Pre-Jurassic tectonic evolution of the central part of West Siberian basin: the new data from the Frolov-Krasnoleninsky region

The basement of West Siberian plate has mosaic architecture and consists of the Paleozoic fold belts and supposed Precambrian massifs. The Frolov-Krasnoleninsky region is located in the central part of the West Siberian basin (near the town of Khanty-Mansiysk) and occupies the key position in its structure.  The junction of the Uralian fold belt, Kazakhstan superterrane, and Irtysh-Zaysan fold zone is located there. However, the pre-Jurassic tectonic evolution of this area is still poorly constrained. Based on the new representative data on drill cores from deep boreholes and geophysical data, whole-rock geochemistry and U-Pb ages, we reconstructed the main stages of the geological history of this area:

• In the Neoprotertozoic the ancient metamorphic complexes of the Krasnoleninsky and Aprel’sky uplifts were formed. Based on the detrital zircons ages and correlation with similar rocks in the nearby fold belts, we suggest that this stage terminated about 600-540 Ma.
• In the Early Paleozoic volcano-terrigenous rocks were accumulated mainly in the island arc tectonic setting. This stage ended with the emplacement of gabbro-granitic plutons, fold deformations and amalgamation of the Kazakhatan superterrane with the Krasnoleninsky block in the beginning of Silurian (446-440 Ma).
• In the Devonian – Early Carboniferous carbonate and overlying mainly clastic sediments were accumulated. The first manifestation of supra-subduction volcanic activity and granitic intrusions are identified as Late Devonian-Early Carboniferous. At the end of Early – beginning of Middle Carboniferous fold deformations related to the closing of back-arc basin took place.
• In the Middle – Late Carboniferous differentiated volcanic series and coeval granodiorite massifs of the continental arc tectonic setting were formed (310-307 Ma). This stage corresponds to the convergence of continental masses of Siberian and East European platforms and Kazakhstan superterrane and the closing of relic oceanic basins between them.
• The Early-Middle Permian is a time of collision, manifested by large granitic plutons in the Krasnoleninsky uplift and other areas of the West Siberia and Uralian fold belt (290-260 Ma). At this stage, main structural features of the basement of West Siberian plate were formed.
• In the Late Permian – Early Triassic West Siberia was an area of wide-scale rifting, caused by the post-collisional extension and the mantle plume ascent. Thick sequences of the contrasting basaltic and felsic lavas were erupted. Volcanic piles are overlain by clastic coal-bearing sediments of the Triassic and, possibly, Early Jurassic age.