Almost 600 diamond crystals from Western Russian kimberlite pipes of the Arkhangelsk area and Kola Peninsula and from placer deposits of the Urals and Timan areas were studied with IR spectrometry methods, in order to evaluate the presence of nitrogen and other impurity centers. The crystals differ in thier total nitrogen contents and in the concentration of individual structural impurities according to their provenance. There are differences in the temperature of formation of diamond from each deposit: from 1075-1100°C for the Arkhangelsk suite to 1125-1150°C for the Timan and Urals suites. Diamond crystals with octahedral zoning (tangential mechanism of growth) are characterized by the lowest contents of nitrogen, and have a rather uniform distribution of impurity centers. Samples with combined mechanisms of growth demonstrate a paradoxical relationship between temperatures of formation for the central and marginal zones of the crystals: temperatures calculated for the cores are 15-50°C lower than those estimated for the marginal zones. This paradox is caused by differences in the mechanism of growth. Diamond crystals with octahedral zoning were formed under equilibrium conditions, whereas crystals with normal or combined mechanisms of growth had a rate of crystallization probably higher than the rate of aggregation of nitrogen atoms in the crystals. The latter were formed under non-equilibrium conditions. As a result, values of the temperature of formation determined by IR spectroscopy are only realistic for those crystals that grew under equilibrium conditions. For crystals with normal and combined mechanisms of growth, temperature values calculated from IR data may be unrealistic, as they also depend on the kinetics of the crystallization process.
|Number of pages||14|
|Publication status||Published - Feb 2003|
- Crystal growth
- East European platform
- Infrared absorption