TECTONIC AND MAGMATIC EVOLUTION OF THE LATE MESOZOIC–CENOZOIC INTRAPLATE VOLCANIC PROVINCE OF CENTRAL ASIA AS A RESULT OF PLUME-LITHOSPHERIC INTERACTION

The late Mesozoic–Cenozoic intraplate volcanic province of Central Asia unites a number of spatially isolated volcanic regions. Based on the examples of the South-Khangai, West-Transbaikal, and East-Mongolian regions, we demonstrate that three periods of activity can be distinguished in the province’s geological history. The initial period (between ~145 and 100 Ma) was characterized by a regional extension and riftogenic magmatism. The middle period (between 100 and 30 Ma) was distinguished by a quasi-platform tectonic regime and an areal type of volcanism. The late period (the last 30 million years) is distinguished as a period of lava plateau volcanism. The magmatism of the province is determined primarily by mafic rocks with elevated alkalinity. During the riftogenic period, trachybasalts and trachybasaltic andesites were formed, the geochemical signature of which was high REE contents with depleted concentrations of Nb and Ta. During the period of areal volcanism, trachybasalts and alkaline basaltoids with OIB characteristics became predominant. This rock type remains dominant in the volcanic associations of the final period of the province’s formation. The trends in variations of trace elements and the isotopic composition of Sr, Nd, Pb in mafic rocks of different ages in the province were determined and the compositions of their magmatic sources were estimated. We show that at all stages of the province development, one of the magma sourcecomponents remained constant and was close to the asthenospheric mantle of the EMORB type. During the rift period, subduction-metasomatized mantle also participated in magmatism. During the period of areal volcanism, the metasomatized mantle was gradually removed from the composition of melt sources. Since that time, the magmatism of the province has been determined by the interaction of asthenospheric, plume (OIB-type) and depleted lithospheric mantles. The formation of the province is associated with the emergence of a hot mantle field at the base of the East Asian lithosphere. Its origin is consistent with the activation of deep geodynamic processes in the early late Mesozoic, primarily with the activity of the Pacific superplume.