Measurements of thermophysical properties of deep Earth materials under high pressure and high temperature

在kawai型仪器中，采用一维热流脉冲加热方法，在压力高达8-10 GPa、温度高达1100 K的条件下，测量了主要地幔候选材料的热扩散率和热导率。结果表明，这些主要地幔矿物的热导率或热导率每1 GPa增加3- 4%，橄榄石在地幔中的稳定性可能保持各向异性，即直到410 km深度。石榴石表现出某种特殊的导热性或热扩散性：与其他致密氧化物和橄榄石相比，其加热降低和加压增加是适度的。另一种主要的地幔物质辉石表现出与橄榄石相似的导热性或扩散性。目前关于扩散系数的热导率的压力依赖性的结果与以前的实验和理论预测一致。当热扩散系数和热导率同时测量时，通过比较这些量可以得到热容。这项研究证明了矿物物理学的一个新方面：地幔物质在压力下的热容可以通过实验来确定。橄榄石和石榴石在室温下的热容与以前报道的值相差不到5%。此外，橄榄石的三个结晶方向的热容在6%以内是一致的，这表明本方法的热扩散率和导热率是适当的。在高压下，热容的值略低于零压时的值。这与热力学在压力下热容变化的特性是一致的。在未来的研究中，压力范围将超过15gpa，相当于上地幔底部的压力范围，并希望能够进行明显精度的测量，减少可能由机械缺陷或样品组合压缩变形引起的系统误差。少

Thermal diffusivity and thermal conductivity of major mantle candidate materials have been measured under pressures up to 8-10 GPa and temperatures to 1100 K, using a pulse-heating method of one-dimensional heat flow in a Kawai-type apparatus. The results show that the thermal conductivity or diffusivity of these major mantle minerals increases 3-4 % per 1 GPa, and that olivine likely preserves anisotropy in thermal diffusivity or conductivity throughout its stability in the mantle, i.e. down to 410 km depth. Garnet shows somewhat peculiar behavior of thermal conductivity or thermal diffusivity : their decrease by heating and increase by pressurizing are moderate compared to other dense oxides and olivine. Another major mantle material, pyroxene shows similar behavior of thermal conductivity or diffusivity to olivine. The present results of pressure dependence in thermal conductivity of diffusivity agree with previous experiments and theoretical predictions.As thermal diffusivity and t … More hermal conductivity are measured simultaneously, heat capacity is obtained by comparing these quantities. This study demonstrates a novel aspect of mineral physics : that the heat capacity of mantle materials under pressure could be determined experimentally. Heat capacities of olivine and garnet at room temperature are within 5 % of previously reported values. Moreover, the heat capacities for the three crystallographic directions in olivine are consistent within 6 %, which shows the adequacy of the present method for thermal diffusivity and conductivity. Under high pressures, heat capacities have slightly lower values to those at zero pressure. This is consistent with the identity of thermodynamics for changes in heat capacity under pressure.For future study, the pressure range will exceed 15 GPa, which is equivalent to those at the bottom of the upper mantle, and measurements of marked precision are hope to be performed with reduction of systematic errors probably derived from mechanical defect or deformation of the sample assembly by compression. Less