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MULTISCALE MODELLING OF THE RHEOLOGY OF MANTLE MINERALS

Final Report Summary - RHEOMAN (MULTISCALE MODELLING OF THE RHEOLOGY OF MANTLE MINERALS)

The Earth expels its internal heat through large scale deformations which stir the mantle from ca. 2900 km depth. These deformations have their origin at the atomic scale within the high pressure minerals which constitute the rocks of the mantle. Reproducing these deformations in the laboratory is challenging due to the extreme pressures and temperatures of the mantle, and also due to the very slow, geological timescales involved. To overcome these limitations, we have developed in the RheoMan project a multiscale numerical approach which, starting from the atomic scale, models the nature and dynamics of the crystal defects responsible for flow in the mantle. We have shown that in bridgmanite, a high-pressure mineral stable below 670 km depth and constitutes about half of the Earth’s mass, atomic diffusion and crystal defects named dislocations combine to produce flow through an original mechanism called pure climb creep which is extremely difficult to reproduce in the laboratory. We also show that although pressure hardens minerals, unexpected ductility is exhibited by some minerals close to the core-mantle boundary. This has important implications on how heat is extracted from the core and transferred to the surface.