CHROMATOGRAPHIC STUDY OF DIAMOND ETCHING IN KIMBERLITIC MELTS IN THE CONTEXT OF DIAMOND NATURAL STABILITY

Abstract

The morphology of diamond crystals during resorption in the silicate melt at high PT parameters depends on a fluid presence in the system. This is related to the fact that refraction in the <110> direction of a rounded surface of etching, which, to a first approximation, corresponds to the form {110} and appears at the site of octahedron edges, depends on the ratio H2O/(CO2 + CO). At a high value of this ratio, the diamond resorption proceeds through ditrigonal etching layers, giving rise to a face suture on surfaces {110}. Values of the ratio H2O/(CO2 + CO) in kimberlite samples, which were established by chromatographic analysis, approach after the experiment the conditions under which octahedral diamond crystals resorb through trigonal layers. The correlation of experimental results with the natural material suggests that diamonds from kimberlites and lamproites experienced resorption and the process was so intense that it affected not only the morphology of crystals but also the diamond potential of kimberlites in general. It was water that acted as the main reagent to resorb diamonds. As its concentration increased, so did the intensity of the process. The increase in the carbon dioxide content assisted not only a change in the type of diamond morphogenesis upon resorption but also a decrease in the depth of the process itself.