Chemical and petrological properties of some liptinite-rich coals from British Columbia

Abstract

Chemical and petrological analyses were carried out on several British Columbia coals which are known as ‘needle’ coals because of the pine needle morphology exhibited on weathering. The object was to determine the nature of the precursor and thus to identify the component maceral as resinitic or algal. Infrared spectroscopy, saturate fraction gas chromatography, pyrolysis chromatography, gas chromatography-mass spectrometry, organic elemental analysis and reflectance and fluorescence microscopy were used. While the i.r. properties are consistent with previously published results on resinite, the other chemical results suggest that the present materials are not obviously related to any given member of the liptinite group of macerals. High concentrations of extractable hopanoid hydrocarbons are interpreted as resulting from high contribution to the biomass by bacterial debris. The petrological results suggest that the main constituent of the ‘needles’ can be best described as bituminite II or III derived from non-algal lipids. This conclusion is also supported by the observed associations of the other identifiable macerals. The results indicate that the ‘needles’ have been chemically and petrologically homogenized from a liptinite-rich precursor with minimal algal input. The present morphology may have been preserved from resin rodlets which have been severely altered by catagenetic or biological mechanisms or both.