THE STRUCTURE OF SILICATE MELTS: A GLASS PERSPECTIVE
2005; Mineralogical Association of Canada; Volume: 43; Issue: 6 Linguagem: Inglês
10.2113/gscanmin.43.6.1921
ISSN1499-1276
Autores Tópico(s)Geological and Geochemical Analysis
ResumoGlasses are widely used as analogues for the study of silicate melts.Although they are solid materials, their structure is inherently complex and diffi cult to study.However, progress has been made in elucidating this structure, its relationship to composition, and how it behaves at high temperatures and pressures.Recent research has brought to light some new fi ndings with important implications for natural melts.These include the observation that the structure is dependent upon the type and size of alkali or alkaline-earth cations incorporated into the glass network, with Li behaving very differently than other alkali cations.In addition, the presence of more than one type of alkali cation can cause non-linear physical behavior.Elements such as Al, Ti and Fe, which play important roles in petrological phenomena, can exhibit coordination environments (e.g., 5-fold) or polyhedral arrangements (e.g., triclusters) that are not common in crystalline phases.Furthermore, polyamorphic phase-transitions may occur at high temperature and pressures; the application of new theoretical models like mean fi eld-constraint hypothesis suggests that several glass phenomena, and probably melt phenomena as well, may be related to stress-rigid to fl oppy transitions.The state of understanding of glass structure, although still rudimentary relative to crystalline materials, has grown exponentially over the last few decades, often with geological researchers at the forefront.
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