C1-C4 hydrocarbons in hydrothermal gases

Twenty-two gas samples from Yellowstone National Park have been analyzed for C₁–C₄ hydrocarbons. All five alkanes in the sequence were identified, two alkenes were identified, and no alkynes were observed. The molecular species present in those samples and the quantitative distribution of those species seems more consistent with an organic orgin (e.g. the thermal degradation of kerogen. etc.) for the hydrothermal gases than with the non-biological production of methane (CO₂ + 4H₂ = CH₄ + 2H₂O) followed by pyrolysis. The latter possibility cannot be completely eliminated, however, since the conditions of reaction are not well known.