How lowermost mantle viscosity controls the chemical structure of Earth’s deep interior
How lowermost mantle viscosity controls the chemical structure of Earth’s deep interior
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DOI：
10.1038/s43247-023-01153-1
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发表时间：
2023-12
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影响因子：
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通讯作者：
J. Dannberg;K. Chotalia;Rene Gassmöller
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作者：
J. Dannberg;K. Chotalia;Rene Gassmöller
确定俯冲洋壳的命运对于理解地球深层内部的物质循环和地幔非均质性的来源至关重要。在长时间尺度上，控制俯冲板块分布的一个关键因素是最下层地幔的钙钛矿-后钙钛矿相变，这种相变被认为会导致流变减弱。利用高分辨率的计算模型，我们表明在核幔边界普遍存在的弱后钙钛矿可以促进或阻止玄武岩海洋地壳的积累，这取决于减弱的程度和地壳厚度。中等弱的后钙钛矿（~ 10 - 100倍弱）有利于地壳与俯冲板块的分离，增加玄武岩密集堆积。相反，非常弱的后钙钛矿（弱100倍以上）促进有力的羽流，携带更多的地壳物质，减少玄武岩的积累。我们的研究结果调和了先前研究的矛盾结论，并对整个地球历史上最下层地幔中俯冲地壳的积累提供了见解。
Determining the fate of subducted oceanic crust is critical for understanding material cycling through Earth’s deep interior and sources of mantle heterogeneity. A key control on the distribution of subducted slabs over long timescales is the bridgmanite to post-perovskite phase transition in the lowermost mantle, thought to cause rheological weakening. Using high-resolution computational models, we show that the ubiquitous presence of weak post-perovskite at the core-mantle boundary can facilitate or prevent the accumulation of basaltic oceanic crust, depending on the amount of weakening and the crustal thickness. Moderately weak post-perovskite ( ~ 10–100× weaker) facilitates segregation of crust from subducted slabs, increasing basalt accumulation in dense piles. Conversely, very weak post-perovskite (more than 100× weaker) promotes vigorous plumes that entrain more crustal material, decreasing basalt accumulation. Our results reconcile the contradicting conclusions of previous studies and provide insights into the accumulation of subducted crust in the lowermost mantle throughout Earth’s history.