惑星深部物質の熱伝導率に対する水と化学不純物の影響：地球型惑星の熱進化の探求

地核地幔边界热通量控制着观测到的地系行星磁场、地质活动和热结构的产生，而地核地幔边界热通量受最下层地幔矿物的热性质支配。本研究旨在了解矿物中杂质对类地行星热演化的影响，实现以下项目：(1)测定含（Fe, Al）菱辉石导热系数的压力依赖性和温度依赖性；(2)脉冲加热法测定无水和含水菱辉石导热系数的压力依赖性和温度依赖性。在本会计年度，我们分析了项目(1)在上一会计年度获得的实验数据。桥辉石的压力依赖性和导热系数绝对值的显著降低表明岩浆海洋凝固后，地幔在长期冷却过程中由于杂质的参与，冷却速率逐渐减慢。我们还大力推行项目(2)。得到了具有理想成分和水含量的环伍德石样品的合成条件。然而，我们发现菱辉石非常脆，在切成薄片的过程中，它很容易碎成碎片。经过多次努力，我们决定减小样品直径以获得较薄的环伍德石薄片。一种新的高压热导率测量电池已经开发出来。目前正在进行环woodite热导率的测量。

Core mantle boundary heat flux, which is governed by the thermal properties of the lowermost mantle minerals, controls the generation of observed magnetic field, geological activity and thermal structure of the terrestrial planets. The purpose of this study is to understand how impurities in minerals affect the thermal evolution of terrestrial planets and to achieve the following projects: (1) Determination of pressure dependence and temperature dependence of thermal conductivity of (Fe, Al)-bearing bridgmanite (2) Determination of pressure dependence and temperature dependence of thermal conductivity of anhydrous and hydrous ringwoodite by pulse heating method.In this fiscal year, we analyzed experimental data of project (1) obtained in the previous fiscal year. The significant decrease of pressure dependence and the absolute value of thermal conductivity of bridgmanite indicates a gradual slowing of the cooling rate of the mantle due to impurities' involvement during the secular cooling after the magma ocean solidification. We have also vigorously pursued project (2). The synthesis conditions of ringwoodite samples with desired compositions and water content have been well mastered. However, we found ringwoodite is very brittle, during cutting into thin slices, it easily breaks into pieces. After many struggles, we decide to decrease the sample diameter to get thin slices of ringwoodite. A new high-pressure thermal conductivity measurement cell for such smaller samples has been developed. The measurements of thermal conductivity of ringwoodite are now undergoing.