Tectogenesis as a factor influencing the stability of rock masses of the Northern iron ore district of the Kryvbas

In the Northern iron-ore district of the Kryvbas basin, mining of deposits of poor magnetic ores is underway in two quarries – Pervomaiskyi and Hannivsky. Oftentimes, their mine contours contain low-valuable or unusable magnetite-silicaceous quarzites of containing ferrous and slate horizons. As a result, excavated ore mass contains ores and partly containing rocks of various mineral and chemical compositions and physical and technical properties. This caused diversity (15 mineral kinds) of the compositions of ores mined from the both deposits. Variability of mineral compositions of ores and rocks is due to manifesta- tions of numerous geological processes such as sedimentation, metamorphism, tectogenesis, metasomatism, supergene, etc. Various mineralogical, geochemical courses of the processes resulted in variability in physical, technical characteristics of ores and containing rocks, and this, in turn, caused various stability of rock masses during drilling-explosive works and mining. Stability of pit walls of the quarries of iron-ore deposits of the Kryvyi Rih basin is a sharp issue for mining enterprises. Solutions to those issues have been analyzed in various aspects. A number of factors take effects on the indicator of stability of rock masses within deposits, particularly mineralogical, geochemical, tectonic, etc. This paper looks at the influence of the tectonic factor specifically, which actively manifests within the Pervomayskyi and Hannivskyi deposits as fractures, breccias, mylonite of ores and rocks. During the surveys, there were designated tectonically altered kinds of ores and rocks within the both deposits, which take effects on seismic stability of pit walls of the both quarries, and also we put areas with various tectonic intensities on schematic maps. For this purpose, we used geological methods of study (selection of samples, mapping), mineralogical (determining quantitative proportions of minerals, texture, structure of ores and rocks). The study provides the data of mineralogical estimates of tectonically altered types of ores and rocks of productive layers of the Pervomaiskyi and Hannivskyi deposits of the Kryvyi Rih basin. We charted maps with areas of various manifestations of tectonic changes within productive layers of the both deposits.