¹D. Fernandes,^1,2N. G. Rudraswami,¹M. Pandey,^1,2V. P. Singh
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14143]
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa, India
²Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
Published by arrangement with John Wiley & Sons

Fe-rich relict olivine grains are found in a small percentage of cosmic spherules, which are studied here to determine the nature of their precursors. We examined 128 Fe-rich relict olivine grains with Fa >10 mol% from 53 cosmic spherules of different types collected from Antarctica (Antarctica micrometeorites [AMM]) and deep-sea sediments (DSS) of the Indian Ocean. Fe-rich olivines identified in cosmic spherules are close analogs of type II chondrule olivines formed in the early solar system. The olivine analysis shows well-defined trends in molar Fe/Mn versus Fe/Mg with an affinity for ordinary and carbonaceous chondrites. The minor oxides in olivine are in ranges such as MnO ~0.1–0.8 wt%, Cr2O3 ~0–0.7 wt%, CaO ~0–0.6 wt%, and Al2O3 ~0–0.2 wt%, respectively. The chemical composition suggests that the precursors for these Fe-rich olivine-bearing cosmic spherules consist of ordinary chondrites (~21%–23%, AMM-DSS), carbonaceous chondrites (~17%–36%, AMM-DSS), and a large fraction overlapping both carbonaceous and ordinary chondrites (~41%–62% AMM-DSS). The elemental ratios Fe/Si/CI and Mg/Si/CI for the Fe-rich relict olivines ranging between the values 0.5–1.0 and 1.1–1.7 are compatible with IDPs, Comet 81P/Wild 2 as well as the Asteroid Itokawa and Ryugu, which are indistinguishable from carbonaceous and ordinary chondrites. In addition, pyroxene and olivine assemblages in their Fa versus Fs mol% show strong similarities to EOC chondrites. Our results on Fe-rich relict olivines show that these grains in cosmic spherules are less common than Mg-rich olivines, which show a narrow range of chemical compositions identical to those from ordinary chondrites and carbonaceous chondrites, indicating a supplementary contribution of an ordinary chondritic component to the micrometeorite source of dust.

¹Christian Vollmer,^2,3Demie Kepaptsoglou,^4,5Jan Leitner,²Aleksander B. Mosberg,^2,3Khalil El Hajraoui,⁶Ashley J. King,^6,7Charlotte L. Bays,⁶Paul F. Schofield,^8,9Tohru Araki,^2,10Quentin M. Ramasse
Nature Communications 15, 778 Open Access Link to Article [DOI
https://doi.org/10.1038/s41467-024-45064-x%5D
¹Institut für Mineralogie, Universität Münster, Münster, Germany
²SuperSTEM Laboratory, Keckwick Lane, Daresbury, UK
³School of Physics, Engineering and Technology, University of York, Heslington, UK
⁴Institut für Geowissenschaften, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
⁵Max Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany
⁶Planetary Materials Group, Natural History Museum, London, UK
⁷Department of Earth Sciences, Royal Holloway, University of London, Egham, UK
⁸Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
⁹National Institutes of Natural Sciences, Institute for Molecular Science, UVSOR Synchrotron Facility, Okazaki, Japan
¹⁰School of Chemical and Process Engineering and School of Physics and Astronomy, University of Leeds, Leeds, UK

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