Growth Diamond on an Impact Lonsdaleite-bearing Diamond from the Popigai Astrobleme

Abstract

The Popigai astrobleme contains huge reserves of diamonds with unusual properties. In impact diamonds from the Popigai astrobleme, the cubic phase and lonsdaleite are intergrown. In order to study the relationship of lonsdaleite-bearing impact diamonds with diamond, an experimental study of the features of diamond growth on lonsdaleite-bearing fragments was carried out. The experiments were carried out on a high-pressure apparatus of the “BARS” type at 5.5 GPa and 1450 ° C in the Fe-Ni-C system (nickel 36 wt.%). Impact Popigai diamonds were used as seed crystals. As a result of the study, it was found that the newly formed crystals are represented by a cubic phase, while the lonsdaleite in the seed crystals was preserved and the lonsdaleite / diamond ratio did not change. The newly formed cubic diamond in its main properties (Raman spectra, morphology, color, etc.) corresponds to synthetic diamonds grown in the iron-nickel system. The difference between the growth of crystals on seeds of impact diamonds and growth on a single-crystal seed of diamond was that the nucleation of crystals began from different points of the seed of the impact diamond. Multi-headed growth was observed and, as a result, an intergrowth of diamond crystals was formed. Probably, the initial misorientation of the points of nucleation of subindividuals leads to multi-headed growth of crystals in an intergrowth, in contrast to single-crystal growth of diamond on a single- crystal seed.