Home-made MicroRaman spectrometer
with hydrothermal DAC
Kanzaki, M. and Xue, X. (2017) Protoenstatite in MgSiO3 samples prepared by conventional solid state reaction, J. Mineral. Petrol. Sci., 112, 359-364. Link to paper
Protoenstatite is generally beleaved as unquenchable phase to ambient temperature. Enstatite (MgSiO3) sample was prepared by conventional solid state reaction at 1500 C, followed by cooling to ambient temperature with four different cooling rates (0.04–500 K/s). Quantitative analysis of enstatite phases in the samples by the Rietveld refinement and 29Si MAS NMR revealed that a large amount of metastable protoenstatite (30–40 mol%) along with clinoenstatite was preserved in all samples. The crystal structures of protoenstatite and clinoenstatite at room temperature were refined using the Rietveld method, and were essentially the same as those reported by previous studies. As the solid state reaction method employed in this study is commonly used to prepare synthetic clinoenstatite, the present result implies that the ‘clinoenstatite’ starting materials used in previous phase equilibrium studies of MgSiO3 pyroxene might contain overlooked protoenstatite, which could affect the interpretation for phase transition and thus those results should be reexamined.