Proposal

Serpentinization is a water-rock interaction in which water interacts with Olivine (an ultramafic mineral that is abundant in mid-ocean ridge rocks) to produce serpentine, magnetite and elemental hydrogen (H2). Furthermore, the reaction of H2 and carbon dioxide gas produces methane gas (CH4) at temperature and pressure conditions characteristic of mid-ocean ridge environments. The formation of H2 and CH4 from serpentinization is a potential future energy resource. Additionally, the production of elemental hydrogen and methane gas as mid-ocean ridges and forearcs is believed to be a key abiotic process that may have driven the formation of life on this planet. My project will quantitatively examine the reaction progress and production of H2 and CH4 evolved by serpentinization using inert gold reaction cells capable of examining liquid-vapor-solid systems at pressures (100-500 bar) and temperatures (100-3000C) analgous to mid-ocean ridge and forearc environments.

I propose to spend the 10 week period of the HHMI summer internship at the U.S. Geological Survey facility in Menlo Park, CA studying serpentinization and the rates of elemental hydrogen and methane production at pressure and temperature conditions similar to in mid-ocean ridge and forearc environments. Professor Oze from Bryn Mawr College and Dr. Robert Rosenbaum of USGS will sponsor my participation in the research at Menlo Park. Under the direction of Rosenbaum at USGS, I will set up and run the inert gold cell experiment and collect results on the rates of methane and elemental hydrogen production under the conditions stated above. I plan to continue examining the results from the summer project in order to write my senior thesis in geology in the 2007-2008 academic year.

The results of this project will provide a quantitative understanding of the rates of methane and hydrogen production related to serpentinization that will provide insight into the potential of mid-ocean ridges and forearcs as energy sources and the mechanisms by which organic compounds are produced by abiotic processes.

Summary

Laura Camille Jones
Experimental Geochemistry Lab Intern
Costal and Marine Geology Group
U.S. Geological Survey, Menlo Park, CA
Mentors: Bob Rosenbauer (USGS), Chris Oze (Bryn Mawr College)

Geochemical Processes at Mid-Ocean Ridge and Forearc Environments:
Energy Resources and the Origins of Life

Serpentinization is a geochemical process in which seawater and olivine react to form a variety of minerals including serpentine, magnetite, and elemental hydrogen (H2) at elevated pressures (100-500 bar) and temperatures (100-300°C) in ocean systems. Elemental hydrogen produced during serpentinization is a building block for hydrocarbons including methane (CH4), a potential extractable energy resource and a suspected component of Earth’s primordial soup. Geochemical production of H2 and CH4 has been observed in hydrothermal ocean systems such as forearcs and spreading centers and in Fischer-Tropsch type reactions. At the U.S. Geological Survey (USGS) facility in Menlo Park, I completed two experiments testing the rate and abundance of H2 and CH4 produced during serpentinization by simulating an oceanic hydrothermal environment.

The Water-Rock Interaction Laboratory at the USGS in Menlo Park is equipped to run experiments that model the geochemical systems found in ocean environments and in saline aquifers. Simulating remote ocean and aquifer environments requires subjecting solid and fluid components to elevated pressures and temperatures, thereby, allowing us to monitor reactions that we cannot observe firsthand. The flexible-gold cell hydrothermal autoclaves are unique (there are only two of such labs in the world) because one can take fluid samples from the pressurized cell while the experiment is running. Since these types of experiments need to be maintained at elevated pressures and temperatures for several weeks, sampling during the experiment reveals the progress of chemical reactions occurring inside the pressure cell. We used several analytical approaches including inorganic carbon coulometry, pH meter, ICP-MS, gas chromatography, to assess the multitude of variables controlling the water-rock interactions. Thus, my duties at the USGS included not only setting up, managing, and taking down the hydrothermal autoclaves, but working in several other labs to analyze the fluid and solid samples from the experiments.

Over the course of the summer, we completed two olivine-seawater experiments and collected analytical data to quantitatively examine these two serpentinization scenarios. The reactants in the first experiment are research grade olivine (Fo90) and evolved seawater (KCl, CaCl2, NaCl). The second experiment involved olivine, evolved seawater, solid chromite (a possible catalyst for serpentinization), and sodium bicarbonate. We collected data from analyses preformed during the experimental runs and in batches at the end of the summer. The refractive index, pH, and dissolved carbon were analyzed immediately after extracting each fluid sample from the reaction cell. Aliquots of fluid were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of cations in the fluid and by gas chromatography to determine the abundance of H2 and CH4. Once the experiments reached a steady-state (500-800 hours) we quenched the cells and removed the residual solid to analyze the mineralogy by X-ray diffraction (XRD) and surficial appearance by scanning electron microscopy (SEM). The complete collection of compiled, converted, and compared data from these experiments will be interpreted during the upcoming year and will eventually help explain the chemistry behind serpentinization and its catalysts at 200oC and 300 bar.

Ultimately, this research will expand our understanding of the geochemical production of organic molecules at elevated temperatures and pressures. By this means, we will acquire more information to evaluate the origins of life hypothesis and whether serpentinization is a potential future H2 and CH4 energy resource. Complete analysis of the results from this summer’s project will continue during the upcoming academic year as my senior thesis in geology. The summer research opportunity has yielded abundant data for interpretation and sparked questions that will inform further research on methanogenesis, serpentinization, and water-rock interactions at elevated temperatures and pressures.