Chemical character and structure of uraniferous bitumens (Vrchlabí, Czech Republic)

0566957 - ÚSMH 2023 RIV NL eng J - Journal Article
Machovič, Vladimír - Havelcová, Martina - Lapčák, L. - Mizera, Jiří - Sýkorová, Ivana
Chemical character and structure of uraniferous bitumens (Vrchlabí, Czech Republic).
International Journal of Coal Geology. Roč. 264, DEC 1 (2022), č. článku 104137. ISSN 0166-5162. E-ISSN 1872-7840
R&D Projects: GA ČR(CZ) GA19-05360S
Institutional support: RVO:67985891
Keywords : Bitumen * Halos * Micro-ATR-FTIR mapping * Radiolytic alteration * Uranium
OECD category: Geology
Impact factor: 5.6, year: 2022
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0166516222002130?via%3Dihub

Black shales from the Permian rocks at Vrchlabí in the Krkonoše Piedmont Basin (Czech Republic) contain bitumens with uraninite grain inclusions and bulk uranium concentrations up to 4.8 wt%, determined by instrumental neutron activation analysis. The carbonaceous matter in the bitumens has been characterised by gas chromatography/mass spectrometry, attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, and stable carbon isotopic composition. Progressive radiolytic alteration was documented by changes in the chemical composition and structure of both bulk samples and on the microscale. Condensation of aromatic structures, increase in content of oxygenated compounds, and enrichment in 13C were documented in the uranium-rich bulk samples. Micro-ATR-FTIR area mapping throughout the bright halos around uraninite inclusions revealed detailed structural changes, particularly a decrease in aliphatic bond intensities and an increase in the aromaticity of the structures close to the inclusions. A radiolytic alteration pathway has been suggested assuming a complex of reactions between organic matter and uranyl containing hydrothermal solutions, and oxidation by OH radicals produced in radiolysis of water. The organic matter transformations observed in the uraniferous bitumen correspond to the coalification processes, changing the bitumen composition from type I to type III and IV kerogens. Detailed characterisation of the radiation-induced chemical and structural changes in the naturally occurring uraniferous bitumens will contribute to the general understanding of the nature and behaviour of organic matter in other uraniferous environments or in the radioactive waste repositories.
Permanent Link: https://hdl.handle.net/11104/0341165