Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Retrograde-metamorphic and hydrothermal alterations at the Rožná uranium deposit
Abstract
The Rožná uranium deposit is located in cataclastites that were formed during ductile to brittle, Late Variscan shearing of high-grade metamorphosed Moldanubian rocks. The shearing was associated with a widespread chloritization of biotite and formation of white mica. Chloritized zones were later intruded by saline oxidized brines from Stephanian and Lower Permian sedimentary basins, that were capable to dissolve uranium from the host rock complex. Alteration of rocks by the oxidized brines resulted in the formation of hematite-enriched rocks. The brines were gradually reduced by Fe2+ -silicates (biotite, chlorite) and pyrite producing syn-ore alteration consisting mostly of Fe3+ -illite and hydro-oxides of iron. During the Triassic and Jurassic periods, tectonic and thermal reactivation of the Bohemian massif resulted in the formation of post-ore sulphide-barite-fluorite mineralization, argillitization of host rocks and local remobilization of uranium.
