电气石较常见于（超）高压变质岩中，是（超）高压变质岩俯冲-折返过程的指示矿物，记录了俯冲带地壳物质循环过程。电气石的热稳定性决定其能否在（超）高压变质岩中出现；另一方面，电气石PVT状态方程是了解高温高压下电气石所含元素行为和稳定性的晶体物理学基础。目前电气石PVT状态方程的研究极度缺乏，特别是相当于冷俯冲温压条件下的热稳定性仍为空白，严重制约了对冷俯冲带地壳物质循环过程的正确理解。为此，本项目拟利用大压机在冷俯冲温压条件下研究上地壳成分+硼+水体系中电气石的热稳定性,并利用同步辐射单晶X射线衍射结合金刚石压腔外加温实验技术，研究不同成分电气石的PVT状态方程和热稳定性。获得冷俯冲条件下不同成分电气石的热稳定性、晶体结构和热弹性参数，讨论电气石成分变化对电气石上述性质的影响，确定冷俯冲条件下地壳物质的俯冲深度，约束冷俯冲过程中地壳-地幔物质交换作用和地壳物质循环过程。

Tourmaline, an indicator mineral for subduction and exhumation of (ultra)high pressure metamorphic rocks, is widely found in (ultra)high pressure metamorphic rocks. It is well known as a recorder of the circulation of crustal materials in subduction zone. The thermal stability of tourmaline is the key factor to determine whether tourmaline can appear in (ultra)high pressure metamorphic rocks. However, the thermal stability of tourmaline at high temperature and pressure, especially at the temperature and pressure in cold subduction zone, is not well constrained. On the other hand, PVT equation of state of tourmaline is the basis of crystal physics to understand the stability and chemical element behavior of tourmaline under high temperature and pressure. However, there is only one report on PVT equation of state of tourmaline. Therefore, the lack of study on the thermal stability and PVT equation of state of tourmaline hinders the accurate understanding of the circulation of crustal materials in the cold subduction zone. In this project, the thermal stability of tourmaline in the continental upper crust composition + H3BO3 + H2O system will be investigated under the condition equivalent to cold subduction zone temperature and pressure (5.0-10.0 GPa, 450-800℃) using Kawai-1000t multi-anvil apparatus. The PVT equation of state of tourmaline with different compositions will be studied by means of resistance heating diamond anvil cell and synchrotron radiation single crystal X-ray diffraction up to 15 GPa and 600℃. The thermal stability, crystal structure and thermoelastic parameters of tourmaline under the condition of cold subduction zone will be obtained, and the influence of compositional variability on the thermal stability, crystal structure and thermoelastic parameters of tourmaline will be discussed. The subduction depth of crust in cold subduction zone will be determined. In a word, this study will provide the key experiment for further using tourmaline to constrain the circulation of crust material and the exchange of crust and mantle material in the process of cold subduction.