CSEDI: Thermal conductivity of lower mantle minerals and heat flow across the core/mantle boundary

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

The heat flow across the Earth's core-mantle boundary controls the thermal evolution of the whole Earth, which is ultimately expressed on the surface by plate tectonics. However the thermal properties of the core/mantle boundary are not well known, leading to significant uncertainties in our understanding of the temperature and heat profile of the Earth - both currently and in the past. The goal of this proposal is to determine the thermal properties -especially thermal conductivity- of the Earth's mantle, through a combination of experiment and modeling. This information will be used to help constrain the temperature profile throughout the Earth's interior, the style of mantle convection, and the timing for the growth of the inner core. We will combine methods from theoretical and experimental mineral physics and heat flow modeling in crystalline bulk and in composite materials to measure the thermal conductivity of the deep Earth. Starting with a data set describing the lattice thermal conductivity of MgO and MgSiO3 at deep mantle conditions, we will measure how the presence and behavior of iron changes those values at high pressures and temperatures. The experimental data will be interpreted with help from computational models of heat flow in the laser-heated diamond cell, used to make these measurements. Finally, we examine the implications for the mantle using a heat flow model for composite materials and including both conduction and radiation. The overall outcome will be an estimate of the thermal conductivity of the lower mantle at core/mantle boundary conditions, and how the thermal conductivity varies with pressure, temperature, and composition. This project brings together two scientists from very different disciplines: a mechanical engineer with expertise in heat transfer and a geophyscist with expertise in measurements of physical properties under extreme conditions. This interdisciplinary project will support the training of a graduate student for three years. In addition, this project will support summer research for undergraduates at UCLA. Measurements of thermal properties of materials under extreme conditions are important not only for Earth & planetary science, but also for engineering, materials science, and physics. Both researchers are actively involved in science education and outreach at all levels, and have active research groups including undergraduate and graduate students, and postdoctoral scholars.