Experimental and Theoretical Studies of Deep Fluids

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EAR-9909583ManningThe liberation and movement of aqueous fluids is important in many high-pressure geologic processes. For example, aqueous solutions are produced during deep-crustal metamorphism, and their migration redistributes geologically important elements in the crust. Similarly, in the mantle, the source regions for diverse magma types show signs of the passage of water-bearing fluids. The transport of substantial quantities of matter arises from the increasing solubilities of most minerals in water-rich solutions with increasing pressure. However, despite abundant evidence that these processes occur in the Earth, systematic study remains limited because the properties of the solutes dissolved in the fluid are poorly known at high pressure.This project involves experimental and theoretical investigations of the chemistry of aqueous fluids and their dissolved constituents at high pressures (5 kb). The approach is to use recent advances in prediction of the thermodynamic properties of aqueous species in deep fluids to compute model phase relations in the presence of fluid in different environments. The predictions are then used to guide experimental studies on solubilities of major rock-forming minerals. In addition, we are determining solubilities of selected trace-element oxides to identify elements that should readily be redistributed during high-pressure fluid flow. Finally, we are studying the effect of Cl and CO2 on fluid transport in deep environments by measuring mineral solubility in aqueous solutions containing these components. When completed, the combined theoretical and experimental studies will provide a quantitative framework for studying the physical and chemical aspects of fluid flow in deep geologic environments.