globalchange  > 气候减缓与适应
DOI: 10.1038/ngeo2898
论文题名:
Persistence of strong silica-enriched domains in the Earth's lower mantle
作者: Ballmer M.D.; Houser C.; Hernlund J.W.; Wentzcovitch R.M.; Hirose K.
刊名: Nature Geoscience
ISSN: 17520894
出版年: 2017
卷: 10, 期:3
起始页码: 236
结束页码: 240
语种: 英语
Scopus关键词: chondrite ; geophysical method ; heterogeneity ; inorganic compound ; lower mantle ; magnesium ; mantle chemistry ; mantle convection ; mantle upwelling ; mixing ; model test ; persistence ; pyrolite ; silica ; viscosity
英文摘要: The composition of the lower mantle-comprising 56% of Earth's volume-remains poorly constrained. Among the major elements, Mg/Si ratios ranging from â 1/40.9-1.1, such as in rocky Solar-System building blocks (or chondrites), to â 1/41.2-1.3, such as in upper-mantle rocks (or pyrolite), have been proposed. Geophysical evidence for subducted lithosphere deep in the mantle has been interpreted in terms of efficient mixing, and thus homogenous Mg/Si across most of the mantle. However, previous models did not consider the effects of variable Mg/Si on the viscosity and mixing efficiency of lower-mantle rocks. Here, we use geodynamic models to show that large-scale heterogeneity associated with a 20-fold change in viscosity, such as due to the dominance of intrinsically strong (Mg, Fe)SiO 3-bridgmanite in low-Mg/Si domains, is sufficient to prevent efficient mantle mixing, even on large scales. Models predict that intrinsically strong domains stabilize mantle convection patterns, and coherently persist at depths of about 1,000-2,200 km up to the present-day, separated by relatively narrow up-/downwelling conduits of pyrolitic material. The stable manifestation of such bridgmanite-enriched ancient mantle structures (BEAMS) may reconcile the geographical fixity of deep-rooted mantle upwelling centres, and geophysical changes in seismic-Tomography patterns, radial viscosity, rising plumes and sinking slabs near 1,000 km depth. Moreover, these ancient structures may provide a reservoir to host primordial geochemical signatures.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/105831
Appears in Collections:气候减缓与适应
科学计划与规划

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作者单位: Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo, Japan; Institute of Geophysics, ETH Zurich, Zurich, Switzerland; Department of Applied Physics and Applied Mathematics, Columbia University, New York City, NY, United States; Department of Earth and Environmental Sciences, Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY, United States

Recommended Citation:
Ballmer M.D.,Houser C.,Hernlund J.W.,et al. Persistence of strong silica-enriched domains in the Earth's lower mantle[J]. Nature Geoscience,2017-01-01,10(3)
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