The structure of silicate magmas, melts and glasses

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以下的化学和动力学行为，那么了解在地球深处发现的熔融岩石或熔体的行为是很重要的。我正在这些条件下研究这些熔融材料。我研究这些液体的结构在环境条件下（使用淬火液体或玻璃）以及极端条件下是如何变化的。除了拉曼光谱等技术外，我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用于研究地质熔体和岩浆中常见元素（如Si， O, Al，碱和碱土）周围的环境。在与一些国际研究小组的合作下，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。这些研究的发现大大提高了我们对地球最初形成的理解，以及地球融化的物理和化学行为。我们最近发现游离氧（O2-）存在于简单熔体中，是链状和片状硅酸盐熔化和结晶的关键成分。我们提出的熔融模型（100多年来的第一个）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的高频区域的研究表明，所谓的“Q种”振动具有一致和可预测的峰值位置和形状。在光谱中观察到的额外峰是由于mbo（桥接氧与碱或碱土“附着”）的存在。这些“物种”在以前的硅酸盐玻璃和熔体的研究中没有被考虑，使得几乎所有以前的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。目前的建议主要集中在轻元素和氧在玻璃和熔体中的结构作用，并建立在这些发现的基础上。我打算继续研究O2-在熔化反应中的作用，重点考虑Al的存在。在熔化研究中，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。为了更好地理解MBO和Q物质在碱硅酸盐玻璃中的行为，我将使用拉曼光谱研究在小的碱增量（0-15 mol%和30-50 mol%在1 mol%的步骤）中选择的成分，以阐明峰位置和形状与成分之间关系的明确性质。*****

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 studies on 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.*****