高温高压条件下绿辉石热弹性性质研究

Omphacite is an important mineral in kimberlite and diamond xenoliths and (ultra) high pressure metamorphic rocks. A lot of studies have revealed that the Di-Jd binary omphacite from kimberlite and diamond xenoliths and (ultra) high pressure metamorphic rocks are in the minority, the majority of them are Quad-Jd-Ae ternary omphacite. However, up to date, there is no a systematic study about the PVT equation of state of Quad-Jd-Ae ternary omphacite. Large deviations will be caused by using the thermoelastic properties of Di-Jd binary omphacites only to discuss the properties of the eclogite, which will result in misunderstanding the geodynamic processes of plate subduction and delamination. In this project, the PVT equation of state of Quad-Jd-Ae ternary omphacites which have different components will be investigated at high temperature and high pressure, and the high precision thermoelastic parameter will be obtained, by using diamond anvil cell and synchrotron radiation single crystal X-ray diffraction. The effect of composition change on the thermoelastic parameters of Quad-Jd-Ae ternary omphacites will be discussed, and then the quantitative density and thermoelasticity model of the eclogite shall be established. Finally, we will provide some key data to more accurately understand the thermoelastic behavior of eclogite, which will give the basis for further understanding the geodynamical processes of the plate subduction and delamination.

绿辉石是金伯利岩和金刚石矿物包体及（超）高压变质岩中的重要组成矿物。大量研究表明，天然产出的绿辉石中透辉石(Di)-硬玉(Jd)二端元绿辉石只占少数，更多的是钙镁铁质辉石(Quad)-硬玉(Jd)-霓石(Ae)三端元绿辉石，但未有关于Quad-Jd-Ae三端元绿辉石PVT状态方程的系统研究报道。若仅以Di-Jd二端元绿辉石的热弹性性质来约束榴辉岩密度和热弹性性质与地质实际不符，并进一步影响对板块俯冲和拆沉作用动力学过程的正确认识。本项目拟利用同步辐射单晶X射线衍射结合金刚石压腔实验技术，在高温高压条件下对不同组分的Quad-Jd-Ae三端元绿辉石进行PVT状态方程研究，获取高精度的热弹性参数值，讨论组分变化对Quad-Jd-Ae三端元绿辉石热弹性参数值的影响，进而获得榴辉岩的定量密度和热弹性性质模型，为更精确地认识深部俯冲板片的热弹性行为及板块俯冲和拆沉作用动力学过程提供关键的实验依据。

本项目以天然绿辉石矿物为主要矿物样品，并结合部分人工合成斜方辉石样品，利用金刚石压腔外加温和同步辐射 X 射线衍射技术，在高温高压条件下，对三端元绿辉石样品进行 PVT状态方程研究。结合前人研究成果，探讨含水以及组分变化对三端元绿辉石矿物热弹性参数值的影响。项目执行期间，进行了数十次的高温高压同步辐射X射线衍射实验，获得了不同含水量及不同组分三端元绿辉石和斜方辉石矿物的热弹性参数值，有效确定了含水和组分变化对单斜辉石和斜方辉石矿物的稳定性及热弹性性质的影响。进而获得了榴辉岩的定量密度和热弹性性质模型，为更准确地认识上地幔及俯冲带的热弹性行为和动力学过程提供关键的实验约束。受本项目支持，已经发表学术论文22篇，其中SCI论文21篇，EI论文1篇。项目执行期间，共培养出站博士后1名，博士生3名（获国家研究生奖学金2人次，中国科学院院长优秀奖1人次，中国科学院优秀博士论文奖1人次）。