Abstract The new results of experimental study of the Na 2 MgSiO 4 –Mg 2 SiO 4 section of the SiO 2 –MgO–Na 2 O model system at 22–24 GPa and 1600–1900°C are discussed in this paper. An association of Na-bearing ringwoodite (up to 0.42 wt % Na 2 O) and the phase with the composition Na 2 MgSiO 4 with a cristobalite-type structure was obtained at 22 GPa. Incorporation of Na in ringwoodite occurs through the mechanism Mg 2+ → 2/3Na + + 1/3Si 4+ and results in an increase in the cell parameter in relation to that of pure Mg 2 SiO 4 ringwoodite. A paragenesis of Na-bearing bridgmanite (up to 0.67 wt % Na 2 O), periclase, and anhydrous sodium phase X (Na 2 Mg 2 Si 2 O 7 ) is formed at 23–24 GPa. Based on the data obtained, high-pressure Na–Mg silicates, Na 2 MgSiO 4 and Na 2 Mg 2 Si 2 O 7 , may be considered as mineralogically probable mantle phases within the locally metasomatized mantle regions, although their finds as inclusions in diamond crystals are unlikely.

中文翻译：

---

过渡带和下地幔边界处的硅酸钠：成分和结构模式

摘要 本文讨论了SiO 2 -MgO-Na 2 O 模型体系的Na 2 MgSiO 4 -Mg 2 SiO 4 截面在22-24 GPa 和1600-1900°C 条件下的新实验研究结果。在 22 GPa 下获得了含 Na 菱镁矿（高达 0.42 重量% Na 2 O）和组成为 Na 2 MgSiO 4 且具有方石英型结构的相的组合。Na 在菱镁矿中的掺入通过 Mg 2+ → 2/3Na + + 1/3Si 4+ 机制发生，并导致与纯 Mg 2 SiO 4 菱镁矿相比电池参数增加。在 23-24 GPa 下形成含钠桥锰矿（高达 0.67 wt% Na 2 O）、方镁石和无水钠相 X（Na 2 Mg 2 Si 2 O 7 ）的共生作用。根据获得的数据，高压 Na-Mg 硅酸盐 Na 2 MgSiO 4 和 Na 2 Mg 2 Si 2 O 7 ，