Thermal stability of fayalite (Fe2SiO4) is studied at hydrogen pressures up to 7.5 GPa and temperatures up to 400 °C. Powder samples of Fe2SiO4 were exposed to a hydrogen or deuterium atmosphere for 24 h in the Toroid-type apparatus at pre-selected pressures and temperatures followed by quenching to the temperature of liquid nitrogen. The phase and chemical compositions of the quenched samples were examined by energy-dispersive X-ray spectroscopy, X-ray diffraction and Raman spectroscopy at ambient pressure. The chemical composition of volatile products was studied by quadrupole mass spectroscopy in the course of heating from − 196 to 20 °C in a pre-evacuated quartz tube. In these experiments, deuterated samples were used to be sure that the detected compounds could only be formed in the reaction of fayalite with the high-pressure D2 gas. The obtained data allowed us to construct the line of thermal stability of fayalite at hydrogen pressures up to 7.5 GPa. The decomposition temperature of fayalite was proved to nonlinearly decrease from ~ 375 °C at the pressures PH2 = 1.4–2.8 GPa to ~ 175 °C at PH2 = 7.5 GPa. At higher temperatures, fayalite fully decomposed to a mixture of silica, water and metallic Fe or FeH depending on the pressure and temperatures of the hydrogenation.

中文翻译：

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在高氢压下铁橄榄石的破坏和铁和氢化铁的形成

在高达 7.5 GPa 的氢气压力和高达 400 °C 的温度下研究了铁橄榄石 (Fe2SiO4) 的热稳定性。Fe2SiO4 粉末样品在环形装置中在预先选定的压力和温度下暴露于氢或氘气氛中 24 小时，然后淬火至液氮温度。在环境压力下通过能量色散 X 射线光谱、X 射线衍射和拉曼光谱检查淬火样品的相和化学成分。在预抽真空的石英管中从 - 196 到 20 °C 加热的过程中，通过四极杆质谱法研究了挥发性产物的化学成分。在这些实验中，氘化样品用于确保检测到的化合物只能在铁橄榄石与高压 D2 气体的反应中形成。获得的数据使我们能够在高达 7.5 GPa 的氢压下构建铁橄榄石的热稳定性线。铁橄榄石的分解温度被证明从 PH2 = 1.4–2.8 GPa 压力下的~375°C 非线性降低到 PH2 = 7.5 GPa 时的~175°C。在更高的温度下，铁橄榄石根据氢化的压力和温度完全分解为二氧化硅、水和金属 Fe 或 FeH 的混合物。