Permo-Triassic stage of alkaline magmatism in the Vitim plateau (western Transbaikalia)

Abstract We present results of geochronological ( 40 Ar- 39 Ar, U-Pb SHRIMP-II, and LA-ICP-MS) and geochemical studies of alkaline rocks of the Amalat, Sirikta, Tsipa, Pravyi Uligli, and Verkhnii Uligli massifs in the Vitim plateau (western Transbaikalia). The formation of the alkaline rocks and the accompanying albitization are dated at 261-242 Ma. The isotope inhomogeneity (ɛ Nd ( T ) = + 8.4 to -1.7) of the alkaline rocks indicates the heterogeneous composition of the source of their material, having a depleted component, an enriched juvenile metasomatic fluid, and a crustal substrate.