Lateral Mixing Processes in the Hadean

Abstract

Samples of ancient Eoarchean volcanism suggest the existence of isotopically distinct mantle domains. 142Nd evidence suggests that these domains formed within the first several hundred million years of Earth's history and were preserved until circa 3.7 Ga—a span of almost 800 Myr. Here we explore evolving mantle convection models under Hadean conditions to constrain mantle mixing dynamics and in particular focus on the generation, or preservation, of upper mantle hemispheric compositional anomalies. We find that initially radially homogenous models fail to produce hemispheric anomalies spontaneously due to mixing processes and that rheological and buoyancy effects, or asymmetric processes such as plate tectonics or meteorite impacts, do not generate long-lived heterogeneities in upper mantle composition from homogenous initial conditions. In contrast, models initiated with compositional variations can preserve these hemispheric differences of periods >800 Myr despite vigorous internal convection, as a function of the proclivity of these models to exhibit stagnant-lid behavior, resulting in isolated convection cells with restricted lateral transport.