This study will test several hypotheses about organic transformations through independent thermodynamic models of reversible and irreversible processes in comples water/mineral/organic systems. The hypotheses to be tested include: (1) The transformation of solid and liquid organic compounds in heated sediments near ridge hydrothermal systems can be interpreted in terms of aqueous alteration, hydrolytic disporportionation, and the approach towar metastable equilibria using models based on irreversible thermodynamics. (2) Marine dissolved organic matter is altered into characteristic suites of simple organic solutes when heated in submarine hydrothermal systems. These compounds are driven toward metastable states at high temperature, but provide support for heterotrophic hyperthermophiles when vent fluids mix with seawater. (3) Owing to coupled electron-transfer processes, there are reaction pathways involving inorganic and organic sulfur compounds that expedite the transformations documented in hydrothermal organic compounes.
