The Effective Magnetisation of the Jurassic Dolerites of Tasmania

Abstract

Review of the magnetic properties and field responses of a Tasmanian dolerite sheet suggests that the magnetic field is controlled by variations in remanent magnetisation. There is general correlation between magnetic susceptibility and crystal size and texture through the intrusion, but no correlation between susceptibility and nature of the magnetic field. As the natural remanence and modern field vectors are crudely aligned, the effective contrast of the intrusion is the vector sum, which is equivalent to a susceptibility of about 0.07 SI. Intruded rocks are non-magnetic. Variations within the intrusion are explained in terms of oxide-rich horizons (which have equivalent susceptibilities up to 0.15 SI) and reversely magnetised sections.