Spectroscopic studies of geological glasses and melts

点击翻译按钮获取中文摘要

The physical and chemical behaviour of volcanoes depends to a great extend on the properties of the molten material or magma beneath the volcano. Magmas are mixtures of silicate melt, crystals and dissolved gases. The melt phase plays an important role because its structure influences properties such as rheology, diffusion and eruptive style. However, in situ studies of melts are technically difficult and it is easier to study the quenched melt or glass. Geological research into the structure of melts and glasses has been ongoing since the 30s and continues, with large research groups in the USA, Japan, and Europe actively in this area. In general, simple melt compositions are prepared and quenched to glass. The glasses produced have properties closely analogous to the corresponding melt. These glasses are then probed by sophisticated instrumentation and analysis of the spectroscopic data provides key information with which to interpret the speciation, structure and coordination of the glasses. By establishing how composition affects the structural properties of the synthetic glasses it is possible to establish a basis upon which to develop structural models of more complex natural systems. Here I propose to study the influence of composition on 1) the coordination of elements such as O, B, Al, Fe and Ti, 2) the influence of different alkalis (Li, Na, K, Rb) on the extended glass structure, 3) perform in-situ studies on melts and attempt to observe structural changes with changing temperature and, 4) the suitability of using synthetic glasses to host nuclear waste products. These projects address specific well-defined areas of current interest in geological glass/melt research. A significant portion of the research will be carried out at the Canadian Light Source (CLS), the recently opened national synchrotron radiation facility in Saskatoon. I have extensive experience with the instrumentation and techniques that will be employed and have developed an international reputation in their application to glass/melt research. In addition, some of the proposed research is collaborative with colleagues at IPGP (Paris) and IMPMC (Paris) and will utilise instrumentation and synchrotron facilities outside of Canada.