Earth Planets Space, Vol. 59 (No. 7), pp. 717-725, 2007
Andrew J. Biggin1,2 and Mireille Perrin1
1Laboratoire Tectonophysique, ISTEEM, Université Montpellier II, CC049, Montpellier, 34090, France
2Palaeomagnetic Laboratory Fort Hoofddijk, Universiteit Utrecht, Utrecht 3584 CD, Netherlands
(Received September 27, 2006; Revised February 15, 2007; Accepted March 3, 2007; Online published July 20, 2007)
We analyse the results of Thellier palaeointensity experiments modified so that the measured magnetisation at any stage may be decomposed into components of natural remanent magnetisation (NRM) and laboratory thermal remanent magnetisation (TRM). We demonstrate that the very long high temperature tails of pTRM acquired by multidomain (MD) grains may be detected in Thellier experiments without recourse to explicit pTRM tail check measurements. This can save time in the experimental process and provides a more sensitive indication of how MD behaviour may affect that particular experiment than either pTRM tail checks or the observation of zigzagging in an IZZI experiment. We observe that the action of imparting a pTRM tail also involves some removal of NRM. However, the pTRM tails are not the analogues of classical overprints as may be intuitively expected but instead appear to favour remagnetisation over demagnetisation. This and other observed behaviour is not consistent with any phenomenological model of MD TRM but is consistent with predictions made by kinematic theory.
Key words: Paleointensity, thermoremanent magnetisation, pTRM tails, multidomain grains.