MAGNETIC-SUSCEPTIBILITY MAPPING - APPLICATIONS FOR THE MEGUMA GROUP, CENTRAL NOVA-SCOTIA

An extensive magnetic susceptibility mapping program was undertaken in conjunction with re-processing and enhancement of aeromagnetic data o ver the Meguma Group of Nova Scotia. The ground follow-up consisted of several thousand in situ magnetic susceptibility measurements collect ed in conjunction with a detailed geological mapping program designed to identify the sources of newly resolved aeromagnetic anomalies. Anal ysis of the susceptibility data and magnetic mineralogy identified a s trong correlation between general magnetic character and stratigraphy. This correlation can be confidently demonstrated at the member level (e.g., Glen Brook unit), however, more detailed relationship, correspo nd to lithological variations within a particular unit. For example, s late packages within the Steves Road. unit have a mean susceptibility of 0.41(+/-0.09) x 10(-3) SI compared to 0.11(+/-0.09) x 10(-3) SI, fo r the predominant mete-sandstone strata. Other examples include variou s lithologies in the Goldenville Halifax Transition zone Upper Beds un it, which consists of silty slate (k(ave)=0.58 x 10(-3) SI), Mn-rich s ilt beds (k(ave)=1.02 x 10(-3) SI), and tightly folded sulphide rich s and beds (k(ave)=1.68 x 10(-3) SI). In situ susceptibility data is als o an indicator of sulphide content in the slates of the Halifax Format ion including pyrrhotite and to a lesser degree, pyrite. The susceptib ility readings also appeared to indicate anisotropy of magnetic suscep tibility (AMS) in the slates where pyrrhotite grains were oriented par allel to well developed cleavage. Within the Goldenville Formation, ma gnetic susceptibility measurements frequently provide the only indicat ion of lithological variations and hence facilitate the mapping of the monotonous metasandstone packages. Marker horizons can also be traced in a similar fashion.