Bilateral Loa-Kea trends of the Hawaiian Islands caused by the bottom-up splitting of plume conduit

Abstract

The Hawaiian-Emperor chain has exhibited two distinct Loa-Kea magmatic groups over the past 8 million years, but their origin remains debated. Using paleographically constrained global mantle convection models, we reproduce the present-day location of the Hawaiian hot spot and the associated spatiotemporal geochemical evolution. The composition of the plume conduit shows conventional concentric zoning prior to the Hawaiian-Emperor Bend and gradually evolves to a north-south bilateral zoning pattern afterward, corresponding to the subparallel Loa-Kea trends. Further analysis suggests that the plume originates from ridges of large low-velocity province (LLVP) induced by the push of slabs. Upwelling at the intersections of ridges is more energetic than at the middle of the ridge, causing bottom-up splitting of plume conduit in the lower mantle that propagates upward, forming bilateral zoning and eventually two independent plumes. This process suggests that bilateral zoning is transient and more common in the Pacific than Africa due to the circum-Pacific subduction.