Chemical composition of Earth's primitive mantle and its variance: 2. Implications for global geodynamics

The global budgets of argon and heat‐producing elements have traditionally been used to argue for layered‐mantle convection because they require a large fraction of Earth's mantle to remain isolated from mantle convection. We revise these mass balance arguments using our new composition model of the primitive mantle and show that the global budgets of argon, heat‐producing elements, and rare earth elements are consistent with Earth's mantle almost entirely composed of the mid‐ocean ridge basalt source mantle, supporting the notion of whole mantle convection. Combined with a recent theory on the thermal evolution of Earth, our revised thermal budget implies inefficient mixing and processing in the past, explaining the survival of long‐lived geochemical heterogeneities in convecting mantle.