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Science. 2006 May 26;312(5777):1139; author reply 1139.

Comment on "Heterogeneous Hadean hafnium: evidence of continental crust at 4.4 to 4.5 Ga".

Author information

1
Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA. valley@geology.wisc.edu

Abstract

Harrison et al. (Reports, 23 December 2005, p. 1947) proposed that plate tectonics and granites existed 4.5 billion years ago (Ga), within 70 million years of Earth's formation, based on geochemistry of >4.0 Ga detrital zircons from Australia. We highlight the large uncertainties of this claim and make the more moderate proposal that some crust formed by 4.4 Ga and oceans formed by 4.2 Ga.

PMID:
16728619
DOI:
10.1126/science.1125301
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