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Biogenic or abiogenic organics in hydrothermal fluids from ultramafic-hosted vents of the Mid Atlantic Ridge: The first step to the origin of life?
A330
Goldschmidt Conference Abstracts 2006
Biogenic or abiogenic organics in hydrothermal fluids from ultramafic-hosted vents of the Mid Atlantic Ridge: The first step to the origin of life? C. KONN1,2, N.G. HOLM1, J.L. CHARLOU2, J.P. DONVAL2, F. DEHAIRS3, S. BOUILLON3 1
Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden ([email protected]) 2 De´partement Geosciences Marines, DRO/GM-IFREMER C/Brest, Plouzane´, France 3 Department of Chemistry, Vrije Universiteit Brussel, Brussels, Belgium The process of serpentinisation at slow spreading ridges is due to the circulation of seawater in outcropping mantle rocks. Association of high CH4- and H2-concentrations in the water column with the serpentinisation of ultramafic rocks is now well agreed upon. The likely abiogenic origin of the methane has been supported by the isotope-ratio values. This has lead to the idea of abiogenic formation of larger organic compounds such as hydrocarbons or key molecules for the origin of life issue. Hydrothermal fluids from the MAR have been collected at different hot vent sites presenting highly different features (high/low pH, ultramafic/basaltic petrology, etc.). SPME (Solid Phase Micro Extraction)-GC-MS and SBSE (Stir Bar Sorptive Extraction)-TD (ThermalDesorption)-GC-MS analyses on the extracts have revealed the presence of organic compounds at trace level in the fluids. Mainly hydrocarbons, but also oxygen-, nitrogen-, sulfur- and phosphorus compounds were clearly identified by comparison of recorded mass spectra with library data. In order to establish whether the compounds were biogenic or abiogenic carbon isotopic ratio measurements have been performed at the Vrije Universiteit Brussel. Despite a lack of resolution on the major part of the spectra, quite a few peaks were separated well enough to get reliable d13C values. These suggest a mix of abiogenic and biogenic carbon for a great majority of the molecules. However, preliminary results show that some of the compounds may have been generated from mineral chemical reactions. We propose that catalytic processes may be involved in the reaction pathway for the formation of organics from thermogenic carbon. Outline for the future is to better separate the chromatographic peaks in order to get more accurate d13C data. This work is carried out partly within the MOMARnet (MOnitoring deep sea floor hydrothermal environments on the Mid-Atlantic Ridge: A Marie Curie Research Training NETwork’) framework. doi:10.1016/j.gca.2006.06.666
Identification of magnetotactic bacteria and their fossils with ferromagnetic resonance R.E. KOPP1, C.Z. NASH1, B.P. WEISS2, A.C. MALOOF2,3, A. KOBAYASHI4, H. VALI5, J.L. KIRSCHVINK1 1
Division of Geological and Planetary Sciences, Caltech, Pasadena, CA 91125, USA ([email protected]) 2 Department of Earth, Atmospheric, and Planetary Scicnes, MIT, Cambridge, MA 02139, USA ([email protected]) 3 Department of Geosciences, Princeton University, Princeton, NJ 08544, USA ([email protected]) 4 National Institute of Advanced Industrial Science and Technology, Osaka, Japan ([email protected]) 5 Dept. of Earth & Planetary Sciences, McGill Univ., Montre´al, Que., Canada H3A 2A7 ([email protected]) Whereas most biomineralizing bacteria produce minerals extracellularly as a metabolic byproduct, with crystal properties controlled abiotically, magnetotactic bacteria produce intracellular magnetic crystals (of either magnetite or greigite) under biological control within membrane-bounded organelles (magnetosomes). Because the bacteria use the crystals to orient themselves, natural selection has acted to optimize the amount of magnetic moment produced for the number of iron atoms used. Magnetosome crystals thus typically have an array of distinctive physical properties. In particular, their size and shape fall within narrow distributions. The crystals are almost always single domain and frequently elongate. In addition, they are almost always arranged in chains. Classical rock magnetic techniques allow the identification of single domain particles and some assessment of their size distribution. Ferromagnetic resonance spectroscopy (FMR) allows assessment not only of the size and shape distribution, but also of crystal elongation and chain arrangement. Our measurements of the magnetotactic bacterial strains MV-1 (which produces chains of elongate magnetite crystals) and AMB1 (which produces chains of equidimensional magnetite crystals), as well as of AMB-1 mutants that produce isolated equidimensional and elongate crystals, allow identification of the contributions of elongation and chain structure to the ferromagnetic resonance spectra of magnetotactic bacteria. All magnetotactic bacteria measured so far fall in a distinct region of the space defined by absorption peak position, width, and asymmetry. Lysed bacteria can produce spectra that resemble those of sediments in which magnetization is largely carried by diagnetically altered magnetosome crystals. Measurements of modern and ancient sediments indicate that FMR can distinguish sediments with magnetic mineralogy dominated by biogenic magnetite from those with magnetic mineralogy dominated by detital input. doi:10.1016/j.gca.2006.06.667
