Magnetic classification of stony meteorites: 3. Achondrites

Abstract

A database of magnetic susceptibility measurements of stony achondrites (acapulcoitelodranite clan, winonaites, ureilites, angrites, aubrites, brachinites, howardite-eucrite-diogenite (HED) clan, and Martian meteorites, except lunar meteorites) is presented and compared to our previous work on chondrites. This database provides an exhaustive study of the amount of iron-nickel magnetic phases (essentially metal and more rarely pyrrhotite and titanomagnetite) in these meteorites. Except for ureilites, achondrites appear much more heterogeneous than chondrites in metal content, both at the meteorite scale and at the parent body scale. We propose a model to explain the lack of or inefficient metal segregation in a low gravity context. The relationship between grain density and magnetic susceptibility is discussed. Saturation remanence appears quite weak in most metal-bearing achondrites (HED and aubrites) compared to Martian meteorites. Ureilites are a notable exception and can carry a strong remanence, similar to most chondrites.