The structure of silicate magmas, melts and glasses

硅酸盐岩浆、熔体和玻璃的结构

• 批准号: RGPIN-2019-04889
• 负责人: Henderson, Grant
• 金额: $ 2.19万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751227
• 关键词: structure; silicate; magmas; melts; glasses

Understanding the behaviour of molten rock or melts under the conditions found deep in the Earth is important if we are to understand how the Earth formed, how magmas evolve, and their chemical and dynamical behaviour below the surface of the Earth. I am studying such molten materials under these conditions. I investigate how the structure of such liquids change under ambient conditions (using quenched liquids or glasses) as well as extreme conditions. I primarily use state-of-the-art synchrotron based techniques in addition to techniques such as Raman spectroscopy. In particular, experimental beamlines at the Canadian Light Source and other international light sources are used to study the environment around elements commonly found in geological melts and magmas such as Si, O, Al, alkalis and alkaline-earths. In collaboration with a number of international research groups we probe the structure of simple synthetic melts of geological interest, including model basalts and granites. The findings of these studies greatly enhance our understanding of how the Earth initially formed, as well as the physical and chemical behaviour melts. We recently showed free oxygen (O2-) occurs in simple melts and is a critical component for the melting and crystallization of chain and sheet silicates. Our proposed melting model (the first in over 100 years) explains how these minerals melt and crystallize. Furthermore studieson the high frequency region of Raman spectra of glasses and melts show so called "Q species" vibrations have consistent and predictable peaks positions and shapes. Extra peaks observed in the spectra are due to the presence of MBOs (bridging oxygens with an alkali or alkaline earth "attached"). These "species" have not been considered in previous studies on silicate glasses and melts, rendering nearly all previous Raman studies of glasses and melts moot. These MBO vibrations must be considered when fitting spectroscopic data. The current proposal focusses primarily on the structural role of light elements and oxygen in glasses and melts and builds on these findings. I intend to continue investigating the role of O2- in melting reactions with an emphasis on considering the presence of Al. In the melting studies it is clear that melts initially polymerize before depolymerizing and crystallizing. I will investigate why they initially polymerize and if this somehow "stabilizes" the melt. In order to better understand the behaviour of the MBO and Q species in alkali silicate glasses I will investigate select compositions in small alkali increments (0-15 mol% and 30-50 mol% in 1 mol% steps) using Raman spectroscopy in order to elucidate the explicit nature of the relationship between peak positions and shapes with composition.

如果我们要了解地球是如何形成的，岩浆是如何演化的，以及它们在地球表面下的化学和动力学行为，了解在地球深处发现的条件下熔岩或熔体的行为是很重要的。我就是在这种条件下研究这种熔融材料的。我研究了这种液体在环境条件下(使用淬火液体或玻璃)以及极端条件下的结构如何变化。除了拉曼光谱等技术外，我还将主要使用最先进的同步加速器技术。特别是，加拿大光源和其他国际光源的实验光束线被用来研究地质熔岩和岩浆中常见元素(如硅、氧、铝、碱和碱土)周围的环境。与许多国际研究小组合作，我们探索了具有地质意义的简单合成熔体的结构，包括模型玄武岩和花岗岩。这些研究的发现极大地提高了我们对地球最初是如何形成的，以及其物理和化学行为融化的理解。我们最近发现，游离氧(O2-)存在于简单的熔体中，它是链状和片状硅酸盐熔融和结晶的关键成分。我们提出的熔融模型(100多年来第一次)解释了这些矿物是如何熔化和结晶的。此外，对玻璃和熔体拉曼光谱高频区的研究表明，所谓的“Q物种”振动具有一致和可预测的峰位和形状。在光谱中观察到的额外峰是由于MBO(桥接氧与碱或碱土“连接”)的存在。这些“物种”在以前对硅酸盐玻璃和熔体的研究中没有被考虑到，这使得几乎所有以前对玻璃和熔体的拉曼研究都没有意义。在拟合光谱数据时，必须考虑这些MBO振动。目前的提议主要集中在轻元素和氧在玻璃和熔体中的结构作用上，并建立在这些发现的基础上。我打算继续研究O2-在熔融反应中的作用，重点是考虑Al的存在。在熔融研究中，很明显，熔体在解聚和结晶之前首先聚合。我将研究它们最初聚合的原因，以及这是否以某种方式“稳定”了熔体。为了更好地了解碱性硅酸盐玻璃中MBO和Q物种的行为，我将使用拉曼光谱以小的碱增量(0-15mol%和30-50mol%，以1mol%的步长)研究选定的成分，以阐明峰位和形状与成分之间关系的明确性质。