Collaborative Research: Incorporating Temperature-dependent Physical Properties into Numerical Models of Magmatic and Related Hydrothermal Systems

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Most geologic processes within the interior of the Earth are driven by heat transfer. These processes include magma generation, volcanism, geothermal systems, and generation of several types of ore deposits. Current mathematical and computer models used to study these processes generally assume fixed values for several fundamental properties of rocks such as heat capacity, that is the ability of rocks to hold heat, thermal diffusivity, that is the ability of rocks to transfer heat, and the amount of heat that is necessary to melt rocks. The values of these properties for many types of rocks, in particular how they vary with temperature, are still poorly known, and one aspect of the research focuses on experimental measurements in the laboratory. The new values will then be applied to modeling the growth of well-characterized magma bodies within the Earth's crust by continued or episodic magma injection, and how growth and crystallization of these plutons drives metamorphism of the surrounding rocks and geothermal systems. The project will provide an opportunity to train students and young scientists in research that will have laboratory, computational and field components. The ability to view complex natural processes from multiple perspectives is key to the training of successful geoscientists.The need for improved data on temperature-dependent properties of rocks that can be incorporated into integrated thermal models is motivated by recent advances in understanding of how granitic plutons are constructed, and because intrusion-induced metamorphic and geothermal systems generally have longer durations than simple conductive and convective thermal models typically predict. There has been a paradigm shift from viewing plutons as large volumes of magmas that are emplaced in a single pulse as diapirs to viewing plutons as bodies that grow over extended periods, from tens of thousands of years to millions of years. Prolonged injection of magma has consequences for crystallization histories of plutons and duration of metamorphic-geothermal systems, all of which are controlled by heat transfer. The aim of the project is to determine temperature-dependent properties of minerals and rocks and to develop integrated numerical models for magmatic-metamorphic-geothermal systems. The modeling will be field-tested by examination of the growth of the Harney Peak Granite pluton in the Black Hills and how its growth influenced its thermal aureole. The laboratory data will be useful to workers who study processes in many other geologic settings.