Geochemical constraints on the origin of organic compounds in hydrothermal systems

Research output: Contribution to journalArticle

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Abstract

It is proposed that abiotic synthesis of organic compounds occurs in metastable states. These states are permitted by kinetic barriers which inhibit the approach to stable equilibrium in the C-H-O-N system. Evidence for metastable equilibrium among organic compounds in sedimentary basins is reviewed, and further evidence is elucidated from hydrous pyrolysis experiments reported in the literature. This analysis shows that at hydrothermal conditions, organic compounds are formed or destroyed primarily through oxidation/reduction reactions, and that the role of temperature is to lower the kinetic barriers to these reactions. These lines of evidence allow the development of a scenario in which abiotic synthesis can occur at hydrothermal conditions through the reduction of CO2 and N2. This scenario can be tested quantitatively with distribution of species calculations as functions of temperature, pressure, hydrogen fugacity (fH2) and initial composition. One example of such a test is given for an early, sudden outgassing of the Earth, in which CO2, H2O, and N2 are transported from the mantle to the atmosphere by hydrothermal solutions. Activities of metastable aqueous organic species which form as a consequence of this process are evaluated at conditions appropriate for seafloor hydrothermal systems, and are found to maximize at about 200 °C and between the oxidation states set by two mineral assemblages common in the oceanic crust.

Original languageEnglish (US)
Pages (from-to)331-367
Number of pages37
JournalOrigins of Life and Evolution of the Biosphere
Volume20
Issue number3-4
DOIs
StatePublished - May 1990
Externally publishedYes

Fingerprint

hydrothermal systems
hydrothermal system
organic compounds
organic compound
Synthetic Chemistry Techniques
Temperature
Atmosphere
oxidation-reduction reactions
Oxidation-Reduction
Minerals
kinetics
Hydrogen
redox reactions
synthesis
outgassing
pyrolysis
fugacity
Pressure
metastable state
sedimentary basin

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Agricultural and Biological Sciences (miscellaneous)

Cite this

Geochemical constraints on the origin of organic compounds in hydrothermal systems. / Shock, Everett.

In: Origins of Life and Evolution of the Biosphere, Vol. 20, No. 3-4, 05.1990, p. 331-367.

Research output: Contribution to journalArticle

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