Home – Home – Jornals – Russian Geology and Geophysics 2005 number 9

Studies of the Emeishan and Siberian trap provinces have demonstrated abundance of basalt series and giant volumes of lavas and sills (~16 · 10⁶ km³) formed for a very short period of the major step of volcanism. The obtained data permit a model for superplumes with three steps of their formation: early (picrites and alkali basalts), major (tholeiite plateau basalts), and final (ultrabasic and alkaline intrusions). These steps reflect the evolution of a superplume from several independent plumes until the formation of thick lenses of mantle melts at the bottom of the lithosphere and, finally, plumes of differentiated mantle melts. Synchronous syenite-granite intrusions and bimodal volcanic series abundant in the framing of the Siberian traps are the result of melting of the lower crust at depths of 65-70 km under the effect of plume melts. Superplumes promoted the synchronization of events of magmatism and geologic processes repeated at intervals of 30 and 120 Myr. A similar synchronization of global geological events is observed during the activity of superplumes 120, 250 and, possibly, 360 and 480 Ma. During the effusion and intrusion of (8-16) · 10⁶ km³ of volcanic material for a short interval of 0.6-2 Myr, huge volumes of CO₂, SO₂, and HF might have been released, capable to destroy the atmospheric system, to disturb the budget of oxygen-free oceanic water, and to lead to the mass extinction of living organisms at the Permian-Triassic boundary.