Formation of ethane and propane via abiotic reductive conversion of acetic acid in hydrothermal sediments
Min Song, Florence Schubotz, Matthias Y. Kellermann, Christian T. Hansen, Wolfgang Bach, Andreas Teske, Kai‐Uwe Hinrichs
Abstract
Significance Nonmethane, low-molecular-weight hydrocarbons are typically formed in geothermally heated subsurface sediments by cracking of larger precursor molecules. The Guaymas Basin serves as a sedimentary model system for extremely rapid formation of petroleum-like compounds. Here, C 2 to C 5 hydrocarbons are unusually enriched in 13 C, and their isotope pattern is distinct from that found in conventional petroleum systems, suggesting a different pathway for their formation. Using isotope tracer experiments at temperatures and pressures pertinent to hydrothermal conditions, we show that ethane and propane can be formed by reductive conversion of acetic acid, whose carboxylic group was isotopically equilibrated with the dissolved inorganic carbon pool. Our findings reveal a formerly unrecognized formation pathway for two major components in natural gas.