TRACE-ELEMENT GEOCHEMISTRY OF THE WHITEWOOD MINE COALS IN ALBERTA

Subbituminous coals, taken from a freshly mined open pit as well as fr om nine drillholes in the Whitewood Mine, Alberta, were analyzed for t heir elemental and radionuclide concentration. Furthermore, the coal a sh was analyzed for major oxides, and a comparison was made with coals of similar rank and present only 12 km away, in the Highvale Mine. Th e Whitewood Mine coals are ''clean'' by world standards and do nor con tain any environmentally deleterious elements in excess amounts. They are suitable for utilization, but care should be taken to minimize the negative opacity effects on the electrostatic precipitators (ESPs). T he low Na2O content in the coals, particularly in the open-pit samples , may affect ash resistivity. This could result in a decrease in the f low of current and thus a decrease in the precipitator efficiency. Cer tain trends of major oxides in the coal ash are observed in a north-so uth direction and are discussed, with particular emphasis on the Na2O distribution in the six coal seams. The Whitewood Mine drillhole sampl es contain the following mean concentration of elements: As (4.7 ppm), Br (15.1 ppm), Cl (21.5 ppm), Co (3.3 ppm), Cr (7 ppm), Mo (4.8 ppm), Na (710 ppm), Ca (1.5%), Mn (110 ppm), Th (6 ppm), U (2.5 ppm), V (19 .3 ppm), and Sb (0.7 ppm). In the surface samples, the mean concentrat ions of the above elements are as follows: As (4.5 ppm), Br (196.2 ppm ), Cl (38.4 ppm), Co (5.4 ppm), Cr (200 ppm), Mo (16.7 ppm), Na (263 p pm) Ca (1.4%), Mn (120 ppm), Th (5.2 ppm), U (1.6 ppm), V (14.3 ppm) a nd Sb (0.7 ppm). The open-pit surface samples are much enriched in Br, Mo, and Cr, slightly enriched in Cl and Co, much depleted in Na, and slightly depleted in Th, U, and V compared to the drillhole samples. B oth sets have similar concentrations of As and Mn. There is a slight i ncrease in As concentration in the north and south ends of the pit; a slight increase in a northern direction was also noted for Si, U, and Na. All rare earth elements (REEs) are within the world range for most coals. Compared to the Highvale Mine coals, the Whitewood Mine coals are slightly enriched in As and V; depleted in Br; Cl, Cr, Se, and Sb; and have essentially the same concentration of Co, Mn, U, and radioac tive nuclides. The radioactive nuclides of the U and Th series present in the surface coals are low and comparable with those in coals from Australia, the United States, and the United Kingdom Semiquatitative m ineralogical analysis of the whole coal indicates the predominantly of quartz and its polymorph cristobalite, followed by kaolinite, mixed-l ayered clays and illite, with minor diopside, zeolite, rhodochrosite, and pyrite. The coal ash of the Whitewood Mine coals has low to medium slagging and fouling propensity.