A Change in the Geodynamics of Continental Growth 3 Billion Years Ago

TLDR

Models of continental crust growth depend on balancing new crust generation with reworking of old crust, and zircon oxygen isotopes serve as a key archive for tracking this process. Systematic variations in zircon hafnium and oxygen isotopes show that continental crust growth was continuous but slowed markedly around 3 billion years ago, a change likely tied to the emergence of subduction‑driven plate tectonics.

Abstract

Models for the growth of continental crust rely on knowing the balance between the generation of new crust and the reworking of old crust throughout Earth's history. The oxygen isotopic composition of zircons, for which uranium-lead and hafnium isotopic data provide age constraints, is a key archive of crustal reworking. We identified systematic variations in hafnium and oxygen isotopes in zircons of different ages that reveal the relative proportions of reworked crust and of new crust through time. Growth of continental crust appears to have been a continuous process, albeit at variable rates. A marked decrease in the rate of crustal growth at ~3 billion years ago may be linked to the onset of subduction-driven plate tectonics.