The quantification of crystallographic preferred orientation using magnetic anisotropy

Abstract

Magnetic anisotropy analysis presents an alternative and fast method for obtaining and quantifying crystallographic preferred orientations in rocks, using relatively simple equipment. Two natural examples and numerical modeling demonstrate that magnetic anisotropy increases with increasing degree of crystallographic preferred orientation. The normalized magnetic parameters Mi = ln(ki/(kmax * kint * kmin)1/3) (kmax >= kint >= kmin are the principal magnetic susceptibilities) correlate directly with March `strains' obtained from X-ray texture goniometry. The additional advantage of our method is that the preferred fabrics are determined from large sample volumes (typically about 11 cm3) rather than the essentially two-dimensional slice used in optical and X-ray methods. Thus, magnetic anisotropy provides a reliable measure of bulk crystallographic preferred orientation in rocks.