GEOLOGICAL AND MAGMATIC EVOLUTION OF THE LATE MESOZOIC-CENOZOIC INTRAPLATE VOLCANIC PROVINCE OF CENTRAL ASIA AS A RESULT OF PLUME-LITHOSPHERIC INTERACTION
YARMOLYUK V.V.1, KOZLOVSKY A.M.1, SAVATENKOV V.M.2
1Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian Academy of Sciences, Moscow, Russia
2Institute of Precambrian Geology and Geochronology RAS, St. Petersburg, Russia
Keywords: intraplate magmatism, basic rocks, Central Asia, rare elements, Sr–Nd–Pb isotopic composition, mantle plumes, plume-lithosphere interaction.
Abstract
The Late Mesozoic – Cenozoic intraplate volcanic province of Central and Asia unites a number of spatially isolated volcanic regions. Three periods of activity are distinguished in the history of its development. The initial period (between ~145 and 100 million years ago) was characterized by a regional extension and riftogenic magmatism. The middle period (between 100 and 30 million years) was distinguished by a subplatform tectonic regime and an areal type of volcanism. The late period (the last 30 million years) is distinguished as a period of volcanic plateau.
The magmatism of the province is determined primarily by alkaline basic rocks.. During the rift period, trachybasalts and trachyandesites were formed, the geochemical feature of which was high REE contents with low Nb and Ta contents. During the period of areal volcanism, trachybasalts and alkaline basaltoids with OIB characteristics became predominant.
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 magmatism sources were estimated. It was shown that at all stages of the province development, one of the components of the magma source 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 at the beginning of the Late Mesozoic, primarily with the activity of the Pacific superplume.
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