Oxyreactive Thermal Analysis (OTA) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) have been performed on highly
matured, uraniferous samples. Organic matter investigated by OTA gives two exothermic peaks on DTA curves. The dominant peak
appearing at temperature higher than 500C, confirm the high maturity of the organic matter. Results of analysis by Py-GC-MS
complement the OTA results. The organic matter in all of the samples shows the same general pyrolysis characteristics. The
pyrograms are dominated by low molecular mass aromatic hydrocarbons. The samples differ in relative abundances of the compounds.
The changes in temperature and intensity of the lower-temperature peak in OTA method and differences in relative abundances
of aromatic hydrocarbons were used to investigate differences in thermal maturity of the organic matter.