差应力对橄榄石热物理性质影响的高温高压实验研究及其地学应用

Differential stress has a significant influence on the physicochemical properties of minerals and rocks. Differential stress can make the plastic deformation, lattice structure change, and lattice preferred orientation, which finally lead to anisotropy of physicochemical properties of minerals and rocks. At present, the thermal physical properties of known minerals and rocks are obtained under hydrostatic pressure. However, the thermodynamic and kinetic relations constructed under the condition of hydrostatic pressure are not satisfied with the existence of differential stress conditions. Consequently, the resulting understanding of the Earth's interior may have a greater deviation from the real Earth. Therefore, it is necessary to pay attention to and evaluate the effect of differential stress on the physicochemical properties of minerals and rocks in the Earth's interior..In this project, single crystal and polycrystalline olivine will be taken as the research object, we will focus on the basic scientific problems and the inherent mechanism of the effect of differential stress on the thermophysical properties of olivine. We will try to establish an excellent experimental method in Institute of Geochemistry, CAS, to in-situ measure thermal diffusivity and thermal conductivity under high temperature, high pressure and the differential stress by employing the high-pressure apparatus (Kawai-1000t multi-anvil、D-DIA-type press、STR、etc). Subsequently, by comparing with hydrostatic pressure results, we will systematically investigate the effect of differential stress on the thermal physical properties of olivine, and construct the constitutive relationships among the thermal conductivity, thermal diffusivity, temperature, pressure, differential stress, strain rates and so on. Furthermore, the effect of olivine fabric change on the anisotropy of thermal conductivity caused by differential stress and the micro physical mechanism will be explored in detail. After this project being finished, it is expected to provide a scientific basis for the thermal structure of the upper mantle and the temperature distribution of the lithosphere.

差应力对矿物岩石的物理化学性质有重要影响，它能够使材料发生塑性变形和晶格结构变化，引起晶格定向排列并最终导致其物理化学性质的各向异性。目前已知矿物岩石热物理性质都是在流体静压力下获得的，而静压条件下建立的热力学和动力学关系不满足存在差应力条件，由此获得的关于地球内部的各种认识可能与真实地球存在较大偏差，因此有必要重视并评估差应力对地球内部矿物岩石物理化学性质的影响。.本项目将以单晶和多晶橄榄石为研究对象，重点研究差应力对橄榄石热物理性质影响的基础科学问题和内在机制；拟在Kawai-1000t、D-DIA、STR流变仪等平台上开发一套能够在高温、高压、差应力下原位测量热物理性质的新方法；对比静压结果建立热导率与温度、压力、差应力、应变率等因素之间的本构方程；探索差应力导致的橄榄石组构变化对热导率各向异性的影响规律和微观物理机理；有望对上地幔热结构、岩石圈温度分布等重要科学问题提供科学依据。

矿物岩石在高温高压下的热物理性质（主要是热导率和热扩散系数）是认识和了解地球内部热结构、动力学过程、地球热演化历史最重要的物理参数，但是热导率和热扩散系数受到温度、压力、水含量、差应力等多种因素的影响。本项目以高温高压实验研究为主，着重考察（1）静压力下温度、压力、水含量对橄榄石热导率和热扩散系数的影响；（2）剪切变形下差应力对橄榄石热物理性质的影响；（3）岩石圈和上地幔的热结构及其演化。通过本项目的顺利实施，取得以下主要成果：（1）开发出地幔物质的热导率和热扩散系数的原位高温高压实验测量新方法；（2）查明了水对橄榄石的热导率和热扩散系数的影响，建立了热导率和热扩散系数与温度、压力、水含量等影响因素之间的本构方程，并阐明了热传导的微观机制；（3）揭示了中下地壳和岩石圈的热结构与热状态，为上地幔地球物理学观测异常的合理解释提供了重要科学依据。本项目已发表学术论文9篇，其中SCI论文8篇，已投稿在审论文2篇，待撰写论文2-4篇。