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Hydrocarbons and organic biomarkers extracted from black shales and other carbonaceous sedimentary rocks are valuable sources of information on the biodiversity and environment of early Earth. However, many Precambrian hydrocarbons including biomarkers are suspected of being younger contamination. An alternative approach is to study biomarkers trapped in oil-bearing fluid inclusions by bulk crushing samples and subsequently analysing the extracted hydrocarbons with gas chromatography- mass spectrometry. However, this method does not constrain the hydrocarbons to one particular oil inclusion, which means that if several different generations of oil inclusions are present in the sample, a mix of the content from these oil inclusions will be analysed. In addition, samples with few and/ or small inclusions are often below the detection limit. Recently, we showed that it is possible to detect organic biomarkers in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the present study, single fluid inclusion analysis has been performed on Proterozoic samples for the first time. Four individual oil-bearing fluid inclusions, found in 1430 Ma sandstone from the Roper Superbasin in Northern Australia, were analysed with ToF-SIMS. The ToF-SIMS spectra of the oil in the different inclusions are very similar to each other and are consistent with the presence of n-alkanes/ branched alkanes, monocyclic alkanes, bicyclic alkanes, aromatic hydrocarbons, and tetracyclic and pentacyclic hydrocarbons. These results are in agreement with those obtained from bulk crushing of inclusions trapped in the same samples. The capability to analyse the hydrocarbon and biomarker composition of single oil-bearing fluid inclusions is a major breakthrough, as it opens up a way of obtaining molecular compositional data on ancient oils without the ambiguity of the origin of these hydrocarbons. Additionally, this finding suggests that it will be possibl, AuthorCount:7;Funding acencies:Swedish Research Council 60573901; Swedish National Space Board 140/06; Australian Research Council ARC DP0556493

Organic phases trapped inside natural mineral samples are of considerable interest in astrobiology, geochemistry and geobiology. Examples of such organic phases are microfossils, kerogen and oil. Information about these phases is usually retrieved through bulk crushing of the rock which means both a risk of contamination and that the composition and spatial distribution of the organics to its host mineral is lost. An attractive of way to retrieve information about the organics in the rock is depth profiling using a focused ion beam. Recently, it was shown that it is possible to obtain detailed mass spectrometric information from oil-bearing fluid inclusions, i.e. small amounts of oil trapped inside a mineral matrix, using ToF-SIMS. Using a 10 keV C-60(+) sputter beam and a 25 keV Bi-3(+) analysis beam, oil-bearing inclusions in different minerals were opened and analysed individually. However, sputtering with a C-60(+) beam also induced other changes to the mineral surface, such as formation of topographic features and carbon deposition. In this paper, the cause of these changes is explored and the consequences of the sputter-induced features on the analysis of organic phases in natural mineral samples (quartz, calcite and fluorite) in general and fluid inclusions in particular are discussed. The dominating topographical features that were observed when a several micrometers deep crater is sputtered with 10 keV C-60(+) ions on a natural mineral surface are conical-shaped and ridge-like structures that may rise several micrometers, pointing in the direction of the incident C-60(+) ion beam, on an otherwise flat crater bottom. The sputter-induced structures were found to appear at places with different chemistry than the host mineral, including other minerals phases and fluid inclusions, while structural defects in the host material, such as polishing marks or scratches, did not necessarily result in sputter-induced structures. The ridge-like structures were often cov

Steranes and hopanes are organic biomarkers used as indicators for the first appearance of eukaryotes and cyanobacteria on Earth. Oil-bearing fluid inclusions may provide a contamination-free source of Precambrian biomarkers, as the oil has been secluded from the environment since the formation of the inclusion. However, analysis of biomarkers in single oil-bearing fluid inclusions, which is often necessary due to the presence of different generations of inclusions, has not been possible due to the small size of most inclusions. Here, we have used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to monitor in real time the opening of individualinclusions trapped in hydrothermal veins of fluorite and calcite and containing oil from Ordovician source rocks. Opening of the inclusions was performed by using a focused C60+ ion beam and the in situ content was preciselyanalysed for C27–C29 steranes and C29–C32 hopanes using Bi3+ as primary ions. The capacity to unambiguouslydetect these biomarkers in the picoliter amount of crude oil from a single, normal-sized (15–30 µm in diameter)inclusion makes the approach promising in the search of organic biomarkers for life’s early evolution on Earth.

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.

The biogenicity of ancient morphological microfossil-like objects can be established by linking morphological (e.g. cell remnants and extracellular polymeric matrix) and chemical (e.g. isotopes, biomarkers and biominerals) evidence indicative of microorganisms or microbial activity. We have developed a non-destructive micro-analytical ion beam system capable of measuring with high spatial resolution the stable carbon isotope ratios of thin samples used for transmission electron microscopy. The technique is based on elastic scattering of alpha particles with an energy of 2.751 MeV. At this energy the 13C cross section is enhanced relative to the pure Rutherford cross section for 13C, whereas the 12C cross section is reduced relative to its pure Rutherford cross section. Here we report the initial results of this experimental approach used to characterize ultramicrotomed sections of sulfur-embedded graphite and microbial cells., Part of urn:nbn:se:su:diva-477

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 inclus, Fluid inclusions, biomarkers, ToF-SIMS, oil

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.

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.

Part of urn:nbn:se:su:diva-477

Part of urn:nbn:se:su:diva-477