The cooling models of Earth’s early mantle

The thermal state of the early Earth’s interior and its way of cooling are crucial for its subsequent evolution. Earth is initially hot as it acquired enormous heat in response to violent processes during its formation, e.g., the Moon-forming giant impact, the segregation and formation of its metallic core, the tidal interaction with the early Moon, and the decay of radioactive elements, etc. In the meantime, the cooling mechanisms of early Earth’s mantle remain elusive despite their importance, and the previously proposed cooling models of the mantle are controversial. In this paper, we first reviewed several prevalent parameterized thermal evolution models of the early mantle. The models give unrealistic predictions since they were established solely based on a single tectonic regime, such as the stagnant-lid regime, or relied on the disputable existence of the plate tectonics prior to ~ 3.5 Ga. Then we argue that the mantle should have started to cool down from a very hot state after the solidification of the ferocious magma ocean. Instead of using one single scaling law to describe a single-stage model, we suggest that an episodic multi-stage cooling model (EMCM) of the early mantle could be more plausible to account for the mantle’s early cooling process. The model reconciles with the fact that the mantle cools down from a hot state prior to ~ 3.5 Ga and can also explain the well-constrained post-3.5 Ga thermal history of the mantle.