Silicon Coordination and Speciation Changes in a Silicate Liquid at High Pressures
Authors:
- 1 September 1989
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 245 (4921) , 962-964
Abstract
Coordination and local geometry around Si cations in silicate liquids are of primary importance in controlling the chemical and physical properties of magmas. Pressure-induced changes from fourfold to sixfold coordination of Si in silicate glass samples quenched from liquids has been detected with 29 Si magic-angle spinning nuclear magnetic resonance spectrometry. Samples of Na 2 Si 2 O 5 glass quenched from 8 gigapascals and 1500°C contained about 1.5 percent octahedral Si, which was demonstrably part of a homogeneous, amorphous phase. The dominant tetrahedral Si speciation in these glasses became disproportionated to a more random distribution of bridging and nonbridging oxygens with increasing pressure.Keywords
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