Testing the geological fate of abiogenic carbonaceous matter

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Organic matter (OM) has been in the focus of numerous investigations as a potential biosignature in Precambrian rocks. However OM can not per se been taken as evidence of life, because there existed numerous abiogenic sources, such as delivery from meteorites and abiogenic organic synthesis. The latter, possibly fueled by hydrothermal energy, impacts, lightning, or UV-radiation, may have proceeded to a much greater extent on the early Earth than today. In the proposed project, a P,T-experiment will be performed to investigate the thermal evolution of abiotic OM generated by Fischer-Tropsch type (FTT) synthesis. The goal is to provide clues to the distinction of biogenic and abiotic OM in Precambrian rocks and other geological samples. FTT synthesis will be performed under hydrothermal conditions using Morey-type reaction vessels and montmorillonite clay as a catalyst. The resulting abiotic OM are artificially maturated in cold-seal pressure vessels (CSPV, gold bags) at lithostatic pressure (1,5kbar) for 10 different time intervals (10min-1yr). Type I kerogen prepared from an immature Eocene oil shale is run in parallel as a reference. The FTT-derived OM and its maturation products (bitumen and kerogen) are analysed using GC-MS, GC-C-IRMS, catalytic hydropyrolysis (HyPy), and Raman-spectroscopy. The properties of abiotic OM maturated under different P,T-conditions will then be compared to Archaean real-world materials. We expect that the results will provide us with a robust clues to the biogenicity of individual kerogens preserved in different facies of the oldest terrestrial rocks carrying indigenous OM.