LITHOGEOCHEMICAL CHARACTERIZATION OF THE BEAVERBANK UNIT OF THE HALIFAX FORMATION, MEGUMA GROUP, AND ACID DRAINAGE IMPLICATIONS

Lithogeochemical analyses of samples from the Beaverbank unit at North Beaverbank were used to characterize the stratigraphic interval repre senting the gradation from metasandstone of the Goldenville Formation to slate of the overlying Halifax Formation in central mainland Nova S cotia (central Meguma area). The unit can be divided into three subuni ts on the basis of lithology, chemistry, and mineralogy Upper subunit A (the coticule horizon) consists principally of grey sulphide-rich me tasiltstone with abundant spessartine garnet and Mn-rich carbonate con cretions. Subunit B is similar to subunit A but has less garnet and mo re metasandstone interbeds. At the base, subunit C consists principall y of medium to coarse grained metasandstone with grey metasiltstone in terbeds, rare garnet, Mn-rich carbonate concretions which are less abu ndant than in subunits A and B, and only minor sulphides. Sulphur anal yses of samples from the Beaverbank unit indicate a potential acid gen erating hazard, based on Nova Scotia Department of the Environment gui delines which suggest that rocks containing greater than 0.40% sulphur should be treated as potentially acid generating. Rocks from the Beav erbank unit have sulphur contents as high as 3.4% and approximately 40 % of the rocks analyzed from this unit exceed 0.40% S limit. Subunits A and B have average sulphur contents of 0.70% and 0.60% respectively, whereas the sulphur content of subunit C is only 0.06%.