Ideas and perspectives: Hydrothermally driven redistribution and sequestration of early Archaean biomass—the ‘hydrothermal pump hypothesis’

Abstract

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 old 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-18. A very similar distribution (≤ n-C18) was observed in HyPy products of preextracted recent bacterial biomass, while abiotic compounds synthesised via Fischer-Tropsch-type synthesis exhibited a modal distribution. We therefore propose that the original organic matter in the Archaean chert veins has a primarily microbial origin. We hypothesise that the microbially-derived organic matter accumulated in different aquatic and subsurface Dresser environments, and was then assimilated, redistributed and sequestered by hydrothermal fluids (‘hydrothermal pump hypothesis’).