Transformations of magnetic mineralogy in rocks revealed by difference of hysteresis loops measured after stepwise heating: theory and case studies

摘要: SUMMARY A new approach for tracking mineralogical alterations during laboratory stepwise heating experiments is proposed. It uses the hysteresis loop obtained as a difference between loops measured after thermal treatment at two different consecutive temperatures. Depending on nature of (the formation ferrimagnetic phase from paramagnetic one, transformation originally present phases, grain size variation) and their relative intensities, it possible to distinguish cases. The examples shown reveal significant alteration magnetic carriers low temperatures (up 200°C) which usually not identified by thermomagnetic analysis susceptibility. temperature remanence has important consequences reliability suitability criteria palaeointensity determinations.