MAGNETITE- AND ILMENITE-SERIES OF GRANITIC ROCKS AND THEIR POTENTIAL NIOBIUM AND TANTALUM MINERALIZATION WITHIN THE UKRAINIAN SHIELD

The paper discusses differentiating between different types of granites that occur within the territory of the Ukrainian Shied. The classification in the article partly follows the principles formulated in the early taxonomies of granites, among which are the classifica-tions proposed by Ishihara [11], Chappel and White [4], and a lower classification proposed by Tomurko and Shcherbakov [20]. The latter made an attempt to single out two contrasting granite varieties ? apobasitic and apopelitic granites ? that are commonly foundwithin the Ukrainian Shield. Grouping granites into different genetic types runs into difficulties due to heterogeneous origin of these formations, which resultsfrom merging parental mantle with crustal sources. Nevertheless, such classification might be used in making an accurate predictionabout metallogenic specialization of different genetic types of granites. The redox state of granites formation is a major factor that can largely affect possible metal concentration in them. Based on this parameter granites can be classified into ilmenite and magnetite se-ries of granites, which differ in geological environment of their formation [6, 11] and mineralization associated with them [1]. Within the territory of the Ukrainian Shield there can be distinguished entire provinces with distinct distribution of mostly ilmenite or magnetite series of granites that reveal different ways of ore mineralization associated with them. Columbite-tantalites are common oreminerals found within these series of granites, with niobium and tantalum being characterised by close lithofillic affinity to these forma-tions. Within the Ukrainian Shield, columbite-tantalites were found in granites and associated rare-metal pegmatites, in some apogranitic metasomatites (greisens, quartzites, perthosites), and also in alkaline rocks of various origin. It is determined the basic features ofcolumbite-tantalites, with Та/Nb value, Fe/Mn ratio and presence of admixture elements to have close genetic relation to different granite series. The features of mineralization, defined to be typomorphic of ilmenite and magnetite series of granites, might be used to improvesurvey and exploration carried out in the Ukrainian Shield.