Characterisation of non-extractable macromolecular organic matter in Palaeozoic coals

Comprehensive organic-geochemical investigations were applied to Permian, Carboniferous and Devonian coals. The major goal of the investigation was to quantify differences in organic matter composition of the coals on a molecular level and to associate these differences with either i) primary composition of the precursor plant material, or ii) diagenetic processes related to burial and temperature increase or iii) evolutionary time trends. The pre-extracted samples were analysed by means of pyrolytic and chemical degradation techniques as well as FTIR spectroscopy. Additionally, Rock-Eval pyrolysis and organic petrography were used to obtain information on the bulk of the coal samples. The degradation analysis revealed a wide variety of individual compounds including n-alkanes, isoprenoids, polycylic aromatic compounds, fatty acids, alkylbenzenes, aromatic carboxylic acids and phenols. Relative concentrations of substances or compound groups were correlated with bulk parameters and age of the samples. Significant correlations of the chemical data were found out mainly for maturity parameters and maceral composition. Time depending changes in chemical composition were observed only to a minor extent. Thus, the rapid morphologic evolution of higher land plants in the Late Palaeozoic is not reflected in a significant way by the chemical composition of the non-extractable matter in the coal samples investigated. (c) 2006 Elsevier B.V. All rights reserved.