¹M. V. Goryunov,²G. Varga,²Z. Dankházi,¹A. V. Chukin,³I. Felner,⁴E. Kuzmann,⁴Z. Homonnay,¹R. F. Muftakhetdinova,¹V. I. Grokhovsky,¹M. I. Oshtrakh
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14363]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russian Federation
²Department of Materials Physics, Eötvös Loránd University, Budapest, Hungary
³Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
⁴Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
Published by arrangement with John Wiley & Sons

A fragment of the Kayakent IIIAB iron meteorite was analyzed using optical microscopy, scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD), X-ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. Optical microscopy and SEM show the presence of (i) the pure α2-Fe(Ni, Co) grains, (ii) the γ-Fe(Ni, Co) phase grains, (iii) the γ-Fe(Ni, Co) rims around the α2-Fe(Ni, Co) phase areas, (iv) the cloudy zone (a mixture of the γ-FeNi(Co) and α2-Fe(Ni, Co) phases), (v) plessite structures, and (vi) schreibersite inclusions in the α-Fe(Ni, Co) phase. The α-Fe(Ni, Co) phase demonstrates the ε-structure αε-Fe(Ni, Co) with the presence of at least three different orientations of the αε-Fe(Ni, Co) microcrystals, as shown by EBSD. EDS indicates variations in the Ni concentrations in the following ranges: (i) ~5.4–7.2 atom% in the α-Fe(Ni, Co) phase, (ii) ~15–18 atom% in the α2-Fe(Ni, Co) phase, and (iii) ~29–47 atom% in the γ-Fe(Ni, Co) phase grains. Schreibersite inclusions contain ~23.5–23.6 atom% of P, ~45.1–46.5 atom% of Fe, and ~28.8–31.4 atom% of Ni. The presence of ~98.1 wt% of the α-Fe(Ni, Co) phase and ~1.9 wt% of the γ-Fe(Ni, Co) phase is found by XRD in the powdered sample, while schreibersite is detected by XRD in the surface of the section only. Magnetization measurements show ferromagnetic multiphase material and a magnetic saturation moment of 175 emu g−1. The room temperature Mössbauer spectrum of the powdered Kayakent IIIAB sample demonstrates six magnetic sextets related to the ferromagnetic α2-Fe(Ni, Co), α-Fe(Ni, Co), and γ-Fe(Ni, Co) phases and one singlet assigned to the paramagnetic γ-Fe(Ni, Co) phase. In addition, the Mössbauer spectrum shows six minor magnetic sextets associated with 57Fe in the M1, M2, and M3 sites in schreibersite and one minor doublet shape assigned to the superparamagnetic rhabdite microcrystals. The iron fractions in the detected phases can be roughly estimated as follows: (i) ~11.9% in the α2-Fe(Ni, Co) phase, (ii) ~75.6% in the α-Fe(Ni, Co) phase, (iii) ~5.7% in the disordered γ-Fe(Ni, Co) phase with Ni content of ~34–40 atom%, (iv) ~1.5% in the more ordered γ-Fe(Ni, Co) phase with a higher Ni content (~46–47 atom%), (v) ~0.5% in the paramagnetic γ-Fe(Ni, Co) phase (~29–33 atom% of Ni), (vi) ~3% in schreibersite, and (vii) ~2% in rhabdite.

^1,2Zhi Li,^1,3Ying-Kui Xu,^4,5Shui-Jiong Wang,⁴Si-Zhang Sheng,^1,3Shi-Jie Li,^1,3Xiong-Yao Li,^1,3Jian-Zhong Liu,⁶Dan Zhu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14369]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
³CAS Center for Excellence in Comparative Planetology, Hefei, China
⁴State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Beijing), Beijing, China
⁵Frontiers Science Center for Deep-Time Digital Earth, China University of Geosciences (Beijing), Beijing, China
⁶State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Published by arrangement with John Wiley & Sons

High-energy impact events prevalent during planetary accretion in the solar system’s evolution significantly shaped planetary bodies, though the effects of shock metamorphism on nickel (Ni) isotope fractionation remain unclear. To investigate the effect of the shock process on Ni isotopes, we selected three shocked ordinary chondrites (OCs) and obtained three sample pairs, each consisting of a melted region and its corresponding unmelted region. We also prepared two whole rock samples and four pairs of magnetic and coupled nonmagnetic samples. The shock melt pockets (SMPs) from three shocked OCs (Chelyabinsk LL5, Viñales L6, Tassédet 004 H5) show δ⁶⁰Ni values of 0.15 ± 0.05‰, 0.14 ± 0.02‰, and 0.20 ± 0.04‰, while adjacent unmelted parts show δ⁶⁰Ni values of 0.21 ± 0.03‰, 0.19 ± 0.01‰, and 0.19 ± 0.03‰. These data are slightly higher than the BSE value (0.11 ± 0.01‰) but generally overlap with the Ni isotopic variation of OCs (0.15–0.51‰) reported in previous studies. The SMPs do not show discernible isotopic variations relative to coupled unmelted parts, suggesting that shock-induced evaporation could not cause Ni isotope fractionation. The value of bulk OCs is calculated by compiling data from previous and this study, yielding a value of ‰0.21−0.11+0.28‰. Moreover, no consistent Ni isotopic variations from four pairs of magnetic and nonmagnetic counterparts are observed. Several possible processes resulting in Ni isotopic variations are discussed. A slight negative correlation between S content and Ni isotopic composition, along with a positive correlation between Ni elemental and isotopic composition in shocked OCs, suggests that the Ni isotopic characteristics may be predominantly influenced by the relative proportions of metal and sulfide phases.