COMPARATIVE ANALYSIS OF GEODYNAMIC SETTINGS OF THE PERMO-TRIASSIC MAGMATISM IN EAST SIBERIA AND WEST SIBERIA Available to Purchase

A comparative analysis of the chemical composition of Permo-Triassic volcanic rocks from the Siberian Platform and pre-Jurassic basement of the West-Siberian Plate was performed to elucidate the geodynamics of magmatism in these regions. Two nearly synchronous stages of magmatism (rifting and flood) have been established on the Siberian Platform. The rocks that formed at the first stage are a differentiated series of basalts of elevated alkalinity; they occur in the paleorift structures of the northwestern and northern framings of the Tunguska Syneclise. Volcanic rocks of the second stage, an undifferentiated series of low-K tholeiites, are common throughout the lava plateau. When volcanic rocks of both stages are present in the same section, the rocks of the first stage occupy the lower and middle parts of stratigraphic columns. The first systematic data on the composition of Permo-Triassic volcanic rocks from the pre-Jurassic basement of the West-Siberian Plate have shown that the most widespread rocks – tholeiitic and subalkalic basalts – are similar in geochemical composition to the rift-stage rocks of the Siberian Platform. The basement contains acid effusive rocks (rhyodacites and rhyolites), volcanic rocks of the shoshonite-latite series, and a rift system, which completed its development in the Triassic. All this suggests taphrogenic magmatism in the region. The geodynamics of magmatic activity in both regions is interpreted in terms of plume tectonics and related rifting with regard for the different thicknesses of lithosphere blocks in East Siberia and West Siberia and the kinematics of movement of the consolidated Eurasian Plate at the Permo-Triassic boundary.