Quantitative relationship between opAMS and ipAMS in some pyrrhotite-bearing rocks

The anisotropy of magnetic susceptibility (AMS) of pyrrhotite-bearing rocks (typically represented by ultramafic rocks) is often composite, carried not only by pyrrhotite, but also by magnetite and mafic silicates. In magnetic fabric studies, it is therefore desirable to separate the AMS component due to pyrrhotite from that due to the rest of the rock. This can be made, in addition to other techniques, by the anisotropy of the out-of-phase component of the AMS (opAMS). For comparative studies, it is vital to know quantitative relationship between opAMS and ipAMS, which is the aim of this paper. This knowledge is useful in interpreting the AMS of rocks in which pyrrhotite is important but not dominant magnetism carrier.The out-of-phase susceptibility (opMS) of the pyrrhotite-bearing rocks investigated increases significantly with the field intensity within the field range between 10 A/m and 700 A/m. The increase is faster in very low fields (