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A numerical study of thermal and chemical structures at the core-mantle boundary
Earth and Planetary Science Letters ( IF 5.3 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.epsl.2020.116498
Claudia Stein , Mariano Mertens , Ulrich Hansen

Abstract The core-mantle boundary (CMB) represents the lower boundary layer of the actively convecting Earth's mantle and is structurally very complex. Thermal and chemical structures such as thermal plumes and thermochemical piles have been considered to explain the complexities. Both affect the dynamics of the Earth's mantle and its temporal evolution. But also the surface plates are an essential aspect of mantle convection that strongly influence the dynamics of the interior. We use numerical thermochemical models of mantle convection to study the structure and dynamics of the lowermost mantle. Our approach allows for the investigation of plumes and piles in combination with plate-like surface motion and deep subduction. The models show that the presence of a dense CMB layer generally reduces the mobility of the surface plates but that during plate evolution a variety of plume classes occur leaving a complex structure at the CMB. The CMB topography shows large elevated areas with sharp edges and a flat or slightly dented top for piles with plumes atop. Also, plume clusters can cause large elevated areas with sharp edges but a flat top with a few smaller peaks. Smaller-scale patterns, often close to the edges of the large structures cause smaller peaks in CMB topography and can be explained by either line-plumes or wind-driven thermals. The latter often arise when heat is trapped beneath subducted slabs that spread over the CMB.

中文翻译:

核-幔边界处热结构和化学结构的数值研究

摘要 核-地幔边界(CMB)代表地幔活跃对流的下边界层,结构非常复杂。热和化学结构,例如热羽流和热化学桩,已被认为可以解释这种复杂性。两者都会影响地幔的动力学及其时间演化。但表面板块也是地幔对流的一个重要方面,它强烈影响内部的动力学。我们使用地幔对流的数值热化学模型来研究最下地幔的结构和动力学。我们的方法允许结合板状表面运动和深俯冲来研究羽流和桩。模型表明,密集的 CMB 层的存在通常会降低表面板块的流动性,但在板块演化过程中,会出现各种类型的羽流,在 CMB 留下复杂的结构。CMB 地形显示大面积升高区域,边缘锋利,顶部平坦或略微凹陷,用于顶部有羽状物的桩。此外,羽流簇会导致大面积升高,边缘锋利,但顶部平坦,有几个较小的峰。较小尺度的模式,通常靠近大型结构的边缘,导致 CMB 地形中的峰值较小,可以用线羽或风驱动的热气流来解释。当热量被困在遍布 CMB 的俯冲板块下方时,后者通常会出现。CMB 地形显示大面积升高区域,边缘锋利,顶部平坦或略微凹陷,用于顶部有羽状物的桩。此外,羽流簇会导致大面积升高,边缘锋利,但顶部平坦,有几个较小的峰。较小尺度的模式,通常靠近大型结构的边缘,导致 CMB 地形中的峰值较小,可以用线羽或风驱动的热气流来解释。当热量被困在遍布 CMB 的俯冲板块下方时,后者通常会出现。CMB 地形显示大面积升高区域,边缘锋利,顶部平坦或略微凹陷,用于顶部有羽状物的桩。此外,羽流簇会导致大面积升高,边缘锋利,但顶部平坦,有几个较小的峰。较小尺度的模式,通常靠近大型结构的边缘,导致 CMB 地形中的峰值较小,可以用线羽或风驱动的热气流来解释。当热量被困在遍布 CMB 的俯冲板块下方时,后者通常会出现。通常靠近大型结构的边缘会导致 CMB 地形中的较小峰值,并且可以用线羽或风驱动的热气流来解释。当热量被困在遍布 CMB 的俯冲板块下方时,后者通常会出现。通常靠近大型结构的边缘会导致 CMB 地形中的较小峰值,并且可以用线羽或风驱动的热气流来解释。当热量被困在遍布 CMB 的俯冲板块下方时,后者通常会出现。
更新日期:2020-10-01
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