Stress-driven melt redistribution in partially molten rocks deformed in torsion: from pressure shadows to base-state segregation

Abstract

The redistribution of melt in partially molten rocks during deformation plays an important role in the evolution and dynamics of Earth's mantle. Previous studies discovered different scales of melt redistribution: melt alignment and melt segregation to form melt-enriched bands , both of which have demonstrated their importance to the deformation of the mantle. In this dissertation, two new forms of stress-driven melt redistribution in deformed partially molten rocks are produced: a formation of pressure shadows around rigid particles and a large-scale, base-state melt segregation. For pressure shadows, observations on the microstructure around the rigid particles revealed the melt distribution and solid flow field, which will provide a constraint on the bulk viscosity of the partially molten rock, if associated with theoretical studies. The presence of base-state melt segregation validated a hypothesis of viscous anisotropy, which provides explanations for melt segregation processes and will cause a significant impact to the dynamic of the mantle. Therefore, the studies of stress-driven melt redistribution in this dissertation are of great significance that will influence the future studies of Earth's mantle.