The mantle rheology always fascinates me. I worked on deformation experiments of olivine using Griggs apparatus as an undergraduate student at CUG supervised by Prof. Junfeng Zhang. Specifically, I study the fabric of water-bearing olivine under the plastic deformation at pressures and temperatures relevant to the upper mantle. The experiments were very challenging and time-consuming. I spent over several months and got two successful Griggs runs. I am digging into my old files to look for the results that I remember are actually quite interesting, though they were not complete enough to support a paper.
With the mantle rheology kept in mind, after obtaining the melting curves of one of Earth’s most abundant minerals, (Mg, Fe)O ferropericlase, I related them to the viscosity of ferropericlase using the homologous temperature scaling. I showed, for the first time, the melting temperature depression at a depth of ~1000 km for ferropericlase indicates a viscosity jump within the mantle and providing a unified mechanism to explain the subducting slab stagnation and upwelling plume deflection at these depths (Deng and Lee, 2017, Nature Comms).