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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Contrasting opacity of bridgmanite and ferropericlase in the lowermost mantle: Implications to radiative and electrical conductivity
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Contrasting opacity of bridgmanite and ferropericlase in the lowermost mantle: Implications to radiative and electrical conductivity

机译：Bridgmanite和铁铁酶在最低地幔中的对比度：对辐射和电导率的影响

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摘要

Earth's lowermost mantle displays complex geological phenomena that likely result from its heterogeneous physical interaction with the core. Geophysical models of core-mantle interaction rely on the thermal and electrical conductivities of appropriate geomaterials which, however, have never been probed at representative pressure and temperature (P-T) conditions. Here we report on the opacity of single crystalline bridgmanite and ferropericlase and link it to their radiative and electrical conductivities. Our results show that light absorption in the visible spectral range is enhanced upon heating in both minerals but the rate of change in opacity with temperature is a factor of six higher in ferropericlase. As a result, bridgmanite in the lowermost mantle is moderately transparent while ferropericlase is highly opaque. Our measurements support previous indirect estimates of low (< 1 W/m/K) and largely temperature-independent radiative conductivity in the lowermost mantle. This implies that the radiative mechanism has not contributed significantly to cooling the Earth's core throughout the geologic time. Opaque ferropericlase is electrically conducting and mediates strong core-mantle electromagnetic coupling, explaining the intradecadal oscillations in the length of day, low secular geomagnetic variations in Central Pacific, and the preferred paths of geomagnetic pole reversals. (C) 2021 Elsevier B.V. All rights reserved.
机译：地球最下面的地幔显示出复杂的地质现象，这可能是由于其与地核的非均匀物理相互作用造成的。核幔相互作用的地球物理模型依赖于适当地质材料的热导率和导电率，然而，从未在代表性压力和温度（P-T）条件下进行过探测。在这里，我们报告了单晶硼镁石和铁方镁石的不透明性，并将其与它们的辐射和导电性联系起来。我们的结果表明，两种矿物在加热后可见光谱范围内的光吸收都会增强，但在铁方镁石中，不透明度随温度的变化率要高出六倍。因此，最下部地幔中的硼镁石呈中等透明度，而铁橄榄岩呈高度不透明。我们的测量结果支持之前对最低地幔的低（<1 W/m/K）和基本上与温度无关的辐射电导率的间接估计。这意味着在整个地质时期，辐射机制并没有对地核的冷却做出显著贡献。不透明的铁橄榄石具有导电性，介导了强烈的核幔电磁耦合，解释了日长的年代内振荡、太平洋中部长期地磁变化较低，以及地磁磁极反转的首选路径。（c）2021爱思唯尔B.V.保留所有权利。

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