Experiments on TRM intensity dependence on cooling rate

Palaeointensity studies have an important role to play in understanding the origin and time variation of the geomagnetic field. However, theoretical considerations indicate that the intensity of magnetization recorded by a rock or archaeological sample will be dependent on the rate at which it cooled as well as field magnitude. Experiments on synthetic magnetite and titanomagnetites of varying grain sizes indicate that for acicular magnetite at low concentration, slower cooled TRM is stronger than faster cooled TRM, but for all other samples slower cooled TRM is weaker. This is the predicted behaviour. However the magnitude of the effect is much greater than the predicted kinetic effects and indicates that the magnetization of sub‐microscopic magnetite‐rich inclusions in the titanomagnetites strongly controls the TRM intensity of the matrix.