Collaborative Research: Physical properties and structure of silicate melts and supercooled liquids at high pressures

地球的热演化和化学分异涉及硅酸盐和金属熔体的分离，以及由于密度差异而共存的矿物。这一单一因素影响了地球形成水圈和生物圈的初始条件（成为一个可居住的星球），岩浆分化的效率，火山系统的演化和喷发的特征，一些经济矿床的形成，通过深部地幔的挥发物的运输，以及穿过核心地幔边界的热传递，这反过来又影响了磁场的产生。矿物和熔体之间的浮力关系是由于熔体比矿物具有更大的压缩性而引起的强大的压力函数。考虑到难熔性、缺乏长期结构顺序以及适应熔体致密化的复杂结构变化，量化压力增加对熔体性能的响应是具有挑战性的。关键的测量必须在控制良好的实验室条件下进行。这项研究的结果将大大提高我们对地球动力学过程的理解，以及与构造板块运动和全球地球化学循环的联系。本研究采用新颖的高压实验方法，利用原位x射线技术（微断层扫描、吸收和衍射）和声速测量来确定深部地球条件下熔体的体积特性和结构变化。这些结果将有助于对岩浆海洋的性质、地核的形成、分离和对流动力学，以及最终对地球的热学和化学演化进行更严格的限制。这些数据也将有助于我们理解当今的动力学，包括岩浆在地壳和地幔中的储存和运输、大洋中脊构造板块的扩张、地幔柱上涌以及在核幔边界可能发生的反应。此外，我们与该项目相关的努力将有助于进一步扩大高压下微断层扫描研究的机会，以研究部分熔化和变形，以及其他需要详细3D微观结构表征的高压现象。预计这项工作的结果将在寻找和表征新的在高温高压下合成的奇异材料的工业应用方面具有长期的好处。

The thermal evolution and chemical differentiation of the Earth involves the segregation of silicate and metallic melts, and coexisting minerals due to differences in their density. This single factor impacts the initial condition as the Earth formed its hydrosphere and biosphere (to become a habitable planet), the efficiency of magmatic differentiation, evolution of volcanic systems and character of eruptions, formation of some economic ore deposits, transportation of volatiles through the deep mantle, and heat transfer across the core mantle boundary which, in turn, impacts generation of the magnetic field. The buoyancy relations between minerals and melts are strong functions of pressure caused by the greater compressibility of melts compared to minerals. Quantifying the response of increasing pressure on melt properties is challenging given the refractory nature, absence of long range structural order, and complex structural change that accommodates densification of melts. Critical measurements must be made under well-controlled laboratory conditions. The results of this research will greatly improve our understanding of dynamic processes within our planet and links to motions of the tectonic plates and global geochemical cycle.This research employs novel high-pressure experimental methods utilizing in situ X-ray techniques (microtomography, absorption and diffraction) and acoustic velocity measurements to determine the volumetric properties and structural changes in melts at deep Earth conditions. The results will help place tighter constraints on properties of the magma ocean, core formation, segregation and convection dynamics, and, ultimately, the thermal and chemical evolution of the Earth. These data will also contribute to our understanding of present-day dynamics involving the storage and transport of magma through the crust and mantle, spreading of tectonic plates from mid-ocean ridges, mantle plume upwelling, and possible reactions at the core-mantle boundary. Additionally, our efforts in connection with this project will help to further expand the opportunities for microtomography research at high pressures for the study of partial melting and deformation, among other phenomena at high pressures requiring detailed microstructure characterization in 3D. It is anticipated that the results of this work will have long-term benefits in the search and characterization of new exotic materials synthesized at high temperature and pressure for industrial applications.