ToF-SIMS analysis of hopanes and steranes in single oil-bearing fluid inclusions
2009 (English)In: Geochimica et Cosmochimica Acta, vol 73, A1223, 2009Conference paper (Other academic)
Hopanes and steranes are key biomarkers when tracking early evolution of life on Earth. A potential contamination-free source of such biomarkers is oil-bearing fluid inclusions as the oil has been secluded from the environment since the the inclusion was trapped. Using extraction-based techniques (GC/MS, LC/MS), it is, however, problematic to assign the extracted biomarkers to specific inclusions, due to the presence of often several generations of inclusions. As yet, it has not been possible to selectively analyse syngenetic inclusions for their biomarker content, because of their small size (5-30 µm in diameter). Here we present an approach employing time-of-flight secondary ion mass spectrometry (ToF-SIMS) to open and directly analyse the picoliter content of individual oil inclusions in petrographic thin sections of the target rocks.
A number of oil-bearing inclusions (20-30 µm in diameter) from hydrothermal veins in the Siljan impact structure, Sweden, were analysed. The approach consisted of the following steps; i) localization of a suitable inclusion in a thin section using optical microscopy, ii) opening of the inclusion by ion etching with a C60+ sputter gun inside the ToF-SIMS instrument while recording in real-time the opening of the inclusion and, iii) analysis of the exposed inclusion contents with ToF-SIMS. ToF-SIMS spectra from the analysed inclusions showed a large number of organic peaks that are characteristic for crude oils, including all major diagnostic peaks for several hopanes and steranes.
To our knowledge, it is the first time hopanes and steranes have been detected in single oil-bearing fluid inclusions. We are currently using this approach for analysing single inclusions in Precambrian rocks, in search of organic biomarkers that could help to answer questions regarding early evolution of life on Earth.
Place, publisher, year, edition, pages
Fluid inclusion, oil, ToF-SIMS, biomarkers
Research subject Geochemistry
IdentifiersURN: urn:nbn:se:su:diva-33654OAI: oai:DiVA.org:su-33654DiVA: diva2:283307
Goldschmidt conference 2009