Rock magnetism in the alpine-peridotite body at Dun Mountain, New Zealand

摘要

The directions of chemical remanent magnetisation acquired during serpentinisation of the classic alpine-type peridotite-serpentinite body at Dun Mountain, New Zealand, are chaotic, and show little sign of stabilisation or convergence during step-wise alternating field demagnetisation. During demagnetisation, most samples show progressive changes in direction which are interpreted as being caused by selective demagnetisation of at least two primary components of remanent magnetisation that have different directions. The primary components are thought to have formed during separate periods of serpentinisation, between which times either the geomagnetic field changed in direction or the ultramafic body, as a whole, was rotated.