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

通过地核-地幔边界的热流控制着整个地球的热演化，最终通过板块构造在地表表现出来。然而，地核/地幔边界的热性质尚不清楚，这导致我们对地球当前和过去的温度和热分布的理解存在很大的不确定性。这项提议的目标是通过实验和建模相结合的方法来确定地幔的热特性，尤其是热导率。这些信息将用于帮助确定整个地球内部的温度分布、地幔对流的方式以及内核生长的时间。我们将结合理论和实验矿物物理以及晶体体和复合材料的热流建模方法来测量地球深部的导热性。从描述深地幔条件下MgO和MgSiO3晶格热导率的数据集开始，我们将测量铁的存在和行为如何在高压和高温下改变这些值。实验数据将在用于测量的激光加热金刚石细胞的热流计算模型的帮助下进行解释。最后，我们使用复合材料的热流模型，包括传导和辐射，研究了对地幔的影响。总体结果将是估计下地幔在核心/地幔边界条件下的热导率，以及热导率如何随压力、温度和成分变化。该项目汇集了来自不同学科的两位科学家：一位是具有传热专业知识的机械工程师，另一位是具有极端条件下物理性质测量专业知识的地球物理学家。这个跨学科的项目将支持培养一名研究生三年。此外，该项目将支持加州大学洛杉矶分校本科生的暑期研究。测量极端条件下材料的热性能不仅对地球和行星科学很重要，而且对工程、材料科学和物理学也很重要。两位研究人员都积极参与各级科学教育和推广工作，拥有包括本科生、研究生和博士后在内的活跃研究小组。

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.