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ToF-SIMS as a tool for analysing organic material in geological samples -Fluid inclusions and beyond
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In situ analysis of organic material in rocks has potential to answer questions in geochemistry, astro- and geobiology. Recently, successful studies which included in situ analyses of geological samples with time-of-flight secondary ion mass spectrometry (ToF-SIMS) were carried out. In this PhD project possibilities and limitations of ToF-SIMS analysis of organic material in geological samples will be further explored. The main objective of the project is to develop an approach for analysis of single oil-bearing fluid inclusions and most importantly the detection of biomarkers, such as hopanes and steranes, in these inclusions. Analysis of oil-bearing fluid inclusions is attractive as they may provide an uncontaminated source of Precambrian hopanes and steranes, which are key biomarkers for tracking the early evolution of life on Earth. Due to presence of several inclusion generations, single inclusion analysis is preferred in order to constrain biomarkers to specific inclusions. The small sample amount in oil-bearing fluid inclusions, however, usually makes it difficult to analyse single inclusions with standard technique gas chromatography mass spectrometry (GC-MS). ToF-SIMS with high sensitivity, high mass resolution, imaging and depth profiling capabilities provides an excellent tool for analysis of these types of samples. The development of the approach for analysis of single oil-bearing inclusions was done in a two-step process; i) a number of crude oils were analysed with ToF-SIMS and GC-MS to facilitate interpretation of ToF-SIMS spectra of these types of samples and, ii) a procedure that combines micrographs with ion etching and ToF-SIMS analysis was developed for analysis of inclusions. With this approach it was possible to detect hopanes and steranes in single oil-bearing fluid inclusions. The next step of the project will be to analyse inclusions in Precambrian rocks in search for hopanes and steranes. In addition to the Precambrian samples, the capabilities of ToF-SIMS in analysis of geological samples will be further explored with analysis of additional samples, including Martian meteorites and microbial mats from hot springs in Yellowstone National Park.

Abstract [sv]

In situ-analys av organiskt material i geologiska prover har potential att svara på viktiga frågor i geokemi, geo- och astrobiologi. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) har nyligen framgångsrikt använts för in situ-analys av geologiska prover. Målet för doktorandprojektet är att utforska möjligheterna och begränsningarna för analys av organiskt material i geologiska prover med ToF-SIMS.Huvudmålet med projektet är att utveckla en metod som kan detektera hopaner och steraner i enskilda oljebärande vätskeinneslutningar. Vätskeinneslutningar är intressanta då de är en potentiell källa för prekambriska biomarkörer som hopaner och steraner vilka används till att utforska livets tidiga utveckling på jorden. Analys av enskilda inneslutningar är emellertid oftast nödvändigt för att kunna tidsbegränsa biomarkörer. På grund av de flesta inneslutningar är små (10 μm i diameter) är det inte möjligt att analysera en enskild vätskeinneslutning med standardtekniken gaskromatografi-masspektrometri. ToF-SIMS med sin höga känslighet, höga massupplösning och kapacitet för 2D representation av analysdata och djupprofilering av prover är ett utmärkt instrument för analys av enskilda inneslutningar.Metoden för analys av enskilda inneslutningar utvecklades i två steg. Först analyserades ett antal råoljor med ToF-SIMS och GC-MS för att underlätta förståelsen av ToF-SIMS spektra av dessa typer av prover och därefter utvecklades en metod för analys av enskilda inneslutningar som består av mikroskopering, jonetsning och ToF-SIMS analys av det exponerade inneslutningsmaterialet. Med den utvecklade metoden var det möjligt att detektera hopaner och steraner i enskilda oljebärande vätskeinneslutningar. Nästa steg i projektet blir att analysera enskilda inneslutningar i prekambriska prover i hopp om att detektera hopaner och steraner i dessa. Dessutom kommer andra prover att analyseras i projektet, inklusive marsmeteoriter och biofilmer från heta källor i Yellowstone, USA.

Place, publisher, year, edition, pages
2009.
Keyword [en]
Organic material, ToF-SIMS
National Category
Other Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
URN: urn:nbn:se:su:diva-33653OAI: oai:DiVA.org:su-33653DiVA: diva2:283302
Presentation
2009-02-06, 14:00 (English)
Supervisors
Available from: 2011-08-29 Created: 2009-12-23 Last updated: 2011-08-29Bibliographically approved
List of papers
1. Detection of organic biomarkers in crude oils using ToF-SIMS
Open this publication in new window or tab >>Detection of organic biomarkers in crude oils using ToF-SIMS
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2009 (English)In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 1, 135-143 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
ToF-SIMS, biomarkers, oil, time-of-flight secondary ion mass spectrometry
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-16184 (URN)10.1016/j.orggeochem.2008.08.010 (DOI)000262806300014 ()
Available from: 2008-12-15 Created: 2008-12-15 Last updated: 2017-12-13Bibliographically approved
2. Analysis of hopanes and steranes in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS)
Open this publication in new window or tab >>Analysis of hopanes and steranes in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS)
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2010 (English)In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 8, no 1, 37-44 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Fluid inclusions, oil, biomarkers, ToF-SIMS, hopanes, sterans
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-33651 (URN)10.1111/j.1472-4669.2009.00223.x (DOI)000272836600003 ()
Available from: 2009-12-23 Created: 2009-12-23 Last updated: 2017-12-12Bibliographically approved

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