Structure and Geochemical Features of the Volcanic Rocks in the Tunguska Syneclise (Siberian Trap Province)

Abstract

To understand the origin of the Siberian trap province, it is necessary to know its internal structure in detail. Only two areas were described, the Noril’sk and Maimecha-Kotuy, while the most important part of the province, the Tunguska syneclise, is still poorly characterized. The main goal of our study is an investigation of the structure and geochemistry of volcanic rocks located in the central part of the province. We have studied basalts and tuffs and compared them with the rocks of the Noril’sk area. All studied rocks belong to three formations: Korvunchansky, Nidymsky and Kochechumsky. The whole thickness of this cross-section is around 1,000 m. Our geochemical data demonstrate that the lower part of the cross-section comprises basalts with TiO2=1 wt% while the upper part consists of the basalts with the average TiO2 content 1.4-1.5wt%. Based on this data, these rocks can be correlated with Morongovsky and Mokulaevsky formations located in the Noril’sk area. Despite many similarities between the volcanic rocks of these two areas, the basalts and tuffs of the Tunguska syneclise have their specific features, i.e. many tuff horizons, small thickness of flows and their poikiloophitic structure that reflect the rock formation near the boundary of the Tunguska syneclise.