ORGANIC GEOCHEMISTRY OF SEDIMENTARY URANIUM ORE-DEPOSITS

In many sedimentary uranium deposits, close relationships between uran ium and organic matter can be observed. They may be statistical, spati al or chemical. Such relationships entitle the organic matter to be co nsidered as an accurate marker of the history of uranium deposits. Geo chemical analyses of organic matter in uranium deposits often allow th e paleoenvironment, the thermal history as well as the different oxida tion-reduction processes involved during the diagenesis of the ore to be reconstructed. Routine techniques such as C-H-O analysis, Rock-Eval pyrolysis, gas chromatography (GC) or infrared spectroscopy provide b asic data that facilitate the characterization of organic matter: Howe ver, sophisticated analytical tools (GC-mass spectrometry, microspectr oscopic techniques, C-13 nuclear magnetic resonance, kinetic modelling ) may be required in order to obtain more detailed information on the complex behaviour of organic matter associated with uranium deposits. Data concerning various uranium deposits are presented with special em phasis on the determination of the origin and the maturation of organi c matter as well as the alteration processes involved in its diageneti c history.