SOME SPECIFIC FEATURES OF GENESIS OF MICRODIAMONDS OF OCTAHEDRAL AND CUBIC HABIT FROM KIMBERLITES OF THE UDACHNAYA PIPE ( Yakutia ) INFERRED FROM CARBON ISOTOPES AND MAIN IMPURITY DEFECTS
V.N. Reutsky, D.A. Zedgenizov
Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Microdiamonds; crystal habit; growth mechanism; carbon isotopes; Udachnaya kimberlite pipe; Yakutia
Pages: 299-304
Abstract
Microdiamonds (crystals smaller than 1 mm) of octahedral and cubic habit from Udachnaya kimberlite pipe (Yakutia) have been compared in order to distinguish genetic features inferred from carbon isotopic composition and impurity defects. Microdiamonds of cubic habit from the Udachnaya kimberlite pipe have a fibrous internal structure and a high content of nitrogen impurity (400-3000 ppm). Octahedral microdiamonds from the same deposit are distinguished by a low nitrogen content of 0 to 500 ppm and zoning structure. The isotopic composition of carbon (δ13C is -4.7
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