Structural peculiarities, mineral inclusions, and point defects in yakutites—A variety of impact-related diamond

1,2Andrei A. Shiryaev,3Anton D. Pavlushin,4,5Alexei V. Pakhnevich,6Ekaterina S. Kovalenko,1Alexei A. Averin,7Anna G. Ivanova
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13791]
1A. N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Leninsky pr. 31 korp. 4, Moscow, 119071 Russia
2Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Moscow, 119017 Russia
3Diamond and Precious Metal Geology Institute, Siberian Branch of RAS, Lenin pr. 39, Yakutsk, 677000 Russia
4Paleontological Institute RAS, Profsoyuznaya str. 123, Moscow, 117997 Russia
5The Frank Laboratory of Neutron Physics, JINR, Dubna, 141980 Russia
6NRC “Kurchatov Institute,”, Kurchatov square 1, Moscow, 123182 Russia
7Shubnikov Institute of Crystallography FSRC “Crystallography and Photonics” RAS, Leninsky pr. 53, Moscow, 119333 Russia
Published by arrangement with John Wiley & Sons

An unusual variety of impact-related diamond from the Popigai impact structure—yakutites—is characterized by complementary methods including optical microscopy, X-ray diffraction, radiography and tomography, infrared, Raman, and luminescence spectroscopy providing structural information at widely different scales. It is shown that relatively large graphite aggregates may be transformed to diamond with preservation of many morphological features. Spectroscopic and X-ray diffraction data indicate that the yakutite matrix represents bulk nanocrystalline diamond. For the first time, features of two-phonon IR absorption spectra of bulk nanocrystalline diamond are interpreted in the framework of phonon dispersion curves. Luminescence spectra of yakutite are dominated by dislocation-related defects. Optical microscopy supported by X-ray diffraction reveals the presence of single crystal diamonds with sizes of up to several tens of microns embedded into nanodiamond matrix. The presence of single crystal grains in impact diamond may be explained by chemical vapor deposition–like growth in a transient cavity and/or a seconds-long compression stage of the impact process due to slow pressure release in a volatile-rich target. For the first time, protogenetic mineral inclusions in yakutites represented by mixed monoclinic and tetragonal ZrO2 are observed. This implies the presence of baddeleyite in target rocks responsible for yakutite formation.

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