Diamond Resorption Morphology and Applications: a Review
Diamond Resorption Morphology and Applications: a Review
Previously Published Material: This review referes to some published or submitted experimental data. However, the content and findings of this presentation have not been published or submitted.
Abstract ID#: 34918
English Abstract:
Diamond resorption morphology reflects the conditions of diamond reaction with the host kimberlite magma and with metasomatic agents in the mantle. During the last decade experimental studies combined with application of new analytical method of atomic force microscopy (AFM) provided new quantitative data and notably extended our understanding of this process. I will discuss types of morphological transformations of diamond, what do we know from experiments and see on natural stones, and what can we learn about the conditions in natural diamond-hosting environments from diamond morphology. The study uses experimental data simulating three stages in diamond history: 5 – 7 GPa runs examine conditions during the mantle residence, 1- 3 GPa runs examine conditions during kimberlite emplacement, and runs at 0.1 MPa examine diamond resorption in near surface conditions after the emplacement. Diamond resorption causes transformation of crystal morphology and development of etch feature on the crystal surface. The type of morphological changes depends on the composition of the reacting media, whereas the degree of rounding depends on the pressure and gives an estimate of the depth of the fluid exsolution in different kimberlite magmas. The surface features include negative trigons, as well as positive trigons, tetragonal and circular pits, terraces, and cavities with surface graphitization. AFM based classification of the trigons reflects their evolution, the reaction conditions, and gives an estimate of H2O:CO2 ratio and the temperature of the reacting fluid. Positive trigons are a feature of near-surface resorption and occur only in limited number of diamond populations, and the circular pits can serve as indicators of low-pressure aqueous fluid. Morphology of natural diamonds is used to assess the importance of their reaction with carbonatitic melts, silicate aqueous melt / fluid, and CHO fluid (with variable H2O:CO2 ratio) on diamond road from the mantle to the surface.