| Research Abstract |
In this research, we clarified the phase transitions and partitioning of elements in mantle minerals in the transition zone and the lower mantle, i.e., stability of hydrous phases, melting and physical properties of magma, phase transition kinetics, core formation process in the early Earth. One of the important results in this study is on the stability of hydrous phases. We observed two new hydrous minerals which are expected to exist in the lower mantle ; i.e., phase G (Mg1.14Si1.73H2.81O6) and phase d-AlOOH.Phase G is stable at relatively low temperature around 1000-1200℃ at around 25 GPa and it is expected to exist in the peridotite layer in the cold slab descending into the lower mantle. Whereas phase delta AlOOH is stable in the sediment components in the descending slabs in the upper most part of the lower mantle. These phases work as the water carrier into the lower mantle. Another mportant results in this research is on decomposition kinetics of ringwoodite. We observed periclase and ilmenite, and priclase and stishovite as a metastable assemblage in the beginning of the decomposition of ringwoodite. These metastable assemblages eventually disappeared within 10 minutes to form stable assemblage, i.e., periclase and perovskite.
|
