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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 >Segregation of core melts by permeable flow in the lower mantle
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Segregation of core melts by permeable flow in the lower mantle

机译：下地幔中的渗透流使岩心熔融物分离

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摘要

We measured the dihedral angle of molten iron in (Mg,Fe)SiO3-perovskite aggregate with increasing pressure and temperature using laser-heated diamond anvil cell. Results demonstrate that it decreases from 94° at ～27 GPa and ～2400 K to 51° at ～47 GPa and～3000 K. This value is smaller than the critical angle of 60°, thus allowing iron melt to wet the grain boundaries of silicate perovskite and develop an interconnected melt network within the perovskite-dominant matrix, even at very small melt fractions. The quenched liquid iron contained substantial amounts of oxygen and silicon as pressure and temperature increase. Such a decrease in the dihedral angle is likely due to a reduction in the iron-perovskite interfacial energy by dissolving oxygen and silicon into the liquid iron from coexisting silicate perovskite. These suggest that a wetting behaviour of core melts in the solid silicate mantle changes above ～40 GPa, corresponding to ～1000 km depth in the present Earth, and efficient metal segregation may have proceeded by permeable flow in a late stage of accretion. Oxygen and silicon incorporated during core formation and later by core–mantle boundary process may be important light elements in the Earth's core.
机译：我们使用激光加热的金刚石砧单元，随着压力和温度的升高，测量了（Mg，Fe）SiO3-钙钛矿聚集体中铁水的二面角。结果表明，它从〜27 GPa和〜2400 K时的94°减小到〜47 GPa和〜3000 K时的51°。该值小于60°的临界角，从而使铁水润湿了合金的晶界。硅酸盐钙钛矿，即使在很小的熔体含量下，也能在钙钛矿占主导的基体内形成相互连接的熔体网络。随着压力和温度的升高，淬火的液态铁含有大量的氧和硅。这种二面角的减小可能是由于通过将氧和硅从共存的硅酸盐钙钛矿溶解到液态铁中而降低了铁钙钛矿的界面能。这些表明，固体硅酸盐地幔中核熔融物的润湿行为在〜40 GPa以上变化，对应于目前地球上〜1000 km的深度，并且在积聚的后期阶段可能通过渗透流进行了有效的金属偏析。在岩心形成过程中以及随后通过岩心-地幔边界过程掺入的氧和硅可能是地球核心中的重要轻元素。

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