Hadean zircon formed due to hydrated ultramafic protocrust melting

Abstract Hadean zircons, from the Jack Hills (Western Australia) and other localities, are currently only window into earliest terrestrial felsic crust, formation of which remains enigmatic. Based upon new experimental results, generation such early crust has been hypothesized to involve partial melting hydrated peridotite interacting with basaltic melt at low pressure (<10 km), but it yet be demonstrated that liquids can indeed crystallize zircons comparable zircon. We used thermodynamic geochemical modeling test this hypothesis. The predicted zircon saturation temperatures <750 °C, together model Th, U, Nb, Hf, Y, rare earth element (REE) contents 700 ?18OVSMOW (Vienna standard mean ocean water) signatures, co-crystallizing mineral assemblage were compared those This comparison was favorable respect crystallization temperature, most trace-element contents, inclusions in discrepancy signatures may explained by hotter conditions protocrust hydration. Our work supports idea magma shallow depths involving a primordial weathered ultramafic local intrusions is viable mechanism for on Earth.