Perovskite and post-perovskite in the (Mg,Fe)GeO3 system

(Mg,Fe)GeO3体系中的钙钛矿和后钙钛矿

• 批准号: 1415321
• 负责人: Thomas Duffy
• 金额: $ 36万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1415321&HistoricalAwards=false
• 关键词: Perovskite; post; perovskite; Mg; Fe

The geological activity at Earth's surface that can so profoundly affect humanity ultimately arises from on-going processes within the deep interior. These large-scale processes are in turn controlled by the properties of the constituent materials of the deep Earth. A mineral's crystal structure is its most fundamental characteristic, from which all other physical and chemical properties follow. Due to the incredibly high pressures (millions of atmospheres) and temperatures (thousands of degrees) of the deep Earth, our knowledge of the crystal structures of minerals residing near the base of Earth's mantle remains far from complete. This region of the Earth is primarily composed of silicate minerals that adopt structures known as perovskite and post perovskite. In this project, the PI will conduct laboratory experiments to probe the basic structural properties of magnesium iron germanates, a class of compounds that serve as close analogs for the silicate minerals of the deep Earth, but which can be studied at lower pressures and temperatures which are more easily attainable in the laboratory. Through this work, he and his team will provide fundamental knowledge of mineral crystal structures and properties that are needed to understand and interpret geophysical observations of the Earth's interior. The Earth's deep lower mantle is key for understanding the overall structure, dynamics, and evolution of the planet. Seismic evidence indicates this region exhibits considerable chemical heterogeneity as exemplified by features such as large low shear velocity provinces, ultra-low velocity zones, and the complexity of the core-mantle boundary region. The PI will conduct high-pressure X-ray experiments on Fe-bearing compositions in the (Mg,Fe)GeO3 system, an analog for the silicates of the deep mantle. The advantage of this system is that the perovskite to post-perovskite transition occurs at much lower pressure for germanates, allowing the team to avoid or reduce the experimental complications that plague silicate studies at ultrahigh pressures. They will use the laser-heated diamond anvil cell to carry out a series of synchrotron-based studies of the crystal structure, equation of state, electronic configuration, and local environment of iron in germanates with the perovskite and post-perovskite structures. The results will lead to a better understanding of how iron content affects mineralogical behavior in these phases and will directly impact the fields of seismology, petrology, geodynamics, geochemistry, and mineralogy.

地球表面的地质活动，可以如此深刻地影响人类，最终产生于内部深处正在进行的过程。这些大规模的过程反过来又受到地球深部组成材料的性质的控制。 矿物的晶体结构是其最基本的特征，所有其他物理和化学性质都是由此而来的。 由于地球深处的压力（数百万个大气压）和温度（数千度）令人难以置信，我们对地幔底部附近矿物晶体结构的了解仍然远远不够。地球的这个区域主要由硅酸盐矿物组成，这些矿物采用称为钙钛矿和后钙钛矿的结构。 在这个项目中，PI将进行实验室实验，以探测镁铁锗酸盐的基本结构特性，这是一类化合物，作为地球深部硅酸盐矿物的类似物，但可以在较低的压力和温度下进行研究，这些压力和温度更容易在实验室中获得。通过这项工作，他和他的团队将提供了解和解释地球内部地球物理观测所需的矿物晶体结构和性质的基础知识。地球深部的下地幔是了解地球整体结构、动力学和演化的关键。地震证据表明，这一地区表现出相当大的化学不均匀性，例如大的低剪切速度省，超低速带，核幔边界区的复杂性的功能。PI将对（Mg，Fe）GeO3系统中的含铁成分进行高压X射线实验，该系统是深部地幔硅酸盐的模拟物。该系统的优点是，对于锗酸盐来说，钙钛矿到后钙钛矿的转变发生在低得多的压力下，这使得该团队能够避免或减少在高压下困扰硅酸盐研究的实验复杂性。他们将使用激光加热的金刚石对顶砧单元对具有钙钛矿和后钙钛矿结构的锗酸盐中的铁的晶体结构、状态方程、电子构型和局部环境进行一系列基于同步加速器的研究。研究结果将有助于更好地了解铁含量如何影响这些阶段的矿物学行为，并将直接影响地震学，岩石学，地球动力学，地球化学和矿物学领域。