1. School of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth , Australia
2. Department of Geology & Geophysics, University of Wisconsin, Madison, Wisconsin 53706, USA
3. Department of Geology & Geophysics, University of Edinburgh, Edinburgh, EH9 3JW, UK
4. Present address: Department of Geology, Colgate University, Hamilton, New York 13346 , USA

Correspondence to: Correspondence and requests for materials should be addressed to S.A.W. (e-mail: Email: wildes@lithos.curtin.edu.au).

Abstract

No crustal rocks are known to have survived since the time of the intense meteor bombardment that affected Earth¹ between its formation about 4,550 Myr ago and 4,030 Myr, the age of the oldest known components in the Acasta Gneiss of northwestern Canada². But evidence of an even older crust is provided by detrital zircons in metamorphosed sediments at Mt Narryer³ and Jack Hills^{4, 5, 6, 7, 8} in the Narryer Gneiss Terrane⁹, Yilgarn Craton, Western Australia, where grains as old as 4,276 Myr have been found⁴. Here we report, based on a detailed micro-analytical study of Jack Hills zircons¹⁰, the discovery of a detrital zircon with an age as old as 4,404 8 Myr—about 130 million years older than any previously identified on Earth. We found that the zircon is zoned with respect to rare earth elements and oxygen isotope ratios (¹⁸O values from 7.4 to 5.0), indicating that it formed from an evolving magmatic source. The evolved chemistry, high ¹⁸O value and micro-inclusions of SiO₂ are consistent with growth from a granitic melt^{11, 2} with a ¹⁸O value from 8.5 to 9.5. Magmatic oxygen isotope ratios in this range point toward the involvement of supracrustal material that has undergone low-temperature interaction with a liquid hydrosphere. This zircon thus represents the earliest evidence for continental crust and oceans on the Earth.

1. School of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth , Australia
2. Department of Geology & Geophysics, University of Wisconsin, Madison, Wisconsin 53706, USA
3. Department of Geology & Geophysics, University of Edinburgh, Edinburgh, EH9 3JW, UK
4. Present address: Department of Geology, Colgate University, Hamilton, New York 13346 , USA

Correspondence to: Correspondence and requests for materials should be addressed to S.A.W. (e-mail: Email: wildes@lithos.curtin.edu.au).