Configurational entropy of basaltic melts in Earth’s mantle
Sung Keun Lee, J. L. Mosenfelder, Sun Young Park, A Chim Lee, Paul D. Asimow
Abstract
Significance Proper inference of the seismological and chemical effects of partial melting in Earth’s upper mantle depends on physical properties of interstitial melts at elevated pressure. Silicate liquids display anomalous softening upon compression. This lacks an atomic-scale explanation, partly because studies linking microstructure and physical properties of melts are limited to ambient pressure. Here we studied basaltic glass quenched from high pressure with multinuclear NMR spectroscopy that defines the populations of oxygen species in the glass with sufficient precision to reveal a decrease with pressure in the configurational entropy, which we attribute to entanglement of the melt network upon densification. We explain how the configurational entropy can be used as a tool to explain the anomalous behavior of melts under compression.