地球D"层中MgSiO₃后钙钛矿相的理论与实验证据。

Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D" layer.

作者信息

Oganov Artem R, Ono Shigeaki

机构信息

Laboratory of Crystallography, Department of Materials, ETH Zurich, Wolfgang Pauli Strasse 10, CH-8093 Zurich, Switzerland.

出版信息

Nature. 2004 Jul 22;430(6998):445-8. doi: 10.1038/nature02701.

DOI:10.1038/nature02701

PMID:15269766

Abstract

The Earth's lower mantle is believed to be composed mainly of (Mg,Fe)SiO3 perovskite, with lesser amounts of (Mg,Fe)O and CaSiO3 (ref. 1). But it has not been possible to explain many unusual properties of the lowermost approximately 150 km of the mantle (the D" layer) with this mineralogy. Here, using ab initio simulations and high-pressure experiments, we show that at pressures and temperatures of the D" layer, MgSiO3 transforms from perovskite into a layered CaIrO3-type post-perovskite phase. The elastic properties of the post-perovskite phase and its stability field explain several observed puzzling properties of the D" layer: its seismic anisotropy, the strongly undulating shear-wave discontinuity at its top and possibly the anticorrelation between shear and bulk sound velocities.

摘要

地球下地幔据信主要由（镁，铁）硅酸钙钛矿组成，还有少量的（镁，铁）氧化物和硅酸钙（参考文献1）。但用这种矿物学无法解释下地幔最底部约150公里区域（D"层）的许多异常特性。在此，我们通过从头算模拟和高压实验表明，在D"层的压力和温度条件下，硅酸镁从钙钛矿转变为层状的钙铱矿型后钙钛矿相。后钙钛矿相的弹性特性及其稳定场解释了D"层观测到的几个令人困惑的特性：其地震各向异性、其顶部强烈起伏的剪切波不连续面以及剪切波速与体波声速之间可能存在的反相关性。