The data available indicate the complex evolution of deformed peridotites of mantle xenoliths, the P–T parameters of which indicate that they are fragments of the metasomatized lower part of the cratonic lithosphere. The zoning established in garnets from xenoliths in kimberlite pipes is interpreted as a result of metasomatism that occurred shortly before xenoliths reached the surface. Metasomatic alterations in xenoliths of deformed harzburgites were manifested not only in the development of zoning of minerals. The study results show that there is a discrepancy between the data calculated based on the contents of incompatible elements in minerals of xenoliths and those obtained due to direct measurements of the bulk composition of xenoliths. To determine the balance of incompatible elements, we have carried out experiments on leaching xenoliths of deformed lherzolites from the Udachnaya kimberlite pipe. It was established that a significant part of LREEs in the studied xenoliths occurs in the intergranular space. The distribution pattern of incompatible elements and, in particular, the presence of a positive Eu anomaly indicate that the appearance of the intergranular component is not associated with contamination of xenoliths by the kimberlite melt. Quite a few xenoliths demonstrate a positive Eu anomaly, which indicates the influence of the subducted crustal component at one of the modification stages of xenoliths.