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Low temperature olivine alteration ; an experimental approach
Stockholm University, Faculty of Science, Department of Geological Sciences. (geochemistry)
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 [en]
Olivine alteration, hydrogen, methane, serpentinization
National Category
Natural Sciences
Research subject
Geochemistry
Identifiers
URN: urn:nbn:se:su:diva-65451ISBN: 978-91-7447-426-8 (print)OAI: oai:DiVA.org:su-65451DiVA: diva2:463919
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
List of papers
1. Reduction of nitrogen compounds i oceanic basemet and its implications for HCN formation and abiotic organic synthesis
Open this publication in new window or tab >>Reduction of nitrogen compounds i oceanic basemet and its implications for HCN formation and abiotic organic synthesis
2009 (English)In: Geochemical Transactions, ISSN 1467-4866, E-ISSN 1467-4866, Vol. 10, no 9Article in journal (Refereed) Published
Abstract [en]

Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur.

Place, publisher, year, edition, pages
BioMed Central Ltd, 2009
Keyword
astrobiology, nitrogen reduction, hydrogen cyanide, origin of life, subduction zones, abiotic organic synthesis
National Category
Other Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-31641 (URN)10.1186/1467-4866-10-9 (DOI)000271451900001 ()
Projects
Hydrothermal Organic Geochemistry
Available from: 2009-11-23 Created: 2009-11-23 Last updated: 2017-12-12Bibliographically approved
2. Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C
Open this publication in new window or tab >>Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C
Show others...
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.

National Category
Other Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-61762 (URN)10.1186/1467-4866-12-6 (DOI)000293981700001 ()
Available from: 2011-08-29 Created: 2011-08-29 Last updated: 2017-12-08Bibliographically approved
3. The potential for abiotic methane formation fueled by olivine dissolution
Open this publication in new window or tab >>The potential for abiotic methane formation fueled by olivine dissolution
(English)In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908Article in journal (Refereed) Submitted
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-65502 (URN)
Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2017-12-08Bibliographically approved
4. The effect of DIC on low temperature olivine alteration and H2 formation
Open this publication in new window or tab >>The effect of DIC on low temperature olivine alteration and H2 formation
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-65501 (URN)
Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2011-12-12Bibliographically approved

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