The role of melt depletion versus refertilization in the major element chemistry of four-phase spinel peridotite xenoliths

Mantle peridotites are interpreted as either residues after partial melting and melt extraction or products of igneous refertilization of refractory peridotites. The simple distinction between these models is difficult to assess because in chemical variation diagrams, both processes lead essentially to the same results. The only exception is the Ti-in-Cpx versus Ti-in-whole-rock plots, which can successfully discriminate between these models. In this study, a modified version of Ti-in-Cpx versus Mg#-in-olivine plots was applied to ∼1,500 spinel peridotite xenoliths from worldwide localities. The results showed that the vast majority of shallow mantle samples are consistent with the partial melting model; however, a minority of samples may indicate refertilization of formerly refractory mantle domains.