Collaborative Research: Density and structure of s

合作研究：密度和结构

• 批准号: 1620548
• 负责人: Yanbin Wang
• 金额: $ 33.6万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1620548&HistoricalAwards=false
• 关键词: Collaborative; Research; Density; structure

Silicates, the major constituents of Earth's outer crust and rocky mantle layers, melt at very high temperatures, especially at deeper depths. Liquid forms of silicates played a pivotal role in the early evolution history of planet Earth and continue to influence dynamic processes in present day. The early Earth was most likely molten after the formation process. As the Earth cooled off, liquid silicates solidified and crystals of particular compositions formed at various stages of the cooling process, defining the composition structure of the Earth as we have today. Giant amounts of magmas are ascending from present-day mid-ocean ridges, a process closely related to plate tectonics. The cooling products of these magmas form the ocean floors. Volcanic activities over the globe change the environment and endangering human lives. Understanding the dynamics and thermodynamics of these processes requires knowledge of density, viscosity, and structure of silicate liquids over a wide range of pressure conditions corresponding to the Earth's interior. Efforts for obtaining such knowledge have been impeded by technical challenges in the past. To overcome the technical challenges, the investigators have developed a series of synchrotron-based techniques for studying density, compressibility, and structure of silicate liquids under high pressure and temperature conditions. This research will support the training and mentoring of a graduate student and post doc, and will provide support to early career scientists. The investigators propose to study structure-density relations of liquids with selected compositions in the system Na2O-CaO-MgO-FeO-Al2O3-SiO2 to cover major components of mafic to ultramafic liquids relevant to deep mantle melting, by combining advanced techniques using large-volume presses and synchrotron radiation. Structure data will be collected in the Paris-Edinburgh press to 20 GPa and 2500 K. Density will be determined using both in-situ X-ray absorption and ex-situ sink/float techniques. To complement density measurements, sound velocities of selected low-viscosity liquid compositions will be measured using ultrasonic interferometry in a double-stage multianvil press. With these data the team will examine the link between structure and density/compressibility across the pressure range where tetrahedral-to-octahedral coordination change of network formers (Si and Al) occurs. This work will provide vital experimental constraints on modeling liquid compression at deep mantle conditions, by (1) gaining insights into structural evolution of silicate liquids through coordination changes over the pressure range covering the upper mantle, transition zone, and the top of the lower mantle (2) obtaining data on density and acoustic velocity through the coordination transition in liquids, and (3) establishing new equations of state for silicate liquids incorporating structural information, to enable better prediction of liquid density under deep mantle conditions.

硅酸盐，地球外壳和岩石地幔层的主要成分，在非常高的温度下融化，特别是在更深的深处。液态硅酸盐在行星地球的早期演化历史中发挥了关键作用，并继续影响着当今的动态过程。早期的地球在形成过程后很可能是熔融的。随着地球的冷却，液态硅酸盐凝固，在冷却过程的不同阶段形成了特殊成分的晶体，定义了我们今天地球的成分结构。大量的岩浆正从现今的洋中脊上升，这一过程与板块构造密切相关。这些岩浆的冷却产物形成了海底。全球的火山活动改变了环境，危及人类的生命。要了解这些过程的动力学和热力学，就需要了解硅酸盐液体在与地球内部相对应的各种压力条件下的密度、粘度和结构。过去，获得这类知识的努力受到技术挑战的阻碍。为了克服技术挑战，研究人员开发了一系列基于同步加速器的技术，用于研究高压和高温条件下硅酸盐液体的密度、可压缩性和结构。这项研究将支持研究生和博士后的培训和指导，并将为早期职业科学家提供支持。研究人员提出，通过结合大型压机和同步辐射等先进技术，研究na20 - cao - mgo - feo - al2o3 - sio2体系中选定成分的液体的结构-密度关系，以涵盖与深部地幔熔融有关的基性至超基性液体的主要成分。结构数据将在巴黎-爱丁堡出版社收集到20gpa和2500k。密度将使用原位x射线吸收和非原位汇/浮技术来确定。为了补充密度测量，将在双级多砧压力机中使用超声干涉测量法测量选定的低粘度液体成分的声速。有了这些数据，研究小组将研究结构和密度/可压缩性之间的联系，在压力范围内，网络形成物（Si和Al）的四面体到八面体配位变化发生了。通过(1)通过覆盖上地幔、过渡带和下地幔顶部的压力范围内的配位变化来深入了解硅酸盐液体的结构演化(2)通过液体中的配位转变获得密度和声速数据，本工作将为深部地幔条件下液体压缩建模提供重要的实验约束。(3)建立了包含结构信息的硅酸盐液体状态方程，以便更好地预测深部地幔条件下的液体密度。