Plastic deformation of lower mantle diamonds by inclusion phase transformations

摘要

The changes in pressure (P) and temperature (T) conditions experienced by a natural diamond, as it rises to shallower depths and is eventually erupted at the Earth’s surface, give rise to stresses between the diamond and any inclusions it contains as a consequence of their differing changes in volume cell parameters in response to P and T. In the case of diamonds with lower-mantle silicate inclusions such effects will be markedly enhanced by phase transformations by which MgSi-perovskite and CaSi-perovskite transform to pyroxene, pyroxenoid and other phases. Using micro-Raman and SEM-EBSD techniques, we have carried out investigations of the diamond immediately adjacent to inclusions with lower mantle perovskite chemical compositions, and compared them with studies of lower-mantle ferropericlase and upper-mantle inclusions.