The association of Hawaiian-Emperor volcanism with a large-scale central Pacific anisotropy anomaly at ~150 km depth can be explained by tapping of shallow melt sources in a perisphere/LLAMA (layer of lateral advection of mass and anisotropy) model. The origin of the anisotropy anomaly can be traced to the formation of a phlogopite-garnet-pyroxenite assemblage in the perisphere beneath an island arc on the Stikine terrane of the North American Cordillera in the Carboniferous. The pyroxenites were formed when subduction-related melts invaded the mantle wedge at ~150–200 km depth. The enriched region inherited the thermal profile of the mantle wedge, along with...