Conversion of the magnetic susceptibility tensor into the orientation tensor in some rocks

The preferred orientation of minerals in a rock with a structural or sedimentary fabric can be referred to by the orientation tensor. This paper describes the determination of the orientation tensor of the crystallographic c′-axes from the rock magnetic anisotropy and the mineral anisotropy degree, in rocks in which the magnetic anisotropy is dominantly carried by one mineral with uniaxial magnetic anisotropy (e.g. phyllosilicates, pyrrhotite, hematite). The orientation tensor of biotite c′-axes in four samples of the Bíteš orthogneiss determined in this way is similar to that determined independently through the universal stage measurement of biotite leaves in thin sections and is obtained much more rapidly by the magnetic method.