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Metasomatic Origin of Quartz-Pyroxene Rock, Akilia, Greenland, and Implications for Earth's Earliest Life
Christopher M. Fedo,1*Martin J. Whitehouse2
A quartz-pyroxene rock interpreted as a banded iron formation
(BIF) from the island of Akilia, southwest Greenland, contains13C-depleted graphite that has been claimed as evidence for
theoldest (>3850 million years ago) life on Earth. Field
relationshipson Akilia document multiple intense deformation events
that haveresulted in parallel transposition of Early Archean rocks andsignificant boudinage, the tails of which commonly form the bandingin
the quartz-pyroxene rock. Geochemical data possess distinctcharacteristics consistent with an ultramafic igneous, not BIF,protolith for this lithology and the adjacent schists. Later
metasomaticsilica and iron introduction have merely resulted in a rock
thatsuperficially resembles a BIF. An ultramafic igneous origin
invalidatesclaims that the carbon isotopic composition of graphite
inclusionsrepresents evidence for life at the time of crystallization.
1 Department of Earth and Environmental
Sciences, George Washington University, Washington, DC 20052, USA.
2 Swedish Museum of Natural History, Laboratory for
Isotope Geology, Box 50007, SE-104 05 Stockholm, Sweden.
*
To whom correspondence should be addressed. E-mail:
cfedo{at}gwu.edu
The editors suggest the following Related Resources on Science sites:
In Science Magazine
TECHNICAL COMMENTS
S. J. Mojzsis, T. M. Harrison, Clark R. L. Friend, Allen P. Nutman, Victoria C. Bennett, Christopher M. Fedo, and Martin J. Whitehouse (1 November 2002) Science298 (5595), 917a.
[DOI: 10.1126/science.298.5595.917a] |Full Text »|PDF »
LETTERS
J. Michael Palin;, Christopher M. Fedo, and Martin J. Whitehouse (1 November 2002) Science298 (5595), 961c.
[DOI: 10.1126/science.298.5595.961c] |Full Text »|PDF »
NEWS FOCUS
Richard A. Kerr (24 May 2002) Science296 (5572), 1384.
[DOI: 10.1126/science.296.5572.1384] |Summary »|Full Text »|PDF »
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