Evidence for Fe-Si-O liquid immiscibility at deep Earth pressures
Evidence for Fe-Si-O liquid immiscibility at deep Earth pressures
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DOI：
10.1073/pnas.1821712116
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发表时间：
2019-05-21
影响因子：
11.1
通讯作者：
Lee, Kanani K. M.
中科院分区：
文献类型：
--
作者：
Arveson, Sarah M.;Deng, Jie;Lee, Kanani K. M.
地震观测表明，地球液态外核的最上层区域是有浮力的，速度比大块的外核慢。形成稳定分层层的一种可能机制是熔融铁合金系统的不相容性，这一点尚未在堆芯压力下得到证实。通过激光加热金刚石压砧实验和第一性原理分子动力学模拟，我们发现液态Fe-Si和Fe-Si-O之间的不相容性至少持续到140 GPa。Fe-Si-O系统中的高压不稳定性可能解释了外核顶部的分层层，复杂的地球深部分化和演化，并影响地球磁场的结构和强度。我们的研究结果支持硅和氧作为共存的轻元素在核心，并建议SiO2不结晶出熔融的Fe-Si-O在核幔边界。
Seismic observations suggest that the uppermost region of Earth's liquid outer core is buoyant, with slower velocities than the bulk outer core. One possible mechanism for the formation of a stably stratified layer is immiscibility in molten iron alloy systems, which has yet to be demonstrated at core pressures. We find immiscibility between liquid Fe-Si and Fe-Si-O persisting to at least 140 GPa through a combination of laser-heated diamond-anvil cell experiments and first-principles molecular dynamics simulations. High-pressure immiscibility in the Fe-Si-O system may explain a stratified layer atop the outer core, complicate differentiation and evolution of the deep Earth, and affect the structure and intensity of Earth's magnetic field. Our results support silicon and oxygen as coexisting light elements in the core and suggest that SiO2 does not crystallize out of molten Fe-Si-O at the core-mantle boundary.