Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere.
Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed by thermal stress, are present in solvent extracts of 2,707- to 2,685-million-year-old (Ma) metasedimentary rocks from Timmins, ON, Canada. These lipids appear in conventional gas chromatograms as unresolved complex mixtures and include cyclic and acyclic biphytanes, C36-C39 derivatives of the biphytanes, and C31-C35 extended hopanes. Biphytane and extended hopanes are also found in high-pressure catalytic hydrogenation products released from solvent-extracted sediments, indicating that archaea and bacteria were present in Late Archean sedimentary environments. Postdepositional, hydrothermal gold mineralization and graphite precipitation occurred before metamorphism (approximately 2,665 Ma). Late Archean metamorphism significantly reduced the kerogen's adsorptive capacity and severely restricted sediment porosity, limiting the potential for post-Archean additions of organic matter to the samples. Argillites exposed to hydrothermal gold mineralization have disproportionately high concentrations of extractable archaeal and bacterial lipids relative to what is releasable from their respective high-pressure catalytic hydrogenation product and what is observed for argillites deposited away from these hydrothermal settings. The addition of these lipids to the sediments likely results from a Late Archean subsurface hydrothermal biosphere of archaea and bacteria.
Ventura
Gregory T
GT
Department of Earth and Environmental Sciences, University of Illinois at Chicago, M/C 186, 845 West Taylor Street, Chicago, IL 60607-7059, USA. gventura@whoi.edu
Kenig
Fabien
F
Reddy
Christopher M
CM
Schieber
Juergen
J
Frysinger
Glenn S
GS
Nelson
Robert K
RK
Dinel
Etienne
E
Gaines
Richard B
RB
Schaeffer
Philippe
P
D001105:Archaea / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D002244:Carbon / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D002849:Chromatography, Gas; D019143:Evolution, Molecular; D005580:Fossils; D006108:Graphite / Q000737:chemistry / Q000378:metabolism; D006838:Hydrocarbons / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D050356:Lipid Metabolism; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000378:metabolism*
D006838:Hydrocarbons; D009930:Organic Chemicals; D014867:Water; D002244:Carbon; D006108:Graphite; D006859:Hydrogen; C006647:asphalt