REFLECTANCE AND PETROLOGY OF A BURNING BITUMINOUS COAL SEAM

Samples from a burning bituminous coal seam from Coalspur, Alberta, were studied by reflected light microscopy. Two zones - namely oxidation-combustion and distillation - were detected in the seam. Near the surface, the oxidation zone contained chars showing cracks and oxidation rims. The cracks were filled with fluorescing hydrocarbon material formed by thermal cracking of coal macerals. The chars in the deeper part of the oxidation zone had a carbonized matrix and burnt rims. The distillation zone covered most of the coal seam. Chars were mostly in the precarbonization stages, except those immediately below the combustion zone or near the base of the seam. The distilled chars were formed by heat generated by combustion at the top of the seam and also by heat transfer from an underlying burning seam through an intermediate clastic layer. The minimum temperature of formation of residues in the oxidation and distillation zones was estimated.