Hydrocarbons in Hydrothermal Vent Fluids: Mineral Catalyzed Metastability of Reduced Carbon Compounds at Elevated Temperatures and Pressures

ABSTRACT: Seyfried (0549457)

Intellectual Merit: This research constrains the mechanism and rate of carbon reduction reactions that abiotically create hydrocarbons in ultramafic seafloor hydrothermal systems using a newly developed hydrothermal flow-through reactor that can measure reactions at the high temperatures and pressures present at hydrothermal vents in the seafloor. Hydrothermal fluids issuing from vents at mid-ocean ridges provide clues critical to our understanding of the origin and evolution of seawater and the oceanic crust through time. Recently, vent fluids from ultramafic-hosted hydrothermal systems have been found to contain abundant and largely unexpected dissolved hydrocarbon species. The experiments allow dissolved gases (H2 and CO2) and other key aqueous species to be added to a reaction cell that contains mineral reactants (catalysts), while rates and processes of hydrocarbon formation are monitored simultaneously from changes in the organic chemistry of the out-flow fluid. Dissolved H2 concentrations and pH (acidity) during the experiments. By performing experiments in both single pass and recirculation modes, organic contamination can be minimized, while carbon adsorption on mineral surfaces can be maximized, facilitating analysis of mineral surfaces by high-resolution surface analytical techniques (XPS, TOF-SIMS, and C-XANES). Mineral catalysts will include a wide range of oxides, sulfides and silicates typical of subseafloor reaction zones in ultramafic-hosted hydrothermal systems, as inferred from reported vent fluid chemistry from these systems. Broader impacts of the work include involvement of undergraduate students in research through the UM/NSF REU Fluids in the Earth. This program provides support for high achieving students from traditionally undergraduate institutions to join in the experimental design and analysis of run products derived from of the proposed investigation. It will also involve development of the proposed hydrothermal flow reactor with in-situ chemical sensors.