Quantitative correlation of texture and magnetic anisotropy of compacted calcite-muscovite aggregates

摘要

Deformation of carbonate rocks leads to crystallographic preferred orientations (CPOs) of calcite, which in turn generates an anisotropy of magnetic susceptibility (AMS). The use of the diamagnetic anisotropy, which arises from the preferential orientation of calcite, for texture characterization is usually hindered by (1) the weakness of the anisotropy, and (2) overlapping contributions from paramagnetic and ferromagnetic minerals to the AMS. In this study, the diamagnetic, paramagnetic and ferromagnetic sub-fabrics of synthetic calcite-muscovite samples have been separated using high-field torque measurements. The CPO of calcite and muscovite has been determined by neutron diffraction, and the magnetic sub-fabrics are compared to the AMS that was re-calculated from the CPO. The isolated diamagnetic sub fabric shows a good correlation with the calcite texture for calcite concentrations above 70%. The paramagnetic sub-fabric is shown to be a reliable texture parameter for muscovite, even at a concentration of 5%. The results demonstrate the capability of the AMS method as a texture parameter in impure carbonate rocks.