Goldschmidt Conference Abstracts 2006
Biogenic or abiogenic organics in hydrothermal fluids from ultramafic-hosted vents of the Mid Atlantic Ridge: The first step to the origin of life? C. KONN1,2, N.G. HOLM1, J.L. CHARLOU2, J.P. DONVAL2, F. DEHAIRS3, S. BOUILLON3 1
Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden ([email protected]) 2 De´partement Geosciences Marines, DRO/GM-IFREMER C/Brest, Plouzane´, France 3 Department of Chemistry, Vrije Universiteit Brussel, Brussels, Belgium The process of serpentinisation at slow spreading ridges is due to the circulation of seawater in outcropping mantle rocks. Association of high CH4- and H2-concentrations in the water column with the serpentinisation of ultramafic rocks is now well agreed upon. The likely abiogenic origin of the methane has been supported by the isotope-ratio values. This has lead to the idea of abiogenic formation of larger organic compounds such as hydrocarbons or key molecules for the origin of life issue. Hydrothermal fluids from the MAR have been collected at different hot vent sites presenting highly different features (high/low pH, ultramafic/basaltic petrology, etc.). SPME (Solid Phase Micro Extraction)-GC-MS and SBSE (Stir Bar Sorptive Extraction)-TD (ThermalDesorption)-GC-MS analyses on the extracts have revealed the presence of organic compounds at trace level in the fluids. Mainly hydrocarbons, but also oxygen-, nitrogen-, sulfur- and phosphorus compounds were clearly identified by comparison of recorded mass spectra with library data. In order to establish whether the compounds were biogenic or abiogenic carbon isotopic ratio measurements have been performed at the Vrije Universiteit Brussel. Despite a lack of resolution on the major part of the spectra, quite a few peaks were separated well enough to get reliable d13C values. These suggest a mix of abiogenic and biogenic carbon for a great majority of the molecules. However, preliminary results show that some of the compounds may have been generated from mineral chemical reactions. We propose that catalytic processes may be involved in the reaction pathway for the formation of organics from thermogenic carbon. Outline for the future is to better separate the chromatographic peaks in order to get more accurate d13C data. This work is carried out partly within the MOMARnet (MOnitoring deep sea floor hydrothermal environments on the Mid-Atlantic Ridge: A Marie Curie Research Training NETwork’) framework. doi:10.1016/j.gca.2006.06.666
Identification of magnetotactic bacteria and their fossils with ferromagnetic resonance R.E. KOPP1, C.Z. NASH1, B.P. WEISS2, A.C. MALOOF2,3, A. KOBAYASHI4, H. VALI5, J.L. KIRSCHVINK1 1
Division of Geological and Planetary Sciences, Caltech, Pasadena, CA 91125, USA ([email protected]) 2 Department of Earth, Atmospheric, and Planetary Scicnes, MIT, Cambridge, MA 02139, USA ([email protected]) 3 Department of Geosciences, Princeton University, Princeton, NJ 08544, USA ([email protected]) 4 National Institute of Advanced Industrial Science and Technology, Osaka, Japan ([email protected]) 5 Dept. of Earth & Planetary Sciences, McGill Univ., Montre´al, Que., Canada H3A 2A7 ([email protected]) Whereas most biomineralizing bacteria produce minerals extracellularly as a metabolic byproduct, with crystal properties controlled abiotically, magnetotactic bacteria produce intracellular magnetic crystals (of either magnetite or greigite) under biological control within membrane-bounded organelles (magnetosomes). Because the bacteria use the crystals to orient themselves, natural selection has acted to optimize the amount of magnetic moment produced for the number of iron atoms used. Magnetosome crystals thus typically have an array of distinctive physical properties. In particular, their size and shape fall within narrow distributions. The crystals are almost always single domain and frequently elongate. In addition, they are almost always arranged in chains. Classical rock magnetic techniques allow the identification of single domain particles and some assessment of their size distribution. Ferromagnetic resonance spectroscopy (FMR) allows assessment not only of the size and shape distribution, but also of crystal elongation and chain arrangement. Our measurements of the magnetotactic bacterial strains MV-1 (which produces chains of elongate magnetite crystals) and AMB1 (which produces chains of equidimensional magnetite crystals), as well as of AMB-1 mutants that produce isolated equidimensional and elongate crystals, allow identification of the contributions of elongation and chain structure to the ferromagnetic resonance spectra of magnetotactic bacteria. All magnetotactic bacteria measured so far fall in a distinct region of the space defined by absorption peak position, width, and asymmetry. Lysed bacteria can produce spectra that resemble those of sediments in which magnetization is largely carried by diagnetically altered magnetosome crystals. Measurements of modern and ancient sediments indicate that FMR can distinguish sediments with magnetic mineralogy dominated by biogenic magnetite from those with magnetic mineralogy dominated by detital input. doi:10.1016/j.gca.2006.06.667