Owing to the association with diamonds, eclogite xenoliths have samples were derived from typical depleted mantle. However, two groups of three samples each indicate both enriched mantle and received disproportionate attention given their low abundance in kimberlites. Several hypotheses have been advanced for the origin of possible ultra-depleted mantle present beneath Yakutia during the late Archean and early Proterozoic. The vast majority of eclogites eclogite xenoliths, from the subduction and high-pressure melting of oceanic crust, to cumulates and liquids derived from the upper studied from the Obnazhennaya pipe also exhibit characteristics of mantle. We have amassed a comprehensive data set, including Group A eclogites and are probably derived directly from the mantle. majorand trace-element mineral chemistry, carbon isotopes in However, the eclogites from the Mir kimberlite are more typical of diamonds, and Rb–Sr, Sm–Nd, Re–Os, and oxygen isotopes in other eclogites world-wide and show convincing evidence of a recycled, ultrapure mineral and whole-rock splits from eclogites of the Udoceanic crustal affinity. We concur with the late Ted Ringwood achnaya kimberlite pipe, Yakutia, Russia. Furthermore, eclogites that eclogites can be formed in a variety of ways, both within the from two other Yakutian kimberlite pipes, Mir and Obnazhennaya, mantle and from oceanic crustal residues. have been studied in detail and offer contrasting images of eclogite protoliths. Relative to eclogites from southern Africa and other Yakutian localities, Udachnaya eclogites are notable in the absence of chemical zoning in mineral grains, as well as the degree of light