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

谢龙剑，2018年9月获博士学位。他总结了自己近五年来的成就。主要包括三个方面：多砧装置中掺硼金刚石（BDD）加热器的研制、原位落球法测定~ 30gpa硅酸盐熔体粘度和基于新测硅酸盐熔体粘度的岩浆海（MO）演化讨论。他的研究重点是：(1)利用BDD加热器在Kawai多砧装置上产生了~4000 K的世界最高温度；(2)利用BDD加热器在原位降球粘度测量中首次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再现了分子动力学模拟提出的四种压力致致密机制。(4)黏度数据也表明岩浆海洋存在分馏性凝固；(5)分馏性凝固模型表明，初生上地幔可能是一段~900 km MO经过桥菱铁矿和CaSiO3钙钛矿（质量比：94:6）联合分馏后的残余，在MO底部形成了一层~660 ~900 km深度的堆积层。

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.