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The fate of ammonium in phengite at high temperature

机译：在高温下磷酸盐中铵的命运

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Nitrogen (N) is the main component of the atmosphere and is largely considered as a volatile element. However, most researchers now agree that a significant amount of N, in the form of ammonium (NH4+) substituting for K+ in some K-bearing minerals such as clays, micas, and feldspars, can be transferred to the deep Earth through subduction. The fate of ammonium in those minerals during subduction is still poorly known but is likely controlled by temperature and pressure pathways. In an attempt to contribute to understanding the fate of N during high-temperature processes, we carried out in situ high-temperature IR and Raman spectra measurements to investigate the rate and mechanism of NH4+ loss in phengite. We observed that a new OH band at 3425 cm(-1) became prominent above 400 degrees C, and did not change with times during isothermal annealing at 500 and 700 degrees C. The N-H stretching band shifted to higher wavenumbers in the temperature interval from -150 to 20 degrees C, while linearly shifted to lower wavenumbers in the temperature interval from 20 to 500 degrees C and remained stable above 500 degrees C. The N-H bending band linearly shifted to lower wavenumbers in the temperature interval from -150 to 400 degrees C and remained stable. The K-O stretching frequency decreased with increasing temperature to 600 degrees C, and then remained stable. These processes were reversible until dehydration and ammonium loss from phengite starting at 800 degrees C. The results suggest that (1) at low temperatures, ammonium is ordered and hydrogen bonding between ammonium and the framework evolves during cooling; (2) at high temperatures, the N-H interatomic distance of NH4+ lengthens with increasing temperature until 500 degrees C. N-H bond subsequently no longer lengthens, accompanied by H transferring from N to neighboring O and forming a new OH band at 3425 cm(-1). At 800 degrees C, H+ starts breaking from N and leaving others to form NH3 and OH-. This study has impl
机译：氮气（N）是大气的主要成分，主要被认为是挥发性元素。然而，大多数研究人员现在一致认为，在一些K轴承矿物如粘土，云母和长石等k +含k +的铵（NH4 +）中，铵（NH 4 +）的形式可以通过俯冲转移到深地。在俯冲期间的那些矿物中的铵的命运仍然是清楚的，但可能受到温度和压力途径的控制。试图有助于在高温过程中理解N的命运，我们以原位高温IR和拉曼光谱测量进行，以研究峰值NH4 +损失的速率和机制。我们观察到，3425厘米（-1）的新OH频段以来突出400摄氏度，并且在500和700摄氏度的等温退火期间没有随时间改变。NH拉伸带在温度间隔中移位到更高的波数-150至20℃，而在温度间隔中线性移动到从20到500℃的温度间隔偏移，并且保持高于500℃的稳定性。NH弯曲带在-150至400度的温度间隔中线性地移位到下波数C并保持稳定。 K-O拉伸频率随温度的增加降低至600℃，然后保持稳定。这些方法是可逆的，直至从800℃开始脱水和从磷酸盐开始的脱水和铵损失。结果表明（1）在低温下，在冷却期间铵和骨架之间的氢键在冷却期间进化铵。 （2）在高温下，NH4 +的NH间隙距离随着温度的增加而延长，直至500℃，NH键随后不再延长，伴随着从N转移到相邻O并在3425cm处形成新的OH带（-1 ）。在800℃下，H +开始从n断开并留下其他形成NH3和OH-。这项研究有魔术

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