铁方镁石中铁自旋交叉对lower mantle地热的影响
Influence of the iron spin crossover in ferropericlase on the lower mantle geotherm
摘要：
铁方镁石中的铁自旋交叉在其热力学和热弹性性质中引入了异常。在这里，我们调查这些异常如何影响下地幔地热。在地幔聚合物组成的混合物的bridgmanite，铁方镁石，和CaSiO $_3$钙钛矿，不同的Mg/Si比从方辉橄榄岩钙钛矿（Mg/Si $\sim$ 1.5至0.8）的影响进行了检查。我们发现，引入的自旋交叉的异常增加等熵梯度，从而地热成比例的铁方镁石的量。在深下地幔条件下，该地热可高达$\sim$ 200 K，高于传统的绝热地热。聚合体弹性模量和地震速度也对自旋交叉和地热敏感，这影响下地幔速度和成分的分析。
英文摘要：
The iron spin crossover in ferropericlase introduces anomalies in its thermodynamics and thermoelastic properties. Here we investigate how these anomalies can affect the lower mantle geotherm. The effect is examined in mantle aggregates consisting of mixtures of bridgmanite, ferropericlase, and CaSiO$_3$ perovskite, with different Mg/Si ratios varying from harzburgitic to perovskitic (Mg/Si$\sim$1.5 to 0.8). We find that the anomalies introduced by the spin crossover increase the isentropic gradient and thus the geotherm proportionally to the amount of ferropericlase. The geotherms can be as much as $\sim$ 200K hotter than the conventional adiabatic geotherm at deep lower mantle conditions. Aggregate elastic moduli and seismic velocities are also sensitive to the spin crossover and the geotherm, which impacts analyses of lower mantle velocities and composition.
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