A rapid cooling stage in Earth’s thermal history driven by the onset of plate tectonics

Earth is the only planet that currently has plate tectonics, but it is widely thought that Earth initially operated in a stagnant lid regime, akin to present day Venus. Exactly when the transition to plate tectonics happened is debated. Because these different tectonic regimes reflect different efficiencies of convective heat loss, reconstructing the thermal history of Earth’s interior may provide valuable insight into the timing of the transition. Here, we use the composition of mantle residual peridotites as a direct constraint on the temperature of the Earth’s interior. Residual peridotites, through their olivine forsterite compositions, provide records of melting degree and mantle temperature. Our results reveal a rapid change in olivine forsterite composition from ∼92.0 to 90.9 between ∼3.0–2.0 Ga, corresponding to a change in mantle potential temperature from ∼1630 to ∼1450 °C. Rather than gradual cooling, our results suggest rapid cooling across this time period. Parameterized thermal evolution modeling shows that this shift requires a fundamental change in the efficiency of heat loss from the mantle. We interpret this change as the onset of a new geodynamic regime, from a stagnant or sluggish lid regime to a mobile-lid regime. These results provide direct petrologic evidence that modern-style plate tectonics may have begun around 3.0 -2.0 Ga.