抄録
Knowledge of the atomic structures of Earth's materials is indispensible for the understanding/modeling of macroscopic geochemical processes. Solid-state NMR spectroscopy offers a rich variety of advanced multi-nuclear, multi-dimensional techniques that can provide not only quantitative information about local structures around different elements (isotopes), but also direct information concerning atomic connectivities. Recently, we have applied some of these techniques to unravel the structures of (1) high-pressure hydrous minerals in the MgO-SiO2-H2O and Al2O3-SiO2-H2O systems (e.g. phase egg, δ-AlOOH, phase D, superhydrous B), which represent potential water reservoirs in the Earth's mantle, and (2) hydrous (alumino) silicate glasses (quenched melts), which serve as analogs for natural magmas. For the hydrous minerals, the states of Si-Al and Si-Mg order/disorder among octahedral sites and hydrogen distribution and hydrogen-bonding distances were clearly revealed. Such information would have been difficult to obtain by any other single technique. For the hydrous aluminosilicate melts, advanced NMR techniques provided the key information needed to end a long-standing controversy concerning the water dissolution mechanisms. Some of these results are summarized here to demonstrate the usefulness and wonder of advanced solid-state NMR spectroscopy.
