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Structure of Glasses of Geological Interest: Applying Spectroscopic Techniques
Published online by Cambridge University Press: 29 November 2013
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Glasses are a minor fraction of Earth materials. However, all igneous processes within the Earth involve a melt phase (magma), and our understanding of the physical and chemical features of these processes is contingent upon an adequate understanding of the melt phase itself. In particular, we wish to relate the behavior of such melts to their composition and structure in the range of physical and chemical conditions in which they occur. The physical conditions of many of these processes are particularly difficult to reproduce in the laboratory, and the ability to predict behavior under such conditions is the goal. From a geological viewpoint, the primary interest is in silicate melts because of the composition of the Earth's lithosphere and mantle. There are significant experimental difficulties in looking at the behavior of silicate melts, so much work has focused on glasses as melt analogues since spectroscopic data on silicate glasses and melts (Figure 1) are similar.
Silicate glasses are also of considerable industrial interest, and early work in the geological field borrowed heavily from materials science. However, the thrust to understand natural magmas led geologically based work into more complex chemical systems (e.g., hydrous alkali-alkaline-earth-aluminosilicates) and their behavior at high pressures.
The structure of glasses is a complex issue, and many different experimental techniques are needed to resolve the details of their structure. Here I will focus on the following techniques: IR (infrared), Raman, Mössbauer, EXAFS (extended x-ray absorption fine structure) and XANES (x-ray absorption near-edge spectroscopy) spectroscopies.
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- Copyright © Materials Research Society 1992
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