Cretaceous coal-bearing sequences from the Moose River basin in northern Ontario and the Peace River basin in northeast British Columbia were analysed for trace- and major-element contents. Modes of occurrence of the trace elements are proposed on the basis of Pearson correlation coefficients and scanning electron microscopy coupled with energy-dispersive X-ray analysis.The Moose River basin lignite was deposited in an alluvial floodplain environment, and the restricted mineralogy, dominated by quartz and kaolinite, reflects derivation from a highly weathered terrain. The bituminous coal from the Peace River basin was deposited in an alluvial to deltaic environment, with a dominant mineralogy including quartz, illite, kaolinite, mixed-layer clays, carbonates, barite, feldspar, and pyrite.Trace-element contents in both deposits are comparable to the average concentration in United States coals. Modes of occurrence of trace elements in the coals are extremely variable and depend on local conditions both during deposition and subsequently. Association with the organic matter is the most common mode of occurrence of trace elements in the Moose River basin lignites, whereas clay minerals are important trace-element sites in the Peace River basin coal.Factors including coal rank, clay mineralogy, nature of the surrounding rocks, and composition of the groundwaters appear to have important influences on the concentrations of the trace elements and their siting in the coals.

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