Origin of stable remanent magnetization in LL6 chondrite, St. Séverin

Thermal demagnetization has been carried out on 20 mutually oriented chips to unravel the stable paleomagnetic record of LL6 St. Séverin. Whereas the higher unblocking fractions (520–560 °C) of natural remanent magnetization (NRM) are directionally scattered, the lower unblocking fractions (<520 °C) are relatively well constrained along a great circle in a stereographic projection. Microscopic analysis revealed St. Séverin to contain paramagnetic troilite and a ferromagnetic Fe–Ni system. A sharp unblocking around 560 °C during thermal demagnetization strongly indicates that tetrataenite is the sole NRM carrier in St. Séverin. The absence of kamacite contribution on NRM and the presence of a scattered higher unblocking fraction (520–560 °C) of NRM imply a sequence of brecciation and a shock-induced metamorphism rather than a thermal origin of NRM.