Rock magnetic properties of the Arunta Block, central Australia, and their implication for the interpretation of long-wavelength magnetic anomalies

Rock magnetic and petrologic studies of a suite of deep crustal rocks from the Arunta Block of Central Australia reveal that the granulite grade rocks are in general much more magnetic than the amphibolite grade samples irrespective of bulk rock composition. The dominant magnetic mineral in all samples is relatively pure magnetite. The sample have very large remanences. These remanences are relatively resistant to thermal demagnetization. Thus remanence may contribute significantly to the observed magnetic anomalies. The magnetic susceptibilities of the samples are only capable of producing a magnetization of less than 1 A/m in the 0.05 mT present-day field of Central Australia. Susceptibility is nearly constant with temperature to within 30°C of the Curie temperature where it decreases rapdily, i.e., there is no significant Hopkinson peak. -from Authors