Ammonium Impacts on Vibrations of Hydroxyl and Lattice of Phengite at High Temperature and High Pressure

• 作者: Weihua Huang Yan Yang Zeming Qi Wendi Liu Zhongping Wang Yan Liu Qunke Xia
• 来源期刊: 地球科学学刊（英文版）
• 年，卷（期）: 2021,（5）
• 页码范围: 1278-1286
• 页数: 9页
• 语种: 英文

摘要

Dehydration in hydrous phases of the downgoing slab controls water release processes in sub- duction 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 oC 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 hy- droxyl bonding strength, but hinders hydrogen transition at high temperatures and high pressures. Ammo- nium does not influence the lattice at high pressures either, but delays softening of the lattice at high temper- atures. 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 sub- duction.