The West Transbaikal rift region was formed within continental setting in the Late Jurassic and was developed until the Early Cenozoic. The Udinsky sector is one of its central fragments and includes the Udinsky, Eravninsky and Zazinsky depressions. New studies of the Sr, Nd, Pb, O isotopic composition and geochemical signatures of Cretaceous basaltoids of each depression are given in this article and its allowed us to estimate the mantle and crustal sources compositions and propose the its mixing model. During the formation of volcanics of the Udinsky sector within the age range of ~ 143–71 MA, there was a consistent change in the isotopic parameters of the sources from enriched (EMI and EMII) to moderately depleted PREMA type. Early Cretaceous primary magmas were formed from mantle sources that included subduction-enriched mantle, which resulted in the depletion of basaltoids in Ta, Nb, Ti and in high (La/Ta) (2.2–4.9), (La/Nb) (2.1–4.2) and at the same time high contents of incompatible trace elements. Mantle magmas of the Uda depression were contaminated with lower crustal matter, which is characterized by moderate or reduced contents of Zr and La, low values of La/Yb, Rb/Sr compared to the composition of the basaltic melt. The compositions of the Eravninskaya and Zazinskaya depressions basaltoids reflect the mantle magmas interaction with upper crustal granitoids of the Angara-Vitim batholith. Mantle-crust interactions were least reflected in the composition of Late Cretaceous volcanics, the geochemical characteristics of which are consistent with the nature of changes in the isotopic compositions of mantle sources over time.
A.A. Vorontsov (2025) studied this question.