Comprehensive Investigation of Some Ordinary Chondrites Based on X-Ray Methods and Mössbauer Spectroscopy

Resumo

Comprehensive investigation into ordinary chondrites presented by the species of Markovka (H4 petrological type), Polujamki (H4 type) and Jiddat Al Harasis 055 (L4-5 type) is performed. The element and phase compositions, as well as the oxidation states of iron and nickel in the chondrites, are examined via micro X-ray fluorescence (micro-XRF), Mössbauer spectroscopy and synchrotron-based X-ray absorption spectroscopy. Elemental composition analysis is performed using micro-XRF, allowing one to obtain element distribution maps for the meteorite samples. According to Mössbauer spectroscopy data gathered on iron-containing phases, the chondrites consist mainly of olivine and goethite with a small amount of pyroxene and hematite. A low amount of troilite and kamacite is also observed in the Markovka and Polujamki specimens. The oxidation states of 3d metals in the chondrites are estimated from Fe and Ni K-edge X-ray absorption near-edge structure (XANES) spectra. Most nickel atoms in the meteorites are found to be in the Ni²⁺ state, while iron has an average oxidation state of +2.4 which is commensurate with the Mössbauer spectroscopy data. Infrared spectroscopy analysis of the chondrites is implemented as well. The results are important from the viewpoint of statistics acquisition on ordinary chondrites, as well as for further understanding of their formation.