Can Kimberlites be generated from an ordinary mantle?

Kimberlites are characterized by a high concentration of incompatible elements, including light rare earths. However, Nd isotopic evidence indicates that their source regions do not have a long history of enrichment. If kimberlites can be generated from non-enriched mantle sources by simple partial melting processes, this implies that crystal-liquid partition coefficients for some trace elements are lower for kimberlitic liquids than for basalts or andesites. From a comparison of clinopyroxene megacrysts (regarded as equilibrated with kimberlite at depth) with existing kimberlite data we argue here that low crystal-liquid partition coefficients for the rare earths are plausible.