Vol 21, (1984)
Vol 21, (1984)
- Details
- Category: Vol 21, (1984)
Authors: Milan Doležal & Ctirad Schejbal
Full version (9,744 kB)Abstract: The geologic-exploration works, carried out by Uranium Survey, Liberec in the region described, confirm the prediction of new uranium occurrences, which are distinct of those mined formerly. The attention is focused on prospecting for deposits with metasomatic ore mineralization in central Bohemian pluton, on the one hand and stratiform-type deposits in its surroundings, on the other hand. To the first ones belong the Nahošín and Mečichov occurrences located east of the Horažďovice. They are predominantly bound on the north-southern fault structures accompanied by NE-SW and NW-SE fractures, occurring in the vicinity of older up to ten meters thick shear zones trending to E-W. Around the N-S and NE-SW faults the aureole of hydrothermal alterations is developed accompanying the metasomatic uranium mineralization of silicate character. The alterations are mainly represented by chloritization, hematitization, pyritization, carbonatization and feldspathization. In the depth the ore mineralization is represented by coffinite mainly; within supergene zone uraninite, sooty pitchblende, exceptionally uranophane with cuprosklodowskite and meta-autunite appear. Similarly, as in the Vítkov II deposit in the Bor massif the ore mineralization is of disseminated to fine-dispersed character with combination of microfracture filling in form of veinlets. The present exploration results enable to project here the mining exploration works. Distinct are the features of the second type of the above-mentioned deposits which is bound on north-western exocontact of the Klatovy apophyse. In the Struhadlo locality, situated west of the Klatovy in variegated and metamorphic spilite zone, uranium mineralization is bound on series of strata of graphitic shales, quartzites, spilites, their tuffs and tuffites, as well as limestones metamorphosed in facies of green schists to albite-epidote amphibolites. In quartz graphitic shales and silicites, being affected by directional fault tectonics, uranium mineralization forms the conformable submicroscopic dispersions, irregular streaks or contrast veinlets. Besides uraninite also sulphides (pyrite, pyrhotine, sphalerite rich in high Cd content, chalcopyrite, arsenopyrite] are abundant. Of similar character are also the new U-mineralization occurrences near the Novotniky village, situated west of the Nepomuk. They appear in the vicinity of the prospect described in the foregoing. In volcano-sedimentary series of strata the uranium mineralization of apparent thickness, attaining several metres and containing great amounts of V [0.1-1 % ] and Mo (to 0.2 % ] has been found by boreholes. These intervals are bound on beds of grey to dark silicites in biotite hornfels. The two last occurrences, undoubtedly, represent a new interesting type of ore mineralization not only for the Horažďovice and Klatovy regions but for the entire Czech Massif. However, it will be necessary to evaluate its economic importance.
