• ISSN 2097-1893
  • CN 10-1855/P
俞春泉,李娟,杨凡,张炎. 2023. 地幔过渡带间断面结构地震学成像研究进展. 地球与行星物理论评(中英文),54(3):318-338. doi: 10.19975/j.dqyxx.2022-034
引用本文: 俞春泉,李娟,杨凡,张炎. 2023. 地幔过渡带间断面结构地震学成像研究进展. 地球与行星物理论评(中英文),54(3):318-338. doi: 10.19975/j.dqyxx.2022-034
Yu C Q, Li J, Yang F, Zhang Y. 2023. Advances in seismic imaging of mantle transition zone discontinuities. Reviews of Geophysics and Planetary Physics, 54(3): 318-338 (in Chinese). doi: 10.19975/j.dqyxx.2022-034
Citation: Yu C Q, Li J, Yang F, Zhang Y. 2023. Advances in seismic imaging of mantle transition zone discontinuities. Reviews of Geophysics and Planetary Physics, 54(3): 318-338 (in Chinese). doi: 10.19975/j.dqyxx.2022-034

地幔过渡带间断面结构地震学成像研究进展

Advances in seismic imaging of mantle transition zone discontinuities

  • 摘要: 地幔过渡带位于410-km和660-km两个地震学间断面之间,是深入认识地球内部温度结构、物质组成以及动力学演化过程的关键区域. 地幔过渡带的上下界面分别对应橄榄石到瓦兹利石和林伍德石到布里奇曼石和铁方镁石的矿物相变. 本文总结了地幔过渡带间断面结构的主要地震学研究方法以及研究进展. 这些方法包括SS和PP前驱波方法、接收函数方法、ScS多次反射波方法、P'P'前驱波方法、三重震相波形模拟方法、背景噪声体波干涉成像方法等. 总体而言,地幔过渡带的厚度与地幔过渡带速度在大尺度结构上存在正相关性,表明两者都主要受控于温度结构,与橄榄石矿物相变预测一致. 然而,地震学观测得到的410-km和660-km间断面的绝对深度和几何形态则缺乏相关性,可能是由于地幔过渡带上下界面处的横向温度变化特征并不一致或者由于水含量和化学成分等差异所导致. 410-km和660-km间断面的强度(包括速度、密度和波阻抗跳跃值)和宽度主要受到地幔过渡带化学成分和水含量的影响. 一些地震学研究还探测到了地幔过渡带内部的520-km和560-km间断面,前者被认为由瓦兹利石到林伍德石的相变所导致,而后者可能与钙-钙钛矿从超硅石榴子石中出溶有关. 地幔过渡带附近的低速层可能与过渡带物质进入上下地幔发生脱水熔融存在一定联系. 尽管地幔过渡带研究取得了长足进展,但仍有许多重要科学问题悬而未决. 精确可靠的地幔过渡带地震学成像结果可以为这些问题提供关键信息,但同时也需要与矿物物理学、地球动力学、地球化学等学科交叉融合. 本文最后对未来的地幔过渡带地震学研究方向进行了展望.

     

    Abstract: Located between the 410-km and 660-km discontinuities, the mantle transition zone is the key region for understanding the thermal and chemical structure and the dynamic evolution of the Earth’s mantle. The top and bottom boundaries of the mantle transition zone correspond to mineral phase transitions from olivine to wadsleyite and ringwoodite to bridgmanite and ferropericlase, respectively. This paper summarizes the main seismological methods for studying and related research progress of the mantle transition zone discontinuities. These methods include SS and PP precursors, receiver functions, ScS reverberations, P'P' precursors, waveform modeling of seismic triplications, reflected body waves retrieved from ambient noise interferometry, etc. Overall, there is a positive correlation between the thickness of the mantle transition zone and velocity perturbations in the mantle transition zone on the large-scale structure, indicating that they are both mainly controlled by mantle temperature, consistent with the prediction of olivine phase transitions. However, the lack of negative correlation between 410-km and 660-km discontinuity topography, which is expected from olivine phase transitions, suggests that either the thermal structure is not coherent across the mantle transition zone vertically or there are lateral varitions in water content or mantle chemical composition. The strength (including velocity, density and impedance jumps) and width of the 410-km and 660-km discontinuities are mainly controlled by the chemical composition and water content of the mantle transition zone. Some studies also detected 520-km and 560-km discontinuities within the mantle transition zone, which might be caused by the phase transition from wadsleyite to ringwoodite and the exsolution of calcium-perovskite from majorite, respectively. The seismically detected low-velocity zones above and below the mantle transition zone may be related to the dehydration melting caused by hydrated mantle transition zone material entering the low water-solubility upper and lower mantle. Although great progresses have been made, many important scientific questions related with the mantle transition zone remain unsolved. Accurate and reliable seismic imaging of the mantle transition zone provides crucial information for understanding these questions. Multidisciplinary studies integrating seismology, mineral physics, geodynamics and geochemistry are also needed. Finally, this paper discusses some future seismological research directions of the mantle transition zone.

     

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