Thermal Enhancement of Magnetic Fabrics in High Grade Gneisses

The orientation‐distributions of AMS and AARM ellipsoids are non‐coaxial in the Kapuskasing Zone granulites. AARM is due to the preferred orientation of magnetite which mostly postdates the silicate fabric. The AMS orientation‐distribution combines susceptibility anisotropies of magnetite and the silicates. Whereas heating does not increase the bulk susceptibility, it does improve the definition of the orientation‐distributions of both AMS and AARM. However, the orientation‐distribution of AARM is most enhanced and therefore post‐heated samples emphasize the magnetite sub fabric. Thus, heating does not clarify the interpretation of the silicate fabric in this study. However, it does change the samples' AMS fabric in such a way as to reveal the magnetite subfabric which can only otherwise be detected by more tedious AARM measurements.