Dehydration in hydrous phases of the downgoing slab controls water release processes in subduction zones. Interplay between volatiles in hydrous minerals has complicated the previous knowledge of their dehydration. Phengite is an essential mineral carrying both hydrogen and nitrogen to the deep Earth. To further understand the link between nitrogen and dehydration process of phengite at an atomic level, we here carry out high temperature and high pressure vibrational spectroscopic investigations on hydroxyl and lattice of ammonium-bearing and ammonium-free phengites. The results show that heating to 800 °C hardly influences hydroxyl bonding strength, whereas pressure induces strengthening of hydrogen bonding until 10 GPa. Moreover, hydrogen transits between the sites with increasing temperature and pressure. The lattice modes soften with increasing temperature and stiffen under compression. Ammonium has no effect on hydroxyl bonding strength, but hinders hydrogen transition at high temperatures and high pressures. Ammonium does not influence the lattice at high pressures either, but delays softening of the lattice at high temperatures. These data unveil behavior of hydroxyl and lattice in phengite at high temperature and high pressure, and also evaluate ammonium impacts, shedding new lights on dehydration processes of phengite during subduction.

下沉板含水阶段的脱水控制俯冲带的水释放过程。含水矿物中挥发物之间的相互作用使先前对其脱水的认识变得复杂。硫铁矿是一种将氢和氮都带到地球深处的重要矿物。为了进一步了解氮与硫原子的脱水过程之间的联系，我们在这里对含铵和不含铵的硫磺的羟基和晶格进行了高温高压振动光谱研究。结果表明，加热至800°C几乎不会影响羟基键合强度，而压力会导致氢键合增强，直至10 GPa。此外，随着温度和压力的增加，氢在两个位点之间迁移。晶格模式随温度升高而软化，并在压缩下变硬。铵盐对羟基键合强度没有影响，但会阻止氢在高温高压下的过渡。铵也不会在高压下影响晶格，但会延迟高温下晶格的软化。这些数据揭示了高温和高压下硫铁矿中羟基和晶格的行为，还评估了铵的影响，为俯冲期间铁矿的脱水过程提供了新的思路。