C-Isotopensystematik und 13C-D Gehalt von n-Alkanen in vulkanisch-hydrothermalen Entgasungen

• Antragsteller: Professor Dr. Jens Fiebig
• Fachliche Zuordnung: Mineralogie, Petrologie und Geochemie
• Förderung: Förderung von 2013 bis 2016
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 237608878

Short chain n-alkanes such as methane, ethane and propane play a significant role as energy resources, but at the same time hold the potential to trigger abrupt climate change and even contribute to photochemical pollution and ozone production. Therefore, a thorough understanding of their biological and geological sources and sinks is of great societal importance. In this respect it is important to be able to distinct between biogenic and abiogenic hydrocarbon emissions. One of the criteria for hydrocarbon classification is the carbon isotope relationship between the n-alkanes. N-alkanes deriving from an abiogenic polymerization of methane have been proposed to exhibit a small carbon isotope fractionation between methane and ethane, while the fractionation is negligibly small during the addition of further methane monomers. The carbon isotopic composition of n-alkanes higher than ethane, therefore, progressively converges towards that of the methane again with increasing chain length. We request funding for the setup of an analytical technique that will allow us to analyze the carbon isotopic composition of n-alkanes contained in ppb to sub-ppb amounts in volcanic-hydrothermal emissions. In a pilot study, this technique will then be applied to study the carbon isotope relationships between methane, ethane, propane and n-butane from selected emissions. Methane in these discharges has been ascribed an abiogenic origin. A few of these hydrocarbon samples will also be analyzed for their clumped isotopic composition. The new isotope information thus received will allow us to constrain the mechanism(s) of hydrocarbon formation in volcanic-hydrothermal systems and to establish criteria for biogenic vs abiogenic hydrocarbon classification.

• DFG-Verfahren: Sachbeihilfen
• Internationaler Bezug: Italien, USA
• Beteiligte Personen: Dr. Walter d' Alessandro; Professor John Eiler, Ph.D.; Dr. Fausto Grassa; Professor Dr. Wilhelm Püttmann; Professor Dr. Franco Tassi; Professor Dr. Orlando Vaselli