Double volcanic tracks at Hawaii caused by bridgmanite-enriched primordial mantle blobs

Mantle plumes, rising from Earth's deep interior, are expected to produce a single age-progressive hotspot track. However, Hawaiian volcanoes younger than ~7 million years form two subparallel volcanic chains, the Loa and Kea trends. The mechanism behind this double-track volcanism and its connection to deep mantle reservoirs remain unresolved. Here we show that bridgmanite-enriched primordial mantle blobs (BPMBs) with intrinsic viscosities 10-30 times higher than the ambient mantle can generate bilaterally zoned plumes using three-dimensional thermochemical mantle plume models. Enhanced viscous heating within BPMBs raises plume temperatures asymmetrically, reproducing observed contrasts in isotopic composition, plume temperature, melt flux, and seismic velocity between the Loa and Kea trends. The global occurrence of similar double-track volcanism suggests that BPMBs are scattered within large low velocity provinces (LLVPs), likely remnants of an ancient basal magma ocean. Our results provide a mechanism for double-track volcanism and constraints on the structure and composition of LLVPs.