Get access

New insight into the contributions of thermogenic processes and biogenic sources to the generation of organic compounds in hydrothermal fluids

Authors

  • C. KONN,

    1. 1 Département Geosciences Marines, Ifremer C/Brest, Plouzané, France
      2 Département MCMF, Institut Néel, Grenoble, France
      3 UMR6197 LM2E, Ifremer C/Brest, Plouzané, France
      4Department of Geosciences, Geochemistry Section, Stockholm University, Stockholm, Sweden
    Search for more papers by this author
  • 1 D. TESTEMALE,

    1. 1 Département Geosciences Marines, Ifremer C/Brest, Plouzané, France
      2 Département MCMF, Institut Néel, Grenoble, France
      3 UMR6197 LM2E, Ifremer C/Brest, Plouzané, France
      4Department of Geosciences, Geochemistry Section, Stockholm University, Stockholm, Sweden
    Search for more papers by this author
  • 2 J. QUERELLOU,

    1. 1 Département Geosciences Marines, Ifremer C/Brest, Plouzané, France
      2 Département MCMF, Institut Néel, Grenoble, France
      3 UMR6197 LM2E, Ifremer C/Brest, Plouzané, France
      4Department of Geosciences, Geochemistry Section, Stockholm University, Stockholm, Sweden
    Search for more papers by this author
  • 3 N. G. HOLM,

    1. 1 Département Geosciences Marines, Ifremer C/Brest, Plouzané, France
      2 Département MCMF, Institut Néel, Grenoble, France
      3 UMR6197 LM2E, Ifremer C/Brest, Plouzané, France
      4Department of Geosciences, Geochemistry Section, Stockholm University, Stockholm, Sweden
    Search for more papers by this author
  • and 4 J. L. CHARLOU 1

    1. 1 Département Geosciences Marines, Ifremer C/Brest, Plouzané, France
      2 Département MCMF, Institut Néel, Grenoble, France
      3 UMR6197 LM2E, Ifremer C/Brest, Plouzané, France
      4Department of Geosciences, Geochemistry Section, Stockholm University, Stockholm, Sweden
    Search for more papers by this author

Corresponding author: C. Konn. Tel.: +33 (0)298 224 264; fax: +33 (0)298 224 570; e-mail: cecile.konn@ifremer.fr

Abstract

Experiments on hydrothermal degradation of Pyrococcus abyssi biomass were conducted at elevated pressure (40 MPa) over a 200–450 °C temperature range in sapphire reaction cells. Few organic compounds could be detected in the 200 °C experiment. This lack was attributed to an incomplete degradation of P. abyssi cells. On the contrary, a wide range of soluble organic molecules were generated at temperatures ≥350 °C including toluene, styrene, C8–C16 alkyl-benzenes, naphthalene, C11–C16 alkyl-naphthalenes, even carbon number C12–C18 polycyclic aromatic hydrocarbons, C15–C18 alkyl-phenanthrenes and C8:0–C16:0 n-carboxylic acids. The effect of time on the final organic composition of the degraded P. abyssi solutions at 350 °C was also investigated. For that purpose the biomass was exposed for 10, 20, 60, 90, 270 and 720 min at 350 °C. We observed a similar effect of temperature and time on the chemical diversity obtained. In addition, temperature and time increased the degree of alkylation of alkyl-benzenes. This study offers additional evidence that a portion of the aliphatic hydrocarbons present in the fluids from the Rainbow ultramafic-hosted hydrothermal field may be abiogenic whereas a portion of the aromatic hydrocarbons and n-carboxylic acids may have a biogenic origin. We suggest that aromatic hydrocarbons and linear fatty acids at the Rainbow site may be derived directly from thermogenic alteration of material from the sub-seafloor biosphere. Yet we infer that the formation and dissolution of carboxylic acids in hydrothermal fluids may be controlled by other processes than in our experiments.

Ancillary