A study of ordinary chondrites by Mssbauer spectroscopy with high-velocity resolution

Abstract

An improvement in the velocity resolution and quality of Mssbauer spectra has been applied to a group of ordinary chondrites. This improvement permitted us to carry out a more detailed study of the iron bearing phases in these samples than has previously been possible. Mssbauer spectra of 11 ordinary chondrites of L and H chemical groups were measured using 4096 channels and presented for further analysis in 1024 channels. Subspectra of the metal grains of several chondrites demonstrated the presence of at least two magnetic sextets related to the main Fe(Ni, Co) phases. Moreover, Mssbauer study of extracted metal grains from Tsarev L5 revealed three sextets and one singlet spectral components related to various α-Fe(Ni, Co), α′-Fe(Ni, Co), α2-Fe(Ni, Co), and γ-Fe(Ni, Co) phases. Each subspectrum of olivine and pyroxene in Mssbauer spectra of ordinary chondrites was fitted by superposition of two quadrupole doublets related to M1 and M2 sites in minerals for the first time. An analysis of relative areas and Mssbauer hyperfine parameters was performed and some differences for L and H chondrites as well as for M1 and M2 sites were observed. Mssbauer parameters of troilite and oxidized iron were analyzed. In contrast to a previous study with 512-channel spectra, the presence of oxidized iron was found in all chondrites.