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Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
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2011 (English)In: Geochemical Transactions, ISSN 1467-4866, E-ISSN 1467-4866, Vol. 12, no 6Article in journal (Refereed) Published
Abstract [en]

Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures   above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian   CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the   CH4 and H2 formation potential of forsteritic olivine.

The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.

It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze   the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.

Place, publisher, year, edition, pages
2011. Vol. 12, no 6
National Category
Other Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
URN: urn:nbn:se:su:diva-61762DOI: 10.1186/1467-4866-12-6ISI: 000293981700001OAI: oai:DiVA.org:su-61762DiVA: diva2:437445
Available from: 2011-08-29 Created: 2011-08-29 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Low temperature olivine alteration ; an experimental approach
Open this publication in new window or tab >>Low temperature olivine alteration ; an experimental approach
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Water reacting with minerals to alter or dissolve them is a common phenomenon on Earth, leading to a unique chemical composition of the oceans and continents. The continuous circulation of elements and the chemical reactions between them creates the extraordinary environment prevailing on our Earth today and was probably an important requirement for the onset of life on our planet. Olivine is a mineral with the special property of being unstable at atmospheric pressures and temperatures due to its crystal structure and chemical composition. Hydrous alteration of olivine has the capacity to form molecular hydrogen (H2) and hydrated secondary products concurrent with the release of heat. H2 is considered to be crucial for the deep subsurface biosphere and is capable of reducing oxidized carbon species to CH4 and other hydrocarbons through the so-called Sabatier reaction or Fischer-Tropsch Type reactions which are important when studying the large scale CH4 outgassing on Mars or the CH4 seeps coupled to contemporary terrestrial ophiolites.

This thesis investigates the potential abiotic formation of H2 and CH4 at low temperatures and pressures as well as under anoxic conditions but also looks at the potential for sustaining the growth of methanogenic archaea with olivine and water. The results suggest that olivine has the potential to form H2 and fuel the abiotic formation of CH4 at low temperatures and low concentrations of dissolved bicarbonate. At higher bicarbonate concentrations, precipitation of silica and carbonate are suggested to cover the reactive catalytic sites on the olivine surface.

Place, publisher, year, edition, pages
Department of Geological Sciences, Stockholm University, 2011. 88 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 346
Keyword
Olivine alteration, hydrogen, methane, serpentinization
National Category
Natural Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-65451 (URN)978-91-7447-426-8 (ISBN)
Public defence
2012-01-20, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2011-12-21 Created: 2011-12-12 Last updated: 2011-12-19Bibliographically approved
2. Abiotic and biotic methane dynamics in relation to the origin of life
Open this publication in new window or tab >>Abiotic and biotic methane dynamics in relation to the origin of life
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Methane (CH4) plays an important role in regulating Earth’s climate. Its atmospheric concentrations are related to both biotic and abiotic processes. The biotic one can be formed either by chemoautotrophic or heterotrophic pathways by methanogens. Abiotic CH4 formation can occur from several sequential reactions starting with H2 production by serpentinization of Fe-bearing minerals followed by Fischer-Tropsch Type reactions or thermogenic reactions from hydrocarbons. In the presence of suitable electron acceptors, microbial oxidation utilizes CH4 and contributes to regulating its emission.  From the perspectives of astrobiology and Earth climate regulation, this thesis focuses on: (1) Dynamics of CH4 formation and oxidation in lake sediments (Paper I), (2) Constructing an automatic flux chamber to facilitate its emission measurements (Paper II), (3) dynamics of both abiotic and biotic CH4 formation processes related to olivine water interaction in temperature range 30 - 70°C (Paper III and IV).

Paper I showed that potential CH4 oxidation strongly correlated to in situ its formation rates across a wide variety of lake sediments. This means that the oxidation rates could be enhanced in environments having the high formation rates. Thereby, the oxidation would likely be able to keep up with potentially increasing the formation rates, as a result diffusive CH4 release from freshwater sediments might not necessarily increase due to global warming. Paper II presented a new automated approach to assess temporal variability of its aquatic fluxes. Paper III and IV together revealed that H2 can be formed via olivine-water interaction. Abiotic CH4 formation was formed likely by Fischer-Tropsch Type reactions at low inorganic carbon concentration but by thermogenic processes at high inorganic carbon concentration. Paper IV showed that biotic methanogenic metabolism could harvest H2 and produce CH4. The dynamics of these processes seemed strongly affected by carbonate chemistry.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University, 2012. 50 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 348
Keyword
methane, methanogens, methane formation, methane oxidation, lake sediment, olivine, origin of life
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-65895 (URN)978-91-7447-428-2 (ISBN)
Public defence
2012-01-26, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Submitted. Available from: 2012-01-04 Created: 2011-12-15 Last updated: 2011-12-16Bibliographically approved

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