Nitrogen in the deep mantle

相对于地球上的其他挥发性元素，氮似乎高度贫化。然而，我们实验室最近的数据表明，仅上地幔就可能储存比目前大气中多20 - 50倍的氮。再加上一些观察结果，例如现今的氮俯冲和脱气之间的不平衡，这表明大气中的氮含量以及大气压可能在地质时期发生了变化。为了进一步限制氮在深部地幔中的潜在储存，应通过实验研究过渡区矿物（硅镁石、菱锰矿、镁橄榄石）和下地幔矿物（硼镁石、CaSiO 3钙钛矿）中的氮溶解度。矿物将在多砧实验中与富氮流体平衡合成，随后通过西姆斯（二次离子质谱法）进行分析。偏振FTIR和拉曼光谱，以及单晶X射线衍射将被用来约束氮的溶解机制。将建立地幔中氮储存量和氮平衡分布的热力学模型。

Nitrogen appears highly depleted relative to other volatile elements on Earth. However, recent data from our laboratory suggest that the upper mantle alone may be able to store 20 - 50 times more nitrogen than presently resides in the atmosphere. Together with a number of observations, e.g. an imbalance between present-day nitrogen subduction and degasing, this suggests that the amount of nitrogen residing in the atmosphere and therefore the bulk atmospheric pressure may have changed over geologic time. To further constrain the potential storage of nitrogen in the deep mantle, nitrogen solubility in the minerals of the transition zone (wadsleyite, ringwoodite, majorite) and of the lower mantle (bridgmanite, CaSiO3 perovskite) shall be experimentally investigated. Minerals will be synthesized in equilibrium with a nitrogen-rich fluid in multi-anvil experiments and subsequently be analysed by SIMS (secondary ion mass spectrometry). Polarized FTIR and Raman spectroscopy, as well as single-crystal X-ray diffraction will be used to constrain the solubility mechanism of nitrogen. Thermodynamic models will be developed for the nitrogen storage capacity and the equilibrium nitrogen distribution in the mantle.