The two geochemical tracks in Hawaii (and as observed in many other plume related hotspot tracks) are thought to be related to some sort of heterogeneity in the mantle plume itself. As described in the recent review on mantle plumes by Koppers et al., 2021, there are three basic models to explain this:

1. An unzoned, but heterogeneous plume where the double tracks reflect different components with different melting temperatures.

2. A concentrically zoned plume with the hottest and densest portion of the plume material in the center.

3. A bilaterally zoned plume where one half of the plume is more a direct sampling of the source LLSVP and, since most plumes originate from the edge of LLSVPs at the core-mantle boundary, the other half incorporates more "ambient" mantle.

At present, the bilateral model is more favored as a general explanation, but it doesn't explain all of the observations of double tracks at all hotspots, so there may not be a single mechanism. Specific to Hawaii though, the bilateral plume model is the favored one (e.g., Williamson et al., 2019).