Early Earth zircons formed in residual granitic melts produced by tonalite differentiation

Abstract The oldest geological materials on Earth are Hadean (>4 Ga) detrital zircon grains. Their chemistry and apparently low Ti-in-zircon temperatures (?700 °C) considered to be inconsistent with crystallization in a magma of the tonalite-trondhjemite-granodiorite (TTG) suite, although these dominant Archean (4.0–2.5 silicic rocks. Using new data set trace element contents zircons from Paleoarchean Barberton TTGs (South Africa) thermodynamic modeling, we show that have crystallized at near-solidus conditions compositionally uniform granitic melt. This melt is residual less evolved (tonalitic) parent thereby shows major compositions different bulk TTG A global compilation reveals most TTG-hosted grains share peculiar signature distinct chemical trends defined by Phanerozoic zircons. Our model Ti early reflect higher (720–800 than initially inferred due lower modeled TiO2 activity relative previous estimates. We therefore propose chemically TTG-like magmatic environment was zircon-forming process Earth.