Modeling Magmatic Crystallization and Melting Behavior with Synthetic Water-Salt Fluid Inclusions

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Through this project, a technique of using synthetic H20-KCl fluid inclusions is developed to visually simulate magmatic crystallization and melting behavior for students enrolled in an upper-division petrology course. The technique offers students an interactive, visual learning experience of a geologic process that can never be directly observed. Using synthetic H2O-KCl fluid inclusions of known composition and a heating and cooling stage, students conduct an exercise in which they observe and control: (1) eutectic melting (of ice and sylvite at -10.7 C), (2) liquidus crystallization and melting of ice or sylvite, and (3) final ice or sylvite melting temperatures. Using these data, students construct their own phase diagram of the water-rich portion of the H2O-KCl system and will then explore questions on the (1) the relationship between eutectic and liquidus temperatures and bulk composition and (2) applications of the phase rule at various temperatures. The main advantage of this technique is that all of the important phase changes analogous to magmatic systems (i.e., eutectic and liquidus behavior, crystallization and melting textures) can be visually observed and controlled by the student. Consequently, every space, line and point on a phase diagram will have direct relevance to the student and result in a more meaningful interpretation of phase diagrams and their application to igneous rocks.