Rhenium and selenium in the Upper Jurassic shale of the “Gorodishchi” section, Central part of the Volga shale basin

Research subject . This article presents new data on the content of rhenium (Re), selenium (Se) and a number of other rare elements in the rocks of the Gorodishi section located in the Central part of the Volga basin shale (upper Jurassic) in the South-East of the Russian plate. In this section, rocks are rich in organic matter (15–37 % wt in oil shale) and contain layers of oil shale with a thickness of up to0.7 m. Materials and methods . The description and layer-by-layer testing of the Gorodishchi section was performed. Sulphides were isolated from two samples of carbonaceous shale for subsequent analysis. In the selected samples and isolated sulphides, the contents of Re, Se and a number of rare elements were determined at the VSEGEI central analytical laboratory. For the first time, the chemical composition of the samples was determined by ISP-MS using an Agilent 7700h device. Results. Oil shale samples demonstrated the highest concentration of Re and Se, with the concentration of Re and Se being on average 0.13 g/t (ranging from 0.09 to 0.19) and 10.39 g/t (from 6.54 to 12.4), respectively. A statistical analysis of the data obtained (using principal component factor analysis) revealed a close relationship of Re and Se both with the rock organic matter and with Cu, Cd, U, Ag. Conclusions . Anomalously high concentrations of Se and high concentrations of Re revealed in the oil shale of the section under study testifies to the need for specialized mineralogical and geochemical studies of the upper Jurassic carbon shale of the Central part of the Volga basin shale in terms of Re and Se content.