Supervisor: John Rudge (Earth Sciences)
Importance of the area of research:
Beneath mid-ocean ridges the mantle melts, and that melt rises to the surface to form new crust. Quite how the melt rises, and how the melt network is organised beneath the ridge, is poorly understood. Geochemical observations suggest that the process of melt ascent is relatively rapid; much more rapid than one would predict from simple porous flow theory. It remains an outstanding fluid dynamical challenge to explain the process of melt ascent. Fundamental to any fluid dynamical model is the rheology of the partially molten mantle, which is also poorly understood.
The aim of this project is to devise new micro-mechanical models of partially molten rock, and then upscale these models to produce continuum models of rock rheology that can be applied at tectonic-scales. A particular focus will be the interaction between deformation and the topology of the melt network. The models will be ground-truthed by comparison with the results of laboratory experiments, and in particular the recent deformation experiments that have been performed in the laboratories of Yasuko Takei (University of Tokyo) and David Kohlstedt (University of Minnesota).
What the student will do:
This project is largely theoretical and computational, and the student will be involved both in developing new theory and developing new numerical codes. The student will first construct a partial-differential-equation-based model of rock deformation based on physical principles of conservation of mass, momentum and energy. The student will then develop code to numerically solve the relevant governing equations. Comparisons between the models and the lab experiments will be used to inform and develop new theoretical ideas about rock rheology, and in turn new ideas on the nature of melt transport through the mantle.
Kohlstedt, D.L., Holtzman, B.K. 2009. Shearing melt out of the Earth: An experimentalist's perspective on the influence of deformation on melt extraction. Annu. Rev. Earth Planet. Sci. vol. 37, pp.561-593. doi:10.1146/annurev.earth.031208.100104
Takei, Y., Holtzman, B.K. 2009. Viscous constitutive relations of solid-liquid composites in terms of grain boundary contiguity: 1. Grain boundary diffusion control model. J. Geophys. Res. vol. 114, B06205. doi:10.1029/2008JB005850
Ghanbarzadeh S., Prodanovic M., Hesse M.A. 2014. Percolation and grain boundary wetting in anisotropic texturally equilibrated pore networks. Phys. Rev. Lett. vol. 113. 048001. doi:10.1103/PhysRevLett.113.048001
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