Multiscale Seismic Tomography of Mantle Plumes and Subducting Slabs
Multiscale Seismic Tomography of Mantle Plumes and Subducting Slabs
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DOI：
10.1007/978-1-4020-5750-2_1
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Dapeng Zhao
中科院分区：
文献类型：
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作者：
Dapeng Zhao
综述了地方性、区域性和全球性地幔热柱和俯冲板块的层析成像研究。将成熟的局部和远震层析成像方法应用于俯冲带，获得了活动弧火山下方上地幔楔体中俯冲板块和岩浆室的清晰图像，表明与弧后岩浆作用和弧后扩张有关的地球动力学系统与深部过程有关，如地幔楔体中的对流循环和俯冲板块的脱水反应。证据还表明，弧岩浆和板片脱水也可能导致俯冲带各种类型地震的发生。由于相变产生的巨大重力不稳定性，大多数板条物质在地幔过渡区停滞不前，最终坍塌到核幔边界。由于大多数热点位于仪器设备较差的大陆和海洋地区，因此只确定了冰岛、黄石和艾菲尔等少数被地震台网覆盖的热点地区的三维地壳和上地幔结构。在这些热点下的上地幔中发现了羽状低速异常。全球对深部地幔热柱的层析成像研究才刚刚开始，还需要更多的努力来成像下地幔热柱的管道。只有结合更有效的地震成像技术和对全球地震网络的密集覆盖，才能彻底了解地幔热柱和俯冲板块的地震结构，特别是在海洋中。
Local, regional and global tomographic studies of mantle plumes and subducting slabs are reviewed. Applications of the well-established local and teleseismic tomography methods to subduction zones have resulted in clear images of subducting slabs and magma chambers in the upper mantle wedge beneath active arc volcanoes, indicating that geodynamic systems associated with arc magmatism and back-arc spreading are related to deep processes, such as convective circulation in the mantle wedge and dehydration reactions of the subducting slab. Evidence also shows that arc magma and slab dehydration may also contribute to the generation of various types of earthquakes in subduction zones. Most of the slab materials are stagnant in the mantle transition zone before finally collapsing down to the core-mantle boundary as a result of large gravitational instability from phase transitions. Because most hotspots are located in poorly instrumented continental and oceanic regions, 3-D crust and upper mantle structure is determined for only a few hotspots such as Iceland, Yellowstone and Eifel which are covered by seismic networks. Plume-like low-velocity anomalies are revealed in the upper mantle under those hotspots. Global tomographic studies of deep mantle plumes have just started, and more efforts are needed to image the conduits of the lower-mantle plumes. A thorough understanding of the seismic structure of mantle plumes and subducting slabs will only be achieved by a combination of more effective seismic imaging techniques and dense coverage of global seismic networks, particularly in the oceans.