Kimberlite magmatism fed by upwelling above mobile basal mantle structures

Most diamonds have been transported to Earth's surface from depths between similar to 120 km and similar to 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 similar to 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. Volatile-rich kimberlite magmas may be transported to the surface by broad mantle upwellings located above mobile basal mantle structures, according to global models of mantle convection over the past 200 million years.

Automated summary

Most diamonds are transported to the Earth's surface from depths of around 120 km to 660 km by kimberlites, which are volatile-rich magmas. The locations where kimberlites erupted in the past 320 million years have been found to be related to large basal mantle structures at approximately 2,800 km depth as imaged by seismic imaging. Our global mantle convection models incorporating a basal layer of dense material driven by surface plate motions show that kimberlite magmatism is fueled by broad mantle upwellings occurring above basal mantle structures.