The Raman-Derived Carbonization Continuum: A Tool to Select the Best Preserved Molecular Structures in Archean Kerogens
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- Frédéric Delarue
- IMPMC Sorbonne Universités—MNHN, UPMC Univ Paris 06, UMR CNRS 7590, IRD UMR 206, Paris, France.
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- Jean-Noël Rouzaud
- Laboratoire de Géologie de l'ENS, UMR CNRS 8538, Paris, France.
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- Sylvie Derenne
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 7619 METIS, CC 105, Paris, France.
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- Mathilde Bourbin
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 7619 METIS, CC 105, Paris, France.
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- Frances Westall
- Centre de Biophysique Moléculaire, UPR CNRS 4301, Orléans, France.
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- Barbara Kremer
- Institute of Paleobiology, Polish Academy of Sciences, Warszawa, Poland.
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- Kenichiro Sugitani
- Department of Environmental Engineering and Architecture, Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan.
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- Damien Deldicque
- Laboratoire de Géologie de l'ENS, UMR CNRS 8538, Paris, France.
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- François Robert
- IMPMC Sorbonne Universités—MNHN, UPMC Univ Paris 06, UMR CNRS 7590, IRD UMR 206, Paris, France.
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説明
The search for indisputable traces of life in Archean cherts is of prime importance. However, their great age and metamorphic history pose constraints on the study of molecular biomarkers. We propose a quantitative criterion to document the thermal maturity of organic matter in rocks in general, and Archean rocks in particular. This is definitively required to select the best candidates for seeking non-altered sample remnants of life. Analysis of chemical (Raman spectroscopy, (13)C NMR, elemental analysis) and structural (HRTEM) features of Archean and non-Archean carbonaceous matter (CM) that was submitted to metamorphic grades lower than, or equal to, that of greenschist facies showed that these features had all undergone carbonization but not graphitization. Raman-derived quantitative parameters from the present study and from literature spectra, namely, R1 ratio and FWHM-D1, were used to draw a carbonization continuum diagram showing two carbonization stages. While non-Archean samples can be seen to dominate the first stage, the second stage mostly consists of the Archean samples. In this diagram, some Archean samples fall at the boundary with non-Archean samples, which thus demonstrates a low degree of carbonization when compared to most Archean CM. As a result, these samples constitute candidates that may contain preserved molecular signatures of Archean CM. Therefore, with regard to the search for the oldest molecular traces of life on Earth, we propose the use of this carbonization continuum diagram to select the Archean CM samples.Archean-Early life-Kerogen-Raman spectroscopy-Carbonization. Astrobiology 16, 407-417.
収録刊行物
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- Astrobiology
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Astrobiology 16 (6), 407-417, 2016-06
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