This paper presents the results of oxyreactive thermal analyses of organic matter in rocks, heated naturally during diagenetic
to metamorphic processes. During the experiments we traced the reactions in the temperature range up to 900C, it means from
the very beginning of diagenetic transformations to the highest real temperatures acting in the Earth's crust as a solid phase.
The results showed that TA could be a tool for the reconstruction of thermal regime in natural coal-bearing systems.