Argon constraints on the early growth of felsic continental crust.

The continental crust is a major geochemical reservoir, the evolution of which has shaped the surface environment of Earth. In this study, we present a new model of coupled crust-mantle-atmosphere evolution to constrain the growth of continental crust with atmospheric Ar/Ar. Our model is the first to combine argon degassing with the thermal evolution of Earth in a self-consistent manner and to incorporate the effect of crustal recycling and reworking using the distributions of crustal formation and surface ages. Our results suggest that the history of argon degassing favors rapid crustal growth during the early Earth. The mass of continental crust, highly enriched in potassium, is estimated to have already reached >80% of the present-day level during the early Archean. The presence of such potassium-rich, likely felsic, crust has important implications for tectonics, surface environment, and the regime of mantle convection in the early Earth.