Open AccessTransformations of magnetic mineralogy in rocks revealed by difference of hysteresis loops measured after stepwise heating: theory and case studies
Author(s) -
Henry Bernard,
Jordanova Diana,
Jordanova Neli,
Le Goff Maxime
Publication year - 2005
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2005.02644.x
Subject(s) - ferrimagnetism , thermomagnetic convection , remanence , rock magnetism , magnetic hysteresis , hysteresis , grain size , magnetic mineralogy , mineralogy , paramagnetism , geology , phase (matter) , materials science , condensed matter physics , magnetization , chemistry , magnetic field , physics , quantum mechanics , organic chemistry , geomorphology
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 the loops measured after thermal treatment at two different consecutive temperatures. Depending on the nature of the mineralogical alterations (the formation of a new ferrimagnetic phase from a paramagnetic one, the thermal transformation of the originally present ferrimagnetic phases, grain size variation) and on their relative intensities, it is possible to distinguish between different cases. The examples shown reveal the significant alteration of magnetic carriers at low temperatures (up to 200°C) which usually is not identified by thermomagnetic analysis of magnetic susceptibility. The low temperature alteration of the remanence carriers has important consequences for the reliability and suitability criteria of palaeointensity determinations.