3 years ago

Lateral mixing processes in the Hadean.

S. Zhang, C. J. O'Neill

Abstract

Samples of ancient Eoarchean volcanism suggest the existence of isotopically distinct mantle domains. 142Nd evidence suggests these domains formed within the first several hundred million years of Earth's history, and were preserved until ca. 3.7Ga – a span of almost 800Myr. 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 > 800Myr despite vigorous internal convection, as a function of the proclivity of these models to exhibit stagnant lid behaviour, resulting in isolated convection cells with restricted lateral transport.

Publisher URL: https://onlinelibrary.wiley.com/doi/abs/10.1029/2018JB015698

DOI: 10.1029/2018JB015698

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