Geology and Petrography of Uraniferous Bitumens in Permo-Carboniferous Sediments (Vrchlabi, Czech Republic)

0558292 - ÚJF 2023 RIV CH eng J - Journal Article
Havelcová, M. - Sýkorová, I. - Rene, M. - Mizera, Jiří - Coubal, M. - Machovič, V. - Strunga, Vladimír - Goliáš, V.
Geology and Petrography of Uraniferous Bitumens in Permo-Carboniferous Sediments (Vrchlabi, Czech Republic).
Minerals. Roč. 12, č. 5 (2022), č. článku 544. E-ISSN 2075-163X
Research Infrastructure: CANAM II - 90056
Institutional support: RVO:61389005
Keywords : uraninite * bitumen * halos * bireflectance * radiolytic alteration
OECD category: Analytical chemistry
Impact factor: 2.5, year: 2022
Method of publishing: Open access
https://doi.org/10.3390/min12050544

Uraniferous bitumens found in black shales from the Permian rocks at Vrchlabi in the Krkonose Piedmont Basin (Czech Republic) were described and characterized petrologically and mineralogically. The Permian sediments originated from weathering products in metasediments and granitoids of the Krkonose-Jizera and Orlice-Sneznik crystalline complexes. The organic matter contained up to 4.8 wt.% uranium, as uraninite grains. Elements associated with uraninite, such as Pb, Zr, Cu, and As, may have accumulated from epigenetic fluids in layers rich in organic matter during their late diagenesis. The bitumen structures were extremely heterogeneous, a feature attributed to the radiolytic effects of uranium. Amorphous bitumens, alternating with various forms of nodular and corroded bitumen types from multiple generations, were present. Low and highly altered bitumens with weak anisotropy were recognized, together with halo zones, with reflectance up to 4.37%. The halo zones differed in size, brightness, and reflectance, increasing from the edge to the center. Halos often revealed dark rims between uraninite inclusions and clear zones, originating probably as a result of weaker alterations in organic matter due to the presence of other inorganic components. Uranium concentration was the main factor controlling the degree of radiolytic alteration. The studied uraniferous bitumens are an excellent example of multistage formation and diverse evolution during burial and diagenesis.
Permanent Link: http://hdl.handle.net/11104/0332022