310 Ma and is spatially associated with several U deposits and occurrences. In the southern part of the Armorican Massif (French part of the EHB), the Guérande peraluminous leucogranite was emplaced in an extensional deformation zone at ca. Most of the hydrothermal uranium (U) deposits from the European Hercynian belt (EHB) are spatially associated with Carboniferous peraluminous leucogranites. 295 Ma (Carl et al., 1983 Dill, 2015 and reference therein) is synchronous with the emplacement of intragranitic uranium oxides bearing pegmatites in the Hagendorf-Pleystein province from 302.8 ± 1.9 Ma to 299 0.6 ± 1.9 Ma (Dill, 2015). In the western edge of the Bohemian Massif, the age of vein type deposits at ca. (2006) showed that the U ore originated from the leaching of the cupola of the Aue syeno-monzo-granite during the interaction with oxidizing hydrothermal fluids and that the reducing nature of the metasedimentary host rocks promoted the precipitation of U. For the Schlema and Schneebergs vein-type deposits (Bohemian Massif), Barsukov et al. Similarly, meteoric and basin derived fluids were involved during the genesis of the shear zone-hosted U mineralization of Okrouhlá Radouň and Rožná in the Bohemian Massif (Kříbek et al., 2009 Dolníček et al., 2013) and their mixing likely promoted the precipitation of the U leached out from the basement. (1990) proposed that in the Massif Central, the U deposition resulted from the mixing of two types of fluids: an oxidizing surface-derived aqueous fluid able to leach U from uranium oxides in the leucogranites and a reduced fluid with an inferred sedimentary origin. Regarding the genesis of these deposits, Turpin et al. The massive hydrothermal alteration of host rocks, as well as the high mobility of REE, Y and Zr indicate an influx of oxidised basinal fluids in the Permian to the crystalline rocks of the Moldanubian Zone. The high mobility of Y and Zr during formation of the uranium mineralisation is supported by the occurrence of Y- and Zr-rich coffinite However, this change is connected to the depletion of REE, as well as the enrichment of P and Th in the bulk. In Na and Ca while depleting K, Si, Rb and Ba. The alteration of high-grade metasediments has also led to an enrichment The alteration of leucogranites has caused enrichment in Na, Ca, Fe3+, Zr and the bulk of REE while depleting K, Fe2+, Si, Th, Rb and Ba. Metamorphic rocks in the Moldanubian Zone (Bohemian Massif).
The mobility of rare-earth elements (REE), Y and Zr during the Late-Variscan and post-Variscan mineralisation event in the Okrouhlá Radouň uranium deposit has been investigated to elucidate their behaviour during the hydrothermal alteration of leucogranites and high-grade
Pre-ore albitization was caused by circulation of alkaline, oxidized, and Na-rich playa fluids, whereas basinal/shield brines and meteoric water were more important during the post-ore stage of alteration. The available data suggest participation of three fluid endmembers of primarily surficial origin during alteration and mineralization at the deposit: (1) local meteoric water, (2) Na-Ca-Cl basinal brines or shield brines, (3) SO4-NO3-Cl-(H)CO3 playa-like fluids. The fluid inclusion and stable isotope data suggest low homogenization temperatures (̃50-140 ☌ during pre-ore albitization and post-ore carbonatization, up to 230 ☌ during pre-ore chloritization), variable fluid salinities (0-25 wt.% NaCl eq.), low fluid δ18O values (-10 to +2 ‰ V-SMOW), low fluid δ13C values (-9 to -15 ‰ V-PDB), and highly variable ionic composition of the aqueous fluids (especially Na/Ca, Br/Cl, I/Cl, SO4/Cl, NO3/Cl ratios). The subsequent fluid circulation led to precipitation of disseminated uraninite and coffinite, and later on, post-ore quartz and carbonate mineralization containing base metal sulfides. The pre-ore pervasive alteration of wall rocks is characterized by chloritization of mafic minerals, followed by albitization of feldspars and dissolution of quartz giving rise to episyenites. The Okrouhlá Radouň shear zone hosted uranium deposit is developed along the contact of Variscan granites and high-grade metasedimentary rocks of the Moldanubian Zone of the Bohemian Massif.