Reconciling thermal regimes and tectonics of the early Earth

Thermomechanical models of mantle convection and melting in an inferred hotter Archean Earth show the emergence of pressure-temperature (P-T) regimes that resemble present-day plate tectonic environments yet developed within a non-plate tectonics regime. The models' P-T gradients are compatible with those inferred from evolving tonalite-trondhjemite-granodiorite series rocks and the paired metamorphic belt record, supporting the feasibility of divergent and convergent tectonics within a mobilized, yet laterally continuous, lithospheric lid. "Hot" P-T gradients of 10-20 °C km^-1 form along asymmetric lithospheric drips, then migrate to areas of deep lithospheric downwelling within ~300-500 m.y., where they are overprinted by high-pressure warm and, later, cold geothermal signatures, up to ~8 °C km^-1. Comparisons with the crustal production and reworking record suggest that this regime emerged in the Hadean.