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- Siljeström, Sandra, et al.
(author)
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Detection of hopanes and steranes in single oil-bearing fluid inclusions using ToF-SIMS
- 2009
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In: IMOG 24th International Meeting of Organic Geochemistry, Book of Abstract, www.imog2009.org. ; , s. 6-
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Conference paper (other academic/artistic)abstract
- Hopanes and steranes are key biomarkers when tracking early evolution of life on Earth. A potential contamination-free source of Precambrian biomarkers is oil-bearing fluid inclusions as the oil has been secluded from the environment since the formation of the inclusion. Due to presence of often several generations of inclusions it can be problematic to assign the biomarkers to specific inclusions. It has, however, because of the small size of inclusions (5-30 µm), not been possible to analyse single oil-bearing fluid inclusions. We present here an approach employing time-of-flight secondary ion mass spectrometry (ToF-SIMS) to selectively open individual oil inclusions in situ by ion etching, and precisely analyse their picoliter content for steranes and hopanes. A number of oil-bearing inclusions from hydrothermal veins in the Siljan impact structure in south-central Sweden were analysed. The approach used for analysis of a single inclusion consisted of the following steps i) localization of suitable inclusion in double polished thin section with optical microscopy, ii) opening of inclusion by ion etching with C60+ 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. The micrographs and the ToF-SIMS ion images collected before, during and after analysis ensured the correct inclusion had been analysed. ToF-SIMS spectra reconstructed from analysis times and 2D regions of interest with increased organic ion signal showed a large number of organic peaks (up to m/z 500) that are characteristic for a crude oil. Comparison of the reconstructed spectra with those of a Siljan seep oil, which has previously been analysed with ToF-SIMS, showed a high degree of resemblance, as expected from the geological interpretation of the origin on the oils. All major characteristic peaks for several hopanes and steranes were detected in the mass spectra from the single fluid inclusion (Fig. 1). The agreement with respect to mass accuracy (< 50 ppm), fragment pattern and isotope distributions between these peaks and those observed in spectra from standard samples and from hopanes and steranes in the Siljan seep oil, provide strong evidence for the presence of hopanes and steranes in the analysed single fluid inclusions. The results thus demonstrate that the approach presented here has the capability to detect specific biomarkers in individual single oil inclusions. It is to our knowledge the first time hopanes and steranes have been detected in single oil-bearing fluid inclusins and the next step will be to analyse single oil-bearing fluid inclusions in Precambrian rocks with ToF-SIMS in search for organic biomarkers. Detection of hopanes and steranes in such an inclusion could help to answer questions regarding early evolution of life on Earth, including the first appearance of the eukaryotes on Earth.
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- Siljeström, Sandra, et al.
(author)
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Detection of organic biomarkers in crude oils using ToF-SIMS
- 2009
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In: Organic Geochemistry. - : Elsevier BV. - 0146-6380 .- 1873-5290. ; 40:1, s. 135-143
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Journal article (peer-reviewed)abstract
- In this study, we show that time of flight-secondary ion mass spectrometry (ToF-SIMS) can be used todetect organic biomarkers, such as hopanes and steranes, in non-fractionated crude oils, without extractionand chemical preparation. Hopanes and steranes may provide valuable information on the history oflife on early Earth, particularly if they are present in fluid inclusions in ancient rocks. Due to the presenceof different generations of inclusions in even very small rock samples, it would be advantageous to find amethod capable of detecting biomarkers in single oil rich fluid inclusions. The capability of ToF-SIMS fordetailed chemical analysis of very small sample amounts makes it a potential technique for such analysis,and in this work this possibility is explored. The presence of hopanes and steranes in four different crudeoils of different ages and stages of biodegradation was investigated using ToF-SIMS and GC–MS. By combininganalyses of biomarker standards, crude oils and chromatographic oil fractions, specific peaks forthe different biomarkers were identified in the ToF-SIMS spectra. The presence of these peaks in the spectrafrom the crude oil samples could be attributed to the biomarkers based on exact mass determinationand by comparison with the spectra from the biomarker containing and biomarker lacking fractions,respectively. In addition, the results show that a significant biomarker signal may be obtained from a 10 µm2 oil sample, demonstrating the potential of ToF-SIMS for analysis of single oil bearing fluid inclusions,which in turn may contribute to a better understanding of the early history of life on Earth.
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- Siljeström, Sandra, 1980-, et al.
(author)
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ToF-SIMS analysis of hopanes and steranes in single oil-bearing fluid inclusions
- 2009
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In: Geochimica et Cosmochimica Acta, vol 73, A1223.
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Conference paper (other academic/artistic)abstract
- 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.
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- Siljeström, Sandra, et al.
(author)
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ToF-SIMS Possibilities in Geobiology
- 2008
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In: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; , s. 329-
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Conference paper (other academic/artistic)abstract
- Signs of earliest life on Earth are often controversial. Organic biomarkers, which are widely used to identify biological traces in geological samples, can provide additional information. We present examples of how Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) can be used on its own and in combination with other techniques to detect biomarkers in a variety of samples, including crude oils and microbial cells. ToF-SIMS with its unique combination of absolute sensitivity, high mass resolution and imaging capabilities can help answer geobiological questions and may ultimately be applied to Early Earth and extraterrestrial samples.
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- Sjövall, Peter, et al.
(author)
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Detection of organic biomarkers in crude oils using ToF-SIMS
- 2009
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In: Organic Geochemistry. ; 40, s. 135-143
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Journal article (peer-reviewed)abstract
- In this study, we show that time of flight-secondary ion mass spectrometry (ToF-SIMS) can be used to detect organic biomarkers, such as hopanes and steranes, in non-fractionated crude oils, without extraction and chemical preparation. Hopanes and steranes may provide valuable information on the history of life on early Earth, particularly if they are present in fluid inclusions in ancient rocks. Due to the presence of different generations of inclusions in even very small rock samples, it would be advantageous to find a method capable of detecting biomarkers in single oil rich fluid inclusions. The capability of ToF-SIMS for detailed chemical analysis of very small sample amounts makes it a potential technique for such analysis, and in this work this possibility is explored.
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- Sjövall, Peter, et al.
(author)
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Organic Geochemical Microanalysis by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)
- 2008
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In: Geostandards and Geoanalytical Research. ; 32, s. 267-277
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Journal article (peer-reviewed)abstract
- Time-of-flight secondary ion mass spectrometry(ToF-SIMS) is a powerful method for the chemicalanalysis of solid surfaces. In this paper, thecapabilities and limitations of this technique andthe potential for its use in geochemical research areoutlined. Using ToF-SIMS, the chemical compositionof sample structures down to 10–100 μm can bedetermined, without the need for pre-selection orlabelling of the analysed substances. In addition,the lateral distribution of organic and inorganiccompounds can be mapped in geochemicalsamples at a resolution in the micrometre range.The capabilities of the technique in geochemistryare illustrated by two examples. In the first example,it is shown that ToF-SIMS can be used to detectbiomarkers in oil samples, making it a promisingmethod for the analysis of biomarkers in fluidinclusions. In the second example, a number ofspecific lipid biomarkers were identified andmapped on the surface of a microbial matcryosection surface. Post-measurement opticalmicroscopy correlated the localisation of the lipidswith the presence of methanotrophic archaea in themicrobial mat.
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