Utility of Raman spectroscopy in estimates of the thermal maturity of Ediacaran organic matter: An example from the East European Craton |
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| Affiliation: | 1. Institute of Geological Sciences, Polish Academy of Sciences, Research Centre in Krakow, Poland;2. Faculty of Earth Sciences, University of Silesia, Będzińska 60, 41-200 Sosnowiec, Poland;1. Institute of Archaeology, University of Wrocław, Poland;2. Institute of Geological Sciences, University of Wrocław, Poland;1. University of Wrocław, Institute of Geological Sciences, Cybulskiego 30, 50-205, Wrocław, Poland;2. Wrocław University of Environmental and Life Sciences, Department of Soil Sciences and Environmental Protection, CK Norwida 25/27, 50-375, Wrocław, Poland;3. Charles University, Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Albertov 6, 128 43, Prague 2, Czech Republic;1. University of Tartu, Department of Geology, 50411 Tartu, Estonia;2. Quaternary Surveys, 26 Thornhill Ave., Thornhill, Ontario, Canada L4J1J4;1. Institute of Geological Sciences, Polish Academy of Sciences, Krakow, Poland;2. Research and Production Center for Geology, Minsk, Belarus;3. Institute of Physics, Jagiellonian University, Krakow, Poland;4. Institut de Chimie des Milieux et Matériaux de Poitiers, Univ. Poitiers – CNRS, France;5. Engineering Geology, Technical University of Munich, Munich, Germany;6. University of Silesia, Faculty of Earth Sciences, Sosnowiec, Poland |
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| Abstract: | Raman spectroscopy was used as a supplementary method to characterise the thermal maturity of Ediacaran organic matter (OM) from the East European Craton. Because this method is based on organic particles measurement, it appears to be a good supplementary method in addition to the acquisition of biomarker data, which is based on extractable organic matter and may be affected by potential contamination. Raman spectroscopy seems to be particularly useful for lower Palaeozoic rocks, which do not contain vitrinite. Here, we compared C31 22S/(S + R) homohopane ratio results (obtained using gas chromatography – mass spectrometry), with various Raman parameters including: G_STA, Gmax position, Dmax/Gmax, FWHMG, RAR, D_STA, and PDmax. Close correlations were observed between C31 22S/(S + R) and G_STA, Gmax position, Dmax/Gmax, and FWHMG, reaching values of R2 = 0.5‒0.6, whereas no correlation existed between homohopane ratio and the RAR, D_STA, and PDmax parameters. Raman spectroscopy results divided Ediacaran samples into two distinctive groups: (i) immature (Russian, Lithuanian, and Belarusian), characterised by relatively higher values of G_STA, Dmax/Gmax, and FWHMG and relatively lower values of PGmax, and (ii) mature (Polish and Ukrainian), with relatively lower values of G_STA, Dmax/Gmax, and FWHMG and relatively higher values of PGmax. Within each group no statistically confirmed differences were found. However, significant discrepancies were observed between the hopane ratio and Raman parameters in Lithuanian samples, in relation to other samples from the group (i). Values of the C31 22S/(S + R) ratio for Lithuanian samples are close to those for the group (ii) and significantly higher than those for the group (i). However, all Raman parameters are the same as those of the rest samples from the group (i), indicating the immature character of OM from Lithuanian rocks. We interpret this discrepancy as representing contamination of the cores with drilling fluids, resulting in increased values for the C31 22S/(S + R) ratio. In this case, Raman spectroscopy is a useful tool for detecting extract contamination and appears to be an effective and decisive method in the case of rocks suspected of contamination. |
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| Keywords: | Raman spectroscopy Biomarkers Correlation Maturity Ediacaran |
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