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Title

No evidence for Hadean continental crust within Earth’s oldest evolved rock unit

Authors
Reimink, J. R.
Chacko, T.
Stern, R. A.
Heaman, L. M.
Sarkar, C.
Creaser, R. A.
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Published in Nature Geoscience. 2016, vol. 9, no. 10, p. 777-780
Abstract Due to the acute scarcity of very ancient rocks, the composition
 of Earth’s embryonic crust during the Hadean eon
 (>4.0 billion years ago) is a critical unknown in our search
 to understand how the earliest continents evolved. Whether
 the Hadean Earth was dominated by mafic-composition crust,
 similar to today’s oceanic crust1–4, or included significant
 amounts of continental crust5–8 remains an unsolved question that carries major implications for the earliest atmosphere the origin of life, and the geochemical evolution of the crust–mantle system. Here we present new U–Pb and Hf; isotope data on zircons from the only precisely dated Hadean rock unit on Earth—a 4,019.6 - 1.8Myr tonalitic gneiss unit in the Acasta Gneiss Complex, Canada. Combined zircon and whole-rock geochemical data from this ancient unit shows no indication of derivation from, or interaction with, older Hadean continental crust. Instead, the data provide the first direct evidence that the oldest known evolved crust on Earth was generated from an older ultramafic or mafic reservoir that probably surfaced the early Earth.
Keywords HadeanU-PbZirconEarliest rockAcastaCanada
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Other version: http://www.nature.com/doifinder/10.1038/ngeo2786
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Research group Isotope Geochemistry, Geochronology and Thermochronology
Citation
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REIMINK, J. R. et al. No evidence for Hadean continental crust within Earth’s oldest evolved rock unit. In: Nature Geoscience, 2016, vol. 9, n° 10, p. 777-780. https://archive-ouverte.unige.ch/unige:88290

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Deposited on : 2016-10-18

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