Experimental studies on plastic deformation of the lower mantle materials

Yale University, New Haven CT

Investigators

Abstract

In this project, the PI team will study the plastic flow behavior of materials in the lower mantle of the Earth that occupies a large fraction of Earth between the upper mantle and the core. Plastic deformation in this region is an important mechanism of cooling of Earth and it also controls the way in which materials are stirred or mixed. The experimental studies on plastic deformation under the conditions of the lower mantle have been difficult due to the difficulties in generating and measuring stress and strain under these conditions. The team has made various modifications to the deformation apparatus that was developed in their lab to conduct these deformation experiments. The results will provide the first data set to understand the whole Earth thermal and chemical history. Rheological properties of the lower mantle will be investigated using a rotational Drickamer apparatus developed in in the PI's laboratory. This apparatus, after numerous modifications, now allows his team to conduct large strain quantitative deformation experiments (to strain ~100-300%) under shallow lower mantle conditions (P to 28 GPa, T to 2200 K) providing the quantitative results on rheological behavior under these conditions. Not only the flow laws of each mineral, but also the microstructural evolution will be studied to provide the mechanisms of deformation and the nature of lattice-preferred orientation that can be used to interpret seismic anisotropy.