An emerging plume head at Hawaii

Abstract

The Hawaii-Emperor seamount chain showed two sub-parallel geographical and geochemical volcanic trends since ~5 Ma, the Loa and Kea trends, regarding which numerous models have been proposed that usually involved a single mantle plume sampling different compositional sources of the deep or shallow mantle. However, the eruption rate of the Hawaiian plume also dramatically increased since ~5 Ma. Moreover, this was accompanied by nearly simultaneous southward bending of the Hawaiian chain. Here, we propose a plume-plume interaction model, where the Kea trend represents the original Hawaiian plume tail, and the Loa trend represents an emerging plume head southeast of the original Hawaiian plume tail with enriched isotopic compositions. Geodynamic modeling suggests that the interaction between the emerging Loa plume head and the existing Hawaiian plume tail is responsible for the southward bending of the Hawaiian chain and the rapid growth of the eruption rate along the hotspot track. We suggest that this double-plume scenario also represents an important mechanism for the formation of other hotspot tracks in the Pacific plate, likely reflecting a dynamic reorganization of the lowermost mantle. It has implications to the formation of the LLSVP and mantle plumes in general.