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