铝硅酸盐钙钛矿的晶格参数

 本文根据MgSiO₃－CaSiO₃－Al₂O₃系统在高温超高压下（p>40 GPa，T~1 500 ℃）合成铝硅酸盐钙钛矿的实验结果，并通过(Mg,Al)(Si,Al)O₃钙钛矿和(Mg,Fe)SiO₃钙钛矿的对比，研究组分对钙钛矿的晶格常数、畸变和稳定性的影响。查明在650 km的地震波速度不连续面以下的地幔中，Al₂O₃和CaO的存在形式。

LATTICE PARAMETERS OF THE PEROVSKITE IN ALUMINUM-BEARING SILICATES

In the present paper, the sysem FeO-MgO-Al₂O₃-CaO-SiO₂ has been studied in an attempt to determine the effects of aluminum and calcium on the stability of the silicate perovskite. A series of synthesized silicate glasses were converted to silicate-perovskites in a diamond cell at approximately 40 GPa and 1 500 ℃. Powder X-ray diffraction analyses of these quenched samples showed that at least 25 mol% Al₂O₃ was dissolved in perovskite forming (Mg,Al)(Si,Al)O₃. The increase in volume of the perovskite phase was regarded as a function of increasing Al₂O₃ content. The addition of Al₂O₃ caused a significant increase in the molar volume of MgSiO₃-Pv than FeSiO₃. Because of the large volume diference between garnet and perovskite, there would be no stadility field for garnet in the lower mantle at depths greater than the 650 km seismic discontinuity. In th study of the compositions En₈₀Wo₁₈Co₂ and En₇₃Wo₂₄Co₃ at 40 GPa, the run products yielded X-ray diffraction patterns almost identical with those of calcium-free perovskites. The calcium would probably form a Ca-rich Al-bearing silicate perovskites at high pressure and high temperature, but it could not be quenched.