ANISOTROPY OF MAGNETIC-SUSCEPTIBILITY OF MAGNETICALLY ORIENTED ROCK POWDERS

To estimate the maximum magnetic anisotropy of the ensemble of magneti c carriers present in a rock, we measured the Anisotropy of Magnetic l ow field Susceptibility (AMS) of magnetically oriented rock powder. We studied basaltic rock (Chaine des Puys, Massif Central France) and me tasediments (Coffs Harbour, Australia). In the basaltic powder, PSD ti tanomagnetites show maximum anisotropy of L approximate to 1.16. In th e metasediments, the foliation anisotropy is constant (F approximate t o 1.3) controlled by iron-bearing phyllosilicates. The linear anisotro py goes up to L approximate to 2 in pyrrhotite bearing rocks. In contr ast, magnetite bearing samples show low linear anisotropy (L<1.1).