My main research interests involve assessment of geochemical processes responsible for the chemical evolution of aqueous fluids in and on the Earth. Thus, I study mineral dissolution and precipitation processes together with the reaction rates of minerals in complex aqueous fluids at a wide range of temperatures and pressures. The approach I emphasize in the course of these studies typically involves experimental and theoretical modeling, in conjunction with analysis of field data from natural hydrologic and hydrothermal systems. Although initially focused on inorganic chemical systems, recent experiments have been directed towards organic systems involving microbial metabolism in deep-sea vents and the role of mineral catalysis on hydrocarbon formation in hydrothermal vent fluids. Hydrocarbons synthesized in the hydrothermal experiments not only relate well to modern geochemical and biological systems at mid-ocean ridges, but may also provide clues for the mechanism of formation of even more complex organic molecules (amino acids, lipids) in ancient, pre-biotic hydrothermal systems on Earth and elsewhere.
Moreover, the aqueous geochemistry group at the University of Minnesota has played an important role in the development of new experimental hydrothermal techniques that have resulted in novel chemical sensors to investigate the in-situ chemistry of aqueous fluids at elevated temperatures and pressures. Although initially designed to determine the distribution of aqueous species in complex fluids where theoretical models are lacking or inaccurate, it soon became clear that the lab-based sensors could be reconfigured for seafloor hydrothermal applications. Thus, in-situ sensors for measurement and monitoring dissolved components in high-temperature hydrothermal fluids were successfully developed and deployed in vent fluid systems on the Juan de Fuca Ridge (N.E. Pacific)(1999, 2005), East Pacific Rise, 9-10°N (2002, 2004) and the Galapagos Rift (2005) using DSRV ALVIN. Indeed, these deployments have provided the first simultaneous in-situ data for pH, dissolved hydrogen and dissolved hydrogen sulfide, species critical to understanding geochemical reactions at depth in the ocean crust, as well as biogeochemical processes in the near-vent environment. Future research cruises and ROV investigations are planned for longer term monitoring studies of vent fluid chemistry at mid-ocean ridges and at hydrothermal vents on the floor of Yellowstone Lake, Wyoming. An overarching goal of these studies involves exploration of the interplay between chemical and physical processes that influence the origin and evolution of hydrothermal vent fluids and coexisting biologic communities in space and time.