Phase E是地球深部的重要含水相之一，是俯冲板块将水带入地幔转换带的重要载体。前人研究表明，在水饱和MgO-SiO2体系中，Phase E只能在俯冲板块较低的地温梯度下稳定。在水饱和CaO-MgO-FeO-Al2O3-TiO2-SiO2体系中，含Fe, Al的Phase E则被发现可在正常地温梯度下稳定。然而在该体系中，Phase E稳定的最高温度和压力条件还没有得到实验研究的约束。本项目拟通过高温高压实验，研究Phase E在地幔转换带下部存在的可能性；拟通过X射线单晶衍射和高压拉曼光谱实验，研究Fe, Al对Phase E晶体结构和拉曼光谱特征的影响，并论证Fe, Al 在稳定Phase E晶体结构方面所发挥的作用。本项目的研究结果将对地幔转换带的矿物组成，以及水在地幔转换带的赋存形式提供新的认识。

Phase E is a significant hydrous phase in the Earth’s deep interior. As an important water carrier in subducting slabs, Phase E transports water to the mantle transition zone. According to previous studies, Phase E (Mg2.27Si1.26H2.4O6) can be observed in the system MgO-SiO2-H2O at subduction slab geotherms up to 1100゜C and 17 GPa. In CaO-MgO-FeO-Al2O3-TiO2-SiO2-H2O system, Phase E can be observed at average mantle geotherm or near average mantle geotherm (15.5 GPa, 1400゜C; 19 GPa, 1400゜C). However, the stability field of Phase E in this system is still unknown. To understand the stability of Phase E in the lower transition zone (20-22 GPa，1500-1550゜C), we plan to conduct synthetic experiments in CaO-MgO-FeO-Al2O3-TiO2-SiO2-H2O system. In addition, for Fe, Al-bearing Phase E, crystal structure parameters and Raman spectra collected with increasing pressures will be analyzed. The impacts of Fe and Al on stabilizing Phase E at mantle geotherm in the transition zone will be discussed based on the experimental results of X-ray diffraction and Raman spectroscopy. This project is expected to better our understanding on hydrated region of the mantle transition zone.