Understanding magnetic fabrics
Hirt, Ann M.; Schmidt, Volkmar; Almqvist, Bjarne S.G.
The anisotropy of magnetic susceptibility(AMS) has been used as an indicator of deformation, and in certain cases strain, in rocks for over fifty years. Advantages of using AMS to describe deformation is that low-field AMS is relatively fast to measure and it is very sensitive in detecting mineral alignment. However interpretation of AMS results is not always straightforwardand requires a good understanding of the mineral phase or phases, which contribute to the magnetic fabric. Numerous studies use the intensity of bulk susceptibilityto interpret whether diamagnetic, paramagnetic or ferromagneticminerals control the observed fabric. Such a criterion can be misleading since minerals responsible for the anisotropy are not always the minerals that make the largest contribution to the bulk susceptibility. Exampleswill be given from differentrock types to illustratethe role that mineralogy has on interpretingAMS results.