Georesursy (Sep 2019)
Comparison of the contribution of differently depth geological processes in the formation of a trace elements characteristic of caustobiolites
Abstract
The article analyzes the correlation dependences between the logarithms of the concentrations of trace elements (TE) in various geochemical environments (oil, coal, fuel and black shales, as well as in clays, organic matter (OM) of various types and biota) in comparison with the average chemical composition of the upper, middle and lower continental crust. At the same time, along with the TE content of oils of the main oil and gas basins (OGB) – the Volga-Ural and West Siberian ones, the data on the TE content in the so-called young oils were summarized; as such, data on the oil fields of the West Kamchatka oil and gas field and oil manifestations in the area of the caldera of the Uzon volcano were used. Particular attention was also paid to the results of the analysis of the TE composition of the oils of the Romashkino group of fields, as it is possible that they are subject to the influence of deep-seated processes. The correlation coefficients between the studied parameters for the various studied oil- and gas-generating basins, including for the Romashkino group of fields, turned out to be close. For all oils, except for the young oils of Kamchatka and the caldera of the Uzon volcano, a closer connection of their TE composition with the TE composition of the lower crust was revealed. For young oils of the Uzon caldera in Kamchatka, this trend is absent, and a slightly closer relationship is revealed with the average composition of the upper but not lower crust, while for statistically more reliable data on the TE composition of the hydrothermal waters of the caldera of the Uzon volcano, a significantly closer relationship is observed with the average chemical composition of the middle and upper crust. Based on the identified correlations between the TE compositions of oil, caustobioliths and the crust of different levels, conclusions are made about the likely relationship between biogenic and deep processes in the formation of oil and gas fields. According to the authors, the obtained results support the crucially important role in the processes of naphthidogenesis of the upward flows of the low crustal fluids with the dominant source of hydrocarbons from the initial OM of sedimentary basins.
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