ORGANIC GEOCHEMISTRY OF PRECAMBRIAN PETRO LEUM SOURCE DEPOSITS (BY THE EXAMPLE OF THE SIBERIAN PLATFORM)

Nowadays the problems of Precambrian petroleum prospects attract great attention of scientists. Their solution favor progress in the theory of petroleum formation, on one hand, and enables substantiating the pr ospects of ancient strata within petroleum areas and increasing hydroc arbon reserves, on the other hand. Geochemistry of organic matter in L ate Proterozoic (Riphean, Vendian) deposits clearly demonstrates that biospheres of these epochs supplied organic matter (OM) to sedimentary basins, with its amount being close to the amount of OM fossilized in Phanerozoic deposits of different systems. The investigation of OM co ncentrations and regularities of its distribution in the Upper Protero zoic deposits of the Siberian Platform and adjacent folded structures shows that contemporary residual organic carbon there constitutes abou t 64% of its total amount concentrated in the Riphean-Devonian deposit s. The Riphean dark-shale dominikoid deposits abundant within the stru ctures adjacent to the platform and, to a lesser degree, in its inner parts are most enriched in OM. The available data show that the Riphea n deposits of the Siberian and Russian Platforms are similar in the co ncentrations and distribution of OM. Calculations of petroleum formati on intensity for the Lena-Tunguska Province (Siberian Platform) have s hown that the Riphean deposits produced about 80% of liquid hydrocarbo ns (HC) and more than 90% of gas ones of.their total amounts in the se dimentary cover of the province. Thus, in the context of balance calcu lations, the Riphean deposits were principal HC-supplying strata in th e Lena-Tunguska Province. At the same time, numerous literature data o n relict hydrocarbons (biomarkers) indicate that the problem of geneti c correlation between oils and oil source rocks of the ancient Siberia n Platform strata is still unsolved.