鉱物粒界の直視 -高分解能電子顕微鏡観察- Observation of Grain Boundries in Rocks by High-Resolution Transmission Electron Microscopy
Grain boundaries in metamorphic rocks were obsereved by high-resolution transmission electron microscopy. Most of the boundaries have no distinct secondary phases at a nanometer scale. Not only between the same kind of minerals but also between different minerals, mineral grains are directly connected at their boundaries, showing that the structual width of the grain boundaries is less than 0.5nm. Grain boundaries with spheroidal voids are observed in the boundaries. It can be concluded that this type of grain boundary is formed by the healing of microcracks. Low-index plane boundaries are well-developed, showing that this type of boundary has low grain boundary energy. Local structural modification, indicating the segregation of impurities, in grain boundaries is observed. The present results show that the actual width of the grain boundary in rocks is too small for the grain boundary diffusion to be as the dominant transport mechanism.
地學雜誌 108(2), 110-121, 1999-04-25
Tokyo Geographical Society