高温高围压下石英的相变与热物理性质对差应力的响应机制研究

Differential stress widely exists in the interior of the earth. Differential stress has an important contribution to the free energy of matter. Free energy is the decisive factor controlling the composition, structure, properties and interaction process of matter system. Therefore, differential stress, like temperature and hydrostatic pressure, is the most basic thermodynamic variable that constrains the material system within the Earth. Quartz is one of the most important crustal rock-forming minerals, forming different mineral facies under different temperature and pressure conditions. The study of the α-β phase transition and thermodynamic properties of quartz under high temperature and high confining pressure on differential stress response is still blank. Raman spectra of minerals can reflect some lattice vibration characteristics of crystals, and lattice vibration is the physical essence of mineral thermophysical properties. Based on lattice vibration theory and various statistical thermodynamic theoretical models, this project intends to adopt self-developed high temperature and high confining pressure differential stress experimental device combined with in-situ measurement system of focused micro-Raman spectroscopy, and the corresponding temperature, pressure and differential stress conditions in shallow crust. The in situ measurement of Raman spectra of quartz was carried out to study the response mechanism of quartz alpha-beta phase transition process and thermodynamic properties to differential stress. It fills in the blank of the research on the response of mineral phase transformation and thermophysical properties to differential stress under high temperature and high pressure, and provides important experimental basis for understanding the characteristics and evolution process of crustal materials.

地球内部广泛存在差应力，差应力对物质的自由能具有重要贡献，而自由能是控制物质体系组成、结构、构造、性状及相互作用过程的决定性因素。因此，差应力和温度及静水压力一样，都是约束地球内部物质体系最基本的热力学变量。石英是最重要的地壳造岩矿物之一，在不同温压条件下形成不同矿物相。高温高围压下石英的α-β相变和热物理性质对差应力响应研究尚属空白。矿物的拉曼光谱能反映晶体的一部分晶格振动特性，而晶格振动是矿物热物理性质的物理本质。本项目以晶格振动理论和多种统计热力学理论模型为基础，拟采用自主研发的高温高围压差应力实验装置和同聚焦显微拉曼光谱原位测量系统相结合，在地壳浅部对应的温度、压力、差应力条件下，进行石英拉曼光谱的原位测量，对石英α-β相变过程及热物理性质对差应力的响应机制进行研究。填补高温高压下矿物相变和热物理性质对差应力响应机制方面的空白，并为了解地壳物质特征及演化过程提供重要的实验依据。

地球内部广泛存在差应力，差应力对物质的自由能具有重要贡献，而自由能是控制物质体系组成、结构、构造、性状及相互作用过程的决定性因素。因此，差应力和温度及静水压力一样，都是约束地球内部物质体系最基本的热力学变量。石英是最重要的地壳造岩矿物之一，在不同温压条件下形成不同矿物相。高温高围压下石英的α-β相变和热力学性质对差应力响应研究尚属空白。矿物的拉曼散射源于晶格振动，晶格振动是矿物热学性质的物理本质，本项目以晶格振动理论和多种统计热力学理论模型为基础，本项目采用自主研发的高温高围压差应力实验装置和同聚焦显微拉曼光谱原位测量系统相结合，在地壳浅部对应的温度、压力、差应力条件下，原位测量石英的显微拉曼光谱，得到不同温度、围压、差应力条件下石英的拉曼光谱及其与温度、围压、差应力的关系。.主要数据结论如下：.① 在温度 20-500°C、围压压力 0.1-35 MPa 和差应力 0.1-550 MPa 下，温度、围压压力、差应力在实验条件范围内对石英的 464 cm-1峰的频移相互影响的关系不大。.② 在围压10-35 MPa、温度200°C、差应力0.1-550 MPa的范围内，差应力与围压压力对石英的464 cm-1峰的频移影响的关系较小。.③ 464 cm-1峰在20-500°C及恒差应力条件下，随温度的变化率(δνi/δT)S 为-1.2 cm-1/100°C，与前人利用金刚石压腔研究的结果基本一致，可证明该实验方法是有效的，实验结果是可靠的。进一步得出在恒温条件下，随差应力的变化率(δνi/δS)T 为3 cm-1/GPa。.④ 在常压、温度20-500°C、差应力0.1-550 MPa的范围内，沿石英样品的不同轴向加载差应力，石英的464 cm-1的频移对温度的响应几乎没有变化，而垂直于石英样品的C轴方向加载差应力所得的随差应力的恒温变化率(δνi/δS)T是沿石英样品的C轴方向加载差应力的两倍。.该工作填补高温高围压同时差应力条件下矿物的原位拉曼光谱测量工作的空白，为进一步了解地壳物质特征及演化过程提供重要的实验依据。.