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- Title
Characterization of iron meteorites by scanning electron microscopy, x‐ray diffraction, magnetization measurements, and Mössbauer spectroscopy: Mundrabilla IAB‐ung.
- Authors
Goryunov, M. V.; Varga, G.; Dankházi, Z.; Chukin, A. V.; Felner, I.; Kuzmann, E.; Grokhovsky, V. I.; Homonnay, Z.; Oshtrakh, M. I.
- Abstract
A fragment of Mundrabilla IAB‐ung iron meteorite was analyzed using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. The polished section of meteorite fragment characterization by optical microscopy and SEM shows the presence of the γ‐Fe(Ni, Co) phase lamellae, plessite structures and schreibersite inclusions in the α‐Fe(Ni, Co) phase. EDS indicates variations in the Ni concentrations in the following ranges: (i) ∼6.3–6.5 atom% in the α‐Fe(Ni, Co) phase and (ii) ∼22 to ∼45 atom% in the γ‐Fe(Ni, Co) phase lamellae including the range of ∼29–33 atom% of Ni leading to the paramagnetic state of the γ‐Fe(Ni, Co) phase. Schreibersite inclusions contain ∼23 atom% of P, ∼33 atom% of Fe, ∼43 atom% of Ni, and ∼0.7 atom% of Co. Plessite structure contains the average Ni concentration of ∼17 atom% while detailed EDS analysis shows: (i) the lowest Ni concentrations of ∼5 to ∼8 atom%, (ii) the intermediate Ni concentrations of ∼9 to ∼19 atom%, and (iii) the highest Ni concentration up ∼38 atom% (some individual micro‐grains demonstrate up to ∼47 and ∼59 atom% of Ni) that may indicate the presence of the (i) α‐Fe(Ni, Co), (ii) α2‐Fe(Ni, Co), and (iii) γ‐Fe(Ni, Co) phases. These may be a result of the γ‐phase decomposition with mechanism γ → α + α2 + γ that indicates a slow cooling rate for Mundrabilla IAB‐ung iron meteorite. The presence of ∼98.6 wt% of the α‐Fe(Ni, Co) phase and ∼1.4 wt% of the γ‐Fe(Ni, Co) phase is found by XRD while schreibersite is not detected. Magnetization measurements show the saturation magnetization moment of Mundrabilla IAB‐ung of 188(2) emu g−1 indicating a low average Ni concentration in Fe‐Ni‐Co alloy. Mössbauer spectrum of the bulk Mundrabilla powder demonstrates five magnetic sextets related to the ferromagnetic α2‐Fe(Ni, Co), α‐Fe(Ni, Co), and γ‐Fe(Ni, Co) phases and one singlet associated with the paramagnetic γ‐Fe(Ni, Co) phase, however, there are no spectral components corresponding to schreibersite. Basing on relatively larger and smaller values of the magnetic hyperfine field, two magnetic sextets associated with γ‐Fe(Ni, Co) phase can be related to the disordered and more ordered γ‐phases. The iron fractions in the detected phases can be roughly estimated as follows: (i) ∼17.6% in the α2‐Fe(Ni, Co) phase, (ii) ∼68.5% in the α‐Fe(Ni, Co) phase, (iii) ∼11.5% in the disordered γ‐Fe(Ni, Co) phase, (iv) ∼2.0% in the more ordered γ‐Fe(Ni, Co) phase, and (v) ∼0.4% in the paramagnetic γ‐Fe(Ni, Co) phase.
- Subjects
IRON meteorites; MAGNETIZATION measurement; MOSSBAUER spectroscopy; SCANNING electron microscopy; X-ray diffraction; HYPERFINE interactions; IRON clusters
- Publication
Meteoritics & Planetary Science, 2023, Vol 58, Issue 10, p1552
- ISSN
1086-9379
- Publication type
Article
- DOI
10.1111/maps.14070