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The mafic precursors of TTGs may be either: (i) juvenile reservoirs, which are remelted shortly after being extracted from the mantle and emplaced in the crust or (ii) ancient reservoirs that have endured in the crust for hundreds of million years. TTGs mostly form by a two-stage process: initial extraction of primary mafic crust through partial-melting of the mantle, followed by later partial melting of that mafic crust to form evolved magma 15. Preserved evolved Eoarchaean crust is dominated by rocks of the tonalite–trondjhemite–granodiorite (TTG) suite. Testing this hypothesis has, however, proved challenging due to the scarcity and geological complexity of the ancient terranes that preserve a record of crust formation spanning the Hadean and Eoarchaean. An alternative view suggests that the Hadean Earth was surfaced by a predominantly mafic-ultramafic crust, and the Eoarchaean witnessed a fundamental change in crust-forming processes that produced the first widespread stable, evolved crust 10, 12, 13, 14. However, 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. 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. The transition between the Hadean and Eoarchaean (approximately 4000 Ma) marks the time when evolved crustal rocks-the essential building material of continents-started to become widely preserved on Earth. 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. 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. 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. Resolving why the preserved volume of evolved crust increased in the Eoarchaean is key to understanding how the first cratons stabilised. 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. The formation of stable, evolved (silica-rich) crust was essential in constructing Earth’s first cratons, the ancient nuclei of continents.

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