Nano-Micromorphology and Anatomy of Impact Apographitic Diamonds from Bilylivka (Zapadnaya) Astrobleme (the Ukrainian Shield)

UDC 549.211 (477)

https://doi.org/10.15407/mineraljournal.37.04.036

V.M. Kvasnytsya (1), R. Wirth (2), S.M. Tsymbal (1)

(1) M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine

34, Acad. Palladina Pr., Kyiv-142, Ukraine, 03680

E-mail: vmkvas@hotmail.com

(2) Helmholtz-Centre Potsdam, German Research Centre for Geosciences,

GFZ Telegrafenberg, Potsdam, Germany, 14473

E-mail: wirth@gfz-potsdam.de

Nano-Micromorphology and Anatomy of Impact Apographitic Diamonds from Bilylivka (Zapadnaya) Astrobleme (the Ukrainian Shield)

Language: Ukrainian

Mineralogical journal 2015, 37 (4): 36-45

Abstract: Nano-micromorphology and anatomy of impact apographitic diamonds (paramorphoses) from Bilylivka (Zapadnaya) astrobleme in the Ukrainian Shield have been studied. The methods of scanning and transmission electron microscopy were used. Nine individual black, black-grey and light-yellowish paramorphoses have been studied. Impressive images of nanomicromorphology and anatomy for black paramorphoses with alleged high content of lonsdaleite phase were acquired and displayed in the article. Sculptural patterns consisting of multiple, rounded rectangular plates, strictly oriented along [101 – 0] are developed on the (0001) surface of these paramorphoses. The size of plates along their extension is aproximately 50 nm. The intensively dissolved (0001) surface of black paramorphoses is covered with numerous rounded rectangular pits (up to 0.5 μm), and strictly oriented along [101 – 0]. The shape and orientation of the plates and pits on the (0001) surface of paramorphoses allow us to refer them to the morphological manifestation of lonsdaleite phase. They can evidence for a martensitic transformation (0001) plane of the original graphite to the plane (101 – 0) of the newly formed lonsdaleite. That is, when a solid phase transformation of graphite under high load takes place then an orientation relationship between the original and newly formed phases is formed — the (101 – 0) plane of lonsdaleite parallel to (0001) plane of graphite. The unique phenomenon — the growth of numerous diamond nano-micropolyhedrons on the (0001) surface of black-grey paramorphose is fixed. The polyhedrons are presented by octahedrons and their intergrowths. They are distributed on the (0001) surface, randomly on flat areas and in the pits. The intergrowths (growth twins and nucleation twins on (111)) and irregular intergrowths of octahedrons are identified. The faces and edges of octahedrons are covered with nanoscale globules. The size of globules is up to 40 nm. They consist of many particles with the smallest size of 1 nm. This may be an evidence of a cluster growth of diamond crystals, but on the issue of this unusual growth of polyhedrons is no clarity. The size of crystals rarely exceeds one micron. Diamond is confirmed by the octahedral form of the crystals, their intergrowths and by chemical composition, based on the data of X-ray analysis of the largest octahedrons. It suggests the formation of diamond crystals from the vapor phase after the solid-phase transition of graphite to the new phase. The study of ultrathin foils (15 × 10 × 0.2 μm) cut from the paramorphoses perpendicular to the (0001) plane allows us to reveal their anatomy — to receive the images of polysynthetic twinning and polycrystalline structure of its twins. The twins are formed on the (112 – 1) plane, the size of its crystallites is up to 30 nm. Elements of the internal structure of black paramorphoses sometimes may be fixed on the surfaces (101 – 0) with nano-micromorphological studies. The twins can be observed on the (0001) surfaces of paramorphoses by parallel striation along [101 – 0], sometimes symmetrically through 60о. Installed nano-micromorphological and anatomical characteristics of the impact diamonds from Bilylivka astrobleme are direct evidence of a solid phase transition of graphite into lonsdaleite-diamond under high shock load by martensitic mechanism.

Keywords: impact apographitic diamond, paramorphose, nano-micromorphology, anatomy, twin, nano-diamond, lonsdaleite, Bilylivka (Zapadnaya) astrobleme, the Ukrainian Shield.

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