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3.5 Melt Physics and Chemistry

The presence of a melt phase, in virtually any amount, has a profound influence on many of the physical properties and dynamic processes encompassed by the solid Earth. An understanding of melt physics and chemistry through laboratory studies enables us to shed light on topics ranging from processes in the deep Earth such as core viscosity and magma transport in the mantle to shallower depths concerning volcanology and economic geology. The following contributions exemplify the complex dependence of many melt properties such as viscosity, volume and entropy on composition, temperature and pressure. In addition, examining the structure of melts by a variety of spectroscopic methods provides an important link to their rheological and thermodynamic properties. We have continued to reach new goals in the study of melts at high pressure using state-of-the-art techniques designed to track melt dynamics that are too fast to be observed by conventional methods. Recent efforts have also been aimed at examining more complex chemistries such as halide substitution in silicate melts and natural volcanic products hydrated in the laboratory. We have also turned our attention towards some of the more subtle anomalies in simpler systems, including the observed non-linearity in the thermal expansion of diopside liquid over a broad temperature range and the complex viscous behavior of aluminosilicate melts over small compositional increments along lines of equal silica content. These studies provide valuable tests to some of the more fundamental models of silicate melt structure and dynamics.

Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Deutschland
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