University of Cambridge > Talks.cam > BPI Seminar Series > The viscosities of partially molten materials undergoing diffusion creep

The viscosities of partially molten materials undergoing diffusion creep

Add to your list(s) Download to your calendar using vCal

If you have a question about this talk, please contact Catherine Pearson.

Partially molten materials resist shearing and compaction. This resistance is described by a fourth-rank effective viscosity tensor. When the tensor is isotropic, two scalars determine the resistance: an effective shear and an effective bulk viscosity. In this seminar, calculations are presented of the effective viscosity tensor during diffusion creep for a 3D tessellation of tetrakaidecahedrons (truncated octahedrons). The geometry of the melt is determined by assuming textural equilibrium. Two parameters control the effect of melt on the viscosity tensor: the porosity and the dihedral angle. Calculations for both Nabarro-Herring (volume diffusion) and Coble (surface diffusion) creep are presented. For Nabarro-Herring creep the bulk viscosity becomes singular as the porosity vanishes. This singularity is logarithmic, a weaker singularity than typically assumed in geodynamic models. The presence of a small amount of melt (0.1% porosity) causes the effective shear viscosity to approximately halve. For Coble creep, previous modelling work has argued that a very small amount of melt may lead to a substantial, factor of 5, drop in the shear viscosity. Here, a much smaller, factor of 1.4, drop is obtained.

This talk is part of the BPI Seminar Series series.

Tell a friend about this talk:

This talk is included in these lists:

Note that ex-directory lists are not shown.

 

© 2006-2019 Talks.cam, University of Cambridge. Contact Us | Help and Documentation | Privacy and Publicity