Phase egg (AlSiO 3 OH), an important hydrous phase in the Al 2 O 3 –SiO 2 –H 2 O ternary system, was found in the superdeep diamond from the mantle transition zone. Here, we have investigated the compressibility and the crystal structural evolution of phase egg using the synchrotron-based single-crystal X-ray diffraction and infrared spectroscopy combined with diamond anvil cells up to 32 GPa and 900 K. Present results show that the hydrogen atom flips its position and forms a new hydrogen bond configuration at ~ 14 GPa and room temperature, leading to a first-order phase transition of phase egg, but this behavior is smeared out because of thermal disordering of hydrogen atom at high temperatures. These findings provide important implications for revealing the complex state of hydrogen in the deep earth. Along the cold and warm subducting slab geotherms, the density and bulk velocity of phase egg are greater than those of preliminary reference Earth model in the mantle transition zone, presenting negative buoyancy force for deep-water transportation. Based on the obtained thermal elastic parameters, we further demonstrate that topaz-OH transforms to phase egg with a ~ 11.7% increase in bulk velocity and a ~ 4.2% increase in density, and phase egg decomposes into δ-AlOOH and stishovite with a ~ 6.2% increase in bulk velocity and a ~ 4.0% increase in density under subduction zone conditions.

中文翻译：

---

蛋相状态的热方程 (AlSiO3OH)：对地球深处水相的影响

相蛋 (AlSiO 3 OH) 是 Al 2 O 3 -SiO 2 -H 2 O 三元体系中重要的含水相，在地幔过渡带的超深金刚石中被发现。在这里，我们使用基于同步加速器的单晶 X 射线衍射和红外光谱结合高达 32 GPa 和 900 K 的金刚石砧单元研究了相蛋的可压缩性和晶体结构演变。 目前的结果表明氢原子翻转其位置并在~14 GPa 和室温下形成新的氢键构型，导致相蛋的一级相变，但由于氢原子在高温下的热无序，这种行为被涂抹掉了。这些发现为揭示地球深处氢的复杂状态提供了重要意义。沿着冷暖俯冲板片地温，地幔过渡带相蛋的密度和体积速度大于初步参考地球模型的密度和体积速度，对深水输送呈现负浮力。基于获得的热弹性参数，我们进一步证明黄玉-OH 转变为相蛋，体积速度增加 ~ 11.7%，密度增加 ~ 4.2%，相蛋分解为 δ-AlOOH 和 stishovite，具有 ~在俯冲带条件下，整体速度增加 6.2%，密度增加约 4.0%。