Changes in the elemental composition of asphaltenes in organic matter (OM) of different origin, with particular focus on their evolution from proto- to mesocatagenesis, were analyzed in samples of Devonian bituminous shales and brown coals from the Kuznetsk Basin and samples of Cenozoic brown coals and clays from the Middle Amur Basin. The composition of asphaltenes (protoasphaltenes) of different origin is shown to be differentiated as early as the stage of sedimentation: terrestrial asphaltenes are enriched in carbon and hydrogen, while sapropelic asphaltenes contain more oxygen (heteroelements). It is discovered that the formation of the two evolutionary catagenetic branches of asphaltene compositions corresponds to the onset of protocatagenesis. Both sapropelic and terrestrial OM undergo different transformations during diagenesis (at the sedimentprotocatagenesis interface), with sapropelic OM subjected mainly to drastic carbonation with parallel hydrogenation, while redistribution of oxygen and hydrogen concentrations associated with a dramatic loss of the latter observed in the terrestrial OM (if the of carbon concentration level is constant). Further changes in the composition of asphaltenes within these branches take place during the mesocatagenesis through apocatagenesis, during which the evolutionary branches converge again.
