题目：Lattice thermal conductivity of dry ringwoodite: implications for mantle dynamics and thermal evolution of stagnant slabs

报告人：张友悦 助理教授 日本爱媛大学

报告时间：2026年2月5日上午10:00

报告地点：超硬实验综合楼5楼A514会议室

报告摘要：Heat transport in the Earth’s mantle governs its thermal state and long-term evolution. Ringwoodite, a high-pressure polymorph of olivine, constitutes ~60 vol% of the mantle transition zone (MTZ) and ~80 vol% of harzburgitic lithologies subducted into the deep mantle, thus playing a central role in MTZ dynamics. Seismic and electromagnetic tomography suggest thermochemical heterogeneity in the MTZ, with anomalies potentially linked to water. Differences in thermal conductivity between dry and hydrous ringwoodite may therefore be critical in understanding mantle heat transport, yet data for dry ringwoodite remain scarce due to synthesis challenges. In this study, we synthesized a dry (Mg_0.9Fe_0.1)₂SiO₄ ringwoodite under deep-mantle oxygen fugacity (IW buffer) using a Kawai-type multi-anvil press at 20 GPa and 1775 K. Thermal conductivity and thermal diffusivity were measured simultaneously up to 1100 K by the pulse heating method. Results show that dry ringwoodite exhibits higher thermal conductivity than previously reported values for hydrous samples, indicating water suppresses thermal transport. At the 660 km discontinuity, thermal conductivity of dry ringwoodite is ~15% higher than decomposed post-spinel assemblages and ~45% higher than Al,Fe-bearing bridgmanite, while hydrous ringwoodite is comparable to the latter. These results suggest that in dry regions, enhanced thermal conductivity may promote rapid heat redistribution, accelerating local heating near upwelling plumes. In contrast, hydrous regions within or adjacent to stagnant slabs may trap heat and evolve more slowly. Such differences in thermal transport likely contribute to the thermal and chemical heterogeneity revealed in geophysical observations of the MTZ.

个人简介：张友悦助理教授，日本爱媛大学。主要研究方向包括高温高压下矿物热导率的测量、高温高压下金属矿物的相变、高温高压下高质量多晶与单晶硅酸盐矿物的合成、高压中子衍射实验等。发展了大腔体压机高温高压热导率热扩散率同步测量的实验技术、使这项技术得以在地球下地幔条件应用，研究成果发表在PNAS，EPSL，GRL等专业期刊上。