Weathering of Antarctic meteorites investigated from contents of Fe³⁺, chlorine, and iodine

The chemical states of iron in fourteen Antarctic H chondrites were studied by means of Mössbauer spectroscopy. Fe³⁺, Fe³⁺, troilite, and Fe-Ni alloy were analyzed in all meteorites. Determinations of Cl and I in 28 Antarctic H, L, and LL chondrites were carried out by radiochemical neutron activation analysis, and those in three Antarctic eucrites were carried out by isotope dilution mass spectrometry. The results ranged from 90 to 1700 ppm for Cl and from 0.07 to 5 ppm for I in ordinary chondrites, and from 30 to 330 ppm for Cl and from 1 to 9 ppm for I in eucrites. On the basis of the data on halogens and the Mössbauer spectroscopy, terrestrial weathering of Antarctic meteorites are discussed. The relative amount of Fe³⁺ in H chondrites correlates positively with chlorine and iodine contents, and Fe²⁺ and troilite correlate negatively. Chlorine shows a higher enrichment in ordinary chondrites than in eucrites whereas the I enrichment seems to be larger in Fe-Ni alloy-poor meteorites.