Reconstructed Upper-mantle Heterogeneity Domains in the Southwest Pacific since the Cenozoic

Upper mantle heterogeneity is the consequence of mantle differentiation throughout the Earth’s history, driven by material transportation within the upper mantle and across the planet’s surface to the lower mantle. The resulting heterogenic domains likely evolved through time, reflecting the dynamic mantle evolution in deep time. Previous studies mainly relied on present-day basalts (e.g., MORB and OIB) to understand the upper mantle heterogeneity (e.g., O’Nions et al., 1980; Stracke et al., 2005, 2022; Yang et al., 2021). However, the spatiotemporal evolution of ancient mantle heterogeneity remains poorly constrained.

In this study, we developed a technique to reconstruct upper-mantle domains back in time by restoring the basalts and published Pb isotopic ratios to their eruption locations using multiple plate reconstruction models including Müller et al. (2019). We test the new technique in the Southwest Pacific region, reconstructing the Zealandia-Antarctic geochemical domain and its boundary with the adjacent Pacific and Indian domains in the past ~60 Ma.