| Aqueous organic compounds are ubiquitous in geologic environments over great ranges of conditions. Their formation, transformation and composition are influenced by the nature of water/rock reactions in the rocks which host them. In addition, the existence of organic material can have a strong effect on the oxidation state, pH and the bulk composition prevailing in geologic environments. Understanding the role that aqueous organic compounds play in geologic settings is aided by quantitative geochemical models that explicitly take into account the behavior of organic material at the temperatures and pressures of interest. In order to construct and properly constrain such models, I have conducted experiments and designed estimation methods that provide values of the thermodynamic properties of aqueous organic compounds at high temperatures. The experimental measurements reported here represent an increase by 50% the number of aqueous organic compounds for which high-temperature partial molar volume are available. I have combined these data with the revised Helgeson-Kirkham-Flowers equation of state for aqueous species which is widely used in geochemical models of the simultaneous reactions of minerals, gases, and aqueous solutions. Changes in the equation of state for aqueous nonelectrolytes and aqueous organic compounds are proposed which improve the accuracy of estimates of the partial molal volume and heat capacity of these species, and data and parameters are provided for 138 species for which calculations were not previously possible.;Data of this type are used in reaction path models to evaluate the potential for the formation of organic compounds during aqueous alteration of the parent bodies of carbonaceous chondrite meteorites. These models indicate that the extensive suite of soluble organic compounds extracted from the meteorites formed during the episode(s) of aqueous alteration responsible for the hydrated phyllosilicates, sulfides, carbonates and oxides also observed. The results of these calculations suggest that organic compounds can be synthesized in environments where there is a source of carbon, liquid water, and heat, and that the processes leading to the formation of organic material are strongly controlled by the interaction of the fluids with the host rocks. |
