High Pressure-Temperature Equations of State, Oxygen Fugacity, and Earth's Core

高压-温度状态方程、氧逸度和地核

• 批准号: 0635722
• 负责人: Andrew Campbell
• 金额: --
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-12-01 至 2010-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635722&HistoricalAwards=false
• 关键词: Pressure; Temperature; Equations; State; Oxygen

The properties of materials at high pressure and temperature are essential for understanding the Earth's deep interior. This project is extending our understanding of the equations of state (pressure - volume - temperature relationships) of several geophysically important materials, through in situ measurement of unit cell volumes under high pressure, high temperature conditions (up to 100 GPa and 2500 K). Simultaneous pressure - volume - temperature measurements of a metal and its coexisting oxide provide a more precise measure of their relative equations of state than measurements of each phase separately. Synchrotron x-ray diffraction is used to measure volumes of both phases, and high pressures and temperatures are generated using a laser heated diamond anvil cell. Complementary studies using a multi-anvil press are also underway; these strengthen the data set in the lower pressure range ( 25 GPa). The experimental methodologies for both sets of experiments was successfully demonstrated in earlier investigations, but had not been broadly applied. Metals and oxides are being studied primarily, including iron-iron oxide, nickel-nickel oxide, and rhenium-rhenium oxide. There are several applications of these data to studies of the Earth's interior. One is the improved extension of oxygen fugacity buffers to high pressures, by integration of precise, experimentally determined relative volumes of coexisting metal-oxide phases. These results allow one to better quantify the oxygen potential at high pressures, which is needed to understand, for example, core-mantle interaction and elemental partitioning in the mantle. Furthermore, the oxygen fugacity conditions of many high pressure geochemical studies are either controlled by, or referenced to, these metal-oxide buffers. Precise comparison of experimental results that are based on different buffers requires knowledge of the relative shifts of those buffers with increasing pressure. Finally, these studies facilitate direct comparison of experimentally determined densities of candidate core constituents with the observed, seismologically constrained density profiles of the core. More data have been needed here to improve precision and reduce extrapolations, especially at high temperature. The information gained from this project will benefit our understanding of the chemical evolution of the planet and the formation of the core.

材料在高压和高温下的特性对于了解地球深处至关重要。该项目通过在高压、高温条件（高达 100 GPa 和 2500 K）下原位测量晶胞体积，扩展了我们对几种地球物理重要材料的状态方程（压力 - 体积 - 温度关系）的理解。与单独测量每个相相比，同时测量金属及其共存氧化物的压力-体积-温度可以更精确地测量它们的相对状态方程。同步加速器 X 射线衍射用于测量两相的体积，并使用激光加热金刚石砧室产生高压和高温。使用多砧压机的补充研究也在进行中；这些加强了较低压力范围（25 GPa）的数据集。两组实验的实验方法在早期的研究中都得到了成功的证明，但尚未得到广泛应用。主要研究金属和氧化物，包括铁-氧化铁、镍-氧化镍和铼-氧化铼。这些数据在地球内部研究中有多种应用。一是通过整合精确的、实验确定的共存金属氧化物相的相对体积，将氧逸度缓冲扩展到高压。这些结果使人们能够更好地量化高压下的氧势，这是理解核心-地幔相互作用和地幔中元素分配等所必需的。此外，许多高压地球化学研究的氧逸度条件要么由这些金属氧化物缓冲液控制，要么参考这些金属氧化物缓冲液。对基于不同缓冲器的实验结果进行精确比较需要了解这些缓冲器随着压力增加的相对变化。最后，这些研究有助于将实验确定的候选岩心成分的密度与观察到的、地震学约束的岩心密度剖面进行直接比较。这里需要更多的数据来提高精度并减少外推，特别是在高温下。从这个项目中获得的信息将有助于我们了解地球的化学演化和地核的形成。