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Relicts of Earth's earliest crust: U-Pb, Lu-Hf, and morphological characteristics of >3.7 Ga detrital zircon of the western Canadian Shield

By
R.P. Hartlaub
R.P. Hartlaub
Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
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L.M. Heaman
L.M. Heaman
Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
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A. Simonetti
A. Simonetti
Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
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C.O. Böhm
C.O. Böhm
Manitoba Geological Survey, Manitoba Industry, Economic Development and Mines, 360-1395 Ellice Ave., Winnipeg, Manitoba R3G 3P2, Canada
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Published:
January 01, 2006

Ancient (>3.7 Ga) detrital zircons represent some of the few remaining relicts of Earth's earliest evolution. A metagreywacke from the northwestern margin of the Superior Province, Canada, has abundant Paleoarchean detrital zircon with peaks in age distribution at 3.86, 3.79, 3.74, and 3.32 Ga. A fuchsitic quartzite from the western margin of the Rae Province, Canada, contains entirely Paleoarchean detritus with peaks in age distribution at 3.86, 3.76, and 3.72 Ga. Both samples contain a small (2%–4%) proportion of zircon grains that are ≥3.9 Ga. Hf isotopic analysis indicates that a large proportion of the Paleoarchean zircon from both samples was derived by reworking of significantly older crust, consistent with previously published evidence for scarce pre–4.0 Ga continental crust from Jack Hills, Australia, and the Acasta Gneiss, Canada. When comparing the detrital zircon age distributions obtained in this study with known terranes with intact Paleoarchean rocks, most similarity is observed with the Itsaq Gneiss Complex of western Greenland. A lack of ca. 3.6–3.3 Ga igneous crystallization and detrital zircon ages is apparent in the data from the western Rae Province and from the northwestern Superior Province. Many ter-ranes with significant evidence for 3.7–3.9 Ga crust also have a well-defined lack of crust formation at this time, possibly indicating a hitherto undetected relationship between these Paleoarchean terranes.

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GSA Special Papers

Processes on the Early Earth

Wolf Uwe Reimold
Wolf Uwe Reimold
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Roger L. Gibson
Roger L. Gibson
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Geological Society of America
Volume
405
ISBN print:
9780813724058
Publication date:
January 01, 2006

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