COMPOSITIONAL EVOLUTION OF MICROCRYSTALLINE AND MACROCRYSTALLINE ILMENITE IN KIMBERLITE

Abstract

To study the composition of the different ilmenite generations and clarify their evolutionary patterns, we sampled 28 kimberlite pipes in different fields of Siberia. In all, we analyzed 200 microcrystalline ilmenite grains and, within each kimberlite sample, studied those ranging in size from 0.3 mm to 10 μm. The results indicate a wide compositional variability of the mineral. Analysis of ilmenite microinclusions in diamond that are comparable to microcrystalline ilmenite grains in the kimberlite cement, suggest that they crystallized at lower temperature and pressure. This assumption is valid at least for diamond generations paragenetically related to ilmenite.