Characterization of carbon phases in Yamato 74123 ureilite to constrain the meteoriteshock history

1Anna Barbaro,2,3Fabrizio Nestola,4Lidia Pittarello,4Ludovic Ferrière,5Mara Murri,6Konstantin D. Litasov,2Oliver Christ,1Matteo Alvaro,1M. Chiara Domeneghetti
American Mineralogist 107, 377-384 Link to Article [DOI: https://doi.org/10.2138/am-2021-7856]
1Department of Earth and Environmental Sciences, University of Pavia, Via A. Ferrata 1, I-27100 Pavia, Italy
2Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padova, Italy
3Geoscience Institute, Goethe-University Frankfurt, Altenhöferallee 1, 60323 Frankfurt, Germany
4Department of Mineralogy and Petrography, Natural History Museum, Burgring 7, 1010 Vienna, Austria
5Department of Earth and Environmental Sciences, University of Milano-Bicocca, I-20126 Milano, Italy
6Vereshchagin Institute for High Pressure Physics RAS, Troitsk, Moscow, 108840 Russia
Copyright: The Mineralogical Society of America

The formation and shock history of ureilite meteorites, a relatively abundant type of primitive
achondrites, has been debated for decades. For this purpose, the characterization of carbon phases
can provide further information on diamond and graphite formation in ureilites, shedding light on the
origin and history of this meteorite group. In this work, we present X‑ray diffraction and micro‑Raman
spectroscopy analyses performed on diamond and graphite occurring in the ureilite Yamato 74123
(Y-74123). The results show that nano- and microdiamonds coexist with nanographite aggregates.
This, together with the shock-deformation features observed in olivine, such as mosaicism and planar
fractures, suggest that diamond grains formed by a shock event (≥15 GPa) on the ureilitic parent
body (UPB). Our results on Y-74123 are consistent with those obtained on the NWA 7983 ureilite and
further support the hypothesis that the simultaneous formation of nano- and microdiamonds with the
assistance of a Fe-Ni melt catalysis may be related to the heterogeneous propagation and local scat –
tering of the shock wave. Graphite geothermometry revealed an average recorded temperature (Tmax)
of 1314 °C (±120 °C) in agreement with previously estimated crystallization temperatures reported
for graphite in Almahata Sitta ureilite.

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