Thermal conductivity of earth materials under high temperature and high pressure

点击翻译按钮获取中文摘要

To investigate the thermal state of the earth's mantle, the author intends to measure thermal conductivies of mantle candidate minerals under high pressures and high temperatures.A transient method of one dimension heat flow is applied to the thermal conductivity measurement under high pressure. A thin metallic plane heater is inserted between disks of sample. Cuts are made on the heater in order to enhance electric resistance for a sufficient power generated and to ensure uniform heating on the sample. A pulse current is supplied to the heater and temperature profile is detected on the far side of the sample by a thermocouple. Thermal conductivity is calculated from the decay of temperature, the electric power and the positions of the heater and the thermocouple. Measurements are made in a tetrahedral-anvil high-pressure appratus. Conditions of the measurements at the first step are : pressure of 10 GPa and temperature of 1500ﾟC.The materials or minerals to be investigated are alpha-, beta- and gamma- (Mg, Fe) _2SiO_4, (olivine, modified spinel and spinel), (Mg, Fe) SiO_3 (ortho and clino pyroxene), (Mg, Fe) _3Al_2Si_3O_<12>- (Mg, Fe) _4Si_4O_<12> solid solution and (Mg, Fe) SiO_3 perovskite. Other minor components of the mantle materials, such as stishovite are to be also investigated if necessary. Sintered samples of these materials should be prepared for the thermal conductivity measurement. Hot pressing is taken place in a NaCl capsule in order to obtain pore-free no-cracking samples.The experiments are continuing at present. Measurements on fused quartz show that this method can be used for the thermal conductivity of the small samples. Results of the thermal conductivity/diffusivity measurement for mantle materials under pressure will be made in the near future.