洋壳俯冲带高压-超高压岩石的折返问题，一直存在争议。作为浮力折返机制之一的蛇纹岩在俯冲隧道中所起的作用值得深入研究。在前期研究的基础上，本项目拟进一步对西南天山超高压变质蛇纹岩和其中包裹的榴辉岩进行系统的岩石学、元素和同位素地球化学、地质年代学和高压实验的综合研究。通过矿物结构和成分分析，结合相平衡模拟计算以及锆石年代学的研究，确定包裹的榴辉岩的峰期变质条件、变质P-T轨迹和变质时代；通过3.65Å相高压实验研究，探讨其温压稳定范围，确定天山超高压蛇纹岩的折返深度。从而判断榴辉岩与蛇纹岩是一起经历深俯冲并折返，还是超深蛇纹岩在折返过程中捕获榴辉岩然后携带折返？此外通过研究蛇纹岩中各类脉体的变质过程，探索蛇纹岩变质过程中的流体行为以及这些流体对榴辉岩折返过程的影响。

The exhumation mechanism of high-ultrahigh pressure rocks from oceanic subduction zone has been extensively debated. As one of the buoyant host rock that facilitating the exhumation of eclogites, the key role of serpentinites in the subduction channel need more further studies. This project will conduct systematic petrological, geochemical, geochronological and high-pressure experimental studies of serpentinites and enclosed eclogites from the HP-UHP metamorphic belt of southwestern Tianshan. Detailed petrological and geochronological studies combined with phase equilibrium simulation calculation of the enclosed eclogites will help us to infer their peak metamorphic conditions, P-T paths and metamorphic ages. High-pressure experiments will be carried out to determine the stability of 3.65Å phase and related phase transformation, and derive an estimation of the subduction depth for Tianshan serpentinites. On the basis of these studies, to determine whether the eclogites and serpentinites subducted deeply together, or the eclogites were captured by serpentinites during its exhumation and then exhumated together to the earth’s surface. On the other side, the metamorphism of many kinds of veins appeared in serpentinites is also studied, in order to discuss the fluid process after dehydration of serpentinites and the effects to the exhumation of eclogites made by the fluid.