The Nature of the Elongated Form of Diamond Crystals From Urals Placers
- 1 — Saint-Petersburg Mining University ▪ Orcid
- 2 — VSEGEI
- 3 — Saint-Petersburg Mining University
- 4 — VSEGEI
Abstract
The article presents the results of a study of the internal structure of highly elongated diamond crystals from placers in the Krasnovishersky district of the Urals. Very elongated crystals are found within diamond-bearing placer with unrevealed primary sources. Determining the conditions of such crystals formation can help one to determine the primary deposits type. There are three hypotheses for the formation of the elongated shape of such crystals: 1) crys- tals initially elongated along the <100> (strongly distorted octahedra); 2) individual crystals of columnar aggregates; 3) elongated crystals fragments. To study the internal structure, we selected three most elongated individuals of the 155 crystals samples. The study of the internal structure of selected crystals with the usage of photoluminescent (PL) tomography, cathodoluminescence (CL), and optical microscopy has shown that these samples are fragments of lar- ger single crystals. CL imaging allowed to determine slip lines within the crystal's volume. The recorded PL spectra show the 912, 946, and 986 nm peaks, which are characteristic of crystals with plastic deformation. The revealed fea- tures are indicators of plastic deformation accompanying the destruction of the crystals. The significant dissolution following the destruction of the crystals led to the rounding of the vertices and edges of their fragments. Apparently, most of the very elongated crystals from placers with unknown sources are also highly dissolved isometric crystal fragments. The obtained results have shown that the deformation and dissolution of diamond crystals are related events characteristic of diamonds from hitherto undetected, but highly productive primary deposits.
References
- Beskrovanov V.V. Ontogeny of Diamond. Novosibirsk: Nauka, 2000, p. 165.
- Vasilev E. A. Luminescense of Plastically Deformed Diamond in the Range 800-1050 nm. Journal of Applied spectroscopy.
- Vol. 86. N 3, p. 512-515.
- Vasilev E.A., Kozlov A.V., Petrovsky V.A. Volume and Surface Distribution of Radiation Defect in Natural Diamonds.
- Zapiski Gornogo instituta, 2018. Vol. 230, p. 107-115. DOI: 10.25515/PMI.2018.2.107.
- Zhabin A. G. Ontogeny of Minerals (aggregates). Moscow: Nauka, 1979, p. 275 (in Russian).
- Zintchouk N. N., Koptil V. I. Typomorphism of the Siberian platform diamonds. Moscow: Nauka, 1979, p. 275 (in Russian).
- Kuharenko A.A. Almazy Urala. Moscow: Gosgeoltehizdat, 1955, p. 510 (in Russian).
- Afanas’ev V.P., Nikolenko E.I., Tychkov N.S., Titov A.T., Tolstov A.V., Kornilova V.P., Sobolev N.V. Mechanical abrasion of kimberlite indicator minerals: Experimental investigations. Russian Geology and Geophysics. 2008. Vol. 49. N 2, p. 91-97.
- Orlov Yu.L. The Mineralogy of the Diamond. New York: Wiley and Sons, 1977, p. 235.
- Rakin V.I. Real octahedrons of diamond. Vestnik IG Komi SC Ub RAS. 2013. N 6, p. 6-9 (in Russian).
- Fersman A.E. Kristallgrafiya Almaza. Leningrad: Izdatelstvo Akademii Nauk SSSR, 1955. p. 566 (in Russian).
- Khokhryakov A.F., Pal'yanov Yu.N., Sobolev N.V. Crystal morphology as an indicator of redox conditions of natural diamond dissolution at the mantle PT parameters. Doklady Earth Sciences. 2002. Vol. 385. N 5, p. 534-537.
- Gaillou E., Post J.E., Rose, T., Butler J.E. Cathodoluminescence of Natural, Plastically Deformed Pink Diamonds. Micros- copy and Microanalysis. 2012. Vol. 18, p. 1292-1302.
- Dishler B. Handbook of spectral lines in diamond. Springer-Verlag, Berlin Heidelberg, 2012, p. 467.
- Mironov V.P. Regularities in the internal structure of diamonds of the Malaya Botuobia kimberlite field. Journal of Mining Science. 1993. Vol. 29. N 3, p. 294-300.
- Shchukina E.V., Agashev A.M., Kostrovitsky S.I., Pokhilenko N.P. Metasomatic processes in the lithospheric mantle be- neath the V.Grib kimberlite pipe (Arkhangelsk diamondiferous province, Russia). Russian Geology and Geophysics. 2015. Vol. 56, p. 1701-1716.
- Smith C.B., Bulanova G.P., Kohn S.C., Milledge H.J., Hall A.E., Griffin B.J., Pearson G.D. Nature and genesis of Kali- mantan diamonds. Lithos. 2009. Vol. 112S, p. 822-832.
- Gaillou E., Post J.E., Bassim N., Fries M., Rose T., Stroud R., Butler J.E. Spectroscopic and microscopic characterization of color lamellae in natural pink diamonds. Diamond and Related Materials. 2010. Vol. 19, p. 1207-1220.
- Zaitsev A.M. Optical Properties of Diamond: Data Handbook. Berlin: Springer, 2001, p. 502.