Atomistic insight into lithospheric conductivity revealed by phonon–electron excitations in hydrous iron-bearing silicates
Atomistic insight into lithospheric conductivity revealed by phonon–electron excitations in hydrous iron-bearing silicates
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DOI：
10.1038/s43246-021-00161-y
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发表时间：
2021-06
影响因子：
7.8
通讯作者：
B. Mihailova;G. Della Ventura;N. Waeselmann;Wei Xu;J. Schlüter;F. Galdenzi;A. Marcelli;G. Redhammer-G.
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文献类型：
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作者：
B. Mihailova;G. Della Ventura;N. Waeselmann;Wei Xu;J. Schlüter;F. Galdenzi;A. Marcelli;G. Redhammer-G.
角闪石是大陆地壳和俯冲带的重要组成部分，表现出异常的各向异性导电性。岩石的性质取决于其组成矿物的物理性质，而组成矿物的物理性质又取决于晶体声子和态的电子密度。在这里，为了解决特殊岩石电导率的原子尺度机制，我们应用了对声子态和电子态都敏感的原位温度相关拉曼光谱，对富铁的角闪石进行了研究。高温下观察到的各向异性共振拉曼散射，结合密度泛函理论模型，揭示了与FeO_6声子和电子跃迁有关的与方向相关的可移动极化子的形成。因此，水合铁链和层状硅酸盐中温度激活的电子-声子激发是各向异性岩石圈电导率的原子源。此外，即使在还原气氛中，H+的可逆离域也会在相似的温度下发生。这两种类型的电荷载流子的出现都不需要铁的初始混合价状态或系统中的高氧逸度。
Amphiboles are essential components of the continental crust and subduction zones showing anomalous anisotropic conductivity. Rock properties depend on the physical properties of their constituent minerals, which in turn depend on the crystal phonon and electron density of states. Here, to address the atomic-scale mechanism of the peculiar rock conductivity, we applied in situ temperature-dependent Raman spectroscopy, sensitive to both phonon and electron states, to Fe2+-rich amphiboles. The observed anisotropic resonance Raman scattering at elevated temperatures, in combination with density-functional-theory modelling, reveals a direction-dependent formation of mobile polarons associated with coupled FeO6phonons and electron transitions. Hence, temperature-activated electron-phonon excitations in hydrous iron-bearing chain and layered silicates are the atomistic source of anisotropic lithospheric conductivity. Furthermore, reversible delocalization of H+occurs at similar temperatures even in a reducing atmosphere. The occurrence of either type of charge carriers does not require initial mixed-valence state of iron or high oxygen fugacity in the system.