Geochemistry of organic matter of natural bitumen in the section of the Kozhva river (Timan-Pechora province)

Abstract

The results of detailed geochemical studies of natural bitumen in the section of the Kozhva River of the Timan-Pechora province, localized in the dolomites of the Kamensk formation of the Upper Famenian, are presented. It is established that bitumen is allochthonous. This is quite understandable from a geological point of view: the formation of bitumen manifestations is associated with the vertical migration of hydrocarbons (HC) in the zone of the Pripechorsky deep fault, resinous-asphaltene components predominate in the bitumen group composition. Gas chromatography and gas- chromatography-mass spectrometry proved that bitumen underwent intensive bacterial degradation, which led to the loss of n-alkanes and isoprenoids, steranes and partially hopanes. Tricyclanes of composition C19-C25, tetracyclane C24 and «geohopanes» with configuration 17α(H)21β(H) of composition C27 (Ts, Tm) and C29 were identified on mass chromatograms of m/z 191. It was found that tricyclanes predominate. On chromatograms according to m/z 177, 25-norhopane of the composition C28 was identified. Series 25-norhopane series was observed. The isotopic composition of carbon of individual fractions is characteristic of sapropel OM and is similar to the ICC of the previously studied bitumen of the Voya deposit.