Role of Magma Ocean Differentiation in the Formation and Long‐Term Preservation of Distinct Geochemical Domains Within the Deep Mantle

Abstract We modeled the evolution of the terrestrial Magma Ocean using the short‐lived 182 Hf‐ 182 W isotope system ( t 1/2 = 8.9 Myr) in a multi‐reservoir early Earth. We start with a chondritic Earth at T 0 = 4.567 Ga. Core segregates and attains its present‐day mass, W elemental and isotopic ( 182 W/ 184 W) composition by the end of core formation ( T CF ). The duration and rate of core formation constrain the starting composition of the silicate Earth and magma ocean that formed at the last stages of the core formation. Crystallization of magma ocean results in the formation of crystals/cumulates of mass M CX , leaving behind a residue with mass M RES . A series of differential equations describing the changing mass and abundance of 182 Hf, 182 W, and 184 W nuclides in each reservoir are solved numerically at 0.1 Myr time‐step for the initial 200 Myr of Earth's history. Our results constrain the depth of the early magma ocean to be ∼38–70% of the total mantle mass, corresponding to a depth of ∼770–1,600 km and the timing of magma ocean crystallization over a duration T CX of ≤50 Myr after core formation, which successfully reproduces the present‐day Hf and W concentrations and 182 W/ 184 W ratios in M RES reservoir similar to the deep mantle sources sampled by ocean island basalts. The model‐derived results suggest that leftover residual (liquid) magma ocean after magma ocean crystallization could partly or fully represent the present‐day large low shear velocity provinces, LLSVPs.