CAREER: High Pressure Melting and Phase Transitions in Model Compositions of Earth's Core

在地球表面观察到的许多地质过程都是在地球深处发生的过程的表现。因此，重要的是要了解深部内部的构成和动态，以及这些过程随时间的演变。众所周知，地球最深处的S，也就是它的核心，大部分是铁，但其剩余的10%左右的成分是不确定的。确定地核的这一组分是回答有关地球起源、演化和动力学的一些地球物理和地球化学问题的关键-S内部；例如，地球形成过程中的氧化/还原和挥发分损失的程度，以及产生地球的过程的能量学？S磁场，与地核的组成有关。该项目将使我们能够通过实验更好地了解地核，这些实验旨在测量高铁合金在高压和高温下的性质，可以与地球深处存在的条件相媲美。具体地说，在这些实验中，我们将测量代表堆芯建议成分的候选合金成分中的熔化温度，并确定在高压下与熔体共存的固相(S)的成分和结构。这些数据将使我们能够测试地核候选成分的可信程度。利用红外激光加热的金刚石顶锤单元，可以产生实验所需的高压(100 Gpa)和温度(3000 K)。在研究人员的家庭实验室中，将使用光学方法，包括一种新开发的测量实验中温度分布的方法，来确定熔化和其他相变发生的温度。这些转变的进一步表征将使用同步加速器X射线源来探测样品在高压、高温状态下的结构。作为研究训练的一部分，学生将从参与针对这些实验的改进技术的开发中受益。这个职业项目的更大的教育目标是将这项研究和矿物物理学的教学整合到一个广泛的努力中，以扩大马里兰大学地球物理教育的机会。

Many of the geological processes that are observed on the surface of the Earth are manifestations of processes occurring at great depth in the planet. Consequently it is important to understand the constitution and dynamics of the deep interior, as well as the evolution of these processes over time. It is known that the Earth?s innermost region, its core, is mostly iron, but the remaining 10% or so of its constitution is uncertain. Identifying this component of the core is key to answering a number of geophysical and geochemical questions about the origin, evolution, and dynamics of our planet?s interior; for example, the extent of oxidation/reduction and loss of volatiles during Earth formation, and the energetics of the processes generating the Earth?s magnetic field, are linked to the composition of the core. This project will allow us to better understand the Earth's core through experiments designed to measure the properties of iron-rich alloys at high pressures and high temperatures, comparable to the conditions that exist in the planet's deep interior. Specifically, in these experiments we will measure the temperatures of melting in candidate alloy compositions that represent proposed compositions of the core, and also determine the composition and structure of the solid phase(s) that coexist with the melt at high pressures. These data will allow us to test the plausibility of the candidate compositions of Earth's core. Diamond anvil cells, with infrared laser heating, are used to generate the high pressures (100 GPa) and temperatures (3000 K) necessary for the experiments. In the investigator's home laboratory, optical methods, including a newly developed method of measuring temperature distributions in the experiment, will be used to determine the temperatures at which melting and other phase transitions occur. Further characterization of these transitions will be performed using synchrotron X-ray sources to probe the structure of the samples in their high pressure, high temperature state. As part of their research training, students will benefit from participating in the development of improved techniques specific to these experiments. The greater educational aim of this CAREER project is to integrate this research, and teaching mineral physics, into a broad effort to expand the opportunities for geophysics education at the University of Maryland.