Anisotropy of magnetic susceptibility from highly sheared marbles in the Helvetic Alps

ABSTRACT Anisotropy of magnetic susceptibility (AMS) measured in the presence of low and high fields, at ambient and low emperatures(17K), has been used to separate ferromagnetic(s. l.), paramagnetic and diamagnetic sub-fabrics from a highly deformed, low-grade metamorphosed marble shear zone in southwest Switzerland. The AMS and bulk susceptibility obtained from these marbles reflect developmentof crystallographicpreferred orientations, as well as the ratio of diamagneticmatrix calcite to paramagnetic secondary phases. The magnetic fabrics in two of the three study locations is produced by iron-rich calcite, and display an inverse relationship to structural cleavage. Preferred orientations of calcite c-axes correspond to the directions of the separated diamagnetickmax•