Measurements of sound velocity and density of core materials by combination of dynamic and static methods

Carnegie Institution Of Washington, Washington DC

Investigators

Abstract

Earth's metallic core is the engine of the planet, providing the energy to generate its magnetic field and the driving force for plate tectonics. The properties the core control the function of the engine. It is fundamentally important to understanding the physical and chemical properties of the core in order to understand how our planet works. The density and velocity profiles of the core have been derived from seismic observations. Accurate measurements of density and velocity of core iron-alloys under simultaneous high pressure and temperature are required to derive meaningful composition models of the core. Dr. Yingwei Fei investigates the density and sound velocity of core materials over a wide pressure-temperature range by combining static and dynamic experimental methods. The results will be used to develop a comprehensive core composition model. The study will promote interdisciplinary research and significantly advance knowledge of the Earth's core and its influence on the dynamics processes of the planet. The projects will provide training in interdisciplinary research areas for graduate students and postdoctoral associates. The high-pressure techniques developed through the project will have general applications for synthesis of advanced materials, particularly super-hard materials. The objective of the research is to obtain the best measurements of the density and sound velocity of core materials in the Fe-S-Si-O system by combination of static high-pressure compression and shockwave experiment. The proposed projects include (1) measurements of density and sound velocity of a Fe-9wt%O alloy and Fe-3wt%S-3wt%Si-3wt%O mixture by shock compression, and (2) additional measurements of density and sound velocity of an Fe-9wt%Si alloy by static and dynamic compressions. The proposal outlines a new approach to define the density and velocity of the end-member alloys whose compositions are close to the estimated core composition in a binary system. The data obtained in a suite of binary systems can be interpolated in a small range for a multi-element core composition that includes Fe, S, Si, and O. The interpolation will be further tested against new experimental measurements on a multi-element composition (Fe-3wt%S-3wt%Si-3wt%O), and ultimately narrow down the core composition range that is consistent with the geophysical observations.