In situ falling sphere viscometry for silicate melts down to the lower mantle: An application of the B-doped diamond heater

谢龙健于2018年9月完成博士学位。他总结了近五年来取得的成就。它包括三个方面：在多砧装置中开发掺硼金刚石（BDD）加热器，使用现场落球法测量硅酸盐熔体的粘度高达~30 GPa，并根据他的研究中新测量的硅酸盐熔体粘度讨论岩浆海洋（MO）的演化。他的研究重点是（1）产生~4000 K温度（2）在现场落球粘度计中应用BDD加热器测量了下地幔条件下硅酸盐熔体的粘度，（3）粘度数据首次在实验上重现，分子动力学模拟提出的四种压力致密化机制均为有效的，（4）粘度数据也表明岩浆海洋的分离凝固，分馏凝固模型表明，原始上地幔可能是约900 km MO经钙钛矿和钙钛矿复合分馏后的残留物（质量比：94：6），在MO底部形成一个堆积层（~660-900 km深）。

Xie Longjian completed PhD degree September 2018. He summarized his achievements during the recent five years. It consists three aspects: boron-doped diamond (BDD) heater development in multi-anvil apparatus, viscosity measurement of silicate melts up to ~30 GPa using in-situ falling sphere method and discussion on the evolution of the magma ocean (MO) based on the silicate melt viscosity newly measured in his study. Highlights of his study were (1) generation of ~4000 K temperature (world highest) in the Kawai multi-anvil apparatus by using BDD heater, (2) world first measurements of silicate melt viscosity under the lower mantle condition by applying BDD heater in the in-situ falling sphere viscometry, (3) the viscosity data first time reproduces, experimentally, all the four pressure induced densification mechanisms proposed by molecular dynamic simulation, (4) the viscosity data also suggests a fractional solidification of magma ocean, and (5) the fractional solidification model suggests that the primary upper mantle may be the residual of a ~900 km MO after a combination fractionation of bridgmanite and CaSiO3 perovskite (mass ratio: 94:6), which formed a cumulate layer (~660-900 km depth) at the bottom of MO.