APPLICATION OF EXTERNAL MAGNETIC-FIELD TO CHARACTERIZE MAGNETIC OXIDES IN THE CARBONACEOUS CHONDRITE ORGUEIL

Magnetite is the most common magnetic phase in carbonaceous chondrites . Comprehensive and detailed investigations of this magnetite with X-r ay diffraction and electron microprobe have revealed minute amounts of substitutional impurities (e.g. Ni) in the magnetite, but no other ma gnetic oxides have been found in these meteorites. Using an external m agnetic field and Mossbauer spectroscopy, we have found a component in the Mossbauer spectrum that we attribute to maghemite. The relative a rea of this component implies that maghemite accounts for approximatel y 12% of the magnetic oxides in Orgueil.