In this study, we investigated the phase stability of Al-free and Al-bearing superhydrous phase B (shy-B) up to 55 GPa and 2500 K. In comparison with Al-free shy-B, the incorporation of 11.7 wt.% Al₂O₃ in shy-B expands the stability by ∼400–800 K at 20–30 GPa. The determined dehydration boundary for Al-bearing phase D indicates that it could be present even at normal mantle geotherm conditions at 30–40 GPa. Up to 23.8 mol.% Al₂O₃ can be dissolved into the structures of akimotoite and bridgmanite as a result of the decomposition reactions of Al-bearing shy-B and phase D between 20 and 40 GPa. Results of further experiments indicate that δ-AlOOH is the stable hydrous phase coexisting with Al-depleted bridgmanite at pressures above 52 GPa. This study shows that the incorporation of Al in dense hydrous magnesium silicates can have a profound impact on our picture of the water cycle in the deep Earth.

中文翻译：

---

最上层下地幔条件下含铝致密水合硅酸镁的相稳定性：对地幔中水输运的影响

在这项研究中，我们研究了高达 55 GPa 和 2500 K 的无铝和含铝超水相 B (shy-B) 的相稳定性。与无铝 shy-B 相比，掺入量为 11.7 wt.% shy-B 中的Al ₂ O ₃在 20-30 GPa 下将稳定性扩大了 ~400-800 K。确定的含铝相 D 的脱水边界表明，即使在 30-40 GPa 的正常地幔地热条件下，它也可能存在。高达 23.8 mol.% Al ₂ O ₃由于含铝的 shy-B 和 D 相在 20 和 40 GPa 之间的分解反应，可以溶解到 akimotoite 和 Bridgmanite 结构中。进一步的实验结果表明，δ-AlOOH 是在 52 GPa 以上的压力下与贫铝布里奇曼石共存的稳定含水相。这项研究表明，在致密的水合硅酸镁中掺入铝会对我们对地球深处水循环的描绘产生深远的影响。