Thermal Enhancement of Magnetic Fabrics in High Grade Gneisses

Graham J. Borradaile (1) , France Lagroix (2)

1 Department of Geology [Thunder Bay]
2 IPGP - Institut de Physique du Globe de Paris

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 subfabric. 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.

Domains: Sciences of the Universe [physics]

Graham J. Borradaile, France Lagroix. Thermal Enhancement of Magnetic Fabrics in High Grade Gneisses. Geophysical Research Letters, 2000, 27, pp.2413-2416. ⟨10.1029/2000GL008522⟩. ⟨insu-01311022⟩