6. Conclusion

The Bohemian Massif hosts a significant quantity of uranium deposits bound by brittle shear zones developed in high-grade metamorphic rocks (Rožná, Okrouhlá Radouň, Zadní Chodov and Dyleň) and/or granites of the Klenov and Bor plutons (Okrouhlá Radouň, Vítkov II and Lhota). The shear zone-hosted uranium deposits consist of peneconcordant lenses or highly disseminated uranium mineralisation evolved in brecciaed shear zones. The host rocks of these deposits are strongly altered, exhibiting extensive albitisation, chloritisation, hematitisation, and desilification in pre-ore stages. By hydrothermal alteration, aceites are products of lowtemperature alkaline metasomatism associated with a significant input of Na2O and the loss of SiO2. Complex coffinite-uraninite or coffinite-uraninite-brannerite assemblages form the shear zone mineralisation with predominance coffinite about uraninite. Mineralisation evolved in shear zone-hosted uranium deposits of the Bohemian Massif displays enrichment of HREE, Y and Zr in examined uranium minerals, especially in coffinite. For analysed coffinites and brannerites, enrichment of Y (up to 3.4 wt.% Y2O3) and Zr (up to 13.8 wt.% ZrO2) is significant.
