Physicochemical Properties and Genesis of the Asphaltites of Orenburg Oblast

Resumo

In this article, the results of the studies of the physicochemical properties and genesis of asphaltites from the deposits of Orenburg oblast are considered. Based on the data of a study on the distribution of hydrocarbon biomarkers (n-alkanes, isoprenanes, steranes, and terpanes), it was found that deposit formation occurred in carbonate layers under reducing conditions. The distribution of steranes and terpanes confirmed a sufficient maturity of the asphaltite. The C₂₈/C₂₉ sterane ratio of 0.31 corresponds to Silurian age according to Grantham or to Silurian–Devon age according to the pregnane coefficient (a ratio of the sum of C₂₁–C₂₂ pregnanes to the sum of C₂₁–C₂₂ pregnanes and C₂₇–C₂₉ regular steranes) of 9.0%. Thus, it is likely that asphaltites from the Ivanovka deposit in Orenburg oblast were redeposited in Silurian/Devon source rock formations.