Kimberlite magmatism fed by upwelling above mobile basal mantle structures

Most diamonds have been transported to Earth’s surface from depths between ~120 km and ~660 km by volatile-rich magmas called kimberlites. The reconstructed locations of kimberlites erupted in the past 320 million years have been shown to be correlated with seismically imaged large basal mantle structures at ~2,800 km depth. This correlation has been interpreted as requiring basal mantle structures to be stationary over time. However, the geodynamic process responsible for this correlation remains to be identified. Here we use global mantle convection models including a basal layer of dense material and driven by surface plate motions to show that broad mantle upwelling preferentially occurring above basal mantle structures provides the source of heat for kimberlite magmatism. We find that kimberlite eruption locations are statistically as correlated with the mobile basal mantle structures predicted by our models as those imaged by tomographic models, indicating that there is no need to consider basal mantle structures to be stationary. Our models indicate that deep mantle material is carried to the surface by mantle plumes, which is consistent with the geochemical signature of some kimberlites.