Lithochemisry of the weathering crust of the ferrous chert-shale formation on the Bolshetroizkoe deposit

The average compositions of main rock groups from Bolshetroitskoe iron ore deposit of Kursk magnetic anomaly, located 35 km southeastward from the Belgorod sity, were estimated. The benefits of this study are explained by the necessity of industrial development of Bolshetroitskoe deposit by the underground hydraulic mining methods, which require a reliable diagnostics of rock varieties, especially of highgrade iron ores. The latter composed thick Pre-Visean weathering crust on the substrate of Precambrian ferriferous-silica-shale formation (Kursk series with the age ca. 2 billion years) represented by jaspilites and Fe-shales. Based on more than 1000 analyses from 45 prospecting and exploratory boreholes, we determined 2 main groups of rocks: moderately ferriferous enclosing and associated rocks (including bauxites) and actually high-grade iron ores. Within these groups, we determined 12 clusters relating to main weathering crust lithotypes with the help of lithochemical modules: hydrolizatic (GM), alumosilicic (AM) and ferrous (FM).