Composition and Distribution of Microelements in Rocks, Extracts, and Asphaltenes from Domanik Deposits of Various Lithologo-Facial Types of Romashkino Oilfield

Abstract

Comparative studies were made of the microelement composition of rock samples from Domanik deposits of different lithologo-facial types: from Semiluki–Mendym (Domanik) deposits of the Berezovskaya area and from carbonate domanikoid deposits of the Dankovo–Lebedyan horizon of the Zelenogorskaya area of the Romashkino oilfield. These samples differ in the organic matter (OM) content and in the content and composition of petroleum hydrocarbons (HCs) and kerogen. Distinctive features of the composition and distribution of biogenic, rare earth, and radioactive microelements (MEs) in the initial rocks, rock extracts, and asphaltenes recovered from them were revealed. The Domanik carbonate–silica rock of the Berezovskaya area, in contrast to the carbonate rock of the Zelenogorskaya area, is characterized by diversity and high concentrations of all the ME groups with the highest content of V, Ti, Fe, Zn, Ni, Cu, Cr, Ba, Mo, and Mn. In the carbonate rock from domanikoid deposits of the Zelenogorskaya area, the concentration of these MEs is considerably lower, as well as the concentrations of rare earth and radioactive elements; the group of highly volatile chalcophilic MEs including Ge, Ga, As, Se, Cd, Sb, Te, Re, Hg, Tl, and Bi is virtually absent. Both types of rocks contain Sr. In the extracts and asphaltenes, V, Ni, Fe, and Zn are the most abundant MEs. The highest concentrations of V, Ni, and Zn were detected in carbenes and carboids of the Berezovskaya area. The ME composition suggests different conditions of the OM transformation and ME accumulation in rocks from Domanik deposits of different lithologo-facial types due to different intensity of the development of tectonic processes and supply of deep hydrothermal fluids into the deposit strata on the examined territory of the Romashkino oilfield.