Geometry and Geochemistry of the Hawaiian–Emperor Seamount Chain reproduced by global plate-mantle coupling geodynamic models

The Hawaiian–Emperor Seamount Chain (HESC) is the longest volcanic island chain in the world, which is formed by the thermal erosion of the Pacific Plate by a hot mantle plume. The HESC has two major characteristics. First, it features an approximately 60° bend formed around 47 million years ago (Ma), giving rise to its distinctive geometry. Second, over the past ~2 million years (Myr), the HESC has developed into two sub-parallel Loa-Kea trends that exhibit markedly different incompatible element and isotopic signatures, resulting in its distinctive geochemical characteristics. The causes of the two features remain vigorously debated. Here, we use global-scale geodynamic models to investigate their formation mechanisms. We find that intra-oceanic subduction systems existed in the North Pacific from the Jurassic to the Eocene, exerting significant influences on Pacific Plate motion and the thermo-chemical evolution of the Hawaiian plume from its generation at the Large Low–Velocity Provinces (LLVPs), to its drift beneath the plate, and finally its structural evolution throughout the mantle.
We quantitatively resolve the relative contributions of Pacific Plate rotation and Hawaiian hotspot drift to the formation of the Hawaiian-Emperor Bend (HEB). We propose that the demise of the Kronotsky intra-oceanic subduction system was the primary driver of a major rotational reorganization of the Pacific Plate at ~47 Ma, which our numerical simulations quantify as a ~30° rotation. Using global mantle convection models, we successfully reproduce the slab structures, the basal thermochemical anomalies including the LLVPs and an intermediate-scale anomaly (the Kamchatka anomaly) beneath the northwestern Pacific, and more importantly the present-day location of the Hawaiian hotspot. Our model predicts a predominantly southwestward migration of hotspot over the past ~80 Myr. This hotspot trajectory is consistent with plate kinematic constraints, but differs substantially from those of earlier geodynamic models that predict a predominantly southward or southeastward hotspot motion. We find the westward component of the hotspot motion is crucial for the formation of HEB. Further analysis suggests that an Late Jurassic-Cretaceous intra-oceanic subduction system in the northeast Pacific provided the forcing necessary to drive this westward hotspot migration. Combined with modeled Pacific Plate motion, we have fully reproduced the observed ~60° HEB. Furthermore, subduction activity in the North Pacific influenced the structural evolution of the Hawaiian plume, triggering a bottom-up splitting of the plume conduit. This splitting generated internal material zoning, which is expressed at the surface as parallel Loa–Kea geochemical trends. These findings not only explain the geometry and geochemistry of the HESC, but also provide insights on the tectonic evolution of the North Pacific.