Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archaean biomass – the “hydrothermal pump hypothesis”

• Published in: Biogeosciences Vol. 15; no. 5; pp. 1535 - 1548
• Main Authors: Duda, Jan-Peter, Thiel, Volker, Bauersachs, Thorsten, Mißbach, Helge, Reinhardt, Manuel, Schäfer, Nadine, Van Kranendonk, Martin J, Reitner, Joachim
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 15-03-2018; Copernicus Publications
• Subjects: Alkanes; Anoxia; Archaea; Biomass; Biosynthesis; Carbon compounds; Catalysis; Chert; Cratons; Distribution; Environmental aspects; Fluids; Hydropyrolysis; Hydrothermal fields; Hydrothermal systems (Geology); Hypotheses; Kerogen; Microorganisms; Organic carbon; Organic matter; Properties; Veins (geology); Australia; Western Australia Australia; Germany
• ISSN: 1726-4189; 1726-4170; 1726-4189
• DOI: 10.5194/bg-15-1535-2018

Archaean hydrothermal chert veins commonly contain abundant organic carbon of
uncertain origin (abiotic vs. biotic). In this study, we analysed kerogen
contained in a hydrothermal chert vein from the ca. 3.5 Ga Dresser
Formation (Pilbara Craton, Western Australia). Catalytic hydropyrolysis
(HyPy) of this kerogen yielded n-alkanes up to n-C22, with a sharp
decrease in abundance beyond n-C18. This distribution
(≤ n-C18) is very similar to that observed in HyPy products of
recent bacterial biomass, which was used as reference material, whereas it
differs markedly from the unimodal distribution of abiotic compounds
experimentally formed via Fischer–Tropsch-type synthesis. We therefore
propose that the organic matter in the Archaean chert veins has a primarily
microbial origin. The microbially derived organic matter accumulated in
anoxic aquatic (surface and/or subsurface) environments and was then
assimilated, redistributed and sequestered by the hydrothermal fluids
(“hydrothermal pump hypothesis”).