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Project Progress

The focus in this funding year has been on the interaction of formate with submarine hydrothermal systems. This work is an extension of the MS thesis of Robin Penfield, which was completed in YR3, and addresses the primary goal set in YR 3. To conduct the hydrothermal experiments, we designed, developed, and tested a new Ti hydrothermal reaction vessel. Because the fate of formate involves a complex set of reactions and several intermediate products at low concentrations, it was imperative to conduct control experiments to evaluate contamination of the experimental solution with organics derived via leaching of Teflon and PEEK o-rings and tubing, as well as catalysis of formate decomposition by the walls of the vessel. On the basis of a lengthy set of control experiments, we have now arrived at the ideal configuration of the experimental setup and have started a first set of experiments evaluating the interaction between Mid-Ocean Ridge Basalts (MORB) and formate. The first results show that formate is relatively stable in the presence of basalt.

Parallel to our work on formate stability in hydrothermal systems, we have been working on the interaction of dinitrogen with seawater-basalt systems, a goal set in Year 3. Using a combination of geochemical modeling as well as evaluating existing gas composition data for submarine vent solutions, we have placed constraints on the origin and fate of dinitrogen in these systems and have developed a hypothesis of how the origin of dinitrogen in vent solution can be tested using Ar isotopes. As part of this work, we have now started an experimental program to study the sequestration of ammonia in MORB and serpentinite. The rational for this study is that ammonia formation may proceed in seawater-basalt systems but the ammonia does not discharge from the vents as most of it is sequestered in basalt.