Comparison of the 57 Fe hyperfine interactions in silicate phases in Sariçiçek howardite and some ordinary chondrites

Silicate crystals have different thermal history in non-differentiated and differentiated meteorites. This leads to some differences in the Fe 2+ and Mg 2+ distribution between the M1 and M2 sites in olivine, orthopyroxene and clinopyroxene crystals in stony meteorites resulting in small variations in the Fe local microenvironment. For this reason, a comparison of Mössbauer hyperfine parameters for the 57 Fe in the M1 and M2 sites in orthopyroxene and Ca-rich clinopyroxene for non-differentiated NWA 6286 LL6, NWA 7857 LL6 and Tsarev L5 ordinary chondrites and differentiated Sariçiçek howardite was carried out. The results obtained demonstrated small variations in quadrupole splitting and isomer shift for the studied non-differentiated and differentiated stony meteorites. © 2019, Springer Nature Switzerland AG.? 02. Türkiye Bilimsel ve Teknolojik Araştirma Kurumu: MFAG/113F035 Ministry of Education and Science of the Russian Federation: 3.1959.2017/4.6Acknowledgements The authors wish to thank G.A. Yakovlev and Dr. M.S. Karabanalov for the help with scanning electron microscopy with energy dispersive spectroscopy. This work was supported by the Ministry of Science and Higher Education of the Russian Federation (the Project ? 3.1959.2017/4.6) and Act 211 Government of the Russian Federation, contract ? 02.A03.21.0006. O.U. acknowledges the Scientific and Technological Research Council of Turkey (the Project number: MFAG/113F035). -

The interior and the fusion crust in Sariçiçek howardite: Study using X-ray diffraction, magnetization measurements and Mössbauer spectroscopy

PubMed: 318064802-s2.0-85076566142The meteorite Sariçiçek, a 2015 howardite fall in Turkey, was analyzed using various physical techniques. Both the interior and the fusion crust were studied by optical and scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, magnetization measurements and Mössbauer spectroscopy. The main and minor iron-bearing phases such as orthopyroxene, Ca-poor and Ca-rich clinopyroxene, chromite with hercynite, Fe2+ and Fe3+ ilmenite, troilite, ?-Fe(Ni, Co), ?2-Fe(Ni, Co) and ?-Fe(Ni, Co) phases were identified. The ratios of Fe2+ occupancies in the M1 and M2 sites in the silicate phases as well as the equilibrium Fe2+ and Mg2+ cations distribution temperatures (Teq) for orthopyroxene were estimated using X-ray diffraction and Mössbauer spectroscopy, which appeared to be in a good agreement: for example, Teq were 886 and 878 K, respectively. The glass-like fusion crust of Sariçiçek consists of orthopyroxene with ferrous and ferric compounds that are likely products of combustion and melting. © 2019 Elsevier B.V.Ministry of Education and Science of the Russian Federation, Minobrnauka Government Council on Grants, Russian Federation: ? 02. Ural Federal University, UrFU Ministry of Science and Higher Education of the Russian Federation: 3.1959.2017/4.6The authors wish to thank Dr. E.I. Denisov (Institute of Physics and Technology, Ural Federal University) for his kind help with chemical analysis using X-ray fluorescence spectroscopy. This work was supported by the Ministry of Science and Higher Education of the Russian Federation (the Project ? 3.1959.2017/4.6 ) and Act 211 of the Government of the Russian Federation , contract ? 02.A03.21.0006 .The authors wish to thank Dr. E.I. Denisov (Institute of Physics and Technology, Ural Federal University) for his kind help with chemical analysis using X-ray fluorescence spectroscopy. This work was supported by the Ministry of Science and Higher Education of the Russian Federation (the Project ? 3.1959.2017/4.6) and Act 211 of the Government of the Russian Federation, contract ? 02.A03.21.0006

Bjurböle L/LL4 ordinary chondrite properties studied by Raman spectroscopy, X-ray diffraction, magnetization measurements and Mössbauer spectroscopy

Bjurböle L/LL4 ordinary chondrite was studied using scanning electron microscopy with energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, magnetization measurements and Mössbauer spectroscopy. The phase composition and the relative iron fractions in the iron-bearing phases were determined. The unit cell parameters for olivine, orthopyroxene and clinopyroxene are similar to those observed in the other ordinary chondrites. The higher contents of forsterite and enstatite were detected by Raman spectroscopy. Magnetization measurements showed that the temperature of the ferrimagnetic-paramagnetic phase transition in chromite is around 57 K and the saturation magnetic moment is ~7 emu/g. The values of the 57Fe hyperfine parameters for all components in the Bjurböle Mössbauer spectrum were determined and related to the corresponding iron-bearing phases. The relative iron fractions in Bjurböle and the 57Fe hyperfine parameters of olivine, orthopyroxene and troilite were compared with the data obtained for the selected L and LL ordinary chondrites. The Fe2+ occupancies of the M1 and M2 sites in silicate crystals were determined using both X-ray diffraction and Mössbauer spectroscopy. Then, the temperatures of equilibrium cation distribution were determined, using two independent techniques, for olivine as 666 K and 850 K, respectively, and for orthopyroxene as 958 K and 1136 K, respectively. Implications of X-ray diffraction, magnetization measurements and Mössbauer spectroscopy data for the classification of the studied Bjurböle material indicate its composition being close to the LL group of ordinary chondrites