Выпуск: 10 , Том: 37 , Год издания: 1996

Mineral and chemical compositions of flood basalts of tuff lava suites of the core in the Tunguska Syneclise have been studied. Weak variations in contents of petrogenetic and many trace elements have been established for the basalts within both suites and within the region as a whole. The majority of the specimens (89) belong to the tholeiite series (low-K quartz- and olivine tholeiites) and their compositions form compact trends on petrochemical diagrams. There is a stable trend to an increase in the basalt depletion degree from early to late series. However, according to absolute contents of incoherent elements this depletion does not reach the level of MORB, which suggests the formation of primordial magmas of the basalts within the subcontinental lithosphere. Comparative geochemical analysis of volcanites of the central and northwestern parts of the Tunguska Syneclise suggests that it is quite reasonable to refer the basalts of the area to the third, final, stage of the Permo-Triassic magmatism of the Siberian Platform. The absence of more alkaline volcanites from the earlier stages is explained by some remoteness of the syneclise center from linear rift structures, to which they are spatially related.