Effect of Low-Spin Fe^(2+) on the Composition of the Lower Mantle
Effect of Low-Spin Fe^(2+) on the Composition of the Lower Mantle
复制标题
低自旋Fe^(2)对下地幔成分的影响
DOI：
10.1029/jb078i029p07005
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发表时间：
1973
影响因子：
3.7
通讯作者：
D. L. Anderson
中科院分区：
文献类型：
--
作者：
E. Gaffney;D. L. Anderson
详细研究了低自旋Fe^(2+)在地球下地幔中的作用。低自旋Fe^(2+)的存在允许形成额外的相，因为Mg^(2+)和低自旋Fe^(2+)可能不形成固溶体。从体模系统学预测了含低自旋铁的相的弹性行为，并与现有的冲击波数据进行了比较。几种亚铁化合物的高压相可能涉及低自旋的Fe^(2+)。铁将在1700公里以下的地幔中自旋配对，可能在更高的水平上也是如此。观测到的下地幔密度和体积模量值与热解石体相组成中的任何相组合都不一致，但可以很好地用所有Fe^(2+)自旋配对在650公里以下的模型来拟合。下地幔比上地幔富FeO和SiO_2。Fe^(2+)的自旋配对为铁和硅在下地幔中的部分熔融富集提供了极好的机制。因此，铁中的自旋配对支持了先前关于地幔化学不均匀性的论点，也提供了一种产生不均匀性的机制。这消除了还原地幔中FeO和SiO_2而为地核提供Fe和Si的动力。
The effects of low-spin Fe^(2+) in the earth's lower mantle are investigated in considerable detail. The existence of low-spin Fe^(2+) permits the formation of an extra phase, since Mg^(2+) and low-spin Fe^(2+) probably do not form solid solutions. The elastic behavior of phases containing low-spin iron is predicted from bulk modulus systematics and is compared with available shock wave data. It is likely that the high pressure phases of several ferrous iron compounds involve low-spin Fe^(2+). Iron will be spin-paired in the mantle below 1700 km and perhaps at higher levels as well. The observed density and bulk modulus in the lower mantle are inconsistent with any combination of phases in a pyrolite bulk composition but can be fit quite well by a model with all Fe^(2+) spin-paired below 650 km. The lower mantle is richer in FeO and SiO_2 than the upper mantle. The spin-pairing of Fe^(2+) provides an excellent mechanism for both iron and silicon enrichment in the lower mantle by partial melting. Thus spin-pairing in iron provides support for previous arguments for chemical inhomogeneity of the mantle and also provides a mechanism for generating the inhomogeneity. This removes the motivation for reducing FeO and SiO_2 in the mantle to supply Fe and Si for the core.