GEOCHEMISTRY OF SUBBITUMINOUS COALS FROM THE HIGHVALE MINE, ALBERTA, CANADA

Coals from the Highvale Mine, central Alberta Plains, were studied in order to determine the quantity (range and mean values), affinity, and mode of occurrence of the elements present in these subbituminous coa ls. Detailed elemental analyses were carried out for all coal seams an d interburden in two drillholes, HV901-84 and HV904-84. In total, 49 s amples were analyzed from the 16-m-deep HV904-84 drillhole (approximat ely three samples per meter of succession) and 33 samples from the 10. 8-m-deep HV901-84 drillhole (also three samples per meter of successio n). Mean concentration of various elements in the Highvale Mine coals are as follows, all others are below detection limits: Sb, 0.74 ppm; A s, 3.82 ppm; Br, 286.4 ppm; Cl, 72.3 ppm; Cr, 11.5 ppm; Co, 3.25 ppm; Cu, 20.6 ppm; F, 74.3 ppm; Hg, 0.012 ppb, Se, 1.65 ppm; U, 2.57 ppm; T h, 5.6 ppm; and V, 17.1 ppm. By world standards, all mean concentratio ns, except Br in some instances, are relatively low and the coals are not enriched in any environmentally or industrially hazardous elements . Therefore, the Highvale coals are considered ''clean'' by world stan dards and suitable for utilization. The concentration of elements asso ciated with minerals (clays and/or carbonates), such as K, Mg, Na, Th, U, V, and Zn, follows similar repetitive trends within coal seams thr oughout the coal-bearing succession, indicating that the pattern of co al formation is often cyclic and that these geochemical trends are rel ated to the ash content of the coal and the parting location within th e coal-bearing succession. Consistent seam-by-seam variations in the c oncentrations of elements generally do not occur, although some of the elements, such as Al, As, Sc, Th, and the rare earth elements, tend t o decrease from the roof toward the floor of coal seams. Only a few el ements show a higher concentration in the middle or lower parts of the seam, and it is believed that these trends may be more related to var iations in ash content of the samples than to stratigraphic controls. Almost all the elements whose concentrations consistently exceed the d etection limit appear to have strong inorganic associations. Exception s are Cl, Br, and B, which appear to be associated predominantly with the organic fraction in coal, and a few elements, such as Mn, which ap pear to have an intermediate affinity.