Low temperature magnetic transition of chromite in ordinary chondrites

J. Gattacceca (1) , P. Rochette (1) , F Lagroix (2) , P.E. Mathe (1) , B Zanda (3)

1 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
2 IPGP - Institut de Physique du Globe de Paris
3 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie

We present low temperature magnetic data (thermal demagnetization, hysteresis) obtained on thirty three ordinary chondrite meteorites. A magnetic transition is observed in the 40–80 K range (average 66 K), and is interpreted as a ferrimagnetic to paramagnetic phase transition. We present quantitative analyses of changes in magnetization across the magnetic phase transition and chemical elemental analyses to argue that chromite, a common accessory mineral in meteorites, is the mineral undergoing the phase transition, and not troilite or tetrataenite as proposed in previous studies. Moreover, we observe a correlation between the measured Curie temperature and chemical composition of chromites in ordinary chondrites. Low temperature magnetic measurement are thus a sensitive indicator of chromite composition in these meteorites, and as such a possible proxy to the understanding of their thermal metamorphism.

Domaines: Pétrographie

J. Gattacceca, P. Rochette, F Lagroix, P.E. Mathe, B Zanda. Low temperature magnetic transition of chromite in ordinary chondrites. Geophysical Research Letters, 2011, 38 (10), pp.L10203. ⟨10.1029/2011GL047173⟩. ⟨insu-01311073⟩