollback of the Pacific plate and mantle upwelling in the Meso-Cenozoic caused the extension and spreading of continental segments in the South China Block leading to profound variations of the local temperature conditions. We processed 201 teleseismic events beneath 87 stations in the Hainan, Guangdong, and Fujian provinces in the South China Block, and extracted 4172 high-quality receiver functions. We imaged the topography of the local mantle discontinuities by using phase-weighted common conversion point stacking of the receiver functions, which effectively improves the P-to-S-converted phases. We found that the average depths of the discontinuities at 410 and 660 km depth are 414 and 657 km, respectively, while no clearly defined discontinuity at 520 km depth was detected. We mapped the thickness of the mantle transition zone (MTZ), which can reflect temperature and/or compositional heterogeneities as well as the presence of water, and discussed possible geodynamic implications. In particular, we found that the MTZ beneath the Leizhou Peninsula in the Hainan province is 42 km thinner than average. This scenario suggests that the Hainan plume is responsible for positive temperature anomalies between approximate to 270 and 380 K and between approximate to 200 and 240 K at the 660 and 410 km discontinuities, respectively. We also observed a prominent uplifting of the 660 km boundary beneath the coast regions that may be indicative of lateral flow of the Hainan plume.
机译:上地幔的不连续性受复杂地球动力学环境中与对流相关的热异质性影响。太平洋板块的板块退缩和中新生代的地幔隆升引起了华南地块大陆部分的扩展和扩散,导致当地温度条件发生了巨大变化。我们在华南地块的海南,广东和福建省的87个站下处理了201次地震事件,提取了4172个高质量的接收器功能。我们通过使用接收器函数的相位加权公共转换点叠加来成像局部地幔不连续性的地形,从而有效地改善了P到S转换的相位。我们发现,在410和660 km深度处的不连续性的平均深度分别为414和657 km,而在520 km深度处未检测到明确定义的不连续性。我们绘制了可以反映温度和/或成分异质性以及水的存在的地幔过渡带(MTZ)的厚度,并讨论了可能的地球动力学意义。特别是,我们发现海南省雷州半岛下方的MTZ比平均水平薄42公里。这种情况表明,在660 km和410 km的不连续点处,海南羽流分别是正温度异常的原因,正温度异常大约在270 K和380 K之间,大约200和240 K之间。我们还观察到沿海地区下方660 km边界明显抬升,这可能表明海南羽流有侧向流动。

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