Accessory minerals of Ti, Nb, Ta and W (rutile, columbite-tantalite, wolframite, titanite) have become valuable indicators of geochemical evolution in the terms Fe/Mn and Nb/Ta ratios particularly in magmatic rocks and in associated hydrothermal systems.The proposed project will be a contribution to understanding of compositional evolution, geochemical fractionation and enrichment of some economic elements (e.g., Nb, Ta, W) in the rocks such as leucocratic granites and associated rocks transitional between magmatic and hydrothermal stage, and hydrothermal veins, located particularly in the regions of Saxothuringicum, Moldanubian Zone and Bohemicum. Accessory minerals will also be utilized as indicators of subsequent hydrothermal overprint of the magmatic stage in some minerals and, moreover, as indicators of fluid activity (e.g., F, O₂) in the parent rock.