Home – Home – Jornals – Russian Geology and Geophysics 2004 number 7

This paper is concerned with oils from Upper Precambrian and Lower Cambrian deposits of the Baikit, Katanga, and Nepa-Botuobiyan petroliferous areas (PA) and organic matter (OM) from the Upper Precambrian oil source formations of the Baikit PA, Yenisei Range, and Patom Upland. The studied oils are shown to be similar in some parameters to oils of the Huqf basin (Oman) and differ from oils of the McArthur basin (Australia), from some oils of Precambrian basins of the East European Platform, and from Phanerozoic oils. In southern East Siberia, oils are subdivided into two families according to their contents of sulfur and 12- and 13-methylalkanes, cholestane/ethylcholestane and Hh₃₄/Hh₃₅ homohopane ratios, and isotopic compositions of carbon. One family is localized in the Riphean deposits of the Baikit anteclise, and the other, in the Vendian and Lower Cambrian deposits of the Nepa-Botuobiyan anteclise and Katanga saddle. The existence of two oil families evidences different compositions, accumulation conditions, and diagenesis settings of OM in Riphean ecological niches on the Siberian craton.
Study was also given to the OM of Upper Precambrian oil source formations in the Yenisei-Baikit and Baikal-Patom zones of naphthide generation, which might have been the source of modern hydrocarbon pools in the Baikit and Nepa-Botuobiyan anteclises. In zones of moderate catagenesis, the OM, like the Upper Proterozoic and Lower Cambrian oils of the central Lena-Tunguska PA, is enriched in ¹²C. Comparison of the compositions of steranes in oils from the Baikit PA and in few bitumen samples from the Shuntara, Madra, and Iremeken Formations of the Yenisei-Baikit zone of naphthide generation showed that these hydrocarbons are of different genesis. The deposits of the Yenisei-Baikit zone were intensely transformed under the thermal effect, which hampers study of their OM bitumens. Therefore, the conclusion about the absence of OM-oil relationship drawn for single samples cannot be extended to all thick strata of the Yenisei Range.