Tectonics of early Earth: Some geodynamic considerations

Abstract

Today, plate tectonics is the dominant tectonic style on Earth, but in a hotter Earth tectonics may have looked different due to the presence of more melting and associated compositional buoyancy as well as the presence of a weaker mantle and lithosphere. Here we review the geodynamic constraints on plate tectonics and proposed alternatives throughout Earth's history. Observations suggest a 100-300 °C mantle potential temperature decrease since the Archean. The use of this range by theoretical studies, parameterized convection studies, and numerical simulations puts a number of constraints on the viability of the different tectonic styles. The ability to sufficiently cool early Earth with its high radiogenic heat production forms one of the major constraints on the success of any type of tectonics. The viability of plate tectonics is mainly limited by the availability of sufficient driving forces and lithospheric strength. Proposed alternative mechanisms include local or global magma oceans, diapirism, independent dynamics of crust and underlying mantle, and large-scale mantle overturns. Transformation of basaltic crust into dense eclogite is an important driving mechanism, regardless of the governing tectonic style.