Early life signatures in sulfur and carbon isotopes from Isua, Barberton, Wabigoon (Steep Rock), and Belingwe Greenstone Belts (3.8 to 2.7 Ga)

N.V. Grassineau, P. Abell, P.W.U. Appel, D. Lowry, E.G. Nisbet

Publikation: Bidrag til bog/rapport/konferenceproceedingsBogkapitelForskningpeer review

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Abstrakt

Carbon and sulfur isotopes have been measured on samples from four Archean greenstone belts dating from 3.8 Ga to 2.7 Ga, in order to trace metabolic changes as life evolved over this one-billion-year period. In the Isua Greenstone Belt (3.8 Ga), Greenland, δ34 S in sulfide minerals from sedimentary sequences range from -3.8‰ to +3.4‰. δ13 C red measured in BIFs, turbidites and conglomerates vary from -29.6‰ to -14.7‰; this range permits us to hypothesize the presence of hyperthermophilic and chemotrophic species in transient settings, or possibly pelagic photoautotrophic microbes, or both. In the Barberton Greenstone Belt, South Africa, sulfide minerals show δ 34S values from +1.5‰ to +5.6‰. Black shales have δ 13C red values from -32.4‰ to -5.7‰, suggesting that oxygenic photosynthetic and sulfate-reducing bacteria were present by ca. 3.24 Ga. The δ13 C red measured in the stromatolites of Steep Rock Lake (3.0 Ga), Ontario, Canada, are from -30.6‰ to -21.6‰, giving clear evidence for occupation of a shallow water environment by cyanobacteria. The wide isotopic ranges for δ34 S in sulfides from -21.1‰ to +16.7‰ and for δ13 C red in carbon-rich cherts and black shales from -43.4‰ to -7.2‰ in the Belingwe Greenstone Belt, Zimbabwe, indicate that photosynthetic microbial mat communities were well established at 2.7 Ga. In these well-preserved Late Archean formations, modern-style biological sulfur and carbon cycles may have been in operation. The δ 34S and δ13 C red ranges, respectively 37‰ and 36‰, indicate a great variety of biological processes interacting with each other.

OriginalsprogEngelsk
TitelEvolution of early Earth's atmosphere, hydrosphere, and biosphere - constraints from ore deposits
RedaktørerStephen E. Kesler, Hiroshi Ohmoto
ForlagGeological Society of America
Sider33-52
Antal sider20
ISBN (Trykt)9780813711980
DOI
StatusUdgivet - 1 jan. 2006

Publikationsserier

NavnGeological Society of America Memoir
ForlagGeological Society of America
Vol/bind198

Programområde

  • Programområde 4: Mineralske råstoffer

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