Resinite: its infrared spectrum and coalification pattern

Abstract

On the basis of infrared spectral studies some years ago, it was suggested that the maceral resinite was comprised of two contrasting chemical-structural groups: one confined to peats, brown coals, lignites and sub-bituminous coals, the other to the low- and mediumrank bituminous coals. There was little evidence of the existence of resinites with transitional spectra. The maceral frequently occurred in bituminous coals as veins or interconnected globules probably formed by migration at sub-bituminous levels of coalification. Further support came from their differing responses when carbonized: the highly aliphatic resinites from low-rank deposits distilled with little polymerization or increase in aromaticity, but those from bituminous coals appeared to eliminate non-aromatic CH with development of increasing aromaticity. Recent petrological studies in independent laboratories confirm the contrast between the groups, and the migration, but also suggest that much resinite in bituminous coals is of secondary origin and is due to expulsion from several macerals during the sub-bituminous rank stage, the coalification level corresponding to the period of maximum petroleum generation from crustal organic matter.