3.4-Billion-Year-Old Biogenic Pyrites from Barberton, South Africa: Sulfur Isotope Evidence

Laser ablation mass spectroscopy analyses of sulfur isotopic compositions of microscopic-sized grains of pyrite that formed about 3.4 billion years ago in the Barberton Greenstone Belt, South Africa, show that the pyrite formed by bacterial reduction of seawater sulfate. These data imply that by abo...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1993-10, Vol.262 (5133), p.555-557
Main Authors: Ohmoto, Hiroshi, Kakegawa, Takeshi, Lowe, Donald R.
Format: Article
Language:English
Subjects:
Crystals
Exobiology
Geologic Sediments - analysis
Geological Phenomena
Geology
Greenstone belts
Hydrogen Sulfide - analysis
Hydrogen Sulfide - metabolism
Iron - analysis
Isotopes
Marine sediments
Oceans
Oceans and Seas
Pyrites
Rocks
Sea water
Seawater - analysis
Seawater - chemistry
Sedimentary rocks
Sediments
South Africa
Space life sciences
Sulfates - analysis
Sulfates - metabolism
Sulfides
Sulfides - analysis
Sulfur
Sulfur Isotopes
Sulfur-Reducing Bacteria - metabolism
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Summary:Laser ablation mass spectroscopy analyses of sulfur isotopic compositions of microscopic-sized grains of pyrite that formed about 3.4 billion years ago in the Barberton Greenstone Belt, South Africa, show that the pyrite formed by bacterial reduction of seawater sulfate. These data imply that by about 3.4 billion years ago sulfate-reducing bacteria had become active, the oceans were rich in sulfate, and the atmosphere contained appreciable amounts (> > 10$^{-13}$ of the present atmospheric level) of free oxygen.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.11539502