PROVENANCE OF CARBONIFEROUS CLASTIC DEPOSITS IN THE CENTRAL PART VOLGA-URAL PETROLEUM PROVINCE (REPUBLIC OF TATARSTAN) REVEALED BY PETROGRAPHY AND U-PB (LA-ICP-MS) DETRITAL ZIRCON ISOTOPIC DATA

This study presents the results of an integrated petrographic and U-Pb geochronological investigation of Lower to Middle Carboniferous sandstones from the Volga-Ural petroleum province. The samples were obtained from drill cores collected in the South Tatar Arch and the northeastern flank of the Melekess Depression. The combined data reveal distinct provenance signatures for the Lower and Middle Carboniferous units. The Lower Carboniferous sandstones are characterized by a monomictic composition, dominated by well-rounded quartz grains. The heavy mineral assemblage consists primarily of ultra-stable minerals such as rutile, anatase, and zircon. U-Pb (LA-ICP-MS) dating of detrital zircons indicates a dominant Proterozoic age population, suggesting source areas associated with the Sveconorwegian and Svecofenian orogenic belts. In contrast, the Middle Carboniferous sandstones display a polymictic composition, comprising quartz, feldspar, and lithic fragments with moderate grain rounding. The heavy mineral suite is more diverse and includes both stable (rutile, anatase, zircon, spinel, garnet) and less stable minerals (biotite, amphibole, epidote). U-Pb geochronology reveals a dominant Paleozoic detrital zircon population, pointing to the Uralian orogen as the primary sediment source.