Renewal-Experimental Studies of Elasticity, Rheology, and Phonon Dynamics of Materials at Pressure-Temperature Conditions of Earth's Mantle and Core

Carnegie Institution Of Washington, Washington DC

Investigators

Abstract

Plate tectonics, one of the most important scientific discoveries in the last century, is the surface manifestation of the dynamic processes of its much deeper roots. Recent tomographic and geodynamic studies provided detailed three-dimensional descriptions of the solid Earth. Interpretations of these results require additional knowledge on the real materials that constitute the deep Earth and whose properties are drastically altered by its extreme P-T conditions. Key properties include: Density, r (or molar volume, V) Crystal unit-cell parameters (a, b, c, a, b, g) Bulk modulus (K), shear modulus (G), and single-crystal elasticity (cij or sij) Compressional (VP) and shear wave velocity (VS) as a function of crystallographic orientation Phonon density of state (DOS) and phonon dispersion Preferred orientation under stress Shear Strength, creep law, and deformation mechanism Comprehensive understanding of the static and dynamic Earth depends upon our knowledge of these parameters as functions of pressure and temperature. For a long time, only r and K measurements were possible beyond transition-zone pressures (>25 GPa) and most measurements were regarded as reconnaissance in nature. Consequently, Earth models are often tenuous and controversial. Resulted from the previous grant support, a series of breakthroughs in high-pressure technology has finally made it possible to propose a study of all these properties. Using the new technology, the present grant supports a comprehensive and integrated series of experimental studies of the elastic, rheological, and phonon properties of deep mantle and core materials at high pressures and temperatures. The results will be used to resolve major problems associated with the composition, structure, dynamics, and evolution of the Earth's deep interior.