A Raman Spectroscopy Study Of The Structure Of Potassium Aluminum Silicate Melt

Magmatic melt not only bring out the embryonic form of rocks and minerals, but also retain much information of the geological evolution, such as the composition, temperature, pressure, density, viscosity, oxygen fugacity and free energy etc. While, a variety of magmatic processes is determined by the physicochemical properties of silicate, therefore, it is need to deeply analyze the structure of silicate melt, in order to explore the nature of magmatism, the origin and evolution of magma, the hyperplasia of earth's crust and other major geological problems.The aim of this article is to research the structure of silicate melt, and the main work are to collect Raman spectroscopy of synthetic aluminum silicate glass series (K1 to K5) at room temperature, and of the melt corresponding components at high temperature in situ, then, set up a series of Raman spectral data of the potassium aluminum silicate glass and melt, with the theoretical analysis and calculation of quantum chemistry, and discuss Raman spectra characterization and the vibration characteristics, and to explore the meaning of its structure , also to do more research the influence of Al and other metal cations on silicate melt.By analyzing, a number of preliminary conclusions as follows : (1) Under high temperature, the melt structure of K₂O-Al₂O-3-SiO₂ have three types of structural units Q₄,Q₃ and Q₂, they are in the dynamic balance (for example, 2Q₃<=>Q₄ +Q₂), and with the rising of the temperature, such reaction will carry out to the right. In high-frequency area, about 1000-1200 cm^-1, the wave number of characteristic peaks has the trend moving to high-frequency area with the temperature increasing, it means Q₃ and Q₂ will change to Q₄. (2) The characteristic peaks in Low-frequency area 400-700 cm^-1, according to the different sample components have different changes: Of these, 16 samples, their Raman spectroscopy rarely changed in the process of heating and cooling, the main result is characteristic peaks of almost every single sample are having the trend of moving to high-frequency area with the temperature increasing; Otherwise, another 8 samples, their Raman spectra had great changes in the heating and cooling process, the characteristic peaks which in 500-700 cm^-1 would be disappeared with the temperature increasing, and the characteristic peaks in 400-500cm^-1 would be a split during the cooling process. On the specific analysis of K13 sample, it is confer that such change is silicon (aluminum) oxygen tetrahedron ring connected by four turned into six-membered ring connected.(3) With the temperatures increasing, the wave number of peaks in 800-1200cm^-1 range had distinctly moved to low-frequency spectrum, and these peaks should be attributed to Si-Onb non-bridge oxygen asymmetric stretching vibration, and those ones which in the 700-800 cm^-1 range would belong to Al-O non-bridge oxygen asymmetric stretching vibration.