Crustal rejuvenation stabilised Earth\u2019s first cratons

Jacob A Mulder,Nicholas J Gardiner,Timothy J Ivanic,Oliver Nebel,Ashlea N Wainwright,Peter A Cawood

doi:10.1038/s41467-021-23805-6

Abstract

The formation of stable, evolved (silica-rich) crust was essential in constructing Earth’s first cratons, the ancient nuclei of continents. Eoarchaean (4000–3600 million years ago, Ma) evolved crust occurs on most continents, yet evidence for older, Hadean evolved crust is mostly limited to rare Hadean zircons recycled into younger rocks. Resolving why the preserved volume of evolved crust increased in the Eoarchaean is key to understanding how the first cratons stabilised. Here we report new zircon uranium-lead and hafnium isotope data from the Yilgarn Craton, Australia, which provides an extensive record of Hadean–Eoarchaean evolved magmatism. These data reveal that the first stable, evolved rocks in the Yilgarn Craton formed during an influx of juvenile (recently extracted from the mantle) magmatic source material into the craton. The concurrent shift to juvenile sources and onset of crustal preservation links craton stabilisation to the accumulation of enduring rafts of buoyant, melt-depleted mantle.

Highlights

The formation of stable, evolved crust was essential in constructing Earth’s first cratons, the ancient nuclei of continents
The delayed arrival of this stable crust, over 500 Model Age (Ma) after planetary accretion, has traditionally been attributed to the wholesale destruction of pre-existing Hadean crust either by intense meteorite bombardment[1], mantle overturns[2], or subduction[3]. These models continue to be challenged by discoveries of intact remnants of Hadean crust[4,5], recycled Hadean zircons in younger rocks[6,7,8], and Hadean radiogenic Pb and 142Nd isotopic signatures in several cratons worldwide[5,9,10,11], which indicate that potentially large tracts of Hadean crust survived the Hadean–Eoarchaean transition
Eoarchaean TTGs sourced from juvenile reservoirs inherited the near-chondritic Hf isotopic composition of the Eoarchaean mantle[16,17], whereas Eoarchaean TTGs sourced from ancient reservoirs acquired less radiogenic Hf isotopic signatures

Summary

Introduction

The formation of stable, evolved (silica-rich) crust was essential in constructing Earth’s first cratons, the ancient nuclei of continents. The delayed arrival of this stable crust, over 500 Ma after planetary accretion, has traditionally been attributed to the wholesale destruction of pre-existing Hadean crust either by intense meteorite bombardment[1], mantle overturns[2], or subduction[3] These models continue to be challenged by discoveries of intact remnants of Hadean crust[4,5], recycled Hadean zircons in younger rocks[6,7,8], and Hadean radiogenic Pb and 142Nd isotopic signatures in several cratons worldwide[5,9,10,11], which indicate that potentially large tracts of Hadean crust survived the Hadean–Eoarchaean transition. New zircon U–Pb and Hf isotopic data reveal a link between the onset of crustal preservation in the Yilgran Craton and a fundamental shift in the source characteristics of evolved magmatism across the Hadean–Eoarchaean transition

Methods

Results

Conclusion