A structural insight into the Chelyabinsk meteorite: neutron diffraction, tomography and Raman spectroscopy study

Abstract

The internal structural organization and phase composition of a fragment of the Chelyabinsk meteorite have been studied using neutron diffraction, tomography methods, optical microscopy, and Raman spectroscopy. The bulk mineral composition of the meteorite and spatial distribution of different components were determined. In addition to previously found phases of olivine, orthopyroxene, plagioclase and troilite, the obtained data of optical microscopy and neutron diffraction provide evidence of the presence of kamacite phase in the studied meteorite fragment. The heterogeneous distribution of the iron in the olivine and orthopyroxene phases was observed, the morphological calculations were used to analyze the spatial arrangement of metal components.

The structural analysis of Kunya‐Urgench chondrite: The nondestructive neutron studies

“…This value is close to the corresponding one for α‐iron, which indicates a low nickel content in kamacite. The estimation of the nickel content (Kichanov et al., 2019; Morrison et al., 2018) gives an average value of 2.7(5)%, which is significantly lower than in the Seymchan pallasite (Kichanov et al., 2018) or the Chelyabinsk chondrite (Kichanov et al., 2019). The scanning by neutron diffraction at various points or gauge volumes of the chondrite fragment revealed a very small deviation of the nickel content in the kamacite phase within ±0.5%, which does not exceed the measurement error.…”

“…It should be noted that neutron diffraction is quite sensitive to the difference in iron and magnesium content due to the scattering length of those nuclei varies by a factor of almost two (Sears, 1992). Therefore, it is surprising that the iron content in the olivine and pyroxene phases is quite low, even in comparison with earlier data (Kichanov et al, 2019;Krot et al, 2009).…”

“…It is possible to analyze the volumetric and morphological features of the studied meteorite using the obtained 3-D neutron data (Ebel & Rivers, 2007;Kichanov et al, 2018Kichanov et al, , 2019. The total 3-D reconstructed volume of the fragment of the Kunya-Urgench meteorite consists of 157,197,884 voxels, which corresponds to the volume of 22,103.28 mm 3 .…”

“…From this point of view, neutron structural diagnostic methods have become more and more popular and appropriate experimental approaches for studying rare objects such as meteorites (Lehmann & Kaestner, 2009; Lehmann et al., 2014; Podurets et al., 2021). Along with classical traditional approaches, neutron methods provide reliable data on the chemical and mineral composition of meteorite fragments, the spatial distribution of internal chemical or structural components (Hezel, Elangovan, et al., 2013; Hezel, Friedrich, et al., 2013; Kichanov et al., 2019; Lehmann & Kaestner, 2009). The fundamental difference in the nature of neutron interaction with matter compared to X‐rays provides additional benefits to neutron methods, including sensitivity to light elements, a notable difference in contrast between isotopes and high penetration effect through metals or heavy elements (Lehmann & Kaestner, 2009; Podurets et al., 2021).…”

“…The determination of major and minor phases, their textural associations, dimensions, shapes, and spatial arrangement is important for the petrology of meteorites. Taking into account the presence of metallic iron-nickel component, direct Xray diffraction, or tomographic experiments may be limited by the strong absorption of X-ray radiation in large fragments of pallasites or chondrites (Kichanov et al, 2018(Kichanov et al, , 2019Peetermans et al, 2013). From this point of view, neutron structural diagnostic methods have become more and more popular and appropriate experimental approaches for studying rare objects such as meteorites (Lehmann & Kaestner, 2009;Lehmann et al, 2014;Podurets et al, 2021).…”