Anisotropy of diamagnetic susceptibility in Thassos marble: A comparison between measured and modeled data

A study of shear zones within the calcite marble complex of the island of T hassos (Greece) shows that the low field anisotropy of magnetic susceptibil ity (AMS)-technique can be successfully applied to diamagnetic rocks for ch aracterizing rock fabrics. The strain path involves both an early pure shea r stage and a simple shear overprint that is documented by a transition fro m triaxial (neutral) to uniaxial (prolate) shapes of AMS ellipsoids. The ma ximum susceptibility is oriented perpendicular to the rock foliation, refle cting the preferred orientation of calcite c-axes in the protolith as well as in the mylonites. For three samples that represent different types of ca lcite fabrics, the AMS was recalculated from neutron and electron backscatt er diffraction textural data. A comparison of the measured and modeled data shows a good coincidence for the orientation of the principal AMS axes and for the recalculated anisotropy data. Both measured and modeled data sets reflect the change from neutral to distinct prolate ellipsoids during progr essive deformation. (C) 2000 Elsevier Science Ltd. All rights reserved.